Expression of matricellular proteins in human uterine leiomyomas and normal myometrium

Growth of human leiomyomas can probably be initiated as a response to injury, in a way similar to the development of keloids. Among many bioactive molecules, which are implicated in tissue repair, a pivotal role is attributed to matricellular proteins. The aim of the current study was to evaluate the immunohistochemical expression of tenascin-C (TNC), thrombospondin-1 (TSP-1), SPARC/osteonectin and tenascin-X (TNX) in human uterine leiomyomas and normal myometrium. Immunostaining was performed on 33 pairs of paraffin-fixed sections and 9 cell-lines derived from uterine leiomyomas and normal myometrium. Fifteen (45.5%) leiomyomas investigated were positive for TNC, whereas all normal myometrial samples were immunonegative (χ²=19.41; p<0.001). Immunostaining for TSP-1 was observed in 20 (60.6%) uterine fibroids and in 12 (36.4%) control samples (χ²=3.88; p<0.05). The expression of SPARC/osteonectin protein was more frequently found in leiomyomas than in normal myometrium, but this difference was not significant. Apart from one fibroid culture and one myometrial culture, all the others revealed strong TNC immunostaining. Expression of TSP-1 and SPARC/osteonectin was weak to moderate in all established cell-lines. None of the tissues or cell lines investigated showed positive staining for TNX. In conclusion, TSP-1 and TNC are likely to play important roles in the pathogenesis of uterine leiomyomas, presumably affecting cell proliferation and/or extracellular matrix deposition.