Hydrogen sulfide-releasing silk fibroin scaffold for bone tissue engineering.

Hydrogen sulfide (HS)-based therapy is a promising therapeutic strategy for several biomedical applications. Following the observation that endogenous and exogenous HS plays a prominent role as a bone anabolic agent, we recently developed a silk fibroin (SF) porous scaffold loaded with GYY4137 (GYY), an HS donor, for applications in bone tissue engineering. Here, we assayed whether the combination of SF with HS potentiates the osteoconductive properties of SF. Biocompatibility and osteoanabolic activity were assayed in vitro using human bone marrow mesenchymal stromal cells. Cell cultures were performed on a perfusion bioreactor to obtain results closer to the in vivo microenvironment. Cytotoxicity was excluded by lactate dehydrogenase and live/dead assays. Cell colonization and mineral apposition were evaluated by Haematoxylin & Eosin and Von Kossa/Alizarin Red-S stainings respectively. PCR array for human osteogenesis and immunohistochemical analyses were performed to identify pathways and targets involved. Our findings show that HS-releasing SF scaffolds supported cell adhesion, proliferation and viability. Moreover, HS activated genes and proteins involved in ossification, osteoblast differentiation, bone mineral metabolism and angiogenesis allowing a high and early mineralization. Based on these properties, we suggest the use of HS-releasing SF scaffolds for bone healing and regeneration applications.