Mesenchymal stem cells (MSCs) are multipotent cells that exist in mesenchymal tissues such as bone marrow and are able to differentiate into osteocytes, chondrocytes, and adipocytes. MSCs are generally collected as adherent cells on a plastic dish, and are positive for markers such as CD44, CD73, CD90, CD105 and CD166, and negative for CD11b, CD14, CD19, CD31, CD34, CD45, CD79a and HLA-DR. MSCs have been established from many kinds of mammals, but MSCs from amphibians have not yet been reported. We cultured adherent cells from the bone marrow of Xenopus laevis by modifying the protocol for culturing mammalian MSCs. The morphology of these cells was similar to that of mammalian MSCs. The amphibian MSCs were positive for cd44, cd73, cd90 and cd166, and negative for cd11b, cd14, cd19, cd31, cd34, cd45, cd79a and hla-dra. Moreover, they could be induced to differentiate into osteocyte-, chondrocyte-, and adipocyte-lineage cells by cytokine induction systems that were similar to those used for mammalian MSC differentiation. Thus, they are considered to be similar to mammalian MSCs. Unlike mammals, amphibians have high regenerative capacity. The findings from the present study will allow for future research to reveal how Xenopus MSCs are involved in the amphibian regenerative capacity and to elucidate the differences in the regenerative capacity between mammals and amphibians.
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