Preterm birth (PTB), defined as delivery before 37 weeks of gestation (wg), affects approximately 10% of pregnancies worldwide and remains the leading cause of neonatal morbidity and mortality. Approximately 70% of PTBs occur spontaneously, either following the onset of preterm labor or due to premature rupture of the fetal membranes (PROM). An infectious etiology is identified in 25% to 40% of these cases, underscoring the significant role of inflammation in the pathophysiology of PTB. However, the lack of reliable biomarkers and effective therapeutic strategies continues to hinder both the prevention and clinical management of PTB.
Over the past twenty years, my team’s work has demonstrated the direct involvement of prokineticin-1 (PROK1), a canonical member of the prokineticin family, in various pregnancy-related pathologies. More recently, the team highlighted its role in the physiological mechanisms of term labor and hypothesized a key role for PROK1 in the diagnosis and treatment of preterm labor, paving the way for novel biomedical approaches based on its modulation. Specifically, we demonstrated that (i) circulating levels of PROK1 were significantly increased in patients developing preterm labor, (ii) PROK1 exerted a quiescent role prior to the onset of labor, (iii) its levels drastically decreased at labor onset, and (iv) it regulated the expression of proteins associated with parturition.
Based on these data, we hypothesized that PROK1 could serve as a relevant biomarker and/or a potential upstream regulator involved in the prevention of PTB. Thus, the objectives of my thesis project were: (i) to validate the diagnostic value of PROK1 in various biological fluids during pregnancy, notably amniotic fluid (AF) and maternal blood, using multiple distinctive cohorts; and (ii) to better understand the mechanism of action of PROK1 in the context of infectious PTB.
The implementation of my project relied on an integrated experimental approach combining, in vitro, ex vivo, in vivo, and in ovo studies.
Considering new clinical cohorts, I demonstrated a significant increase in PROK1 concentrations in the AF of patients at risk of PTB, particularly in cases of intra-amniotic infection; and an early increase in circulating PROK1 levels, from the first trimester, in patients presenting premature rupture of membranes (PROM), whereas PROK1 levels were significantly decreased in cases of preterm labor (PTL) with intact membranes. These observations reinforce the hypothesis that PROK1 plays a quiescent role during physiological pregnancy and strongly suggest a protective function against the risk of PROM. Concurrently, functional studies conducted in vivo (gravid mice), ex ovo (chicken embryo), and in vitro (human placental explants) demonstrated a protective effect of PROK1 in models of prematurity induced by lipopolysaccharide (LPS). Administration of PROK1 in mice significantly reduced the incidence of PTB and preserved placental integrity. This protection was confirmed in the ex ovo chicken embryo model, further strengthening the robustness of these findings. Analyses of oxidative stress, the interactome, and mitochondrial bioenergy performed on mouse placentas identified the mechanism of action of PROK1, involving modulation of sulfur metabolism (H₂S pathway) and mitochondrial function. Finally, in human placental explants, we demonstrated that PROK1 markedly attenuated LPS-induced inflammation and tissue damage.
In conclusion, my work demonstrates that PROK1 is a promising biomarker for spontaneous infectious PTB or PTB associated with PROM and may act as a preventive factor in cases of threatened PTB. These effects likely limit tissue damage through control of oxidative stress and modulation of bioenergetics and sulfur metabolism.​

Nadia ALFAIDY-BENHAROUGA

Tiphaine BARJAT​