Immediately injectable modified gelatin and hyaluronic acid-based hydrogel encapsulating nano-hydroxyapatite and human adipose-derived MSCs for use as a bone filler in situ therapy

The use of hydrogels for tissue engineering and regenerative medicine has gained significant attention due to their biocompatibility, versatility, and ability to mimic the extracellular matrix of tissues. In this study, we investigated the potential of nano-hydroxyapatite (nHAp)-based hydrogels by using simply modified gelatin and hyaluronic acid for bone tissue engineering as means to use a 3D bioink with in situ manner. First, we confirmed the biocompatibility and cell proliferation rate of the hydrogels by encapsulating human adipose-derived stem cells (hASCs) within the hydrogel matrix. We observed that the addition of nHAp to the hydrogel matrix promoted cell proliferation and enhanced 3D cell organization. Next, we evaluated the osteogenic differentiation potential of hASCs-laden hydrogel through alkaline phosphatase (ALP) activity and alizarin red s staining. The results showed that the hydrogel-containing nHAp group had the highest ALP activity and mineralization, indicating its potential for inducing bone formation. In vivo studies using a rat subcutaneous implantation model and a rat calvarial defect model further confirmed the ability of nHAp-based hydrogels to promote bone formation. Overall, results demonstrate the potential of nHAp-based in situ hydrogels for bone tissue engineering, highlighting their potential as a promising 3D bioink material with enhanced bone regeneration.