Alpha-smooth muscle actin expression in intact and ruptured human anterior cruciate ligament--an immunohistochemical assessment

The objective of this work was to evaluate the distribution of alpha-smooth muscle actin cells in the intact human anterior cruciate ligament and to determine if rupture of the anterior cruciate ligament and the time since injury has any influence on the occurrence of cells with contractile capability, positively stained for a-smooth muscle actin. The intact anterior cruciate ligament group (group A) undergoing total knee arthroplasty, consisted of 9 patients (8 females) with mean age of 65.3 years. The anterior cruciate ligament rupture group (group B) consisted of 20 patients (18 males, 2 females) with mean age of 27.8 years. Healing time of the torn ligament in vivo lasted from 1 to 40 months and the patients were divided into 3 groups (Bi-Biii) embracing diverse time periods. All harvested anterior cruciate ligaments were sectioned in thirds so that there was a proximal, middle and distal third for each ligament. Distribution of alpha-smooth muscle actin was detected with mouse monoclonal anti-human smooth muscle actin antibody. The alpha-SMA cells density was significantly affected by the time after injury as well as the location in the ligament remnant. The decrease of alpha-smooth muscle actin cells in the proximal and middle thirds of the ligament after rupture may suggest that alpha-SMA cells are not mainly responsible for primary retraction of the ruptured human anterior cruciate ligament.