Quantitative trait locus analysis of ovarian cysts derived from rete ovarii in MRL/MpJ mice

Hydronephrosis with ureteritis developed in C57BL/6N mice carrying the congenic region derived from MRL/MpJ-type chromosome 11

Inbred MRL/MpJ mice show several unique phenotypes in tissue regeneration processes and the urogenital and immune systems. Clarifying the genetic and molecular bases of these phenotypes requires the analysis of their genetic susceptibility locus. Herein, hydronephrosis development was incidentally observed in MRL/MpJ-derived chromosome 11 (D11Mit21-212)-carrying C57BL/6N-based congenic mice, which developed bilateral or unilateral hydronephrosis in both males and females with 23.5% and 12.5% prevalence, respectively. Histopathologically, papillary malformations of the transitional epithelium in the pelvic-ureteric junction seemed to constrict the ureter luminal entrance. Characteristically, eosinophilic crystals were observed in the lumen of diseased ureters. These ureters were surrounded by infiltrating cells mainly composed of numerous CD3⁺T-cells and B220⁺B-cells. Furthermore, several Iba-1⁺macrophages, Gr-1⁺granulocytes, mast cells and chitinase 3-like 3/Ym1 (an important inflammatory lectin)-positive cells were detected. Eosinophils also accumulated to these lesions in diseased ureters. Some B6.MRL-(D11Mit21-D11Mit212) mice had duplicated ureters. We determined >100 single nucleotide variants between C57BL/6N- and MRL/MpJ-type chromosome 11 congenic regions, which were associated with nonsynonymous substitution, frameshift or stopgain of coding proteins. In conclusion, B6.MRL-(D11Mit21-D11Mit212) mice spontaneously developed hydronephrosis due to obstructive uropathy with inflammation. Thus, this mouse line would be useful for molecular pathological analysis of obstructive uropathy in experimental medicine.

Genomic analysis of the appearance of ovarian mast cells in neonatal MRL/MpJ mice

In MRL/MpJ mice, ovarian mast cells (OMCs) are more abundant than in other mouse strains, and tend to distribute beneath the ovarian surface epithelium at birth. This study investigated the factors regulating the appearance of neonatal OMCs in progeny of the cross between MRL/MpJ and C57BL/6N strains. F1 neonates had less than half the number of OMCs than MRL/MpJ. Interestingly, MRLB6F1 had more neonatal OMCs than B6MRLF1, although they were distributed over comparable areas. Furthermore, in MRL/MpJ fetuses for which parturition was delayed until embryonic day 21.5, the number of OMCs was significantly higher than in age-matched controls at postnatal day 2. These results suggest that the number of OMCs was influenced by the environmental factors during pregnancy. Quantitative trait locus analysis using N2 backcross progeny revealed two significant loci on chromosome 8: D8Mit343–D8Mit312 for the number of OMCs and D8Mit86–D8Mit89 for their distribution, designated as mast cell in the ovary of MRL/MpJ 1 (mcom1) and mcom2, respectively. Among MC migration-associated genes, ovarian expression of chemokine (C-C motif) ligand 17 at mcom1 locus was significantly higher in MRL/MpJ than in C57BL/6N, and positively correlated with the expression of OMC marker genes. These results indicate that the appearance of neonatal OMCs in MRL/MpJ is controlled by environmental factors and filial genetic factors, and that the abundance and distribution of OMCs are regulated by independent filial genetic elements.

microRNA biomarkers in cystic diseases

microRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by targeting the 3’-untranslated region of multiple target genes. Pathogenesis results from defects in several gene sets; therefore, disease progression could be prevented using miRNAs targeting multiple genes. Moreover, recent studies suggest that miRNAs reflect the stage of the specific disease, such as carcinogenesis. Cystic diseases, including polycystic kidney disease, polycystic liver disease, pancreatic cystic disease, and ovarian cystic disease, have common processes of cyst formation in the specific organ. Specifically, epithelial cells initiate abnormal cell proliferation and apoptosis as a result of alterations to key genes. Cysts are caused by fluid accumulation in the lumen. However, the molecular mechanisms underlying cyst formation and progression remain unclear. This review aims to introduce the key miRNAs related to cyst formation, and we suggest that miRNAs could be useful biomarkers and potential therapeutic targets in several cystic diseases. [BMB Reports 2013; 46(7):338-345]

Relationship between numerous mast cells and early follicular development in neonatal MRL/MpJ mouse ovaries

In the neonatal mouse ovary, clusters of oocytes called nests break into smaller cysts and subsequently form individual follicles. During this period, we found numerous mast cells in the ovary of MRL/MpJ mice and investigated their appearance and morphology with follicular development. The ovarian mast cells, which were already present at postnatal day 0, tended to localize adjacent to the surface epithelium. Among 11 different mouse strains, MRL/MpJ mice possessed the greatest number of ovarian mast cells. Ovarian mast cells were also found in DBA/1, BALB/c, NZW, and DBA/2 mice but rarely in C57BL/6, NZB, AKR, C3H/He, CBA, and ICR mice. The ovarian mast cells expressed connective tissue mast cell markers, although mast cells around the surface epithelium also expressed a mucosal mast cell marker in MRL/MpJ mice. Some ovarian mast cells migrated into the oocyte nests and directly contacted the compressed and degenerated oocytes. In MRL/MpJ mice, the number of oocytes in the nest was significantly lower than in the other strains, and the number of oocytes showed a positive correlation with the number of ovarian mast cells. The gene expression of a mast cell marker also correlated with the expression of an oocyte nest marker, suggesting a link between the appearance of ovarian ? 4mast cells and early follicular development. Furthermore, the expression of follicle developmental markers was significantly higher in MRL/MpJ mice than in C57BL/6 mice. These results indicate that the appearance of ovarian mast cells is a unique phenotype of neonatal MRL/MpJ mice, and that ovarian mast cells participate in early follicular development, especially nest breakdown.

Bilateral ovarian cysts originating from rete ovarii in an African green monkey (Cercopithecus aethiops)

Ovarian cyst is common incidental finding in humans and many animals and includes follicular cysts, cystic rete ovarii and mesonephric duct cysts. Ovarian cyst is often associated with reproductive disorders in humans and animals. We found accidentally bilateral cystic masses in ovaries in an African green monkey. Grossly, the left and right ovarian cystic masses were single unilocular cystic structures measuring 0.6 and 1.8 cm in diameter, respectively. Histologically, both cysts were thin-walled structures that arose from the center of the ovary and displaced ovarian tissue peripherally. The cysts were lined by a single layer of nonciliated low cuboidal epithelium. Immunohistochemically, epithelial cells in the cysts were positive for cytokeratin, and the stromal cells were positive for smooth muscle actin but negative for vimentin. These results suggest that these ovarian cysts in an African green monkey are cystic rete ovarii. To our knowledge, this is the first report of cystic rete ovarii in African green monkeys and may be of value in relation to research of the pathogenesis and treatment of ovarian cyst.

Ovarian cysts in MRL / MpJ mice are derived from the extraovarian rete: a developmental study

MRL/MpJ (MRL) mice, commonly used as a model for autoimmune disease, have a high frequency of ovarian cysts originating from the rete ovarii. In the present study, to clarify how the rete ovarii, which are remnants of mesonephric tubules during embryogenesis, progress to cystic formation with aging, the morphology of MRL rete ovarii was analyzed and compared with that of normal C57BL/6N (B6) mice. In B6 mice, the rete ovarii consisted of a series of tubules, including the extraovarian rete (ER), the connecting rete (CR), and the intraovarian rete (IR), based on their location. Whereas the ER of B6 mice was composed of highly convoluted tubules lined by both ciliated and non-ciliated epithelia, the tubules in the CR and IR had only non-ciliated cells. In MRL mice, dilations of the rete ovarii initiated from the IR rather than the ER or CR. Although the histological types of cells lining the lumen of the rete ovarii were the same as those in B6 mice, the ER in MRL mice showed a variety in morphology. In particular, the connections between the ER and ovary tended to disappear with increasing age and the development of ovarian cysts. Furthermore, the epithelium lining the large ovarian cysts in MRL mice had ciliated cells forming the cluster. On the basis of these findings, it is suggested that cystic changes of the rete ovarii in MRL mice are caused by the dilations of the IR with invasion of the ER and CR into the ovarian medulla. These data provide new pathological mechanisms for ovarian cyst formation.