3 years ago

Human Bone Marrow Mesenchymal stromal cell derived Osteoblasts Promote the Expansion of Hematopoietic Progenitors through Beta-Catenin and Notch Signaling Pathways.

Roya Pasha, Emily Doxtator, Owen Hovey, Nicolas Pineault, Suria Jahan, Ahmad Abu-Khader, Gavin Boisjoli, Matthew Michalicka
Coculture of hematopoietic stem cells (HSC) with primary stromal cells from HSC niches supports the maintenance and expansion of HSC and progenitors ex vivo. However, a major drawback is the availability of primary human samples for research and clinical applications. We investigated the use of in vitro derived osteoblasts as a new source of feeder cells and characterized the molecular pathways that mediate their growth promoting activities. First, we compared the growth and differentiation modulating activities of mesenchymal stromal cells (MSC)-derived osteoblasts (M-OST) to that of their undifferentiated precursor on umbilical cord blood (UCB) progenitors. Feeder-free cultures were also included as baseline control. Cell growth and expansion of hematopoietic progenitors were significantly enhanced by both feeder cell types. However, progenitor cell growth was considerably greater with M-OST. Coculture also promoted the maintenance of immature CD34+ progenitor subsets and modulated in a positive fashion the expression of several homing-related cell surface receptors, in a feeder-specific fashion. Serial transplantation experiments revealed that M-OST coculture supported the maintenance of long-term lympho-myeloid reconstituting HSC that provided engraftment levels generally superior to that from MSC cocultures. Mechanistically, we found that coculture with M-OST was associated with enhanced -catenin (-Cat) activity in UCB cells and that abrogation of -Cat/TCF activity blunted the growth promoting activity of the M-OST coculture. Conversely, Notch inhibition reduced UCB cell expansion but to a much lesser extent. In conclusion, this study demonstrates that M-OST are excellent feeder cells for HSC and progenitors, and identify key molecular pathways responsible for the growth enhancing activities of osteoblasts on UCB progenitors.

Publisher URL: http://doi.org/10.1089/scd.2017.0133

DOI: 10.1089/scd.2017.0133

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