[Histological and biochemical studies of collagen in human uterine leiomyomas]

Forty eight human uteri including normal group (16 cases), adenomyosis group (5 cases) and myoma group (27 cases) were studied to clarify the pathogenesis of uterine leiomyomas on the viewpoint of the collagen metabolism. The leiomyomas in the myoma group were histologically divided into the three types; cellular leiomyoma type (7 cases), fibromyoma type (14 cases) and hyaline degeneration type (6 cases). After collagen contents were determined, collagen molecules were extracted and purified, then they were examined by the techniques of SDS-polyacrylamide gel electrophoresis and amino acid analysis. The results were as follows: The collagen content of the myoma group (62.3 +/- 2.7%, mean +/- S.E.) was higher than those of the normal group (48.5 +/-3.2%) and the adenomyosis group (52.0 +/- 5.2%) (P less than 0.05), and it was consistent with the histological collagen amount in the three types of the myoma group respectively. The normal group, the adenomyosis group and the myoma group contained mainly type I collagen [alpha 1 (I)2 alpha 2] and a little type III collagen [alpha 1 (III)3], but alpha 1(III)/alpha 1(I) ratio decreased in order of the normal group (20.6 +/- 0.3%), the adenomyosis group (16.4 +/- 0.2%) and the myoma group (12.9 +/- 0.4%); the cellular leiomyoma type (15.8 +/- 0.2%), the fibromyoma type (12.4 +/- 0.2%) and the hyaline degeneration type (10.5 +/- 0.6%) (P less than 0.001). Decrease of the type III collagen was related to decrease of the tissue elasticity and increase of the tissue firmness. Though hydroxylation ratio of proline showed no remarkable change, hydroxylation ratio of lysine in the myoma group (26.8 +/- 0.5%) was higher than those in the normal group (23.4 +/- 0.4%) (P less than 0.001) and the adenomyosis group (24.3 +/- 0.9%) (P less than 0.05). In the three types of myoma group, its ratio of the cellular leiomyoma type (28.8 +/- 1.1%) was higher than that of the fibromyoma type (25.8 +/- 0.5%) (P less than 0.05). This suggests that intermolecular, rather than intramolecular, cross-linking formation was accelerated in the collagen metabolism of uterine leiomyomas. In conclusion, it was suspected that these abnormalities in the collagen metabolism led to the development of the uterine leiomyoma.