Thursday, September 5, 2013

Stem cells, tissues and regenerative medicine

Excerpted from "Stem cells mimic human brain," Nature. August 28, 2013 -- With the right mix of nutrients and a little bit of coaxing, human stem cells derived from skin can assemble spontaneously into brain-like chunks of tissue. “It’s a seminal study to making a brain in a dish,” says Clive Svendsen, a neurobiologist at the University of California, Los Angeles, who was not involved in the study. “That’s phenomenal.” A fully formed artificial brain might still be years away, he notes, but the pea-sized neural clumps developed in this work could prove useful for researching human neurological diseases.

In the latest advance, scientists developed bigger and more complex neural-tissue clumps by first growing the stem cells on a synthetic gel that resembled natural connective tissues found in the brain and elsewhere in the body. Then they plopped the nascent clumps into a spinning bath to infuse the tissue with nutrients and oxygen.

“The big surprise was that it worked,” says study co-author Juergen Knoblich, a developmental biologist at the Institute of Molecular Biotechnology in Vienna. The blobs grew to resemble the brains of fetuses in the ninth week of development. Under a microscope, researchers saw discrete brain regions that seemed to interact with one another. But the overall arrangement of the different proto-brain areas varied randomly across tissue samples — amounting to no recognizable physiological structure.

“The entire structure is not like one brain,” says Knoblich, adding that normal brain maturation in an intact embryo is probably guided by growth signals from other parts of the body. The tissue balls also lacked blood vessels, which could be one reason that their size was limited to three to four millimeters in diameter, even after growing for 10 months or more.


Dr. David PrenticeCMDA Member and Senior Fellow for Family Research Council David Prentice, PhD: “There have been numerous stories lately about using induced pluripotent stem (iPS) cells to form various tissues, including vascular endothelial cells for blood vessels, myocardial tissue for heart muscle regeneration and even brain tissue for study of normal and abnormal brain development.

“The iPS cells, because they are created from the patient’s own normal cells, could potentially provide tissues for personalized drug development or for transplant. There are still significant practical problems to overcome with iPS cells, including their penchant for growth, which may make them more suitable for laboratory study than for the clinic.

“But the ethics of the research is also significant. The iPS cell creation technique (for which Dr. Yamanaka won the Nobel Prize) does not rely on creation or destruction of human life—it does not use embryos, eggs or cloning techniques. Thus, it provides an ethical source of cells for study (as long as the molecular tools used for creation of the iPS cells are ethical, of course; i.e., not using aborted fetal tissue for DNA production, etc.). As more and more cellular and molecular techniques approach the clinic, this ethical consideration is very important if we are to maintain our stance for life. “Do no harm” applies not only to the patient treated, but to the origin of the treatment as well. We should reject any ethically-tainted treatments just as we would reject any bacterially-tainted or chemically-tainted drug or instrument.”

CMDA Ethics Statement on Stem Cell Research and UseScientific Demagoguery in the Stem Cell Wars by David Stevens, MD, MA (Ethics)

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