Hemicentin mediated type IV collagen assembly strengthens juxtaposed basement membrane linkage

Basement membrane (BM) matrices surround and separate most tissues. However, through poorly understood mechanisms, BMs of adjacent tissues can also stably link to support organ structure and function. Using endogenous knock-in fluorescent proteins, conditional RNAi, optogenetics, and quantitative live imaging, we identified matrix proteins mediating a BM linkage (B-LINK) between the uterine utse and epidermal seam cell BMs in Caenorhabditis elegans that supports the uterus during egg-laying. We found that hemicentin is secreted by the utse and promotes fibulin-1 assembly to jointly initiate the B-LINK. During egg-laying, however, both proteins decline in levels and are not required for B-LINK maintenance. Instead, we discovered that hemicentin also promotes type IV collagen assembly, which accumulates to high levels during egg-laying and sustains the B-LINK during the mechanically active egg-laying period. This work reveals mechanisms underlying BM-BM connection maturation and identifies a crucial function for hemicentin and fibulin-1 in initiating attachment and type IV collagen in strengthening this specialized form of tissue linkage.

Screening of Self-Assembling of Collagen IV Fragments into Stable Structures Potentially Useful in Regenerative Medicine

The aim of the research was to check whether it is possible to use fragments of type IV collagen to obtain, as a result of self-assembling, stable spatial structures that could be used to prepare new materials useful in regenerative medicine. Collagen IV fragments were obtained by using DMT/NMM/TosO− as a coupling reagent. The ability to self-organize and form stable spatial structures was tested by the CD method and microscopic techniques. Biological studies covered: resazurin assay (cytotoxicity assessment) on BJ, BJ-5TA and C2C12 cell lines; an alkaline version of the comet assay (genotoxicity), Biolegend Legendplex human inflammation panel 1 assay (SC cell lines, assessment of the inflammation activity) and MTT test to determine the cytotoxicity of the porous materials based on collagen IV fragments. It was found that out of the pool of 37 fragments (peptides 1–33 and 2.1–2.4) reconstructing the outer sphere of collagen IV, nine fragments (peptides: 2, 4, 5, 6, 14, 15, 25, 26 and 30), as a result of self-assembling, form structures mimicking the structure of the triple helix of native collagens. The stability of spatial structures formed as a result of self-organization at temperatures of 4 °C, 20 °C, and 40 °C was found. The application of the MST method allowed us to determine the Kd of binding of selected fragments of collagen IV to ITGα1β1. The stability of the spatial structures of selected peptides made it possible to obtain porous materials based on their equimolar mixture. The formation of the porous materials was found for cross-linked structures and the material stabilized only by weak interactions. All tested peptides are non-cytotoxic against all tested cell lines. Selected peptides also showed no genotoxicity and no induction of immune system responses. Research on the use of porous materials based on fragments of type IV collagen, able to form stable spatial structures as scaffolds useful in regenerative medicine, will be continued.

A novel noninvasive formula for predicting cirrhosis in patients with chronic hepatitis C

Evaluating liver fibrosis is crucial for disease severity assessment, treatment decisions, and hepatocarcinogenic risk prediction among patients with chronic hepatitis C. In this retrospective multicenter study, we aimed to construct a novel model formula to predict cirrhosis. A total of 749 patients were randomly allocated to training and validation sets at a ratio of 2:1. Liver stiffness measurement (LSM) was made via transient elastography using FibroScan. Patients with LSM ≥12.5 kPa were regarded as having cirrhosis. The best model formula for predicting cirrhosis was constructed based on factors significantly and independently associated with LSM (≥12.5 kPa) using multivariate regression analysis. Among the 749 patients, 198 (26.4%) had LSM ≥12.5 kPa. In the training set, multivariate analysis identified logarithm natural (ln) type IV collagen 7S, ln hyaluronic acid, and ln Wisteria floribunda agglutinin positive Mac-2-binding protein (WFA+-Mac-2 BP) as the factors that were significantly and independently associated with LSM ≥12.5 kPa. Thus, the formula was constructed as follows: score = −6.154 + 1.166 × ln type IV collagen 7S + 0.526 × ln hyaluronic acid + 1.069 × WFA+-Mac-2 BP. The novel formula yielded the highest area under the curve (0.882; optimal cutoff, −0.381), specificity (81.5%), positive predictive values (62.6%), and predictive accuracy (81.6%) for predicting LSM ≥12.5 kPa among fibrosis markers and indices. These results were almost similar to those in the validated set, indicating the reproducibility and validity of the novel formula. The novel formula scores were significantly, strongly, and positively correlated with LSM values in both the training and validation data sets (correlation coefficient, 0.721 and 0.762; p = 2.67 × 10−81 and 1.88 × 10−48, respectively). In conclusion, the novel formula was highly capable of diagnosing cirrhosis in patients with chronic hepatitis C and exhibited better diagnostic performance compared to conventional fibrosis markers and indices.

Atypical Antiglomerular Basement Membrane Disease in a Pediatric Patient Successfully Treated with Rituximab

Classic antiglomerular basement membrane (anti-GBM) disease is an exceedingly rare but extremely aggressive form of glomerulonephritis, typically caused by autoantibodies directed against cryptic, conformational epitopes within the noncollagenous domain of the type IV collagen alpha-3 subunit. Pathologic diagnosis is established by the presence of strong, diffuse, linear staining for immunoglobulin on immunofluorescence microscopy. Recently, patients with atypical clinical and pathologic findings of anti-GBM disease have been described. These patients tend to have an indolent clinical course, without pulmonary involvement, and laboratory testing rarely reveals the presence of anti-GBM antibodies. Specific guidelines for the treatment and management of these patients are unclear. Here, we describe a case of atypical anti-GBM disease in a young child who presented with hematuria and prominent proteinuria. Throughout the course of his illness, creatinine remained normal. He was conservatively treated with steroids and rituximab, resulting in resolution of his clinical symptoms and normalization of laboratory findings.

Alport Syndrome

Alport syndrome (AS) is a type IV collagen hereditary disease characterized by the association of progressive Hematuric nephritis, hearing loss, and, frequently, ocular changes. Mutations in the COL4A5 collagen gene are responsible for the more common X-linked dominant form of the disease.

Kidney organoids: A system to study human basement membrane assembly in health and disease

Basement membranes (BMs) are complex macromolecular networks underlying all continuous layers of cells. Essential components include type IV collagen and laminins, which are affected by human genetic defects leading to a range of debilitating conditions including kidney, muscle, and cerebrovascular phenotypes. We investigated the dynamics of BM assembly in human pluripotent stem cell-derived kidney organoids. We resolved their global BM composition and discovered a conserved temporal sequence in BM assembly that paralleled mammalian fetal kidneys. We identified the emergence of key BM isoforms, which were altered by a pathogenic variant in COL4A5. Integrating organoid, fetal and adult kidney proteomes we found dynamic regulation of BM composition through development to adulthood, and with single-cell transcriptomic analysis we mapped the cellular origins of BM components. Overall, we define the complex and dynamic nature of vertebrate BM assembly and provide a platform for understanding its wider relevance in human development and disease.

IMMUNOGISTOCHEMICAL STUDIES OF THE LUNGS IN FIRE PENETRATION INJURIES

Summary. The aim of the study was to analyze the data of immunohistochemical studies of the lungs after a gunshot wound penetrating at different times. Materials and methods. Lung tissue removed from the wounded with an encapsulated foreign body or without a foreign body of fire origin in the period from 1 day to 10 months after injury was studied. Results and discussion. At 1 day after injury, pathological type IV collagen and transforming growth factor begin to accumulate in the damaged areas. On day 2 of the wound, there is a slight increase in the expression of TGF-β1 and Collagen IV, VEGF is practically not produced, the number of CD68 + macrophages increases. Day 10 was characterized by a progressive increase in the content of transforming growth factor in leukocytes, lymphocytes, fibroblasts, macrophages and collagen type IV in the surrounding wounds. Ten months after injury and surgery, the wound canal was a large area of dense connective tissue with single venous vessels, often without a muscular layer. Transforming growth factor showed pronounced expression in macrophages and vascular endothelium, while VEGF was manifested as a weak positive response in vascular endothelial cells and single macrophages. Type IV collagen remained between the fibers of dense fibrous tissue, which replaced the wound canal, and was also found in the walls of blood vessels, interalveolar membranes, fibroblasts of the adjacent lung parenchyma. Conclusions. 1. Traumatic disorders in the lung parenchyma in FPI in the first hours after injury are accompanied by the accumulation of CD68 + macrophages, which persist for 10 months after FPI and become the main producers of TGF-β1 and VEGF. 2. Transforming growth factor TGF-β1 and vascular-endothelial growth factor VEGF are found in large quantities in macrophages, leukocytes, lymphocytes, fibroblasts and vascular endothelium from the first day of trauma to the lung parenchyma; up to 10 days the expression of TGF-β1 becomes significant, while VEGF weakly marks capillary endotheliocytes, arterioles, single macrophages. This immunohistochemical picture explains the long healing period of FPI. 3. The content of pathological collagen type IV Collagen IV on the first day of gunshot wound is minimal, increases up to 10 days and is detected in the fields of fibrosis and dystelectasis of the lung parenchyma after 10 months. 4. Determination of IHC expression of CD68, TGF-β1, VEGF and Collagen IV in the first 10 days after FPI and in the subsequent stages of treatment of the wounded will help to predict the course of combat trauma and adjust the methods of treatment.