Antioxidant Defenses, Oxidative Stress Responses, and Apoptosis Modulation in Spontaneous Abortion: An Immunohistochemistry Analysis of First-Trimester Chorionic Villi

Abstract

Oxidative stress (OS) and apoptosis are critical factors in placental development and function. Their interplay influences trophoblast proliferation, differentiation, and invasion, as well as vascular development. An imbalance between these processes can lead to pregnancy-related disorders such as preeclampsia, intrauterine growth restriction, and even spontaneous abortion. Our study seeks to elucidate the associations between preventive antioxidant/protective OS response factors-glutathione (GSH), MutT Homolog 1 (MTH1), and apoptotic regulation modulators-tumor protein p53 and B-cell lymphoma (Bcl-2) transcripts, in the context of spontaneous abortion (30 samples) versus elective termination of pregnancy (20 samples), using immunohistochemistry (IHC) to determine their proteomic expression in chorionic villi within abortive fetal placenta tissue samples. Herein, comparative statistical analyses revealed that both OS response factors, GSH and MTH1, were significantly under-expressed in spontaneous abortion cases as compared to elective. Conversely, for apoptotic regulators, p53 expression was significantly higher in spontaneous abortion cases, whereas Bcl-2 expression was significantly lower in spontaneous abortion cases. These findings suggest that a strong pro-apoptotic signal is prevalent within spontaneous abortion samples, alongside reduced anti-apoptotic protection, depleted antioxidant defenses and compromised oxidative DNA damage prevention/repair, as compared to elective abortion controls. Herein, our hypothesis that OS and apoptosis are closely linked processes contributing to placental dysfunction and spontaneous abortion was thus seemingly corroborated. Our results further highlight the importance of maintaining redox homeostasis and apoptotic regulation for a successful pregnancy. Understanding the mechanisms underlying this interplay is essential for developing potential therapies to manage OS, promote placentation, and avoid unwanted apoptosis, ultimately improving pregnancy outcomes. Antioxidant supplementation, modulation of p53 activity, and the enhancement of DNA repair mechanisms may represent potential approaches to mitigate OS and apoptosis in the placenta. Further research is needed to explore these strategies and their efficacy in preventing spontaneous abortion.

Keywords: B-cell lymphoma (Bcl)-2 transcript; MutT Homolog 1 (MTH1) protein; autophagy; histopathology of the placenta; immunohistochemistry; miscarriage; molecular markers; reduced glutathione (GSH); spontaneous abortion; tumor protein p53 transcript.

Figure 1

First-trimester chorionic villi in hematoxylin–eosin (HE) staining: (a) 200×, mesenchymal villi, with diffuse stromal structure, containing thin collagen and reticulin fibers (black arrows), fibroblasts (blue arrows), scarce Hofbauer macrophages (yellow arrows), and rare fetal blood vessels (red arrows) encased within a peripheral trophoblastic epithelium, comprised of a well-defined cytotrophoblastic layer internally (green arrows), and a relatively thick, syncytiotrophoblastic layer externally (purple arrows); (b) 400×, villous sprouts and details regarding cellular morphology of cytotrophoblasts (green arrows) and syncytiotrophoblast (purple arrows).

Figure 2

Chorionic villi in hematoxylin–eosin (HE) staining (400×), demonstrating chorangiosis and accelerated villous maturation seen only in spontaneous abortion cases.

Figure 3

Targeted immunohistochemistry staining patterns encountered in chorionic villi from first-trimester fetal placentas: (A) 400×, increased, high intensity, trophoblastic nuclear reactivity; (B) 200×, low density, moderate intensity, trophoblastic nuclear positivity; (C) 400×, detail of negative chorionic villus; (D) 200×, high density, high intensity, trophoblastic cytoplasmic positivity; (E) 200×, very isolated, low-intensity, nuclear reactivity; (F) 200×, negative/control slide.

Figure 4

Comparative distribution of individual H-score values for all immunohistochemistry targets in the spontaneous abortion study group: p53—tumor protein p53; Bcl-2—B-cell lymphoma-2 protein; GSH—glutathione; MTH1—MutT Homolog 1 protein.

Figure 5

Paired comparison between expression of immunohistochemistry targets, i.e., p53—tumor protein p53; Bcl-2—B-cell lymphoma-2 protein; GSH—glutathione; MTH1—MutT Homolog 1 protein, within the spontaneous abortion study group: (A) difference between means for p53 vs. GSH; (B) difference between means for Bcl-2 vs. MTH1; (C) difference between means for Bcl-2 vs. GSH; (D) difference between means for p53 vs. MTH1. ns = non-significant. The power of statistical significance was marked on the charts with asterisks, with the number of asterisks directly parallel to the statistical power.

Figure 6

Representation of normality test results for the compared values (P53—tumor protein p53; Bcl-2—B-cell lymphoma-2 protein; GSH—glutathione; MTH1—MutT Homolog 1 protein), namely (a) predictive; (b) Gaussian dispersion.