Skin keratin correlates with bone and tendon collagen quality: a proof-of-concept clinical study using FTIR spectroscopy in shoulder arthroplasty patients.

Abstract

There is a current need for non-invasive approaches to clinically assess the quality of bone and tendon tissues. We hypothesize that skin keratin properties correlate with those of collagen in tendon and bone. Eight clinical patients undergoing shoulder arthroplasty were enrolled. We applied Fourier-transform-infrared(FTIR) spectroscopy to evaluate whether superficial skin composition reflected tendon and bone quality. Resultant data was analyzed for peak intensities and ratios reflecting the tissue content of specific molecules. In-situ FTIR spectra of skin showed peaks assigned to keratin and keratin/lipid content in the stratum corneum. Ex-vivo spectra of harvested bone and tendon showed peaks reflecting collagen quality and quantity, as well as tissue mineralization in bone. Significant correlations were observed between the content of keratin-specific FTIR signal in the skin and collagen quality in bone(r = 0.72;p < 0.05) and tendon(r = 0.76;p < 0.05), as well as between collagen quality in bone and tendon(r = 0.89;p < 0.05). Moreover, a correlation was found between the keratin/lipid content in skin and the degree of bone tissue mineralization(r = 0.70;p = 0.053). This preliminary study highlights the potential of FTIR assessment of skin as a non-invasive approach to assess bone and tendon quality, which could provide a cost-effective and non-invasive tool to aid in counseling patients considering musculoskeletal treatment.