Spermatogenesis involves mitosis, meiosis, growth, and differentiation of spermatogonial stem cells (SSCs), which are capable of self-renewal and differentiation into spermatozoa. Markers of spermatogonia and other spermatogenic cells have been extensively studied in rodents, whereas physiological characteristics and stage-specific markers of germ cells remain largely unknown in large domestic animals. In rodents, paired box protein 7 (PAX7) is known to be a specific marker of a rare spermatogonial subpopulation in adult testes, while being expressed by a large proportion of neonatal testicular germ cells. However, the expression of PAX7 has not yet been investigated in domestic animals. The objective of this study was to characterize PAX7 expression during boar testis development and in in vitro cultured porcine SSCs (pSSCs). Notably, the expression of PAX7 was positively correlated with that of a known boar testis spermatogonial and gonocyte marker, protein gene product 9.5 (PGP9.5), in prepubertal (5-day-old) boar testes but was not observed during or following puberty. Furthermore, the early-stage spermatogonial markers GDNF family receptor alpha-1 (GFRα1) and Sal-like protein 4 (SALL4) were coexpressed in PAX7⁺ testicular cells from 5-day-old boars. PAX7 expression was also maintained in in vitro cultured undifferentiated porcine spermatogonia, with both PAX7 and PGP9.5 strongly expressed in pSSC colonies but not in feeder cells (testicular somatic cells). These data demonstrated that PAX7 expression only occurred in boar testes during prepuberty and was mainly restricted to very early-stage spermatogonial germ cells, such as gonocytes, which implies that PAX7 can be used as a boar gonocyte marker.

精子发生涉及精子干细胞（SSC）的有丝分裂，减数分裂，生长和分化，它们能够自我更新并分化为精子。在啮齿动物中已广泛研究了精原细胞和其他生精细胞的标志物，而在大型家养动物中生殖细胞的生理特征和阶段特异性标志物仍是未知之数。在啮齿动物中，成对的盒蛋白7（PAX7）是成年睾丸中罕见的精原细胞亚群的特异性标记物，而新生婴儿的睾丸生殖细胞中有很大的表达量。然而，尚未在家畜中研究PAX7的表达。这项研究的目的是表征公猪睾丸发育过程中和体外的PAX7表达培养的猪SSC（pSSC）。值得注意的是，在青春期前（5日龄）的公猪睾丸中，PAX7的表达与已知公猪睾丸的精原和性腺细胞标记物，蛋白基因产物9.5（PGP9.5）的表达呈正相关。 。此外，早期精原标记GDNF家族受体α-1（GFRα1）和Sal样蛋白4（SALL4）在5天大公猪的PAX7 ⁺睾丸细胞中共表达。在体外PAX7表达也得以维持培养的未分化猪精原细胞，在pSSC集落中强烈表达PAX7和PGP9.5，但在饲养细胞（睾丸体细胞）中不表达。这些数据表明，PAX7表达仅在青春期前的公猪睾丸中发生，并且主要限于非常早期的精原生殖细胞，例如生殖细胞，这意味着PAX7可以用作公猪生殖细胞标记。