Induced pluripotent stem cells (IPSCs) are reprogrammed cells - such as those obtained from a skin sample - and are similar to embryonic stem cells in the sense that it should be possible to generate any form of cell from them. They offer the capacity to easily generate unlimited numbers of patient-specific cells, or build tissue and organ structures from scratch. Each type of tissue or cell requires different chemical instructions, growth environments, and technical strategies to be discovered and then refined, however - and there are a few hundred types of cell in the human body. Here, researchers report on progress on generating cartilage from IPSCs:
[Researchers have] engineered cartilage from induced pluripotent stem cells that were successfully grown and sorted for use in tissue repair and studies into cartilage injury and osteoarthritis. ... [This] suggests that induced pluripotent stem cells, or iPSCs, may be a viable source of patient-specific articular cartilage tissue.
Articular cartilage is the shock absorber tissue in joints that makes it possible to walk, climb stairs, jump and perform daily activities without pain. But ordinary wear-and-tear or an injury can diminish its effectiveness and progress to osteoarthritis. Because articular cartilage has a poor capacity for repair, damage and osteoarthritis are leading causes of impairment in older people and often requires joint replacement.
One challenge the researchers sought to overcome was developing a uniformly differentiated population of chondrocytes, cells that produce collagen and maintain cartilage, while culling other types of cells that the powerful iPSCs could form.
To achieve that, the researchers induced chondrocyte differentiation in iPSCs derived from adult mouse fibroblasts by treating cultures with a growth medium. They also tailored the cells to express green fluorescent protein only when the cells successfully became chondrocytes. As the iPSCs differentiated, the chondrocyte cells that glowed with the green fluorescent protein were easily identified and sorted from the undesired cells.
The tailored cells also produced greater amounts of cartilage components, including collagen, and showed the characteristic stiffness of native cartilage, suggesting they would work well repairing cartilage defects in the body.