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Arnold I. Caplan, PhD

Professor, Biology 216.368.3562 (o) 216.368.4077 (f)

Member, Hematopoietic and Immune Cancer Biology Program


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You are ALIVE because you continuously renew (rejuvenate) various tissues/organs. Within the body, cells of the skin, gut, and blood, among others come to maturation, function for a time and then expire to be replaced by a continuous stream of cells which renew the tissue. The fabric of bone is broken down by specialized cells, osteoclasts, to form large pits into which bone-forming cells, osteoblasts, deposit new bone until the pits are filled; these osteoblasts then expire and newly differentiated osteoblasts take their place. In every tissue in which this rejuvenation process occurs, a source exists which gives rise to these differentiated cells. The source is called a STEM CELL. Such a stem cell divides to produce like stem cells, some of which enter into a pathway of development and differentiation resulting in an end-phenotype which produces highly specialized molecules and/or functions and then, after a time, expires.

The emphasis of our studies is to develop and refine the technology necessary to isolate one of these rare stem cells, the mesenchymal stem cell (MSC). The MSC gives rise to bone-forming cells, cartilage-forming cells and cells of tendon, ligament fat, and dermis, as well as various connective tissues including the stroma of marrow. Following isolation and by mitotically expanding their numbers in culture, we can drive these cells down specific and different developmental pathways with emphasis on cartilage and bone. The experimental approaches use the classical information of both morphogenesis and organogenesis coupled with the new information of the control of developmental lineage progression as controlled by potent growth factors. The knowledge gained from animal models will be directly applied to the study of human MSC, as our preliminary studies have already proven to be successful. These studies integrate both basic scientists and clinicians to more effectively translate these basic science findings into new, innovative human health care protocols of using tissue engineering to repair skeletal tissues as in this accompanying figure.