C-Met-Activated Mesenchymal Stem Cells Rescue Ischemic Damage via Interaction with Cellular Prion Protein

Abstract

Background/Aims: Stem cell transplantation has emerged as a promising therapeutic strategy, but the exact mechanisms by which stem cells exposed to hypoxic conditions increase the survival rate and rescue ischemic injury at the graft site are not well known. In this study, we aimed to determine if c-Met-activated mesenchymal stem cells (MSCs) pre-exposed to hypoxia promote therapeutic efficacy when transplanted to ischemic models, and whether c-Met interacts with cellular prion protein (PrP^C) present in the ischemic tissue. Methods: Western blot analysis was performed to determine the expression levels of PrP^C, C-caspase-3, and C-PARP-1, as well as the phosphorylation of Akt, p38, JNK, and BAX. A co-immunoprecipitation assay was performed to show that PrP^C binds with c-Met in vitro. An adhesion assay was performed to explore the alterations in MSCs attached to myoblasts (in vitro), and an invasion assay was performed to determine the effect on MSC invasion capacity upon interaction with myoblast-induced c-Met and PrP^C. CD31-positive capillaries and αSMA-positive arterioles in in vivo hindlimb ischemic tissue were quantified by immunofluorescence staining. The level of apoptosis in the tissue of each group was assessed by quantifying the number of C-caspase-3-positive cells. Finally, laser Doppler technology was utilized to detect the enhanced angiogenic effects in vivo. Results: We showed that hypoxic conditions increased PrP^C levels in vivo (hindlimb ischemic tissue) and in vitro (myoblasts) and increased c-Met levels in MSCs. To identify the relationship between c-Met from MSCs and PrP^C from myoblasts, we used a co-culturing system with myoblasts and MSCs pre-exposed to hypoxia. Hypoxia increased the phosphorylation of mitogen-activated protein kinases. Transplantation of hypoxia-pre-exposed MSCs to the ischemic site increased anti-apoptosis and enhanced the survival and proliferation of transplanted MSCs in a murine hindlimb model, resulting in improved functional recovery of the ischemic tissue. All the aforementioned effects were inhibited by the pretreatment of MSCs with the c-Met-neutralizing antibody Conclusion: c-Met-activated MSCs pre-exposed to hypoxia interact with PrP^C at the site of ischemic injury to increase the efficiency of MSC transplantation. Hence, our study demonstrated that c-Met is a potential target for MSC-based therapies.