Abstract:

Objective To study the effect of chronic sleep deprivation(CSD) on the expression of the transforming growth factor β1(TGF-β1) in condylar cartilage of rats.

Methods A total of 60 male Wistar rats were randomly divided into three groups, the experimental group, the control group and the recovery group. The modified multiple platforms method(MMPM) was used to build the CSD of rats in the experimental and recovery group. Open field test was performed to evaluate the effect of sleep deprivation model of rats. At the end of the 1, 2, 3 and 4 week of sleep deprivation, 5 rats in the experimental group and the control group were sacrificed respectively. The rats in recovery group received 1 week of cage feeding after sleep deprivation to recover the sleep, and then were sacrificed. Subsequently, bilateral temporomandibular joints were obtained. HE staining was used to observe morphological changes in the condyle of temporomandibular joint. And the immunohistochemistry was performed to detect the changes of TGF-β1 in condylar cartilage.

Results The rat model of CSD was successfully established by the MMPM, and the rat was in a state of stress. HE staining showed no significant  change in the condyle of rats in the control group. In the experimental group, there were some degenerative pathological changes like fissures and fractures in the superficial fibers of the condyle of the rats, unclear cell boundaries, and ingrowth of subchondral bone into the cartilage layer. Compared with the rats in the experimental group, the control group showed increased fissures of the fibrous band on the condylar surface of the rats, more layers of local mast cells, and clearer cell boundaries of each layer. The immunohistochemistry showed that the TGF-β1 was mainly expressed in the cells of the proliferative layer of condylar cartilage and mast cells of the fibrocartilage layer. There were no obvious changes in TGF-β1 expression in the control group at different time points, which, however, was increased in the experimental group with the prolonged CSD, suggesting significant differences between two groups(P＜0.05). In the recovery group, TGF-β1 expression was slightly decreased compared with the experimental group, and there was significant difference(P＜0.05). At 1 week after CSD, no significant difference was found between the recovery group and the control group(P＞0.05). However, at 2, 3, and 4 weeks after CSD, TGF-β1 expression was higher in the recovery group than in the control group, and the difference was statistically significant(P＜0.05).

Conclusion CSD can cause stress in rats, leading to degenerative changes in condylar cartilage, and increased TGF-β1 expression in condylar cartilage. TGF-β1 expression increases with prolonged sleep deprivation. In addition, sleep recovery can induce the decrease of TGF-β1 expression.

Key words:

sleep deprivation, transforming growth factor β1, condylar cartilage