Retinoic acid promotes the final phase of Sertoli cell differentiation — ASN Events
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Retinoic acid promotes the final phase of Sertoli cell differentiation (#188)

Peter K. Nicholls 1 2 , Craig A. Harrison 1 2 , Katarzyna E. Rainczuk 1 , A. Wayne Vogl 3 , Peter G. Stanton 1 2
  1. Prince Henry's Institute of Medical Research, Clayton, VIC, Australia
  2. Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
  3. Department of Cellular and Physiological Sciences, Faculty of Medicine, Life Sciences Centre, The University of British Columbia, Vancouver, British Columbia, Canada

During embryonic and early postnatal gonadal development, Sertoli cells undergo extensive mitotic activity under the influence of numerous factors, including activins. From one week after birth, the rate of Sertoli cell proliferation declines rapidly, reaching mitotic quiescence around 15 dpp in the rat. This is immediately followed by the formation of tight junctions (TJ) between adjacent Sertoli cells, contributing to the blood-testis barrier (BTB). This final phase of Sertoli cell differentiation is necessary for germ cell development and male fertility.

Retinoid signaling is essential for germ cell differentiation and male fertility, as adult rodents fed a vitamin A deficient diet become reversibly infertile. The initiation of spermatogonial differentiation and germ cell meiosis occurs under the direction of local retinoid signaling in the testis, corresponding with the final phase of somatic Sertoli cell differentiation at puberty. We therefore hypothesized that retinoid signaling may simultaneously direct the final phase of Sertoli cell maturation.

To determine the actions of retinoids on Sertoli cell differentiation, primary rat Sertoli cells from pre-pubertal proliferative (10dpp) and quiescent (20dpp) phases were cultured with all-trans-retinoic acid (ATRA). ATRA potently suppressed activin-induced DNA synthesis and cell proliferation in both 10- and 20- dpp cells. ATRA also antagonised G1 phase progression by stimulating the expression of the cyclin-dependent kinase inhibitor, Cdkn2b, under both basal- and activin-stimulated conditions.

We then assessed the effect of retinoid signaling upon TJ formation. With 10 dpp cultures, ATRA initiated the formation of morphologically identifiable TJs by electron microscopy. ATRA also promoted TJ function in 20dpp cultures. Consistent with a pro-differentiative role, ATRA also increased the expression of Sertoli cell markers of maturation.

We conclude that retinoid signaling promotes Sertoli cell differentiation in vitro. Additionally, this data implicates retinoid signaling in the maintenance of the differentiated Sertoli cell phenotype in the adult testis.

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