title: Stem cell-like differentiation potentials of endometrial side population cells as revealed by a newly developed in vivo endometrial stem cell assay.
abstract: BACKGROUND
  Endometrial stem/progenitor cells contribute to the cyclical regeneration of human endometrium throughout a woman's reproductive life. Although the candidate cell populations have been extensively studied, no consensus exists regarding which endometrial population represents the stem/progenitor cell fraction in terms of in vivo stem cell activity. We have previously reported that human endometrial side population cells (ESP), but not endometrial main population cells (EMP), exhibit stem cell-like properties, including in vivo reconstitution of endometrium-like tissues when xenotransplanted into immunodeficient mice. The reconstitution efficiency, however, was low presumably because ESP cells alone could not provide a sufficient microenvironment (niche) to support their stem cell activity. The objective of this study was to establish a novel in vivo endometrial stem cell assay employing cell tracking and tissue reconstitution systems and to examine the stem cell properties of ESP through use of this assay.
  
  
  RESULTS
  ESP and EMP cells isolated from whole endometrial cells were infected with lentivirus to express tandem Tomato (TdTom), a red fluorescent protein. They were mixed with unlabeled whole endometrial cells and then transplanted under the kidney capsule of ovariectomized immunodeficient mice. These mice were treated with estradiol and progesterone for eight weeks and nephrectomized. All of the grafts reconstituted endometrium-like tissues under the kidney capsules. Immunofluorescence revealed that TdTom-positive cells were significantly more abundant in the glandular, stromal, and endothelial cells of the reconstituted endometrium in mice transplanted with TdTom-labeled ESP cells than those with TdTom-labeled EMP cells.
  
  
  CONCLUSIONS
  We have established a novel in vivo endometrial stem cell assay in which multi-potential differentiation can be identified through cell tracking during in vivo endometrial tissue reconstitution. Using this assay, we demonstrated that ESP cells differentiated into multiple endometrial lineages in the niche provided by whole endometrial cells, indicating that ESP cells are genuine endometrial stem/progenitor cells.
authors.affiliation: Department of Obstetrics and Gynecology, School of Medicine, Keio University, Tokyo, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Miyazaki
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Maruyama
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Masuda
authors.forename: Akiko
authors.initials: A
authors.lastname: Yamasaki
authors.forename: Sayaka
authors.initials: S
authors.lastname: Uchida
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Oda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uchida
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Yoshimura
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000328:Adult; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation; D019070:Cell Lineage; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D002469:Cell Separation; D003114:Colony-Forming Units Assay / Q000379:methods*; D004717:Endometrium / Q000166:cytology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000378:metabolism; D058985:Side-Population Cells / Q000166:cytology* / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D015415:Biomarkers; D009363:Neoplasm Proteins