Endometriosis in rhesus monkeys

Archimetrosis: the evolution of a disease and its extant presentation : Pathogenesis and pathophysiology of archimetrosis (uterine adenomyosis and endometriosis)

PURPOSE

This article presents a novel concept of the evolution and, thus, the pathogenesis of uterine adenomyosis as well as peritoneal and peripheral endometriosis. Presently, no unifying denomination of this nosological entity exists.

METHODS

An extensive search of the literature on primate evolution was performed. This included comparative functional morphology with special focus on the evolution of the birthing process that fundamentally differs between the haplorrhine primates and most of the other eutherian mammals. The data were correlated with the results of own research on the pathophysiology of human archimetrosis and with the extant presentation of the disease.

RESULTS

The term Archimetrosis is suggested as a denomination of the nosological entity. Archimetrosis occurs in human females and also in subhuman primates. There are common features in the reproductive process of haplorrhine primates such as spontaneous ovulation and corpus luteum formation, spontaneous decidualization and menstruation. These have fused Müllerian ducts resulting in a uterus simplex. Following a usually singleton pregnancy, the fetus is delivered in the skull position. Some of these features are shared by other mammals, but not in that simultaneous fashion. In haplorrhine primates, with the stratum vasculare, a new myometrial layer has evolved during the time of the Cretaceous-Terrestrial Revolution (KTR) that subserves expulsion of the conceptus and externalization of menstrual debris in non-conceptive cycles. Hypercontractility of this layer has evolved as an advantage with respect to the survival of the mother and the birth of a living child during delivery and may be experienced as primary dysmenorrhea during menstruation. It may result in tissue injury by the sheer power of the contractions and possibly by the associated uterine ischemia. Moreover, the lesions at extra-uterine sites appear to be maintained by biomechanical stress.

CONCLUSIONS

Since the pathogenesis of archimetrosis is connected with the evolution of the stratum vasculare, tissue injury and repair (TIAR) turns out to be the most parsimonious explanation for the development of the disease based on clinical, experimental and evolutionary evidence. Furthermore, a careful analysis of the published clinical data suggests that, in the risk population with uterine hypercontractility, the disease develops with a yet to be defined latency phase after the onset of the biomechanical injury. This opens a new avenue of prevention of the disease in potentially affected women that we consider to be primarily highly fertile.

Primate model research for endometriosis

Endometriosis is defined as the existence of endometrial tissue outside the uterine cavity, and it includes a chronic, inflammatory reaction associated with female infertility and pelvic pain. Endometriosis occurs in 7 to 10% of women. Although it has been studied for more than 50 years, the pathogenesis and development of endometriosis are still poorly understood. There is no curative therapy for endometriosis, which often recurs after surgical or medical treatment. There is a consensus that the adverse current of menstrual blood plays a crucial role in the development of endometriosis. This places a major limitation on research using rodent models of endometriosis, although these are still widely employed, because rodents do not menstruate and endometriosis does not occur spontaneously in these animals. In fact, menstruation and spontaneous endometriosis only occur in women and some non-human primates, making models that employ non-human primates the best animal models for research into the pathogenesis, pathophysiology, spontaneous onset, and treatment of endometriosis. This review assesses the effectiveness and potential of the non-human primate models of endometriosis. It also describes the current findings and theories on the pathogenesis of endometriosis that have been obtained by research using non-human primates.

Endometriosis: clinical monitoring and treatment procedures in Rhesus Monkeys

The National Institute on Aging (NIA) sponsored a workshop on September 8, 2004, to discuss the incidence, diagnosis, and clinical treatment of endometriosis in rhesus monkey colonies. Because of the growing number of aging studies using rhesus monkeys, this disease has become more prevalent as monkeys are living into advanced ages in captivity. The objective of the workshop was to gather information from various NIA-supported aging rhesus colonies on the incidence, clinical manifestations, indicators for early detection, and possible treatment options for endometriosis. Participants outlined a course of action for the effective management of this disease that would best maintain the integrity of long-term aging studies.

Genomic alterations in the endometrium may be a proximate cause for endometriosis

OBJECTIVE

To test the hypothesis that endometriosis may originate from genomic alterations in the endometrium by genomic analysis of endometrial tissues in patients with endometriosis and compare them with those from normal controls.

METHODS

Endometrial tissue samples were taken from five women with endometriosis. For controls, we used endometrial tissue samples from four women who underwent elective abortions and one sample from placenta. Using array-based comparative genomic hybridization (CGH), we determined the normal range of variation in CGH signals using normal controls. CGH results were further confirmed by real-time quantitative PCR and loss of heterozygosity analysis.

RESULTS

We identified several regions of genomic alterations in all five patients. Some of these regions were the same regions identified previously in endometriotic lesions. For select markers, the genomic alterations were confirmed by real-time PCR and LOH analyses.

CONCLUSIONS

There is evidence that the endometrium in women with endometriosis has genomic alterations. This is consistent with numerous reports that the endometrium of women with endometriosis differ from those of women without. Our finding suggests that genomic alterations in the endometrium may be a proximate cause for endometriosis.

Record review of baboons with histologically confirmed endometriosis in a large established colony

Spontaneous endometriosis was diagnosed in 43 baboons over a 14-year period. Thirty-seven have died; five remain alive; one was sold and lost to follow-up. The average age at diagnosis was 17.2 years; 29 (67%) were between 12 and 21 years of age. Fifteen (35%) were diagnosed by biopsy and received surgical excision of the endometriotic tissue; four of these were identified during caesarian section, confirming one prior report of endometriosis in pregnant animals. Twenty-eight (65%) were diagnosed at or shortly preceding necropsy. When diagnosed by a palpable abdominal mass, there was a significantly greater likelihood the animal died or was killed as a result of complications of endometriosis. When diagnosis was at necropsy, there was a significantly greater likelihood that the animal died from causes unrelated to endometriosis. Early identification with surgical removal appears to provide a benefit for both survival and delivering offspring after diagnosis. In twenty-one baboons (49%), endometriosis affected multiple sites within the peritoneal cavity. In the remaining baboons, lesions were more localized. Ovarian involvement was seen in sixteen (37%) of these baboons. This paper is the first to describe significant ovarian involvement in baboons, previously considered a limitation of the usefulness of this species as an animal model. We also describe the first reported endometriosis seeding of an abdominal surgery scar in a baboon. Many of these baboons were middle aged, had few or no offspring, or had evidence of a long duration of uninterrupted menstrual cycles, consistent with risk factors for women. Endometriosis was an incidental finding in 17 (40%) of these baboons, consistent with previous reports of minimal endometriosis as a common asymptomatic finding in baboons and in women. Overall, endometriosis in baboons presents a spontaneously occurring animal model that shares important features with the disease in women and the rhesus macaque.

Endometriosis is associated with an altered profile of intestinal microflora in female rhesus monkeys

BACKGROUND

The intestinal microflora provide a strong defence against intestinal pathogens, and may be altered in inflammatory conditions that impact the gut, such as endometriosis. Therefore, intestinal bacteria shed from rhesus monkeys with endometriosis were compared with age-matched healthy controls. A second study assessed the prevalence of intestinal inflammation in female monkeys to determine whether endometriosis is associated with an increased likelihood of intestinal inflammation.

METHODS

Differential and selective agars were used to enumerate total and Gram-negative aerobic and facultatively anaerobic bacteria, as well as Lactobacilli, from female monkeys with or without endometriosis. In addition, the prevalence of intestinal inflammation in monkeys with or without endometriosis was determined in a retrospective analysis of necropsy reports.

RESULTS

Monkeys with endometriosis had a significantly different profile of shed microflora. Endometriosis was associated with lower Lactobacilli concentrations and higher Gram-negative bacteria concentrations. Moreover, there was a higher prevalence of intestinal inflammation in monkeys with endometriosis in comparison to healthy controls.

CONCLUSIONS

Endometriosis is associated with an altered profile of intestinal microflora in rhesus monkeys. Although the exact mechanisms linking endometriosis and the microflora are unknown, it is possible that the microflora were affected by endometriosis-associated intestinal inflammation.

Toward developing a genome-wide microsatellite marker set for linkage analysis in the rhesus macaque (Macaca mulatta): identification of 76 polymorphic markers

Linkage analysis can be problematic in humans because of the lack of large, multigenerational pedigrees and the difficulties in obtaining phenotypic data on all family members. In contrast, large, captive colonies of rhesus macaque are a potentially valuable resource for linkage studies because detailed phenotypic and genealogical data are kept, inbreeding is avoided, and DNA samples can usually be obtained. Microsatellite marker sets for genome-wide screening are available in a number of species, but not for the rhesus macaque. We tested primers to 400 human microsatellite markers from a genome-wide mapping set using DNA from nine unrelated female rhesus macaques. We found that 76 (19%) of the primers amplified a polymorphic product using the standard protocols for human DNA. The average heterozygosity of the markers in humans was 0.80, compared to 0.65 in the rhesus macaques. This study provides preliminary data, which could be used toward the development of a linkage mapping set in this species. There would be a need, however, to confirm the Mendelian inheritance of the markers.

Endometriosis in rhesus monkeys

Endometriosis was present in five out of six Rhesus monkeys who had to be sacrificed because of disease in a colony of 90. The monkeys lost appetite and became constipated. The abdomen was distended and often a pelvic mass could be palpated. At autopsy, 300-500 ml of blood-stained fluid was found in the abdomen together with intestinal or pelvic endometriosis. The ethiology of endometriosis in Rhesus monkeys is unknown. The most probable explanation is intraabdominal implantation of endometrial tissue through retrograde menstruation. The lesion is rare in animals in free ranging colonies. It is not known whether this is due to a higher frequency of pregnancies in animals with free access to matings or to its consequences, i.e. more infrequent menstruations.