REPRODUCTION © 2017 Society for Reproduction and Fertility DOI: 10.1530/REP-17-0074 ISSN 1470–1626 (paper) 1741–7899 (online) Online version via www.reproduction-online.org RESEARCH Syndecan 1 represses cell growth and FSH responsiveness in human granulosa cells Simon Colombe 1 , Laura Houllier 1 , Emmanuelle Fleurot 1 , Guénaëlle Levallet 1,2 , Annie Benhaïm 1,3 , Pierre-Jacques Bonnamy 1 and Jérôme Levallet 1 1 Oestrogènes, Reproduction, Cancer, Normandie Université, UNICAEN, Normandie, France, 2 CHU de Caen, Service d’Anatomie Pathologique, Caen, France and 3 CHU de Caen, Laboratoire de Fécondation In Vitro, Service de Gynécologie Obstétrique, Caen, France Correspondence should be addressed to J Levallet; Email: Jerome.levallet@unicaen.fr Abstract Albeit devoid of intrinsic catalytic activity, the transmembrane heparan sulphate proteoglycan syndecan 1 plays critical roles in cellular processes such as extracellular matrix crosstalk, cytoskeletal organization, cell spreading, proliferation and differentiation. During the ovarian cycle, the expression of syndecan 1 in granulosa cells shows cyclic variation suggesting that it might fulfil specific roles in follicle development. To investigate its physiological roles on granulosa cells, syndecan 1 was overexpressed in human granulosa cell line KGN which retains features of granulosa cells from small antral follicle such as estradiol (E2) synthesis and low expression of functional FSH receptor (FSHR). We demonstrated that overexpression of syndecan 1 in immature granulosa cells (KGN-SDC1) induces a profound alteration in their intrinsic characteristics including enhanced spreading and attachment, both associated with a reduced growth rate. Flow cytometry analysis revealed that syndecan 1 overexpression increases the percentage of KGN cells in quiescent phase. This partial cell cycle exit is concordant with downregulated levels of CCND1 and CDK4 and upregulated expression of CDK inhibitor CDKN1A. In parallel both unstimulated and FSH-induced E2 synthesis are reduced in KGN-SDC1 through both repression of CYP19A1 and FSHR mRNA associated with decreased levels of potential regulators NR5A1 and ESR2. Additionally, we provide evidence that transient cAMP accumulation reduction in cells overexpressing syndecan 1 is accompanied by an increase in cAMP-hydrolysing PDE activity. Our results demonstrated that syndecan 1 might regulate differentiation of granulosa cells and follicular development by means of various mechanisms involving morphological changes, control of signalling pathways and alterations in gene expressions. Free French abstract: A French translation of this abstract is freely available at http://www.reproduction-online.org/ content/153/6/797/suppl/DC2. Reproduction (2017) 153 797–808 Introduction Syndecan 1, a member of transmembrane heparan sulphate proteoglycan (HSPG) family composed of four members, is expressed in cell- and tissue-type specific patterns. Composed of three major domains – a short cytoplasmic domain, a membrane-spanning domain and a long extracellular domain bearing heparan sulphate chains – syndecan 1 acts as cell surface receptor, regulating adhesion-dependent signalling pathways during cell growth, migration and differentiation (Bernfield et al. 1999, Couchman 2010). Through binding with the extracellular matrix components (ECM) and/or soluble ligands, syndecan 1 could recruit or tether, near the inner plasma membrane, some scaffolding proteins, thus acting as a regulator of membrane signalling pathways (Couchman 2010). Syndecan 1 can potentiate or inhibit some growth factor/tyrosine kinase receptor interactions through its HS (Bernfield et al. 1999). Additionally, syndecan 1 might be translocated into the nucleus to modulate transcription factors activities or induce histones post-translational modifications thus modulating the expression of genes (Brockstedt et al. 2002, Szatmari et al. 2012, Kovalszky et al. 2014). Hence, despite the lack of intrinsic catalytic activity, syndecan 1 plays significant roles in cell–cell and cell– matrix adhesion, in regulation of cell growth as well as in differentiation during the developmental processes. During follicular development, granulosa cells are essential for normal cycle and oocyte development. From the time they enter the selectable stage during the follicular phase, human granulosa cells from pre- antral follicles express FSH receptors and become sensitive to cyclic changes of FSH in terms of granulosa cell proliferation (Oktay et al. 1997). A small decrease in FSH concentration in growing follicles is enough to induce apoptosis of granulosa cells (Chun et al. 1996). Downloaded from Bioscientifica.com at 12/27/2018 10:04:24AM via free access