Experimental genital mycoplasmosis causes increased levels of mRNA for IL-6 and TNF-alpha in the placenta.
OBJECTIVE
Previous studies with animal models have shown that injection of lipopolysaccharide (LPS) results in fetal loss and increases production of proinflammatory cytokines at the maternal-fetal interface. Most intrauterine infections, however, are associated with Ureaplasma urealyticum, a microorganism that lacks a cell wall and therefore does not contain LPS. Previous work in our laboratory with an animal model for genital infection with a similar organism, Mycoplasma pulmonis, revealed that widespread infection in maternal and fetal tissues can be experimentally induced with minimal manipulation of the animal. For this project, we tested the hypothesis that administration of the organism by a hematogenous route at gestational day (gd) 14 would result in increased tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 production by the placenta.


METHODS
Timed-pregnant, Sprague-Dawley rats were anesthetized on gd 14 and 10(7) CFU of M. pulmonis strain X1048 or an equivalent volume of sterile medium was injected into the heart. Rats were necropsied on gd 18 or 21, and ex vivo production of TNF-alpha and IL-6 was evaluated from six randomly selected placentas from each litter. The remaining placentas were harvested and either snap-frozen or placed in formalin. Frozen placentas were processed for real-time reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of TNF-alpha and IL-6 mRNA. Formalin-fixed placentas were sectioned and stained with hematoxylin and eosin for lesion analysis.


RESULTS
Concentrations of TNF-alpha but not IL-6 were significantly higher in conditioned medium from placentas harvested from infected dams at gd 21. Levels of mRNA for IL-6 and TNF-alpha, however, were increased by M. pulmonis at gd 18 and 21. Analysis of gd 21 placentas by light microscopy revealed that significant histological chorioamnionitis was present in infected animals with accumulations of neutrophils in the capsular decidua.


CONCLUSIONS
These data indicate that experimental infection with M. pulmonis causes histological chorioamnionitis, elevated mRNA levels of TNF-alpha and IL-6 in placental tissues, and the secretion of TNF-alpha by the placenta during late gestation.
Peltier
Morgan R
MR
Department of Obstetrics, Gynecology and Reproductive Sciences, University of Medicine and Dentistry of New Jersey, New Brunswick, NJ 08901, USA. peltiemr@umdnj.edu
Brown
Mary B
MB
D000818:Animals; D002821:Chorioamnionitis / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D005260:Female; D007275:Injections, Intravenous; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D009175:Mycoplasma Infections / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D045803:Mycoplasma pulmonis / Q000276:immunology*; D010920:Placenta / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D048069:Tumor Necrosis Factors / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology
D015850:Interleukin-6; D012333:RNA, Messenger; D048069:Tumor Necrosis Factors