EGF, GDNF, and IGF-1 influence the proliferation and stemness of ovine spermatogonial stem cells in vitro

Purpose The objective of the present study was to purify sheep spermatogonial stem cells (SSCs) from testicular isolate using combined enrichment methods and to study the effect of growth factors on SSC stemness during culture. Methods The testicular cells from prepubertal male sheep were isolated, and SSCs were purified using Ficoll gradients (10 and 12%) followed by differential plating (laminin with BSA). SSCs were cultured with StemPro (R)-34 SFM, additives, and FBS for 7 days. The various doses (ng/ml) of growth factors, EGF at 10, 15, and 20, GDNF at 40, 70, and 100 and IGF-1 at 50, 100, and 150 were tested for the proliferation and stemness of SSCs in vitro. The stemness in cultured cells was assessed using SSC markers PLZF, ITGA6, and GFR alpha 1. Results Ficoll density gradient separation significantly (p < 0.05) increased the percentage of SSCs in 12% fraction (35.1 +/- 3.8 vs 11.2 +/- 3.7). Subsequently, purification using laminin with BSA plating further enriched SSCs to 61.7 +/- 4.7%. GDNF at 40 ng/ml, EGF at 15 and 20 ng/ml and IGF1 at 100 and 150 ng/ml significantly (p < 0.05) improved proliferation and stemness of SSCs up to 7 days in culture. GDNF at 40 ng/ml outperformed other growth factors tested and could maintain the ovine SSCs proliferation and stemness for 36 days. Conclusions The combined enrichment method employing density gradient centrifugation and laminin with BSA plating improves the purification efficiency of ovine SSCs. GDNF at 40 ng/ml is essential for optimal proliferation and sustenance of stemness of ovine SSCs in vitro.