Concentration and total number of circulating primordial germ cells in Green-legged Partridgelike chicken embryos

Abstract

The Green-legged Partridgelike fowl is an old Polish indigenous breed of chicken. Primordial germ cells ( PGCs ) are one of the best sources of precursor cells that can be used for the conservation and proliferation of the endangered breeds of bird. Initially, the chicken PGCs colonize at the anterior extraembryonic region called “germinal crescent,” and after the establishment of blood vascular circulation, they temporally circulate via the embryonic blood vascular system along with embryonic blood cells. They further colonize at the microcapillary networks of both right and left future gonadal regions. Subsequently, they migrate interstitially to reach gonadal anlages, where they begin to differentiate and eventually develop into the future ova or sperm. The basic knowledge regarding the concentration and the total number of circulating PGCs ( cPGCs ) throughout their circulating phase in the early embryonic stages is crucial for providing an insight into the mechanisms by which they circulate and colonize at the capillary networks of left and right future gonadal regions in each developmental stage. The present study aims to determine the most efficient developmental stage that is suitable to collect cPGCs. The concentration of cPGCs was directly measured, and total volume of embryonic blood was calculated based on the concentration of PKH26-stained embryonic blood cells which were injected 10 min before the blood sampling process in the same embryo during each stage of embryonic development from stage 13 Hamburger and Hamilton ( HH ; Hamburger and Hamilton, 1951 ) to 16 HH. Analysis of whole embryonic bloodstream revealed that at stage 14 HH of embryonic development, peak total number of cPGCs (386.3 cells/μL) and peak concentration of cPGCs (18.6 cells/μL) were observed. Later, there was a decrease in concentration, suggesting that the cPGCs might be trapped gradually by the capillary networks at the future gonadal regions after stage 15 HH.

Comparison of the Transcriptomic and Epigenetic Profiles of Gonadal Primordial Germ Cells of White Leghorn and Green-Legged Partridgelike Chicken Embryos

“…GP chickens have been kept in a flock without subjecting them to any selection process for more than 60 generations [ 18 ]. Our previous studies suggested that a GP can be an excellent model for research, for example, as a good source of PGCs [ 19 ] and hence has been extensively used for biotechnological manipulations [ 20 , 21 ].…”

“…Kuwana et al indicated a large variation in the PGC concentration even within the same breed [ 22 ]. The results of Szczerba et al [ 19 ] showed that the number of gPGCs was probably influenced by the stage of embryonic development. In the case of inbred lines or endangered breeds, the number of total PGCs seems to be lower compared to commercial chicken breeds [ 23 , 24 ].…”

“…The level of its methylation in GP was found to be high for 4.5 days. Our previous studies showed that at the 14th stage of HH (i.e., about day 2) of embryonic development of GP, the peak total number of cPGCs and the maximum concentration were observed [ 19 ]. There was a decrease in concentration at a later stage, suggesting that cPGCs may be gradually trapped by capillary networks.…”

Poultry genetic heritage cryopreservation and reconstruction: advancement and future challenges

“…Circulating PGCs comprised less than 0.02% of cells in the blood stream of early embryo, therefore a very small number of PGCs (50–150 cells per embryo) can be expected to be harvested in this way [ 100 ]. The peak concentration of circulating PGCs also varies between breeds and affected by incubation temperature [ 101 ]. The propagation of PGCs in culture in vitro to expand that small population of cells to 50,000 to 100,000 in 4–5 weeks before cryopreservation is necessary and helpful [ 102 ], as it reduces the technical skill needed to isolate and purify the cells before transplantation.…”

A Novel, Efficient Method to Isolate Chicken Primordial Germ Cells from Embryonic Blood Using Cell Culture Inserts

“…Avian PGC shows a distinct migration pathway during embryo development. PGCs originate in the epiblast layer, are scattered throughout the vascular system, and circulate with the blood flow from Hamburger and Hamilton (HH) stage 13 to 17 [4]. They then migrate to the germinal ridges at HH stage 27.…”