What is Stem Cell
What adipose-derived stem cells are
From the definition of the cell population obtained from fat, through the four possible sources, to how it differs from PRP.
The stromal vascular fraction, or SVF, is what remains of adipose tissue once the fat cells are removed: a mixed population of cells. It contains adipose-derived mesenchymal stem cells (ADSC) along with endothelial cells, pericytes, immune cells and growth factors. Much of what is described as a "stem cell injection" in practice uses this fraction rather than a single purified cell type.
What is inside 1cc of fat
Adipose tissue is not made of fat cells alone. Blood vessels run between them, and cells involved in regeneration gather around those vessels. When harvested fat is broken down with collagenase and centrifuged, the light fat cells float and a cell pellet settles below. That lower layer is the stromal vascular fraction.
Adipose-derived mesenchymal stem cells
ADSC. Able to differentiate into several tissue cell types, with a tendency to migrate towards damaged sites.
Endothelial cells and pericytes
The cells that form and maintain blood vessels. Tissue regeneration also requires blood supply to be restored.
Immune cells
Macrophages and other immune cells are included, and are involved in regulating the inflammatory response in tissue.
Growth factors and cytokines
Beyond differentiation itself, signalling molecules act to support the recovery of surrounding cells.
Because it is a mixture rather than one cell type, saying "a population of cells that includes stem cells is injected" is more accurate than saying "stem cells are injected".
How the cells in the fraction are identified
Since it is a mixed population, research identifies the cell types by surface markers.
| Cell | Markers used | Role in tissue repair |
|---|---|---|
| Adipose-derived MSC (ADSC) | CD73, CD90, CD105 positive / CD45 negative | Differentiates into several tissue cell types and secretes growth factors |
| Haematopoietic lineage | CD34 positive | Discussed in relation to blood vessel formation |
| Endothelial cells | CD31 positive | Line the vessel wall and contribute to restoring blood supply |
| Pericytes | CD146 positive | Wrap and stabilise vessels, and are discussed as a source of stem cells |
| Immune cells such as macrophages | CD45 positive | Regulate inflammation and clear damaged tissue |
Marker combinations and proportions are defined slightly differently across studies. The table gathers widely used criteria, and actual proportions vary with age, body composition and harvesting site.
Why the same fat gives different results
What ends up in the syringe is decided by six things, and equipment alone is not one of them.
| Variable | What changes | How this lab handles it |
|---|---|---|
| Harvest site and layer | The proportion of living cells differs by layer | The dense middle layer is selected |
| Suction pressure and cannula | High pressure or a narrow cannula damages cells | Harvested by surgeons averaging 29 years in practice |
| Enzyme conditions | Concentration, temperature and time drive recovery and damage | GMP-grade collagenase under fixed conditions |
| Centrifugation | Speed changes which layer is recovered | Separation completed within 45 minutes |
| Time outside the body | Survival falls the longer cells are outside | Operating room and lab are one floor apart |
| Freezing and thawing | Some cells are lost in the freeze-thaw cycle | Storage at -196℃, with recovery rate factored into the amount stored |
What injected cells do
The action is usually described in three ways, and the three happen at once.
Homing
Injected cells migrate towards sites emitting damage signals. This is the basis for describing intravenous delivery as reaching the areas that need it.
Differentiation
Undifferentiated cells divide and change into other tissue cells as required, including cartilage, skin and vessels.
Paracrine action
Even without changing themselves, the cells secrete growth factors and cytokines that support recovery in surrounding cells. Recent work weights this action heavily.
Where the cells come from changes things
Stem cells can be obtained from cord blood, bone marrow, blood or fat. Rather than one being better outright, the choice follows the purpose and the burden of harvesting.
| Item | Cord blood | Bone marrow | Blood | Fat |
|---|---|---|---|---|
| How it is obtained | Collected at birth | Marrow aspiration from the iliac bone | Venous draw then centrifugation | Liposuction |
| Burden | Timing is fixed | Invasive | Low | Small volume under sedation |
| Cell yield | Limited | Very low | Low, culture usually needed | Highest |
| Repeat harvest | Not possible | Heavy burden | Possible | Possible |
| Mainly used for | Storage | Bone and joint repair | Skin and pain | Body, skin, joints, hair, whole-body |
The cell yield from fat is reported at roughly 100 to 1,000 times that of bone marrow. Actual yield varies considerably with harvesting site, age, body composition and technique, so it needs to be assessed individually in consultation.
Terms that get confused
SVF
Stromal vascular fraction. The cell population obtained from adipose tissue once fat cells are removed.
ADSC
Adipose-derived mesenchymal stem cells. The stem cells contained within the fraction.
MSC
Mesenchymal stem cells. A type of adult stem cell obtained from marrow, fat or cord blood.
BMAC
Bone marrow aspirate concentrate. Marrow that has been aspirated and concentrated, so marrow-derived rather than adipose-derived.
ECM
Extracellular matrix. The structure cells sit in and function within. It is not the cells themselves.
Adult stem cells
Stem cells obtained from tissue in an already born body. This is the type used in actual treatment today.
How it differs from PRP
Both use something taken from your own body. What differs is what is taken.
| Item | Stem cell injection (adipose-derived SVF) | PRP (autologous plasma) |
|---|---|---|
| Source | Adipose tissue, harvested under sedation | Blood, drawn from a vein |
| What is obtained | A cell population including stem cells | Platelets and the growth factors they carry |
| Contains cells | Yes | Growth factor centred, not a stem cell population |
| Burden of harvesting | Higher, sedation required | Low, a blood draw |
| Storage | Remaining cells can be frozen at -196℃ | Prepared and used on the day |
Neither is superior in every case. PRP has a far lower harvesting burden, while a cell population can be stored and reused. Which is appropriate depends on the site, the purpose and the condition of the individual, and should be decided after examination and consultation.
Frequently asked questions
Is a stem cell injection the same as an SVF injection?
In most cases what is injected is the stromal vascular fraction, a mixed population that contains stem cells rather than purified stem cells alone. Describing it as a cell population that includes stem cells is the accurate wording.
Do results appear immediately?
Cell therapy works through tissue repair, so change is generally observed over weeks to months rather than immediately. The extent and the timing vary between individuals, and treatment does not produce the same result in everyone.
Are the cells cultured to increase the number?
Not at this lab. Cells are isolated and used on the same day without culturing. Culturing and expanding autologous cells requires a separate regulatory route under Korean law on advanced regenerative medicine.
How much fat needs to be harvested?
It depends on the purpose and on how many cells are needed. Yield tends to fall with age and varies with body composition, so the amount is decided at consultation after examination.
What are the side effects?
Harvesting involves sedation and a small liposuction procedure, so bruising, swelling and discomfort at the harvest site can occur. As with any injection, infection and inflammation are possible.
Whether treatment is appropriate should be decided after adequate examination and consultation, and any existing condition or medication should be disclosed beforehand.