Reduced neurotrophin receptor TrkA gene expression in human granulosa cells: a novel marker of diminishing ovarian reserve?

Abstract

OBJECTIVE: To investigate granulosa cell neurotrophin (NT) and its receptor expression in diminished ovarian reserve (DOR) and to explore the association between NT receptors, AMH and ART outcome.DESIGN: Prospective clinical and laboratory based study.MATERIALS AND METHODS: Mural and cumulus granulosa cells were collected from 23 women (ages:26-46) undergoing ART: 15 women with male or tubal factor infertility and 8 with DOR (diagnosed by D3 FSH>10IU/L). FSH and AMH were measured on D3 of the cycle. Mural and cumulus cell mRNA was isolated and gene expression of nerve growth factor (NGF) and its receptors TrkA and p75NTR was quantified by qRT-PCR and normalized to GAPDH. Data were analyzed using correlation analysis as appropriate, Student t–test and expressed as Mean ± SEM.RESULTS: TrkA expression was significantly associated with the number of oocytes retrieved in both mural (r=0.62,p=0.0084) and cumulus (r=0.86,p=0.0001) granulosa cells. This association was stronger in women with DOR (mural, r= 0.89,p=0.017; cumulus, r=0.95,p=0.01). All women with an AMH cutoff≥0.8ng/ml had increased TrkA mRNA in mural (8.8 ± 1.3 vs 4.5 ± 1.9,p=0.05) and cumulus cells (10.7 ± 1.3 vs 4.7 ± 3.1,p=0.03). The ratio of p75NTR/TrkA receptors determines cell fate, with an increased ratio promoting apoptosis and a decreased ratio promoting survival. Women with a cumulus cell p75NTR/TrkA mRNA ratio cutoff≥2 had significantly fewer eggs retrieved (6.8 ± 0.9 vs 16 ± 2.5,p=0.02). Women with an AMH cutoff≥0.8 had a lower p75NTR/TrkA mRNA ratio in mural (1.4 ± 0.3 vs 3.2 ± 1,p=0.02) and cumulus cells (1 ± 0.4 vs 5.3 ± 2.9,p=0.02).CONCLUSION: This study identified the novel association between reduced TrkA expression in granulosa cells and decreased AMH levels and oocyte numbers. We postulate that NGF action, through granulosa cell receptors, alters follicular unit survival and, along with AMH and number of oocytes, is a significant indicator of DOR. OBJECTIVE: To investigate granulosa cell neurotrophin (NT) and its receptor expression in diminished ovarian reserve (DOR) and to explore the association between NT receptors, AMH and ART outcome. DESIGN: Prospective clinical and laboratory based study. MATERIALS AND METHODS: Mural and cumulus granulosa cells were collected from 23 women (ages:26-46) undergoing ART: 15 women with male or tubal factor infertility and 8 with DOR (diagnosed by D3 FSH>10IU/L). FSH and AMH were measured on D3 of the cycle. Mural and cumulus cell mRNA was isolated and gene expression of nerve growth factor (NGF) and its receptors TrkA and p75NTR was quantified by qRT-PCR and normalized to GAPDH. Data were analyzed using correlation analysis as appropriate, Student t–test and expressed as Mean ± SEM. RESULTS: TrkA expression was significantly associated with the number of oocytes retrieved in both mural (r=0.62,p=0.0084) and cumulus (r=0.86,p=0.0001) granulosa cells. This association was stronger in women with DOR (mural, r= 0.89,p=0.017; cumulus, r=0.95,p=0.01). All women with an AMH cutoff≥0.8ng/ml had increased TrkA mRNA in mural (8.8 ± 1.3 vs 4.5 ± 1.9,p=0.05) and cumulus cells (10.7 ± 1.3 vs 4.7 ± 3.1,p=0.03). The ratio of p75NTR/TrkA receptors determines cell fate, with an increased ratio promoting apoptosis and a decreased ratio promoting survival. Women with a cumulus cell p75NTR/TrkA mRNA ratio cutoff≥2 had significantly fewer eggs retrieved (6.8 ± 0.9 vs 16 ± 2.5,p=0.02). Women with an AMH cutoff≥0.8 had a lower p75NTR/TrkA mRNA ratio in mural (1.4 ± 0.3 vs 3.2 ± 1,p=0.02) and cumulus cells (1 ± 0.4 vs 5.3 ± 2.9,p=0.02). CONCLUSION: This study identified the novel association between reduced TrkA expression in granulosa cells and decreased AMH levels and oocyte numbers. We postulate that NGF action, through granulosa cell receptors, alters follicular unit survival and, along with AMH and number of oocytes, is a significant indicator of DOR.