Co-culture of human bone marrow stromal cells with endothelial cells alters gene expression profiles

The intricate relationship between angiogenesis and osteogenesis in vivo must be replicated in bone tissue engineering constructs to ensure the formation of a functional vascular network to support successful bone formation. Although communication between bone marrow stromal cells (MSC) and endothelial cells (EC) is recognized as one of the most important cellular interactions in bone regeneration, the underlying mechanisms of this biological process are not well understood. The purpose of this study was to analyze global gene expression associated with intercellular communication between MSC and EC using HumanWG-6 v3.0 expression BeadChips with a one-channel platform system (Illumina, San Diego, CA, USA). Each array contains more than 48,000 probes derived from human genes. A global map of MSC gene expression was generated following co-culture of MSC with EC for 5 and 15 days, in a direct-contact model. The map was used to determine relative alterations in functional processes and pathways. Co-culturing EC with MSC up-regulated genes related to angiogenesis as von Willebrand factor, platelet/endothelial cell adhesion molecule-1, cadherin 5, angiopoietin-related protein 4, and cell surface antigen CD34, and genes playing important roles in osteogenesis as alkaline phosphatase, FK506 binding protein 5, and bone morphogenetic protein. These findings clearly demonstrated that EC had a significant impact on MSC, particularly the bidirectional regulation of angiogenesis and osteogenesis. Moreover, cell-matrix interactions and TGF-beta signal pathways were implicated for a crucial role in endothelial, cell-induced gene regulation in MSCs. A detailed study of the functional correlates of the microarray data is warranted to explore cellular and molecular interactions of importance in bone tissue engineering.