Irisin improves delayed bone repair in diabetic female mice

Irisin-loaded electrospun core-shell nanofibers as calvarial periosteum accelerate vascularized bone regeneration by activating the mitochondrial SIRT3 pathway

The scarcity of native periosteum poses a significant clinical barrier in the repair of critical-sized bone defects. The challenge of enhancing regenerative potential in bone healing is further compounded by oxidative stress at the fracture site. However, the introduction of artificial periosteum has demonstrated its ability to promote bone regeneration through the provision of appropriate mechanical support and controlled release of pro-osteogenic factors. In this study, a poly (l-lactic acid) (PLLA)/hyaluronic acid (HA)-based nanofibrous membrane was fabricated using the coaxial electrospinning technique. The incorporation of irisin into the core-shell structure of PLLA/HA nanofibers (PLLA/HA@Irisin) achieved its sustained release. In vitro experiments demonstrated that the PLLA/HA@Irisin membranes exhibited favorable biocompatibility. The osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) was improved by PLLA/HA@Irisin, as evidenced by a significant increase in alkaline phosphatase activity and matrix mineralization. Mechanistically, PLLA/HA@Irisin significantly enhanced the mitochondrial function of BMMSCs via the activation of the sirtuin 3 antioxidant pathway. To assess the therapeutic effectiveness, PLLA/HA@Irisin membranes were implanted in situ into critical-sized calvarial defects in rats. The results at 4 and 8 weeks post-surgery indicated that the implantation of PLLA/HA@Irisin exhibited superior efficacy in promoting vascularized bone formation, as demonstrated by the enhancement of bone matrix synthesis and the development of new blood vessels. The results of our study indicate that the electrospun PLLA/HA@Irisin nanofibers possess characteristics of a biomimetic periosteum, showing potential for effectively treating critical-sized bone defects by improving the mitochondrial function and maintaining redox homeostasis of BMMSCs.

Knockdown of SIRT3 perturbs protective effects of irisin against bone loss in diabetes and periodontitis

A well-recognized risk factor for periodontitis, diabetes mellitus (DM) aggravates periodontal disease with increasing alveolar bone loss. As a novel myokine, irisin is closely linked with bone metabolism. Nonetheless, the effects of irisin on periodontitis under diabetic conditions and the underlying mechanisms remain poorly understood. Here, we showed that local irisin treatment ameliorates alveolar bone loss and oxidative stress, increases SIRT3 expression within periodontal tissues of our experimentally-induced diabetes and periodontitis (DP) rat models. By culturing the periodontal ligament cells (PDLCs) in vitro, we found that irisin could partially rescue inhibited cell viability, mitigate accumulated intracellular oxidative stress, ameliorate mitochondrial dysfunctions, and restore disturbed osteogenic and osteoclastogenic capacities of PDLCs when exposed to high glucose and pro-inflammatory stimulation. Furthermore, lentivirus-mediated SIRT3 knockdown was employed to unravel the underlying mechanism by which SIRT3 mediated irisin's beneficial effects on PDLCs. Meanwhile, in SIRT3-deficient mice, irisin treatment did not protect against alveolar bone destruction and oxidative stress accumulation in DP models, which underlined the crucial role of SIRT3 in mediating the positive effects of irisin on DP. Our findings, for the first time, revealed that irisin attenuates alveolar bone loss and oxidative stress via activation of the SIRT3 signaling cascade, and highlighted its therapeutic potential for the treatment of DP.