Expanding the Gene Expression Profiling of Drug Transporters and Drug-Metabolizing Enzymes to Include the Upper Female Reproductive Tract

Background/Objectives: With the ongoing efforts in supporting the discovery of novel targeted drug delivery systems for the upper region of the female reproductive tract (FRT), it is imperative to understand the local drug disposition pathways. We aim to obtain a comprehensive profile of the drug transporters and drug-metabolizing enzymes in the human ectocervix, uterus, and fallopian tubes, as these factors may substantially influence mucosal penetration, tissue exposure, drug disposition, and the risk of drug–drug interactions. Methods: Gene expression of 12 drug transporters and 21 drug-metabolizing enzymes was quantified using RT-qPCR. Protein expression of highly expressed transporters was assessed using immunohistochemistry (IHC). Results: Among the 12 transporters analyzed, the efflux transporters P-gp, BCRP, and MRP4 exhibited the highest expression across the ectocervix, endometrium, myometrium, and fallopian tubes, with P-gp consistently showing the greatest abundance in all evaluated FRT tissues. Expression of these transporters was significantly higher (6–17×) in myometrium compared with ectocervix. IHC demonstrated strong localization of P-gp, BCRP, and MRP4 to epithelial layers facing the lumen, as well as to stromal and vascular endothelial cells. For drug-metabolizing enzymes, all 21 phase I and II enzymes were detectable across the FRT, and 15 were expressed at comparatively higher levels across all tissue types. These included CYP1A1, CYP1B1, CYP2B6, CYP2C8, CYP2C19, CYP3A4, UGT1A1, UGT1A3, UGT1A4, UGT1A7, UGT1A8, UGT1A10, UGT2B4, UGT2B15, and UGT2B17. Conclusions: The gene expression and localization data obtained from this work may improve our understanding of drug disposition in the FRT, which will inform selection, design, and optimization of drugs intended for targeted delivery within the FRT.