Protein gene product 9.5 is a spermatogonia-specific marker in the pig testis: Application to enrichment and culture of porcine spermatogonia

Identification and isolation of spermatogonial stem cells (SSCs) are a prerequisite for culture, genetic manipulation, and/or transplantation research. In this study, we established that expression of PGP 9.5 is a spermatogonia-specific marker in porcine testes. The expression pattern of PGP 9.5 in spermatogonia was compared to cell type-specific protein (GATA-4 or PLZF) expression in seminiferous tubules at different ages, and expression levels of PGP 9.5, Vasa, and Oct-4 were compared in different cell fractions. Enrichment of spermatogonia from 2-week-old (2wo) and 10-week-old (10wo) boars by adhesion to laminin, differential plating, or velocity sedimentation followed by differential plating was assessed by identification of spermatogonia using expression of PGP 9.5 as a marker. Compared to the initial samples, spermatogonia were enriched twofold in laminin-selected cells (P < 0.05), and fivefold either in cells remaining in suspension (fraction 1) or in cells slightly attached to the culture dish (fraction 11) (P < 0.05) after differential plating. Cells in fraction 11 appeared to be superior for future experiments due to higher viability (> 90%) than in fraction 1 (similar to 50%). Velocity sedimentation plus differential plating achieved cell populations containing up to 70% spermatogonia with good viability (> 80%). Enriched spermatogonia from 2wo and 10wo testes could be maintained in a simple culture medium without additional growth factors for at least 2 weeks and continued to express PGP 9.5. These data provide the basis for future studies aimed at refining conditions of germ cell culture and manipulation prior to germ cell transplantation in pigs.