THE PREDICTIVE POWER OF FSH RECEPTOR GENE EXPRESSION ANALYSIS FOR PERSONALIZED OVARIAN STIMULATION PREDICTIONS

Abstract

Objective

Traditional biomarkers for predicting response to Controlled Ovarian Stimulation (COS) have limited capabilities, highlighted by the portion of patients who do not fit the response pattern predicted by their AMH levels and age. Identifying biomarkers that enable better forecasting of response to COS is desirable, potentially revealing patients at elevated risk of hyperstimulation and those who might produce a fewer than optimal number of oocytes. It has been proposed that alternative transcripts of the follicle-stimulating hormone receptor (FSHR) gene might contribute to variation in response to COS. We examined this hypothesis and produced the first comprehensive catalogue of FSHR transcript variants.

Material and Methods

Patterns of FSHR mRNA splice variants were analysed in 126 patients. RNA extracted from granulosa cells was subjected to long-read nanopore sequencing, enabling analysis of the entire FSHR transcript in a single continuous sequence ‘read’.This was essential for determining whether variants affecting different parts of the transcript occur together or independently. Patients were categorised based on their COS response (high, low or normal), in addition to being classified by age, AMH level and the number of oocytes retrieved. Expression patterns of FSHR were compared to response to COS.

Findings

Full-length FSHR transcript was detected in 97.6% of patients, and skipping Exon 6 was observed in 68%. In total, 9 distinct FSHR mRNA variants were detected. Five novel transcripts were identified involving partial insertion of ∼100bp segments of introns 1 or 2, seen in 6.6% of patients. Inconsistent responses to COS were identified in 53% and 33% of the patients predicted via their age or AMH levels, respectively. As expected, older age was associated with higher FSH requirement per oocyte collected (p=0.02), and AMH levels declined with age (p=0.01). AMH levels and amount of FSH injection per oocyte retrieved were negatively correlated (p<0.001). Interestingly, women ≥38 expressed novel variants more often than their younger counterparts (p=0.02), potentially indicative of an age-related decline in transcriptional fidelity in granulosa cells, which may have wider clinical relevance. The only transcript potentially linked to an altered response to COS was that lacking exon 6, which was associated with greater numbers of oocytes produced (p=0.009). This transcript was observed less often in older patients with low response to COS (p= 0.03).

Discussion&Conclusion

AMH and age-dependent response predictions were unreliable in many patients, highlighting the importance of discovering more powerful biomarkers. Our findings suggest that skipping Exon 6 may be associated with greater sensitivity to COS, indicating that FSHR mRNA profiling could potentially play a role in personalisation of stimulation protocols. This conclusion underscores the potential implications of research in this area for assisted reproductive technology.