Proteomic analysis of preovulatory follicular fluid reveals differentially abundant proteins in less fertile dairy cows

• Dairy cows suffer from low fertility which could be related to follicular function.
• This is the first description of the proteome of pre-ovulatory follicles in cows.
• Higher follicular estradiol suggests of accelerated growth in less fertile cows.
• Differential abundance of 8 relevant proteins was found in less fertile cows.
• These proteins could influence follicular function and should be further examined.

The follicular fluid (FF) proteome can provide an indication of follicular quality. High-yielding dairy cows suffer from low fertility, which could be related to follicular function. However, the proteome of preovulatory follicles has never been described in cows. Our objectives were to: 1) define the bovine preovulatory FF proteome, and 2) examine differentially abundant proteins in FF of controls (CTL, n = 10) and less fertile cows (LFC; failed to conceive following ≥ 6 inseminations, n = 8). Follicles ≥ 7 mm in diameter were aspirated in vivo, and estradiol (E2) and progesterone (P4) were examined. The FF from 10 preovulatory follicles (E2/P4 > 1) was analyzed; E2 was higher and follicle diameter tended to be larger in LFC. As aspirations were conducted at a fixed time, this suggests accelerated follicular growth in LFC. The 219 identified and quantified proteins consisted mainly of binding proteins, proteases, receptor ligands, enzymes and transporters. Differential abundance of 8 relevant proteins was found in LFC compared to CTL: SERPINA1, TIMP2, ITIH1, HSPG2, C8A, COL1A2, F2, and IL1RAP. These proteins could influence follicular function—e.g., decreased SERPINA1 may be related to accelerated follicular growth—and therefore, further examination of their roles in the etiology of LFC is warranted.SignificanceHigh yielding dairy cows suffer from infertility that leads to major economic losses worldwide. In Israel, about 30% of dairy cows fail to conceive following ≥ 4 inseminations. The etiology of this low fertility is multifactorial and remains a serious challenge. Follicular fluid proteome can provide indication to follicular quality, yet the proteome of pre-ovulatory follicles has not been described in cows. This work examined the differential abundance of proteins in less fertile dairy cows compared to controls, and found 8 relevant novel proteins that could influence follicular function. The role of these proteins in the etiology of less fertile cows should be further examined.

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