Implementation of ovarian tissue cryopreservation in Hong Kong.

INTRODUCTION: Worldwide, >130 babies have been born from ovarian tissue cryopreservation (OTC) and ovarian tissue transplantation (OTT). Ovarian tissue cryopreservation can improve quality of life among young female cancer survivors. Here, we assessed the feasibility of OTC and subsequent OTT in Hong Kong via xenografts in nude mice. METHODS: This pilot study was conducted in a university-affiliated tertiary hospital. Fifty-two ovarian tissues were collected from 12 patients aged 29 to 41 years during ovarian surgery, then engrafted into 34 nude mice. The efficacies of slow freezing and vitrification were directly compared. In Phase I, non-ovariectomised nude mice underwent ovarian tissue engraftment. In Phase II, ovariectomised nude mice underwent ovarian tissue engraftment, followed by gonadotrophin administration to promote folliculogenesis. Ovarian tissue viability was assessed by gross anatomical, histological, and immunohistochemical examinations before and after OTC. Follicular density and morphological integrity were also assessed. RESULTS: After OTC and OTT, grafted ovarian tissues remained viable in nude mice. Primordial follicles were observed in thawed and grafted ovarian tissues, indicating that the cryopreservation and transplantation protocols were both effective. The results were unaffected by gonadotrophin stimulation. CONCLUSION: This study demonstrated the feasibility of OTC in Hong Kong as well as primordial follicle viability after OTC and OTT in nude mice. Ovarian tissue cryopreservation is ideal for patients who cannot undergo the ovarian stimulation necessary for oocyte or embryo freezing as well as prepubertal girls (all ineligible for oocyte freezing). Our findings support the clinical implementation of OTC and subsequent OTT in Hong Kong.

Effects of strict public health measures on seroprevalence of anti-SARS-CoV-2 antibodies during pregnancy.

INTRODUCTION: A substantial number of people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remain asymptomatic throughout the course of infection. Nearly half of pregnant women with coronavirus disease 2019 (COVID-19) are asymptomatic upon diagnosis; these cases are not without risk of maternal morbidity. Here, we investigated the seroprevalence of anti-SARS-CoV-2 antibodies in an unselected sample of pregnant women in Hong Kong. METHODS: This prospective cohort study included pregnant women who presented for routine Down syndrome screening (DSS) between November 2019 and October 2020; all women subsequently delivered at the booking hospitals. Serum antibodies against SARS-CoV-2 were analysed using a qualitative serological assay in paired serum samples taken at DSS and delivery for all participants. RESULTS: In total, 1830 women were recruited. Six women (0.33%) were seropositive at the DSS visit; this seropositivity persisted until delivery. Of the six women, none reported relevant symptoms during pregnancy; one reported a travel history before DSS and one reported relevant contact history. The interval between sample collections was 177 days (range, 161-195). Among women with epidemiological risk factors, 1.79% with travel history, 50% with relevant contact history, and 0.77% with community SARS-CoV-2 testing history, were seropositive. CONCLUSION: The low seroprevalence in this study suggests that strict public health measures are effective for preventing SARS-CoV-2 transmission. However, these measures cannot be maintained indefinitely. Until a highly effective therapeutic drug targeting SARS-CoV-2 becomes available, vaccination remains the best method to control the COVID-19 pandemic.

Hyperglycaemia potentiates the teratogenicity of retinoic acid in diabetic pregnancy in mice.

AIMS/HYPOTHESIS: We recently showed in mice that maternal diabetes increases embryonic susceptibility to caudal regression induced by vitamin A metabolite retinoic acid. Here we tested whether in the maternal diabetic milieu hyperglycaemia is the critical factor responsible for mediating this increased susceptibility. METHODS: Non-diabetic pregnant mice were made hyperglycaemic by subcutaneous injections of glucose at regular intervals. Conversely, diabetic pregnant mice were treated with phlorizin to induce renal glucosuria and thus reduce blood glucose concentrations. Pregnant mice were treated with retinoic acid and the extent of caudal regression in mouse embryos, measured in terms of the ratio of tail length to crown-rump length was assessed. Embryos were also examined for Wnt-3a expression and cell death. RESULTS: Embryos of mice treated with glucose had a greater extent of caudal regression induced by retinoic acid than saline-treated controls, with enhanced down-regulation of Wnt-3a expression and exacerbated cell death specifically at the caudal end of the embryo. Embryos of diabetic mice treated with phlorizin had a similar extent of caudal regression to embryos of non-diabetic mice after treatment with retinoic acid. CONCLUSIONS/INTERPRETATION: Hyperglycaemia increases embryonic susceptibility to caudal regression induced by retinoic acid, with the underlying cellular and molecular changes closely mimicking those that occur in maternal diabetes. Reduction of blood glucose concentrations in diabetic mice completely abolishes this increased susceptibility to retinoic acid. These results suggest that in maternal diabetes hyperglycaemia is the critical factor responsible for potentiating the teratogenic effect of retinoic acid.