Improvement of in vitro proliferation of cockerel spermatogonial stem cells using different combinations of growth factors.

1. This study examined whether in vitro proliferation and maintenance of cockerel spermatogonial stem cells (SSCs) could be improved by adding different combinations of growth factors (GFs), including glial cell line-derived neurotrophic factor (GDNF), basic fibroblast growth factor (bFGF) or leukaemia inhibitory factor (LIF) into the culture medium. 2. The SSCs were isolated from the testes of immature cockerels. For short-term cultures, a medium supplemented with different combinations of GFs for 7 d in 5 replicates was used. The groups were classified as follows: without GF (control group); with GDNF (G group); with GDNF and bFGF (GF group); and with GDNF, bFGF and LIF (GFL group). The number of colonies and cells per colony, as well as the transcript abundance of STRA8 and OCT4 genes, was determined 7 d after the initial culturing. Immunofluorescence staining of SSEA-1, SSEA-3 and VASA protein markers, besides periodic acid-Schiff (PAS) staining, was carried out. 3. The number of colonies and cells per colony increased in the G, GF and GFL groups, compared to the control group (P < 0.01); however, the highest proliferation and colony formation were observed in the GFL group. The positive immunofluorescence staining of SSEA-1, SSEA-3 and VASA protein markers, as well as PAS staining, confirmed the self-renewal and colonisation of cockerel SSCs. The proliferation results were supported by the increased STRA8 and OCT4 transcript abundance in the treated groups (G, GF and GLF), compared to the control group. The SSC proliferation was associated with the higher transcript abundance of STAR8 and OCT4 genes in the GFL group, compared to the G and GF groups (P < 0.01). 4. The results showed that proliferation and colony-forming capacity of cockerel SSCs were positively improved by GDNF, bFGF and LIF. However, the most significant effect was observed when the medium was supplemented with LIF in combination with GDNF and bFGF.