Laser-induced modification of the patellar ligament tissue: comparative study of structural and optical changes

The effects of non-ablative infrared (IR) laser treatment of collagenous tissue have been commonly interpreted in terms of collagen denaturation spread over the laser-heated tissue area. In this work, the existing model is refined to account for the recently reported laser-treated tissue heterogeneity and complex collagen degradation pattern using comprehensive optical imaging and calorimetry toolkits. Patella ligament (PL) provided a simple model of type I collagen tissue containing its full structural content from triple-helix molecules to gross architecture. PL ex vivo was subjected to IR laser treatments (laser spot, 1.6 mm) of equal dose, where the tissue temperature reached the collagen denaturation temperature of 60 ± 2°C at the laser spot epicenterin the first regime, and was limited to 67 ± 2°C in the second regime. The collagen network was analyzed versus distance from the epicenter. Experimental characterization of the collagenous tissue at all structural levels included cross-polarization optical coherence tomography, nonlinear optical microscopy, light microscopy/histology, and differential scanning calorimetry. Regressive rearrangement of the PL collagen network was found to spread well outside the laser spot epicenter (>2 mm) and was accompanied by multilevel hierarchical reorganization of collagen. Four zones of distinct optical and morphological properties were identified, all elliptical in shape, and elongated in the direction perpendicular to the PL long axis. Although the collagen transformation into a random-coil molecular structure was occasionally observed, it was mechanical integrity of the supramolecular structures that was primarily compromised. We found that the structural rearrangement of the collagen network related primarily to the heat-induced thermo-mechanical effects rather than molecular unfolding. The current body of evidence supports the notion that the supramolecular collagen structure suffered degradation of various degrees, which gave rise to the observed zonal character of the laser-treated lesion

FGFR3 mutations in seborrheic keratoses are already present in flat lesions and associated with age and localization

Somatic activating fibroblast growth factor 3 (FGFR3) mutations in human skin can cause seborrheic keratoses, one of the most frequent skin tumors in man. However, details of the involved mechanisms remain elusive. We analyzed 65 acanthotic seborrheic keratoses with varying vertical diameters for FGFR3 mutations using a SNaPshot multiplex assay. Immunohistochemistry was performed for Ki-67, bcl-2 and FGFR3 protein in all seborrheic keratoses and 19 normal skin samples. FGFR3 mutations were detected in 37 of 65 seborrheic keratoses (57%). These mutations were found both in flat (initial) and thick seborrheic keratoses. FGFR3 mutations were significantly associated with increased age and localization on the head and neck (P<0.01). Ki-67 expression was significantly higher in seborrheic keratoses than in normal epidermis independent of the FGFR3 status (P<0.001). Furthermore, FGFR3 mutations were associated with an increased expression of bcl-2 and FGFR3 protein (P<0.05). Our results indicate that FGFR3 mutations can occur early in the pathogenesis of at least a subset of seborrheic keratoses. Increased age appears to be a risk factor for these mutations. The preferential occurrence of FGFR3 mutations in seborrheic keratoses of the head and neck suggests a causative role for cumulative lifetime ultraviolet light exposure