Self-assembled GFFYK peptide hydrogel enhances the therapeutic efficacy of mesenchymal stem cells in a mouse hindlimb ischemia model.

Mesenchymal stem cell (MSC) transplantation has emerged as a very promising strategy for the treatments of peripheral artery disease (PAD). However, MSC-based therapies are limited by low cell retention and survival rate in the ischemic zone. Small molecular (SM) hydrogels have shown attractive abilities to enhance the therapeutic effects of human MSCs via promoting their proliferation or maintaining their differentiation potential. Here, we designed and synthesized a new bioactive and biocompatible hydrogel, Nap-GFFYK-Thiol, using disulfide bonds as cleavable linkers to control the molecular self-assembly and we hypothesized this hydrogel could enhance the retention and engraftment of human placenta-derived MSCs (hP-MSCs) in a mouse ischemic hindlimb model. In vitro results demonstrated that the Nap-GFFYK-Thiol hydrogel increased cell viability through paracrine effects. Moreover, it enhanced the proangiogenic and anti-apoptotic effects of hP-MSCs. In vivo, Nap-GFFYK-Thiol hydrogel improved the hP-MSC retention in the murine ischemic hindlimb model as visualized by bioluminescence imaging. Furthermore, cotransplantation of hP-MSCs with hydrogel improved blood perfusion, leading to superior limb salvage. These therapeutic effects may attribute to reduced inflammatory cell infiltration, enhanced angiogenesis as well as suppressed collagen deposition. In conclusion, the Nap-GFFYK-Thiol hydrogel fabricated using disulfide bonds as cleavable linkers serves as an artificial niche for promoting hP-MSC survival and proangiogenic factor secretion in PAD therapy and thereby provide an alternative strategy for PAD therapy. STATEMENT OF SIGNIFICANCE: Although several phase I/II clinical trials of MSC-based treatments for critical limb ischemia (CLI) are ongoing, MSC-based therapies are still challenged by the low quality and quantity of cells in the ischemic zone, especially in cases of extensive or irreversible damage. Hydrogels have favorable biocompatibility and safety records in the medical field. In the current study, we engineered a new bioactive and biocompatible hydrogel, Nap-GFFYK-Thiol, using disulfide bonds as cleavable linkers to enhance the therapeutic efficacy of human placenta-derived MSCs (hP-MSCs) in mouse limb ischemia model. Notably, Nap-GFFYK-Thiol hydrogel acts as an artificial niche for promoting hP-MSC survival and proangiogenic factor secretion in PAD therapy, which further promoted the restoration of blood perfusion and regeneration of muscle cells. Considering the proangiogenic effect of Nap-GFFYK-Thiol on hP-MSCs, our results may provide a new strategy for the treatment of PAD.