Chapter 067. Applications of Stem Cell Biology in Clinical Medicine (Part 4)

Other Organ Systems and the Future The use of stem cells in regenerative medicine has been studied for many other organ systems and cell types, including skin, eye, cartilage, bone, kidney, lung, endometrium, vascular endothelium, smooth muscle, striated muscle, and others. In fact, the potential for stem cell regeneration of damaged organs and tissues is virtually limitless. However, numerous obstacles must be overcome before stem cell therapies can become a widespread clinical reality. Only HSCs have been adequately characterized by surface markers to allow unambiguous identification, a prerequisite for reliable clinical applications. The pathways for differentiating stem cells into...
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Chapter 067. Applications of Stem Cell Biology in Clinical Medicine (Part 4) Chapter 067. Applications of Stem Cell Biology in Clinical Medicine (Part 4) Other Organ Systems and the Future The use of stem cells in regenerative medicine has been studied for manyother organ systems and cell types, including skin, eye, cartilage, bone, kidney,lung, endometrium, vascular endothelium, smooth muscle, striated muscle, andothers. In fact, the potential for stem cell regeneration of damaged organs andtissues is virtually limitless. However, numerous obstacles must be overcomebefore stem cell therapies can become a widespread clinical reality. Only HSCshave been adequately characterized by surface markers to allow unambiguousidentification, a prerequisite for reliable clinical applications. The pathways fordifferentiating stem cells into specific cellular phenotypes are still unknown, themigration of transplanted cells is uncontrolled, and the response of the cells to theenvironment of diseased organs is unpredictable. Future strategies may employ thecoadministration of scaffolding, artificial extracellular matrix, and/or growthfactors to orchestrate differentiation of stem cells and their organization intoappropriate constituents of the organ. Imaging techniques are needed to visualizestem cells in vivo after transplantation into humans. Fortunately, stem cells can beengineered before transplantation to contain contrast agents that may make thisfeasible. The potential for tumor formation and the problems associated withimmune rejection are significant impediments. Many strategies for cellreplacement already include vasoactive endothelial growth factor (VEGF)coadministration to foster vascularization, which is required for survival andfunction of the transplant. Some stem cells have been engineered to have aninducible suicide gene so that the cells can be eradicated in the event of tumorformation or some other complication. The potential for stem cell therapies torevolutionize medical care is extraordinary, and disorders such as myocardialinfarction, diabetes, Parkinsons disease and many others are attractive targets.However, such stem cell–based therapies are at a very early stage of development,and perfection of techniques for clinical transplantation of predictable, well-characterized cells will be a difficult and lengthy undertaking. Ethical Issues Stem cell therapies raise contentious ethical issues that must be addressedin parallel with the scientific and medical opportunities. Our society has greatdiversity in religious beliefs, concepts of individual rights, tolerance foruncertainty and risk, and boundaries for how scientific interventions should beused to alter the outcome of disease. In the United States, the federal governmenthas authorized research using human ES lines in existence before August 2001 buthas restricted the use of federal funds for developing new human ES lines.However, these existing lines develop abnormalities with time in culture and arecontaminated with mouse proteins. These findings have sparked renewed debateabout the need to develop new human ES cell lines. In considering ethical issues associated with the use of stem cells, it ishelpful to draw from experience with other scientific advances, such as organtransplantation, recombinant DNA technology, implantation of mechanicaldevices, neuroscience and cognitive research, in vitro fertilization, and prenatalgenetic testing. From these and other precedents, we learn the importance ofunderstanding and testing fundamental biology in the laboratory setting and inanimal models before applying new techniques in carefully controlled clinicaltrials. When these trials occur, they must include full informed consent and havecareful oversight by external review groups. Ultimately, medical interventions will be scientifically feasible but ethicallyor socially unacceptable to some members of a society. Stem cell research raisesquestions about the definition of human life, and it has raised deep fears about ourability to balance issues of justice and safety with the needs of critically illpatients. Health care providers and experts with backgrounds in ethics, law, andsociology must help guard against the premature or inappropriate application stemcell therapies, and the inappropriate use of vulnerable population groups. On theother hand, these therapies offer important new strategies for the treatment ofotherwise irreversible disorders. An open dialogue between the scientificcommunity, physicians, patients, and their advocates, lawmakers, and the laypopulation is important to raise and address ethical issues and to balance thebenefits and risks associated with stem cell transfer. ...