Injectable nanohydroxyapatite-chitosan-gelatin micro-scaffolds induce regeneration of knee subchondral bone lesions

Subchondral bone has been identified as an attractive target for KOA. To determine whether a minimally invasive micro-scaffolds could be used to induce regeneration of knee subchondral bone lesions, and to examine the protective effect of subchondral bone regeneration on upper cartilage, a ready-to-use injectable treatment with nanohydroxyapatite-chitosan-gelatin micro-scaffolds (HaCGMs) is proposed. Human-infrapatellar-fat-pad-derived adipose stem cells (IPFP-ASCs) were used as a cellular model to examine the osteo-inductivity and biocompatibility of HaCGMs, which were feasibly obtained with potency for multi-potential differentiations. Furthermore, a subchondral bone lesion model was developed to mimic the necrotic region removing performed by surgeons before sequestrectomy. HaCGMs were injected into the model to induce regeneration of subchondral bone. HaCGMs exhibited desirable swelling ratios, porosity, stiffness, and bioactivity and allowed cellular infiltration. Eight weeks after treatment, assessment via X-ray imaging, micro-CT imaging, and histological analysis revealed that rabbits treated with HaCGMs had better subchondral bone regeneration than those not treated. Interestingly, rabbits in the HaCGM treatment group also exhibited improved reservation of upper cartilage compared to those in other groups, as shown by safranin O-fast green staining. Present study provides an in-depth demonstration of injectable HaCGM-based regenerative therapy, which may provide an attractive alternative strategy for treating KOA.