Many repair works in our organisms are performed by hard workers, known as stromal progenitor cells, which participate in forming new tissues and extracellular matrix. When we get old, we lose the majority of these cells, which causes bone thinning in elder people, for instance. Russian medics and microbiologists have found out that age-related changes in the population of stromal progenitor cells was not caused only by decreasing numbers of these cells, but also by inhibiting their activity by an organism himself.

In order to understand, how age affects activity of stromal progenitor cells, Russian researchers have performed two experiments. First one consisted of several transplantations between young (two months old) and old (two years old) mice. A donor, which was either young or old, gave a piece of its spleen or bone marrow to a recipient, which was also young or old. After two months, transplants were removed, turned into a cell suspension, which was cultivated. Later researchers counted number of stromal progenitor cells, which in culture form fibroblast colonies.

A transplant or graft is a chimerical organ, in which all stem cells and their descendants belong to a donor, and all surrounding cells and tissues – to a recipient. Scientists have compared condition of drafts in different groups of recipients and revealed that amount of stromal progenitor cells in bone marrow dropped 2.5-3 times with age and 3 times more with organism’s regulating force. This means these cells are present in an organism, but they don’t do anything. When these cells change their “habitat” from an old mouse to a younger one, they start proliferating. The same, even more powerful effect of organism forces was detected in the cells of spleen.

 

 

The second experiment of researchers from Moscow was aimed at studying bone formation. The scientists used the ability of a urinary bladder mucosa to excrete substances, which activate progenitor cells of bone marrow. After transplanting a fragment of urinary bladder mucosa into an abdominal wall, where there are plenty of progenitor cells, one can observe formation of ectopic bone tissue, which isn’t supposed to appear there. As in the previous experiment, donors and recipients are both young and old, but this time they were guinea pigs. After nineteen days after transplantation, researchers have estimated the mass of a newly-formed bone tissue. Surprisingly, the largest bones formed after transplanting a piece of urinary bladder mucosa from an old guinea ping to a young one. This means that with age the ability of urinary bladder mucosa to stimulate bone formation enhances, however, this doesn’t happen in an organism of an old guinea pig either due to presence of some internal mechanisms, which hamper bone tissue formation, or due to absence of some mechanisms, that promote bone formation.

Researchers strongly believe that results of their study will help better understand what causes age-related defects of bone tissue.