GHK-Cu grafted polypeptide microspheres boost osteogenesis and angiogenesis for bone defect repair

Repairing irregular bone defects remains a significant challenge in orthopedic surgery, often limited by the poor integration and insufficient bioactivity of conventional scaffolds. Current approaches struggle to simultaneously promote both osteogenesis (bone formation) and angiogenesis (blood vessel formation), which are critical for effective bone regeneration. Biomimetic scaffolds that mimic the extracellular matrix (ECM) and possess dual osteoinductive and pro-angiogenic properties are highly sought after. The copper peptide GHK-Cu is recognized for its regenerative potential, making it an attractive candidate for functionalizing such biomaterials.

Researchers fabricated asymmetric open-hollow nanofibrous microspheres (HNMs) from poly(γ-benzyl-L-glutamate) (PBLG) using emulsion and thermally induced phase separation. Subsequently, GHK-Cu was covalently grafted onto these microspheres to create PBLG-GCu HNMs. The optimized microspheres had an average diameter of 372 ± 102 μm and an opening size of 219 ± 53 μm, with internal nanofiber diameters of 417 ± 78 nm. They assessed cytocompatibility using Live/Dead staining and CCK-8 assays. Osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) was evaluated by mineralization and qPCR for gene expression, while angiogenic potential was measured via a tube formation assay.

The PBLG-GCu HNMs demonstrated excellent cytocompatibility, confirming their safety for cellular interaction. Compared to non-functionalized PBLG HNMs, the GHK-Cu grafted microspheres significantly enhanced BMSC mineralization. Furthermore, they robustly upregulated key osteogenic gene expression: Runx2 expression increased by 1.61-fold, OPN (osteopontin) by 3.53-fold, and OCN (osteocalcin) by 2.29-fold.

The most significant finding was the 3.53-fold increase in OPN expression, a critical marker for bone matrix maturation, indicating potent osteoinductive capabilities. Beyond osteogenesis, the tube formation assay confirmed that PBLG-GCu HNMs provided robust angiogenic stimulation, crucial for vascularizing new bone tissue. These results highlight the successful integration of hierarchical structural biomimicry with dual bioactivity.