23 October 2008

Male organ from one cell

Pyotr Smirnov, "Newspaper.Ru»No one has denied the theoretical possibility of growing an organ from a single cell for a long time.

For almost a century, the concept of a "stem cell" has existed in the scientific community, and successful attempts to grow animal tissues in culture are the same. But for the last 30-40 years, cell biology has been experiencing a real boom. Oddly enough, it is not associated with any phenomenal discoveries.

These studies have become large-scale due to the creation of an appropriate industrial infrastructure, which has provided hundreds, and now thousands of laboratories around the world with ordinary plastic cups, nutrient media and other "primitivism". Now the cells themselves have become the subject of commercial interest, and the most enterprising scientists have organized real research and production corporations, like Genentech, where Weiqiang Gao works.

And as we can see from the Gao article accepted for publication in Nature, "merchants" are not limited to the production of vaccines or routine tissue-engineered cartilage equivalents for meniscus replacement. They are able to grow an entire organ.

Gao and his colleagues in the department of molecular biology chose the object for their research for a reason: prostate dysfunction is one of the most common ailments for men over 50. And the intimate nature of the problem allows andrologists and pharmacologists specializing in this field to profit well from it.

Scientists proceeded from the hypothesis that in every organ, or rather the tissues of our body, there are stem cells necessary for the normal replacement of cells that are gradually dying or failing, as well as for the rapid restoration of the structure in case of serious damage.

This theory regularly receives inductive proof in the form of successful experimental experience with bone marrow, muscles, heart, liver, epithelium and even hair follicles.

But where are these stem cells to look for? How to distinguish them? After all, if you look through a microscope, it doesn't say "Stem" on the cell.

Often, stem cells are searched for, noticing the unusual structure of its surroundings. Each organ has its own so–called tissue niches – the corresponding microenvironment, which, on the one hand, maintains the state of "stemness", and on the other hand, provides the output and distribution of descendants throughout the tissue. For example, in the epithelium of the skin, progenitor cells are evenly distributed throughout the basal ("underlying") layer and are slightly concentrated in the area of hair follicles. And in the corneal epithelium, progenitors are located exclusively in the limbic zone – the ring, where the cornea passes into the opaque shell of the eye, the sclera.

Gao decided that the most stem cell-rich area in the prostate should be the tops of its lobules. The fact is that scientists have repeatedly noticed cyclical changes in the size of the prostate under the influence of hormones, and this gland is capable of regeneration if you leave this very "tip". This was the end of the intellectual work of naturalized Americans and the heavy laboratory routine began. Sections of the prostate were crushed, and each individual cell was typed in accordance with markers – the so-called differentiation clusters located on the surface.

The smallest was the population designated Lin-Sca-1+CD133+CD44+CD117+. The "+" icons are used to indicate the presence of markers, and the "–" is a reliable absence, so that the given designation symbolizes the presence of all the listed markers in the cell. These cells turned out to be slightly less than 1% of the total number, and scientists immediately suspected that stem cells were hiding somewhere here. As scientists later showed, the CD117 molecule is critically necessary for the normal development of the gland – if it is blocked in embryos, then in adult mice the prostate remains the same size.

But the breakthrough was the second part of the work – biologists injected 97 mice with one such cell under the kidney capsule, and in 14 cases they grew full-fledged prostates.

This approach simultaneously removes the problems that regularly arise before tissue engineers. Firstly, there is no need to take care of feeding areas far from the surface – the kidney is rich in blood vessels, and the "transplanted organ" not only receives the necessary nutrition, but also forms its own vascular network.

Secondly, although the main tissue, in this case glandular, develops from a transplanted stem cell, but the supporting tissues forming the capsule, separating the lobules, and so on, develop either from the recipient's material, or, as in the Gao experiment, from additionally injected rat connective tissue stromal cells.

So this approach of "intra-organ cultivation" of a new organ with subsequent transplantation remains the most promising so far. And since the study was not conducted in a state laboratory, it could not do without a practically significant component.

Biologists found exactly the same population of cells in the human prostate, however, in a concentration of only 0.2%.

But if we consider that in experiments on mice, a single cell was enough, then a piece of prostate of any size will be enough to grow a full-fledged gland. Moreover, it may not come to the creation of an entire organ: in case of myocardial infarction, damage to the nervous system or liver, it is enough to introduce stem cells that know better than scientists where to embed, who to displace and how long to multiply.

Portal "Eternal youth" www.vechnayamolodost.ru23.10.2008

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