- Surgery, Pediatric
- Pediatric Surgery
Board Certification: Pediatric Surgery, American Board of Surgery (2002)
Fellowship:The Children's Hospital of Philadelphia (1997) PA
Fellowship:Yale - New Haven Hospital (2001) CT
Residency:University of Pennsylvania (1999) PA
Internship:Hospital of the University of Pennsylvania (1993) PA
Medical Education:Jefferson Medical College (1992) PA
Current Research and Scholarly Interests
Dr. Sylvester concurrently pursues three areas of related investigation. The general approach of his efforts are to combine the study of human disease samples and mouse models of human disease to pose new hypotheses and to test these hypotheses experimentally. The objective of Dr. Sylvester's studies is to derive a deeper understanding of human disease and to develop applications for possible new diagnostics and therapeutics.
In the laboratory the group studies the role of Wnt signaling in liver regeneration and response to injury. The Sylvester laboratory has demonstrated that Wnt and its signaling molecule beta-catenin have a strong influence over hepatocellular metabolism and resistance to oxidative stress. Ongoing studies to gain a deeper understanding of the mechanism by which Wnt and related pathways exert control over cellular metabolism, energy balance and redox balance are ongoing. Cellular energy and redox balance are central to the related processes of liver development, regeneration and tumorignesis.
Dr. Sylvester has established a network of academic children's hospitals and investigators to study the human newborn diseases Necrotizing Enterocolitis and sepsis. The group has published several papers describing their novel findings of molecular indicators or biomarkers of disease. The group is seeking to establish both molecular indicators of disease as well as biochemical indicators that accurately identify infants most at risk for disease in order to provide clinical strategies to prevent disease onset. Molecules and pathways of interest that have been identified in human specimens are studied further in experimental models of disease to gain a deeper insight to the specific mechanisms of disease.
Laparotomy vs. Drainage for Infants With Necrotizing Enterocolitis
This trial will compare the effectiveness of two surgical procedures -laparotomy versus drainage - commonly used to treat necrotizing enterocolitis (NEC) or isolated intestinal perforations (IP) in extremely low birth weight infants (≤1,000 g). Infants diagnosed with NEC or IP requiring surgical intervention, will be recruited. Subjects will be randomized to receive either a laparotomy or peritoneal drainage. Primary outcome is impairment-free survival at 18-22 months corrected age.
- Independent Studies (5)
Wnt/ß-Catenin Signaling Protects Mouse Liver against Oxidative Stress-induced Apoptosis through the Inhibition of Forkhead Transcription Factor FoxO3.
journal of biological chemistry
2013; 288 (24): 17214-17224
Numerous liver diseases are associated with extensive oxidative tissue damage. It is well established that Wnt/?-catenin signaling directs multiple hepatocellular processes including development, proliferation, regeneration, nutrient homeostasis and carcinogenesis. It remains un-explored whether Wnt/?-catenin signaling provides hepatocyte protection against hepatotoxin-induced apoptosis. Conditional, liver-specific ?-catenin knockdown (KD) mice and their wild-type littermates were challenged by feeding the hepatotoxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet to induce chronic oxidative liver injury. Following DDC diet, mice with ?-catenin-deficient hepatocytes demonstrate increased liver injury, indicating an important role of ?-catenin signaling for liver protection against oxidative stress. This finding was further confirmed in AML12 hepatocytes with ?-catenin signaling manipulation in vitro using paraquat, a known oxidative stress inducer. Immunofluorescence staining revealed an intense nuclear FoxO3 staining in ?-catenin-deficient livers, suggesting active FoxO3 signaling in response to DDC-induced liver injury when compared to wild-type controls. Consistently, FoxO3 target genes p27 and Bim were significantly induced in ?-Catenin KD livers. Conversely, SGK1, a ?-catenin target gene, was significantly impaired in ?-catenin KD hepatocytes that failed to inactivate FoxO3. Furthermore, shRNA mediated deletion of FoxO3 increased hepatocyte resistance to oxidative stress-induced apoptosis, confirming a pro-apoptotic role of FoxO3 in the stressed liver. Our findings suggest that Wnt/?-catenin signaling is required for hepatocyte protection against oxidative stress-induced apoptosis. The inhibition of FoxO through its phosphorylation by ?-catenin induced SGK1 expression reduces FoxO3`s apoptotic function, resulting in increased hepatocyte survival. These findings have relevance for future therapies directed at hepatocyte protection, regeneration and anti-cancer treatment.
View details for DOI 10.1074/jbc.M112.445965
View details for PubMedID 23620592
Heme oxygenase-1 deficiency promotes the development of necrotizing enterocolitis-like intestinal injury in a newborn mouse model.
American journal of physiology. Gastrointestinal and liver physiology
2013; 304 (11): G991-G1001
Necrotizing enterocolitis (NEC) is typified by mucosal destruction, which subsequently can lead to intestinal necrosis. Prematurity, enteral feeding, and bacterial colonization are the main risk factors and, combined with other stressors, can cause increased intestinal permeability, injury, and an exaggerated inflammatory response. Heme oxygenase-1 (HO-1) mediates intestinal protection due to anti-inflammatory, antioxidative, and antiapoptotic effects of its products carbon monoxide, biliverdin, and bilirubin. This study investigates a possible role of HO-1 in the pathogenesis of NEC using a newborn mouse model. We induced NEC-like intestinal injury in 7-day-old HO-1 heterozygous (HO-1 Het, Hmox1(+/-)) and wild-type (Wt, Hmox1(+/+)) mice by gavage feeding and hypoxic exposures. Control (Con) pups of both genotypes were dam-fed. Intestines of HO-1 Het Con pups appeared predisposed to injury, with higher histological damage scores, more TUNEL-positive cells, and a significant reduction in muscularis externa thickness compared with Wt Con pups. The increase in HO activity after HO-1 induction by the substrate heme or by hypoxic stress was significantly impaired in HO-1 Het pups. After induction of intestinal injury, HO-1 Het pups displayed significantly higher NEC incidence (78 vs. 43%), mortality (83 vs. 54%), and median scores (2.5 vs. 1.5) than Wt NEC pups. PCR array analyses revealed increased expressions of IL-1?, P-selectin, matrix metallopeptidase 2, collagen type XVIII-?1, serpine 1, and others in NEC-induced HO-1 Het ileal and jejunal tissues. We conclude that a partial HO-1 deficiency promotes experimental NEC-like intestinal injury, possibly mediated by exaggerated inflammation and disruption in tissue repair.
View details for DOI 10.1152/ajpgi.00363.2012
View details for PubMedID 23578787
The surgical management of necrotizing enterocolitis.
Clinics in perinatology
2013; 40 (1): 135-148
Necrotizing enterocolitis (NEC), a common cause of neonatal morbidity and mortality, is strongly associated with prematurity and typically occurs following initiation of enteral feeds. Mild NEC is adequately treated by cessation of enteral feeding, empiric antibiotics, and supportive care. Approximately 50% of affected infants will develop progressive intestinal necrosis requiring urgent operation. Several surgical techniques have been described, but there is no clear survival benefit for any single operative approach. While debate continues regarding the optimal surgical management for infants with severe NEC, future progress will likely depend on the development of improved diagnostic tools and preventive therapies.
View details for DOI 10.1016/j.clp.2012.12.011
View details for PubMedID 23415269
SIRT1 and c-Myc Promote Liver Tumor Cell Survival and Predict Poor Survival of Human Hepatocellular Carcinomas
2012; 7 (9)
The increased expression of SIRT1 has recently been identified in numerous human tumors and a possible correlation with c-Myc oncogene has been proposed. However, it remains unclear whether SIRT1 functions as an oncogene or tumor suppressor. We sought to elucidate the role of SIRT1 in liver cancer under the influence of c-Myc and to determine the prognostic significance of SIRT1 and c-Myc expression in human hepatocellular carcinoma. The effect of either over-expression or knock down of SIRT1 on cell proliferation and survival was evaluated in both mouse and human liver cancer cells. Nicotinamide, an inhibitor of SIRT1, was also evaluated for its effects on liver tumorigenesis. The prognostic significance of the immunohistochemical detection of SIRT1 and c-Myc was evaluated in 154 hepatocellular carcinoma patients. SIRT1 and c-Myc regulate each other via a positive feedback loop and act synergistically to promote hepatocellular proliferation in both mice and human liver tumor cells. Tumor growth was significantly inhibited by nicotinamide in vivo and in vitro. In human hepatocellular carcinoma, SIRT1 expression positively correlated with c-Myc, Ki67 and p53 expression, as well as high á-fetoprotein level. Moreover, the expression of SIRT1, c-Myc and p53 were independent prognostic indicators of hepatocellular carcinoma. In conclusion, this study demonstrates that SIRT1 expression supports liver tumorigenesis and is closely correlated with oncogenic c-MYC expression. In addition, both SIRT1 and c-Myc may be useful prognostic indicators of hepatocellular carcinoma and SIRT1 targeted therapy may be beneficial in the treatment of hepatocellular carcinoma.
View details for DOI 10.1371/journal.pone.0045119
View details for Web of Science ID 000308860100058
View details for PubMedID 23024800
beta-Catenin Regulates Hepatic Mitochondrial Function and Energy Balance in Mice
2012; 143 (3): 754-764
Wnt signaling regulates hepatic function and nutrient homeostasis. However, little is known about the roles of ?-catenin in cellular respiration or mitochondria of hepatocytes.We investigated ?-catenin's role in the metabolic function of hepatocytes under homeostatic conditions and in response to metabolic stress using mice with hepatocyte-specific deletion of ?-catenin and their wild-type littermates, given either saline (sham) or ethanol (as a model of binge drinking and acute ethanol intoxication).Under homeostatic conditions, ?-catenin-deficient hepatocytes demonstrated mitochondrial dysfunctions that included impairments to the tricarboxylic acid cycle and oxidative phosphorylation (OXPHOS) and decreased production of adenosine triphosphate (ATP). There was no evidence for redox imbalance or oxidative cellular injury in the absence of metabolic stress. In mice with ?-catenin-deficient hepatocytes, ethanol intoxication led to significant redox imbalance in the hepatocytes and further deterioration in mitochondrial function that included reduced OXPHOS, fatty acid oxidation (FAO), and ATP production. Ethanol feeding significantly increased liver steatosis and oxidative damage, compared with wild-type mice, and disrupted the ratio of nicotinamide adenine dinucleotide. ?-catenin-deficient hepatocytes also had showed disrupted signaling of Sirt1/peroxisome proliferator-activated receptor-? signaling.?-catenin has an important role in the maintenance of mitochondrial homeostasis, regulating ATP production via the tricarboxylic acid cycle, OXPHOS, and fatty acid oxidation; ?-catenin function in these systems is compromised under conditions of nutrient oxidative stress. Reagents that alter Wnt-?-catenin signaling might be developed as a useful new therapeutic strategy for treatment of liver disease.
View details for DOI 10.1053/j.gastro.2012.05.048
View details for Web of Science ID 000308399300039
View details for PubMedID 22684045
Notch signaling inhibits hepatocellular carcinoma following inactivation of the RB pathway
JOURNAL OF EXPERIMENTAL MEDICINE
2011; 208 (10): 1963-1976
Hepatocellular carcinoma (HCC) is the third cancer killer worldwide with >600,000 deaths every year. Although the major risk factors are known, therapeutic options in patients remain limited in part because of our incomplete understanding of the cellular and molecular mechanisms influencing HCC development. Evidence indicates that the retinoblastoma (RB) pathway is functionally inactivated in most cases of HCC by genetic, epigenetic, and/or viral mechanisms. To investigate the functional relevance of this observation, we inactivated the RB pathway in the liver of adult mice by deleting the three members of the Rb (Rb1) gene family: Rb, p107, and p130. Rb family triple knockout mice develop liver tumors with histopathological features and gene expression profiles similar to human HCC. In this mouse model, cancer initiation is associated with the specific expansion of populations of liver stem/progenitor cells, indicating that the RB pathway may prevent HCC development by maintaining the quiescence of adult liver progenitor cells. In addition, we show that during tumor progression, activation of the Notch pathway via E2F transcription factors serves as a negative feedback mechanism to slow HCC growth. The level of Notch activity is also able to predict survival of HCC patients, suggesting novel means to diagnose and treat HCC.
View details for DOI 10.1084/jem.20110198
View details for Web of Science ID 000295318900005
View details for PubMedID 21875955
Intestinal involvement during 3,5-diethoxycarbonyl-1,4-dihydrocollidine-induced chronic liver injury in a mouse model
JOURNAL OF PEDIATRIC SURGERY
2011; 46 (8): 1495-1502
Although a physiologic relationship between intestinal mucosal integrity and hepatic function has been previously described, the effect of primary liver disease on intestinal mucosal homeostasis has not been previously well documented. In the current study, we studied the effects of chronic liver injury as a primary injury on enterocyte turnover (proliferation and apoptosis) in a mouse model.The liver toxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-enriched diet was used to induce chronic cholestatic liver injury in mice. Livers and intestine were harvested after 3 weeks of dietary treatment of histologic analysis and a determination of cell proliferation (immunohistochemistry for Ki67), or apoptosis (immunohistochemistry for caspase-3), as well as a determination of Wnt/β-catenin signaling activity.All DDC-fed animals exhibited histologic evidence of liver damage that was associated with the expansion of atypical ductal proliferation near the periportal areas and increased oxidative stress. In the intestine, DDC-induced liver damage was associated with decreased villus height, decreased enterocyte proliferation, and increased cell apoptosis compared with control animals. There was also evidence for decreased β-catenin expression by immunostaining in crypt and villus cells of DDC-fed mice compared with control animals.Primary liver injury and cholestasis is associated with intestinal mucosal hypoplasia. Decreased cell proliferation and increased cell apoptosis may be responsible for decreased intestinal epithelial cell mass. The observed decrease in cell turnover is accompanied by an alteration in Wnt/β-catenin signaling.
View details for DOI 10.1016/j.jpedsurg.2011.04.007
View details for Web of Science ID 000293950100014
View details for PubMedID 21843714
Wnt-beta-catenin Signaling Protects Against Hepatic Ischemia and Reperfusion Injury in Mice
2011; 141 (2): 707-U417
Ischemia and reperfusion injury are common causes of oxidative tissue damage associated with many liver diseases and hepatic surgery. The Wnt-?-catenin signaling pathway is an important regulator of hepatic development, regeneration, and carcinogenesis. However, the role of Wnt signaling in the hepatocellular response to ischemia-reperfusion (I/R) injury has not been determined.Hepatic injury following ischemia or I/R was investigated in hepatocyte-specific, ?-catenin-deficient mice, as well as Wnt1-overexpressing and wild-type (control) mice.Wnt-?-catenin signaling was affected by the cellular redox balance in hepatocytes. Following ischemia or I/R, mice with ?-catenin-deficient hepatocytes were significantly more susceptible to liver injury. Conversely, mice that overexpressed Wnt1 in hepatocytes were resistant to hepatic I/R injury. Hypoxia inducible factor (HIF)-1? signaling was reduced in ?-catenin-deficient liver but increased in hepatocytes that overexpressed Wnt1 under hypoxia and following I/R, indicating an interaction between ?-catenin and HIF-1? signaling in the liver. The mechanism by which Wnt signaling protects against liver injury involves the role of ?-catenin as a transcriptional coactivator of HIF-1? signaling, which promotes hepatocyte survival under hypoxic conditions.Cellular redox balance affects Wnt-?-catenin signaling, which protects against hypoxia and I/R injury. These findings might be used to develop strategies for protection of hepatocytes, regeneration of liver, and inhibition of carcinogenesis.
View details for DOI 10.1053/j.gastro.2011.04.051
View details for Web of Science ID 000293523300049
View details for PubMedID 21679710
Risk Factors for Parenteral Nutrition-associated Liver Disease Following Surgical Therapy for Necrotizing Enterocolitis
JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION
2011; 52 (5): 595-600
The aim of the study was to prospectively determine risk factors for the development of parenteral nutrition-associated liver disease (PNALD) in infants who underwent surgery for necrotizing enterocolitis (NEC), the most common cause of intestinal failure in children.: From February 2004 to February 2007, we diagnosed 464 infants with NEC, of whom 180 had surgery. One hundred twenty-seven patients were available for full analysis. PNALD was defined as serum direct bilirubin ? 2 mg/dL or ALT ? 2 × the upper limit of normal in the absence of sepsis after ? 14 days of exposure to PN.Median gestational age was 26 weeks and 68% were boys. Seventy percent of the cohort developed PNALD and the incidence of PNALD varied significantly across the 6 study sites, ranging from 56% to 85% (P = 0.05). Multivariable logistic regression analysis identified small-bowel resection or creation of jejunostomy (odds ratio [OR] 4.96, 95% confidence interval [CI] 1.97-12.51, P = 0.0007) and duration of PN in weeks (OR 2.37, 95% CI 1.56-3.60, P < 0.0001) as independent risk factors for PNALD. Preoperative exposure to PN was also associated with the development of PNALD; the risk of PNALD was 2.6 (95% CI 1.5-4.7; P = 0.001) times greater in patients with ? 4 weeks of preoperative PN compared with those with less preoperative PN use. Breast milk feedings, episodes of infection, and gestational age were not related to the development of PNALD.The incidence of PNALD is high in infants with NEC undergoing surgical treatment. Risk factors for PNALD are related to signs of NEC severity, including the need for small-bowel resection or proximal jejunostomy, as well as longer exposure to PN. Identification of these and other risk factors can help in the design of clinical trials for the prevention and treatment of PNALD and for clinical assessment of patients with NEC and prolonged PN dependence.
View details for DOI 10.1097/MPG.0b013e31820e8396
View details for Web of Science ID 000289671900018
View details for PubMedID 21464752
Risk Factors for Intestinal Failure in Infants with Necrotizing Enterocolitis: A Glaser Pediatric Research Network Study
JOURNAL OF PEDIATRICS
2010; 157 (2): 203-U50
To determine risk factors for intestinal failure (IF) in infants undergoing surgery for necrotizing enterocolitis (NEC).Infants were enrolled in a multicenter prospective cohort study. IF was defined as the requirement for parenteral nutrition for >or= 90 days. Logistic regression was used to identify predictors of IF.Among 473 patients enrolled, 129 had surgery and had adequate follow-up data, and of these patients, 54 (42%) developed IF. Of the 265 patients who did not require surgery, 6 (2%) developed IF (OR 31.1, 95% CI, 12.9 - 75.1, P < .001). Multivariate analysis identified the following risk factors for IF: use of parenteral antibiotics on the day of NEC diagnosis (OR = 16.61, P = .022); birth weight < 750 grams, (OR = 9.09, P < .001); requirement for mechanical ventilation on the day of NEC diagnosis (OR = 6.16, P = .009); exposure to enteral feeding before NEC diagnosis (OR=4.05, P = .048); and percentage of small bowel resected (OR = 1.85 per 10 percentage point greater resection, P = .031).The incidence of IF among infants undergoing surgical treatment for NEC is high. Variables characteristic of severe NEC (low birth weight, antibiotic use, ventilator use, and greater extent of bowel resection) were associated with the development of IF.
View details for DOI 10.1016/j.jpeds.2010.02.023
View details for Web of Science ID 000279871700011
View details for PubMedID 20447649
URINE PEPTIDOMICS FOR CLINICAL BIOMARKER DISCOVERY
ADVANCES IN CLINICAL CHEMISTRY, VOL 51
2010; 51: 181-213
Urine-based proteomic profiling is a novel approach that may result in the discovery of noninvasive biomarkers for diagnosing patients with different diseases, with the aim to ultimately improve clinical outcomes. Given new and emerging analytical technologies and data mining algorithms, the urine peptidome has become a rich resource to uncover naturally occurring peptide biomarkers for both systemic and renal diseases. However, significant analytical hurdles remain in sample collection and storage, experimental design, data analysis, and statistical inference. This study summarizes, focusing on our experiences and perspectives, the progress in addressing these challenges to enable high-throughput urine peptidomics-based biomarker discovery.
View details for DOI 10.1016/S0065-2423(10)51007-2
View details for Web of Science ID 000281865700007
View details for PubMedID 20857622
Clinical parameters do not adequately predict outcome in necrotizing enterocolitis: a multi-institutional study
JOURNAL OF PERINATOLOGY
2008; 28 (10): 665-674
Necrotizing enterocolitis (NEC) remains a major cause of neonatal morbidity and mortality. Some infants recover uneventfully with medical therapy whereas others develop severe disease (that is, NEC requiring surgery or resulting in death). Repeated attempts to identify clinical parameters that would reliably identify infants with NEC most likely to progress to severe disease have been unsuccessful. We hypothesized that comprehensive prospective data collection at multiple centers would allow us to develop a model which would identify those babies at risk for progressive NEC.This prospective, observational study was conducted at six university children's hospitals. Study subjects were neonates with suspected or confirmed NEC. Comprehensive maternal and newborn histories were collected at the time of enrollment, and newborn clinical data were collected prospectively, thereafter. Multivariate logistic regression analysis was used to develop a predictive model of risk factors for progression.Of 455 neonates analyzed, 192 (42%) progressed to severe disease, and 263 (58%) advanced to full feedings without operation. The vast majority of the variables studied proved not to be associated with progression to severe disease. A total of 12 independent predictors for progression were identified, including only 3 not previously described: having a teenaged mother (odds ratio, OR, 3.14; 95% confidence interval, CI, 1.45 to 6.96), receiving cardiac compressions and/or resuscitative drugs at birth (OR, 2.51; 95% CI, 1.17 to 5.48), and having never received enteral feeding before diagnosis (OR, 2.41; 95% CI, 1.08 to 5.52).Our hypothesis proved false. Rigorous prospective data collection of a sufficient number of patients did not allow us to create a model sufficiently predictive of progressive NEC to be clinically useful. It appears increasingly likely that further analysis of clinical parameters alone will not lead to a significant improvement in our understanding of NEC. We believe that future studies must focus on advanced biologic parameters in conjunction with clinical findings.
View details for DOI 10.1038/jp.2008.119
View details for Web of Science ID 000259675900003
View details for PubMedID 18784730
Hepatotoxin-Induced Changes in the Adult Murine Liver Promote MYC-Induced Tumorigenesis
2008; 3 (6)
Overexpression of the human c-MYC (MYC) oncogene is one of the most frequently implicated events in the pathogenesis of hepatocellular carcinoma (HCC). Previously, we have shown in a conditional transgenic mouse model that MYC overexpression is restrained from inducing mitotic cellular division and tumorigenesis in the adult liver; whereas, in marked contrast, MYC induces robust proliferation associated with the very rapid onset of tumorigenesis in embryonic and neonatal mice.Here, we show that non-genotoxic hepatotoxins induce changes in the liver cellular context associated with increased cellular proliferation and enhanced tumorigenesis. Both 5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) and carbon tetrachloride (CCl(4)) cooperate with MYC to greatly accelerate the onset of liver cancer in an adult host to less than 7 days versus a mean latency of onset of over 35 weeks for MYC alone. These hepatotoxin-enhanced liver tumors grossly and histologically resemble embryonic and neonatal liver tumors. Importantly, we found that MYC overexpression is only capable of inducing expression of the mitotic Cyclin B1 in embryonic/neonatal hosts or adult hosts that were treated with either carcinogen.Our results suggest a model whereby oncogenes can remain latently activated, but exposure of the adult liver to hepatotoxins that promote hepatocyte proliferation can rapidly uncover their malignant potential.
View details for DOI 10.1371/journal.pone.0002493
View details for Web of Science ID 000263280700056
View details for PubMedID 18560566
Doxycycline sclerotherapy as primary treatment of head and neck lymphatic malformations in children
JOURNAL OF PEDIATRIC SURGERY
2008; 43 (3): 451-460
The authors report their experience with doxycycline sclerotherapy as primary treatment of head and neck lymphatic malformations (LMs) in children.A retrospective chart review was used to collect data on 11 patients treated with doxycycline sclerotherapy for LMs of the head and neck at our institution since 2003. Radiographic imaging allowed classification of patient LM as macrocystic, microcystic, or mixed according to previously published guidelines. Only patients with macrocystic or mixed lesions were offered doxycycline sclerotherapy. Radiographic imaging and physical examination were used to determine efficacy of treatment. After each treatment, the clinical and radiographic response was characterized as excellent (> or = 95% decrease in lesion size), satisfactory (> or = 50% decrease in volume and asymptomatic), or poor (< 50% decrease in volume or symptomatic).Eleven patients underwent a total of 23 sclerotherapies with an average of 2 treatments per patient (range, 1-4). All 7 patients with macrocystic lesions achieved complete clinical resolution with an average radiographic resolution of 93%. The 4 patients with mixed lesions achieved only partial clinical resolution and an average of 73% radiographic resolution. No patient experienced any adverse effects related to the treatment. At a median follow-up of 8 months, 2 patients (18%) experienced lesion recurrence in the setting of concomitant infection.Doxycycline sclerotherapy is safe and effective as a primary treatment modality for macrocystic and mixed LMs of the head and neck in the pediatric population.
View details for DOI 10.1016/j.jpedsurg.2007.10.009
View details for Web of Science ID 000254803500008
View details for PubMedID 18358281
Hepatic parenchymal replacement in mice by transplanted allogeneic hepatocytes is facilitated by bone marrow transplantation and mediated by CD4 cells
2008; 47 (2): 706-718
The lack of adequate donor organs is a major limitation to the successful widespread use of liver transplantation for numerous human hepatic diseases. A desirable alternative therapeutic option is hepatocyte transplantation (HT), but this approach is similarly restricted by a shortage of donor cells and by immunological barriers. Therefore, in vivo expansion of tolerized transplanted cells is emerging as a novel and clinically relevant potential alternative cellular therapy. Toward this aim, in the present study we established a new mouse model that combines HT with prior bone marrow transplantation (BMT). Donor hepatocytes were derived from human alpha(1)-antitrypsin (hAAT) transgenic mice of the FVB strain. Serial serum enzyme-linked immunosorbent assays for hAAT protein were used to monitor hepatocyte engraftment and expansion. In control recipient mice lacking BMT, we observed long-term yet modest hepatocyte engraftment. In contrast, animals undergoing additional syngeneic BMT prior to HT showed a 3- to 5-fold increase in serum hAAT levels after 24 weeks. Moreover, complete liver repopulation was observed in hepatocyte-transplanted Balb/C mice that had been transplanted with allogeneic FVB-derived bone marrow. These findings were validated by a comparison of hAAT levels between donor and recipient mice and by hAAT-specific immunostaining. Taken together, these findings suggest a synergistic effect of BMT on transplanted hepatocytes for expansion and tolerance induction. Livers of repopulated animals displayed substantial mononuclear infiltrates, consisting predominantly of CD4(+) cells. Blocking the latter prior to HT abrogated proliferation of transplanted hepatocytes, and this implied an essential role played by CD4(+) cells for in vivo hepatocyte selection following allogeneic BMT.The present mouse model provides a versatile platform for investigation of the mechanisms governing HT with direct relevance to the development of clinical strategies for the treatment of human hepatic failure.
View details for DOI 10.1002/hep.22012
View details for Web of Science ID 000252939500040
View details for PubMedID 18220289
Wnt/beta-catenin signaling in murine hepatic transit amplifying progenitor cells
2007; 133 (5): 1579-1591
Oval cells are postnatal hepatic progenitors with high proliferative potential and bipotent differentiation ability to become hepatocytes and cholangiocytes. Because Wnt/beta-catenin signaling is a known regulatory pathway for liver development and regeneration, we studied the role of Wnt signaling in oval cells using a mouse model of chronic liver injury.A 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-enriched diet was used to stimulate oval cell proliferation. Livers were harvested for histologic analysis and determination of Wnt family gene expression by quantitative reverse transcription-polymerase chain reaction and in situ hybridization. The transgenic beta-catenin reporter mouse (TOPGAL) was use to confirm canonical Wnt/beta-catenin signal transduction in proliferating oval cells within atypical ductal proliferations (ADPs). Confocal fluorescence microscopy and immunohistochemistry was used to confirm colocalization of beta-catenin with the oval cell antigen A-6.Several Wnt ligands were significantly induced in the liver of DDC-fed mice and localized to proliferating cells in and adjacent to the ADPs. Oval cells isolated from DDC-fed mouse livers showed the presence of active beta-catenin in the nucleus along with cell-cycle entry in response to purified Wnt3a in vitro. Moreover, Wnt3a-induced beta-catenin/T-cell factor/lymphoid enhancer factor (TCF/LEF) transcriptional activation was quantified by TCF/LEF luciferase reporter assays.From these data, we conclude that oval cells respond to Wnt ligands (Wnt3a) in vitro with an increase in amino-terminus dephosphorylated beta-catenin and cell-cycle entry and that canonical Wnt/beta-catenin/TCF signaling is active in proliferating facultative hepatic progenitor cells in vivo. These findings may lend insight to the consequences of increased canonical Wnt signaling during periods of chronic liver injury.
View details for DOI 10.1053/j.gastro.2007.08.036
View details for Web of Science ID 000250820100025
View details for PubMedID 17983805
Risk factors for the development of abdominal abscess following operation for perforated appendicitis in children - A multicenter case-control study
ARCHIVES OF SURGERY
2007; 142 (3): 236-241
The morbidity following treatment for perforated appendicitis in children is significant, with intra-abdominal abscess being one of the more serious complications. This can lead to prolonged hospitalizations and antibiotic administration, multiple computed tomographic scans, and invasive procedures. The purpose of our study was to determine risk factors for developing an intra-abdominal abscess following treatment for perforated appendicitis.Case-control study.Four tertiary care children's hospitals.Children aged 1 to 18 years with appendicitis.Multivariable logistic regression.Development of postoperative abscess, length of hospital stay, presence or absence of fever, and tolerance of diet on postoperative day 3.Thirty-five (13.2%) of 265 children developed an abscess. Ten factors with a bivariate P value <.20 were included in the regression model. The final multivariable model revealed only 2 factors influencing abscess development: an intraoperative fecalith (odds ratio, 8.77 [95% confidence interval, 1.50-51.40]) and diarrhea at presentation. Many factors proposed to be associated with abscess were not, including pain history, type and timing of preoperative antibiotics, abscess at operation, laparoscopic procedure, and length of antibiotics postoperatively. Thiry-seven children were discharged on or before postoperative day 3. Another 21 children were afebrile and tolerating a diet at that time but remained in the hospital. There were no significant differences between the 2 groups. None of the early-discharge group developed an abscess, and 2 of those remaining in the hospital developed an abscess (P = .06).Clinical factors commonly thought to be predictive of abscess formation following perforated appendicitis were not reliable predictors of this outcome. Our results suggest that if children are afebrile and eating on postoperative day 3 they can be discharged with a low rate of abscess development.
View details for Web of Science ID 000244717700006
View details for PubMedID 17372047
Matched analysis of nonoperative management vs immediate appendectomy for perforated appendicitis
JOURNAL OF PEDIATRIC SURGERY
2007; 42 (1): 19-24
The role of nonoperative therapy vs immediate appendectomy in the management of children with perforated appendicitis remains undefined. The objective of this study was to rigorously compare these management options in groups of patients with matched clinical characteristics.Multicenter case-control study was conducted from 1998 to 2003. We compared patients treated nonoperatively vs those undergoing appendectomy to identify differences in 12 clinical parameters. We then generated a second control group of patients matched for these variables and compared the following outcomes in these clinically similar groups: complication rate, abscess rate, and length of stay (LOS). Analysis was performed according to intention-to-treat principles, using chi2, Fisher exact, and Student t tests.The only significant difference between patients treated nonoperatively and those treated by appendectomy was the duration of pain on presentation (6.8 vs 3.1 days of pain). We created a second control group of patients undergoing immediate appendectomy matched on duration of pain on presentation to patients treated nonoperatively. These groups continued to be clinically comparable for the other 11 parameters. Compared to this matched control group, the nonoperative group had fewer complications (19% vs 43%, P < .01), fewer abscesses (4% vs 24%, P < .01), and a trend for shorter LOS (6.5 +/- 5.7 vs 8.8 +/- 6.7 days, P = .08).When nonoperative management for perforated appendicitis was studied using appropriately matched clinical controls, we found that it resulted in a lower complication rate and shorter LOS in the subset of patients presenting with a long duration of pain. Our data suggest that nonoperative management should be prospectively evaluated in children with perforated appendicitis presenting with a history of pain exceeding 5 days.
View details for DOI 10.1016/j.jpedsurg.2006.09.005
View details for Web of Science ID 000243707100003
View details for PubMedID 17208535
Stem cells: tissue regeneration and cancer.
Seminars in pediatric surgery
2006; 15 (4): 284-292
Regenerative medicine is the promised paradigm of replacement and repair of damaged or senescent tissues. As the building blocks for organ development and tissue repair, stem cells have unique and wide-ranging capabilities, thus delineating their potential application to regenerative medicine. The recognition that consistent patterns of molecular mechanisms drive organ development and postnatal tissue regeneration has significant implications for a variety of pediatric diseases beyond replacement biology. The observation that organ-specific stem cells derive all of the differentiated cells within a given tissue has led to the acceptance of a stem cell hierarchy model for tissue development, maintenance, and repair. Extending the tissue stem cell hierarchical model to tissue carcinogenesis may revolutionize the manner in which we conceptualize cancer therapeutics. In this review, the clinical promise of these technologies and the emerging concept of "cancer stem cells" are examined. A basic understanding of stem cell biology is paramount to stay informed of this emerging technology and the accompanying research in this area with the potential for clinical application.
View details for PubMedID 17055959
Laparotomy versus peritoneal drainage for necrotizing enterocolitis and perforation
NEW ENGLAND JOURNAL OF MEDICINE
2006; 354 (21): 2225-2234
Perforated necrotizing enterocolitis is a major cause of morbidity and mortality in premature infants, and the optimal treatment is uncertain. We designed this multicenter randomized trial to compare outcomes of primary peritoneal drainage with laparotomy and bowel resection in preterm infants with perforated necrotizing enterocolitis.We randomly assigned 117 preterm infants (delivered before 34 weeks of gestation) with birth weights less than 1500 g and perforated necrotizing enterocolitis at 15 pediatric centers to undergo primary peritoneal drainage or laparotomy with bowel resection. Postoperative care was standardized. The primary outcome was survival at 90 days postoperatively. Secondary outcomes included dependence on parenteral nutrition 90 days postoperatively and length of hospital stay.At 90 days postoperatively, 19 of 55 infants assigned to primary peritoneal drainage had died (34.5 percent), as compared with 22 of 62 infants assigned to laparotomy (35.5 percent, P=0.92). The percentages of infants who depended on total parenteral nutrition were 17 of 36 (47.2 percent) in the peritoneal-drainage group and 16 of 40 (40.0 percent) in the laparotomy group (P=0.53). The mean (+/-SD) length of hospitalization for the 76 infants who were alive 90 days after operation was similar in the primary peritoneal-drainage and laparotomy groups (126+/-58 days and 116+/-56 days, respectively; P=0.43). Subgroup analyses stratified according to the presence or absence of radiographic evidence of extensive necrotizing enterocolitis (pneumatosis intestinalis), gestational age of less than 25 weeks, and serum pH less than 7.30 at presentation showed no significant advantage of either treatment in any group.The type of operation performed for perforated necrotizing enterocolitis does not influence survival or other clinically important early outcomes in preterm infants. (ClinicalTrials.gov number, NCT00252681.).
View details for Web of Science ID 000237758900004
View details for PubMedID 16723614
Absence of the p53 tumor suppressor gene promotes osteogenesis in mesenchymal stem cells
JOURNAL OF PEDIATRIC SURGERY
2006; 41 (4): 624-632
Osteosarcoma arises predominantly in the metaphyseal growth plate of children during the growth spurt years. These tumors develop during physiological growth from an expanding cell population, suggesting that the transformed cell is a bone-forming progenitor. An absence of the p53 oncogene has been implicated in the origin and progression of osteosarcoma, and because mesenchymal stem cells (MSCs) are the physiological osteogenic progenitor cell population, we hypothesized that a p53-/- mutation would enhance bone differentiation of MSC in a mouse model of in vitro osteogenesis.Clonal MSC populations were derived from p53-/- mice. P53-/- and wild-type cells were placed in osteogenic culture and assessed via Alizarin Red quantification and alkaline phosphatase staining. The osteogenic marker genes Cbfa1, osteopontin, and osteocalcin were assessed by quantitative real time polymerase chain reaction during differentiation.Bone nodule formation and alkaline phosphatase staining was accelerated and enhanced in the p53-/- cells. The early and intermediate osteogenic markers, Cbfa1 and osteopontin, were upregulated in p53-/- MSCs compared with wild-type cells during osteogenesis. The terminal osteogenic marker gene osteocalcin was paradoxically lower in p53-/- MSCs indicating impaired terminal differentiation.The p53-/- mutation enhances and accelerates early osteogenesis in MSCs, but prevents terminal differentiation toward a mature osteocyte phenotype. These findings may have important implications for the regulation of the MSC compartment during the derivation of osteosarcoma in children.
View details for DOI 10.1016/j.jpedsurg.2005.12.001
View details for Web of Science ID 000237015800002
View details for PubMedID 16567167
Repair and regeneration: opportunities for carcinogenesis from tissue stem cells
JOURNAL OF CELLULAR AND MOLECULAR MEDICINE
2006; 10 (2): 292-308
This review will discuss the mechanisms of repair and regeneration in various tissue types and how dysregulation of these mechanisms may lead to cancer. Normal tissue homeostasis involves a careful balance between cell loss and cell renewal. Stem and progenitor cells perform these biologic processes as the functional units of regeneration during both tissue homeostasis and repair. The concept of tissue stem cells capable of giving rise to all differentiated cells within a given tissue led to the concept of a cellular hierarchy in tissues and in tumors. Thus, only a few cells may be necessary and sufficient for tissue repair or tumor regeneration. This is known as the hierarchical model of tumorigenesis. This report will compare this model with the stochastic model of tumorigenesis. Under normal circumstances, the processes of tissue regeneration or homeostasis are tightly regulated by several morphogen pathways to prevent excessive or inappropriate cell growth. This review presents the recent evidence that dysregulation of these processes may provide opportunities for carcinogenesis for the long-lived, highly proliferative tissue stem cell population. New findings of cancer initiating tissue stem cells identified in several solid and circulating cancers including breast, brain and hematopoietic tumors will also be reviewed. Finally, this report reviews the cellular biology of cancer and its relevance to the development of more effective cancer treatment protocols.
View details for Web of Science ID 000239799000005
View details for PubMedID 16796800
Donor-derived, liver-specific protein expression after bone marrow transplantation
2004; 78 (4): 530-536
Bone marrow transplantation (BMT) may represent a novel mechanism to deliver a functional gene to a deficient liver. Bone marrow-derived hepatocytes are rare and without a defined contribution to liver function. Consequently, the clinical significance of BMT to treat liver disease is unclear. We sought to quantify bone marrow-derived hepatocyte protein expression after BMT and determine whether the process is inducible with liver injury.Mice transgenic for human alpha-1 antitrypsin (hAAT) under a hepatocyte-specific promoter were used as bone marrow donors. Adenoviral transduction of modified urokinase plasminogen activator (Ad-muPA) was used to induce liver injury. Eight weeks after lethal irradiation and BMT, recipients were stratified into two groups: BMT alone (n = 5) and BMT + Ad-muPA (n= 10). Both groups of animals were bled before (t = 0) and at 2, 4, 8, and 16 weeks after Ad-muPA administration, and the serum samples were assessed for hAAT by enzyme-linked immunosorbent assay.Transgenic donor mice expressed 5 to 10 mg/mL of hAAT. Recipients of BMT alone expressed less than 80 ng/mL of hAAT over all time periods. Animals receiving BMT + Ad-muPA showed sustained and stable hAAT expression of approximately 200 ng/mL. Differences were statistically significant at each time point.Serum protein levels from liver-specific transgene expression are detectable and persist after BMT. Expression is low, but inducible with liver injury. We are currently developing strategies to augment donor-derived, liver-specific protein expression after BMT.
View details for DOI 10.1097/01.TP.0000130180.42573.BI
View details for Web of Science ID 000223486500008
View details for PubMedID 15446311
In vivo selection of primary and bone-marrow-derived hepatocytes after allogeneic transplantation in mice
ELSEVIER SCIENCE BV. 2006: S33-S33
View details for Web of Science ID 000237328100076
Hepatocyte targeting for quantifiable and functional cellular transplantation
ELSEVIER SCIENCE INC. 2003: S15-S15
View details for Web of Science ID 000185248100026