Abstract:

This study aimed to explore the effects of light disturbance and biological clock on osteoarthritis (OA) based on the relationship between the length of sunshine duration (SD) and osteoarthritis (OA) in dairy farms in different regions. By investigating the incidence of bone and joint diseases of lactation cows and local monthly SD in 11 regions across the country from July 2018 to June 2021, the correlation between its incidence and SD was analyzed through Pearson. At the same time, 64 SD male rats were randomly divided into N group (n=32) and OA group (n=32). The OA group used the method of anterior cruciate ligament cleavage (ACLT) to establish an early OA model, and N group performed sham surgery. Each group is divided into two subgroups, and two light-dark period regulation modes (normal light LD and disordered light illumination Dis-LD) are established, namely N+LD, N+Dis-LD, OA+LD and OA+Dis-LD groups, with 16 individual groups. The test cycle was 6 weeks, and the weight changes in rats were recorded, the levels of inflammatory factors and cartilage degradation markers were detected in rat serum, and the articular cartilage was stained with frairo O-solid green and OARSI scores were used to detect the levels of proteins related to cartilage metabolism in rats, and the effects of key biological clock proteins in the heart, liver, spleen, lung and kidney of OA rats were detected. Among the 11 regions surveyed, except for Yinchuan, the other 10 regions were positively correlated with SD, with 6 regions moderately positive correlation (0.4 < R² < 0.6) and 4 regions weakly correlated (0.2 < R² < 0.4). The results of rat experimental research showed that light disorders can significantly slow down the weight gain in rats, increase the content of proinflammatory factors (IL-1β, TNF-α, IL-6, iNOS) and cartilage degradation markers (COMP and CTX-Ⅱ) in rats, promote the catabolism of articular cartilage matrix (MMP-3, MMP-13, ADAMTS-4) in rats in OA group and reduce the synthesis of cartilage collagen fibers (COL2A1). The key biological clock proteins (BMAL1, NR1D1, CRY1 and PER3) in the heart, liver, spleen, lung and kidney of OA rats showed varying degrees. Epidemiological investigations revealed that the incidence of bone and joint diseases in dairy cows was significantly positively correlated with SD. Rat experiments showed that light disorders lead to abnormal biological clocks, promote pathological damage to the cartilage and accelerate the development of OA. This experiment revealed the significant impact of light changes on bone and joint diseases in mammals, and provided a reference for dairy farms to develop appropriate artificial light cycle plans to reduce the incidence of bone and joint diseases in dairy cows in the future.

Key words: light disturbance, biological clock, bone joint disease, sunshine duration, dairy cattle