Mesenchymal Stromal Cells and Tissue-Specific Progenitor Cells: Their Role in Tissue Homeostasis

Figure 1

Tissue distribution and the phenotype of tissue-resident stem cells characterized by immunocytochemistry for CD45, CD34, CD73, CD90, c-kit, and Pax7. Tissue samples were collected from skin, liver, heart, and skeletal muscle. Immunostaining for CD45 and CD34 (arrows) illustrated the presence of cells of hematopoietic origin in the tissues. Note CD34 positivity on the vessel endothelial cells. Common feature of tissue localized stem cells was expression of CD73, CD90, and c-kit. Skeletal muscle progenitor cells exclusively express transcriptional factor Pax7. CD73, CD90, and c-kit were expressed on single stem cells of examined tissues and were localized in specific tissue compartments: in the basal layer of epidermis, the epithelium of adnexal structure of the skin, the periportal area of the liver, between the basal lamina and sarcolemma of myofibers of the muscle, and were connected to myocytes and fibroblasts in the cardiac niches.