Hyaluronic acid-based hydrogels with tobacco mosaic virus containing cell adhesive peptide induce bone repair in normal and osteoporotic rats

Tobacco mosaic virus (TMV) has been studied as a multi-functional agent for bone tissue engineering. An osteo-inductive effect of wild-type TMV has been reported, as it can significantly enhance the bone differentiation potential of bone marrow stromal cells both on a two-dimensional substrate and in a three-dimensional (3D) hydrogel system. A TMV mutant (TMV-RGD1) was created which featured the adhesion peptide arginyl-glycyl-aspartic acid (RGD), the most common peptide motif responsible for cell adhesion to the extracellular matrix, on the surface of the virus particle to enhance the bio-functionality of the scaffold material. We hypothesised that the incorporation of either wild-type TMV or TMV-RGD1 in the 3D hydrogel scaffold would induce bone healing in critical size defects of the cranial segmental bone. We have previously tested the virus-functionalised scaffolds, in vitro, with a hyaluronic acid-based system as an in-situ hydrogel platform for 3D cell encapsulation, culture, and differentiation. The results of these experiments suggested the potential of the virus-functionalised hydrogel to promote in vitro stem cell differentiation. The hydrogel-forming system we employed was shown to be safe and biocompatible in vivo. Here, we further explored the physiological responses regarding bone regeneration of a calvarial defect in both normal and osteoporotic ovariectomized rat models. Our results, based on histological analysis in both animal models, suggested that both wild-type TMV and TMV-RGD1 functionalised hydrogels could accelerate bone regeneration, without systemic toxicity, evaluated by blood counts. New bone formation was intensified by the incorporation of the RGD-mutant viral particles. This finding increased the potential for use of the rod-shaped plant virus as a platform for the addition of powerful biofunctionality for tissue engineering applications. This study was approved by the Ethics Committee on Animal Use of the Zhenjiang Affiliated First People’s Hospital affiliated to Jiangsu University