Are stem cells involved in the development of experimental pituitary adenomas? Our evidences say yes

GUIDO, C; SOSA L DEL V.; ZLOCOWSKI N; PEREZ P; MOYANO CRESPO G D; GUTIÉRREZ, S; PETITI J P; MUKDSI, J. H.; TORRES, A I

Workshop; EMBO Workshop, Molecular mechanisms of developmental and regenerative biology; 2018

The presence of stem cells (SC) has been described in the adult pituitary. They reside in a microenvironment (niche) generated by mesenchymal cells forming a functional unit that regulates cellular signals leading self-renewal or differentiation. The interaction between the SC and the niche influences the balance between symmetric and asymmetric divisions, a dysregulation could cause the development of a tumor. Little is known about tumor stem cells (TSC) in pituitary adenomas, being of interest the identification of biomarkers involved in the induction and progression of pituitary adenomas. They could provide important information regarding tumor cells behaviour and the degree of proliferation of therapeutic implications. The aim of this study was to evaluate possible changes in the expression of SC: GFRa2, OCT4, SOX2, NESTIN, Progenitor (P): SOX9, and CSC: CD133 and CD44 markers, during experimental pituitary tumor development, and later characterization of the SC in culture. The experimental model was performed in female Fischer rats, treated with 30 mg of estradiol benzoate during 5 (5d), 10 (10d), 20 (20d) or 30 (30d) days. The control group (C) included rats in diestrous. SC/P and CSC markers were detected by immunofluorescence (IF) and Western Blot (WB). The marginal zone (ZM), the main niche of SC in the adult pituitary gland, presented cells with apical extensions, such as cilia, oriented towards the pituitary cleft. Besides, two cell layers were visualized, one bordering the cleft and another below it identified as support cells. The SC and CSC markers, Oct4, Sox2, GFRa2, Nestin and CD133 showed variations in their distribution within the gland in the different experimental groups. We observed positive cells for these markers in MZ and less immunostaining in adenoparenchyma (AP) of C and 5d rats. In contrast, at 30d the expression of the markers decreased in MZ and increased in AP, indicating a reorganization of SC niche. GFRa2, Nestin, CD133 and CD44 expression levels increased significantly in 5d compared to C. The transcription factor Sox2 expression levels did not show variations during the estradiol benzoate treatment, while the expression of Sox9 decreased in 5d. Additionally, SC from 30d were isolated as pituispheres in vitro and they exhibited heterogeneous cellular composition including epithelial cells and others with mesenchymal phenotype. The pituispheres in culture were positive for SC and CSC markers. And a significant increase of proliferation was observed in spheres obtained from 5d and 30d vs. C (p