Fig. 4

Histological and biochemical analyses were used to evaluate the protective and restorative effects of microsphere treatment on the cartilage of OA rats. Typical images of knee joints. Histological staining was performed at 4 and 12 weeks after surgery. a HE staining demonstrates a clear boundary between the cartilage and subchondral layer; b Safranin-O Fast Green staining demonstrates cartilage matrix and chondrocyte plasma (stained red), and muscle, collagen fibers, and bone tissue (stained gray-green); c II collagen staining demonstrates gray-black small particles which represent type II collagen fibers; d Chondrocyte proteoglycan staining demonstrates gray-black small particles which represent proteoglycans; e OARSI histological scoring of the cartilage at 4 and 12 weeks after surgery. (Control group: Joint cavity was surgically accessed without any procedure done; L0: L0 microspheres injected after the ACLT and DMM procedures; L1, L1 microspheres injected after the ACLT and DMM procedures; L2, L2 microspheres injected after the ACLT and DMM procedures; Normal saline group: normal saline microspheres injected after the ACLT and DMM procedures)