230 EFFECT OF DIFFERENT CONCENTRATIONS OF GLIAL CELL LINE-DERIVED NEUROTROPHIC FACTOR ON EXPRESSION OF SELF-RENEWAL RELATED GENES IN GOAT (CAPRA HIRCUS) SPERMATOGONIAL STEM CELLS

Abstract

Glial cell line-derived neurotrophic factor (GDNF), a member of the transforming growth factor-β superfamily produced by Sertoli cells, is essential for the self-renewal of spermatogonial stem cells in vivo. The present study evaluated the effects of different concentrations of GDNF (human recombinant expressed in Escherichia coli) on expression of some self-renewal related genes in spermatogonial stem cells (SSC). The SSC were isolated from prepubertal goat testes (3–6 months of age) by using double enzymatic digestion method and filtration through 80- and 60-µm nylon mesh filters. Further enrichment was achieved by differential plating on Datura stramonium agglutinin (DSA) lectin-coated dishes and Percoll density gradient centrifugation. The enriched cells were cultured on goat Sertoli cell feeder layer in DMEM + 10% fetal bovine serum at 37°C in a 5% CO₂ incubator. Primary SSC colonies were formed within 7 to 10 days. These colonies were characterised through alkaline phosphatase and immunofluorescence staining on Day 10 for different SSC-specific protein markers. Colonies were found to be positive for DBA, THY1, PLZF, UCHL1, OCT-4, SOX2, and NANOG, and negative for c-Kit expression. These colonies were cultured for 15 days without or with supplementation of GDNF forming following groups: (1) without GDNF (control), (2) 10 ng mL^–1 GDNF, (3) 20 ng mL^–1 GDNF, and (4) 40 ng mL^–1 GDNF. RNA was isolated from 100 colonies from 3 different trials on Day 15 of culture, and relative expression of different self-renewal related genes was determined by qRT-PCR. Relative mRNA abundance of PLZF was higher (P < 0.05) following supplementation with 40 ng mL^–1 GDNF than in other groups (i.e. control, 10 and 20 ng mL^–1 GDNF). Expression of BCL6B and ID4 was found to be significantly higher (P < 0.05) after supplementation of GDNF at all concentrations compared with the control group. Expression of UCHL1 was higher with addition of 20 and 40 ng mL^–1 GDNF (P < 0.05), whereas expression of THY1 was higher with supplementation of 10 ng mL^–1 GDNF (P < 0.05). In conclusion, GDNF was found to benefit expression of goat SSC candidate genes at a concentration of 40 ng mL^–1.