Oocyte CTR1 is not essential for cisplatin-induced oocyte death of primordial follicle

Abstract

Accumulated evidence indicates that cisplatin, a platinum-based alkylating agent, causes preferential DNA damage to oocytes of primordial follicles (PFs) in the ovary, suggesting oocyte-favored accumulation of cisplatin. Copper transporter 1 (CTR1; Slc31a1 ) is implicated in facilitating cisplatin uptake in cells. Here we found that oocytes of PFs had constitutively higher expression of CTR1 than other cell types in mouse ovary. However, oocyte-specific Slc31a1 knockout was not sufficient to prevent cisplatin-induced depletion of PFs in vitro . Our data indicate that CTR1 would not be the only route for cisplatin to be transported inside the oocytes of PFs in the ovary.

Figure 1. The distribution of CTR1 protein in the mouse ovary and effects of oocyte-specific Ctr1 knockout on ovarian reserve against cisplatin

A and B. CTR1 immunofluorescence assay on the mouse liver and ovary sections. C. Representative genotyping image of homozygous or heterozygous for the floxed Slc31a1 allele and Gdf9-iCre transgene. D. CTR1 immunofluorescence assay on ovary sections from wild-type or oocyte-specific Slc31a1 knockout mice. Zoomed pictures are located below each panel. The orange arrows for PFs from wild-type ovary indicate the expression of CTR1 in oocytes of PFs. The white arrows for oocytes of PFs exhibit the absence of CTR1 expression from oocyte-specific Slc31a1 knockout ovary. E. Representative image of H&E staining of ovary sections from oocyte-specific Slc31a1 knockout PD8 mice ex vivo cultured in the presence or absence of cisplatin ( cis -diamminedichloroplatinum(II), CDDP) for 96 hours. Green arrow, surviving PF; Yellow arrows, dead PFs. F. Total numbers of follicles (n=4). Scale bar for A, D, and E, 50 μm; Scale bar for B, 100 μm. *, p < 0.05.