Wildfire smoke particulate matter induces ovarian hyperandrogenism via aryl hydrocarbon receptor activation I
Wildfires have become more frequent and intense worldwide. Wildfire smoke particulate matter (WFPM) can be more toxic than urban background PM due to nanosized PM or WFPM0.1 and more polar organic compounds including polycyclic aromatic hydrocarbons (PAHs). While WFPM has been linked to cardiopulmonary diseases, its impact on female reproduction remains elusive. Here, we used an in vivo mouse intratracheal exposure model and a 3D ovarian follicle culture system, together with molecular, transcriptomics, and computational analyses, to examine the effects of lab-synthesized (LS) and Canadian real-world WFPM0.1 (C- WFPM0.1) on ovarian functions. Intratracheal exposure to LS-WFPM0.1 disrupted estrous cycles and elevated serum estradiol and testosterone concentrations in young adult female mice. RT-qPCR and single-follicle RNA-sequencing (RNA-seq) analysis analysis revealed altered steroidogenic genes, transcriptomic changes, and activation of aryl hydrocarbon receptor (AhR) in antral follicles of from LS-WFPM0.1-treated mice. In vitro exposure revealed thatto LS-WFPM0.1 increased testosterone secretion and induced genes related to androgen synthesis and AhR. Single-follicle and single-oocyte RNA-seq analysis identified differentially expressed genes (DEGs) related to inflammation in somatic cells and mitochondria and cell cycle in oocytes. Both real-world C-WFPM0.1 from the 2023 Canadian wildfires and benzo[a]pyrene, a high molecule weight PAH, reproduced these ovarian defects caused by LS-WFPM0.1. Mechanistically, AhR inhibition reversed hyperandrogenism induced by WFPM0.1. Together, our findings demonstrate that PAH-containing WFPM0.1  perturbs ovarian steroidogenesis and induces hyperandrogenism through AhR activation. These results are crucial for developing strategies to protect women's reproductive health and tailor guidelines for women seeking for infertility treatment during wildfire seasons. Overall design: SMART-Seq2 profiling of single oocyte extracted from follicles treated with vehicle or LS-WFPM0.1 using 3D encapsulated in-vitro follicle growth (eIVFG) system extracted on 6th day of culture