Gabriel Mbalaviele

Mesenchymal Stem Cells

Many adult mammalian tissues maintain a healthy state by continuous renewal involving cell turnover. In response to trauma, disease or overuse, the body either repairs or regenerates the tissue.These two possibilities are distinguished in that regeneration results in new tissue that is indistinguishable from the original tissue in its structural organization, cellular content and function, whereas repair results in a high content of fibroblastic tissue, scar formation, limited structural organization and impaired function. Certain tissues, including skin, intestine, epithelium, and skeletal muscle have regenerative ability owing to resident progenitor cells. Other regenerating tissues, such as liver, have differentiated cells that retain the ability to de-differentiate and re-enter a proliferating growth phase before differentiating once again. Many types of blood cells originate from hematopoietic stem cells (HSCs) present in the sinusoids of bone marrow. In addition to progenitor cells resident in tissues, multipotent stem cells capable of connective tissue regeneration reside in bone marrow. The in vitro and in vivo study of these bone marrow-derived mesenchymal stem cells (MSCs) is important in developing a comprehensive understanding of the dynamic processes that occur in regenerating tissues and the roles that MSCs play. The characterization of proliferative fibroblastic marrow cells with the potential to differentiate has been explored from multiple species including mouse [1-7], guinea pig [8,9], rat [10-14], rabbit [15-20], dog [21-23], horse [24, 25] and man [26-35 and references therein], and several reviews have been published [49-55]. While many of these reports suggested the stem cell nature of the cells under study, the characterization was often incomplete.