Inflammasome-targeted therapy might prevent adverse perinatal outcomes of recurrent chronic intervillositis of unknown etiology

Abstract

Chronic histiocytic intervillositis of unknown origin (CHI) is a rare placental disorder associated with adverse pregnancy outcomes, frequent recurrence, and a lack of effective preventive strategies. Recent insights indicate a potential link between CHI-associated inflammatory lesions and the inflammasome pathway, suggesting innovative therapeutic avenues. Here we show a potential role of the inflammasome pathway in CHI through comprehensive transcriptomic analysis of grade 2 or 3 histopathologic CHI samples, paired with placental controls. Additionally, we present case studies of three individuals with recurrent CHI, who have undergone treatment with anakinra and colchicine throughout pregnancy, resulting in improved perinatal outcomes. Notably, all cases are characterized by the birth of healthy, full-term infants, with reduced or absent intervillositis recurrence. Placental assessment unveils heightened activation of the NLRP3-PYCARD inflammasome pathway and IL-1β processing in CHI samples, with downregulation observed in treated pregnancy samples, devoid of intervillositis. Collectively, these findings suggest a potential therapeutic role for targeting the inflammasome pathway in preventing recurrent CHI in pregnant individuals.

Fig. 1. Transcriptomic Profiling of the Inflammasome Pathway in CHI Placentas.

A Principal component analysis (PCA plot) of the placental transcriptomes. The PCA plot reveals a significant separation between the controls (CTRL) and CHI placentas (Patient). B Top canonical pathways upregulated in CHI. In red, canonical pathways involved in innate immunity, macrophage activation and inflammasome pathway. C Volcano plots identifying differentially expressed genes between CHI and controls. Genes involved in the inflammasome pathway are represented. D. Heatmap representation of inflammasome-related gene expression, organized by hierarchical clustering, depicting differences between healthy controls (n = 6) and CHI patients (n = 18). E–J Box-whisker plots of transcriptomic analysis reveals the log2 expression levels of key components involved in the inflammasome pathway: NLRP3, PYCARD, CASPASE-1, MEFV, IL-1β, and IL-18, respectively, in comparison between healthy controls and patients afflicted with CHI. K–M Box-whisker plots of transcriptional signature of the inflammasome pathway, IL-1β, and IL-18, respectively, across these groups. The horizontal line in each box is the median. The lower and upper ends of each box are limits of the first and third quartiles, and height of each box is the interquartile range. Statistical analysis was conducted using GraphPad Prism 9. P values between each group were determined by a Mann-Whitney U test; *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. All tests were two sided.

Fig. 2. Obstetrical treatment chronology across patients’ obstetric histories.

A–C depict the comprehensive obstetrical treatment timelines for each patient. HCQ (Hydroxychloroquine), IUGR (Intrauterine Growth Restriction), IV (Intravenous), CHI (Chronic histiocytic intervillositis), LDA (Low-Dose Aspirin), LMWH (Low Molecular Weight Heparin), PRED (Prednisone), TOP (Termination of Pregnancy), and WG (Week of Gestation).

Fig. 3. Placental histological analysis and immunohistochemistry staining in patients diagnosed with CHI and treated with Inflammasome Blockade strategy.

Stainings were repeated on multiple different sections of the placental samples, and the most representative data are presented (scale-bar: 200μ). Panels A1 and B1 present microscopic placental features from Patient 1 (A1) and Patient 2 (B1), both diagnosed with CHI. Hematoxylin-eosin-saffron staining of placental tissue reveals the presence of macrophages (magnification: x100). Insets provide a closer view, highlighting histiocytic infiltration through CD68 immunostaining. Panels A2 and B2 display microscopic placental features from the consecutive pregnancies of Patient 1 (A2) and Patient 2 (B2), following treatment with anakinra and colchicine. Hematoxylin-eosin-saffron staining of placental tissue reveals limited lesions associated with vascular malperfusion, with an absence of CHI-related lesions (magnification: x100). Insets provide an amplified view, emphasizing the very limited histiocytic infiltration through CD68 immunostaining. Panel C (1–4) showcases placental immunohistochemistry staining using anti-NLRP3 antibodies for Patient 1, diagnosed with CHI (C1), and after undergoing treatment with an inflammasome blockade strategy (C3). Panels C2 and C4 serve as term-matched controls for C1 and C3, respectively (magnification: x100). Panel D (1–4) illustrates placental immunohistochemistry staining with anti-PYCARD antibodies for Patient 1, diagnosed with CHI (D1), and following treatment with an inflammasome blockade strategy (D3). Panels D2 and D4 function as term-matched controls for D1 and D3, respectively (magnification: x100).