In mice, bone growth takes place in accordance with the same principles as when new cells are constantly produced in blood, skin and other tissue, stated new study published in the journal Nature.
This contradicts the previous understanding that bone growth depends on a finite number of gradually consumed progenitor cells. If the new findings also apply to humans, they could make an important contribution to the treatment of children with growth disorders. The growth of children's bones depends on growth plates (physes) situated close to the end of all long bones in the body. These plates consist of cartilage cells, chondrocytes, that form a kind of scaffold supporting the formation of new bone tissue, and that are themselves generated from stem-cell like progenitor cells called chondroprogenitors.
For long bones to grow properly, chondrocytes must be generated constantly throughout the growth period. The general view in the field has been that there is a limited number of progenitor cells that are formed during embryonic development and then consumed for bone growth until they run out and we stop growing. In an attempt to ascertain whether or not this is true, researchers at Karolinska Institutet decided to study the formation of chondrocytes in mice.
Such progenitor cell behaviour is typical for tissue that constantly produces many new cells, such as skin, blood and intestine. For such tissue types, it has been shown that the progenitor cells are situated in a very specific micro-environment, a stem cell niche, which helps to generate the necessary cells (e.g. skin and blood cells) but also enables the progenitor cells to renew themselves. If the niche is disrupted or dysfunctional, the progenitor cells become depleted and the tissue is damaged.
"If it turns out that humans also have this growth mechanism, it could lead to a significant reassessment of numerous therapeutic approaches used for children with growth disorders," says Dr Chagin. "The mechanism could also explain some previously puzzling phenomena, such as the unlimited growth seen in patients with certain genetic mutations."