Vaginal Microbiota, Genital Inflammation and Extracellular Matrix Remodelling Collagenase: MMP-9 in Pregnant Women With HIV, a Potential Preterm Birth Mechanism Warranting Further Exploration

Abstract

BackgroundPregnant women living with HIV infection (PWLWH) have elevated rates of preterm birth (PTB) in which HIV and cART are implicated. PWLWH also have a high prevalence of adverse vaginal microbiota, which associate with genital tract inflammation. The mechanism underlying PTB in PWLWH is unknown. We present the first data in PWLWH on genital-tract matrix-metalloproteinase-9(MMP-9), an important collagenase implicated in labour onset, and tissue inhibitor of metalloproteinases-1(TIMP-1) and explore correlations with local inflammation and vaginal bacteria.Material and MethodsCervical vaginal fluid (CVF) collected by a soft cup and high vaginal swabs (HVS) were obtained from PWLWH and HIV uninfected pregnant women (HUPW) at three antenatal time points. Maternal characteristics, combination antiretroviral therapy (cART) exposure, and pregnancy outcome were recorded. Concentrations of MMP-9, TIMP-1 and ten cytokines were measured by immunoassays. Vaginal microbiota composition was determined through 16S rRNA amplicon sequencing. MMP-9, TIMP-1 and cytokine concentrations were compared by HIV status, cART, and prematurity and in PWLWH correlations with polymorphonuclear leucocytes, cytokines and bacterial genera were explored.ResultsCVF was available for 50 PWLWH (108 samples) and 12 HUPW (20 samples) between gestation weeks 14-38. Thirty-six PWLWH conceived on cART and 14 initiated post-conception. There were five and one PTB outcomes in PWLWH and HUPW respectively. PWLWH had higher mean CVF concentrations of MMP-9 (p<0.001) and TIMP-1 (p=0.035) in the second trimester compared with HUPW with a similar trend in the third trimester. PWLWH also had higher CVF values of cytokines: IL-1β, IL-8, IL-12 and TNF-α in both trimesters compared to HUPW (p ≤ 0.003). In PWLWH, MMP-9 positively correlated with TIMP-1 (r=0.31, p=0.002) and CVF polymorphonuclear leucocytes (r=0.57, p=0.02). Correlations were observed between MMP-9 and three cytokines: IL-1β (r=0.61), IL-8 (r=0.57) and TNF-α (r=0.64), p<0.001, similarly for TIMP-1. Abundance of anaerobic pathobionts correlated with MMP-9: Gardnerella (r=0.44, p<0.001), Atopobium (r=0.33, p=0.005), and Prevotella genera (r=0.39, p<0.001). Conversely proportion of Lactobacillus genera negatively correlated with MMP-9 (rho=-0.46, p<0.001). MMP-9/TIMP-1 ratio increased with gestational age at sampling in PWLWH, but this was no longer significant after adjusting for confounders and no difference by prematurity was observed in this sub-study.ConclusionsHere we show strong correlations of MMP-9 to genital tract inflammation and sub-optimal bacterial genera in PWLWH indicating the ascending genital tract infection pathway may be a contributory mechanism to the high risk of PTB.

Interactions between microbiota and cervical epithelial, immune, and mucus barrier

“…The potential mechanisms by which bacterial infections affect cervical remodelling mainly involve metalloproteinases. G. vaginalis, A. vaginae, P. bivia, and P. asaccharolytica can induce or secrete MMP-1, 9 and 10, which shows the ability to degrade collagen (type I and IV), gelatin, casein, and fibrinogen (Łaniewski and Herbst-Kralovetz, 2021;McGregor et al, 1986;Łaniewski and Herbst-Kralovetz, 2021;Short et al, 2021;Tantengco et al, 2021a), while L. crispatus has no effect on type I collagen, casein, and fibrinogen, which inhibits clot formation (Lithgow et al, 2022). The colonisation of the mouse reproductive tract by G. vaginalis increases mucin expression, dispersion of collagen fibres, and alters cervical biomechanical properties which indicates a more rapid cervical remodeling (Sierra et al, 2018).…”

Matrix metalloproteinase-induced cervical extracellular matrix remodelling in pregnancy and cervical cancer

“…An altered vaginal microbiota with depleted lactobacilli and overgrowth of pathobionts may attract immune cells such as neutrophils and macrophages which release MMPs. The pathway of sub-optimal vaginal microbiota, genital tract inflammation, release of MMP-9 by polymorphonuclear leucocytes, ascending genital tract infection promoted by MMP-induced cervical ECM degradation and subsequent PTB have been suggested in pregnant women living with HIV infection ( Short et al 2021 ). That is, during pregnancy, the trigger for MMP release may be vaginal dysbiosis and resultant host immune response.…”

“…Instead of complement activation on macrophages, there is an increase in MMP-9/TIMP-1 ratio that correlates with dominance of pathogenic anaerobes, increase in IL-1β, IL-8 and TNF-α, and polymorphonuclear leucocyte counts in a positive feedback fashion. MMP-9 may be released by both neutrophils and macrophages ( Short et al 2021 ) and not macrophages alone.…”

“…For instance, in normal pregnancy/labour, the MMP/TIMP ratio is usually balanced with no angiogenesis. However, disrupted MMP/TIMP ratios in favour of MMPs and angiogenesis are common in cervical neoplasia ( Table 1 ) and vaginal dysbiosis-induced MMP release during gestation ( Short et al 2021 ). CIN/cancer-associated vaginal microbiota may be useful in predicting the risk of HPV-related diseases and guiding treatment strategies ( Norenhag et al 2020 ).…”

¿Son útiles los antimicrobianos en pacientes con trabajo de parto prematuro, espontáneo, membranas intactas e infección bacteriana ascendente? Una revisión narrativa

“…a) Estudios aclaratorios, que el uso de antimicrobianos en el PP con MI, asociados con infección/inflamación no producen daños a corto y largo plazo en los niños/ niñas. b) Más y mejores estudios centrados en la detección precoz de la infección subclínica a nivel cervico-vaginal, aunque ya existen marcadores sensibles de infección a ese nivel, como IL-6 21 , MMP-9 81 , técnica de Nugent para diagnóstico de VB, aumento en el recuento de LPM > de 10 por campo 400x 22,25 . c) Más revisiones sistemáticas y meta-análisis de ECAs, para determinar si las mujeres con IMCA o aquellas solo con endocervicitis pueden beneficiarse con la administración de antimicrobianos.…”