(178d) Effects of Hypoxic, hMSC-Derived ECM Matrices On hMSC Characteristics

In vivo, human mesenchymal stem cells (hMSCs) reside in a low oxygen tension environment in the bone marrow. In vitro, recent studies have shown that MSCs exhibited greater colony forming ability, proliferated faster and longer, and maintained their undifferentiated characteristics better under low oxygen conditions. Hypoxia also influences the composition of the extracellular matrix (ECM) proteins, which are also part of the specialized MSC niche in vivo. As both oxygen tension and ECM matrices are important components of the in vivo hMSC microenvironment, the objective of this study is to investigate the effects of oxygen tension on the properties of the hMSC-derived ECM matrices and their combined influences on hMSC phenotype, gene expressions, and MAPK signaling pathways. We first derived ECM matrices made under hypoxia (2% O2) and normoxia (20%) and found that oxygen tension regulates the composition of the ECM matrices with significantly increased fibronectin and collagen under hypoxia. The hypoxic ECM matrices also promoted hMSC proliferation and maintained higher CFU-F forming ability compared to their normoxia counterparts. As the mitogen-activated protein kinase (MAPK) pathways have been implicated in both hypoxia- and ECM-mediated hMSC responses, we are in the process of analyzing the activation of regulatory kinases and their contribution to hMSC proliferation and phenotype. Together, the results will help determine the role of hMSC microenvironment including hypoxia and components of ECM matrices, and further delineate the regulatory mechanisms governing hMSC proliferation and cell fate.