This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The cells have been variously referred to as colony-forming fibroblasts, mesenchymal stem cells, or marrow stromal cells (MSCs), and have been attracting increasing interest both for their biological properties as multipotential stem-like cells and their potential use for cell and gene therapy. However, a major problem in the field has been that reproducible conditions for isolation and expansion of the cells in culture has not been defined. The overall aim of the present proposal is to develop effective conditions for their isolation and expansion of human hMSCs in culture based on three recent observations made in our laboratory: 1) we have developed culture conditions whereby hMSCs can be expanded over 108-fold without significant loss in replicative capacity; 2) we have found that the replication of hMSCs in culture is regulated autocrine/paracrine factors that can be recovered from the culture medium; 3) we have identified a sub-population of small granular cells in cultures of hMSCs that are highly replicative and appear to be the earliest progenitors in the cultures.
The specific aims of this protocol are: l) to determine whether the highly replicative cells we have obtained after 108-fold expansion of hMSCs retain their multiopotentiality to differentiate into osteoblasts, chondrocytes, and adipocytes; 2) isolate and characterize the secreted factors that regulate replication of hMSCs in culture; 3) isolate the small, granular, and highly replicative cells we have identified in cultures of hMSCs and define their surface epitopes.
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