Regenerating Mice

The most interesting pieces of research have a way of turning up on sci.life-extension - the regulars there keep a good ear to the ground. In this case, the research in question is an examination of advanced regenerative capacities in a strain of mice:

The reaction of cardiac tissue to acute injury involves interacting cascades of cellular and molecular responses that encompass inflammation, hormonal signaling, extracellular matrix remodeling, and compensatory adaptation of myocytes. Myocardial regeneration is observed in amphibians, whereas scar formation characterizes cardiac ventricular wound healing in a variety of mammalian injury models. We have previously shown that the MRL mouse strain has an extraordinary capacity to heal surgical wounds, a complex trait that maps to at least seven genetic loci. Here, we extend these studies to cardiac wounds and demonstrate that a severe transmural, cryogenically induced infarction of the right ventricle heals extensively within 60 days, with the restoration of normal myocardium and function. ... The myocardial response to injury observed in these mice resembles the regenerative process seen in amphibians.

Understanding the process by which lower forms of animal life regenerate serious wounds has been a desirable goal for some time now:

Studies of expression profiles, functional assays, and cloning of mammalian orthologues of genes that promote regeneration are aimed at designing a molecular cocktail of genes and/or proteins that will reverse tissue damage and lead to regeneration from the body's own cells. The limb provides information that will lead to the regeneration of muscle, bone, skin, and nerves. The work on eye will help us regenerate lens, retina and optic nerve, and the studies of spinal cord to reverse paralysis.

It is interesting and potentially very promising that a similar regenerative process has been found in a mammal - indicating a much shorter, although still resource-intensive, jump to therapies that will work for human injuries.

Our laboratory has determined that the MRL mouse strain is unique in its capacity for regenerative wound healing, as shown by the closure of ear punches with normal tissue architecture and cartilage replacement reminiscent of amphibian regeneration as opposed to scarring. Furthermore, we have mapped the genes involved, identified a minimum of six different loci on five chromosomes, and shown that this is a complex multigenic trait.

Using this mouse strain in the present study, we show that the MRL heart, when injured with a cryoprobe, is capable of growing and replacing wounded tissue without fibrosis. We show that cardiomyocytes are capable of dividing near and filling the wound site with a mitotic index equivalent to that of amphibians. We also show that granulation tissue resolves quickly with restoration of normal myocardial architecture and a markedly reduced extent of scarring. Finally, myocardial function seems to recover from the injury.

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