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

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

Primordial germ cells (PGCs) play a crucial role in preserving poultry genetic resources and conducting transgenic research. A system for the rapid isolation of PGCs from single chicken embryonic blood was established in this paper. We found that PGCs can migrate to the lower layer of chicken embryonic fibroblasts (CEFs) through pores smaller than their diameter, while blood cells cannot, when co-cultured with CEFs of passages two to three. Based on the characteristics of PGCs, we developed a new PGC isolation method (cell culture insert/CEF adhesion method) that utilizes a 3 μm cell culture insert and CEFs of passages two to three. Using this method, approximately 700 PGCs can be isolated from the blood of a single chicken embryo at Hamburger and Hamilton (H&H) stage 17 of development. The separation rate achieved was 87.5%, with a separation purity of 95%. The separation rate of this method was 41.4% higher than the common Percoll density gradient centrifugation method and 33.6% higher than lysis with ACK buffer. PGCs isolated from embryonic blood could proliferate 37-fold within 2 weeks when cultured in a feeder-free culture system. They also continued to express the SSEA-1 and DAZL proteins and retained the ability to migrate in vivo. Overall, PGCs separated using cell culture inserts/CEF adhesion method retain their stem cell characteristics and migration ability. PGCs also exhibit good proliferation efficiency, making them suitable for subsequent transgenic experiments or genetic resource preservation.

Enhanced cultivation of chicken primordial germ cells

The cultivation and expansion of chicken primordial germ cells (cPGCs) are of critical importance for both biotechnological applications and the management of poultry genetic biodiversity. The feeder-free culture system has become the most popular approach for the cultivation and expansion of cPGCs. However, despite some success in the cultivation of cPGCs, the reproducibility of culture conditions across different laboratories remains a challenge. This study aimed to compare two defined and enriched media for the growth of cPGCs originating from the Hubbard JA57 broiler. To this end, cPGCs were isolated from the embryonic blood of Hamburger-Hamilton (HH) stages 14-16 and cultured at various time points. The Growth properties and characteristics of these cells were evaluated in two different culture conditions (the defined or enriched medium) and their migratory properties were assessed after genetic engineering and injection into the vasculature of 2.5-day-old chicken embryos. The main finding of this study was that the use of an enriched medium (the defined medium with Knock-Out Serum Replacement; KOSR) resulted in improved growth properties of cPGCs originating from the Hubbard JA57 broiler compared to a defined medium. The ability to cultivate and expand cPGCs is crucial for the generation of both genetically engineered birds and breeds of interest from local or commercial origins. Therefore, these results highlight the importance of choosing an appropriate culture medium for cPGCs growth and expansion.

The constitutively active pSMAD2/3 relatively improves the proliferation of chicken primordial germ cells

In many multicellular organisms, mature gametes originate from primordial germ cells (PGCs). Improvements in the culture of PGCs are important not only for developmental biology research, but also for preserving endangered species, and for genome editing and transgenic animal technologies. SMAD2/3 appear to be powerful regulators of gene expression; however, their potential positive impact on the regulation of PGC proliferation has not been taken into consideration. Here, the effect of TGF-β signaling as the upstream activator of SMAD2/3 transcription factors was evaluated on chicken PGCs' proliferation. For this, chicken PGCs at stages 26-28 Hamburger-Hamilton were obtained from the embryonic gonadal regions and cultured on different feeders or feeder-free substrates. The results showed that TGF-β signaling agonists (IDE1 and Activin-A) improved PGC proliferation to some extent while treatment with SB431542, the antagonist of TGF-β, disrupted PGCs' proliferation. However, the transfection of PGCs with constitutively active SMAD2/3 (SMAD2/3CA) resulted in improved PGC proliferation for more than 5 weeks. The results confirmed the interactions between overexpressed SMAD2/3CA and pluripotency-associated genes NANOG, OCT4, and SOX2. According to the results, the application of SMAD2/3CA could represent a step toward achieving an efficient expansion of avian PGCs.

Male Gonads Transplantation from Kadaknath Chicken to Chicken and Duck Surrogates

Transplantation of the gonadal tissue of male and female avian species, such as chicken, onto suitable surrogates and production of live offspring has been successfully demonstrated as a strategy for the conservation and re-constitution of valuable chicken germplasm. The main objective of this study was to establish and develop the male gonadal tissue transplantation technology for the conservation of the indigenous chicken germplasm. The male gonads of the Indian native chicken breed, Kadaknath (KN), were transplanted from a day-old donor to a recipient white leghorn (WL) chicken, and Khaki Campbell (KC) ducks, as surrogates. All the surgical interventions were performed under permitted general anaesthesia, and the chicks, upon recovery, were reared with and without immunosuppressant. The recipient surrogates for the donor KN gonads were housed and reared for 10-14 weeks, and post-sacrifice, developed gonadal tissues were harvested to squeeze out the fluid to perform artificial insemination (AI). The AI-entailed fertility test using the recovered seminal extract from the transplanted KN testes from both surrogate species (KC ducks and WL males), used against KN purebred females, remained very close to the percent fertility realised from purebred KN chickens (controls). These initial results revealed from this trial study suggest definitively that, Kadaknath male gonads were readily accepted and grown inside the intra- and inter-species surrogate host, WL chicken and KC ducks, demonstrating a suitable intra- and inter-species donor-host system. Furthermore, the developed transplanted male gonads of KN chicken into the surrogates were found to have the potential to fertilise the egg and give rise to pure-line KN chicks.