Abstract
This study aimed to investigate the molecular pathways involved in muscle wasting in an animal model of osteoarthritis (OA) induced by anterior cruciate ligament transection (ACLT) in rats. Reduction of protein syntheses, increased proteolysis and impaired muscle regeneration are important pathways related to muscle wasting, and myogenin, MyoD, myostatin and MuRF-1 are some of their markers. Female Wistar rats were allocated into two groups: OA (submitted to the ACLT) and SHAM (submitted to surgery without ACLT). Nociception, spontaneous exploratory locomotion and body weight of animals were evaluated weekly. Twelve weeks after the disease induction, animals were euthanized, and the right knee joints were collected. Gastrocnemius muscle of the right hind paw were dissected and weighed. Gastrocnemius was used for evaluation of muscle atrophy and expression of IL-1β, TNF-α, Pax7, myogenin, MyoD, myostatin and MuRF-1. Histopathology of the knee confirmed the development of the disease in animals of OA group. Gastrocnemius of OA animals showed a reduction of about 10% in area and an increased IL-1β expression compared to animals of SHAM group. Expression of myostatin was increased in OA group, while myogenin expression was decreased. TNF-α, Pax7, MuRF-1 and MyoD expression was similar in both OA and SHAM groups. Nociception was significantly elevated in OA animals in the last two weeks of experimental period. Spontaneous exploratory locomotion, body weight and weight of gastrocnemius showed no difference between OA and SHAM groups. Gastrocnemius atrophy in OA induced by ACLT involves elevated expression of IL-1β within the muscle, as well as increased expression of myostatin and decreased expression of myogenin. Therefore, muscle wasting may be linked to impaired muscle regeneration.
Highlights
Osteoarthritis (OA) is a chronic disease characterized by abnormal remodeling of joint tissues driven by inflammatory mediators within the affected joint
The nociception of the right hind paw was significantly increased in animals of OA group in the last two weeks of the experimental period, compared to animals from SHAM group (p = 0.0011; Fig 2A)
The results of this study provide new information about the molecular pathways involved in muscle wasting in a rat model of OA induced by anterior cruciate ligament transection (ACLT)
Summary
Osteoarthritis (OA) is a chronic disease characterized by abnormal remodeling of joint tissues driven by inflammatory mediators within the affected joint. The main sign of OA is the progressive degradation of articular cartilage, but changes in muscles surrounding the affected joint can be present [1]. In OA that affects lower limbs, muscle weakness is a common feature. Muscle weakness is related with the progression of OA, since the muscle strength in the lower limbs seems to decrease as the severity of the disease increases [6,7,8]. Muscle weakness in patients with OA is often associated with atrophy of muscle fibers [8, 9] In this context studies report that there is a reduction of 12– 19% in the cross-sectional area (CSA) of muscles from the affected limb in patients with hip and knee OA [9,10,11])
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