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  • Author: Matti Poutanen x
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Heikki T Turunen, Petra Sipilä, Leena Strauss, Ida Björkgren, Ilpo Huhtaniemi and Matti Poutanen

Bmyc is a member of the Myc family of transcriptional regulators in the mouse and the rat. It is predominantly expressed in hormonally controlled tissues, with highest level of expression in the epididymis. The BMYC protein has been shown to function as a transcription factor in vitro and to inhibit MYC. To study the significance of BMYC in vivo, a Bmyc knockout (KO) mouse model was generated by homologous recombination. The KO mice were viable and fertile and did not display gross morphological or histological changes compared to the WT mice. However, the testes and the epididymides of the KO mice were smaller than those of the WT mice. Correspondingly, a tendency for a lower sperm concentration in the cauda epididymides of the KO mice was detected. The testosterone produced/testis was significantly reduced, and accordingly, the LH levels were increased in the KO mice. Also, the expression levels of Myc and several of its target genes were elevated in the testes of prepubertal KO mice, whereas no differences in gene expression levels were detected in adult mice. Associated with the increased Myc expression, more apoptotic spermatogenic cells were detected in the seminiferous tubules of the KO mice. In conclusion, our data suggest that Bmyc is a regulator of Myc in vivo and that overexpression of Myc in the developing testis leads to increased apoptosis of spermatogenic cells.

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Samu Myllymaa, Arja Pasternack, David G Mottershead, Matti Poutanen, Minna M Pulkki, Lauri J Pelliniemi, Olli Ritvos and Mika P E Laitinen

Growth differentiation factor-9 (GDF9) and bone morphogenetic protein-15 (BMP15) are among the key regulators transmitting the signaling between the oocyte and the surrounding granulosa cells. Previously, it has been shown that a recombinant BMP type II receptor ectodomain–Fc fusion protein (BMPR2ecd–Fc) is able to inhibit the actions of GDF9 and BMP15 in vitro. Here, we have produced bioactive BMPR2ecd–Fc, which was injected i.p. into neonatal mice. Early folliculogenesis was first studied by injecting mice five times with various doses of BMPR2ecd–Fc during the postnatal days 4–12. Folliculogenesis was affected dose dependently, as evidenced by a decreased mitogenesis of granulosa cells of the growing follicles. Furthermore, we also noticed a decrease in the number of secondary and tertiary follicles as well as an increase in the oocyte size. Electron microscopic analysis revealed that the ultrastructure of the granulosa cells of the primary follicles was not affected by the BMPR2ecd–Fc treatment. A second study was conducted to investigate whether a longer treatment with 12 injections during postnatal days 4–28 would inhibit folliculogenesis. Similar effects were observed in the two studies on the early follicular developmental stages. However, in the long-term study, later stages of folliculogenesis were not blocked but rather increased numbers of antral follicles, preovulatory follicles, and corpora lutea were found. We conclude that BMPR2ecd–Fc is a potent modulator of ovarian folliculogenesis in vivo, and thus, is a valuable tool for studying the physiology and downstream effects of oocyte-derived growth factors in vivo.

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Lena Walenta, Nina Schmid, J Ullrich Schwarzer, Frank-Michael Köhn, Henryk F Urbanski, Rüdiger Behr, Leena Strauss, Matti Poutanen and Artur Mayerhofer

NLRP3 is part of the NLRP3 inflammasome and a global sensor of cellular damage. It was recently discovered in rodent Sertoli cells. We investigated NLRP3 in mouse, human and non-human primate (marmoset and rhesus macaque) testes, employing immunohistochemistry. Sertoli cells of all species expressed NLRP3, and the expression preceded puberty. In addition, peritubular cells of the adult human testes expressed NLRP3. NLRP3 and associated genes (PYCARD, CASP1, IL1B) were also found in isolated human testicular peritubular cells and the mouse Sertoli cell line TM4. Male infertility due to impairments of spermatogenesis may be related to sterile inflammatory events. We observed that the expression of NLRP3 was altered in the testes of patients suffering from mixed atrophy syndrome, in which tubules with impairments of spermatogenesis showed prominent NLRP3 staining. In order to explore a possible role of NLRP3 in male infertility, associated with sterile testicular inflammation, we studied a mouse model of male infertility. These human aromatase-expressing transgenic mice (AROM+) develop testicular inflammation and impaired spermatogenesis during aging, and the present data show that this is associated with strikingly elevated Nlrp3 expression in the testes compared to WT controls. Interference by aromatase inhibitor treatment significantly reduced increased Nlrp3 levels. Thus, throughout species NLRP3 is expressed by somatic cells of the testis, which are involved in testicular immune surveillance. We conclude that NLRP3 may be a novel player in testicular immune regulation.

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Kalle T Rytkönen, Taija Heinosalo, Mehrad Mahmoudian, Xinghong Ma, Antti Perheentupa, Laura L Elo, Matti Poutanen and Günter P Wagner

Human reproductive success depends on a properly decidualized uterine endometrium that allows implantation and the formation of the placenta. At the core of the decidualization process are endometrial stromal fibroblasts (ESF) that differentiate to decidual stromal cells (DSC). As variations in oxygen levels are functionally relevant in endometrium both upon menstruation and during placentation, we assessed the transcriptomic responses to hypoxia in ESF and DSC. In both cell types, hypoxia-upregulated genes in classical hypoxia pathways such as glycolysis and the epithelial mesenchymal transition. In DSC, hypoxia restored an ESF-like transcriptional state for a subset of transcription factors that are known targets of the progesterone receptor, suggesting that hypoxia partially interferes with progesterone signaling. In both cell types, hypoxia modified transcription of several inflammatory transcription factors that are known regulators of decidualization, including decreased transcription of STATs and increased transcription of CEBPs. We observed that hypoxia-upregulated genes in ESF and DSC had a significant overlap with genes previously detected to be upregulated in endometriotic stromal cells. Promoter analysis of the genes in this overlap suggested the hypoxia-upregulated Jun/Fos and CEBP transcription factors as potential drivers of endometriosis-associated transcription. Using immunohistochemistry, we observed increased expression of JUND and CEBPD in endometriosis lesions compared to healthy endometria. Overall, the findings suggest that hypoxic stress establishes distinct transcriptional states in ESF and DSC and that hypoxia influences the expression of genes that contribute to the core gene regulation of endometriotic stromal cells.