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Cytomatrix |
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Tissue Engineering Bone Marrow and Thymus Abstract |
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Michael Rosenzweig, B.V.Sc., Ph.D.
Chief Scientific Officer, Cytomatrix, Woburn, MA |
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Ex-vivo engineering of tissues is directed at recreating in vivo microenvironments that recapitulate the biology required for the formation and maintenance of complex tissues. We have developed a porous, biocompatible three-dimensional tissue scaffold, CellfoamTM, which we have used to recreate the spatial arrangement of cells in tissues such as the bone-marrow and thymus. Attempts to culture hematopoietic stem cells (HSCs) ex vivo have generally required the use of cytokines and serum, and although cell expansion is achieved, it is often at the cost of terminal differentiation of the cells, loss of pluripotency and failure to engraft in vivo. Using a culture system that incorporates the CellfoamTM matrix, we have been able to successfully culture and expand hematopoietic progenitors ex vivo without the addition of exogenous cytokines. HSCs isolated from bone marrow, peripheral blood and umbilical cord blood that have been cultured in this system for 14 days have been shown to retain phenotype and function in a number of standard in vitro assays, as well as engraftment capacity in an NOD/SCID model. This demonstrates that alternative strategies can be employed to successfully expand HSCs ex vivo, which has obvious implications for the field of stem cell transplantation. In related work, we have engineered a thymic organoid using the CellfoamTM matrix to support the growth of thymic stroma in a three-dimensional arrangement. The co-culture of HSCs with this engineered artificial thymus yields mature, polyclonal T cells. Further evidence of in vivo mimicry is the demonstration of a phenotype consistent with thymic differentiation as well as specific characteristics of de novo T cell generation, such as an increase in the number of T cell receptor excisional circles (TRECs). The CellfoamTM technology has thus proven effective for the ex-vivo engineering of a number of tissue types.   |
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