Patient Specific Biomechanical Properties of Human Adipose TIssue
Jaime L. Bernstein, BS, Julia Jin, BS, Yoshiko Toyoda, BA, Philipp Franck, MD, Peter A. Torzilli, PhD, John P. Morgan, PhD, Jason A. Spector, MD.
Weill Cornell Medical College, New York, NY, USA.
BACKGROUND: Tissue stiffness is increasingly recognized as a crucial modulator of cell behavior, and vice-versa. Despite the ubiquity of adipose tissue throughout the body, little information exists about the biomechanical properties of human adipose tissue . Understanding these properties and how adipose tissue from various anatomical locations differs is not only crucial to the field of tissue engineering, but has the potential to enhance outcomes in aesthetic and reconstructive surgery. We aim to map the biomechanical properties of adipose tissue from various locations in the human body.
METHODS: All tissue samples were obtained from discarded post-surgical specimens. 1x1 cm tissue samples were taken from the suprascarpa (SS) and infrascarpal (IS) adipose layers, as well as the omentum and breast when possible. ElectroForce-3200 Series III was used for mechanical confined compressive studies. The force and displacement of deformation for each sample was collected and plotted using MATLAB (MathWorks, MA). A linear regression was performed and elastic modulus was defined as the slope of the linear portion of the compression curve. Samples of each patient's adipose tissue from various locations was tested, averaged, and compared using a two-tailed unpaired t-test.
RESULTS: Compression curves showed SS and IS adipose had an average elastic modulus of 36.83 kPa and 26.81 kPa (less stiff), respectively. This is consistent with the gross observation that SS adipose tissue has lobules smaller in size when compared to IS fat which correlates to an increase in the amount of connective tissue, corresponding with the significant increase in stiffness in the SS compared to the IS adipose layer (p=0.0101). Linear regression showed a significant correlation between age and elastic modulus of abdominal fat, with fat from older patients demonstrating a significantly greater stiffness (p=0.0227, R2=0.68). Breast and omentum showed an average elastic modulus of 39.33 and 22.22 kPa, respectively. Interestingly, omentum showed the most tightly clustered data points with a standard deviation of only 4.86 kPa between multiple patients, compared to the other fat types with standard deviations ranging from 10-20 kPa. These data suggest that omentum is the most consistent fat tissue between patients, regardless of demographics.
CONCLUSIONS: We have begun to explore the biomechanical properties of various human tissues and have shown for the first time that there is a significant difference in elastic modulus (stiffness) between the SS and IS abdominal fat layers. Further we have demonstrated that abdominal fat stiffness of both sub-types increases with age, yet omental fat does not appear to differ as much between patients. Describing and understanding tissue biomechanical properties is crucial for both research (e.g. creation of more accurate biomimetic platforms) and clinical (choosing the proper donor site, implications for autogenous fat transfer and suction assisted lipectomy outcomes, etc.) applications.
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