| Objective To explore the repair effect and mechanism of RADA-16 self-assembling peptide hydrogel scaffolds loaded with TGF-β1 on cartilage damage in osteoarthritis, so as to provide a new strategy for cartilage regeneration. Methods Cartilage tissues were collected from 8 elderly patients with severe knee osteoarthritis during knee arthroplasty, and 30 cartilage rings were obtained. They were divided into experimental group (filled with TGF-β1-loaded RADA-16 hydrogel), control group (filled with pure RADA-16 hydrogel) and blank control group (without filling) using block randomization, with 10 samples in each group. The microstructure of hydrogels was observed by scanning electron microscope, and the sustained release profile of TGF-β1 was detected by ELISA. CCK-8 assay and Calcein-AM/PI staining were adopted to evaluate the proliferation and viability of bone marrow mesenchymal stem cells (BMSCs). Toluidine blue and Sirius red staining were used to assess extracellular matrix synthesis, and immunofluorescence staining was performed to detect the expression of type Ⅱ collagen (Col-Ⅱ) and aggrecan. The mRNA expression of cartilage-specific genes was analyzed by qRT-PCR. HE staining and immunofluorescence staining were used to observe the repair of cartilage rings. Results The fibers of TGF-β1-loaded RADA-16 hydrogel were denser, with a fiber diameter of 20–60 nm and pore size of 30–150 nm; its specific surface area increased by 23.6% (P<0.05), showing a biphasic drug release pattern. The cell survival rate in the experimental group was 110.4%±4.0% on day 14, which was significantly higher than that in the control group (P<0.05). The positive area of toluidine blue staining was 5200±320 pixels on day 28, presenting a time-dependent increase, along with denser collagen fibers. On day 14, the mRNA levels of Col2, aggrecan and SOX-9 in the experimental group were higher than those in the control group (P<0.05). On day 28, a large number of neocartilage was found in the defective area of cartilage rings in the experimental group. The toluidine blue positive area reached 78.5%±6.3% (P＜0.001), and the fluorescence intensities of aggrecan and Col2 were significantly elevated (P＜0.01). Conclusion RADA-16 self-assembling hydrogel scaffolds loaded with TGF-β1 can promote the proliferation and chondrogenic differentiation of BMSCs via sustained release of TGF-β1, and markedly enhance extracellular matrix synthesis. It exerts a favorable repair effect on osteoarthritic cartilage damage, and is a promising biomaterial for clinical cartilage regeneration therapy. |