Dermal organization in scleroderma: The fast Fourier transform and the laser scatter method objectify fibrosis in nonlesional as well as lesional skin

Scleroderma, a chronic, progressive disorder, is characterized by dermal fi brosis with collagen bundles orientated parallel to the epidermis. Simple o bjective parameters to evaluate disease progression and therapies are neede d. We describe two methods, the laser scatter method and the fast Fourier t ransform (FFT), to measure collagen bundle orientation and spacing. Lesiona l sclerodermic skin (LS), nonlesional sclerodermic skin (nonLS), and contro l skin (CS) sections were evaluated for orientation ratio using the laser s catter method. The FFT was used to calculate orientation ratio, variation, and spacing of collagen bundles. Parameters were correlated with local and mean skin score measurements, on a scale of 0 (normal) to 3 (severely scler otic). With both the laser scatter method and the FFT, orientation ratios o f LS (respectively, 2.16 +/- 0.33 and 1.83 +/- 0.62) were significantly hig her than CS (respectively, 1.70 +/- 0.35 and 1.38 +/- 0.15). NonLS orientat ion ratios (respectively, 1.92 +/- 0.15 and 1.48 +/- 0.44) were between LS and CS ratios. Orientation variation and bundle spacing of LS (respectively , 57.3 +/- 19.4 and 15.7 +/- 5.6 mu m) were significantly reduced compared to CS (respectively, 73.8 +/- 15.0 and 18.9 +/- 1.9 mu m). NonLS orientatio n ratios (respectively, 57.2 +/- 29.0 and 15.6 +/- 6.1 mu m) were similar t o LS. Bundles in LS are more parallel, show less variation in orientation, and are more densely packed than in CS. There was a linear correlation betw een mean skin score and orientation ratio. Local skin score was not linearl y correlated to orientation ratio. Our findings suggest that nonLS dermis w ithout clinical sclerosis already shows fibrotic characteristics. Both tech niques were easy to use and suitable for objectifying dermal fibrosis in sc leroderma lesions. FFT is more accurate and reproducible than the laser sca tter method and allows simultaneous pathological evaluation of the location of the analyzed tissue sections. Future studies will need to focus on the correlation between clinical disease severity and collagen bundle character istics.