Sustained Release of Melatonin from GelMA Liposomes Reduced Osteoblast Apoptosis and Improved Implant Osseointegration in Osteoporosis

A reduction in bone mass around an implant is the main cause of implant loosening, especially in postmenopausal osteoporosis patients. In osteoporosis, excessive oxidative stress, resulting in osteoblast apoptosis, largely contributes to abnormal bone remodeling. Melatonin (MT) synthesized by the pineal gland promotes osteoblast differentiation and bone formation and has been effectively used to combat oxidative stress. Therefore, we hypothesized that MT attenuates osteoblast apoptosis induced by oxidative stress, promotes osteogenesis in osteoporosis, and improves bone mass around prostheses. Moreover, considering the distribution and metabolism of MT, its systemic administration would require a large amount of MT, increasing the probability of drug side effects, so the local administration of MT is more effective than its systemic administration. In this study, we constructed a composite adhesive hydrogel system (GelMA-DOPA@MT) to bring about sustained MT release in a local area. Additionally, MT-reduced apoptosis caused by hydrogen peroxide- (H2O2-) induced oxidative stress and restored the osteogenic potential of MC3T3-E1 cells. Furthermore, apoptosis in osteoblasts around the implant was significantly attenuated, and increased bone mass around the implant was observed in ovariectomized (OVX) rats treated with this composite system. In conclusion, our results show that GelMA-DOPA@MT can inhibit osteoblast apoptosis caused by oxidative stress, thereby promoting osteogenesis and improving bone quality around a prosthesis. Therefore, this system of local, sustained MT release is a suitable candidate to address implant loosening in patients with osteoporosis.