Browsing by Subject "gonad development"

Bipotential gonads are precursor structures for testes and ovaries. Steroidogenic factor-1 (SF1) is one of the most important transcription factors in an embryo needed for the development and maintenance of bipotential gonads. If SF1 is not expressed, bipotential gonads fail to develop, and genitalia and kidneys are not formed. Later, SF1 expression persists high in testes, where it supports Sertoli and Leydig cell formation and development. If SF1 is not expressed enough in males, the bipotential gonads differentiate into ovaries. The factors activating and regulating SF1 are not currently fully known. By getting more knowledge of how SF1 is controlled, regulatory mechanisms behind normal fetal development of gonads and disorders of sex development (DSD) can be understood better. The aims of this thesis were to study whether growth factors, that naturally regulate differentiation of developing gonads, promote differentiation of human induced pluripotent stem cells (hiPSC) into Sertoli-like cells (SLCs) and whether SF1 expression is induced by the addition of these growth factors. For conducting the study, we used hiPSCs, which have an SF1 activation domain cassette previously introduced to the cells by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated protein 9 (Cas9) (CRISPR/Cas9) method. SF1 could be activated by adding doxycycline (DOX) and trimethoprim (TMP). These hiPSCs were differentiated into intermediate mesoderm (IM) on the first four days according to the protocol published earlier by the group. After this, the differentiation to SLCs was guided by adding growth factors to the culture medium. Basic fibroblast growth factor (bFGF), fibroblast growth factor 9 (FGF9) and prostaglandin-2 (PGD2) were tested separately and in a combined cocktail also including follicle stimulating (FSH) and glial cell-derived neurotrophic factor (GDNF). In a control condition, cells were differentiated without additional growth factors. In all tested conditions, cells first differentiated into IM were further differentiated either in the presence or absence of DOX and TMP for 8 days. The differentiation medias were changed to the cells every day and lysis samples for quantitative PCR (qRT-PCR) were taken every other day. The relative gene expression levels of bipotential gonad, testis and steroidogenic gene markers from each condition were monitored with qRT-PCR and compared to the levels of the undifferentiated hiPSCs. Immunocytochemistry was performed to see the changes in protein production. Against our hypothesis and the previous studies by others, none of the tested growth factors induced the cells to differentiate into SLCs. However, SF1 expression was triggered by chemical induction with DOX and TMP. Also, the expression levels of bipotential gonadal and testicular gene markers increased in control conditions with/without chemical induction. PGD2 conditions were the only ones to resemble the gene expression and morphology of control conditions while the others differed. These results indicated that the addition of bFGF, FGF9, FSH and GDNF did not improve the differentiation of iPSCs into SLCs and in fact, bFGF and FGF9 hindered their differentiation into SLCs. As a future perspective the optimal concentrations for each growth factor and the duration of growth factor supplementation ought to be tested to refine the protocol.