In Vitro Culture of Chicken Circulating and Gonadal Primordial Germ Cells on a Somatic Feeder Layer of Avian Origin

SIMPLE SUMMARY: Chicken primordial germ cells are specialized cells that are formed outside the developing embryo, from where they migrate into the gonad, and give rise to the gametes. There are two types of those cells: Circulating blood primordial germ cells and gonadal primordial germ cells. They can be isolated only in low numbers from the bloodstream or gonads of donor embryos. Hence, efficient in vitro cultivation systems are required to increase their quantity through proliferation. Here, we provide a single culture system that can be used to cultivate both cell types. We also present a novel, easy-to-train, and non-invasive method to identify live primordial germ cells in the culture. In this analysis, chicken primordial germ cells obtained from embryonic blood or gonadal regions were cultured in vitro on feeder cell layers derived from embryonic chick cells. The use of the chicken origin feeder layer allowed reducing the xenogenic animal factors in the culture. We demonstrated a feasible and cost-efficient technique to routinely assess the cultivated primordial germ cells on the basis of their morphological characteristics and using the optical features of cells in darkfield illumination. This method is especially useful to distinguish primordial germ cells during co-cultivation with other cell types. ABSTRACT: The present study had two aims: (1) To develop a culture system that imitates a normal physiological environment of primordial germ cells (PGCs). There are two types of PGCs in chicken: Circulating blood (cPGCs) and gonadal (gPGCs). The culture condition must support the proliferation of both cPGCs and gPGCs, without affecting their migratory properties and must be deprived of xenobiotic factors, and (2) to propose an easy-to-train, nonlabeling optical technique for the routine identification of live PGCs. To address the first aim, early chicken embryo’s feeder cells were examined instead of using feeder cells from mammalian species. The KAv-1 medium at pH 8.0 with the addition of bFGF (basic fibroblast growth factor) was used instead of a conventional culture medium (pH approximately 7.2). Both cPGCs and gPGCs proliferated in vitro and retained their migratory ability after 2 weeks of culture. The cultivated cPGCs and gPGCs colonized the right and/or left gonads of the recipient male and female embryos. To address the second aim, we demonstrated a simple and rapid method to identify live PGCs as bright cells under darkfield illumination. The PGCs rich in lipid droplets in their cytoplasm highly contrasted with the co-cultured feeder layer and other cell populations in the culture.