Cytidine deaminase Apobec3a induction in fallopian epithelium after exposure to follicular fluid

Abstract

Objective Ovarian carcinomas that originate from fallopian epithelial cells are suggested to arise due to repeated exposure to ovulatory follicular fluid (FF). Mechanistic explanation(s) for how this occurs are unknown. Here, we sought to understand if FF exposure to fallopian epithelial cells could induce DNA damage and expression of a known family of DNA mutators, apolipoprotein B mRNA editing enzyme, catalytic polypeptide (APOBEC) cytidine deaminases. Methods Follicular fluid and matched patient plasma samples were obtained from donors. Fallopian epithelial cells (FT33-TAg, FT189, FT190, and FT194) were cultured with FF or plasma for 24 hr, and cell proliferation and DNA damage were assessed. Effects of FF on Apobec gene expression was determined by qRT-PCR and western blot analyses. Fallopian epithelial cells were transfected with an APOBEC3A expression vector and DNA damage was assessed. Results Follicular fluid exposure increased epithelial cell proliferation as measured by three independent methods, and DNA damage accumulation as assessed using three independent measures. This effect was specific to FF, as matched patient plasma did not have the same effects. Increased expression of Apobec3a was observed in fallopian epithelial cells following exposure to 5 of 8 patient FF samples, and transient overexpression of APOBEC3A was sufficient to induce double strand DNA breaks. Conclusions Follicular fluid can induce cell proliferation and DNA damage accumulation in cultured fallopian epithelial cells. Increased expression of APOBEC3A, a known DNA mutator, may explain the high incidence of DNA damage after FF exposure. The role of Apobec3a in ovulation-induced inflammation warrants further investigation.

Cellular models of development of ovarian high‐grade serous carcinoma: A review of cell of origin and mechanisms of carcinogenesis

“…41 It was later noted that without a tearing, fallopian tube fimbria, bathed by follicular fluid (FF) during oocyte catch up, is also vulnerable to ovulation injury, such as inflammation and DNA damage. [42][43][44][45] Eventually, the focus turned to the contents in the FF that bath both the ovulatory wound and FTE after ovulation. FF contains high concentrations of growth factors, proteinases involving coagulation cascades and others, extracellular proteins, hormones, immune agents and reactive oxygen species (ROS).…”

“…Alternatively, the tear‐and‐repair hypothesis proposed by Fathalla 32 states a repetitive proliferation of the OSE after ovulation‐induced wounding, 40 which increases DNA damage and may enhance the transformation 41 . It was later noted that without a tearing, fallopian tube fimbria, bathed by follicular fluid (FF) during oocyte catch up, is also vulnerable to ovulation injury, such as inflammation and DNA damage 42‐45 . Eventually, the focus turned to the contents in the FF that bath both the ovulatory wound and FTE after ovulation.…”

WNT and inflammatory signaling distinguish human Fallopian tube epithelial cell populations

“…Consequently, the ovary-derived factors have long been suspected of promoting malignant transformation (Fathalla, 1971). More recent studies find that follicular fluid induces DNA damage and proliferation in TE (Brachova et al, 2017;King et al, 2011), and exposure to follicular fluid also induces changes in TE reminiscent of STICs (Bahar-Shany et al, 2014). Gene expression data from different human TE cell populations may aid in determining the immediate relevance of these observations to the human TE.…”

In vivo genetic cell lineage tracing reveals that oviductal secretory cells self-renew and give rise to ciliated cells

“…Exposure to pro-inflammatory follicular fluid can induce DNA double-strand breaks, as marked by phospho-γH2AX, in mouse oviductal epithelial cells (King et al, 2011) and in cultured human fimbrial epithelial cells and fimbria tissue (Huang et al, 2015). Using an ex vivo culture system, in which the fallopian tube epithelium was exposed to follicular fluid, an increase was observed in the expression of DNA repair pathway components and inflammatory-related genes (Bahar-Shany et al, 2014;Brachova et al, 2017). This could represent a key step in the process of premalignant transformation of fallopian tubal epithelium.…”