Expression of the gap junction connexins Cx43, Cx45 and Cx26 in human uterine leiomyomata.

Uterine leiomyomata of 34 premenopausal women undergoing leiomyomectomy or hysterectomy, and in four cases the corresponding myometrium, were collected at laparotomy or laparoscopy to investigate the ability of these benign smooth muscle cell tumors to express different connexins. Immunohistochemical and Northern blot analyses were performed for the characterization of the expression of connexins Cx43, Cx45, Cx26 and Cx32. Immunofluorescence revealed the presence of Cx43 in most leiomyomata. Only seven leiomyomata lacked Cx43 expression. Cx45 was expressed in 13, a weak Cx26 immunostaining was found in seven cases, whereas Cx32 could not be detected. No correlations between the 17 beta-estradiol or progesterone serum levels and the expression patterns of the connexins Cx43, Cx45 and Cx26 could be observed. Gonadotropin-releasing hormone (GnRH)-agonist or progestin treatment did not influence the connexin expression pattern. Northern blot analyses confirmed these results; however, transcripts of Cx26 were not detectable. Connexin transcripts between myomata and the corresponding myometrium showed no obvious differences. Our data show that uterine leiomyomata are capable of expressing different connexins comparable to the corresponding myometrium, but do not respond to different hormonal conditions. The ability to express the appropriate connexins could explain why these tumors, though developing independently of hormonal levels, are still differentiated benign smooth muscle tumors.