This study reports no significant different however there is a slightly elevation of sFlt-1 immunostaining within the placental bed of a preeclamptic compared to normotensive pregnancies. This is an expected result as it is widely accepted that preeclampsia is associated with defective placentation (Fillion et al., 2021; Garrido-Gomez et al., 2017; Gui et al., 2020). More specifically, in PE the luminal diameter of spiral arteries remains of small caliber (Nobis et al., 2020; Sankar et al., 2013) hence the field area percentage of endothelial cells is lower. Moreover, trophoblast cells are absent within these non-physiologically converted spiral arteries in PE. We also report a significant decline of sFlt-1 immunostaining within spiral arteries of EOPE and LOPE (p < 0.0001) compared to the normotensive pregnant group. Of the two subtypes of PE (EOPE and LOPE), EOPE is associated with deficient trophoblast invasion together with the total absence of myometrial spiral artery remodeling (Pillay and Naicker, 2020).
This study also reports no significant difference with a decrease of PlGF immunostaining within the placental bed of PE compared to normotensive pregnancies. In comparison to sFlt-1, the intensity of immunoreactivity of PlGF was reduced across the study population. Of-note, PlGF is a pro-angiogenic molecule, therefore in the large flaccid remodeled spiral arteries of normotensive pregnancies, it is expected to have a larger surface area of endothelial cells compared to the non-physiological converted spiral arteries in the myometrium of PE. Previous literature has also demonstrated a reduction of PlGF in favor of sFlt-1 in PE compared to normotensive pregnancies, albeit within the placenta (Govender et al., 2013). Moreover, the absence of intramural trophoblast cells in PE supports our observed reduction of PlGF immunoreactivity. A notable decrease in PlGF immunostaining was noted in spiral arteries within the myometrium of normotensive pregnancies compared to EOPE (p = 0.4248) and an increase in LOPE (p = 0.1209) pregnancies. Among the two subtypes of preeclampsia EOPE serves as a paradigmatic manifestation of preeclampsia, highlighting the pivotal role of dysregulated angiogenesis in its pathophysiology (Cele et al., 2018). The notable increase in PlGF expression observed in EOPE compared to the normotensive group in our study may be linked to the abnormal morphology of the placental bed resulting from altered blood flow dynamics.
To our knowledge, this is the first study to report on the immunostaining of PlGF and sFlt-1 within the placental bed of pregnancies complicated by PE comorbid with HIV infection in women of African ancestry. sFlt-1 has been extensively investigated as a key protein that may be involved in the etiology or as a secondary phenomenon of PE within the placenta only as the placental bed is an invasive procedure (Maynard et al., 2003; Mcelwain et al., 2020).
Another main finding of the study was the non-significant elevation of sFlt-1 within the myometrium of the placental bed in the HIV + ve compared to HIV-ve (p = 0.1411), irrespective of pregnancy type. It is a standard of care procedure in SA for all HIV-infected women to receive ART and prophylaxis for the prevention mother to mother-to-child HIV transmission (PMTCT) (Akinsanya et al., 2017; Wessels et al., 2020). In contrast to sFlt-1, we report a similar immunoreactivity of PlGF between HIV -positive vs HIV-negative (p = 0.3042) group. Of-note ART serves to restore the immune response, ameliorating the potent pro-angiogenic effect of HIV(Isaguliants et al., 2021). HIV is a powerful pro-angiogenic factor due to the homology of shared lys-ala residue of its accessory protein Tat with the VEGF protein (Spector et al., 2019). Moreover, the HIV-1 accessory and matrix proteins are proponents for the dysregulation of hypoxia, apoptosis, oxidative stress, angiogenesis, and cell invasion (Mazzuca et al., 2018; Singh et al., 2023a). To-date, there is no available literature on the subcellular localization of sFlt-1 and PlGF within the placental bed of HIV-positive patients. The underlying mechanism behind the observed outcome requires greater clarity. Nonetheless, it is hypothesized that HIV infection may have a protective effect through mechanisms such as immune suppression or the strong resemblance of the HIV tat protein to VEGF (Singh et al., 2023b). Alternatively, the neutralisation may be insufficient within the heightened immune milieu of PE.
Across all groups, sFlt-1 levels were significantly down-regulated in normotensive HIV-negative women compared to EOPE HIV-negative women, suggesting an up-regulation of anti-angiogenic factors in EOPE. Conversely, EOPE HIV-negative women exhibited higher sFlt-1 levels compared to LOPE HIV-negative and LOPE HIV-positive women, indicating that sFlt-1 is more prominently involved in EOPE rather than LOPE, irrespective of HIV status. Notably, EOPE HIV-positive women showed higher sFlt-1 levels compared to LOPE HIV-negative and LOPE HIV-positive women, reinforcing the association of sFlt-1 upregulation with EOPE. Similarly, a significant increase in the immunoexpression PlGF was noted in EOPE HIV-positive women compared to LOPE HIV-positive and LOPE HIV-negative groups. Normotensive HIV-negative women exhibited lower PlGF levels compared to EOPE HIV-positive women, indicating that preeclampsia and HIV together may exacerbate angiogenic imbalance (Padayachee et al., 2019). HIV infection is known to affect angiogenic and downstream cell transduction pathways (Mtshali et al., 2020; Padayachee et al., 2019). HIV proteins, such as gp120, can induce endothelial cell apoptosis and dysregulate angiogenic factors, contributing to vascular complications (Mazzuca et al., 2018; Seeherman and Suzuki, 2021). HIV-related chronic inflammation and immune activation may further disrupt the angiogenic balance, potentially exacerbating preeclampsia symptoms. The interplay between HIV and angiogenic factors like sFlt-1 and PlGF in the placental bed highlights a complex mechanism where both viral infection and preeclampsia can lead to significant endothelial and placental dysfunction.
Despite no statistically significant difference noted between sFlt-1 and PlGF levels p = 0.8854, there is a slight increase in sFlt-1 compared to PlGF immunoexpression. Previous studies have highlighted the importance of the sFlt-1/PlGF ratio as a biomarker for diagnosing and predicting the severity of preeclampsia (Zeisler et al., 2016). An elevated sFlt-1/PlGF ratio, indicative of increased sFlt-1 or decreased PlGF levels, has been associated with adverse maternal and fetal outcomes in preeclampsia (Verlohren et al., 2010)). While the lack of a significant difference in our study's comparison may seem surprising, it highlights the complexity of angiogenic factor dynamics in preeclampsia. Factors such as gestational age, disease severity, and individual variations can influence sFlt-1 and PlGF levels, contributing to variability in their ratios. This finding suggests a potential imbalance or dysregulation in the sFlt-1/PlGF ratio, which is often considered a critical factor in the pathophysiology of preeclampsia (Oladipo and Jayade, 2024; Yagel et al., 2023). The sFlt-1/PlGF ratio is known to be altered in preeclampsia, with increased sFlt-1 and decreased PlGF contributing to the anti-angiogenic state associated with preeclampsia (De Oliveira et al., 2013; Gannoun et al., 2023). However, the lack of a statistically significant difference in this specific comparison in the preeclamptic group may imply variability within this cohort or a potential overlap in the ranges of sFlt-1 and PlGF values in this context.
We also report the following clinical demographics to be significantly different among the groups, maternal age (p < 0.0001), maternal weight p < 0.0221, systolic (p < 0.0001), and diastolic (p < 0.0001) pressures gestational weight (p < 0.0001) and gestational age (p < 0.0001). These findings suggest that these factors may have an impact on the development and severity of preeclampsia. Interestingly, there were no significant differences in terms of gravidity and parity between the study groups suggesting that the number of pregnancies or births may not be directly associated with the development of preeclampsia.