Uterine defence mechanisms in mares resistant and susceptible to persistent endometritis: a review

Expression of indoleamine 2,3-dioxygenase 1 as transcript and protein in the healthy and diseased equine endometrium

The enzyme indoleamine 2,3-dioxygenase 1 (IDO1) acts immunomodulatory and restricts bacterial growth. In the uterus of women and mice, it likely contributes to tissue homeostasis and disease pathogenesis. Pregnancy failure in mares is often caused by endometritis and endometrosis. The pathogenesis of nonsuppurative endometritis and endometrosis is still uncertain. To the authors' knowledge, no information on IDO1 expression in the equine endometrium is published. Aim of this study was to examine the presence of IDO1 as transcripts and proteins in the healthy and diseased endometrium of 25 mares and to determine its cellular expression. By PCR, IDO1 transcripts were detected in healthy (3 mares) and diseased endometria (22 mares). Western blot on 15 samples showed the concurrent presence of IDO1 proteins. Immunohistochemistry revealed its expression in macrophages and epithelial cells. Endometria of 21 mares showed an intense staining of glandular epithelia, whereas glands of the remaining 4 mares were negative or contained only few positive cells. Tissue samples of all mares showed a minimal to mild IDO1 expression in the surface epithelium and glandular ducts. Quantification of immunohistochemistry on biopsies of 6 mares collected at different stages of the same endometrial cycle indicated that the IDO1 expression is not influenced by the endometrial cycle. This study confirmed IDO1 expression also in the equine endometrium and suggests an immunomodulatory role of uterine macrophages and epithelial cells. A markedly reduced glandular IDO1 expression as detected in 4 mares may be associated with alterations of uterine immune defenses.

The contribution of complement to opsonic activity in the uterine secretions of mares free of endometritis

The aim of the present study was to investigate if complement contributes to opsonic activity in the uterine secretions of mares with normal reproductive functions. Five mares with a mean age of 9 years were used in the study. The mares were considered to be free of endometritis based upon clinical history, palpation per rectum and ultrasonogaraphy of the genital tract, videoendoscopic inspection of the uterus, electronmicroscopy of endometrial biopsies, and bacteriological and cytological examination of swabs from the endometrium. The hormonal status of the mares was also determined. Uterine secretions were collected by a tampon inserted into the uterus during estrus. Secretion and serum samples were divided in half, one half of which was subjected to heat treatment (56 degrees C in 30 minutes) in order to inactivate the complement. Opsonic activity in the samples was then determined in a chemiluminescence assay using zymosan as the target particle. Opsonic activity was expressed as peak chemiluminescence and the time to peak chemiluminescence. Heat treatment of the secretions reduced peak luminescence significantly (P<0.01), and it prolonged the time to peak luminescence significantly (P<0.05). These data show that complement contributes a considerably to opsonic activity in uterine secretions prior to an inflammatory response in the equine uterus.

Endometrial explant culture for characterizing equine endometritis

PROBLEM

Endometritis after insemination is ubiquitous in the horse and is associated with semen and/or bacteria in the uterus. In up to 40% of horses, inflammation persists causing infertility. An endometrial explant culture was developed to study uterine secretion of prostaglandin F(2alpha) (PGF(2alpha)) in response to physiological and pathological challenge.

METHOD OF STUDY

Uteri were collected from mares, the endometrium dissected and explants from the uterine body or horn cultured in William's or RPMI medium. The response of explants to oxytocin, semen or bacteria compared to untreated tissue was tested by collecting medium after 24 and 72 hr and measuring PGF(2alpha) by radioimmunoassay.

RESULTS

Explants from the uterine horn and cultured in William's medium secreted the most PGF(2alpha) after challenge with oxytocin. Explants treated with semen produced a PGF(2alpha) response after 72 hr. Explants collected from mares in the transition season treated with killed S. zooepidemicus or E. coli lipopolysaccharide (LPS) secreted increased concentrations of PGF(2alpha) after 24 and 72 hr. The response to LPS was inhibited by polymyxin B. Follicular and luteal phase explants did not respond to treatments.

CONCLUSIONS

An endometrial explant culture was developed that measured PGF(2alpha) and may be used to study endometritis.

Common procedures in broodmare practice: what is the evidence?

Many procedures performed as part of routine broodmare practice are based on sound clinical judgment and experience or scientific evidence; however, others are based on perceived problems and needs to address them. This article presents four procedures commonly used in broodmare practice, for which there is questionable evidence to substantiate their use.

Use of leukocytes as treatment for endometritis in mares experimentally infected with Streptococcus equi subsp. zooepidemicus

This study compared four treatments for bacterial endometritis in mares experimentally infected with Streptococcus zooepidemicus. Twenty-five mares were used, 20 resistant and five susceptible to endometritis. Mares would be in estrus when infected. Twenty-four hours after inoculation, clinical, bacteriological and cytological examinations were performed and repeated until the first occurrence: negative cytology and no Streptococcus growth or the seventh day post-infection. All mares showed clinical signs of endometritis and were assigned to one of the following treatments: (1) intrauterine infusion of fresh leukocytes; (2) intrauterine infusion of frozen-thawed leukocytes; (3) intrauterine infusion of lysed leukocytes; (4) intrauterine infusion of recombinant human interleukin-8 (rhIL-8); (5) control. Mares were submitted to all treatments, with at least a 14-day interval between treatments in a Latin square design. Treatment did not affect (P=0.121) time needed for resistant mares to eliminate bacteria. Time needed for elimination of bacteria was similar in susceptible mares treated with fresh and frozen leukocytes (P=0.333). Susceptible mares treated with frozen leukocytes also did not differ from those treated with lysed leukocytes (P=0.227) for time to eliminate bacteria, but were significantly different (P>0.02) from those treated with rhIL-8 and control. In resistant mares, physical clearance ability was probably the responsible for bacterial elimination. Intrauterine infusions in susceptible mares with viable or lysed leukocytes associated or not to opsonizing factors, reduced the time to elimination of bacteria. Infusions with bactericidal effect (functional neutrophils and granules) was likely effective and responsible for the more rapid elimination of bacteria in susceptible mares.

Degenerative Endometrial Changes do not Change the Functional Capacity of Immigrating Uterine Neutrophils in Mares

An endometritis model was used to investigate the influence of degenerative endometrial changes (endometrosis) on functional parameters of uterine neutrophils in the horse. Six hours after intrauterine application of recombinant human interleukin-8 (rhIL-8), the uteri of 15 mares were flushed with phosphate-buffered saline. Quantitative and qualitative flow cytometric assays were then made to determine the absolute numbers, viability, phenotype, generation of reactive oxygen species (ROS), and phagocytic activity of immigrated polymorphonuclear neutrophilic granulocytes (PMN). Recombinant hIL-8 attracted similarly high numbers of similarly viable PMN into the uteri of mares with or without degenerative endometrial changes. Compared with blood PMN, immigrated uterine neutrophils displayed significantly upregulated expression of CD11a/CD18 (LFA-1) on uterine PMN whereas major histocompatibility complex class I molecules were expressed at lower densities. The ability to phagocytose opsonized streptococci did not differ between uterine and blood PMN. However, uterine PMN displayed a higher capacity to generate ROS. On average, uterine PMN of mares with degenerative endometrial changes showed phenotypical and functional characteristics similar to those of mares with a histologically healthy endometrium. Therefore, degenerative endometrial changes per se did not reduce the functional capacity of equine uterine neutrophils in mares.

Post-breeding endometritis in the mare

Post-breeding endometritis is a major cause of subfertility in the mare. Endometritis is a normal event in the immediate period after mating, but the presence of ultransonographically visible uterine fluid more than 12 h later is thought to be evidence of uterine pathology. In mares that are free of venerally transmitted endometritis, treatment is aimed at removing the intraluminal fluid. If the endometritis persists past day 5, when the embryo enters the uterine lumen, the cytotoxic environment will not be compatible with pregnancy. Reproductive anatomy, defective myometrial contractility, lowered immune defences, overproduction of mucus, inadequate lymphatic drainage, or a combination of these factors will predispose the mare to post-breeding endometritis.

Concentrations of total protein, albumin and immunoglobulins in undiluted uterine fluid of gynecologically healthy mares

Undiluted uterine fluid from 20 Warmblood/Standardbred mares (5 to 14 yr old) was recovered by absorption to an intrauterine tampon. The mares were considered gynecologically healthy based on a clinical examination including uterine swabs for cytology and bacteriology as well as endometrial biopsy examinations. The protein profiles (SDS-PAGE) and concentrations of total protein, albumin, and immunoglobulins (Ig) A and G in the uterine fluid were examined and compared with the same proteins in serum. Major peaks were identified on the obtained protein profiles, and there was a clear similarity between the serum profiles and uterine fluid profiles. Variability in protein concentrations among mares was considerably larger in uterine fluid than in serum. Concentrations of the various proteins in uterine fluid were 44 to 56% of those in serum, except for IgA, which had a similar concentration in both serum and uterine fluid. Concentration of the proteins corresponding to peak No. 3 (molecular weight 60 to 71 kDa) in uterine fluid was higher (P < 0.05) in younger mares than in older ones. Parity had no effect on the recorded protein concentrations. The present study of gynecologically healthy mares showed that there is a large individual variation in the protein composition of uterine fluid. The results suggest that age, but not parity, may affect this composition, and indicate further that there is considerable transudation to the uterine cavity.

Lymphocyte subsets in the endometrium of genitally normal mares and mares susceptible to endometritis

The density and distribution of MHC Class II positive cells and subpopulations of lymphocytes were studied in the endometrium of genitally normal mares and mares susceptible to endometritis. In genitally normal mares, more MHC Class II positive cells were present in the epithelium and stratum compactum during oestrus than dioestrus. Significantly more CD4+ and CD8+ lymphocytes were present in the stratum compactum than in the stratum spongiosum. CD4+ lymphocytes were present in greater numbers than CD8+ lymphocytes in the stratum compactum but approximately equal numbers were present in the stratum spongiosum and in lymphoid aggregates. Occasional CD4+ and CD8+ cells were seen in the luminal and glandular epithelium. Infrequently, B cells were present in the endometrium and were not observed in the epithelium. Numbers of T and B cells did not appear to be affected by cycle stage. In mares with endometritis, the densities of CD4+, CD8+ and B cells were significantly increased. Large aggregates of lymphoid cells which contained approximately twice as many CD4+ cells as CD8+ cells were present in the endometrium of these mares and all 3 subclasses of lymphocyte were seen occasionally in luminal and glandular epithelium.

Investigation of association between alpha-1 proteinase inhibitor haplotype and endometritis in the thoroughbred mare

Failure to inhibit proteinases can lead to excessive tissue damage. The possibility that the severity of endometritis in Thoroughbred mares correlates with the haplotypes of plasma alpha 1-proteinase inhibitor (alpha 1-PI) expressed was investigated in two groups of mares. In mares with pyometritis before treatment, the frequency of the N haplotype, which is already high in the Thoroughbred population, was significantly increased when compared with that in a large published population. In mares with acute endometritis which persisted after treatment followed by sexual rest, the absence of S and T haplotypes was significant, suggesting that, when present, they may have a protective function.

Evaluation of progesterone treatment to create a model for equine endometritis

To investigate a model for equine endometritis, 12 mares with normal reproductive tracts were divided into 2 groups. All mares received progesterone in oil, 250 mg im, daily. At 5 days after initiation of progesterone administration, the uteri were inoculated with 10(6) colony forming units of Pseudomonas aeruginosa. The day of inoculation was designated Day 0. On Day 6, endometrial swab samples yielded P. aeruginosa in 5 mares; samples from the other 7 mares yielded heavy growth of Escherichia coli, Streptococcus zooepidemicus, Klebsiella pneumoniae, Enterobacter spp., Citrobacter diversus, Staphylococcus epidermidis and Streptococcus morbillorum. On Days 6, 7 and 8, Group A mares received intrauterine infusions of 6 g ticarcillin disodium and 0.2 g clavulanate potassium in 100 ml sterile saline. Group B mares received infusions of saline only. The incidence of swab specimens yielding no bacterial growth was significantly higher in Group A than Group B mares on Days 8 and 13 (4/6 vs 0/6). Swab samples from 5 of the 6 mares in Group A yielded growth of fungi on Days 13 and 19. Mares in Group B were then similarly treated with ticarcillin/clavulanate infusions, on Days 19, 20 and 21. The incidence of swab specimens yielding no bacterial growth was 2/6 and 1/6 on Days 21 and 26, respectively; fungi were not recovered from these mares at any time. The incidence of no-growth swabs after antibiotic treatment tended to be higher in Group A and incidence of fungal recovery after antibiotic treatment was significantly higher in Group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Bovine endometritis: current and future alternative therapy

Abnormal parturition can be followed by a persistent endometritis which can have deleterious effects on the cow's subsequent reproductive performance. Normal and active uterine defense mechanisms have been reported to be very important for the exclusion of bacterial infection from the uterus and recovery from endometritis developing after parturition. Despite the widespread use of local or systemic antibiotics, antiseptics, sulfonamides and hormones, rates of recovery from endometritis and the cow's subsequent fertility have not increased appreciably. Furthermore, the cost of any treatment, the frequency of its administration and the milk disposal after treatment make their use uneconomic. Alternative therapies which stimulate the natural uterine defense mechanisms have been suggested as treatments of bovine endometritis. These include: (I) Endotoxins such as lipopolysaccharide of E. coli, (II) serum, plasma or hyperimmune serum, (III) polymorphonuclear leucocyte (PMN) extracts and components and (IV) granulocyte-macrophage colony stimulating factors (G-M CSF).

Endometritis in the mare: A comparison between reproductive history and uterine biopsy as techniques for predicting susceptibility of mares to uterine infection

Thirty mares with no clinical signs of endometritis were categorized as being susceptible or resistant to uterine infection depending on whether or not they had a history of recurrent endometritis. The same mares were then independently classified as susceptible or resistant on the basis of their uterine biopsies; those with significant endometrial degeneration were considered to be susceptible to endometritis. The mares then received an intrauterine inoculation of pathogenic Streptococcus zooepidemicus . Those mares which eliminated bacteria by 10 d after inoculation were considered truly resistant to endometritis, whereas those still infected at 10 d were considered susceptible. The original classifications based on history or biopsy were compared to the inoculation results. A history of recurrent endometritis provided a more sensitive (0.90) and specific (0.95) indication of susceptibility to uterine infection than a uterine biopsy with significant endometrial degeneration (sensitivity 0.5, specificity 0.75).