Skin cells replaced patients in clinical trials

Peter Baranov, Infox.ruGeneticists have managed to prove that stem cells created from the skin can be used to test potential drugs.

Now patients with rare genetic diseases will not have to swallow experimental drugs, every time playing the medical equivalent of Russian roulette.

Mice and rats alone are not enough to understand the causes of the disease or to test new drugs. We have to start with the cells isolated from the patients themselves. Sometimes this is not enough – it is difficult to get enough biological material from the liver, kidneys, and, especially, the brain. Lorenz Studer from the Sloan-Kettering Institute and his colleagues suggested using ordinary skin fibroblasts for this purpose, turning them into any tissue of choice.

Embryos can be discardedUnlike the personality as a whole, the fate of each individual cell is predetermined, and it is almost impossible to change it.

Thus, epithelial cells are capable of continuous division, constantly renewing the body's integuments. At the same time, they are not able to turn into, say, neurons, even though they originated from a single germ leaf in embryonic development. A variety of stem cells stand apart here – their abilities for both division and various transformations are somewhat broader. But in an adult, and they are seriously limited – the most "powerful" are located in the bone marrow and give rise to the whole variety of blood cells, but not the cells of the same liver or kidneys.

The most promising available to scientists until recently were embryonic stem cells (ESCs) isolated from the fetus up to a certain stage of development. Unlike all the others, they are able to transform into any cell of the body under the influence of the appropriate environment. Under experimental conditions, they have already managed to grow both heart muscle and teeth, not to mention hundreds of mice "cured" of dozens of diseases.

If it were not for the ethical issues associated with obtaining ESCs, problems of immunological compatibility, and the risk of developing tumors, they would have long been entrenched in clinical practice.

Pseudo - stem cellsThree years ago, a new member appeared in the stem cell family – induced pluripotent stem cells (iPSCs), which have the same properties as embryonic cells, but obtained with the help of a small genetic modification.

Four DNA sites (OCT4, SOX2, KLF4, and c-MYC) are embedded in the genome of a common mouse skin fibroblast. Since 2006, scientists have managed to abandon viruses to introduce these factors, reproduce the phenomenon for human cells, and even grow a mouse from IPSC.

The most obvious application of this technology is the cultivation of new organs and tissues to replace worn or damaged ones. The authors of the publication in Nature proposed a less tempting, but no less promising application – to use IPSC to study the causes and development of hereditary diseases.

A distinctive feature of all hereditary diseases is the presence of a defect in the genome of the zygote, and therefore in all cells of the body. For the work of some tissues, the mutation may be inconspicuous, and for others it is critical. 

Illness without tearsIn the case of Riley-Day syndrome, which became the object of the study, it is a mutation of the IKBKAP gene located on chromosome 9.

It occurs in 1 out of 30 Ashkenazi Jews and in one out of 3,000 other inhabitants of the Earth. However, for the manifestation of the disease, it is necessary that both copies of the gene are "defective" – clinical practice speaks of one child per 3,600 Ashkenazi newborns.

Riley-Day syndrome
(familial autonomic dysfunction) is an autosomal recessive disease that manifests itself in childhood. The probability of a sick child being born to parents carrying a defective gene is 25%. In this disease, there is a decrease in lacrimation, sweating, decreased pain sensitivity, loss of tendon reflexes, absence of mushroom papillae on the tongue and lability of blood pressure. Vomiting crises and fever often occur, which is associated with a decrease in the number of thin myelin and myelin-free nerve fibers. At the moment, only 590 cases of the disease have been described.

Ideally, studies of the molecular mechanisms of the development of this condition would need to be carried out on neurons isolated from patients. But, firstly, they are difficult to obtain in sufficient quantities, and secondly, they do not reproduce in culture in vitro. For this reason, all these procedures were carried out until recently on lymphocytes, also obtained from patients, but already from blood.

Studer and his colleagues managed to get enough "sick" neurons, but not from the brain or sensory organs of a 10-year−old patient, but from a sample of her skin. Naturally, at first they had to turn "defective" fibroblasts into "sick" iPSCs, and only then send the latter along the appropriate path of development.

Normal "defective" cellsThe method allowed the authors to clarify the details of the defective gene, showing how the growth, development and migration of nerve cells slows down.

But the most visible component of their work was the demonstration of the effects of potential drugs.

At the moment, there is no treatment for Riley-Day syndrome that can eliminate the cause of the disease (as well as for any other genetic disease). Therefore, doctors have to deal with the manifestations, preventing the development of the most lethal. Although the absence of tears or scoliosis can not be called fatal causes, but due to the combination of manifestations and their consequences, only half of the patients live up to 30 years.

If it were possible to find a drug that could compensate for the work of the defective gene as much as possible, and not affect very long-term consequences (artificial tears, antiemetics, massage, etc.), then this would greatly facilitate the work of doctors.

The authors took three substances that performed equally well in the mentioned tests on lymphocytes: the plant hormone kinetin, the antioxidant epigallocatechin gallate, and tocotrienol, belonging to the vitamin E group.

Although all these three substances "pressed" the work of the defective gene in lymphocytes quite well, only kinetin showed the same effect when injected into "sick" neurons obtained from IPSC. A month of therapy practically returned the nerve cells to a healthy state, although it never fully restored their ability to migrate.

It is too early to talk about clinical trials of kinetin, and it is unlikely that it will be possible to recruit the necessary number of volunteers from doctors – only 350 patients with Riley-Day syndrome are now known on the whole planet. But Studer clearly demonstrated that general biological laws work not only for completely normal, but also for "defective" cells.

Portal "Eternal youth" http://vechnayamolodost.ru26.08.2009