Abstract
In the testis, the germinal epithelium of seminiferous tubules is surrounded by contractile peritubular cells, which are involved in sperm transport. Interestingly, in postnatal testis, polysialic acid (polySia), which is also an essential player for the development of the brain, was observed around the tubules. Western blotting revealed a massive decrease of polySia from postnatal day 1 towards puberty, together with a fundamental reduction of the net-like intertubular polySia. Using polysialyltransferase knockout mice, we investigated the consequences of the loss of polySia in the postnatal testis. Compared to postnatal wild-type animals, polySia knockouts showed slightly reduced smooth muscle actin (SMA) immunostaining of peritubular smooth muscle cells (SMCs), while calponin, marking more differentiated SMCs, dramatically decreased. In contrast, testicular SMA and calponin immunostaining remained unchanged in vascular SMCs in all genotypes. In addition, the cGMP-dependent protein kinase PKG I, a key enzyme of SMC relaxation, was nearly undetectable in the peritubular SMCs. Cell proliferation in the peritubular layer increased significantly in the knockouts, as shown by proliferating cell nuclear anti (PCNA) staining. Taken together, in postnatal testis, the absence of polySia resulted in an impaired differentiation of peritubular, but not vascular, SMCs to a more synthetic phenotype. Thus, polySia might influence the maintenance of a differentiated phenotype of non-vascular SMCs.
Highlights
The testis is responsible for the production of male germ cells and testosterone [1].The major components of the testis are the seminiferous tubules, with their germinal epithelium [1] and the surrounding peritubular lamina propria [2,3,4]
To examine the impact of polysialic acid (polySia) on the contractile elements of the testis, we investigated the phenotype of smooth muscle cells (SMCs) in polySia knockout mice during postnatal development, demonstrating that the phenotype of peritubular SMCs, different to vascular SMCs, changed in the absence of polySia
In the postnatal murine testis, polySia-positive areas were found in the tunica albuginea [8]
Summary
The testis is responsible for the production of male germ cells and testosterone [1]. The major components of the testis are the seminiferous tubules, with their germinal epithelium [1] and the surrounding peritubular lamina propria [2,3,4] In rodents, this structure consists only of a single layer of contractile (myoid) cells. During postnatal development, the contractile areas of the testis exhibit high amounts of polysialic acid (polySia) [8], which is an essential biomolecule for the development of the brain [9,10,11,12]. To examine the impact of polySia on the contractile elements of the testis, we investigated the phenotype of smooth muscle cells (SMCs) in polySia knockout mice during postnatal development, demonstrating that the phenotype of peritubular SMCs, different to vascular SMCs, changed in the absence of polySia
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