Collagen Fibrils in Skin Orient in the Direction of Applied Uniaxial Load in Proportion to Stress while Exhibiting Differential Strains around Hair FolliclesReport as inadecuate




Collagen Fibrils in Skin Orient in the Direction of Applied Uniaxial Load in Proportion to Stress while Exhibiting Differential Strains around Hair Follicles - Download this document for free, or read online. Document in PDF available to download.

Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA



These authors contributed equally to this work.





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Academic Editor: Amir A. Zadpoor

Abstract We determined inhomogeneity of strains around discontinuities as well as changes in orientation of collagen fibrils under applied load in skin. Second Harmonic Generation SHG images of collagen fibrils were obtained at different strain magnitudes. Changes in collagen orientation were analyzed using Fast Fourier Transforms FFT while strain inhomogeneity was determined at different distances from hair follicles using Digital Image Correlation DIC. A parameter, defined as the Collagen Orientation Index COI, is introduced that accounts for the increasingly ellipsoidal nature of the FFT amplitude images upon loading. We show that the COI demonstrates two distinct mechanical regimes, one at low strains 0%, 2.5%, 5% strain in which randomly oriented collagen fibrils align in the direction of applied deformation. In the second regime, beginning at 5% strain, collagen fibrils elongate in response to applied deformation. Furthermore, the COI is also found to be linearly correlated with the applied stress indicating that collagen fibrils orient to take the applied load. DIC results indicated that major principal strains were found to increase with increased load at all locations. In contrast, minimum principal strain was dependent on distance from hair follicles. These findings are significant because global and local changes in collagen deformations are expected to be changed by disease, and could affect stem cell populations surrounding hair follicles, including mesenchymal stem cells within the outer root sheath. View Full-Text

Keywords: second harmonic generation microscopy SHG; fast fourier transform FFT; collagen orientation index; digital image correlation DIC; strain mapping second harmonic generation microscopy SHG; fast fourier transform FFT; collagen orientation index; digital image correlation DIC; strain mapping





Author: Sterling Nesbitt †, Wentzell Scott †, James Macione † and Shiva Kotha *

Source: http://mdpi.com/



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