They tweaked the stem cells' genes to pump up production of a bone-building protein called BMP-4. When mice with knee injuries got those stem cells, their knees healed better than other mice with the same injuries.
The finding comes from doctors including Ryosuke Kuroda, MD, PhD, of Children's Hospital of Pittsburgh and the University of Pittsburgh.
The experiment, described in Arthritis & Rheumatism, only included mice, not people. Joint damage is a hallmark of arthritis, and scientists don't have a way to make arthritis-damaged joints as good as new.
Healing an Injured Knee
Kuroda's team took stem cells from mouse muscles, placed the stem cells in chemical "glue," and used the mixture on mice with knee injuries.
Some mice got stem cells that had been genetically altered to make more BMP-4. Others got stem cells with normal genes. A third group just got the chemical "glue" with no stem cells.
The mice could move freely around their cages as their knee injuries healed. Their knees were checked after four, eight, 12, and 24 weeks.
The mice that got the genetically altered stem cells healed best by the study's end. They made glossy, white tissue that repaired the joint damage quite well, the study shows.
Healing attempts didn't go as well in the other mice. Their joint repairs were rougher and didn't last as long, like a half-hearted attempt to patch a hole in a wall that later crumbles.
The "glue" helped, write the researchers. Basically, the glue worked like spackle, putting the stem cells in the right spots and filling in little gaps. The glue might work better than solid grafts of tissue, write Kuroda and colleagues.
The results are "encouraging," writes Mary Goldring, PhD, in a journal editorial. Goldring is on staff at Harvard Medical School and the New England Baptist Bone and Joint Institute in Boston. She didn't work on Kuroda's study.