Transcriptional response of endometrial cells to insulin, cultured using microfluidics

Abstract

Obesity is a rapidly growing public health issue among women of reproductive age associated with decreased reproductive function including implantation failure. This can result from a myriad of factors including impaired gametes and endometrial dysfunction. The mechanisms of how obesity-related hyperinsulinaemia disrupts endometrial function are poorly understood. We investigated potential mechanisms by which insulin alters endometrial transcript expression. Ishikawa cells were seeded into a microfluidics device attached to a syringe pump to deliver a constant flow rate of 1 µL/min of the following: (i) control (ii) vehicle control (acidified PBS), or (iii) insulin (10 ng/mL) for 24 h (n = 3 biological replicates). Insulin-induced transcriptomic response of endometrial epithelial cells was determined via RNA sequencing, and DAVID and Webgestalt to identify Gene Ontology (GO) terms and signalling pathways. A total of 29 transcripts showed differential expression levels across two comparison groups (control vs vehicle control; vehicle control vs insulin). Nine transcripts were differentially expressed in vehicle control vs insulin comparison (P < 0.05). Functional annotation analysis of transcripts altered by insulin (n = 9) identified three significantly enriched GO terms: SRP-dependent co-translational protein targeting to membrane, poly(A) binding, and RNA binding (P < 0.05). The overrepresentation analysis found three significantly enriched signalling pathways relating to insulin-induced transcriptomic response: protein export, glutathione metabolism, and ribosome pathways (P < 0.05). Transfection of siRNA for RAPSN successfully knocked down expression (P < 0.05), but this did not have any effect on cellular morphology. Insulin-induced dysregulation of biological functions and pathways highlights potential mechanisms by which high insulin concentrations within maternal circulation may perturb endometrial receptivity. Lay summary Changes in components of blood associated with obesity in women of reproductive age can have consequences for pregnancy success. These changes to circulating molecules associated with obesity can alter the ability of the endometrium (the innermost lining of the womb/uterus) to be receptive to an embryo to implant – a key stage of successful pregnancy. Understanding which molecules contribute to this is difficult and one in particular, insulin, can change the role of the endometrium. Studying this is limited to static culture, that is, the cells are not exposed to sustained and high concentrations of Insulin that could occur in the mother. In this study, we use a new laboratory-based approach (microfluidics) that allows us to mimic maternal circulation. We have determined that exposure of these endometrial cells to insulin changes the expression of specific genes that may lead to the inability of the endometrium to support implantation and early pregnancy.