Type IV collagen: structure, gene organization, and role in human diseases. Molecular basis of Goodpasture and Alport syndromes and diffuse leiomyomatosis

Diabetes and Renal Complications: An Overview on Pathophysiology, Biomarkers and Therapeutic Interventions

Diabetic kidney disease (DKD) is a major microvascular complication of both type 1 and type 2 diabetes. DKD is characterised by injury to both glomerular and tubular compartments, leading to kidney dysfunction over time. It is one of the most common causes of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Persistent high blood glucose levels can damage the small blood vessels in the kidneys, impairing their ability to filter waste and fluids from the blood effectively. Other factors like high blood pressure (hypertension), genetics, and lifestyle habits can also contribute to the development and progression of DKD. The key features of renal complications of diabetes include morphological and functional alterations to renal glomeruli and tubules leading to mesangial expansion, glomerulosclerosis, homogenous thickening of the glomerular basement membrane (GBM), albuminuria, tubulointerstitial fibrosis and progressive decline in renal function. In advanced stages, DKD may require treatments such as dialysis or kidney transplant to sustain life. Therefore, early detection and proactive management of diabetes and its complications are crucial in preventing DKD and preserving kidney function.

Collagen IV assembly is influenced by fluid flow in kidney cell-derived matrices

Kidney podocytes and endothelial cells assemble a complex and dynamic basement membrane that is essential for kidney filtration. Whilst many components of this specialised matrix are known, the influence of fluid flow on its assembly and organisation remains poorly understood. Using the coculture of podocytes and glomerular endothelial cells in a low-shear stress, high-flow bioreactor, we investigated the effect of laminar fluid flow on the composition and assembly of cell-derived matrix. With immunofluorescence and matrix image analysis we found flow-mediated remodelling of collagen IV. Using proteomic analysis of the cell-derived matrix we identified changes in both abundance and composition of matrix proteins under flow, including the collagen-modifying enzyme, prolyl 4-hydroxylase (P4HA1). To track collagen IV assembly, we used CRISPR-Cas9 to knock in the luminescent marker HiBiT to the endogenous COL4A2 gene in podocytes. With this system, we found that collagen IV was secreted and accumulated consistently under both static and flow conditions. However knockdown of P4HA1 in podocytes led to a reduction in the secretion of collagen IV and this was more pronounced under flow. Together, this work demonstrates the effect of fluid flow on the composition, modification, and organisation of kidney cell-derived matrix and provides an in vitro system for investigating flow-induced matrix alteration in the context of kidney development and disease.

Understanding interleukin 11 as a disease gene and therapeutic target

Interleukin 11 (IL11) is an elusive member of the IL6 family of cytokines. While initially thought to be a haematopoietic and cytoprotective factor, more recent data show instead that IL11 is redundant for haematopoiesis and toxic. In this review, the reasons that led to the original misunderstandings of IL11 biology, which are now understandable, are explained with particular attention on the use of recombinant human IL11 in mice and humans. Following tissue injury, as part of an evolutionary ancient homeostatic response, IL11 is secreted from damaged mammalian cells to signal via JAK/STAT3, ERK/P90RSK, LKB1/mTOR and GSK3β/SNAI1 in autocrine and paracrine. This activates a program of mesenchymal transition of epithelial, stromal, and endothelial cells to cause inflammation, fibrosis, and stalled endogenous tissue repair, leading to organ failure. The role of IL11 signalling in cell- and organ-specific pathobiology is described, the large unknowns about IL11 biology are discussed and the promise of targeting IL11 signalling as a therapeutic approach is reviewed.

Collagen IV of basement membranes: II. Emergence of collagen IVα345 enabled the assembly of a compact GBM as an ultrafilter in mammalian kidneys

The collagen IVα345 (Col-IVα345) scaffold, the major constituent of the glomerular basement membrane (GBM), is a critical component of the kidney glomerular filtration barrier. In Alport syndrome, affecting millions of people worldwide, over two thousand genetic variants occur in the COL4A3, COL4A4, and COL4A5 genes that encode the Col-IVα345 scaffold. Variants cause loss of scaffold, a suprastructure that tethers macromolecules, from the GBM or assembly of a defective scaffold, causing hematuria in nearly all cases, proteinuria, and often progressive kidney failure. How these variants cause proteinuria remains an enigma. In a companion paper, we found that the evolutionary emergence of the COL4A3, COL4A4, COL4A5, and COL4A6 genes coincided with kidney emergence in hagfish and shark and that the COL4A3 and COL4A4 were lost in amphibians. These findings opened an experimental window to gain insights into functionality of the Col-IVα345 scaffold. Here, using tissue staining, biochemical analysis and TEM, we characterized the scaffold chain arrangements and the morphology of the GBM of hagfish, shark, frog, and salamander. We found that α4 and α5 chains in shark GBM and α1 and α5 chains in amphibian GBM are spatially separated. Scaffolds are distinct from one another and from the mammalian Col-IVα345 scaffold, and the GBM morphologies are distinct. Our findings revealed that the evolutionary emergence of the Col-IVα345 scaffold enabled the genesis of a compact GBM that functions as an ultrafilter. Findings shed light on the conundrum, defined decades ago, whether the GBM or slit diaphragm is the primary filter.

In vitro microvascular engineering approaches and strategies for interstitial tissue integration

The increasing gap between clinical demand for tissue or organ transplants and the availability of donated tissue highlights the emerging opportunities for lab-grown or synthetically engineered tissue. While the field of tissue engineering has existed for nearly half a century, its clinical translation remains unrealised, in part, due to a limited ability to engineer sufficient vascular supply into fabricated tissue, which is necessary to enable nutrient and waste exchange, prevent cellular necrosis, and support tissue proliferation. Techniques to develop anatomically relevant, functional vascular networks in vitro have made significant progress in the last decade, however, the challenge now remains as to how best incorporate these throughout dense parenchymal tissue-like structures to address diffusion-limited development and allow for the fabrication of large-scale vascularised tissue. This review explores advances made in the laboratory engineering of vasculature structures and summarises recent attempts to integrate vascular networks together with sophisticated in vitro avascular tissue and organ-like structures. STATEMENT OF SIGNIFICANCE: The ability to grow full scale, functional tissue and organs in vitro is primarily limited by an inability to adequately diffuse oxygen and nutrients throughout developing cellularised structures, which generally results from the absence of perfusable vessel networks. Techniques to engineering both perfusable vascular networks and avascular miniaturised organ-like structures have recently increased in complexity, sophistication, and physiological relevance. However, integrating these two essential elements into a single functioning vascularised tissue structure represents a significant spatial and temporal engineering challenge which is yet to be surmounted. Here, we explore a range of vessel morphogenic phenomena essential for tissue-vascular co-development, as well as evaluate a range of recent noteworthy approaches for generating vascularised tissue products in vitro.

A recombinant technique for mapping functional sites of heterotrimeric collagen helices: Collagen IV CB3 fragment as a prototype for integrin binding

Collagen superfamily of proteins is a major component of the extracellular matrix. Defects in collagens underlie the cause of nearly 40 human genetic diseases in millions of people worldwide. Pathogenesis typically involves genetic alterations of the triple helix, a hallmark structural feature that bestows exceptional mechanical resistance to tensile forces and a capacity to bind a plethora of macromolecules. Yet, there is a paramount knowledge gap in understanding the functionality of distinct sites along the triple helix. Here, we present a recombinant technique to produce triple helical fragments for functional studies. The experimental strategy utilizes the unique capacity of the NC2 heterotrimerization domain of collagen IX to drive three α-chain selection and registering the triple helix stagger. For proof of principle, we produced and characterized long triple helical fragments of collagen IV that were expressed in a mammalian system. The heterotrimeric fragments encompassed the CB3 trimeric peptide of collagen IV, which harbors the binding motifs for α1β1 and α2β1 integrins. Fragments were characterized and shown to have a stable triple helix, post-translational modifications, and high affinity and specific binding of integrins. The NC2 technique is a universal tool for the high-yield production of heterotrimeric fragments of collagens. Fragments are suitable for mapping functional sites, determining coding sequences of binding sites, elucidating pathogenicity and pathogenic mechanisms of genetic mutations, and production of fragments for protein replacement therapy.

Identification of unique α4 chain structure and conserved antiangiogenic activity of α3NC1 type IV collagen in zebrafish

BACKGROUND

Type IV collagen is an abundant component of basement membranes in all multicellular species and is essential for the extracellular scaffold supporting tissue architecture and function. Lower organisms typically have two type IV collagen genes, encoding α1 and α2 chains, in contrast with the six genes in humans, encoding α1-α6 chains. The α chains assemble into trimeric protomers, the building blocks of the type IV collagen network. The detailed evolutionary conservation of type IV collagen network remains to be studied.

RESULTS

We report on the molecular evolution of type IV collagen genes. The zebrafish α4 non-collagenous (NC1) domain, in contrast with its human ortholog, contains an additional cysteine residue and lacks the M93 and K211 residues involved in sulfilimine bond formation between adjacent protomers. This may alter α4 chain interactions with other α chains, as supported by temporal and anatomic expression patterns of collagen IV chains during the zebrafish development. Despite the divergence between zebrafish and human α3 NC1 domain (endogenous angiogenesis inhibitor, Tumstatin), the zebrafish α3 NC1 domain exhibits conserved antiangiogenic activity in human endothelial cells.

CONCLUSIONS

Our work supports type IV collagen is largely conserved between zebrafish and humans, with a possible difference involving the α4 chain.

Electroretinographic abnormalities in Alport syndrome with a novel COL4A5 truncated variant (p.Try20GlyfsTer19)

PURPOSE

Alport syndrome comprises a heterogeneous group of inherited kidney diseases that are associated with ocular complications. In this study, we aimed to detail the clinical characteristics of a patient with X-linked Alport syndrome.

METHODS

We performed next-generation sequencing (NGS) with hybridization capture to identify the disease-causing variant of Alport syndrome and a comprehensive ophthalmic examination, including full-field electroretinography (FF-ERG).

RESULTS

Genetic testing using NGS with hybridization capture revealed a novel hemizygous variant [c.51_52delGA (p.Trp20GlyfsTer19)] in exon 1 of COL4A5. The patient underwent cataract surgery in both eyes because of decreased visual acuity and photophobia. The best-corrected visual acuity improved from 0.9 and 0.7 in the right and left eyes, respectively, to 1.5 in both eyes. Anterior-segment optical coherence tomography (OCT) revealed anterior and posterior lenticonus. Fundus photographs showed central and peripheral fleck retinopathy. Wide-field fundus autofluorescence (AF) imaging showed mottled hyper- and hypo-AF in the peripheral retina, which was consistent with peripheral fleck retinopathy. Furthermore, OCT revealed thinning of the inner retinal layers, especially at the temporal macular, but the outer retinal layers were preserved. Ganglion cell analysis showed no progression for 5 years. FF-ERG was performed at 41 (phakia) and 46 (pseudophakia) years of age. The amplitudes of dark-adapted (DA) and light-adapted (LA) responses showed selective b-wave abnormalities. The b/a-wave ratios of DA 3.0 were 1.22 and 1.16 in the right and left eyes, respectively. The amplitudes of DA 3.0 oscillatory potentials (OP) were reduced. Five years later, the amplitudes of DA and LA responses revealed no remarkable changes, except for an OP wave of DA 3.0, which was substantially reduced.

CONCLUSIONS

Our findings revealed electroretinographic abnormalities in a patient with Alport syndrome, which predominantly indicated impairment of the inner retina. Notably, little short-term progression was observed.

Digenic Alport Syndrome

Digenic Alport syndrome refers to the inheritance of pathogenic variants in COL4A5 plus COL4A3 or COL4A4 or in COL4A3 plus COL4A4 Where digenic Alport syndrome includes a pathogenic COL4A5 variant, the consequences depend on the sex of the affected individual, COL4A5 variant "severity," and the nature of the COL4A3 or COL4A4 change. A man with a pathogenic COL4A5 variant has all his collagen IV α3α4α5-heterotrimers affected, and an additional COL4A3 or COL4A4 variant may not worsen disease. A woman with a pathogenic COL4A5 variant has on average 50% of her heterotrimers affected, which is increased to 75% with a further COL4A3 or COL4A4 variant and associated with a higher risk of proteinuria. In digenic Alport syndrome with pathogenic COL4A3 and COL4A4 variants, 75% of the heterotrimers are affected. The COL4A3 and COL4A4 genes occur head-to-head on chromosome 2, and inheritance is autosomal dominant when both variants affect the same chromosome (in cis) or recessive when they affect different chromosomes (in trans). This form of digenic disease results in increased proteinuria and a median age of kidney failure intermediate between autosomal dominant and autosomal recessive Alport syndrome. Previous guidelines have suggested that all pathogenic or likely pathogenic digenic variants should be identified and reported. Affected family members should be identified, treated, and discouraged from kidney donation. Inheritance within a family is easier to predict if the two variants are considered independently and if COL4A3 and COL4A4 variants are known to be inherited on the same or different chromosomes.

Prospective collagen IVα345 therapies for Alport syndrome

PURPOSE OF REVIEW

In Alport syndrome, over 1,700 genetic variants in the COL4A3, COL4A4, and COL4A5 genes cause the absence or malfunctioning of the collagen IVα345 scaffold - an essential component of the glomerular basement membrane (GBM). Therapies are limited to treatment with Angiotensin-Converting enzyme (ACE) inhibitors to slow progression of the disease. Here, we review recent progress in therapy development to replace the scaffold or restore its function.

RECENT FINDINGS

Multiple approaches emerged recently for development of therapies that target different stages of production and assembly of the collagen IVα345 scaffold in the GBM. These approaches are based on (1) recent advances in technologies allowing to decipher pathogenic mechanisms that underlie scaffold assembly and dysfunction, (2) development of DNA editing tools for gene therapy, (3) RNA splicing interference, and (4) control of mRNA translation.

SUMMARY

There is a growing confidence that these approaches will ultimately provide cure for Alport patients. The development of therapy will be accelerated by studies that provide a deeper understanding of mechanisms that underlie folding, assembly, and function of the collagen IVα345 scaffold.

Defective perlecan-associated basement membrane regeneration and altered modulation of transforming growth factor beta in corneal fibrosis

In the cornea, the epithelial basement membrane (EBM) and corneal endothelial Descemet's basement membrane (DBM) critically regulate the localization, availability and, therefore, the functions of transforming growth factor (TGF)β1, TGFβ2, and platelet-derived growth factors (PDGF) that modulate myofibroblast development. Defective regeneration of the EBM, and notably diminished perlecan incorporation, occurs via several mechanisms and results in excessive and prolonged penetration of pro-fibrotic growth factors into the stroma. These growth factors drive mature myofibroblast development from both corneal fibroblasts and bone marrow-derived fibrocytes, and then the persistence of these myofibroblasts and the disordered collagens and other matrix materials they produce to generate stromal scarring fibrosis. Corneal stromal fibrosis often resolves completely if the inciting factor is removed and the BM regenerates. Similar defects in BM regeneration are likely associated with the development of fibrosis in other organs where perlecan has a critical role in the modulation of signaling by TGFβ1 and TGFβ2. Other BM components, such as collagen type IV and collagen type XIII, are also critical regulators of TGF beta (and other growth factors) in the cornea and other organs. After injury, BM components are dynamically secreted and assembled through the cooperation of neighboring cells-for example, the epithelial cells and keratocytes for the corneal EBM and corneal endothelial cells and keratocytes for the corneal DBM. One of the most critical functions of these reassembled BMs in all organs is to modulate the pro-fibrotic effects of TGFβs, PDGFs and other growth factors between tissues that comprise the organ.

A Neutralizing IL-11 Antibody Improves Renal Function and Increases Lifespan in a Mouse Model of Alport Syndrome

BACKGROUND

Alport syndrome is a genetic disorder characterized by a defective glomerular basement membrane, tubulointerstitial fibrosis, inflammation, and progressive renal failure. IL-11 was recently implicated in fibrotic kidney disease but its role in Alport syndrome is unknown Methods: We determined IL-11 expression by molecular analyses and in an Alport syndrome mouse model. We assessed the effects of a neutralizing IL-11 antibody (X203) versus an IgG control in Col4a3-/- mice (lacking the gene encoding a type IV collagen component) on renal tubule damage, function, fibrosis, and inflammation. Effects on lifespan of X203, the IgG control, an angiotensin-converting enzyme inhibitor (ramipril), or ramipril+X203 were also studied.

RESULTS

In Col4a3 mice, as kidney failure advanced, renal IL-11 levels increased and IL-11 expression localized to tubular epithelial cells. The IL-11 receptor IL11RA is expressed in tubular epithelial cells and podocytes and is upregulated in tubular epithelial cells of Col4a3 mice. Administration of X203 reduced albuminuria, improved renal function, and preserved podocyte numbers and levels of key podocyte proteins that are reduced in Col4a3 mice; these effects were accompanied by reduced fibrosis and inflammation, attenuation of epithelial-tomesenchymal transition, and increased expression of regenerative markers. X203 attenuated pathogenic ERK and STAT3 pathways, which were activated in Col4a3 mice. Median lifespan of Col4a3 mice was prolonged 22% by ramapril, 44% with X203, and 99% with amipril+X203.

CONCLUSIONS

In an Alport syndrome mouse model, renal IL-11 is upregulated, and neutralization of IL-11 reduces epithelial-to-mesenchymal transition, fibrosis, and inflammation, while improving renal function. Anti-IL-11 combined with ACE inhibition synergistically extends lifespan. This suggests that a therapeutic approach targeting IL-11 holds promise for progressive kidney disease in Alport syndrome.

Expression of collagen type IV in human kidney during prenatal development

Background/Aim. Type IV collagen belongs to the group of nonfibrillar collagens and is an important component of the basement membranes, where it accounts for approximately 50% of its structural elements. The aim of the study was to describe the expression and distribution of collagen type IV in the embryonic and fetal metanephric kidney and to determine the volume density of collagen type IV in kidney tissue in each trimester of development. Methods. The material consisted of 19 human embryos/fetuses, in the gestational age from 8th to 37th week. Kidney tissue specimens were routinely processed to paraffin molds, stained immunohistochemically using polyclonal anti-collagen IV antibody and counterstained with Mayer hematoxylin and eosin. Stained slides were examined using a light microscope, and images of the selected areas under different lens magnification were captured with a digital camera. Volume density of collagen type IV was determined using ImageJ 1.48v and a plugin of the software, which inserted a grid system with 336 points. For the data comparison, the One-Way Analysis of Variance (ANOVA) was used. Results. Strong collagen IV immunopositivity was seen in all specimens, with a distribution in the basement membranes of urinary bud, parietal leaf of Bowman?s capsule, glomerular basement membrane, basement membrane of interstitial blood vessels, and basement membranes of nephron tubules and collecting ducts. No statistically significant difference in the volume density of type IV collagen was found among the different trimesters of the embryonic and fetal development. Conclusion. The synthesis and secretion of collagen type IV simultaneously follow the development of nephron structures, collecting system and blood vessels. The volume density of collagen type IV remains constant throughout all the trimesters of metanephric kidney development, indicating that it plays a crucial role in the normal development of nephron and collecting system structures, as well as in maintaining the normal kidney function.

Emerging Technologies to Study the Glomerular Filtration Barrier

Kidney disease is characterized by loss of glomerular function with clinical manifestation of proteinuria. Identifying the cellular and molecular changes that lead to loss of protein in the urine is challenging due to the complexity of the filtration barrier, constituted by podocytes, glomerular endothelial cells, and glomerular basement membrane. In this review, we will discuss how technologies like single cell RNA sequencing and bioinformatics-based spatial transcriptomics, as well as in vitro systems like kidney organoids and the glomerulus-on-a-chip, have contributed to our understanding of glomerular pathophysiology. Knowledge gained from these studies will contribute toward the development of personalized therapeutic approaches for patients affected by proteinuric diseases.

Basal lamina changes in neurodegenerative disorders

BACKGROUND

Neurodegenerative disorders are a group of age-associated diseases characterized by progressive degeneration of the structure and function of the CNS. Two key pathological features of these disorders are blood-brain barrier (BBB) breakdown and protein aggregation.

MAIN BODY

The BBB is composed of various cell types and a non-cellular component---the basal lamina (BL). Although how different cells affect the BBB is well studied, the roles of the BL in BBB maintenance and function remain largely unknown. In addition, located in the perivascular space, the BL is also speculated to regulate protein clearance via the meningeal lymphatic/glymphatic system. Recent studies from our laboratory and others have shown that the BL actively regulates BBB integrity and meningeal lymphatic/glymphatic function in both physiological and pathological conditions, suggesting that it may play an important role in the pathogenesis and/or progression of neurodegenerative disorders. In this review, we focus on changes of the BL and its major components during aging and in neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). First, we introduce the vascular and lymphatic systems in the CNS. Next, we discuss the BL and its major components under homeostatic conditions, and summarize their changes during aging and in AD, PD, and ALS in both rodents and humans. The functional significance of these alterations and potential therapeutic targets are also reviewed. Finally, key challenges in the field and future directions are discussed.

CONCLUSIONS

Understanding BL changes and the functional significance of these changes in neurodegenerative disorders will fill the gap of knowledge in the field. Our goal is to provide a clear and concise review of the complex relationship between the BL and neurodegenerative disorders to stimulate new hypotheses and further research in this field.

Application of Collagen I and IV in Bioengineering Transparent Ocular Tissues

Collagens represent a major group of structural proteins expressed in different tissues and display distinct and variable properties. Whilst collagens are non-transparent in the skin, they confer transparency in the cornea and crystalline lens of the eye. There are 28 types of collagen that all share a common triple helix structure yet differ in the composition of their α-chains leading to their different properties. The different organization of collagen fibers also contributes to the variable tissue morphology. The important ability of collagen to form different tissues has led to the exploration and application of collagen as a biomaterial. Collagen type I (Col-I) and collagen type IV (Col-IV) are the two primary collagens found in corneal and lens tissues. Both collagens provide structure and transparency, essential for a clear vision. This review explores the application of these two collagen types as novel biomaterials in bioengineering unique tissue that could be used to treat a variety of ocular diseases leading to blindness.

Collagens in primary frozen shoulder: expression of collagen mRNA isoforms in the different phases of the disease

OBJECTIVES

Primary frozen shoulder (pFS) has three phases that differ in clinical presentation. It is characterized by contracture of the joint capsule. We hypothesized that there is a general upregulation of collagens in pFS, and that this is highest in the first phase of the disease. The aims of this study were to investigate the expression of various collagens and degradation of collagens in patients with primary pFS and relate this to the three phases of the condition.

METHODS

From twenty-six patients with pFS and eight control patients with subacromial impingement, biopsies were obtained during shoulder arthroscopy from the middle glenohumeral ligament and the anterior capsule, and mRNA levels for collagens, MMP-2 and -14 and TGF-β1, - β2 and -β3 in the tissue were analysed using real-time PCR.

RESULTS

Genes for collagens type I, III, IV, V, VI and XIV, were activated in pFS, and the total mRNA for all collagens was increased (P < 0.05). This upregulation was independent of disease phases in pFS. In addition, MMP-2, MMP-14, TGF-β1 and TGF-β3 were upregulated in all phases of the disease.

CONCLUSION

There is a general upregulation and an increased degradation of collagens in pFS in all three phases of the disease. This indicates a constantly increased turnover of the fibrotic tissue in the capsule from pFS. The difference in clinical presentation of pFS observed in the three phases of the disease is not primarily a result of variations in collagen production.

Association of Collagen Gene (COL4A3) rs55703767 Variant With Response to Riboflavin/Ultraviolet A-Induced Collagen Cross-Linking in Female Patients With Keratoconus

PURPOSE

To investigate for the first time the association of collagen COL4A3 (rs55703767), COL5A1 (rs7044529), and COL4A4 (rs2229813) variants with response to corneal collagen cross-linking (CXL) with riboflavin and ultraviolet A in patients with keratoconus (KC).

METHODS

A total of 147 eligible patients with KC were genotyped for the specified collagen variants using real-time TaqMan-based polymerase chain reaction. Adjusted odds ratio (OR) with 95% confidence interval (CI) was applied to assess the strength of the association with response to CXL for a decrease in maximum keratometry and/or an increase in corneal thickness.

RESULTS

Eighty-two patients (55.8%) had post-CXL successful outcomes. The overall analysis revealed that minor allele frequencies of COL4A3, COL5A1, and COL4A4 variants were 0.22, 0.22, and 0.38, respectively. The G/T genotype of the COL4A3 variant was more prevalent in the successful group (43%) compared with the failure group (23%) (P < 0.001). COL4A3 (rs55703767) was associated with a good response under heterozygote (OR: 2.19, 95% CI, 1.04-4.59, P < 0.001) and overdominant (OR: 2.59, 95% CI, 1.25-5.38, P = 0.008) models. By contrast, COL5A1 and COL4A4 variants were not associated with the effective response after CXL treatment. Interestingly, stratification analysis by sex revealed that CXL was more successful in female patients with KC under heterozygote (OR: 4.71, 95% CI, 1.74-12.75), dominant (OR: 3.16, 95% CI, 1.29-7.78), and overdominant (OR: 5.18, 95% CI, 1.92-13.95) models for COL4A3 (rs55703767) variant.

CONCLUSIONS

The COL4A3 (rs55703767) variant, among other study variants, could be implicated in CXL riboflavin/ultraviolet A treatment response in patients with KC in the study population. Large-scale replication and follow-up studies in different ethnic groups are warranted.

Consensus statement on standards and guidelines for the molecular diagnostics of Alport syndrome: refining the ACMG criteria

The recent Chandos House meeting of the Alport Variant Collaborative extended the indications for screening for pathogenic variants in the COL4A5, COL4A3 and COL4A4 genes beyond the classical Alport phenotype (haematuria, renal failure; family history of haematuria or renal failure) to include persistent proteinuria, steroid-resistant nephrotic syndrome, focal and segmental glomerulosclerosis (FSGS), familial IgA glomerulonephritis and end-stage kidney failure without an obvious cause. The meeting refined the ACMG criteria for variant assessment for the Alport genes (COL4A3-5). It identified 'mutational hotspots' (PM1) in the collagen IV α5, α3 and α4 chains including position 1 Glycine residues in the Gly-X-Y repeats in the intermediate collagenous domains; and Cysteine residues in the carboxy non-collagenous domain (PP3). It considered that 'well-established' functional assays (PS3, BS3) were still mainly research tools but sequencing and minigene assays were commonly used to confirm splicing variants. It was not possible to define the Minor Allele Frequency (MAF) threshold above which variants were considered Benign (BA1, BS1), because of the different modes of inheritances of Alport syndrome, and the occurrence of hypomorphic variants (often Glycine adjacent to a non-collagenous interruption) and local founder effects. Heterozygous COL4A3 and COL4A4 variants were common 'incidental' findings also present in normal reference databases. The recognition and interpretation of hypomorphic variants in the COL4A3-COL4A5 genes remains a challenge.

Basement Membrane Extracellular Matrix Proteins in Pulmonary Vascular and Right Ventricular Remodeling in Pulmonary Hypertension

The extracellular matrix (ECM), a highly organized network of structural and non-structural proteins, plays a pivotal role in cellular and tissue homeostasis. Changes in the ECM are critical for normal tissue repair, while dysregulation contributes to aberrant tissue remodeling. Pulmonary arterial hypertension (PAH) is a severe disorder of the pulmonary vasculature characterized by pathologic remodeling of the pulmonary vasculature and right ventricle (RV), increased production and deposition of structural and non-structural proteins, and altered expression of ECM growth factors and proteases. Furthermore, ECM remodeling plays a significant role in disease progression as several dynamic changes in its composition, quantity, and organization are documented in both humans and animal models of disease. These ECM changes impact upon vascular cell biology and affect proliferation of resident cells. Further, ECM components determine the tissue architecture of the pulmonary and myocardial vasculature as well as the myocardium itself, and provide mechanical stability crucial for tissue homeostasis. However, little is known about the basement membrane (BM), a specialized, self-assembled conglomerate of ECM proteins, during remodeling. In the vasculature, the BM is in close physical association with the vascular endothelium and smooth muscle cells. While in the myocardium, each cardiomyocyte is enclosed by a BM that serves as the interface between cardiomyocytes and the surrounding interstitial matrix. In this review, we provide a brief overview on the current state of knowledge of the BM and its ECM composition and their impact on pulmonary vascular remodeling and RV dysfunction and failure in PAH.

Serum Anti-Collagen IV IgM and IgG Antibodies as Indicators of Low Vascular Turnover of Collagen IV in Patients with Long-Term Complications of Type 2 Diabetes

Thickening of the vascular basement membrane (BM) is a fundamental structural change in the small blood vessels in diabetes. Collagen type IV (CIV) is a major component of the BMs, and monitoring the turnover of this protein in type 2 diabetes (T2D) can provide important information about the mechanisms of vascular damage. The aim of the study was through the use of non-invasive biomarkers of CIV (autoantibodies, derivative peptides, and immune complexes) to investigate vascular turnover of CIV in patients with long-term complications of T2D. We measured serum levels of these biomarkers in 59 T2D patients with micro- and/or macrovascular complications and 20 healthy controls using an ELISA. Matrix metalloproteinases-2 and -9 (MMP-2 and MMP-9) were also tested. In the T2D group, significantly lower levels of CIV markers and significantly higher levels of MMP-2 and MMP-9 were found compared to controls. A significant positive correlation was found between IgM antibody levels against CIV and MMP-2. These findings suggest that vascular metabolism of CIV is decreased in T2D with long-term complications and show that a positive linear relationship exists between MMP-2 levels and CIV turnover in the vascular wall.

Collagen IVα345 dysfunction in glomerular basement membrane diseases. II. Crystal structure of the α345 hexamer

Our recent work identified a genetic variant of the α345 hexamer of the collagen IV scaffold that is present in patients with glomerular basement membrane diseases, Goodpasture’s disease (GP) and Alport syndrome (AS), and phenocopies of AS in knock-in mice. To understand the context of this “Zurich” variant, an 8-amino acid appendage, we developed a construct of the WT α345 hexamer using the single-chain NC1 trimer technology, which allowed us to solve a crystal structure of this key connection module. The α345 hexamer structure revealed a ring of 12 chloride ions at the trimer–trimer interface, analogous to the collagen α121 hexamer, and the location of the 170 AS variants. The hexamer surface is marked by multiple pores and crevices that are potentially accessible to small molecules. Loop-crevice-loop features constitute bioactive sites, where pathogenic pathways converge that are linked to AS and GP, and, potentially, diabetic nephropathy. In Pedchenko et al., we demonstrate that these sites exhibit conformational plasticity, a dynamic property underlying assembly of bioactive sites and hexamer dysfunction. The α345 hexamer structure is a platform to decipher how variants cause AS and how hypoepitopes can be triggered, causing GP. Furthermore, the bioactive sites, along with the pores and crevices on the hexamer surface, are prospective targets for therapeutic interventions.

Collagen IVα345 dysfunction in glomerular basement membrane diseases. III. A functional framework for α345 hexamer assembly

We identified a genetic variant, an 8-residue appendage, of the α345 hexamer of collagen IV present in patients with glomerular basement membrane diseases, Goodpasture’s disease and Alport syndrome, and determined the long-awaited crystal structure of the hexamer. We sought to elucidate how variants cause glomerular basement membrane disease by exploring the mechanism of the hexamer assembly. Chloride ions induced in vitro hexamer assembly in a composition-specific manner in the presence of equimolar concentrations of α3, α4, and α5 NC1 monomers. Chloride ions, together with sulfilimine crosslinks, stabilized the assembled hexamer. Furthermore, the chloride ion–dependent assembly revealed the conformational plasticity of the loop-crevice-loop bioactive sites, a critical property underlying bioactivity and pathogenesis. We explored the native mechanism by expressing recombinant α345 miniprotomers in the cell culture and characterizing the expressed proteins. Our findings revealed NC1-directed trimerization, forming protomers inside the cell; hexamerization, forming scaffolds outside the cell; and a Cl gradient–signaled hexamerization. This assembly detail, along with a crystal structure, provides a framework for understanding hexamer dysfunction. Restoration of the native conformation of bioactive sites and α345 hexamer replacement are prospective approaches to therapeutic intervention.

Collagen IVα345 dysfunction in glomerular basement membrane diseases. I. Discovery of a COL4A3 variant in familial Goodpasture's and Alport diseases

Diseases of the glomerular basement membrane (GBM), such as Goodpasture’s disease (GP) and Alport syndrome (AS), are a major cause of chronic kidney failure and an unmet medical need. Collagen IV^α345 is an important architectural element of the GBM that was discovered in previous research on GP and AS. How this collagen enables GBM to function as a permselective filter and how structural defects cause renal failure remain an enigma. We found a distinctive genetic variant of collagen IV^α345 in both a familial GP case and four AS kindreds that provided insights into these mechanisms. The variant is an 8-residue appendage at the C-terminus of the α3 subunit of the α345 hexamer. A knock-in mouse harboring the variant displayed GBM abnormalities and proteinuria. This pathology phenocopied AS, which pinpointed the α345 hexamer as a focal point in GBM function and dysfunction. Crystallography and assembly studies revealed underlying hexamer mechanisms, as described in Boudko et al. and Pedchenko et al. Bioactive sites on the hexamer surface were identified where pathogenic pathways of GP and AS converge and, potentially, that of diabetic nephropathy (DN). We conclude that the hexamer functions include signaling and organizing macromolecular complexes, which enable GBM assembly and function. Therapeutic modulation or replacement of α345 hexamer could therefore be a potential treatment for GBM diseases, and this knock-in mouse model is suitable for developing gene therapies.

A local regulatory network in the testis mediated by laminin and collagen fragments that supports spermatogenesis

It is almost five decades since the discovery of the hypothalamic-pituitary-testicular axis. This refers to the hormonal axis that connects the hypothalamus, pituitary gland and testes, which in turn, regulates the production of spermatozoa through spermatogenesis in the seminiferous tubules, and testosterone through steroidogenesis by Leydig cells in the interstitium, of the testes. Emerging evidence has demonstrated the presence of a regulatory network across the seminiferous epithelium utilizing bioactive molecules produced locally at specific domains of the epithelium. Studies have shown that biologically active fragments are produced from structural laminin and collagen chains in the basement membrane. Additionally, bioactive peptides are also produced locally in non-basement membrane laminin chains at the Sertoli-spermatid interface known as apical ectoplasmic specialization (apical ES, a testis-specific actin-based anchoring junction type). These bioactive peptides are derived from structural laminins and/or collagens at the corresponding sites through proteolytic cleavage by matrix metalloproteinases (MMPs). They in turn serve as autocrine and/or paracrine factors to modulate and coordinate cellular events across the epithelium by linking the apical and basal compartments, the apical and basal ES, the blood-testis barrier (BTB), and the basement membrane of the tunica propria. The cellular events supported by these bioactive peptides/fragments include the release of spermatozoa at spermiation, remodeling of the immunological barrier to facilitate the transport of preleptotene spermatocytes across the BTB, and the transport of haploid spermatids across the epithelium to support spermiogenesis. In this review, we critically evaluate these findings. Our goal is to identify research areas that deserve attentions in future years. The proposed research also provides the much needed understanding on the biology of spermatogenesis supported by a local network of regulatory biomolecules.

A glycine substitution in the collagenous domain of Col4a3 in mice recapitulates late onset Alport syndrome

Alport syndrome (AS) is a severe inherited glomerulopathy caused by mutations in the genes encoding the α-chains of type-IV collagen, the most abundant component of the extracellular glomerular basement membrane (GBM). Currently most AS mouse models are knockout models for one of the collagen-IV genes. In contrast, about half of AS patients have missense mutations, with single aminoacid substitutions of glycine being the most common. The only mouse model for AS with a homozygous knockin missense mutation, Col4a3-p.Gly1332Glu, was partly described before by our group. Here, a detailed in-depth description of the same mouse is presented, along with another compound heterozygous mouse that carries the glycine substitution in trans with a knockout allele. Both mice recapitulate essential features of AS, including shorten lifespan by 30–35%, increased proteinuria, increased serum urea and creatinine, pathognomonic alternate GBM thinning and thickening, and podocyte foot process effacement. Notably, glomeruli and tubuli respond differently to mutant collagen-IV protomers, with reduced expression in tubules but apparently normal in glomeruli. However, equally important is the fact that in the glomeruli the mutant α3-chain as well as the normal α4/α5 chains seem to undergo a cleavage at, or near the point of the mutation, possibly by the metalloproteinase MMP-9, producing a 35 kDa C-terminal fragment. These mouse models represent a good tool for better understanding the spectrum of molecular mechanisms governing collagen-IV nephropathies and could be used for pre-clinical studies aimed at better treatments for AS.

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Two mouse models were generated that recapitulate essential features of AS patients.

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Glomeruli and tubuli respond differently to mutant collagen IV protomers.

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The mutant colIV protomers in glomeruli probably undergo a cleavage process by MMP9.

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The two AS mouse models represent a good tool for studying collagen-IV nephropathies.

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These models could be used for pre-clinical studies aimed at better treatments.

Discoidin domain receptor 1 activation links extracellular matrix to podocyte lipotoxicity in Alport syndrome

Background

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that is activated by collagens that is involved in the pathogenesis of fibrotic disorders. Interestingly, de novo production of the collagen type I (Col I) has been observed in Col4a3 knockout mice, a mouse model of Alport Syndrome (AS mice). Deletion of the DDR1 in AS mice was shown to improve survival and renal function. However, the mechanisms driving DDR1-dependent fibrosis remain largely unknown.

Methods

Podocyte pDDR1 levels, Collagen and cluster of differentiation 36 (CD36) expression was analyzed by Real-time PCR and Western blot. Lipid droplet accumulation and content was determined using Bodipy staining and enzymatic analysis. CD36 and DDR1 interaction was determined by co-immunoprecipitation. Creatinine, BUN, albuminuria, lipid content, and histological and morphological assessment of kidneys harvested from AS mice treated with Ezetimibe and/or Ramipril or vehicle was performed.

Findings

We demonstrate that Col I-mediated DDR1 activation induces CD36-mediated podocyte lipotoxic injury. We show that Ezetimibe interferes with the CD36/DDR1 interaction in vitro and prevents lipotoxicity in AS mice thus preserving renal function similarly to ramipril.

Interpretation

Our study suggests that Col I/DDR1-mediated lipotoxicity contributes to renal failure in AS and that targeting this pathway may represent a new therapeutic strategy for patients with AS and with chronic kidney diseases (CKD) associated with Col4 mutations.

Funding

This study is supported by the NIH grants R01DK117599, R01DK104753, R01CA227493, U54DK083912, UM1DK100846, U01DK116101, UL1TR000460 (Miami Clinical Translational Science Institute, National Center for Advancing Translational Sciences and the National Institute on Minority Health and Health Disparities), F32DK115109, Hoffmann-La Roche and Alport Syndrome Foundation.

Mild X-linked Alport syndrome due to the COL4A5 G624D variant originating in the Middle Ages is predominant in Central/East Europe and causes kidney failure in midlife

A study of 269 children enrolled into a National Registry for children with persistent glomerular hematuria identified 131 individuals with genetically confirmed X-linked Alport Syndrome. A single variant c.1871G>A p.Gly624Asp (G624D) in COL4A5 was predominant and accounted for 39% of X-linked Alport Syndrome in unrelated Polish families (44 of 113). To evaluate its origins, the genetic variation in a 2.79 Mb segment encompassing the COL4A5 locus on chromosome X was assessed. All G624D alleles were found on the same rare haplotype background, indicating a founder effect dating back to the 12-13th century. The phenotypic data of 131 children with X-linked Alport Syndrome and their 195 affected adult relatives revealed that the G624D variant was associated with a significantly milder clinical course in comparison to other pathogenic COL4A5 variants. Furthermore the clinical course of this genetically uniform cohort was milder than that observed in individuals with other COL4A5 missense mutations. In spite of the benign clinical manifestation throughout childhood and early adulthood, the G624D variant confers significant risk for both kidney failure and deafness in males, albeit 20-30 years later than that observed in individuals with other COL4A5 pathogenic variants (50% cumulative risk of starting dialysis at 54 years (95% confidence interval: 50-62) v. 26 years (95% confidence interval: 22-30)). Thus, males with G624D are candidates for existing and emerging therapies for Alport Syndrome.

The basement membrane as a structured surface - role in vascular health and disease

The basement membrane (BM) is a thin specialized extracellular matrix that functions as a cellular anchorage site, a physical barrier and a signaling hub. While the literature on the biochemical composition and biological activity of the BM is extensive, the central importance of the physical properties of the BM, most notably its mechanical stiffness and topographical features, in regulating cellular function has only recently been recognized. In this Review, we focus on the biophysical attributes of the BM and their influence on cellular behavior. After a brief overview of the biochemical composition, assembly and function of the BM, we describe the mechanical properties and topographical structure of various BMs. We then focus specifically on the vascular BM as a nano- and micro-scale structured surface and review how its architecture can modulate endothelial cell structure and function. Finally, we discuss the pathological ramifications of the biophysical properties of the vascular BM and highlight the potential of mimicking BM topography to improve the design of implantable endovascular devices and advance the burgeoning field of vascular tissue engineering.

Nanomedicine Approaches for Advanced Diagnosis and Treatment of Atherosclerosis and Related Ischemic Diseases

Cardiovascular diseases (CVDs) remain one of the major causes of mortality worldwide. In response to this and other worldwide health epidemics, nanomedicine has emerged as a rapidly evolving discipline that involves the development of innovative nanomaterials and nanotechnologies and their applications in therapy and diagnosis. Nanomedicine presents unique advantages over conventional medicines due to the superior properties intrinsic to nanoscopic therapies. Once used mainly for cancer therapies, recently, tremendous progress has been made in nanomedicine that has led to an overall improvement in the treatment and diagnosis of CVDs. This review elucidates the pathophysiology and potential targets of atherosclerosis and associated ischemic diseases. It may be fruitful to pursue future work in the nanomedicine-mediated treatment of CVDs based on these targets. A comprehensive overview is then provided featuring the latest preclinical and clinical outcomes in cardiovascular imaging, biomarker detection, tissue engineering, and nanoscale delivery, with specific emphasis on nanoparticles, nanostructured scaffolds, and nanosensors. Finally, the challenges and opportunities regarding the future development and clinical translation of nanomedicine in related fields are discussed. Overall, this review aims to provide a deep and thorough understanding of the design, application, and future development of nanomedicine for atherosclerosis and related ischemic diseases.

Cdc42 is involved in NC1 peptide-regulated BTB dynamics through actin and microtubule cytoskeletal reorganization

Noncollagenous domain 1 (NC1)-peptide is a biologically active peptide derived from the C-terminal region of collagen α3(IV) chain, a structural constituent protein at the basement membrane in the rat testis, likely via proteolytic cleavage of matrix metalloproteinase 9. Studies have shown that this NC1 peptide regulates testis function by inducing Sertoli cell blood-testis barrier (BTB) remodeling and is also capable of inducing elongate spermatid exfoliation through its disruptive effects on the organization of actin- and microtubule (MT)-based cytoskeletons at these cell adhesion sites. However, the underlying molecular mechanism remains unknown. NC1 peptide was found to exert its biologic effects through an activation of small GTPase cell division control protein 42 homolog (Cdc42) because cooverexpression of the dominant negative mutant of Cdc42 [namely, Cdc42-T17N (via a single mutation of amino acid residue 17 from the N terminus from Thr to Asn by site-directed mutagenesis, making it constitutively inactive)] and NC1 peptide was able to block the NC1 peptide-induced Sertoli cell tight junction-permeability barrier disruption. Their cooverexpression also blocked the NC1 peptide-induced misdistribution of BTB-associated proteins at the cell-cell interface and also disruptive cytoskeletal organization of F-actin and MTs through changes in spatial expression of the corresponding actin and MT regulatory proteins. Interestingly, NC1 peptide was also found to induce an up-regulation of phosphorylated (p)-ribosomal protein S6 (rpS6) (namely, p-rpS6-S235/S236) and a concomitant down-regulation of p-Akt1/2 (namely, p-Akt1-S473 and p-Akt2-S474), but these changes could not be blocked by overexpression of Cdc42-T17N. More importantly, NC1 peptide-induced Cdc42 activation was effectively blocked by treatment of Sertoli cell epithelium with a p-Akt1/2 activator SC79, which is also capable of blocking NC1 peptide-induced down-regulation of p-Akt1-S473 and p-Akt2/S474, but not p-rpS6-S235/S236 up-regulation. In summary, these findings illustrate that Cdc42 is working downstream of the mammalian target of rapamycin complex 1/rpS6/Akt1/2 signaling pathway to support NC1 peptide-mediated effects on Sertoli cell function in the testis using the rat as an animal model.-Su, W., Cheng, C. Y. Cdc42 is involved in NC1 peptide-regulated BTB dynamics through actin and microtubule cytoskeletal reorganization.

Genetic background influences cardiac phenotype in murine chronic kidney disease

Background

Levels of fibroblast growth factor 23 (FGF23) increase early in chronic kidney disease (CKD) and are independently associated with left ventricular hypertrophy (LVH), heart failure and death. Experimental models of CKD with elevated FGF23 and LVH are needed. We hypothesized that slow rates of CKD progression in the Col4a3 knockout (Col4a3KO) mouse model of CKD would promote development of LVH by prolonging exposure to elevated FGF23.

Methods

We studied congenic Col4a3KO and wild-type (WT) mice with either 75% 129X1/SvJ (129Sv) or 94% C57Bl6/J (B6) genomes.

Results

B6-Col4a3KO lived longer than 129Sv-Col4a3KO mice (21.4 ± 0.6 versus 11.4 ± 0.4 weeks; P < 0.05). 10-week-old 129Sv-Col4a3KO mice showed impaired renal function (blood urea nitrogen 191 ± 39 versus 34 ± 4 mg/dL), hyperphosphatemia (14.1 ± 1.4 versus 6.8 ± 0.3 mg/dL) and 33-fold higher serum FGF23 levels (P < 0.05 versus WT for each). Consistent with their slower CKD progression, 10 week-old B6-Col4a3KO mice showed milder impairment of renal function than 129Sv-Col4a3KO mice and modest FGF23 elevation without other alterations of mineral metabolism. At 20 weeks, further declines in renal function in B6-Col4a3KO mice was accompanied by hyperphosphatemia and 8-fold higher FGF23 levels (P < 0.05 versus WT for each). Only the 20-week-old B6-Col4a3KO mice developed LVH (LV mass 125 ± 3 versus 98 ± 6 mg; P < 0.05 versus WT) in association with significantly increased cardiac expression of FGF receptor 4 (FGFR4) messenger RNA and protein and markers of LVH (Atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), beta-myosin heavy chain (β-MHC); P < 0.05 versus WT for each).

Conclusions

In conclusion, B6-Col4a3KO mice manifest slower CKD progression and longer survival than 129Sv-Col4a3KO mice and can serve as a novel model of cardiorenal disease.

The Col4a2em1(IMPC)Wtsi mouse line: lessons from the Deciphering the Mechanisms of Developmental Disorders program

The Deciphering the Mechanisms of Developmental Disorders (DMDD) program uses a systematic and standardised approach to characterise the phenotype of embryos stemming from mouse lines, which produce embryonically lethal offspring. Our study aims to provide detailed phenotype descriptions of homozygous Col4a2^{em1(IMPC)Wtsi} mutants produced in DMDD and harvested at embryonic day 14.5. This shall provide new information on the role Col4a2 plays in organogenesis and demonstrate the capacity of the DMDD database for identifying models for researching inherited disorders. The DMDD Col4a2^{em1(IMPC)Wtsi} mutants survived organogenesis and thus revealed the full spectrum of organs and tissues, the development of which depends on Col4a2 encoded proteins. They showed defects in the brain, cranial nerves, visual system, lungs, endocrine glands, skeleton, subepithelial tissues and mild to severe cardiovascular malformations. Together, this makes the DMDD Col4a2^{em1(IMPC)Wtsi} line a useful model for identifying the spectrum of defects and for researching the mechanisms underlying autosomal dominant porencephaly 2 (OMIM # 614483), a rare human disease. Thus we demonstrate the general capacity of the DMDD approach and webpage as a valuable source for identifying mouse models for rare diseases.

Summary: We define the spectrum of phenotypic abnormalities linked with Col4a2 disruption and demonstrate the opportunities the Deciphering the Mechanisms of Developmental Disorders (DMDD) program offers for exploring rare human diseases.

Loss of function of Colgalt1 disrupts collagen post-translational modification and causes musculoskeletal defects

In a screen for organogenesis defects in N-ethyl-N-nitrosourea (ENU)-induced mutant mice, we discovered a line carrying a mutation in Colgalt1 [collagen beta(1-O)galactosyltransferase type 1], which is required for proper galactosylation of hydroxylysine residues in a number of collagens. Colgalt1 mutant embryos have not been previously characterized; here, we show that they exhibit skeletal and muscular defects. Analysis of mutant-derived embryonic fibroblasts reveals that COLGALT1 acts on collagen IV and VI, and, while collagen VI appears stable and its secretion is not affected, collagen IV accumulates inside of cells and within the extracellular matrix, possibly due to instability and increased degradation. We also generated mutant zebrafish that do not express the duplicated orthologs of mammalian Colgalt1. The double-homozygote mutants have muscle defects; they are viable through the larvae stage but do not survive to 10 days post-fertilization. We hypothesize that the Colgalt1 mutant could serve as a model of a human connective tissue disorder and/or congenital muscular dystrophy or myopathy.

Summary: The authors characterized a novel mouse mutant that has a defect in collagen glycosylation, which appears to affect muscle development. There is very little functional characterization of the affected gene, but this study provides analysis of its embryonic phenotype and the biochemistry of the null mutant, as well as the phenotype of null-mutant zebrafish.

Type IV collagen turnover is predictive of mortality in COPD: a comparison to fibrinogen in a prospective analysis of the ECLIPSE cohort

BACKGROUND

Identifying subjects with chronic obstructive pulmonary disease (COPD) at high risk of exacerbation and mortality is key to aid individual management of COPD. The only FDA approved blood-based drug development biomarker for patients at high risk of mortality, is plasma fibrinogen. In this study, we benchmarked two biomarkers of basement membrane remodeling, a characteristic of COPD, against plasma fibrinogen alone and as a combination. The biomarkers of basement membrane remodeling are two neoepitopes from of the alpha 3 chain of type IV collagen (COL4A3).

MATERIALS AND METHODS

COL4A3 degradation was assessed by the biomarkers C4Ma3 and tumstatin (TUM) in year 1 plasma samples in 984 COPD subjects, 95 non-smoking controls and 95 smoking controls from the Evaluation of COPD Longitudinally to Identify Predictive Surrogate End-points (ECLIPSE) cohort. They were measured by competitive ELISA using monoclonal antibodies recognizing two specific MMP-generated cleavage site within COL4A3. The level of fibrinogen was previously assessed in year 1 plasma.

RESULTS

In COPD subjects, plasma C4Ma3 levels were significantly correlated with plasma fibrinogen levels (0.389 (P < 0.0001)). Cox proportional-hazards regression adjusted for relevant confounders showed that high levels of plasma C4Ma3, but not TUM, were related to a higher risk of mortality (hazard ratio 5.12 (95% CI 2.28-11.50), P < 0.0001). High levels of plasma fibrinogen were not associated with all-cause mortality in this subpopulation, contradictory to published results. Whereas plasma C4Ma3 multiplied by fibrinogen showed to be related to a higher risk of mortality (hazard ratio 5.74 (95% CI 2.65-12.41), P < 0.0001). Plasma C4Ma3 levels were related to the number of hospitalizations due to COPD exacerbations in the year before study start (P = 0.0375). Fibrinogen levels were related to hospitalized exacerbations prior to study start (P = 0.0058) and were also related to future exacerbations (P < 0.0001).

CONCLUSION

We compared herein fibrinogen, C4Ma3 and TUM as biomarkers for COPD prognosis. Fibrinogen was related to future exacerbation, whereas C4Ma3 and the combination of C4Ma3 with fibrinogen were superior to fibrinogen alone in predicting mortality. This pilot study suggests that the assessment of plasma C4Ma3 could be important for identifying COPD patients with a poor prognosis.

TRIAL REGISTRATION

NCT00292552 , GSK Study No. SCO104960.

Collagen type-IV Langmuir and Langmuir-Schäfer layers as model biointerfaces to direct stem cell adhesion

In biomaterial development, the design of material surfaces that mimic the extra-cellular matrix (ECM) in order to achieve favorable cellular instruction is rather challenging. Collagen-type IV (Col-IV), the major scaffolding component of Basement Membranes (BM), a specialized ECM with multiple biological functions, has the propensity to form networks by self-assembly and supports adhesion of cells such as endothelial cells or stem cells. The preparation of biomimetic Col-IV network-like layers to direct cell responses is difficult. We hypothesize that the morphology of the layer, and especially the density of the available adhesion sites, regulates the cellular adhesion to the layer. The Langmuir monolayer technique allows for preparation of thin layers with precisely controlled packing density at the air-water (A-W) interface. Transferring these layers onto cell culture substrates using the Langmuir-Schäfer (LS) technique should therefore provide a pathway for preparation of BM mimicking layers with controlled cell adherence properties. In situ characterization using ellipsometry and polarization modulation-infrared reflection absorption spectroscopy of Col-IV layer during compression at the A-W interface reveal that there is linear increase of surface molecule concentration with negligible orientational changes up to a surface pressure of 25 mN m^-1. Smooth and homogeneous Col-IV network-like layers are successfully transferred by LS method at 15 mN m^-1 onto poly(ethylene terephthalate) (PET), which is a common substrate for cell culture. In contrast, the organization of Col-IV on PET prepared by the traditionally employed solution deposition method results in rather inhomogeneous layers with the appearance of aggregates and multilayers. Progressive increase in the number of early adherent mesenchymal stem cells (MSCs) after 24 h by controlling the areal Col-IV density by LS transfer at 10, 15 and 20 mN m^-1 on PET is shown. The LS method offers the possibility to control protein characteristics on biomaterial surfaces such as molecular density and thereby, modulate cell responses.

Basement membrane and stroke

Located at the interface of the circulation system and the CNS, the basement membrane (BM) is well positioned to regulate blood-brain barrier (BBB) integrity. Given the important roles of BBB in the development and progression of various neurological disorders, the BM has been hypothesized to contribute to the pathogenesis of these diseases. After stroke, a cerebrovascular disease caused by rupture (hemorrhagic) or occlusion (ischemic) of cerebral blood vessels, the BM undergoes constant remodeling to modulate disease progression. Although an association between BM dissolution and stroke is observed, how each individual BM component changes after stroke and how these components contribute to stroke pathogenesis are mostly unclear. In this review, I first briefly introduce the composition of the BM in the brain. Next, the functions of the BM and its major components in BBB maintenance under homeostatic conditions are summarized. Furthermore, the roles of the BM and its major components in the pathogenesis of hemorrhagic and ischemic stroke are discussed. Last, unsolved questions and potential future directions are described. This review aims to provide a comprehensive reference for future studies, stimulate the formation of new ideas, and promote the generation of new genetic tools in the field of BM/stroke research.

A current perspective of canstatin, a fragment of type IV collagen alpha 2 chain

Type IV collagen is a main component of basement membrane extracellular matrix. Canstatin, a non-collagenous C-terminal fragment of type IV collagen α2 chain, was firstly identified as an endogenous anti-angiogenic and anti-tumor factor, which also has an anti-lymphangiogenic effect. Then, canstatin has been widely investigated as a novel target molecule for cancer therapy. The anti-angiogenic effect of canstatin may be also useful for the treatment of ocular neovascularization. Recently, we have demonstrated that canstatin, which is abundantly expressed in the heart tissue, exerts various biological activities in cardiac cells. In rat H9c2 cardiomyoblasts, canstatin inhibits isoproterenol- or hypoxia-induced apoptosis. Canstatin plays an important role in modulating voltage-dependent calcium channel activity in rat cardiomyocytes. Canstatin also regulates various biological functions in rat cardiac fibroblasts and myofibroblasts. The expression of canstatin decreases in the infarcted area after myocardial infarction. This review focuses on a current perspective for the roles of canstatin in tumorigenesis, ocular neovascularization and cardiac pathology.

Basement membrane and blood-brain barrier

The blood–brain barrier (BBB) is a highly complex and dynamic structure, mainly composed of brain microvascular endothelial cells, pericytes, astrocytes and the basement membrane (BM). The vast majority of BBB research focuses on its cellular constituents. Its non-cellular component, the BM, on the other hand, is largely understudied due to its intrinsic complexity and the lack of research tools. In this review, we focus on the role of the BM in BBB integrity. We first briefly introduce the biochemical composition and structure of the BM. Next, the biological functions of major components of the BM in BBB formation and maintenance are discussed. Our goal is to provide a concise overview on how the BM contributes to BBB integrity.

Clinicopathological features and outcome of antibody-negative anti-glomerular basement membrane disease

AIM

To explore the clinicopathological characteristics of patients with anti-GBM antibody-negative anti-GBM disease.

METHODS

The clinical and renal pathological findings were retrospectively studied in 19 patients. All patients met the following inclusion criteria: linear GBM IgG deposition on immunofluorescence(IF); and lack of serum anti-GBM antibodies by ELISA and indirect immunofluorescence assay.

RESULTS

There were 17 male and two female patients, with a median age of 36 years (range 15-61 years). Hypertension was present in 68% of cases, nephrotic-range proteinuria (> 3.5 g/24 hours) in 42%, nephrotic syndrome in 37%, microhaematuria in 95%, renal insufficiency in 63% and lung involvement in 16%. On biopsy all patients had linear GBM staining for polyclonal IgG by IF. The dominant IgG subtype was IgG4 or IgG1. By light microscopy, mesangial proliferative GN without crescents was seen in four patients; proliferative GN (mesangial proliferative GN in eight; endocapillary proliferative GN in two; and membranoproliferative GN in two) with crescents (focal in 11; diffuse in one) in 12 patients; and crescentic GN without mesangial or endocapillary proliferative or membranoproliferative changes in three patients. By electron microscopy, six patients showed scarce electron dense deposits in glomeruli and 11 patients had global podocyte effacement. Totally, 10 (53%) patients received immunosuppressive therapy. The median follow-up was 15 months and six (32%) patients progressed to end-stage renal disease.

CONCLUSIONS

Anti-GBM antibody-negative anti-GBM disease was different from classic anti-GBM disease clinically and pathologically. The pathogenesis of the renal injury in these patients has not been elucidated until now and it should be studied and identified further.

Alport syndrome and Pierson syndrome: Diseases of the glomerular basement membrane

The glomerular basement membrane (GBM) is an important component of the kidney's glomerular filtration barrier. Like all basement membranes, the GBM contains type IV collagen, laminin, nidogen, and heparan sulfate proteoglycan. It is flanked by the podocytes and glomerular endothelial cells that both synthesize it and adhere to it. Mutations that affect the GBM's collagen α3α4α5(IV) components cause Alport syndrome (kidney disease with variable ear and eye defects) and its variants, including thin basement membrane nephropathy. Mutations in LAMB2 that impact the synthesis or function of laminin α5β2γ1 (LM-521) cause Pierson syndrome (congenital nephrotic syndrome with eye and neurological defects) and its less severe variants, including isolated congenital nephrotic syndrome. The very different types of kidney diseases that result from mutations in collagen IV vs. laminin are likely due to very different pathogenic mechanisms. A better understanding of these mechanisms should lead to targeted therapeutic approaches that can help people with these rare but important diseases.

Reliability of the skin blotting method when used on the elderly

The aim of this study was to compare protein secretion on intact skin of extremities and verify the relationship between the marker proteins on abdominal skin and systemic factors using skin blotting. A cross-sectional study was conducted among elderly patients aged 65 years and older (N = 73) at a long-term medical facility in Japan. Skin blotting was performed on the right and left forearms, right and left lower legs, and abdomen. Pearson's correlations and Bland-Altman plots were utilised for comparing the protein secretion from the skin between the right or left forearms or lower legs. Multiple regression analysis was applied to determine the relationship between intensity levels of 3 proteins on the abdominal skin and the systemic factors. Bland-Altman plots demonstrated that there was no significant difference between right and left secretion levels on the forearms and lower legs among 3 proteins. Multiple regression analysis showed that age and antiplatelet use was positively associated with decreased collagen type IV and increased matrix metalloproteinase 2 levels, respectively. Our findings suggested that collecting samples from either the right or the left skin would be sufficient if skin properties between arms and legs are evaluated using skin blotting.

Laminin-521 Protein Therapy for Glomerular Basement Membrane and Podocyte Abnormalities in a Model of Pierson Syndrome

Background Laminin α5β2γ1 (LM-521) is a major component of the GBM. Mutations in LAMB2 that prevent LM-521 synthesis and/or secretion cause Pierson syndrome, a rare congenital nephrotic syndrome with diffuse mesangial sclerosis and ocular and neurologic defects. Because the GBM is uniquely accessible to plasma, which permeates endothelial cell fenestrae, we hypothesized that intravenous delivery of LM-521 could replace the missing LM-521 in the GBM of Lamb2 mutant mice and restore glomerular permselectivity.Methods We injected human LM-521 (hLM-521), a macromolecule of approximately 800 kD, into the retro-orbital sinus of Lamb2-/- pups daily. Deposition of hLM-521 into the GBM was investigated by fluorescence microscopy. We assayed the effects of hLM-521 on glomerular permselectivity by urinalysis and the effects on podocytes by desmin immunostaining and ultrastructural analysis of podocyte architecture.Results Injected hLM-521 rapidly and stably accumulated in the GBM of all glomeruli. Super-resolution imaging showed that hLM-521 accumulated in the correct orientation in the GBM, primarily on the endothelial aspect. Treatment with hLM-521 greatly reduced the expression of the podocyte injury marker desmin and attenuated the foot process effacement observed in untreated pups. Moreover, treatment with hLM-521 delayed the onset of proteinuria but did not prevent nephrotic syndrome, perhaps due to its absence from the podocyte aspect of the GBM.Conclusions These studies show that GBM composition and function can be altered in vivovia vascular delivery of even very large proteins, which may advance therapeutic options for patients with abnormal GBM composition, whether genetic or acquired.

Multiscale modeling of keratin, collagen, elastin and related human diseases: Perspectives from atomistic to coarse-grained molecular dynamics simulations

Scleroproteins are an important category of proteins within the human body that adopt filamentous, elongated conformations in contrast with typical globular proteins. These include keratin, collagen, and elastin, which often serve a common mechanical function in structural support of cells and tissues. Genetic mutations alter these proteins, disrupting their functions and causing diseases. Computational characterization of these mutations has proven to be extremely valuable in identifying the intricate structure-function relationships of scleroproteins from the molecular scale up, especially if combined with multiscale experimental analysis and the synthesis of model proteins to test specific structure-function relationships. In this work, we review numerous critical diseases that are related to keratin, collagen, and elastin, and through several case studies, we propose ways of extensively utilizing multiscale modeling, from atomistic to coarse-grained molecular dynamics simulations, to uncover the molecular origins for some of these diseases and to aid in the development of novel cures and therapies. As case studies, we examine the effects of the genetic disease Epidermolytic Hyperkeratosis (EHK) on the structure and aggregation of keratins 1 and 10; we propose models to understand the diseases of Osteogenesis Imperfecta (OI) and Alport syndrome (AS) that affect the mechanical and aggregation properties of collagen; and we develop atomistic molecular dynamics and elastic network models of elastin to determine the role of mutations in diseases such as Cutis Laxa and Supravalvular Aortic Stenosis on elastin's structure and molecular conformational motions and implications for assembly.

Canstatin inhibits isoproterenol-induced apoptosis through preserving mitochondrial morphology in differentiated H9c2 cardiomyoblasts

Canstatin, a non-collagenous fragment, is cleaved from type IV collagen α2 chain, an essential component of basement membrane surrounding cardiomyocytes. Although canstatin is known as an endogenous anti-angiogenic factor, its effects on cardiomyocytes have not been clarified. This study examined the effects of canstatin on isoproterenol-induced apoptosis in differentiated H9c2 cardiomyoblasts. Retinoic acid was used to differentiate H9c2 myoblast to cardiomyocyte-like phenotype. Cell viability was determined by a cell counting assay. Western blotting was performed to detect expression of cleaved casepase-3 and phosphorylation of dynamin related protein (Drp)1 at Ser637 which regulates mitochondrial fission. Mito Sox Red staining was performed to examine a mitochondria-dependent production of reactive oxygen species (ROS). Mitochondrial morphology was detected by Mito Tracker Red staining. Isoproterenol (100 μM, 48 h) significantly decreased cell viability and increased cleaved caspase-3 expression, which were inhibited by canstatin (10-250 ng/ml) in a concentration-dependent manner. Canstatin suppressed the isoproterenol-induced mitochondrial fission but not ROS. Canstatin also inhibited the isoproterenol-induced dephosphorylation of Drp1 at Ser637. In conclusion, canstatin inhibits isoproterenol-induced apoptosis through the inhibition of mitochondrial fission via the suppression of dephosphorylation of Drp1 at Ser637 in differentiated H9c2 cardiomyoblasts.

Strategies for Optimizing the Soft Tissue Seal around Osseointegrated Implants

Percutaneous and permucosal devices such as catheters, infusion pumps, orthopedic, and dental implants are commonly used in medical treatments. However, these useful devices breach the soft tissue barrier that protects the body from the outer environment, and thus increase bacterial infections resulting in morbidity and mortality. Such associated infections can be prevented if these devices are effectively integrated with the surrounding soft tissue, and thus creating a strong seal from the surrounding environment. However, so far, there are no percutaneous/permucosal medical devices able to prevent infection by achieving strong integration at the soft tissue-device interface. This review gives an insight into the current status of research into soft tissue-implant interface and the challenges associated with these interfaces. Biological soft/hard tissue interfaces may provide insights toward engineering better soft tissue interfaces around percutaneous devices. In this review, focus is put on the history and current findings as well as recent progress of the strategies aiming to develop a strong soft tissue seal around osseointegrated implants, such as orthopedic and dental implants.

Chikungunya virus dissemination from the midgut of Aedes aegypti is associated with temporal basal lamina degradation during bloodmeal digestion

In the mosquito, the midgut epithelium is the initial tissue to become infected with an arthropod-borne virus (arbovirus) that has been acquired from a vertebrate host along with a viremic bloodmeal. Following its replication in midgut epithelial cells, the virus needs to exit the midgut and infect secondary tissues including the salivary glands before it can be transmitted to another vertebrate host. The viral exit mechanism from the midgut, the midgut escape barrier (MEB), is poorly understood although it is an important determinant of mosquito vector competence for arboviruses. Using chikungunya virus (CHIKV) as a model in Aedes aegypti, we demonstrate that the basal lamina (BL) of the extracellular matrix (ECM) surrounding the midgut constitutes a potential barrier for the virus. The BL, predominantly consisting of collagen IV and laminin, becomes permissive during bloodmeal digestion in the midgut lumen. Bloodmeal digestion, BL permissiveness, and CHIKV dissemination are coincident with increased collagenase activity, diminished collagen IV abundance, and BL shredding in the midgut between 24–32 h post-bloodmeal. This indicates that there may be a window-of-opportunity during which the MEB in Ae. aegypti becomes permissive for CHIKV. Matrix metalloproteinases (MMPs) are the principal extracellular endopeptidases responsible for the degradation/remodeling of the ECM including the BL. We focused on Ae. aegypti (Ae)MMP1, which is expressed in midgut epithelial cells, is inducible upon bloodfeeding, and shows collagenase (gelatinase) activity. However, attempts to inhibit AeMMP activity in general or specifically that of AeMMP1 did not seem to affect its function nor produce an altered midgut escape phenotype. As an alternative, we silenced and overexpressed the Ae. aegyptitissue inhibitor of metalloproteinases (AeTIMP) in the mosquito midgut. AeTIMP was highly upregulated in the midgut during bloodmeal digestion and was able to inhibit MMP activity in vitro. Bloodmeal-inducible, midgut-specific overexpression of AeTIMP or its expression via a recombinant CHIKV significantly increased midgut dissemination rates of the virus. Possibly, AeTIMP overexpression affected BL degradation and/or restoration thereby increasing the midgut dissemination efficiency of the virus.

The biological nature of the midgut escape barrier in insects for arthropod-borne viruses has been a mystery for decades. Here we show that the basal lamina (BL) surrounding the mosquito midgut acts as a barrier for chikungunya virus, an alphavirus, which has emerged in the New World hemisphere around three years ago. The barrier became permissive for the virus during digestion of a viremic bloodmeal inside the midgut lumen. Concurrent with BL permissiveness, we observed that collagen IV, a major component of the BL became temporally degraded while the BL was visibly damaged. Based on previous findings, we hypothesized that matrix metalloproteinases such as Ae. aegypti (Ae)MMP1 may be involved in BL degradation. We confirmed that recombinant AeMMP1 exhibited strong gelatinase activity, which was profoundly reduced when recombinant AeMMP1 interacted in vitro with the recombinant Ae. aegypti tissue inhibitor of metalloproteinases (AeTIMP). When transgenically overexpressing AeTIMP in an attempt to temporally inhibit general MMP activity in the mosquito midgut, we observed that the dissemination efficiency of chikungunya virus became significantly increased, while its midgut infection was not affected. It is possible that AeTIMP overexpression affected BL degradation/restoration permitting increased quantities of virus to escape from the midgut.

Inter-adipocyte Adhesion and Signaling by Collagen IV Intercellular Concentrations in Drosophila

Sheet-forming Collagen IV is the main component of basement membranes, which are planar polymers of extracellular matrix underlying epithelia and surrounding organs in all animals. Adipocytes in both insects and mammals are mesodermal in origin and often classified as mesenchymal. However, they form true tissues where cells remain compactly associated. Neither the mechanisms providing this tissue-level organization nor its functional significance are known. Here we show that discrete Collagen IV intercellular concentrations (CIVICs), distinct from basement membranes and thicker in section, mediate inter-adipocyte adhesion in Drosophila. Loss of these Collagen-IV-containing structures in the larval fat body caused intercellular gaps and disrupted continuity of the adipose tissue layer. We also found that Integrin and Syndecan matrix receptors attach adipocytes to CIVICs and direct their formation. Finally, we show that Integrin-mediated adhesion to CIVICs promotes normal adipocyte growth and prevents autophagy through Src-Pi3K-Akt signaling. Our results evidence a surprising non-basement membrane role of Collagen IV in non-epithelial tissue morphogenesis while demonstrating adhesion and signaling functions for these structures.

Antiglomerular Basement Membrane Disease in a Pediatric Patient: A Case Report and Review of the Literature

Goodpasture's syndrome (GPS) remains a very rare disease entity in the pediatric population characterized by the presence of pulmonary hemorrhage and rapidly evolving glomerulonephritis. We hereby describe the case of a 2-year-old girl who presented with renal failure and was diagnosed with GPS. A brief review of the literature in regard to data on demographics, pathogenesis, clinical features, diagnosis, treatment, and prognosis for renal recovery is also provided.