Physical exercise affects cell proliferation in lumbar intervertebral disc regions in rats.

Abstract

Descriptive experimental study. The aim of this study was to investigate the effect of exercise on cell proliferation in different areas of the intervertebral disc (IVD) and recruitment of cells possibly active in regeneration of normal rat lumbar IVDs. Little is known about the effects of physical exercise on lumbar IVD tissue. Recently, stem cell niches in the perichondrium area of the IVD were identified and cells in these niches have been suggested to be involved in the normal regeneration of the IVD. Thirty Sprague-Dawley rats were exposed to 5-bromo-2-deoxyuridine (BrdU) diluted in the drinking water during 14 days. Fifteen rats ran on a treadmill daily for 50 min/d, 5 d/wk (exercise group), and 15 nonexercised rats served as controls. Immunohistochemical analyses (anti-BrdU antibody) were performed at 9, 14, 28, 56, and 105 days after the start of the exercise protocol. BrdU positive cells were counted in the stem cell niche area, the peripheral region of epiphyseal cartilage area, and the annulus fibrous outer and inner areas. Data were analyzed by 2-way analysis of variance (significance level; P < 0.05). The BrdU positive cell numbers in the stem cell niche and annulus fibrous outer regions were increased in discs from the exercising group on days 14 (P < 0.01) and 105 (P < 0.05) and at day 14 (P < 0.01) in the peripheral epiphyseal cartilage region compared with controls. Physical exercise was shown to have positive effects on cell proliferation in IVDs, with involvement of various disc regions, indicating a differential response by disc tissue to exercise depending on anatomical location and tissue characteristics.