BRIGHT ASARE-BEDIAKO

All Publications

• Mouse and Rat Oxygen-Induced Retinopathy Models to Study Vascular Features Seen in Retinopathy of Prematurity. Bio-protocol Tankersley, M. P., Beri, S., Ramshekar, A., Asare-Bediako, B., Shah, N. S., Karmoker, J. R., Huang, H. C., Hartnett, E. M. 2026; 16 (15): e5771

  Abstract

  Retinopathy of prematurity (ROP), a retinovascular disease, is a leading cause of childhood blindness worldwide. Given the constraints of studying molecular mechanisms in preterm infants, reproducible animal models are important to understand ROP pathophysiology. Mouse and rat oxygen-induced retinopathy (OIR) models are the most commonly used and recapitulate key vascular features seen in ROP. However, these models are susceptible to inherent variability that limits reproducibility, including inter-litter variability, consistency of oxygen delivery across experiments, retinal dissection technique, and immunohistochemistry. Here, we describe a comprehensive protocol for performing the most common mouse and rat OIR models, and procedures such as eye enucleation, retinal dissection and flat mounting, isolectin GS-IB4 staining, whole retina stitched fluorescence imaging from Z-stacks, and quantification of vascular features. This protocol provides important materials and procedural details to increase the reproducibility of the mouse and rat OIR models. Key features • Rat and mouse oxygen-induced retinopathy (OIR) models. • Eye enucleation of experimental rat and mouse pups. • Retinal flat mounting and immunostaining for rat and mouse eyes. • Image analysis of retinal flat mounts from rat and mouse eyes.

  View details for DOI 10.21769/BioProtoc.5771

  View details for PubMedID 42591369

  View details for PubMedCentralID PMC13461755

• Automated Deep Learning Quantification of Avascular Area and Intravitreal Neovascularization in Retinal Flatmounts of Rodent Oxygen-Induced Retinopathy Models. Translational vision science & technology Shah, N. S., Ramshekar, A., Asare-Bediako, B., Tankersley, M. P., Huang, H. C., Beri, S., Kunz, E., Lee, A. Y., Hartnett, M. E. 2026; 15 (6): 41

  Abstract

  To develop a single deep learning model that quantifies the retinal avascular area (AVA) and intravitreal neovascularization (IVNV) in rodent oxygen-induced retinopathy (OIR) models.A U-Net-based model was developed to analyze AVA and IVNV in lectin-stained retinal flatmounts. The model was trained on 325 images (267 mouse and 58 rat) and evaluated on an independent test set of 37 images (18 mouse and 19 rat) annotated by human graders. We assessed intergrader reliability and agreement at metric and pixel levels. Mouse pixel-level performance was also compared with a previously published model.Intergrader reliability was high for percent AVA (mouse intraclass correlation coefficient [ICC] = 0.840; rat ICC = 0.971), moderate for rat percent IVNV (ICC = 0.509), and low for mouse percent IVNV (ICC = -0.082). Metric-level correlation was strong in rat OIR (percent AVA r = 0.979; percent IVNV r = 0.943) and for mouse percent AVA (r = 0.957), but weak for mouse percent IVNV (r = 0.265). The Dice similarity coefficient was high for total retina (TR)/AVA and moderate for IVNV (rat: TR = 0.983, AVA = 0.924, IVNV = 0.612; mouse: TR = 0.975, AVA = 0.912, IVNV = 0.601). In mouse OIR, the Dice similarity coefficient matched or exceeded the previously published model (AVA = 0.912 vs. 0.887; IVNV = 0.601 vs. 0.559). Reviewers selected the IVNV mask created by the model in 83.3% of qualitative comparisons.Our deep learning model supports automated rat OIR analysis while maintaining mouse performance and may improve reproducibility of OIR measurements.Rodent OIR models are necessary to understand retinopathy of prematurity (ROP) pathophysiology. Our deep learning model effectively quantifies features of ROP recapitulated by both mouse and rat OIR.

  View details for DOI 10.1167/tvst.15.6.41

  View details for PubMedID 42376996

• Resilient Calvarial Bone Marrow Supports Retinal Repair in Type 2 Diabetes. Advanced science (Weinheim, Baden-Wurttemberg, Germany) Asare-Bediako, B., Calzi, S. L., Behnsen, J. G., Prasad, R., Blaszkiewicz, M., Adu-Rutledge, Y., Rosencrans, R. F., Floyd, J. L., Rennhack, A., Stanford, D., Lin, A., Lydic, T. A., Sheridan, C. M., Boulton, M. E., Townsend, K. L., Busik, J. V., Grant, M. B. 2026: e19680

  Abstract

  Using micro-computed tomography, we identified a network of skull channels in the calvarium of type 2 diabetic (T2D) mice that remained structurally intact and numerically stable despite long-standing disease. The retention of calvaria bone marrow structural integrity was associated with preserved hematopoietic capacity under chronic diabetic conditions, which was not observed in the bone marrow of long bones. A distinctive feature of the calvarial bone marrow compartment was its direct exposure to cerebrospinal fluid (CSF), a property not shared by tibial bone marrow. To characterize the biochemical environment of the murine calvarium, we profiled oxysterols in CSF using mass spectrometry. The CSF exhibited elevated levels of neurotrophic and anti-inflammatory oxysterols, including 22-hydroxycholesterol (22-OHC) and 27-hydroxycholesterol (27-OHC). To assess whether this protective oxysterol signature was conserved in humans, we analyzed CSF samples from diabetic and non-diabetic individuals with obesity-associated idiopathic intracranial hypertension (IIH). Human CSF contained 7α-hydroxy-3-oxo-4-cholestenoic acid (7-HOCA), a metabolite of 27-OHC, supporting the conservation of this neuroprotective profile across species. Given the anatomical proximity of the calvarium to the eye, we hypothesized that calvaria bone marrow may serve as a reservoir for immune cells recruited to the injured or infected retina. The calvaria bone marrow was the predominant source of myeloid angiogenic cells (MACs) and neutrophils, mobilizing these cells at levels approximately 20-fold higher than long bones. These findings demonstrate that calvarial bone marrow plays a critical role in retinal immune defense, while maintaining both structural integrity and functional capacity despite chronic T2D.

  View details for DOI 10.1002/advs.202519680

  View details for PubMedID 41486419

• Endothelial MEMO1 Regulates Angiogenic Signaling in a Model of Retinopathy of Prematurity. FASEB bioAdvances Ramshekar, A., Asare-Bediako, B., Nguyen, J., Suresh, A., Simmons, A., Bretz, C. A., Wang, H., Kunz, E., Zaugg, C. J., Wallace-Carrete, C., Hartnett, M. E. 2025; 7 (9): e70051

  Abstract

  Vascular endothelial growth factor (VEGF) is important in both developmental and pathologic angiogenesis in retinopathy of prematurity (ROP). Using a rat model representative of ROP, we found that regulation of VEGF signaling through VEGF receptor 2 (VEGFR2) in retinal microvascular endothelial cells (RMVECs) extended developmental angiogenesis but reduced pathologic angiogenesis, that is, intravitreal neovascularization (IVNV). We identified an adaptor protein, MEMO1, in IVNV in the rat model and tested the hypothesis that MEMO1 in RMVECs was important in IVNV by regulating signaling through VEGFR2. Instead, we found MEMO1 knockdown enhanced phosphorylation of VEGF-induced VEGFR2 and STAT3 and increased wound closure in vitro using cultured human RMVECs. Furthermore, MEMO1 overexpression suppressed VEGF-induced VEGFR2 and STAT3 phosphorylation and dampened VEGF-induced RMVEC wound closure. In contrast, in the absence of VEGF, MEMO1 overexpression promoted RMVEC proliferation in the wound closure assay and AKT phosphorylation, supporting a role for MEMO1 in VEGF-independent angiogenic processes. In vivo, retinal endothelial cell-specific knockdown of MEMO1 in the rat ROP model significantly increased IVNV but did not affect developmental angiogenesis. Our findings support a novel regulatory role for MEMO1 where MEMO1 limits VEGF-driven IVNV and promotes VEGF-independent angiogenic signaling. These results suggest MEMO1 may serve as a protective modulator of pathological angiogenesis in ROP and represent a potential therapeutic target to limit IVNV while preserving physiologic angiogenesis.

  View details for DOI 10.1096/fba.2025-00146

  View details for PubMedID 40936746

  View details for PubMedCentralID PMC12422028

• Phosphorylation of Y1212 (p-Y1212) on VEGFR2 affects developmental angiogenesis and neurogenesis in the retina Asare-Bediako, B., Satheesh, S., Ramshekar, A., Tankersley, M., Beri, S., Bright, M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2025

  View details for Web of Science ID 001560014200012

• Elucidating the role of MEMO1 in EPO-triggered signaling in retinal microvascular endothelial cells Ramshekar, A., Asare-Bediako, B., Jasmine Nguyen, Suresh, A., Hartnett, M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2024

  View details for Web of Science ID 001312227700347

• Short-term selective activation of phospho-Y1175 (p-Y1175) on VEGFR2 suppresses retinal endothelial cell migration Asare-Bediako, B., Ramshekar, A., Nguyen, J., Suresh, A., Hartnett, M. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2024

  View details for Web of Science ID 001312227706162

• The calvarium bone marrow responds to acute retinal injury and is resilient to chronic diabetes compared to long bone marrow Calzi, S., Asare-Bediako, B., Prasad, R., Adu-Agyeiwaah, Y., Rosencrans, R. F., Floyd, J., Stanford, D., Lin, A., Lydic, T. A., Boulton, M., Busik, J., Grant, M. B. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2024

  View details for Web of Science ID 001312227701023

• Sustained ACE2 Expression by Probiotic Improves Integrity of Intestinal Lymphatics and Retinopathy in Type 1 Diabetic Model JOURNAL OF CLINICAL MEDICINE Prasad, R., Adu-Agyeiwaah, Y., Floyd, J. L., Asare-Bediako, B., Li Calzi, S., Chakraborty, D., Harbour, A., Rohella, A., Busik, J. V., Li, Q., Grant, M. B. 2023; 12 (5)

  Abstract

  Intestinal lymphatic, known as lacteal, plays a critical role in maintaining intestinal homeostasis by regulating several key functions, including the absorption of dietary lipids, immune cell trafficking, and interstitial fluid balance in the gut. The absorption of dietary lipids relies on lacteal integrity, mediated by button-like and zipper-like junctions. Although the intestinal lymphatic system is well studied in many diseases, including obesity, the contribution of lacteals to the gut-retinal axis in type 1 diabetes (T1D) has not been examined. Previously, we showed that diabetes induces a reduction in intestinal angiotensin-converting enzyme 2 (ACE2), leading to gut barrier disruption. However, when ACE2 levels are maintained, a preservation of gut barrier integrity occurs, resulting in less systemic inflammation and a reduction in endothelial cell permeability, ultimately retarding the development of diabetic complications, such as diabetic retinopathy. Here, we examined the impact of T1D on intestinal lymphatics and circulating lipids and tested the impact of intervention with ACE-2-expressing probiotics on key aspects of gut and retinal function. Akita mice with 6 months of diabetes were orally gavaged LP-ACE2 (3x/week for 3 months), an engineered probiotic (Lactobacillus paracasei; LP) expressing human ACE2. After three months, immunohistochemistry (IHC) was used to evaluate intestinal lymphatics, gut epithelial, and endothelial barrier integrity. Retinal function was assessed using visual acuity, electroretinograms, and enumeration of acellular capillaries. LP-ACE2 significantly restored intestinal lacteal integrity as assessed by the increased expression of lymphatic vessel hyaluronan receptor 1 (LYVE-1) expression in LP-ACE2-treated Akita mice. This was accompanied by improved gut epithelial (Zonula occludens-1 (ZO-1), p120-catenin) and endothelial (plasmalemma vesicular protein -1 (PLVAP1)) barrier integrity. In Akita mice, the LP-ACE2 treatment reduced plasma levels of LDL cholesterol and increased the expression of ATP-binding cassette subfamily G member 1 (ABCG1) in retinal pigment epithelial cells (RPE), the population of cells responsible for lipid transport from the systemic circulation into the retina. LP-ACE2 also corrected blood-retinal barrier (BRB) dysfunction in the neural retina, as observed by increased ZO-1 and decreased VCAM-1 expression compared to untreated mice. LP-ACE2-treated Akita mice exhibit significantly decreased numbers of acellular capillaries in the retina. Our study supports the beneficial role of LP-ACE2 in the restoration of intestinal lacteal integrity, which plays a key role in gut barrier integrity and systemic lipid metabolism and decreased diabetic retinopathy severity.

  View details for DOI 10.3390/jcm12051771

  View details for Web of Science ID 000948257000001

  View details for PubMedID 36902558

  View details for PubMedCentralID PMC10003436

• Hematopoietic Cells Influence Vascular Development in the Retina CELLS Asare-Bediako, B., Adu-Agyeiwaah, Y., Abad, A., Li Calzi, S., Floyd, J. L., Prasad, R., DuPont, M., Asare-Bediako, R., Bustelo, X. R., Grant, M. B. 2022; 11 (20)

  Abstract

  Hematopoietic cells play a crucial role in the adult retina in health and disease. Monocytes, macrophages, microglia and myeloid angiogenic cells (MACs) have all been implicated in retinal pathology. However, the role that hematopoietic cells play in retinal development is understudied. The temporal changes in recruitment of hematopoietic cells into the developing retina and the phenotype of the recruited cells are not well understood. In this study, we used the hematopoietic cell-specific protein Vav1 to track and investigate hematopoietic cells in the developing retina. By flow cytometry and immunohistochemistry, we show that hematopoietic cells are present in the retina as early as P0, and include microglia, monocytes and MACs. Even before the formation of retinal blood vessels, hematopoietic cells localize to the inner retina where they eventually form networks that intimately associate with the developing vasculature. Loss of Vav1 lead to a reduction in the density of medium-sized vessels and an increased inflammatory response in retinal astrocytes. When pups were subjected to oxygen-induced retinopathy, hematopoietic cells maintained a close association with the vasculature and occasionally formed 'frameworks' for the generation of new vessels. Our study provides further evidence for the underappreciated role of hematopoietic cells in retinal vasculogenesis and the formation of a healthy retina.

  View details for DOI 10.3390/cells11203207

  View details for Web of Science ID 000872720000001

  View details for PubMedID 36291075

  View details for PubMedCentralID PMC9601270

• Fasting and fasting-mimicking treatment activate SIRT1/LXRα and alleviate diabetes-induced systemic and microvascular dysfunction DIABETOLOGIA Hammer, S. S., Vieira, C. P., McFarland, D., Sandler, M., Levitsky, Y., Dorweiler, T. F., Lydic, T. A., Asare-Bediako, B., Adu-Agyeiwaah, Y., Sielski, M. S., Dupont, M., Longhini, A., Calzi, S., Chakraborty, D., Seigel, G. M., Proshlyakov, D. A., Grant, M. B., Busik, J. V. 2021; 64 (7): 1674-1689

  Abstract

  Homo sapiens evolved under conditions of intermittent food availability and prolonged fasting between meals. Periods of fasting are important for recovery from meal-induced oxidative and metabolic stress, and tissue repair. Constant high energy-density food availability in present-day society contributes to the pathogenesis of chronic diseases, including diabetes and its complications, with intermittent fasting (IF) and energy restriction shown to improve metabolic health. We have previously demonstrated that IF prevents the development of diabetic retinopathy in a mouse model of type 2 diabetes (db/db); however the mechanisms of fasting-induced health benefits and fasting-induced risks for individuals with diabetes remain largely unknown. Sirtuin 1 (SIRT1), a nutrient-sensing deacetylase, is downregulated in diabetes. In this study, the effect of SIRT1 stimulation by IF, fasting-mimicking cell culture conditions (FMC) or pharmacological treatment using SRT1720 was evaluated on systemic and retinal metabolism, systemic and retinal inflammation and vascular and bone marrow damage.The effects of IF were modelled in vivo using db/db mice and in vitro using bovine retinal endothelial cells or rat retinal neuroglial/precursor R28 cell line serum starved for 24 h. mRNA expression was analysed by quantitative PCR (qPCR). SIRT1 activity was measured via histone deacetylase activity assay. NR1H3 (also known as liver X receptor alpha [LXRα]) acetylation was measured via western blot analysis.IF increased Sirt1 mRNA expression in mouse liver and retina when compared with non-fasted animals. IF also increased SIRT1 activity eightfold in mouse retina while FMC increased SIRT1 activity and expression in retinal endothelial cells when compared with control. Sirt1 expression was also increased twofold in neuronal retina progenitor cells (R28) after FMC treatment. Moreover, FMC led to SIRT1-mediated LXRα deacetylation and subsequent 2.4-fold increase in activity, as measured by increased mRNA expression of the genes encoding ATP-binding cassette transporter (Abca1 and Abcg1). These changes were reduced when retinal endothelial cells expressing a constitutively acetylated LXRα mutant were tested. Increased SIRT1/LXR/ABC-mediated cholesterol export resulted in decreased retinal endothelial cell cholesterol levels. Direct activation of SIRT1 by SRT1720 in db/db mice led to a twofold reduction of diabetes-induced inflammation in the retina and improved diabetes-induced visual function impairment, as measured by electroretinogram and optokinetic response. In the bone marrow, there was prevention of diabetes-induced myeloidosis and decreased inflammatory cytokine expression.Taken together, activation of SIRT1 signalling by IF or through pharmacological activation represents an effective therapeutic strategy that provides a mechanistic link between the advantageous effects associated with fasting regimens and prevention of microvascular and bone marrow dysfunction in diabetes.

  View details for DOI 10.1007/s00125-021-05431-5

  View details for Web of Science ID 000633274200002

  View details for PubMedID 33770194

  View details for PubMedCentralID PMC8236268