Synchronized osteochondral regeneration using a dynamic sacrificial‑phase injectable macroporous PEO‑gelatin‑GelMA hydrogel delivering BMP‑14‑engineered BMSCs

Integrated osteochondral repair remains a clinical challenge because of the distinct regenerative requirements of avascular cartilage and underlying subchondral bone. However, a key research bottleneck is the lack of an injectable scaffold that can reduce diffusion barriers while providing sustained signals for both osteogenic and chondrogenic differentiation. To address this challenge, we engineered a highly interconnected macroporous hydrogel (PGG) through a dynamic sacrificial-phase strategy using polyethylene oxide (PEO) and gelatin as transient templates within a GelMA matrix—hereafter referred to as PGG. Post-injection, the gradual dissolution drives of these sacrificial templates from the PGG hydrogel matrix drives the in situ formation of a highly interconnected macroporous network. By modulating the component ratios, the architecture was optimized to yield the G1:2 formulation, with a pore size of approximately 91 μm and a compressive modulus of 85.5 ± 0.7 kPa, measured on day 1 in the hydrated state. To drive lineage-specific differentiation, the scaffold was loaded with lentivirally transduced bone marrow-derived stem cells overexpressing BMP-14 (oeBMP-14-BMSCs). In vitro, these ‘micro-biofactories’ provided sustained paracrine signaling for 15 days, demonstrating a unique dual-lineage potency by simultaneously upregulating both chondrogenic (SOX9, COL2A1) and osteogenic (RUNX2, ALP) markers. In a rat femoral trochlear model, the oeBMP-14-BMSC/PGG composite orchestrated the integrated restoration of the osteochondral unit. At 8 weeks, it facilitated superior subchondral bone remodeling, characterized by significantly higher bone volume/tissue volume (BV/TV) and bone mineral density (BMD), coupled with the formation of more organized hyaline-like repair tissue and increased type II collagen deposition. This dual-functional platform provides a promising experimental approach for coordinated osteochondral regeneration, although comprehensive long-term biosafety evaluation is required before clinical translation.