Effects of growth and exercise on composition, structural maturation and appearance of osteoarthritis in articular cartilage of hamsters

Abstract

Articular cartilage composition and structure are maintained and remodeled by chondrocytes under the influence of loading. Exercise-induced changes in the composition, structure, mechanical properties and tissue integrity of growing and aging hamster articular cartilage were investigated. Articular cartilage samples (n = 191) were harvested from the proximal tibiae of hamsters aged 1, 3, 6, 12 and 15 months. The hamsters were divided into runners and controls. The runners had free access to a running wheel between 1 and 3 months (runner groups 3-, 12-and 15-month-old hamsters) or 1 and 6 months (runner group 6-month-old hamsters) of age. Control animals were subjected to a sedentary lifestyle. Mechanical indentation tests and depth-wise compositional and structural analyses were performed for the cartilage samples. Furthermore, the integrity of articular cartilage was assessed using histological osteoarthritis grading. Exercise affected the collagen network organization after a 5-month exercise period, especially in the middle and deep zones. However, no effect on the mechanical properties was detected after exercise. Before the age of 12 months, the runners showed less osteoarthritis than the controls, whereas at 15 months of age the situation was reversed. It is concluded that, in hamsters, physical exercise at a young age enhances cartilage maturation and alters the depth-wise cartilage structure and composition. This may be considered beneficial. However, exercise at a young age demonstrated adverse effects on cartilage at a later age with a significant increase in the incidence of osteoarthritis.

Minor Influence of Lifelong Voluntary Exercise on Composition, Structure, and Incidence of Osteoarthritis in Tibial Articular Cartilage of Mice Compared with Major Effects Caused by Growth, Maturation, and Aging

“…Lifelong moderate and non-voluntary running exercise of C57BL mice between the ages of 2 and 18 months was shown to increase the incidence and severity of OA [19]. A similar trend was observed in hamsters with voluntary exercise only at a young age [8], but this phenomenon was more clearly evident in rats [24]. Earlier studies on the effects on lifelong exercise on growth and maturation have focused mainly on studying the incidence OA, and have not examined the compositional and structural changes in AC.…”

“…More specifically, in OA, the PGs of the superficial zone experience loss and the collagen fibril network in the surface-most cartilage becomes progressively disorganized [14][15][16][17]. Earlier findings have indicated that exercise may protect from OA, make the joint more prone to OA, or have no effect on the incidence of OA [8,[18][19][20][21][22]. Part of this controversy may be explained by variations in the amount of exercise and its duration, as well as the site investigated in the joint [16].…”

“…Hypothetically, the modification of cartilage composition due to exercise could protect the joint from OA during later periods of life [18,23]. Investigations of the simultaneous effects of aging and exercise on cartilage with different animal models have reported various types of outcomes [8,19,24]. Lifelong moderate and non-voluntary running exercise of C57BL mice between the ages of 2 and 18 months was shown to increase the incidence and severity of OA [19].…”

“…The composition and structure of AC is modified during growth and maturation due to remodeling of the AC matrix [2][3][4][5]. It has been reported that the cartilage remodeling is affected by external loading of the joints [6][7][8]. Remodeling can be considered an adaptation to joint loading conditions and demands, as it is known that the composition and structure of AC modulates the mechanical properties and thereby the function of AC [9][10][11][12].…”

“…Exercise-induced changes in AC composition and structure have been studied with several animal models [6,8,[18][19][20][25][26][27][28][29]. Different types of exercise routines have been applied.…”