AbstractThe spermatogonial stem cell (SSC) niche has an important regulatory function in spermatogenesis. The SSC niche consists of Sertoli cells, Leydig cells, myoid cells and blood vessels. Besides cells, the niche also contains testicular extracellular matrix (ECM) which is mainly produced by peritubular myoid cells and Sertoli cells. Damage to the testicular niche cells and ECM leads to disturbed fertility. This study aims to evaluate these damages effected by certain diseases and treatments characterized by fibrosis in the testes, loss of SSCs and consequently disturbed spermatogenesis.
Firstly, the effect of diseases (Klinefelter Syndrome (KS), Sertoli cell only (SCO) syndrome) and treatments (chemotherapy and hormone therapy) on the integrity of niche cells was investigated by immunohistochemistry using functional markers: Melanoma-associated antigen 4 (MAGE-A4) for SSC, inhibin b for Sertoli cells, Insulin-like factor 3 (INSL3) for Leydig cells and α-actin-2 (ACTA2) for myoid cells. Secondly, the specific ECM components were evaluated by immunohistochemistry using antibodies against major ECM building blocks including laminin, fibronectin, collagen I and collagen IV. These results were compared to fertile controls (FC).
Only patients treated with chemotherapy and patients with KS still had tubules with differentiation. All groups showed functional Sertoli cells in the seminiferous epithelium. Abnormalities to peritubular myoid cells were typical for all infertility groups. In patients with KS an increased density of Leydig cells was observed compared to FC. The highest density of Leydig cells was found in patients with SCO syndrome. Generally, tubules with differentiation in the different patient groups showed similar ECM staining patterns in the tubular wall compared to FC. In contrast, the tubules without differentiation generally had abnormal ECM patterns in the tubular wall. Specifically, fibronectin, laminin, collagen I and collagen IV showed irregular patterns in KS patients, SCO syndrome, chemotherapy treated patients and patients who received hormone therapy. Overexpression of certain ECM proteins could probably be due to the peritubular myoid cell impairment. ECM, which has a role in the regulation of spermatogenesis, is fibrotic, causing spermatogenesis disruption. Especially noticeable was the disappearance of laminin expression which is important for the attachment and function of Sertoli cells suggesting that disturbed spermatogenesis could be caused by Sertoli cell dysfunction. Finally, an increase in Leydig cell density could be an overcompensation mechanism to induce spermatogenesis.
A comparative evaluation of the alterations in the proteome of each group by mass spectrometric analyses and quantitative analysis of the known factors associated with inflammation and fibrosis by Enzyme-Linked Immuno Sorbent Assay (ELISA) would be useful to better understand the mechanisms behind disturbed spermatogenesis and could lead to new treatments for male infertility which can be due to a medical therapy or disorder.
|Date of Award||22 Jun 2018|
|Supervisor||Dorien Van Saen (Advisor), Yoni Baert (Advisor) & Ellen Goossens (Promotor)|