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The regenerative powers of the human body may lead to new treatments for hard-to-treat diseases, says Paul J. Simmons, Ph.D., director of the Center for Stem Cell Research at the Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases (IMM), which is a part of The University of Texas Health Science Center at Houston.
Paul J. Simmons, Ph.D.
Simmons’ lecture earlier this year was the third of four by IMM senior faculty presented by the Houston Seminar lecture series in the Fayez S. Sarofim Research Building. It was titled “Stem Cells: From Concept to Clinic.”
“It is estimated that the human body loses approximately 50 million cells every second of our life. At that rate we would cease to exist in about a month were it not for cell replacement. Fortunately the human body is a prolific cell producing machine,” said Simmons, who is president of the International Society for Stem Cell Research (http://www.isscr.org). For example, skin is replaced every 27 days and the lining of the intestines every two days, which equates to 13,000 times during adult life.
Stems cells are at the apex of this amazing capacity for cell regeneration, explained Simmons. Not only are stem cells ultimately responsible for all cell replacement in most adult tissues and organs, they may also be used to create substitute tissues and organs. There are two major categories of stem cells. Adult stem cells are found in most, if not all, body tissues and are limited in their developmental potential to regenerating cells of the organ in which they reside. On the other hand, human embryonic stem cells can develop into any of the body’s 250 cell types and are consequently described as pluripotent stem cells.
Stem cells from adult tissues are already being used in some clinical situations. Present in bone marrow, hematopoietic stem cells (HSC) are involved in the treatment of leukemia, lymphoma and other inherited blood disorders. Doctors started transferring HSCs in bone marrow transplants 40 years ago.
More clinical applications could be coming, Simmons said.
Simmons said IMM biologists are studying stem cells and translating their unique biological properties into novel cellular therapies for graft engineering and tissue regeneration. Some of their work is based on a population of stem cells termed mesenchymal stem cells. Also found in bone marrow, MSC have the potential to generate fat, cartilage, bone and muscle.
In Australia, mesenchymal cells were used to treat a fractured forearm bone that was separated by 50 millimeters, he said. This is a non-union fracture which will not heal without surgical intervention. Using methodologies to isolate and culture MSC developed in Simmons’ lab, the patient’s own mesenchymal stem cells were immobilized on particles of hydroxyapatite, the same mineral as in bone tissue, and transplanted into the defect resulting in regeneration of bone tissue within the defect.
IMM biologists are also focusing some of their efforts on diseases of the lung and kidney, which Simmons described as areas of “unmet medical need.” “We have opportunities to cure diseases based on stem cell technology that currently have no effective treatments,” he said.
IMM scientists recently developed a new procedure for the differentiation of human embryonic stem cells, with which they have created the first transplantable source of lung epithelial cells. The process, created in the laboratory of Rick A. Wetsel, Ph.D., a professor of molecular medicine at the IMM, is described in the Proceedings of the National Academy of Sciences (PNAS). Research scientist Dachun Wang, M.D., is lead author of the article, “A pure population of lung alveolar epithelial type II cells derived from human embryonic stem cells.”
Simmons added, “Our goal is to translate the findings of our laboratory into the clinic. There is no more exciting field to be in …. I love it.”
—Rob Cahill
Date Posted: 05/07/2007
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