ARLINGTON, Va., April 11, 2002 --- The research lab that made headlines last year for turning fat cells into cartilage has taken the work a step further by successfully implanting the altered cells in mice.
This demonstrates the potential of taking stem cells from one tissue and turning them into cells of other tissues for use as implants in treating injury and disease.
Since cartilage has few blood vessels, nerves and lymphatic support, it has a limited capacity for repair when damaged. This makes cartilage an especially good candidate for replacement by engineered tissue.
"For patients with tissue damage, we envision being able to remove a small piece of fat, and then growing customized, three-dimensional pieces of tissue which would then be surgically implanted where needed," said Whitaker investigator Farshid Guilak, Ph.D., director of orthopedic research at Duke University.
Guilak and his colleagues have also used fat cells to produced cells that can make bone and, of course, fat. The ultimate goal of the work is to develop replacement cells and tissues by tapping into the regenerative power of stem cells.
Stem cells are the mother cells of various tissues of the body. They reproduce themselves and, at the same time, give rise to different cell types that become skin, bone, blood and other living tissues.
Recent research suggests that stem cells from one tissue can be reprogrammed to make cells of another tissue. The ability to isolate and manipulate stem cells have opened new avenues of research for treating injury and disease.
Embryonic stem cells can develop into virtually any cell type in the body. They are the subjects of widespread interest and controversy. President Bush has stopped federally funded research involving new lines of embryonic stem cells. This has accelerated the search for stem cells in adult tissue.
"We have found a new source of adult stem cells that can be changed into different cells and tissues," said M. Quinn Wickham, a Duke University medical student who works in Guilak's lab.
In the animal studies, fat cells left over from liposuction were filtered to isolate a colony of cells rich in stem cells. These were grown in a chemical and physical environment that encourages the growth of cartilage. It was important to feed the cells growth factors and culture them in a three-dimensional configuration to simulate the way cartilage cells grow naturally.
Fat cells grown in this way began to produce collagen, a main ingredient of cartilage. When these cells were implanted under the skin of mice, they continued for three months to produce collagen and other ingredients in a matrix characteristic of cartilage.
It is unlikely that one source of stem cells can be used to treat a wide variety of medical problems and disease, Guilak said. "But different clinical problems could be addressed by using adult cells taken from different spots throughout the body, without the same ethical concerns associated with embryonic stem cells."
Results of the study were published in the journal Biochemical and Biophysical Research Communications.
In a related study, fat cells were taken from a pad of fat that lies behind the knee cap (patella). Cells can be harvested from this area using a minimally invasive procedure that is less disruptive than liposuction. Similar deposits are also found in various other connective tissues throughout the body.
The researchers took fat pads from patients whose knee joints were removed during total joint replacement surgery and extracted a population of connective tissue (stromal) cells believed to be rich in stem cells.
Three groups of these cells were placed in three different environments and given steroids and growth factors that would encourage the growth of cartilage, bone and fat.
After a period of weeks, the cell cultures were examined. The first group had developed collagen matrix molecules characteristic of cartilage. The second group developed calcium phosphate deposits as if they were beginning to build a structure of bone. The third group began producing fat cells.
The results suggest that stem cells taken from fatty tissue can be reprogrammed into various other types of cells.
Any human applications of this work would be years away, but the research group is encouraged and continuing the work. Collaborating with the Duke team was Dr. Jeff Gimble of Durham, N.C.-based Artecel Sciences, who holds the patent for the process of isolating these cells from fat. Guilak is a consultant for Artecel Sciences.