Breaking down fat: Quality control and release criteria for SVF-based products

by Alexey Bersenev on May 9, 2015 · 1 comment

in adipose

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Since FDA views adipose-derived stromal vascular fraction (SVF) as a “drug”, it is important to discuss quality control testing. Even if you will operate under different jurisdiction, where SVF is not a drug, you want to make sure that quality of fat tissue processing device output will not possess any risks to your patients. So, before get started with patients, you better validate the device by measuring quality its output (SVF). Under FDA jurisdiction, you should establish quality control testing and release criteria for every SVF product before administration. Since autologous SVF usually used in “point-of-care” settings, these QC tests should be minimal and very rapid. The most important and feasible quality parameters should be used as release criteria for SVF product.

Viability is the most important quality control criteria of adipose tissue processing. There is a number of methods (manual and automated) to assess viability of freshly isolated cells in suspension. The most popular (but not the most accurate) method is using viability dye Trypan Blue. Viability testing should not take more than 10-15 min. Viability as release criteria will depend on your tissue processing method and could be set after device validation. The typical viability for SVF could be set as >50% or >60-70%.

Cell yield
Very useful quality parameter, but not necessarily release criteria. Measured as number of cells per gram of tissue or per ml of lipoaspirate. SVF yield is highly depend on methodology and device for adipose tissue processing. Yield is one of the most important characteristics of processing device output.

The risk of contamination during point-of-care processing, using single use disposables, is minimal. However, regulators may ask about testing it, since processing is not performed in clean rooms and may have a risk for materials integrity (centrifugation). The only rapid, currently available sterility test, is a Gram stain. It could be done within 30 min. Because it captures very limited spectrum of microorganisms, usual sterility testing (aerobic and anaerobic with readout of 5-14 days) for cell products may be considered. Results of these sterility tests could be used for investigations of adverse events cases.

Level of residual enzymes
This is very specific test for adipose tissue processing. Even though clinically acceptable levels of residual enzymes are not established in toxicology, it could cause allergic reactions and tissue damage. The biggest safety concern here is a residual collagenase. This enzyme is the most frequently used for adipose tissue processing. It is bacteria-derived product. Residual collagenase level is highly dependent on type of processing device, in particular how well SVF was washed before final formulation. Some kits commercially available for testing of enzyme levels (ex: EnzChek assay). It is important to test during validation, but there is no consensus on use of residual enzyme level as release criteria.

Because “tissue processing enzymes” usually derived from bacteria, level of endotoxin should be measured in final product. Endotoxin test could replace routine residual enzyme level assay. There are few rapid commercially available test systems for endotoxin. This test is good to have in your release criteria.

Phenotypic product composition
Cellular composition of SVF could be tested by flow cytometry. It is important to do for validation of your process/ device. In point-of-care applications of autologous SVF is not feasible to perform before product release.

As an example of SVF product release criteria, I’d proposed the following:

  • viability >70%
  • Gram stain – negative
  • Endotoxin <5EU/kg or <0.5EU/ml (depends on test)

This post is a part of series Breaking Down Fat. In this series we will talk about identification, characterization and clinical processing of potentially therapeutic cell populations from adipose tissue. We started this series in response to the growing trend of wide (mostly uncontrolled) clinical use adipose-derived cells and some controversies/ misconceptions in the field.If you would like to contribute to this series or become a sponsor, please contact us!

{ 1 comment… read it below or add one }

Lara December 1, 2015 at 7:33 am

regarding evaluation of cell yield, what methodology and device are available to establish this parameter!
thank you


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