all tissue regeneration stories

Stem cell research sheds light on organ regeneration

Wed, 11 Jul 2007 10:33:24 -0400

The rules governing mammalian organ repair and regeneration are so widely varied as to suggest at first glance that there are no rules: Blood has such an enormous regenerative capacity that you can literally give it away by the pint and be none the worse for wear; rip a hole in your skin and new skin will cover it; donate a portion of your liver and it will regenerate; but lose a kidney or suffer damage to your pancreas, and what's lost is lost.

Research reveals how stem cells build a heart

Wed, 11 Jul 2007 16:11:35 -0400

Master cells that give rise to the three main cell types in a human heart have been discovered by Harvard Stem Cell Institute scientists working independently at two Harvard-affiliated hospitals. Together they found that a single progenitor stem cell differentiates into cells that cause a heart to beat, that make up its internal surface, and form its blood vessels.

The master cells arise during an early stage of embryo growth. As-yet-undiscovered signals then stimulate them to form the main building blocks of the heart, the first identifiable organ in the development of human life. Once started, that life-sustaining muscular pump beats more than 2,500 million times during an average lifetime.

Muscle cells grown into working heart cells

Fri, 13 Jul 2007 09:32:26 -0400

Muscle cells have been used successfully to restore life-sustaining rhythms to ailing hearts, a first step toward developing natural pacemakers. Placed in a tiny raft of collagen implanted into the hearts of rats, these cells survived for the entire lifespan of the animals.

"Our experiments provide proof that engineered tissue can function as an electric conduit in the heart and, ultimately, may offer a substitute for artificial (electronic) devices," says Douglas Cowan. He is an assistant professor of anesthesiology at Harvard Medical School who led a team of biologists, cardiologists, and surgeons at Children's Hospital Boston to create a biological substitute for the tissue that keeps the heart beating regularly.

Transplanted cells regenerate muscles

70652986 — Mon, 26 Mar 2007 06:24:37 -0400

Biological engineering, which once excited the medical community, has been fraught with the difficulties of keeping transplanted cells alive and getting them to integrate with a host's body. Researchers at Harvard University's Department of Engineering and Applied Science may have solved these problems.

"We transplant the cells on a scaffold that keeps them alive, then directs them to leave in a controlled manner and migrate into the surrounding tissue," explains David Mooney, Gordon McKay Professor of Bioengineering. "This is the first time that has been done."

The strategy successfully heals lacerated muscles in mice, but the potential exists for applying it to a wide variety of situations in humans, including treatment of muscular dystrophy, heart disease, and some brain disorders, and to regenerate bone.

"We don't know yet whether the specific materials and approach we used [will] work in humans," Mooney says. "However, I think the basic concept is a very powerful one that will likely have application in humans in some form. We demonstrated the concept with muscle, and this could be useful to treat wounds and, perhaps some day, muscular dystrophy.

"In addition, it could be very useful in transplantation of cells to the heart to treat coronary artery diseases, to transplant cells that promote blood vessel formation, to transplant cells to the brain to treat various neurological conditions, and to transplant cells to promote bone generation."

Barrier found to nerve regeneration

70652986 — Mon, 26 Mar 2007 05:41:31 -0400

Scientists have long dreamed of prompting adult neurons of the central nervous system to regenerate. But these cells have the deck stacked against them in several ways. Molecules from the myelin sheath surrounding their axons actively discourage growth. After injury, nearby astrocytes form a dense scar to block them. Even the signals that once guided axons as they formed during development now seem to prevent regeneration. And most neurons also have lost the internal factors that enabled them to stretch their axons out in the first place - even if allowed to, they wouldn't grow.

Regeneration seems like a daunting task with all of these circumstances conspiring against it. Still, most researchers in the field believe it will be possible to remove the brakes on growth in the centrall nervous system if they can identify the restraints. An encouraging study in the Oct. 7, 2005 Science from the lab of Zhigang He, Harvard Medical School assistant professor of neurology at Children's Hospital Boston, uncovers a surprising new player on the side of inhibition - the well-known epidermal growth factor (EGF) receptor. The molecule appears to mediate the inhibitory signals of both myelin and proteoglycans from the glial scar - a convergence of pathways in a field that has become increasingly complex.

Researchers induce heart cells to proliferate

50443248 — Tue, 24 Jul 2007 14:23:18 -0400

In the best-documented effort to date, researchers from the Howard Hughes Medical Institute at Children's Hospital Boston and Harvard Medical School have successfully induced adult heart-muscle cells to divide and multiply.

Schepens scientists regenerate optic nerve for the first time

70652986 — Mon, 26 Mar 2007 06:20:43 -0400

In earlier research, Dr. Dong Feng Chen, lead author of the study, assistant scientist at Schepens Eye Research Institute and an assistant professor of ophthalmology at Harvard Medical school, and her team discovered several processes that they believed "locked up" the optic nerve's ability to regenerate. The first lock was the turning off of the gene BCL-2, which, when turned on, activates growth and regeneration. The second lock, they theorized, was a scar on the brain created shortly after birth by "glial" cells.

In the current research, Dr. Kin-Sang Cho, research associate in Chen's laboratory and the first author of the paper, tested two keys to unlock regeneration. The first key involved the development of a mouse model in which the BCL-2 gene is always turned on (or is over-expressing). The second key was the use of a mouse line carrying mutations of "glial specific genes" that lead to the reduced "glial scar" formation.

Unlocking the regeneration with the first key caused robust optic nerve regeneration, but only in the mice whose brains had not yet formed a "glial scar."

Cho then added the second key by combining BCL-2 over- expresser with the "glial gene" mutation to prevent the development of the "glial scar" in the older transgenic mice. He found that this combination caused rapid, robust regeneration of the optic nerve again, as with the younger mice.

The next step for Chen and her colleagues is to determine if the regenerated optic nerves were functional.

Tissue engineering produces an artificial gland

70652986 — Mon, 26 Mar 2007 05:04:38 -0400

Your thymus is a walnut-sized gland that sits just above your heart. The master gland of the immune system, one of the thymus' chief functions is to produce T lymphocytes, which are a type of white blood cell that works to prevent disease. In July 2000, a team of Harvard Medical School researchers at Massachusetts General Hospital, including Associate Professor of Medicine David Scadden, unveiled a man-made structure that mimics the thymus by churning out human T cells. The building blocks for this "organoid" were CellFoam, a synthetic material manufactured by Cytomatrix of Woburn, Mass., and tissue from humans and mice.