Expression and localisation of osteopontin and prominin-1 (CD133) in patients with endometriosis

Abstract

In this study, we investigated the expression and localisation of the proteins, osteopontin (OPN) and prominin-1 (CD133), as well as the plasma OPN levels in the endometrium of patients with endometriosis. Samples of ectopic endometriotic lesions and normal endometrium were obtained from 31 women with endometriosis and 28 healthy control subjects. The mRNA and protein expression of OPN and CD133 was analysed by real‑time RT-PCR and immunohistochemistry. The plasma levels of OPN were determined by ELISA. Our results revealed that OPN mRNA and protein expression, as well as its release in the blood, was significantly increased in the endometriotic lesions in comparison to normal tissue. Although the presence of CD133+ cells was detected in the normal endometrium, as well as in the endometriosis specimens, a significant quantitative variation of this protein was not demonstrated in the patients with endometriosis. In conclusion, our data indicate that OPN is involved in the development of endometriosis by enhancing the invasiveness, proliferation and survival of endometrial cells in ectopic lesions. CD133 cannot be used as a disease marker for endometriosis, although an involvement of this protein in the pathogenesis of endometriosis cannot be excluded.

Figure 1

Real-time RT-PCR analysis of osteopontin (OPN) and CD133 mRNA expression in the ectopic (endometriotic) and eutopic (control) endometrium. (A) OPN mRNA expression was significantly higher in patients with endometriosis in comparison to the control subjects. (B) Although CD133 expression was slightly higher in the patients with endometriosis in comparison to the control subjects, the difference was not statistically significant (^*p<0.01).

Figure 2

Plasma osteopontin levels in women with endometriosis and control subjects. The mean plasma osteopontin levels were higher in the patients with endometriosis compared to the control group (^*p<0.01).

Figure 3

Representative micrographs of immunohistochemistry of osteopontin (OPN) and CD133 expression in the eutopic normal endometrium and endometriotic lesions. (a) In normal tissue, OPN was exclusively immunolocalised in the cytoplasm of epithelium of the functional layer. (b) In endometriotic tissue (stage III-IV), OPN expression was higher in comparison to the control samples, and its localisation was restricted to the cytoplasm of epithelial gland cells, as well as to the macrophages in the stroma. (c) In the control tissue, the surface of epithelial cells lining the lumen was immunostained for CD133. (d) The immunohistochemical pattern for CD133 in endometriotic tissue (stage III-IV) was similar to that obtained in control tissue (bars: a, 80; b, 80; c, 90; and d, 80 μm).