Expression of nerve growth factor and its receptors in the uterus of gilts with endometritis induced by infection with Escherichia coli.

Nerve growth factor (NGF) is a neurotrophin implicated in the pathophysiology of allergy, diseases of the immune system and inflammation. Expression of NGF and its receptors (TrkA and p75) has not been examined in inflamed uterine tissue. The aim of the present study was to evaluate the patterns of NGF, TrkA and p75 expression in normal and inflamed porcine uteri using real-time reverse transcriptase polymerase chain reaction (RT-PCR), western blotting and immunohistochemistry. On day 3 of the oestrous cycle, 50 ml of saline or 50 ml of Escherichia coli suspension containing 10(9) colony forming units/ml, was injected into both uterine horns of control (n = 10) and experimental (n = 10) gilts, respectively. Infected animals developed moderate or severe acute endometritis after 8 days and moderate acute or subacute endometritis after 16 days. On day 8 of the study, the expression of NGF and TrkA mRNA and protein was higher in the endometrium of gilts with endometritis than in normal tissue. NGF protein was also more prominently expressed in the endometrium of those animals with endometritis 16 days post infection. There was no difference in endometrial p75 mRNA and protein expression on either day. The myometrium of animals in both groups showed no difference in expression of any of the three molecules. Immunohistochemically, on day 8 there was greater expression of NGF and TrkA by the luminal epithelium and some glandular and endothelial cells as well as the myometrium of the uteri of gilts with endometritis compared with normal tissues. At day 16, there was greater expression of NGF by the luminal epithelium and of TrkA by some endothelial cells and the myometrium, compared with control tissue. There is therefore, up-regulation of NGF and TrkA mRNA and protein expression in the porcine uterus when affected by E. coli-induced inflammation. NGF and TrkA may have roles in this inflammatory process and/or in the innervation of the uterus.