Polarization in Raman spectroscopy helps explain bone brittleness in genetic mouse models.
Raman spectroscopy (RS) has been extensively used to characterize bone composition. However, the link between bone biomechanics and RS measures is not well established. Here, we leveraged the sensitivity of RS polarization to organization, thereby assessing whether RS can explain differences in bone toughness in genetic mouse models for which traditional RS peak ratios are not informative. In the selected mutant mice - activating transcription factor 4 (ATF4) or matrix metalloproteinase 9 (MMP9) knock-outs - toughness is reduced but differences in bone strength do not exist between knock-out and corresponding wild-type controls. To incorporate differences in the RS of bone occurring at peak shoulders, a multivariate approach was used. Full spectrum principal components analysis of two paired, orthogonal bone orientations (relative to laser polarization) improved genotype classification and correlation to bone toughness when compared to traditional peak ratios. When applied to femurs from wild-type mice at 8 and 20 weeks of age, the principal components of orthogonal bone orientations improved age classification but not the explanation of the maturation-related increase in strength. Overall, increasing polarization information by collecting spectra from two bone orientations improves the ability of multivariate RS to explain variance in bone toughness, likely due to polarization sensitivity to organizational changes in both mineral and collagen.
Tennessee Valley Healthcare System, Department of Veterans Affairs, Nashville, Tennessee 27212, United StatesbVanderbilt University, Department of Biomedical Engineering, Nashville, Tennessee 37232, United StatescVanderbilt University, Vanderbilt Center f.
Alexander J
AJ
Makowski
Vanderbilt University, Department of Biomedical Engineering, Nashville, Tennessee 37232, United States.
Isaac J
IJ
Pence
Vanderbilt University, Department of Orthopaedic Surgery and Rehabilitation, Nashville, Tennessee 37232, United States.
Sasidhar
S
Uppuganti
Vanderbilt University, Department of Biomedical Engineering, Nashville, Tennessee 37232, United States.
Ahbid
A
Zein-Sabatto
Vanderbilt University, Department of Biomedical Engineering, Nashville, Tennessee 37232, United States.
Meredith C
MC
Huszagh
Vanderbilt University, Department of Biomedical Engineering, Nashville, Tennessee 37232, United States.
Anita
A
Mahadevan-Jansen
Tennessee Valley Healthcare System, Department of Veterans Affairs, Nashville, Tennessee 27212, United StatesbVanderbilt University, Department of Biomedical Engineering, Nashville, Tennessee 37232, United StatescVanderbilt University, Vanderbilt Center f.
Jeffry S
JS
Nyman
D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology*; D005260:Female; D005269:Femur / Q000737:chemistry* / Q000503:physiopathology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008859:Microscopy, Polarization / Q000379:methods*; D015999:Multivariate Analysis; D013059:Spectrum Analysis, Raman / Q000379:methods*; D055114:X-Ray Microtomography