Effects of repetitive motion on human fibroblasts

ALMEKINDERS, L. C., A. J. BANES, and C. A. BALLENGER. Effects of repetitive motion on human fibroblasts. Med. Sci. Sports Exerc., Vol. 25, No. 5, pp. 603–607, 1993. Repetitive motion injuries such as tendonitis are common sports injuries. However, few scientific studies are available on the effects of repetitive motion on mesenchymal cells and the presumed inflammatory response. This study used a new in vitro model to study the effects of repetitive motion. Human tendon fibroblasts were subcultured and plated on culture wells with flexible bottoms. The cells were repetitively stretched using a microprocessor-controlled pressure unit that causes a cyclic deformation of the flexible bottom. The wells were divided in the following groups: group I controls without repetitive motion, group IIA repetitive motion with 0.25 strain at 0.17 Hz (10 cyclesμmin-1), group IIB repetive motion with 0.25 strain and 0.17 Hz in presence of 25 μM indomethacin, and group III repetitive motion with 0.25 strain at 1 Hz (60 cycles·min-1). After 3 h of stimulation the supernatant fluids were harvested and evaluated for prostaglandin E2(PGE2), leukotriene B4 (LTB4), and lactate dehydrogenase (LDH). The results showed significantly (P < 0.001) increased levels of PGE2 in groups IIA (46.9 ± 4.7 pg·0.1 ml-1) and III (65.7±8.0 pg·0.1 ml-1). This represents a 1.3− and 1.8-fold increase, respectively, compared with the control group I (36.4±5.9 pg·0.1 ml-1). LTB4 was significantly (P < 0.001) elevated in the indomethacin-treated group IIB (45.0±11.0 pg·0.1 ml-1) compared with very low levels in all other groups. LDH was not significantly different in any of the experimental groups compared with the control group I. The results indicate that repetitive motion induces production of PGE2. However, once PGE2 production is blocked by indomethacin, a concomitant increase in LTB4 results. Microscopic evaluation revealed no significant effects from the repetitive stretching compared with nonstretched control cells.