November 30, 2020

The Niche

Knoepfler lab stem cell blog

SVF & CAL are two fat stem cell acronyms generating a lot of buzz

Two emerging acronyms in the for-profit stem cell world that remain unknown to most academic stem cell scientists, but that are generating the most buzz are:

SVF and CAL.

These are two fat acronyms.


These acronyms relate to adipose (fat) stem cell-based procedures.SVF

SVF stands for “stromal vascular fraction”.

SVF is, for lack of a better word, a fat extract. There is even a wiki page on SVF (which has the model image above) that is mostly accurate, but needs some work.

To make SVF (a helpful review paper describes how to make SVF),  fat isolated by liposuction is processed by collagenase treatment and centrifugation: all the goodies at the bottom of the tube including a whole bunch of different cell types (only one of which is mesenchymal stem cells: MSCs) constitute the SVF.

SVF in fact contains many cell types including mesenchymal stem cells, pre-adipocytes (fat precursor cells), endothelial and pre-endothelial cells, stromal cells and non-cellular elements. Importantly, despite the heterogeneity of SVF, many doctors also simply call it “stem cells”, which seems misleading to patients.

SVF is clearly a biological drug and has been defined as such by the FDA, but most physicians today doing transplants of SVF do not have an IND and are hoping to just forget that whole FDA thing.

SVF can be cultured in a lab prior to transplantation into patients. Culturing seems to inherently change the properties of the cellular population as evidenced by decreased expression of the surface marker CD34 and increased CD105. Such culturing would also appear to inherently alter SVF in other ways that remain uncharacterized at this time.

CAL means “cell-assisted lipotransfer”.

If you’ve ever been to Jamba Juice you know all about the BOOSTS that they will add to your drinks: Heart health, Antioxidant, Green Tea, Immune Boost, etc.

Well, CAL is an autologous stem cell procedure that is basically a fat transfer procedure with a boost of SVF to increase its potency.

The apparent first paper on CAL can be read here.

It appears that the breast reconstruction that breast cancer survivor Suzanne Somers had was a CAL-like procedure.

“This is the first clinical trial,” says Somers, “so I was the first woman to legally re-grow her breast using stem cells.”

The procedure is called Cell Assisted Lipotransfer. Fat is sucked out of the stomach, half is harvested for stem cells, which are then added to the remaining half, and re-injected into the breast. Suzanne says a lumpectomy and radiation left her breasts lopsided.

“This clinical trial that I started after completion will make this subject to being FDA approved, and paid for by insurance,” says Somers.

Unfortunately I was not able to find any evidence of Somers’ procedure being part of any formal clinical trial. However, perhaps it is out there in the website and I just can’t find it. Anyone know?

CAL too is also a biological drug to be regulated by the FDA, but as with SVF, most docs doing CAL don’t worry about that whole regulatory thing. And so often these procedures are being done in a non-homologous clinical context as well.

In my opinion SVF and CAL have real clinical promise, but they need to be studied in the context of clinical trials. There are some ongoing, but not nearly enough (10 for SVF and just 1 for CAL).

Meanwhile, hundreds of physicians around the world are doing transplants of SVF and doing CAL without regulatory approval.

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