PARENT SESSION
OVARY - C

Wednesday, August 4, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(761) NEUROTROPHIN REGULATION OF GERM CELL PROLIFERATION IN THE HUMAN FETAL OVARY.

Anderson, Richard¹, Robinson, Lynne¹, Bayne, Rosey¹, ¹ MRC Human Reproductive Sciences Unit, Edinburgh, UK

ABSTRACT- The regulation of germ cell proliferation and primordial follicle formation are poorly understood. There is increasing evidence that neurotrophins may be involved in these processes: NT4 and its cognate receptor TrkB are expressed in the developing ovary of both mouse and human, and blockade of neurotrophin signalling reduces germ cell survival during the developmental period preceding primordial follicle formation. We have investigated whether there are changes in expression of NT4 and its receptors (TrkB, truncated TrkB and p75) during this period in the human, and the effect of neurotrophin receptor blockade on germ cell proliferation in vitro. Fetal ovaries were obtained following termination of pregnancy, with IRB approval and written consent. Ovaries were either frozen for subsequent RNA extraction and analysis by quantitative RT-PCR using the Lightcycler, or cut into 0.5mm3 fragments and cultured for 48 hr in serum-free medium in the presence or absence of the Trk receptor blocker K252a (100nM). Proliferation was detected by bromodeoxyuridine (BrdU) incorporation using immunohistochemistry and random stage stereology. Expression of RNA for NT4 increased 1.8 fold between 14 and 19 weeks gestation (p=0.04), and of truncated TrkB by 1.9 fold (p=0.02). Expression of full-length TrkB and p75 was low across this gestational range. Germ cells showed proliferation in vitro with 22±4% (13-16 weeks, n=5) immunostaining for BrdU. This was reduced to 13±4% (p=0.05) in the presence of K252a. Similarly, the number of BrdU+ve germ cells was reduced from 12.8±2.3 to 4.3±1.5 (p=0.04) per unit area. Primordial follicles are seen in the human ovary from 18 weeks gestation and thus are increasingly prevalent during the later part of the gestational range examined here. These data confirm the involvement of neurotrophins and particularly NT4 in ovarian development in the human during the weeks leading up to primordial follicle formation.

KEY WORDS: ovary development, fetal ovary, primordial follicle, neurotrophin