OR17-4 Hormone Replacement Promotes Sexual Maturation and Fertility Restoration in Mice With Congenital Hypopituitarism Harboring Prop1 Mutation

Introduction The Ames strain, a spontaneous mutant mouse of the Prop1 gene, is deficient in GH, TSH, PRL and gonadotropins. In recent years, it has been the focus of studies on aging and there is a growing interest in elucidating the role of hormone replacement (HR) in the hypothalamic-pituitary-gonadal (HPG) axis. Aim The present study aimed to characterize sexual maturation and fertility restoration in isogenic strain under or not HR. Material and methods Five homozygous male animals were treated via intraperitoneal injections, starting 30 days postnatally, with levothyroxine 3x/week and recombinant human GH 5x/week for 40 days, followed by maintenance applications of both hormones once a week until they complete 90 days post natal. The sexual maturity was evaluated looking for balanoprepucial opening and descendent testis comparing untreated homozygous (n=5) with their wild type siblings (n=5). Fertility was evaluated by mating known fertile wild type animals with treated and untreated animals for 8 times. Reproductive parameters were evaluated between groups using histological sections of the testes (HE) and classified according to johnsen score where 1-2 was classified as absent germline cells and 8-10 normal development. At the sacrifice, testicular weight was measured using scale and spermogram was done looking for motility and viability in the sperm collected in the seminiferous tube. Gata2 transcription factor and pituitary hormones Lh, Fsh, Tsh, Prl and Gh transcriptional analysis were performed by RT-qPCR. Results The homozygous treated animals presented a 2 weeks delay in the age of sexual maturation compared to wild animals. Their fertility and reproductive parameters were restored noticed by increased testicular weight, improved spermatogenesis, similar morphology of seminiferous tubules (johnsen score 8.7) and spermogram compared to the wild type, besides presenting offspring when mated to their wild siblings. Sexual maturity was absent in most of the untreated homozygous animals presenting no offspring. The reproductive parameters in the untreated homozygous animals presented reduced testicular weight, size of seminiferous tubes leading to johnsen score as 5 and an azospermic spermogram in all animals. Interestingly 2 untreated homozugous animal had spontaneous maturation. Gata2 was significant decreased in the untreated animal (0,49 ± 0,19) compared to wild type (1 ± 0,15) (p≤ 0.019). LH transcriptional pattern was significant increase in the animals under treatment (1.56 ± 0.68) compared to homozygotes without hormonal intervention (0.36 ± 0.34) (p≤ 0.048). Conclusion Ames mutant mice under treatment with GH and levothyroxine replacement reached sexual maturation and restored fertility and the mechanics behind this phenomenon will be explored using RNA seq in the future. Presentation: Sunday, June 12, 2022 11:45 a.m. - 12:00 p.m.