Collagen Receptor-Mediated Mechanochemical Signaling Contributes to Human Pro-Angiogenic Mesenchymal Stem/Progenitor Cell-Induced Neo-Vasculogenesis

Human mesenchymal stem/progenitor cells (MSPCs) are important tools for tissue repair and regenerative approaches. Co-application of autologous pairs of human MSPCs and endothelial colony forming progenitor cells (ECFCs) drives vessel formation in a mouse model. However, a more detailed mechanistic insight into the contribution of MSPCs to vasculogenesis is required prior to a potential application in clinical trials. The formation of perfused blood vessels following the co-injection of MSPC/ECFC pairs requires directed migration of these cell types through the extracellular matrix. For this, cells must interpret and respond to both biochemical cues and physical parameters of the matrix. Here we aimed at identifying changes in early signaling molecules that could potentially mediate these complex behaviors in ECFCs and MSPCs.

By antibody array analysis of biopsies from vasculogenic regions we identified the levels of the discoidin domain receptor 2 (DDR2) to be upregulated about twofold in MSPCs in an MSPC/ECFC mixture compared to MSPC-only implants. Expression of DDR2 was confirmed by flow cytometry analysis. Employing immunofluorescence microscopy we showed components of the mechanotransduction and cytoskeleton machinery (Paxillin, ILK, Src, h1CaP, and cortactin) to be abundantly expressed and correctly localized in MSPCs. MSPCs also responded to manipulation of cytoskeletal integrity with phorbol dibutyrate or Y-27632, demonstrating the presence of a tissue transmigration machinery in MSPCs. Applying various three dimensional cell culture strategies we identified significant alterations in MSPC morphology, as well as in the mRNA levels for DDR1 and DDR2, and for miRNAs 29b, 199a, 331 in response to different matrix conditions.

Our data suggest a mechanosensitive regulation of MSPC function and we thus conclude that direct or indirect (miRNA-mediated) regulation of the collagen receptors DDR1/2 could have a role in modulating MSPC function during stem-cell induced neo-vascularization in vivo.

No relevant conflicts of interest to declare.