To investigate the feasibility of constructing self-crosslinked recombinant type Ⅰ collagen hydrogels and their role in repairing UV-induced photoaging models.

Recombinant collagen hydrogels were prepared by self-cross-linking using different concentrations of recombinant collagen at the Key Laboratory of Degradable Biomedical Materials of Shaanxi Province, Northwestern University, from July 2021 to December 2022, and the pore size distribution, swelling properties, rheological properties and pushing force of the hydrogels were examined by scanning electron microscopy (SEM), swelling test, rheometer, and universal material testing machine. The hydrogel biocompatibility was analyzed by MTT method and haemolysis test. A photoaging model of human skin fibroblast cells was established, and and the expression levels of inflammatory factors and genes related to ECM generation and degradation were detected by RT-qPCR. A UV-irradiated mice photoaging model was established to evaluate the effect of hydrogel on photoaging by gross observation, and the histocompatibility and degradation of hydrogel were observed by HE staining, and the mechanism of hydrogel action was investigated by RT-qPCR and immunofluorescence staining.

The GEL-Ⅰ hydrogels at 4 g/ml, 20 mg/ml and 40 mg/ml showed good physico-mechanical properties. Biocompatibility studies showed that the cell survival rate of different concentrations of hydrogels was greater than 100%, with pro-cell proliferative effects, and positively correlated with the concentration of recombinant collagen type Ⅰ. The hemolysis rate of the three groups of hydrogels was less than 5%. qPCR showed that in the HSF photo-aging model, compared with the model group, the three concentrations of hydrogel group cells in the Bcl-2 and TGF-β1 were significantly elevated (P<0.005), Caspase-3 and Caspase-9 (P<0.05), and Caspase-3 and Caspase-9 (P<0.05), respectively. Caspase-3 and Caspase-9 were significantly down-regulated (P<0.05), and the degree of apoptosis was significantly reduced; the level of MMP-9 gene was down-regulated (P<0.05), and Col-Ⅰ, Col-Ⅲ, and vimentin genes were significantly up-regulated (P<0.05). In the photoaging mouse model, less wrinkles were formed in the skin of mice in the hydrogel group compared with the model group; HE staining showed abundant and tight expression of collagen fibers and smoother stratum corneum; compared with the model group, GEL-Ⅰ could better reduce the ROS content, increase the SOD activity, and reduce the expression of MDA (P<0.05) with a concentration-dependent manner, and the ROS, SOD, and MDA levels were significantly up-regulated in the 40 mg/ml group compared with the control group (P<0.05), while the ROS and SOD levels of the 40 mg/ml group compared with the control group were significantly up-regulated. ROS and SOD levels were significantly different compared with the control group (P<0.05); Wolf scarlet staining showed that the collagen content in the tissue of the hydrogel group was significantly increased (P<0.05), and the collagen content in the 40 mg/ml group was significantly increased compared with the control group (P<0.05); immunofluorescent staining showed that the contents of TNF-α, IL-6 and MMP-9 decreased significantly (P<0.05) in a concentration-dependent manner.

The recombinant type Ⅰ collagen hydrogel could improve the oxidative stress and inflammatory microenvironment, reduce ROS in skin tissue, down-regulate HSF necrosis cell factors and matrix metallopeptidase 9, promote the functional recovery of skin photoaging cells and enhance the expression of ECM components, which can effectively improve photodamaged skin.

Light; Skin aging; Recombinant type Ⅰ collagen; Reduce inflammation; Skin photoaging repair; Matrix metallopeptidase 9; Extracellular matrix