Polarization-sensitive optical coherence tomography and scleral collagen fiber orientation in osteogenesis imperfecta.

Osteogenesis imperfecta (OI), a rare genetic connective tissue disorder, primarily arises from pathogenic variants affecting the production or structure of collagen type I. In addition to skeletal fragility, individuals with OI may face an increased risk of developing ophthalmic diseases. This association is believed to stem from the widespread presence of collagen type I throughout various parts of the eye. However, the precise consequences of abnormal collagen type I on different ocular tissues remain unknown. Of particular significance is the sclera, where collagen type I is abundant and crucial for maintaining the structural integrity of the eye. Recent research on healthy individuals has uncovered a unique organizational pattern of collagen fibers within the sclera, characterized by fiber arrangement in both circular and radial layers around the optic nerve head. While the precise function of this organizational pattern remains unclear, it is hypothesized to play a role in providing mechanical support to the optic nerve. The objective of this study is to investigate the impact of abnormal collagen type I on the sclera by assessing the fiber organization near the optic nerve head in individuals with OI and comparing them to healthy individuals. Collagen fiber orientation of the sclera was measured using polarization-sensitive optical coherence tomography (PS-OCT), an extension of the conventional OCT that is sensitive to materials that exhibit birefringence (axial changes in light refraction). Birefringence was quantified and used as imaging contrast to extract collagen fiber orientation as well as the thickness of the radially oriented scleral layer. Three individuals with OI, exhibiting different degrees of disease severity, were assessed and analyzed, along with seventeen healthy individuals. Mean values obtained from individuals with OI were descriptively compared to those of the healthy participant group. PS-OCT revealed a similar orientation pattern of scleral collagen fibers around the optic nerve head between OI individuals and healthy individuals. However, two OI participants exhibited reduced mean birefringence of the radially oriented scleral layer compared to the healthy participant group (OI participant 1 oculus dexter et sinister (ODS): 0.34°/µm, OI participant 2: ODS 0.26°/µm, OI participant 3: OD: 0.29°/µm, OS: 0.28°/µm, healthy participants: ODS 0.38 ± 0.05°/µm). The radially oriented scleral layer was thinner in all OI participants although within ±2 standard deviations of the mean observed in healthy individuals (OI participant 1 OD: 101 µm, OS 104 µm, OI participant 2: OD 97 µm, OS 98 µm, OI participant 3: OD: 94 µm, OS 120 µm, healthy participants: OD 122.8 ± 13.6 µm, OS 120.8 ± 15.1 µm). These findings imply abnormalities in collagen organization or composition, underscoring the necessity for additional research to comprehend the ocular phenotype in OI.

Uniaxial mechanical stretch properties correlated with three-dimensional microstructure of human dermal skin.

The intact and healthy skin forms a barrier to the outside world and protects the body from mechanical impact. The skin is a complex structure with unique mechano-elastic properties. To better direct the design of biomimetic materials and induce skin regeneration in wounds with optimal outcome, more insight is required in how the mechano-elastic properties emerge from the skin's main constituents, collagen and elastin fibers. Here, we employed two-photon excited autofluorescence and second harmonic generation microscopy to characterize collagen and elastin fibers in 3D in 24 human dermis skin samples. Through uniaxial stretching experiments, we derive uni-directional mechanical properties from resultant stress-strain curves, including the initial Young's modulus, elastic Young's modulus, maximal stress, and maximal and mid-strain values. The stress-strain curves show a large variation, with an average Young's modules in the toe and linear regions of 0.1 MPa and 21 MPa. We performed a comprehensive analysis of the correlation between the key mechanical properties with age and with microstructural parameters, e.g., fiber density, thickness, and orientation. Age was found to correlate negatively with Young's modulus and collagen density. Moreover, real-time monitoring during uniaxial stretching allowed us to observe changes in collagen and elastin alignment. Elastin fibers aligned significantly in both the heel and linear regions, and the collagen bundles engaged and oriented mainly in the linear region. This research advances our understanding of skin biomechanics and yields input for future first principles full modeling of skin tissue.

Aortic Stenosis and the Evolution of Cardiac Damage after Transcatheter Aortic Valve Replacement.

Background/Objectives: Severe aortic stenosis (AS) is the most frequent valvular heart disease. Models for stratifying cardiac damage associated with aortic stenosis have been developed to predict outcomes following valve replacement. However, evidence regarding morphological and functional evolution, as well as potential changes in the degree of cardiac damage, is limited. We aim to provide information on the evolution of cardiac morphology and the function of patients undergoing transcatheter aortic valve replacement (TAVR) who have been classified using a cardiac damage staging system. Methods: In total, 496 patients were included in the analysis, and were classified into four stages based on the extent of cardiac damage as follows: Stage 0, no cardiac damage: left ventricle global longitudinal strain (LV-GLS) < -17%; right ventricular-arterial coupling (RVAc) ≥ 0.35), and absence of significant mitral regurgitation (MR). Stage 1, left-sided subclinical damage: LV-GLS ≥ -17%. Stage 2, left-sided damage: significant MR. Stage 3, right-sided damage: RVAc < 0.35. Results: The mean age was 82.1 ± 5.9 years, and 53.0% were female. In total, 24.5% of patients met the criteria for Stage 0, and Stage 1 included 42.8% of patients, Stage 2 included 16.5%, and Stage 3 comprised 16.2% of patients. Mortality was 8.4% for stage 0, 17.4% for stage 1, 25.6% for stage 2, and 28.6% for stage 3 patients (p = 0.004). Diabetes mellitus (DM) (p = 0.047) and chronic kidney disease (CKD) (p = 0.024) were the only clinical predictors of no change or worsening in the stage of cardiac damage. Regarding echocardiographic variables, concomitant tricuspid, and mitral regurgitation, ≥ 2 were both significantly associated with no change or worsening, also (p < 0.001). Conclusions: Cardiac damage that is secondary to severe aortic stenosis has morphological and functional repercussions that, even after valve replacement, persist and might worsen the prognosis.

Reporte de un caso: Fractura expuesta del mediopie por accidente de tránsito en paciente VIH/SIDA / Case Report: Exposed Midfoot Fracture Due To Traffic Accident In HIV/AIDS Patient

Actualmente hay una alta incidencia de accidentes de tránsito en el mundo, muchos de ellos provocan una discapacidad grave en las personas. Estas lesiones en las extremidades provocan alta morbilidad llegando incluso a una amputación. Esto se agrava en pacientes VIH/SIDA, sobre todo en el tratamiento y la evolución. Se presenta un caso clínico de un paciente con lesión severa del mediopie que termina en amputación y se hace una revisión del manejo quirúrgico del paciente traumatológico con VIH/SIDA

Currently there is a high incidence of traffic accidents in the world, many of them cause severe disability in people. These limb injuries cause high morbidity even reaching an amputation. This is aggravated in HIV/AIDS patients, especially in treatment and evolution. A clinical case of a patient with severe midfoot injury that ends in amputation is presented and a surgical management review of the trauma patient with HIV/AIDS is made.