Human periodontal ligament stem cells-derived exosomes-loaded hybrid hydrogel enhances the calvarial defect regeneration in middle-age rats

Advances in bone tissue engineering through integrating biologically active extracellular nanovesicles with biomaterial platforms offer a promising solution to overcome the reduced residual bone volume and provide an efficient bone regeneration. Within the scope of clinical research in the field of regenerative medicine, this work represents the potential of human periodontal ligament fibroblasts (hPDLFs)-derived exosomes (hPDLFs-Exo) as a cell-free regenerative therapy tool in the repair of calvarial bone damage by utilizing their cell-instructive potential. To this aim, isolated hPDLFs-Exo were integrated with UV-responsive gelatine methacrylate (GelMA) hydrogels, which enable the development of a robust and biologically active platform for the regeneration of a critical-sized calvarial defect at middle-age rats (6-months old). In vitro tests revealed that human adipose mesenchymal stem cells (hAMSC) on GelMA/hPDLFs-Exo hydrogels begin to up-regulate RUX2, ALP, and OSP expressions, that support the hypothesis of growth factors-free induction of osteogenic differentiation in hMSCs. In vivo results obtained by micro-computed tomography (μ-CT), histochemistry, and gene expression analyses confirmed that rats treated with GelMA/hPDLFs-Exo posed higher new bone mineralization compared to the negative controls. Obtained results highlighted the potential of GelMA/hPDLFs-Exo hydrogel to attract endogenous stem cells and instruct into osteogenesis, providing bone damage repair. Consequently, the developed GelMA/hPDLFs-Exo hydrogel has the potential to be used in bone tissue engineering as a cell-free therapy approach.