Laval University muscles in on the research scene

Researchers in Quebec use injections of myoblasts to fight muscular dysthrophy

By Raymond Reese

Three patients in Quebec who could face an untimely death from Duchenne Muscular Dystrophy (DMD) now have new hope. They've responded positively to a new potential treatment � an injection of cells that stops the muscle degradation.

The research was directed by Dr Jacques Tremblay, a clinical investigator at the Centre Hospitalier de l'Universit� Laval (CHUL) Research Centre and a professor at Laval University. The results will soon appear in the journal Molecular Therapy.

Muscular dystrophies, including DMD, which affects one boy out of every 3,500, are inherited diseases marked by the loss of skeletal muscle over time. DMD spells an early demise for victims, often before the age of 30. This devastating fate attracted Dr Tremblay to the field years ago after meeting some affected boys and their parents at fundraisers.

ZONING IN ON DYSTROPHIN
Dr Tremblay's team decided to attack DMD by zeroing in on a protein called dystrophin. The protein is made by skeletal muscle cells (collectively called myofibres) and keeps cell membranes hardy. The researchers transplanted healthy myoblasts � 'baby' muscle cells, which produce dystrophin as they develop � into a malfunctioning tibialis anterior muscle that controls the up and down movement of the foot.

As logical as myoblast tranplantation sounds, most researchers have shied away from this approach in light of clinical trial results a decade ago that didn't seem encouraging. Now, gene and stem cell therapies have paved the way to success with this technique.

The three patients had different mutations that destroyed the ability of myofibres to make dystrophin. Healthy myoblasts were obtained from each of the donors' fathers (who didn't have DMD). A series of 25 injections arranged in parallel lines in a 1cm3 area pumped about 30 million healthy myoblasts into the left leg muscles. The right leg muscles received cell-free saline. The immune system's predictable attempt to attack the myoblasts was blocked by the drug tacrolimus.

Four weeks later, small plugs of muscle were removed using a needle. These biopsy samples were used to assess cell structure, to see if dystrophin could be detected using special stains and to test for any rejection or death of the transplanted cells. As well, ultra-sensitive reverse transcriptase-polymerase chain reaction was used to detect any dystrophin produced by the healthy injected genes.

The injected myoblasts appeared healthy and, amazingly, were even producing dystrophin. On average, 10% of the muscle fibres obtained in each sample plug from every left leg muscle were producing dystrophin � "the result we were expecting based on animal models," says Dr Tremblay. No dystrophin was detected in the saline-injected muscles.

Dystrophin production occurred along the injection lines, since the injected cells tend to stay put. Increasing migration of the cells from the injection site is the next goal, as that would reduce the injections needed to improve a muscle.

While the present effect was too miniscule to be noticed by the patients, "the work is a new and very promising beginning for the treatment of a devastating genetic disease," says Roderick McInnes, Scientific Director of the Institute of Genetics of the Canadian Institutes of Health Research.