Ovariectomy (OVX) induces profound changes in the pituitary TGFβ1 system and some components of the extracellular matrix, predisposing the gland to a proliferative phenotype

MARÍA ANDREA CAMILLETTI; ERIKA FARAONI; ABELEDO ALEJANDRA; MARÍA CECILIA BOTTINO; DÍAZ DE TORGA, GRACIELA

Congreso; ENDO 2016; 2016

Endocrine Society

TGFβ1 is a potent cytokine expressed in pituitary lactotrophs, and we have previously demonstrated that alterations in the pituitary TGFβ1 system are involved in the development of a prolactinoma (1-2). A well-known model of experimental prolactinoma is a chronic treatment with estrogens in rats. We have recently found that those prolactinomas are larger when the animals (adult female Sprague Dawley rats) were OVX, previously to the treatment (20mg sc diethylstilbestrol, 4 weeks, (DES)). In this work we have studied the disorders induced by the OVX, in the pituitary TGFβ1 system. We observed that OVX caused a drastic decrease in the biological activity of TGFβ1 in the pituitary gland (pSmad2/3 measured by western blot, 137,4±21,2 a.u. in control vs 29,2±11,2 in OVX, N: 8, 10). This fact would be involved in the development of larger prolactinomas induced by estradiol in OVX group. However, we did not find alterations in pituitary active TGFβ1 levels among groups (measured by ELISA). We also found the levels of the TGFβ1 receptors (TßRII, ALK1, ALK5 by qRT-PCR) increased, and even the cytokine mRNA in pituitaries from OVX group (TGFβ1 mRNA: 1,02±0,076 a.u. in controls vs 2,62±0,302 in OVX, N: 8, 10). Why the higher expression of all the components of the pituitary TGFβ1 system found in pituitaries from OVX females is not reflected in an increased biological activity of the cytokine? It was described that decorin and biglycan (small leucine-rich proteoglycans) are capable of sequestering TGFβ1 within the extracellular matrix, neutralizing its activity (3). We evaluated the expression of these compounds (by RT-qPCR) and observed a significant increase of both of them in OVX pituitaries: decorin: 1,01±0,106 a.u. in control vs. 2,42±0,272 in OVX, and biglycan: 1,00±0,052 a.u. in control vs. 2,07±0,098 in OVX. Finally, we demonstrated that both proteoglycans are increased in pituitaries from OVX group because they are negatively regulated by estradiol. We assayed an E2 valerate treatment: 0.2mg / kg, sc, 1, 2 and 24h. Decorin mRNA decreased from 1,01±0,093 a.u. in control to 0,47±0,099 with E2 24hs; Biglycan mRNA decreased from 1,03±0,150 a.u. in control to 0,54±0,039 in E2 24hs. We conclude that OVX causes a drastic decrease in the biological activity of pituitary TGFβ1, determining a pituitary proliferative environment to the steroid action. This was not due to a low expression of the local TGFβ1 system, but probably due to the sequestration of the active cytokine in the extracellular matrix by increased levels of decorin and biglycan in pituitaries from the OVX females.