CONTROL OF STEM CELL BEHAVIOR BY EXPOSURE TO TISSUE-SPECIFIC ECM

Adipose tissue-derived mesenchymal stem cells (AD-MSCs) have the potential to serve as a critical toolfor bone tissue engineering as their relatively high frequency in the body can provide the exceedingly largenumbers of cells required for regenerative therapies. Unfortunately, many studies have shown that AD-MSCshave considerably less osteogenic potential than other types of stem cells. Our group has developed an invitro-produced extracellular matrix (ECM) that recapitulates specific attributes of the native bone marrow (BM-)and adipose (AD-) microenvironment. In previous studies, we demonstrated that BM-ECM significantlypromotes osteogenic differentiation by bone marrow (BM)-derived MSCs relative to standard culture plastic. Inthe current proposal, we evaluate the potential of BM-ECM to increase the osteogenic capacity of AD-MSCs,and by doing so, dramatically improve their clinical relevance for skeletal repair and regeneration. Our preliminary data show that BM- and AD-derived ECMs are capable of guiding BM-MSC differentiationtowards osteoblast and adipocyte lineages. These ECMs are characterized by significant differences inbiochemical composition, architecture and even mechanical properties. We demonstrated that BM- and AD-MSCs cultured on both types of tissue-specific ECM proliferated more readily when each type of MSC wasmaintained on ECM-derived from the same respective tissue. Additionally, we observed that BM- and AD-MSCs both exhibited low-circularity spreading on BM-ECM, while on AD-ECM, they displayed a high-circularityspreading morphology. These observations are consistent with recent reports demonstrating that changes inMSC morphology are ultimately related to signaling cues involved in lineage-decisions. Furthermore, recentstudies have suggested that focal adhesion complex formation can regulate stem cell fate decisions throughthe canonical Wnt/?-catenin pathway. We will investigate if unique focal adhesion complexes form on tissue-specific ECMs and reconstitute the microenvironment(s) responsible for directing MSC differentiation to eitherthe osteoblast and adipocyte lineage. As a result of these observations, we hypothesize that the bone-specific microenvironment of BM-ECMcan 're-train' AD-MSCs in order to enhance their osteogenic potential. The following specific aims areproposed to test this hypothesis: 1) To determine differences in BM- and AD-MSC differentiation, assessedwith assays of osteogenesis and adipogenesis in vitro and in vivo, with culture on tissue culture plastic (TCP)and tissue-specific ECM and 2) To determine the molecular mechanism(s) responsible for promoting MSCdifferentiation to the osteoblast and adipocyte lineages with culture on TCP and tissue-specific ECM.