Oocyte Cryopreservation: A 9-Year Single-Centre Experience.

OBJECTIVE: Oocyte cryopreservation (OC) has increased in recent years; however, there is a paucity of published data on the use of cryopreserved oocytes and associated outcomes. METHODS: A retrospective review of 748 OC cycles between 2013 and 2022 at a private fertility centre was performed. Outcome parameters for oocyte retrieval cycles were reviewed. For patients who returned for oocyte disposition, outcomes subsequent to oocyte re-warming, fertilization, and transfer were analyzed. RESULTS: There were 748 OC cycles (653 elective and 95 non-elective) in 646 patients (556 elective and 90 non-elective). Patients were older at the time of freezing in the elective oocyte group compared with the non-elective group (36.5 vs. 28.8 y; P < 0.001). Sixty-five patients returned to warm and fertilize their oocytes (50 in the elective group and 15 in the non-elective group). The survival rate for warmed oocytes was 76.1% (541/711), and 66.2% of surviving oocytes were successfully fertilized, and 39.1% reached blastulation. Twenty-three patients underwent embryo transfers (10 after preimplantation genetic testing for aneuploidy), with 15 patients having at least 1 delivery or ongoing pregnancy. CONCLUSIONS: To date, this is the largest published experience with OC in Canada. OC can lead to successful live births but does not guarantee a viable outcome for all patients. In this study, most patients with vitrified oocytes had not returned for disposition, so long-term follow-up is still required to verify the efficacy of OC.

A Notch-dependent transcriptional hierarchy promotes mesenchymal transdifferentiation in the cardiac cushion.

BACKGROUND: Valvuloseptal defects are the most common congenital heart defects. Notch signaling-induced endothelial-to-mesenchymal transition (EMT) in the atrioventricular canal (AVC) cushions at murine embryonic day (E)9.5 is a required step during early valve development. Insights to the transcriptional network that is activated in endocardial cells (EC) during EMT and how these pathways direct valve maturation are lacking. RESULTS: We show that at E11.5, AVC-EC retain the ability to undergo Notch-dependent EMT when explanted on collagen. EC-Notch inhibition at E10.5 blocks expression of known mesenchymal genes in E11.5 AVC-EC. To understand the genetic network and AVC development downstream of Notch signaling beyond E9.5, we constructed Tag-Seq libraries corresponding to different cell types of the E11.5 AVC and atrium in wild-type mice and in EC-Notch inhibited mice. We identified 1,400 potential Notch targets in the AVC-EC, of which 124 are transcription factors (TF). From the 124 TFs, we constructed a transcriptional hierarchy and identify 10 upstream TFs within the network. CONCLUSIONS: We validated 4 of the upstream TFs as Notch targets that are enriched in AVC-EC. Functionally, we show these 4 TFs regulate EMT in AVC explant assays. These novel signaling pathways downstream of Notch are potentially relevant to valve development.

Notch initiates the endothelial-to-mesenchymal transition in the atrioventricular canal through autocrine activation of soluble guanylyl cyclase.

The heart is the most common site of congenital defects, and valvuloseptal defects are the most common of the cardiac anomalies seen in the newborn. The process of endothelial-to-mesenchymal transition (EndMT) in the cardiac cushions is a required step during early valve development, and Notch signaling is required for this process. Here we show that Notch activation induces the transcription of both subunits of the soluble guanylyl cyclase (sGC) heterodimer, GUCY1A3 and GUCY1B3, which form the nitric oxide receptor. In parallel, Notch also promotes nitric oxide (NO) production by inducing Activin A, thereby activating a PI3-kinase/Akt pathway to phosphorylate eNOS. We thus show that the activation of sGC by NO through a Notch-dependent autocrine loop is necessary to drive early EndMT in the developing atrioventricular canal (AVC).