After many years of frustrating studies, a team of researchers and surgeons from the University of Minnesota in Minneapolis (USA) has been successful in an endeavour that could have a major impact in the clinical field: it has identified and described human bone stem cells, capable of generating other bone cells and cartilage, and these alone. In fact, for a long time various groups of international researchers had been focusing their attention on so-called mesenchymal stem cells (found predominantly in bone marrow), which appeared to be able to reconstruct skeletal tissue (bone, cartilage, fat, muscle, fibroblast, endothelial cells and stroma), but with irregular and often disappointing results.
Up to now, however, no team of researchers had been able to identify the stem cells that produce bone or cartilage alone in this complex “hotchpotch” of stem cells. The researchers from Minneapolis finally managed, using highly-advanced genetic markers (which enabled them to distinguish the different types of stem cells), and have described their findings in the respected journal Cell.
In an initial phase the researchers identified the bone stem cells of laboratory animals: in particular, in transgenic mice (i.e. mice whose DNA had been modified through genetic engineering) called “rainbow mice”, because the different stem cell types in these animals had different colors. However, since rainbow humans do not exist, the search for similar human cells proved difficult and disappointing… After many other attempts, the US researchers concentrated on the cells of a femur of a 17-week-old aborted fetus (this type of study, with the authorisation of the parents and the Bioethics Committee, is permitted in the United States).
The researchers “sequenced” the genetic code of various cell types, found in different points of the bone, looking for those with similar characteristics to the isolated stem cells in laboratory animals, and in the end they identified cells taken from the fetal bones that were capable of forming new bone and cartilage alone, without the development of any muscle or other tissue. These kinds of tests were then repeated on bone fragments taken from adult patients during joint replacement surgery. However, the scientists are going one step further. The stem cells of human bones, according to the researchers, can also be found inside human adult fat (including the fat that is removed through liposuction). If these studies are confirmed, there will be opportunities to have abundant quantities of stem cells to use, in the future, to repair bone damaged by trauma or osteoporosis.
