Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 296

Bone marrow-derived stem cells for cartilage repair. The bone marrow is an important source of stem cells and is used extensively in the treatment of various conditions. Bone marrow is present in the center of long bones, with the highest concentration of stem cells present in the pelvic bone. Other sources of bone marrow stem cells include the long bones of the arm, leg, and the thigh. The bone marrow stem cells are aspirated using a needle and then concentrated using a centrifuge. Nucleated cells are separated using flow cytometry and 15 percent of this cellular population will consist of stem cells. Platelets are also constituents of this population of cells and, as platelets contain growth factors that aid in the synthesis of collagen matrix, like fibroblast growth factor, insulin-like growth factor-1 and transforming growth factor-B, they are essential to the cellular population. Finally, thrombin is added to the cellular mixture to cleave fibrinogen, which would then give rise to a fibrin scaffold that is essential to hold the stem cells and the growth factors together. This mixture is then injected into the damaged or the injured site. Though the body signals the movement of stem cells from the bone marrow to the injured site on its own, injecting stem cells speed recovery and also increases the concentration of stem cells at the site of injury.

Bone marrow-derived stem cells for tendon repair. Bone marrow stem cells are collected and then centrifuged to obtain the cellular concentrate, while the supernatant is stored for later use. The nucleated cells are isolated using flow cytometry and then cultured to increase the population of stem cells. The cells are grown in cell-culture medium for three weeks, until the cellular population of stem cells are in excess of 10 × 10⁶ cells. After the cells are cultured and their numbers increased, they are suspended in the supernatant of bone marrow, which was separated initially, to prevent contamination of cells or to prevent them from getting mixed with foreign cells. Also, as the supernatant is rich in growth factors, it would aid in the growth of the stem cells. This cellular mixture is then carefully injected at the site of tendon injury. The use of bone marrow mesenchymal stem cells in the treatment of tendon repair was associated with ectopic bone formation in rabbits; the use of embryonic stem cells in tendon repair, however, has resulted in the development of teratoma. The use of tendon stem cells in the repair of tendons has been found to be the most effective and such stem cells have been identified among humans, mice, rabbits, and rats. These tendon stem cells differentiate into tenocytes under normal conditions; however, when these cells are implanted with engineered matrix of tendon, then they result in tendon-like tissues.