Medicine & Science in Sports & Exercise:
B-13L Free Communication/Poster Bone and Connective Tissue
1Nippon Sport Science University, Tokyo, Japan
Although home exercise is being used for therapy and prevention of chronic orthopedic injuries in adult such as tendinosis, osteoarthritis and other conditions, the molecular mechanisms are still uncertain. Most such diseases involve the tendons, enthesis and articular cartilage where extracellular matrix is abundant. Although there have been many reports showing that exercise on a treadmill altered the expression of collagen mRNAs in rat skeletal muscles, such models do not well reflect the effects of chronic exercise. Relatively long-term voluntary wheel running (VWR) should provide some information about tissues adaptations to such exercise.
We examined the effects of four weeks of VWR on the expression of collagen I α2 chain (Colla2) mRNA in mature rat soleus muscle and Achilles tendon.
Eleven male Wistar rats (Age: 15wks) were assigned to two groups designated the exercise (N = 6) and control (N = 5) groups. Rats in the exercise group were caged in a running wheel (perimeter: 1 m) for four weeks. Controls were housed in rectangular cages (20 cm × 20 cm × 30 cm). After the experimental period, soleus muscle and Achilles tendon were isolated, weighed and rapidly frozen in liquid N2. Total RNA was extracted for Northern hybridization to evaluate the quantity of Colla2 mRNA. Digoxygenin-labeled 215 nt cRNA probe of rat Colla2 was designed (Accession No. AF121217, 2256–2470) for detection of the target mRNA.
During the four weeks experimental period, rats ran for 1.67 ± 6.6 km/day on average. Body weight in the exercise group (411.5 ± 34.2 g) was lower than that in the control group (431.4 ± 11.2 g). Respective tissue weights to body weight ratios of the soleus and Achilles tendon in the exercise group were higher than those in the control group. Although mRNA expression of Colla2 in the soleus muscles was almost same with that of control, a higher expression in the exercise group could be observed in Achilles tendon.
Chronic exercise appears to enhance active recruitment of collagenous proteins especially in tissues where chronic injuries frequently occur.