Investigation of dermal collagen nanostructures in Ehlers-Danlos Syndrome (EDS) patients.

Ehlers-Danlos syndromes (EDS) represent a group of rare genetic disorders affecting connective tissues. Globally, approximately 1.5 million individuals suffer from EDS, with 10,000 reported cases in Canada alone. Understanding the histological properties of collagen in EDS has been challenging, but advanced techniques like atomic force microscopy (AFM) have opened up new possibilities for label-free skin imaging. This approach, which explores Type I collagen fibrils at the nanoscale, could potentially enhance EDS diagnosis and our knowledge of collagen type I-related connective tissue disorders. In the current study, we have employed AFM to examine ex-vivo skin biopsies from four individuals: one with classical EDS (cEDS), one with hypermobile EDS (hEDS), one with hEDS and Scleroderma (hEDS-Scleroderma), and one healthy control. Picrosirius red (PS) staining was used to highlight collagen differences in the samples. For each case, 14 images and 1400 force curves were obtained, with seven images and 700 force curves representing healthy collagen (PS-induced red staining) and the rest showcasing disrupted collagen (yellow staining). The results showed that PS staining was uniform throughout the control section, while cEDS and hEDS displayed localized areas of yellow staining. In the case of hEDS-Scleroderma, the yellow staining was widespread throughout the section. AFM images revealed irregular collagen fibrils in the disrupted, yellow-stained areas, contrasting with aligned and well-registered collagen fibrils in healthy, red-stained regions. Additionally, the study assessed the ability of non-AFM specialists to differentiate between healthy and disrupted collagen in AFM images, yielding substantial agreement among raters according to Fleiss's and Cohen's kappa scores (0.96 and 0.79±0.1, respectively). Biomechanical analysis revealed that normal healthy collagen exhibited a predominant population at 2.5 GPa. In contrast, EDS-affected collagen displayed subpopulations with lower compressive elastic modulus, indicating weaker collagen fibrils in EDS patients. Although these findings pertain to a limited number of cases, they offer valuable insights into the nanoscale collagen structure and biomechanics in individuals with EDS. Over time, these insights could be developed into specific biomarkers for the condition, improving diagnosis and treatment for EDS and related connective tissue disorders.

Validation of clinically related aging models based on enamel wear.

PURPOSE: Physiological and erosive wear reported in clinical studies were reviewed, and in vitro aging models were developed to simulate and compare the effect of aging on human teeth with the review data obtained from clinical studies. METHODS: A review of clinical studies and randomized clinical trials that quantify enamel wear was performed in the PubMed database. The first in vitro analysis evaluated the effect of mechanical chewing simulation only. Enamel specimens were aged in the chewing simulator (up to 1.2 million cycles) with two occlusal loads (30 and 50 N). In the second in vitro analysis, specimens were aged in two aging models. The first model (MT) simulated mechanical and thermal oral challenges: MT1- 240,000 chewing and 10,000 thermal cycles, MT2- 480,000 chewing and 20,000 thermal cycles, MT3- 1.2 million chewing and 50,000 thermal cycles. The second model (MTA) simulated mechanical, thermal, and acidic oral challenges as follows: MTA1- 240,000 chewing, 10,000 thermal and 3-h acidic cycles; MTA2: 480,000 chewing, 20,000 thermal and 6-h acidic cycles, MTA3- 1.2 million chewing, 50,000 thermal and 15-h acidic cycles. RESULTS: The review included 13 clinical studies evaluating tooth wear (eight physiological and five erosive). The results estimated the annual average physiological wear as 38.4 µm (9.37-51). In comparison, the MT1 showed wear of 60 (24) µm. Also, the average annual erosive wear in the literature was 179.5 µm (70-265) compared to MTA1-induced wear of 209 (14) µm. CONCLUSION: There was wide variation in tooth wear reported in clinical studies, suggesting a critical need for more accurate studies, possibly based on scanning technologies. Despite this, the data reported using the novel aging models are within a range to be considered consistent with and to simulate tooth wear measured in vivo.