Assay Based on Oxygen Consumption Rate May Enable Reliable Assessment of Adipose Tissue Viability

Goals/Purpose: Autologous fat grafting is a common procedure in aesthetic plastic surgery. However, the rates of graft retention vary due to a lack of standardized protocol for adipose tissue (AT) harvest and processing. Historically, no such protocol has been developed in part because there is no reliable gold-standard assay available for the measurement of AT viability. We present a novel assay for the reliable assessment of AT viability based on quantifying the oxygen consumption rate (OCR) normalized to the DNA content (OCR/DNA).

Methods/Technique: Human AT was harvested: (1) fresh en bloc; or (2) using our standard clinical protocol (i.e., machine-assisted using a 6-mm cannula, under -250 mm Hg of suction pressure, and rinsed using the Revolve^TMsystem). AT was transferred into conical tubes, placed on ice immediately and transported to the laboratory for OCR/DNA measurements. Mean (±SE) cold ischemia time was 3.2 (±0.1) hours. Direct OCR measurements were done using a custom-designed stirred microchamber system (Instech Laboratories, Plymouth Meeting, PA). AT aliquots used for OCR measurements were then collected and the amount of AT was quantified using a commercially-available DNA assay (Quant-IT PicoGreen dsDNA kit, Invitrogen, Grand Island, NY) and spectrometer (SpectraMax M5 plate reader, Molecular Devices, Sunnyvale, CA). OCR/DNA values reflect the fractional viability of the AT sample. Each sample was assessed in quadruplicate. Data are presented as mean (±SE).

Results/Complications: OCR/DNA of fresh en bloc AT was 149.8 (±9.1) nmol/min/mg DNA. However, the OCR/DNA of post-processed AT preparations was 61.1 (±6.1) nmol/min/mg DNA, indicating a significant reduction (~60%) in the fractional viability of AT during standard harvest and processing. 

Conclusion: There is a critical need to develop reliable assays for the assessment of AT viability. OCR/DNA provides an accurate, real-time, quantitative, and operator-independent assay that may enable optimization of fat grafting protocol and should be studied further.