Strategies for Stem Cell Replacement Stem cell transplantation is not a new concept and it is already part of established medical practice. Hematopoietic stem cells (HSCs) (Chap. 68) are responsible for the long-term repopulation of all blood elements in bone marrow transplant recipients. HSC transplantation is now the gold standard against which other stem cell transplantation therapies will be measured. Transplantation of differentiated cells is also a clinical reality, as donated organs (., liver, kidney) and tissues (., cornea, eye, skin) are often used to replace damaged tissues. However, the clinical need for transplantable tissues and organs far outweighs. | Chapter 067. Applications of Stem Cell Biology in Clinical Medicine Part 2 Strategies for Stem Cell Replacement Stem cell transplantation is not a new concept and it is already part of established medical practice. Hematopoietic stem cells HSCs Chap. 68 are responsible for the long-term repopulation of all blood elements in bone marrow transplant recipients. HSC transplantation is now the gold standard against which other stem cell transplantation therapies will be measured. Transplantation of differentiated cells is also a clinical reality as donated organs . liver kidney and tissues . cornea eye skin are often used to replace damaged tissues. However the clinical need for transplantable tissues and organs far outweighs the available supply and organ transplantation has limited potential for some tissues such as the brain. Stem cells offer the possibility of a renewable source of cell replacement for virtually all organs. At least three different therapeutic concepts for cell replacement have been considered Fig. 67-1 1 injection of stem cells directly into the damaged organ or into the circulation allowing them to home into the damaged tissue 2 in vitro differentiation of stem cells followed by transplantation into a damaged organ . pancreatic islet cells could be generated from stem cells prior to transplantation into patients with diabetes whereas cardiomyocytes could be generated to treat ischemic heart disease and 3 stimulation of endogenous stem cells to facilitate repair . administration of appropriate growth factors to amplify numbers of endogenous stem progenitor cells or direct them to differentiate into the desired cell types. In addition to these strategies for cell replacement the ex vivo or in situ generation of tissues provides an alternative means of tissue engineering Chap. 69 . Stem cells are also excellent vehicles for cellular gene therapy Chap. 65 . Figure 67-1 Strategies for transplantation of stem cells. 1. Undifferentiated or .
