Susanna Dolci

Leukemia inhibitory factor sustains the survival of mouse primordial germ cells cultured on TM4 feeder layers

Various growth factors and cytokines were tested for their effects on survival and proliferation of mouse primordial germ cells (PGCs) cultured on TM4 cell feeder layers. Leukemia inhibitory factor was able to sustain the survival of PGCs from 10.5 dpc embryos for at least 3 days and to slow down degeneration of PGCs from 11.5 dpc embryos cultured on TM4 feeder layers.

Cellular interactions of mouse fetal germ cells in in vitro systems

Publisher Summary This chapter discusses the germ cell differentiation in the mouse embryo and cellular interactions during early germ cell differentiation. The development of germ cells in the mouse embryo, as well as in all other mammals, can be schematically divided into four main periods—migratory, proliferative, sex differentiation, and cell death. In the mouse embryo primordial germ cells can be identified by their high alkaline phosphatase activity at the posterior end of the primitive streak about 8 days post coitum. In all mammalian embryos, waves of degeneration drastically reduce the number of germ cells before birth. Throughout their entire life history, germ cells do not exist as an independent tissue, but are always associated with other cells from which they may derive nutrients as well as developmental signals. It is likely that the sequential expression of the different genes that direct germ cell differentiation may be modulated by cellular interactions that involve cell contact and cell position as a function of time. There is evidence suggesting that during the developmental periods germ cells are involved in at least two different kinds of cellular interactions: germ cell– extracellular matrix and germ cell–somatic cell interactions.

SOHLH1 and SOHLH2 directly down-regulate STIMULATED BY RETINOIC ACID 8 (STRA8) expression

As the name implies, Stimulated by Retinoic Acid 8 is an early retinoic acid (RA) responsive gene pivotal for the beginning of meiosis in female and male germ cells. Its expression is strictly time-dependent and cell-specific (pre-meiotic germ cells) and likely requires a complex mechanism of regulation. In this study, we demonstrate a direct negative control of SOHLH1 and SOHLH2, 2 germ cell specific bHLH transcription factors, on Stra8 expression. We observed a negative correlation between STRA8 and SOHLH1 expression in prepuberal differentiating mouse KIT+ spermatogonia and found that SOHLH1 and SOHLH2 were able to directly and cooperatively repress STRA8 expression in cell lines in vitro through binding to its promoter. We also identified 2 canonical E-Box motives in the Stra8 promoter that mediated the negative regulation of SOHLH1 and SOHLH2 on these gene both in the cell lines and KIT+ spermatogonia. We hypothesize that this novel negative activity of SOHLH1and SOHLH2 in male cooperates with that of other transcription factors to coordinate spermatogonia differentiation and the RA-induced meiosis and in female ensures STRA8 down-regulation at mid-end stages of meiotic prophase I.

Platelet‐Derived Growth Factor Regulation of Type‐5 Phosphodiesterase in Human and Rat Penile Smooth Muscle Cells

INTRODUCTION Relaxation of cavernous smooth muscle cells (SMCs) is a key component in the control of the erectile mechanism. SMCs can switch their phenotype from a contractile differentiated state to a proliferative and dedifferentiated state in response to a change of local environmental stimuli. Proliferation and contraction are both regulated by the intracellular second messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which are degraded by phosphodiesterases (PDEs). The most abundant PDE present in corpora cavernosa is the electrolytic cGMP-specific phosphodiesterase type 5 (PDE5). AIM We investigated the cellular localization of PDE5 in in vitro cultured corpora cavernosa cells and the effect of mitogenic stimulation on PDE5 expression. METHODS Biochemical ad molecular techniques on cultured SMCs from human and rat penis. MAIN OUTCOME MEASURES We studied the ability of the quiescent SMC phenotype vs. the proliferating phenotype in modulation of PDE5 expression. RESULTS We demonstrated that PDE5 is localized in the cytoplasm, in the perinuclear area, and in discrete cytoplasmic foci. As previously demonstrated in human myometrial cells, the cytoplasmic foci may correspond to centrosomes. In corpora cavernosa, PDE5 protein levels are strongly regulated by the mitotic activity of the SMCs, as they were increased in quiescent cultures. In contrast, treatment with platelet-derived grow factor (PDGF), one of the most powerful mitogenic factors for SMCs, reduces the expression of PDE5 after 24 hours of treatment. CONCLUSION We found that PDGF treatment downregulates PDE5 expression in proliferating SMCs, suggesting that PDE5 may represent one of the markers of the contractile phenotype of the SMCs of corpora cavernosa.