Microplastic exposure induces epithelial barrier alterations and increases collagen deposition in a 3D human endometrial model in vitro

Purpose: To investigate the effects of microplastics (MPs) on the human endometrium in vitro. Methods: A predictive 3D endometrial in vitro model was generated using highly porous scaffolds where human endometrial stromal (hESC) and epithelial (hEEC) cells were co-cultured for 35 days. The newly generated endometrial barrier was then exposed to different MP concentrations (from 0.25 to 50 mg/ml) for 24 h and 48 h, respectively. Histological staining and functional analyses were performed to assess the endometrial barrier integrity. Molecular studies and collagen deposition were evaluated to investigate the possible activation of pro-apoptotic and pro-fibrotic related pathways. Results: MP exposure for 24 h does not affect endometrial barrier integrity nor collagen synthesis and deposition. Similar responses are detected when concentrations between 0.25 and 1 mg/ml are used for 48 h. In contrast, 48-h incubations with higher doses (10–50 mg/ml MPs) induce epithelial barrier alterations, reduce TEER values and decrease ZO1 and CDH1 gene transcription. This is accompanied by the activation of pro-fibrotic signalling pathways resulting in collagen increment, which often accompanies endometriosis-related alterations. Conclusion: The data obtained suggest MP ability to exert deleterious effects in vitro on human endometrium, with a possible negative impact on its functionality and receptivity.