Current Role at Stanford

Teaching Assistant - Master of Science in Translational Research and Applied Medicine

Education & Certifications

  • Bachelor of Science, Cal Poly Humboldt, Biochemistry (2021)
  • Master of Science, Stanford University, Translational Research and Applied Medicine (2023)

All Publications

  • Purification and functional characterization of novel human skeletal stem cell lineages. Nature protocols Hoover, M. Y., Ambrosi, T. H., Steininger, H. M., Koepke, L. S., Wang, Y., Zhao, L., Murphy, M. P., Alam, A. A., Arouge, E. J., Butler, M. G., Takematsu, E., Stavitsky, S. P., Hu, S., Sahoo, D., Sinha, R., Morri, M., Neff, N., Bishop, J., Gardner, M., Goodman, S., Longaker, M., Chan, C. K. 2023


    Human skeletal stem cells (hSSCs) hold tremendous therapeutic potential for developing new clinical strategies to effectively combat congenital and age-related musculoskeletal disorders. Unfortunately, refined methodologies for the proper isolation of bona fide hSSCs and the development of functional assays that accurately recapitulate their physiology within the skeleton have been lacking. Bone marrow-derived mesenchymal stromal cells (BMSCs), commonly used to describe the source of precursors for osteoblasts, chondrocytes, adipocytes and stroma, have held great promise as the basis of various approaches for cell therapy. However, the reproducibility and clinical efficacy of these attempts have been obscured by the heterogeneous nature of BMSCs due to their isolation by plastic adherence techniques. To address these limitations, our group has refined the purity of individual progenitor populations that are encompassed by BMSCs by identifying defined populations of bona fide hSSCs and their downstream progenitors that strictly give rise to skeletally restricted cell lineages. Here, we describe an advanced flow cytometric approach that utilizes an extensive panel of eight cell surface markers to define hSSCs; bone, cartilage and stromal progenitors; and more differentiated unipotent subtypes, including an osteogenic subset and three chondroprogenitors. We provide detailed instructions for the FACS-based isolation of hSSCs from various tissue sources, in vitro and in vivo skeletogenic functional assays, human xenograft mouse models and single-cell RNA sequencing analysis. This application of hSSC isolation can be performed by any researcher with basic skills in biology and flow cytometry within 1-2 days. The downstream functional assays can be performed within a range of 1-2 months.

    View details for DOI 10.1038/s41596-023-00836-5

    View details for PubMedID 37316563

    View details for PubMedCentralID 6568007

  • In vivo tracking of KCC2b expression during early brain development. The Journal of comparative neurology Jones, E. F., Butler, M. G., Trendafilova, D., Mendez, M. S., Jernigan, L. A., Gahtan, E., Steele, J. 2023; 531 (1): 48-57


    The neuronal chloride (Cl-) exporter, KCC2, regulates neuron excitability and development and undergoes a stereotypical pattern of delayed upregulation as neurons mature. KCC2 upregulation favors neural inhibition by establishing a negative Cl- gradient, ensuring GABA-induced Cl- currents are inward and inhibitory. We developed a zebrafish fluorescent reporter line, KCC2b:mCitrine, to track KCC2 expression in vivo during early brain development. KCC2b:mCitrine was first detected at 16 h postfertilization and by day 6 labeled most central and peripheral neurons and processes. At 20 h, expression was greatest in the soma-dense basal neuroepithelium but largely absent in apical and mantle zones where differentiation and migration primarily occur, and time lapse imaging at this stage supports a postmigration upregulation of KCC2b. Central dopamine neurons showed low KCC2b expression as observed in other species. KCC2b:mCitrine fluorescence was stable over minutes in most neurons, but brightness transients observed in single cells fit our expectation for real-time tracking of KCC2b upregulation in new neurons. To further assess whether fluorescence brightness tracks KCC2b expression, zebrafish embryos were exposed to bisphenol-A (BPA), which is known to suppress KCC2 expression. Fluorescence decreased after 6 days of BPA exposure but not after 2 or 4 days, suggesting that it is an accurate but delayed indicator of KCC2b expression. KCC2b:mCitrine zebrafish present a new method for visualizing KCC2b's complex dynamics during brain development, and potentially screening compounds aimed at modulating KCC2 expression.

    View details for DOI 10.1002/cne.25411

    View details for PubMedID 36217249

  • Aging of Skeletal Stem Cells. Advances in geriatric medicine and research Butler, M. G., Ambrosi, T. H., Murphy, M. P., Chan, C. K. 2022; 4 (2)


    The skeletal system is generated and maintained by its progenitors, skeletal stem cells (SSCs), across the duration of life. Gradual changes associated with aging result in significant differences in functionality of SSCs. Declines in bone and cartilage production, increase of bone marrow adipose tissue, compositional changes of cellular microenvironments, and subsequent deterioration of external and internal structures culminate in the aged and weakened skeleton. The features and mechanisms of skeletal aging, and of its stem and progenitor cells in particular, are topics of recent investigation. The discovery of functionally homogeneous SSC populations with a defined cell surface phenotype has allowed for closer inspection of aging in terms of its effects on transcriptional regulation, cell function, and identity. Here, we review the aspects of SSC aging on both micro- and macroscopic levels. Up-to-date knowledge of SSC biology and aging is presented, and directions for future research and potential therapies are discussed. The realm of SSC-mediated bone aging remains an important component of global health and a necessary facet in our understanding of human aging.

    View details for DOI 10.20900/agmr20220006

    View details for PubMedID 36037035

  • Cross-species comparisons reveal resistance of human skeletal stem cells to inhibition by non-steroidal anti-inflammatory drugs. Frontiers in endocrinology Goodnough, L. H., Ambrosi, T. H., Steininger, H. M., Butler, M. G., Hoover, M. Y., Choo, H., Van Rysselberghe, N. L., Bellino, M. J., Bishop, J. A., Gardner, M. J., Chan, C. K. 2022; 13: 924927


    Fracture healing is highly dependent on an early inflammatory response in which prostaglandin production by cyclo-oxygenases (COX) plays a crucial role. Current patient analgesia regimens favor opioids over Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) since the latter have been implicated in delayed fracture healing. While animal studies broadly support a deleterious role of NSAID treatment to bone-regenerative processes, data for human fracture healing remains contradictory. In this study, we prospectively isolated mouse and human skeletal stem cells (SSCs) from fractures and compared the effect of various NSAIDs on their function. We found that osteochondrogenic differentiation of COX2-expressing mouse SSCs was impaired by NSAID treatment. In contrast, human SSCs (hSSC) downregulated COX2 expression during differentiation and showed impaired osteogenic capacity if COX2 was lentivirally overexpressed. Accordingly, short- and long-term treatment of hSSCs with non-selective and selective COX2 inhibitors did not affect colony forming ability, chondrogenic, and osteogenic differentiation potential in vitro. When hSSCs were transplanted ectopically into NSG mice treated with Indomethacin, graft mineralization was unaltered compared to vehicle injected mice. Thus, our results might contribute to understanding species-specific differences in NSAID sensitivity during fracture healing and support emerging clinical data which conflicts with other earlier observations that NSAID administration for post-operative analgesia for treatment of bone fractures are unsafe for patients.

    View details for DOI 10.3389/fendo.2022.924927

    View details for PubMedID 36093067