The effect of exercise training and injection Mesenchymal Stem Cells on gene expression of Beclin-1, Mir-155 and mTOR of articular cartilage tissue in rats model of osteoarthritis

Arthritis defines a large group of diseases primarily affecting the joint. It is the leading cause of pain and disability in adults. Osteoarthritis affecting the knee or hip is the most common form among over 100 types of arthritis and chronic degenerative disease of articular cartilage and the most common type of arthritis. The purpose of the study was to explain the effect of eight weeks of moderate intensity aerobic exercise and mesenchymal stem cell injection (MSCs) on the expression of Beclin-1, Mir-155 and mTOR genes in damaged cartilage tissue in rats with knee osteoarthritis.

In the experimental study, 35 adult male Wistar rats (mean weight 210±10g) were randomly divided into five healthy groups: osteoarthritis, osteoarthritis+ aerobic exercise, osteoarthritis+ mesenchymal stem cells and osteoarthritis+ exercise group. Aerobic+ mesenchymal stem cells were divided. Osteoarthritis was surgically treated. Exercise consisted of running on a treadmill for eight weeks, five sessions per week, each session lasting 35-45 minutes at a speed of 18 meters per minute. The mesenchymal stem cell group received 1 6 106 mesenchymal stem cells per kg by intra-articular injection of the knee. 48 hours after the last training session and at 12 hours of fasting, knee cartilage samples were isolated and the expression of Mir-155, Beclin-1 and mTOR genes measured by R-T PCR.

The results of the study showed that there is a significant difference between the effect of training and injection of mesenchymal stem cells on Beclin-1mRNA levels (P ˂ 0.001). The results also showed that there was a significant difference between OA group and healthy control groups (P=0.008), MSCs+ OA (P=0.009), exercise+ OA (P=0.001) and MSCs+ exercise+ OA (P=0.001). Also, there was a significant difference between exercise+ OA group (P=0.008) and MSCs+ exercise+ OA (P=0.002) and MSCs+ OA group. However, there was no significant difference between exercise+ OA and MSCs+ exercise+ OA groups (P>0.05). In the present study, it was found that there was a significant difference between groups in the expression of miR-155 groups (P<0.001). Also, the difference between OA group and three groups of exercise+ OA (P=0.002), MSCs+ OA (P=0.001), exercise+ MSCs+ OA (P=0.003) was significant. On the other hand, there was a significant difference between exercise+ MSCs+ OA and MSCs+ OA group (P=0.008). However, there was no significant difference between the two groups of exercise+ OA and MSCs+ OA (P>0.05). The results showed that there was a significant difference between the mean mTOR and mRNA expression of the groups (P<0.001). Also, there was a significant difference between OA group and healthy control groups (P=0.001), MSCs+ OA (P=0.014), exercise+ OA (P=0.021) and MSCs+ exercise+ OA (P=0.003). Also, there was a significant difference between MSCs+ OA group (P=0.022) and MSCs+ OA (P=0.002). However, there was no significant difference between OA+ training groups and MSCs+ OA (P>0.05).

The results of the present study showed that beclin-1 expression is one of the signs of differences between healthy chondrocytes and osteoarthritis. Decreased expression of Beclin-1 may be associated with decreased autophagy, mitochondrial damage and chondrocyte apoptosis. However, a mild intensity exercise training period was associated with increased expression of Beclin-1. In line with the findings of the present study, Zhang et al. (2019) showed that four weeks of running on treadmill at a gentle speed of 18 m/min increased the expression of beclin-1 factor mRNA in chondrocytes of osteoarthritis model mice. Another finding of this study was to increase the expression of beclin-1 factor mRNA by mesenchymal stem cell injection. It should be noted that due to the essential role of Beclin-1 in autophagy and being on the axis of accumulation of proteins involved in autophagy in the membranes of autophagy system, increasing changes in Beclin-1 levels with mesenchymal stem cells indicate an increase in autophagy activity in cartilage tissues and chondrocytes. Cell culture media studies showed that optimal level of autophagy maintains stem cell function and strengthens autophagy activation, differentiation and triggering of stem cell signals. In addition, strengthening the autophagy system also prevents stem cell apoptosis. It was also reported that stem cell migration is affected by autophagy and low hand regulation of Beclin-1 is associated with increased levels of caspase-3 and stem cell apoptosis. In the present study, the progression of knee osteoarthritis was associated with an increase in the expression of MIR-155. However, aerobic training and stem cell injection were associated with decreased expression of MIR-155. The present study is the district research to investigate the effect of aerobic training and stem cells on mir-155 expression. However, in recent years, some studies with different methodology have investigated mesenchymal stem cell interactions, inflammation and MIR-155 and pointed to the role of oxygen free radicals (ROS). Therefore, in the present study, the status of apoptosis and its markers were not measured; reducing the expression of this factor with mesenchymal stem cell and aerobic training may stop the expression of pre-apoptotic proteins. Another finding of the present study showed that osteoarthritis increased mTORmRNA levels of articular cartilage. This can be indirectly related to lack of optimal autophagy control and progression of apoptosis in chondrocytes. In line with this finding, Ying et al. (2015) showed an increase in the expression of mTORmRNA chondrocytes despite osteoarthritis in human, mouse and dog cartilage, and exercise training used in the present study along with mesenchymal stem cell injection was effective in reducing mTORmRNA levels. Although complex-1 rapamycin (C1-mTOR) is the primary regulator of autophagy in mammals, overexpression of mTORmRNA along with beclin-1 reduction are signs of decreased autophagy capacity and aging. However, protein levels were not measured, the intensity of exercise was mild and moderate and its effects were observed in changing the expression of mTOR along with the increase of Beclin-1. This result may reflect the availability of the necessary ground for autophagy and its inhibition in chondrocytes. Application of moderate intensity training in osteoarthritis that promotes the growth and proliferation of chondrocytes. The progression of osteoarthritis is associated with profound changes in epigenetic control of gene expression and transcription factors, leading to certain changes in target gene expression in the joint tissue by changing the methylation status of the genome. Overall, the results of this study showed that a moderate-intensity training period, while increasing Beclin-1 levels, reduced the levels of MIR-155 and mTOR. However, in the present study, protein expression of molecules as well as levels of other autophagy factors such as ULK-1 and LC3 were not measured, which is one of the limitations of the present study. Therefore, it is suggested that people with osteoarthritis use moderate-intensity exercise training and stem cell to improve the expression of articular cartilage autophagy genes.