Investigators from Stanford University School of Medicine have shown that induced Pluripotent Stem cells (iPSCs), which are made from adult cells through genetic engineering techniques, are a possible alternative to human embryonic stem cells when it comes to modeling those defects caused by a particular genetic condition. The example used in this study was Marfan syndrome, and in this study, iPSCs modeled the disease as well as embryonic stem cells (ESCs). Thus, iPSCs could be used to examine the molecular aspects of Marfan on a personalized basis. Embryonic stem cells, on the other hand, can’t do this because their genetic contents are those of the donated embryo are not the same as the patient’s.
Marfan syndrome is an inherited connective-tissue disorder that occurs in one in 10,000 to one in 20,000 individuals. It results from a large number of defects in one gene called “fibrillarin.” People with Marfan syndrome tend to be very tall and thin, and also tend to suffer from osteopenia, or poor bone mineralization. Medical experts have speculated that Abraham Lincoln, for example, suffered from this disorder. Marfan can also profoundly affect the eyes and cardiovascular system.
This proof-of-principle study, with regards to the utility of iPSCs also has more universal significance; it advances the credibility of using iPSCs to model a broad range of human diseases. iPSCs, unlike ESCs, are easily obtained from virtually anyone and possess a genetic background identical to the patient from which they were derived. Moreover, they carry none of the ethical controversy associated with the necessity of destroying embryos.
“Our in vitro findings strongly point to the underlying mechanisms that may explain the clinical manifestations of Marfan syndrome,” said Michael Longaker, MD, professor of surgery and senior author of the study, which will be published online Dec. 12 in Proceedings of the National Academy of Sciences. Longaker is the Dean P. and Louise Mitchell Professor in the School of Medicine and co-director of the school’s Institute for Stem Cell Biology and Regenerative Medicine. The study’s first author is Natalina Quarto, PhD, a senior research scientist in Longaker’s laboratory.
In this study, both iPSCs and ESCs, and embryonic stem cells that carried a mutation that causes Marfan syndrome showed impaired ability to form bone, and all too readily formed cartilage. These aberrations mirror the most prominent clinical manifestation of the disease.
iPSCs were discovered in 2006, and are derived from fully differentiated tissues such as the skin. However, they harbor the same capacity as embryonic stem cells; namely to differentiate into all the tissues of the body, and replicate for indefinite periods in a cell culture dish. Because iPSCs offer an ethically uncomplicated alternative to ESCs, IPSCs have fueled the hope that they can replace ESCs in scientists’ efforts to analyze, in a dish, those cellular defects ultimately responsible for diseases ranging from diabetes to Parkinson’s and even such complex conditions as cardiovascular disease and autism.
One hope for iPSCs is to be able to differentiate them in a dish into tissues of interest and then study these cells and their characteristics. This would help scientists better understand diseases in a patient-specific way, which would be impossible to do with ESCs unless ESCs were made from donated human eggs that were modified by cloning procedures. Cloning human embryos to the blastocyst stage has yet to occur, which makes this option technically impossible at the present time.
While scientists want to us iPSCs to develop therapeutic applications for regenerative medicine. This strategy, however, is technically more difficult, since scientists will have to develop the capacity first to repair genetic defects within cells before they can be used for regenerative medicine. iPSCs in theory might be a better bet because they are derived from patients’ own cells and, therefore, are less likely to provoke graft rejection than similar tissues produced using a donor embryo’s ESCs.
Unfortunately, several studies have reported subtle differences between iPSCs and ESCs, and these differences imply that the two cell types may not be equivalent. Stem cell experts have wondered whether these differences may render iPSCs inadequate substitutes for ESCs in modeling disease states, but this Stanford study suggests otherwise.