A non-human animal model for endometriosis is provided as well as methods of making and using the animal.

BACKGROUND OF THE INVENTION

Endometriosis is a chronic disease that affects nearly 5 million American women, or nearly 1 in 7 women of reproductive age (Klotz et al., 1995). Although endometriosis causes significant disability and distress in millions of women, it is often undiagnosed and, in general, is poorly understood (Corwin, 1997). Endometriosis is a benign disease that presents pleomorphic lesions of endometrial tissue containing glands or stroma or both growing at sites outside the uterine corpus. The ectopic sites include the ovaries, broad ligaments, rectovaginal septum, umbilicus, and laparotomy scars. The endometrial glands respond to hormonal stimuli, resulting in cyclic menstrual bleeding in the ectopic foci. Blood accumulates in cystic structures that are surrounded by inflammatory adhesions. Infertility, dysmenorrhea and chronic pelvic pain are the main symptoms, and are significant gynecological problems.

The exact etiology of this disease is controversial, but endometriosis occurs infrequently outside of the reproductive years, and appears to develop principally from the ectopic implantation of endometrial tissue entering the peritoneal space at the time of menstruation (Ishimaru et al., 1991; Sampson et al., 1927). Additionally, numerous experimental observations demonstrate that introduction of endometrial fragments into the peritoneal space of women (Ridley, 1968) and nonhuman primates (TeLinde et al., 1950) can result in the development of endometriosis.

Although retrograde menstruation has been reported in most women (Halme et al., 1984), endometriosis does not develop in all of them. Accumulating evidence suggests that altered cellular immunity may be involved in the pathogenesis of endometriosis both in women and in rhesus monkeys (Steele et al., 1984; Oosterlynck et al., 1991). Decreased in vitro lymphocyte proliferation in response to autologous endometrial cells has been reported in both rhesus monkeys and women with endometriosis (Steele et al., 1984). Decreased autologous antiendometrial lymphocytotoxicity and decreased natural killer (NK) cell activity has been reported in women with endometriosis when compared with women with a normal pelvis by some but not by other investigators (D'Hooghe et al., 1996).

There is evidence that immune surveillance is altered in women with endometriosis (Steele et al., 1984; Oosterlynck et al., 1991), which may facilitate the implantation of retrogradely shed menstrual endometrial cells. Whether immunosuppression facilitates the development of endometriosis is unknown. Immunosuppression has known profound effects on cellular and humoral immunity: global defects of T- and B-cell populations; decreased NK cell activity; 50% suppression of phytohemagglutinin-, concanavalin A-, and pokeweed mitogen-stimulated blastogenesis; decreased T-helper-T-suppressor ratio; impaired T-suppressor cell function; and reduced in vitro lymphokine-activated NK cell activity (D'Hooghe et al., 1996).

NK cell activity is decreased in women with endometriosis (Oosterlynck et al., 1991; Vigano et al., 1991). The reduced activity is not the result of a quantitative defect in these cells, nor does it appear to cause a significant reduction in systemic immunity (Oosterlynck et al., 1991; Vigano et al., 1991). The reduced NK cell activity may then result in a deficiency in the ability to reject autologous endometrial tissue, causing these women to have an increased risk for the development of endometriosis (Oosterlynck et al., 1991; Vigano et al., 1991).

Because of the expense and difficulties of human and primate research, models for the study of endometriosis have been developed in several other mammals. Many attempts have been made to elucidate the pathogenesis of endometriosis and to evaluate the therapeutic ability of new drugs against endometriosis by autotransplantation of endometrium to the peritoneal cavity of the subcutaneous layer in various laboratory animals, including rats (Klotz et al., 1995; Corwin, 1997; Ishimura et al., 1991), rabbits (Sampson, 1927; Ridley, 1968), monkeys (TeLinde et al., 1950; Halme et al., 1984) and mice (Aoki et al., 1994). The surgical transplantation of endometrial tissue wedges into the peritoneal sidewall and/or onto the ovary is the typical animal model used for studying endometriosis (Aoki et al., 1994; Vernon et al., 185; Zamah et al., 1984). This type of research model is helpful in investigating the effects of medications on ectopic endometrial tissue growth as well as in the in vivo pathophysiologic actions of these implants (Ramey et al., 1996).

The various existing animal models of endometriosis include the mouse (Yang and Foster, 1997), and the rat (Vernon and Wilson, 1985; Yang et al, 1996), where endometriosis is surgically induced by excising the uterine horn and uterine explants in ovariectomized rats and placed in anterior and posterior bifurcation of the uterine horns, and estrogen capsules implanted under the skin or exogenous hormone treatments. However, a major hurdle for understanding the etiology, pathophysiology and spontaneous evolution of the disease is the lack of an appropriate animal model closely mimicking human endometriosis.

Thus, what is needed is a non-human animal model for endometriosis.

SUMMARY OF THE INVENTION

The invention provides a mammalian chimera comprising a non-human mammal and human endometrial cells and/or tissue, as well as a method of preparing the chimeric mammal. The method comprises contacting, e.g., transplanting endometrial tissue and/or cells from a human to a non-human mammal so as to result in a non-human mammalian chimera. Preferably, the non-human mammal employed to prepare the chimera is immunodeficient, e.g., a severe combined immunodeficient (SCID) non-human mammal such as a SCID rat or mouse, or an athymic non-human mammal. The transplanted tissue is preferably from a human at risk of, or having, endometriosis. Also preferably, the endometrial tissue has (prior to contacting or transplanting) or yields (after contact or transplant) at least one endometritic lesion, at least one endometritic adhesion, proliferating human endometrial tissue, or any combination thereof. It is preferred that the endometrial tissues proliferates, forms at least one endometritic lesion, or at least one endometritic adhesion, in the absence of exogenously added hormone(s).

As described hereinbelow, immunodeficient SCID-beige, T, B and NK cell deficient mice were contacted, e.g., transplanted, with human endometrial tissue and/or cells so as to result in a non-human mammalian chimera. Ectopic or eutopic endometrial tissue may be obtained from patients with endometriotic lesions. The tissue is sectioned into uniform pieces and transplanted, for example, by stitching the tissue outside the left uterus horn, into female immunodeficient mice. Animals were then sacrificed after 12 24 weeks. The transplanted endometrial tissue was located in the abdominal cavity, with spread out adhesions. There was a correlation of the size of the endometrial cysts recovered from the chimeric animals with larger cysts observed in chimeric animals sacrificed at the end of 24 weeks compared to those sacrificed after 12 weeks. Endometrial graft from patient A induced endometriotic lesions in one out of two mice, however, both mice exhibited massive adhesions in the abdominal cavity. Tissue from patient B was successfully transplanted with endometriotic lesions in two out of two mice. Although tissue from patient C induced endometriotic lesion/proliferating endometrium in two of four mice, adhesions were present in all the animals. Tissue from patient D induced endometriosis in 3 of 4 mice. All the engrafted endometriotic cysts were stained with anti-human keratinin.

Thus, the chimeras of the invention were successfully transplanted with human endometriosis tissue, which formed proliferating endometriotic lesions in the chimeras that resemble human endometriosis. Therefore, the non-human mammalian chimeras of the invention may be useful to determine the role/effect of various hormones/therapeutic agents in treating human endometriosis, including the role of oral contraceptives on the natural history of endometriosis progression. In addition, co-transplantation of various human immune cells, such as T, B and macrophages from patients, may further define the role of immune cells in the pathophysiology of endometriosis.

Further provided is a method of using the mammalian chimera of the invention. The method comprises contacting the chimera with an agent. Then it is determined whether the agent inhibits, reduces or prevents the proliferation of human endometrial tissue, endometritic lesion formation, endometritic adhesion formation, or an combination thereof.
 

Claim 1 of 7 Claims

1. A chimeric mouse, which is a model for endometriosis, wherein said chimeric mouse is an immunocompromised mouse comprising ectopic human endometrial cells or tissue, wherein the ectopic cells or tissue are affixed to the outside of the uterine horn of the immunocompromised mouse, and wherein the ectopic cells or tissue proliferate, form at least one endometrial lesion, form at least one endometrial adhesion, or any combination thereof, and wherein the chimeric mouse is not subjected to exogenous hormone treatment.

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