Evidence for the presence of stem/progenitor cells in porcine endometrium.

A population of adult stem cells responsible for cyclic reconstructing and remodeling has been proposed to reside in the highly regenerative mammalian endometrium. Recently, stem/progenitor cells have been identified in the human and mouse endometrium, but less is known about these cells in livestock animals. Using Hoechst 33342 fluorescent dye staining and flow cytometry, we identified an emerging cell side population that may be responsible for the regeneration process of the porcine endometrium. The percentage of side-population cells on Day 19 of the estrous cycle was significantly higher than that on Days 2-4. Moreover, single cells were able to seed clones that could differentiate into three independent mesenchymal-cell lineages. We also demonstrated the expression of specific markers of self-renewal cells on these side-population cells and the presence of a population of cells among the stromal cells that possess markers for mesenchymal stem cells. These results indicate that the porcine endometrium contains a population of cells with the capacity for self-renewal and a high rate of proliferation, which depend on the phase of the estrous cycle. These cells could potentially be involved in the cyclic reconstruction of the porcine endometrium.