Development and assessment of a novel silk fibroin methacrylate and keratin hydrogel for human hip acetabular labrum regeneration

The acetabular labrum is a fibrocartilaginous ring that surrounds the acetabular rim, anchoring to bone and ensuring hip joint stability and sealing. It is mainly composed of fibrochondrocytes and type I collagen fibers, providing resistance to mechanical stress during daily activities. Femoroacetabular impingement can compromise these properties, leading to labral degeneration, hip pain, reduced quality of life, and early osteoarthritis. To address this, biomaterials that mimic the native labral and support regeneration are under investigation. This study developed composite hydrogels combining, for the first time, Bombyx mori -derived silk fibroin methacrylate (SilMA) and wool-derived keratin microfibers (KI) to create a bioartificial labrum prototype. Two KI concentrations (12.5% and 25% w /w), mixed with SilMA, were tested and compared to SilMA alone. KI powder was dispersed into SilMA, and ultraviolet (UV) exposure time was optimized for hydrogel crosslinking. Morphological and mechanical characterization of the hydrogels was performed, along with the evaluation of cell biocompatibility and cell behavior with human chondrocytes (C28/I2) using a lactate dehydrogenase assay, transmission electron microscopy, and histology. Increasing KI concentration enhanced viscosity, shear stiffness, and elastic modulus under dry and wet conditions. Biocompatibility assays confirmed cell viability up to 14 days. Overall, SilMA-KI hydrogels demonstrated favorable mechanical performance and cytocompatibility, highlighting their potential as scaffolds for acetabular labrum regeneration.