Innate immune molecules in preterm birth and disease

Abstract

Preterm labour is one of the leading causes of perinatal mortality and morbidity. Most premature babies die before the age of five, and if they survive they face a high risk of disabilities and impairments. SP-A and SP-D are pattern recognition, innate immune molecules that are responsible for the maintenance of pulmonary immunity and surfactant homeostasis. They have been localised in the human reproductive tract and implicated in pregnancy and the initiation of labour. We hypothesised that SP-A and SP-D could play an active role in the activation of the myometrium and the timing of parturition. In this study we investigated the effects of the recombinant forms of SP-A and SP-D (rhSP-A and rhSP-D) on contractile events in the myometrium. We validated the expression of surfactant proteins A and D in the in vitro model of myometrium cell line, ULTR, using qPCR, immunofluorescence and ImageStream technology. We demonstrate that rhSP-A and rhSP-D treatments led to an increase in cell motility and had an effect on the contractile response of ULTR cells when grown on collagen matrices showing reduced surface area. We studied this effect further by measuring the expression of contraction-associated protein genes. rhSP-A and rhSP-D led to an increase in the expression of oxytocin receptor and connexin 43. We reported that both rhSP-A and rhSP-D induce the secretion of pro-inflammatory cytokines, such as IL-6 and IL-8. We also propose a new model for functional progesterone withdrawal showing a cross-talk between progesterone (including non-genomic effects) and SP-A. Emerging evidence has linked shredding of the uterine wall with ovarian cancer cases, suggestive of an interaction between myometrium and ovaries. We investigated the effects of rhSP-D in ovarian cancer in vitro using SKOV3 cells as a model. Conditioned media from ULTRs treated with rhSP-D resulted in growth arrest of SKOV3. We also demonstrated that rhSP-D led to a decrease in cell motility and cell proliferation in these cells. This was followed by an inhibition of the mTOR pathway activity. We expanded on our observations by measuring expression of SP-A and SP-D in human myometrial samples as well as the expression of SP-D in human ovaries. Collectively, this study presents novel interactions of SP-A and SP-D at both myometrial and ovarian level, rendering them key molecules for conditions such as preterm labour as well as implicating them as therapeutic targets for ovarian cancer.