Fat or adipose tissue is mainly located in the subcutaneous tissue layers. It is also called the adipose organ and has several important functions. Fat is characterized by two compartments: the fraction with adipocytes or fat cells and the stomal-vascular fraction (SVF). The adipose derived stem cells (ADSCs) are found within the SVF and located near the blood vessels. Those stem cells can be isolated and used for tissue engineering applications or regenerative medicine. They were discovered in 2000. The fat cell or adipocyte is of course the main player in fat tissue and is a highly dynamic cell. Each adipocyte is in close approximation with a blood vessel; fat is highly vascularized. The content of a fat cell consists mainly of an oil droplet that occupies 90% of its intracellular volume.
One of the crucial functions of fat is to cover muscles, nerves, blood vessels, bone or tendons. Fat is a soft tissue that covers other anatomical structures. When trauma occurs or surgery resects tissue, tissue deficits or tissue deficiencies are the result. Aging or loosing weight also thins the subcutaneous tissue layers. Fat is the ideal tissue to add volume, to cover tissue deficits or restore the body contour. Plastic surgeons use fat tissue because it is easily accessible (underneath the skin) and easy to shape. Lipofilling is an ideal technique because fat is removed with liposuction through small incisions (3 mm) and the fat is re-injected with small cannulas.
Lipofilling injects fat that has been removed with liposuction. The surgeon performs a liposuction, processes the fat (washing or centrifugation) and re-injects it. The main challenge in lipofilling is to have a maximal survival of the injected cells. An overall survival rate of 50 to 60 % is considered a good clinical result. Injected fat survives initially through a process called imbibition: the cells “drink” plasma or fluids from their environment to survive. After 48 hours new blood vessels will start to sprout from pre-existing vessels and will start to grow towards the injected cells. This is called angiogenesis (revascularization). Eventually, the newly formed blood vessels will nourish the injected fat cells and will transport nutrients and oxygen to the fat cells. The fat cells that failed to be revascularized will disappear. This is called resorption.
Stem cells have been discovered in adipose tissue. The concentration of stem cells within adipose tissue is even higher compared to bone marrow. The stem cells in adipose tissue (adipose derived stem cells or ADSCs) are easily accessible and can be isolated with liposuction. However, lipofilling shouldn’t be called a “stem cell technique” but the stem cells within adipose tissue do have a beneficial effect on the tissue quality. Probably, the cells within the SVF (stromal vascular fraction) play a role in the beneficial effect and not only the stem cells.