CD44 regulates extracellular matrix assembly by umbilical cord mesenchymal stem cells enabling host rejection suppression.

Abstract

Purpose: Umbilical cord mesenchymal stem cells (UMSCs) have unique immunosuppressive properties enabling them to evade host rejection and making them valuable tools for cell therapy. We previously showed that human UMSCs exposed to inflammatory cells synthesize a rich extracellular glycocalyx composed of the chondroitin sulfate-proteoglycan versican bound to a heavy chain (HC)-modified hyaluronan (HA) matrix (HC-HA) which modulates the host immune response enabling them to survive xenograft transplantation. This rich glycocalyx which modulates the immune response is bound to the UMSC by cell surface CD44. In present studies we examined the hypothesis that CD44 plays an intricate role in conferring the ability of UMSC to regulate inflammatory cells via withholding the newly synthesized glycocalyx on the cellular surface.

Methods: UMSC were treated with CD44 shRNA in order to produce a UMSC knock-out cell line for CD44 (UMSC^ΔCD44). Thereafter, both the glycocalyx and the ability of these cells to modulate inflammatory cells were analyzed.

Results: Treating UMSC with shRNAi of CD44 resulted in a 60% reduction of CD44 protein levels. UMSC^ΔCD44(down regulated CD44) failed to produce the cable-like HA structures which we have previously shown capture macrophages in the wild-type cells. Moreover, the UMSC^ΔCD44fibroblast-like points of adhesion appear bent like palm-tree fronds and the glycocalyx deposition was greatly reduced. Consequently, UMSC UMSC^ΔCD44 presented a significant loss in the ability to modulate inflammatory cells.

Conclusions: : Our observation support the notion that cell surface CD44 is required for the correct assemble of the UMSC glycocalyx for modulating inflammatory cells.