Laminins: structure and genetic regulation

Bioactive Hydrogels Inspired by Laminin: An Emerging Biomaterial for Tissue Engineering Applications

Tissue or organ damage due to severe injuries or chronic diseases can adversely affect the quality of life. Current treatments rely on organ or tissue transplantation which has limitations including unavailability of donors, ethical issues, or immune rejection after transplantations. These limitations can be addressed by tissue regeneration which involves the development of bioactive scaffolds closely mimicking the extracellular matrix (ECM). One of the major components of ECM is the laminin protein which supports several tissues associated with important organs. In this direction, peptide-based hydrogels can effectively mimic the essential characteristics of laminin. While several reports have discussed the structure of laminin, the potential of laminin-derived peptide hydrogels as effective biomaterial for tissue engineering applications is yet to be discussed. In this context, the current review focuses on the structure of laminin and its role as an essential ECM protein. Further, the potential of short peptide hydrogels in mimicking the crucial properties of laminin is proposed. The review further highlights the significance of bioactive hydrogels inspired by laminin - in addressing numerous tissue engineering applications including angiogenesis, neural, skeletal muscle, liver, and adipose tissue regeneration along with a brief outlook on the future applications of these laminin-based hydrogels.

The Role of the Pancreatic Extracellular Matrix as a Tissue Engineering Support for the Bioartificial Pancreas

Type 1 diabetes mellitus (T1DM) is a chronic condition primarily managed with insulin replacement, leading to significant treatment costs. Complications include vasculopathy, cardiovascular diseases, nephropathy, neuropathy, and reticulopathy. Pancreatic islet transplantation is an option but its success does not depend solely on adequate vascularization. The main limitations to clinical islet transplantation are the scarcity of human pancreas, the need for immunosuppression, and the inadequacy of the islet isolation process. Despite extensive research, T1DM remains a major global health issue. In 2015, diabetes affected approximately 415 million people, with projected expenditures of USD 1.7 trillion by 2030. Pancreas transplantation faces challenges due to limited organ availability and complex vascularization. T1DM is caused by the autoimmune destruction of insulin-producing pancreatic cells. Advances in biomaterials, particularly the extracellular matrix (ECM), show promise in tissue reconstruction and transplantation, offering structural and regulatory functions critical for cell migration, differentiation, and adhesion. Tissue engineering aims to create bioartificial pancreases integrating insulin-producing cells and suitable frameworks. This involves decellularization and recellularization techniques to develop biological scaffolds. The challenges include replicating the pancreas's intricate architecture and maintaining cell viability and functionality. Emerging technologies, such as 3D printing and advanced biomaterials, have shown potential in constructing bioartificial organs. ECM components, including collagens and glycoproteins, play essential roles in cell adhesion, migration, and differentiation. Clinical applications focus on developing functional scaffolds for transplantation, with ongoing research addressing immunological responses and long-term efficacy. Pancreatic bioengineering represents a promising avenue for T1DM treatment, requiring further research to ensure successful implementation.

Involvement of BCR::ABL1 in laminin adhesion of Philadelphia chromosome-positive acute lymphoblastic leukemia through upregulation of integrin α6

BACKGROUND

Adhesion of cancer cells to extracellular matrix laminin through the integrin superfamily reportedly induces drug resistance. Heterodimers of integrin α6 (CD49f) with integrin β1 (CD29) or β4 (CD104) are major functional receptors for laminin. Higher CD49f expression is reportedly associated with a poorer response to induction therapy in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Moreover, a xenograft mouse model transplanted with primary BCP-ALL cells revealed that neutralized antibody against CD49f improved survival after chemotherapy.

AIMS

Considering the poor outcomes in Philadelphia chromosome (Ph)-positive ALL treated with conventional chemotherapy without tyrosine kinase inhibitors, we sought to investigate an involvement of the laminin adhesion.

METHODS AND RESULTS

Ph-positive ALL cell lines expressed the highest levels of CD49f among the BCP-ALL cell lines with representative translocations, while CD29 and CD104 were ubiquitously expressed in BCP-ALL cell lines. The association of Ph-positive ALL with high levels of CD49f gene expression was also confirmed in two databases of childhood ALL cohorts. Ph-positive ALL cell lines attached to laminin and their laminin-binding properties were disrupted by blocking antibodies against CD49f and CD29 but not CD104. The cell surface expression of CD49f, but not CD29 and CD104, was downregulated by imatinib treatment in Ph-positive ALL cell lines, but not in their T315I-acquired sublines. Consistently, the laminin-binding properties were disrupted by the imatinib pre-treatment in the Ph-positive ALL cell line, but not in its T315I-acquired subline.

CONCLUSION

BCR::ABL1 plays an essential role in the laminin adhesion of Ph-positive ALL cells through upregulation of CD49f.

Observing Dynamic Conformational Changes within the Coiled-Coil Domain of Different Laminin Isoforms Using High-Speed Atomic Force Microscopy

Laminins are trimeric glycoproteins with important roles in cell-matrix adhesion and tissue organization. The laminin α, ß, and γ-chains have short N-terminal arms, while their C-termini are connected via a triple coiled-coil domain, giving the laminin molecule a well-characterized cross-shaped morphology as a result. The C-terminus of laminin alpha chains contains additional globular laminin G-like (LG) domains with important roles in mediating cell adhesion. Dynamic conformational changes of different laminin domains have been implicated in regulating laminin function, but so far have not been analyzed at the single-molecule level. High-speed atomic force microscopy (HS-AFM) is a unique tool for visualizing such dynamic conformational changes under physiological conditions at sub-second temporal resolution. After optimizing surface immobilization and imaging conditions, we characterized the ultrastructure of laminin-111 and laminin-332 using HS-AFM timelapse imaging. While laminin-111 features a stable S-shaped coiled-coil domain displaying little conformational rearrangement, laminin-332 coiled-coil domains undergo rapid switching between straight and bent conformations around a defined central molecular hinge. Complementing the experimental AFM data with AlphaFold-based coiled-coil structure prediction enabled us to pinpoint the position of the hinge region, as well as to identify potential molecular rearrangement processes permitting hinge flexibility. Coarse-grained molecular dynamics simulations provide further support for a spatially defined kinking mechanism in the laminin-332 coiled-coil domain. Finally, we observed the dynamic rearrangement of the C-terminal LG domains of laminin-111 and laminin-332, switching them between compact and open conformations. Thus, HS-AFM can directly visualize molecular rearrangement processes within different laminin isoforms and provide dynamic structural insight not available from other microscopy techniques.

Infiltrating CD8+ T cells and M2 macrophages are retained in tumor matrix tracks enriched in low tension fibronectin fibers

Tracks rich in matrix and cells, as described in several cancer types, have immunosuppressive functions and separate tumor nests and stroma, yet their origin is unknown. Immunostainings of cryosections from mouse breast tumors show that these tracks are bordered by an endothelial-like basement membrane, filled with fibers of collagen adjacent to tenascin-C (TNC) and low-tension fibronectin (Fn) fibers. While present in early-stage tumors and maturing with time, tracks still form under TNC KO conditions, however, host (not tumor cell)-derived TNC is important for track maturation. Tumor infiltrating leukocytes (mostly M2 macrophages and CD8+ T cells) are retained in tracks of early-stage tumors. Following track maturation, retained tumor infiltrating leukocyte (TIL) numbers get reduced and more CD8+ TIL enter the tumor nests in the absence of TNC. As these tracks are enriched with platelets and fibrinogen and have a demarcating endothelial-like basement membrane often adjacent to endothelial cells, this suggests a role of blood vessels in the formation of these tracks. The Fn fiber tension probe FnBPA5 colocalizes with TNC and immune cells in the tracks and shows decreased binding in tracks lacking TNC. Consequently, FnBPA5 can serve as probe for tumor matrix tracks that have immune suppressive properties.

Neuro-nanotechnology: diagnostic and therapeutic nano-based strategies in applied neuroscience

Artificial, de-novo manufactured materials (with controlled nano-sized characteristics) have been progressively used by neuroscientists during the last several decades. The introduction of novel implantable bioelectronics interfaces that are better suited to their biological targets is one example of an innovation that has emerged as a result of advanced nanostructures and implantable bioelectronics interfaces, which has increased the potential of prostheses and neural interfaces. The unique physical-chemical properties of nanoparticles have also facilitated the development of novel imaging instruments for advanced laboratory systems, as well as intelligently manufactured scaffolds and microelectrodes and other technologies designed to increase our understanding of neural tissue processes. The incorporation of nanotechnology into physiology and cell biology enables the tailoring of molecular interactions. This involves unique interactions with neurons and glial cells in neuroscience. Technology solutions intended to effectively interact with neuronal cells, improved molecular-based diagnostic techniques, biomaterials and hybridized compounds utilized for neural regeneration, neuroprotection, and targeted delivery of medicines as well as small chemicals across the blood-brain barrier are all purposes of the present article.

Alu Deletions in LAMA2 and CDH4 Genes Are Key Components of Polygenic Predictors of Longevity

Longevity is a unique human phenomenon and a highly stable trait, characterized by polygenicity. The longevity phenotype occurs due to the ability to successfully withstand the age-related genomic instability triggered by Alu elements. The purpose of our cross-sectional study was to evaluate the combined contribution of ACE*Ya5ACE, CDH4*Yb8NBC516, COL13A1*Ya5ac1986, HECW1*Ya5NBC182, LAMA2*Ya5-MLS19, PLAT*TPA25, PKHD1L1*Yb8AC702, SEMA6A*Yb8NBC597, STK38L*Ya5ac2145 and TEAD1*Ya5ac2013 Alu elements to longevity. The study group included 2054 unrelated individuals aged from 18 to 113 years who are ethnic Tatars from Russia. We analyzed the dynamics of the allele and genotype frequencies of the studied Alu polymorphic loci in the age groups of young (18-44 years old), middle-aged (45-59 years old), elderly (60-74 years old), old seniors (75-89 years old) and long-livers (90-113 years old). Most significant changes in allele and genotype frequencies were observed between the long-livers and other groups. The search for polygenic predictors of longevity was performed using the APSampler program. Attaining longevity was associated with the combinations LAMA2*ID + CDH4*D (OR = 2.23, PBonf = 1.90 × 10-2) and CDH4*DD + LAMA2*ID + HECW1*D (OR = 4.58, PBonf = 9.00 × 10-3) among persons aged between 18 and 89 years, LAMA2*ID + CDH4*D + SEMA6A*I for individuals below 75 years of age (OR = 3.13, PBonf = 2.00 × 10-2), LAMA2*ID + HECW1*I for elderly people aged 60 and older (OR = 3.13, PBonf = 2.00 × 10-2) and CDH4*DD + LAMA2*D + HECW1*D (OR = 4.21, PBonf = 2.60 × 10-2) and CDH4*DD + LAMA2*D + ACE*I (OR = 3.68, PBonf = 1.90 × 10-2) among old seniors (75-89 years old). The key elements of combinations associated with longevity were the deletion alleles of CDH4 and LAMA2 genes. Our results point to the significance for human longevity of the Alu polymorphic loci in CDH4, LAMA2, HECW1, SEMA6A and ACE genes, involved in the integration systems.

Mimicking the Natural Basement Membrane for Advanced Tissue Engineering

Advancements in the field of tissue engineering have led to the elucidation of physical and chemical characteristics of physiological basement membranes (BM) as specialized forms of the extracellular matrix. Efforts to recapitulate the intricate structure and biological composition of the BM have encountered various advancements due to its impact on cell fate, function, and regulation. More attention has been paid to synthesizing biocompatible and biofunctional fibrillar scaffolds that closely mimic the natural BM. Specific modifications in biomimetic BM have paved the way for the development of in vitro models like alveolar-capillary barrier, airway models, skin, blood-brain barrier, kidney barrier, and metastatic models, which can be used for personalized drug screening, understanding physiological and pathological pathways, and tissue implants. In this Review, we focus on the structure, composition, and functions of in vivo BM and the ongoing efforts to mimic it synthetically. Light has been shed on the advantages and limitations of various forms of biomimetic BM scaffolds including porous polymeric membranes, hydrogels, and electrospun membranes This Review further elaborates and justifies the significance of BM mimics in tissue engineering, in particular in the development of in vitro organ model systems.

Lysosomes and the pathogenesis of merosin-deficient congenital muscular dystrophy

Congenital muscular dystrophy type 1A (MDC1A), the most common congenital muscular dystrophy in Western countries, is caused by recessive mutations in LAMA2, the gene encoding laminin alpha 2. Currently, no cure or disease modifying therapy has been successfully developed for MDC1A. Examination of patient muscle biopsies revealed altered distribution of lysosomes. We hypothesized that this redistribution was a novel and potentially druggable aspect of disease pathogenesis. We explored this hypothesis using candyfloss (caf), a zebrafish model of MDC1A. We found that lysosome distribution in caf zebrafish was also abnormal. This altered localization was significantly associated with fiber detachment and could be prevented by blocking myofiber detachment. Overexpression of transcription factor EB, a transcription factor that promotes lysosomal biogenesis, led to increased lysosome content and decreased fiber detachment. We conclude that genetic manipulation of the lysosomal compartment is able to alter the caf zebrafish disease process, suggesting that lysosome function may be a target for disease modification.

Variants in LAMC3 Causes Occipital Cortical Malformation

Occipital cortical malformation (OCCM) is a disease caused by malformations of cortical development characterized by polymicrogyria and pachygyria of the occipital lobes and childhood-onset seizures. The recessive or complex heterozygous variants of the LAMC3 gene are identified as the cause of OCCM. In the present study, we identified novel complex heterozygous variants (c.470G > A and c.4030 + 1G > A) of the LAMC3 gene in a Chinese female with childhood-onset seizures. Cranial magnetic resonance imaging was normal. Functional experiments confirmed that both variant sites caused premature truncation of the laminin γ3 chain. Bioinformatics analysis predicted 10 genes interacted with LAMC3 with an interaction score of 0.4 (P value = 1.0e–16). The proteins encoded by these genes were mainly located in the basement membrane and extracellular matrix component. Furthermore, the biological processes and molecular functions from gene ontology analysis indicated that laminin γ3 chain and related proteins played an important role in structural support and cellular processes through protein-containing complex binding and signaling receptor binding. KEGG pathway enrichment predicted that the LAMC3 gene variant was most likely to participate in the occurrence and development of OCCM through extracellular matrix receptor interaction and PI3K-Akt signaling pathway.

Relapse of pathological angiogenesis: functional role of the basement membrane and potential treatment strategies

Blinding eye diseases such as corneal neovascularization, proliferative diabetic retinopathy, and age-related macular degeneration are driven by pathological angiogenesis. In cancer, angiogenesis is key for tumor growth and metastasis. Current antiangiogenic treatments applied clinically interfere with the VEGF signaling pathway-the main angiogenic pathway-to inhibit angiogenesis. These treatments are, however, only partially effective in regressing new pathologic vessels, and the disease relapses following cessation of treatment. Moreover, the relapse of pathological angiogenesis can be rapid, aggressive and more difficult to treat than angiogenesis in the initial phase. The manner in which relapse occurs is poorly understood; however, recent studies have begun to shed light on the mechanisms underlying the revascularization process. Hypotheses have been generated to explain the rapid angiogenic relapse and increased resistance of relapsed disease to treatment. In this context, the present review summarizes knowledge of the various mechanisms of disease relapse gained from different experimental models of pathological angiogenesis. In addition, the basement membrane-a remnant of regressed vessels-is examined in detail to discuss its potential role in disease relapse. Finally, approaches for gaining a better understanding of the relapse process are discussed, including prospects for the management of relapse in the context of disease.

Zebrafish Models of LAMA2-Related Congenital Muscular Dystrophy (MDC1A)

LAMA2-related congenital muscular dystrophy (CMD; LAMA2-MD), also referred to as merosin deficient CMD (MDC1A), is a severe neonatal onset muscle disease caused by recessive mutations in the LAMA2 gene. LAMA2 encodes laminin α2, a subunit of the extracellular matrix (ECM) oligomer laminin 211. There are currently no treatments for MDC1A, and there is an incomplete understanding of disease pathogenesis. Zebrafish, due to their high degree of genetic conservation with humans, large clutch sizes, rapid development, and optical clarity, have emerged as an excellent model system for studying rare Mendelian diseases. They are particularly suitable as a model for muscular dystrophy because they contain at least one orthologue to all major human MD genes, have muscle that is similar to human muscle in structure and function, and manifest obvious and easily measured MD related phenotypes. In this review article, we present the existing zebrafish models of MDC1A, and discuss their contribution to the understanding of MDC1A pathomechanisms and therapy development.

Liver Matrix in Benign and Malignant Biliary Tract Disease

The extracellular matrix is a highly reactive scaffold formed by a wide array of multifunctional molecules, encompassing collagens and noncollagenous glycoproteins, proteoglycans, glycosaminoglycans, and polysaccharides. Besides outlining the tissue borders, the extracellular matrix profoundly regulates the behavior of resident cells by transducing mechanical signals, and by integrating multiple cues derived from the microenvironment. Evidence is mounting that changes in the biostructure of the extracellular matrix are instrumental for biliary repair. Following biliary damage and eventually, malignant transformation, the extracellular matrix undergoes several quantitative and qualitative modifications, which direct interactions among hepatic progenitor cells, reactive ductular cells, activated myofibroblasts and macrophages, to generate the ductular reaction. Herein, we will give an overview of the main molecular factors contributing to extracellular matrix remodeling in cholangiopathies. Then, we will discuss the structural alterations in terms of biochemical composition and physical stiffness featuring the "desmoplastic matrix" of cholangiocarcinoma along with their pro-oncogenic effects.

Peptide-Based Nanoparticles Mimic Fibrillogenesis of Laminin in Tumor Vessels for Precise Embolization

Cancer therapeutic strategies based on angiogenesis attract great attention from fundamental and clinical research. Blocking oxygen and nutrition supply to tumor cells could inhibit the growth of tumors based on occlusion of blood vessels in the tumor. Herein, we report a dual-responsive peptide-based nanoparticle, mimicking the laminin fibrillogenesis specifically and highly efficiently in tumor vessels, resulting in the blockage of tumor vessels and the growth inhibition of tumors. The laminin mimic peptide (LMMP) is designed with a fibrillation sequence, a pH-responsive sequence, and a targeting sequence. The LMMP in nanoformulations is delivered to blood vessels in the tumors, where the microenvironment (pH and microthrombus) enable LMMP to process laminin fibrillogenesis, constructing fibrous networks. The laminin-like fibrous networks capture red blood cells etc., forming occlusion specifically in the tumor blood vessels to inhibit the growth of the tumor.

Cross-Talk Between Extracellular Matrix and Skeletal Muscle: Implications for Myopathies

Skeletal muscle (SM) comprises around 40% of total body weight and is among the most important plastic tissues, as it supports skeletal development, controls body temperature, and manages glucose levels. Extracellular matrix (ECM) maintains the integrity of SM, enables biochemical signaling, provides structural support, and plays a vital role during myogenesis. Several human diseases are coupled with dysfunctions of the ECM, and several ECM components are involved in disease pathologies that affect almost all organ systems. Thus, mutations in ECM genes that encode proteins and their transmembrane receptors can result in diverse SM diseases, a large proportion of which are types of fibrosis and muscular dystrophy. In this review, we present major ECM components of SMs related to muscle-associated diseases, and discuss two major ECM myopathies, namely, collagen myopathy and laminin myopathies, and their therapeutic managements. A comprehensive understanding of the mechanisms underlying these ECM-related myopathies would undoubtedly aid the discovery of novel treatments for these devastating diseases.

The Adult Murine Intestine is Dependent on Constitutive Laminin-γ1 Synthesis

Laminin-γ1 is required for early embryonic development; however, the need for laminin-γ1 synthesis in adulthood is unknown. A global and inducible mouse model of laminin-γ1 deficiency was generated to address this question. Genetic ablation of the Lamc1 gene in adult mice was rapidly lethal. Despite global Lamc1 gene deletion in tamoxifen-induced mutant mice, there was minimal change in total cardiac, pulmonary, hepatic or renal laminin protein. In contrast, laminin-γ1 was significantly depleted in the small intestines, which showed crypt hyperplasia and dissociation of villous epithelium from adjacent mesenchyme. We conclude that the physiologic requirement for laminin-γ1 synthesis in adult mice is dependent on a tissue-specific basal rate of laminin-γ1 turnover that results in rapid depletion of laminin-γ1 in the intestine.

ADAMTS18 Deficiency Affects Neuronal Morphogenesis and Reduces the Levels of Depression-like Behaviors in Mice

The ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) enzymes are secreted, multi-domain matrix-associated zinc metalloendopeptidases that modify extracellular matrix components and play crucial roles in development and numerous diseases. ADAMTS18 is a member of the ADAMTS family, and genome-wide association studies made an initial association of ADAMTS18 with white matter integrity in healthy people of 72-74 years old. However, the potential roles of ADAMTS18 in central nervous system remain unclear. In this study, we showed that Adamts18 mRNA is highly abundant in developing brains, especially in the cerebellum granular cell layer and the hippocampus dentate gyrus (DG) granular cell layer. Adamts18 knockout (KO) mice displayed higher dendritic branching complexity and spine density on hippocampal DG granular cells. Behavioral tests showed that Adamts18 KO mice had reduced levels of depression-like behaviors compared to their wild-type (WT) littermates. The increased neurite formation could be attributed in part to reduced phosphorylation levels of the collapsin response mediator protein-2 (CRMP2) due to activation of the laminin/PI3K/AKT/GSK-3β signaling pathway. Our findings revealed a critical role of ADAMTS18 in neuronal morphogenesis and emotional control in mice.

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.

Signals in the pancreatic islet microenvironment influence β-cell proliferation

The progressive loss of pancreatic β-cell mass that occurs in both type 1 and type 2 diabetes is a primary factor driving efforts to identify strategies for effectively increasing, enhancing or restoring β-cell mass. While factors that seem to influence β-cell proliferation in specific contexts have been described, reliable stimulation of human β-cell proliferation has remained a challenge. Importantly, β-cells exist in the context of a complex, integrated pancreatic islet microenvironment where they interact with other endocrine cells, vascular endothelial cells, extracellular matrix, neuronal projections and islet macrophages. This review highlights different components of the pancreatic microenvironment, and reviews what is known about how signaling that occurs between β-cells and these other components influences β-cell proliferation. Future efforts to further define the role of the pancreatic islet microenvironment on β-cell proliferation may lead to the development of successful approaches to increase or restore β-cell mass in diabetes.

Structure and Function of Basement Membranes

Basement membranes (BMs) are present in every tissue of the human body. All epithelium and endothelium is in direct association with BMs. BMs are a composite of several large glycoproteins and form an organized scaffold to provide structural support to the tissue and also offer functional input to modulate cellular function. While collagen I is the most abundant protein in the human body, type IV collagen is the most abundant protein in BMs. Matrigel is commonly used as surrogate for BMs in many experiments, but this is a tumor-derived BM–like material and does not contain all of the components that natural BMs possess. The structure of BMs and their functional role in tissues are unique and unlike any other class of proteins in the human body. Increasing evidence suggests that BMs are unique signal input devices that likely fine tune cellular function. Additionally, the resulting endothelial and epithelial heterogeneity in human body is a direct contribution of cell-matrix interaction facilitated by the diverse compositions of BMs.

Spontaneous Helical Structure Formation in Laminin Nanofibers

Laminin is a cross-shaped heterotrimer composed of three polypeptides chains that assembles into an insoluble extracellular matrix (ECM) network as part of the basement membrane, serving a vital role in many processes such as embryonic development, differentiation, and muscle and nerve regeneration. Here we engineered monodisperse laminin nanofibers using a surface-initiated assembly technique in order to investigate how changes in protein composition affect formation and structure of the network. Specifically, we compared laminin 111 with varying degrees of purity and with and without entactin to determine whether these changes alter biophysical properties. All the laminin types were reproducibly patterned as 200 μm long, 20 μm wide nanofibers that were successfuly released during surface-initiated assembly into solution. All nanofibers contracted upon release, and while initial lengths were identical, lengths of released fibers depended on the laminin type. Uniquely, the laminin 111 at high purity (>95%) and without entactin spontaneouly formed helical nanofibers at greater than 90%. Atomic force microscopy revealed that the nanofiber contraction was associated with a change in nanostructure from fibrillar to nodular, suggestive of refolding of laminin molecules into a globular-like conformation. Further, for the high purity laminin that formed helices, the density of the laminin at the edges of the nanofiber was higher than in the middle, providing a possible origin for the differential pre-stress driving the helix formation. Together, these results show that variation in the purity of laminin 111 and presence of entactin can have significant impact on the biophysical properties of the assembled protein networks. This highlights the fact that our understanding of protein assembly and function is still incomplete and that cell-free, in vitro assays can provide unique insights into the ECM.

Human Laminin Isotype Coating for Creating Islet Cell Sheets

Our experimental approach toward the development of new islet-based treatment for diabetes mellitus has been the creation of a monolayered islet cell construct (islet cell sheet), followed by its transplantation into a subcutaneous pocket. Previous studies describe rat laminin-5 (chain composition: α3, β3, γ2) as a suitable extracellular matrix (ECM) for surfaces comprised of a coated temperature-responsive polymer, poly(N-isopropylacrylamide) (PIPAAm). To progress toward the clinical application of this approach, the present study attempted to identify an optimal human ECM as a coating material on PIPAAm surfaces, which allowed islet cells to attach on the surfaces and subsequently to be harvested as a monolithic cell sheet. Dispersed rat islet cells were seeded onto PIPAAm dishes coated with various human laminin isotypes: human laminin (HL)-211, HL-332, HL-411, HL-511, and HL-placenta. Plating efficiency at day 1, the confluency at day 3, and glucose-stimulated insulin secretion test at day 3 were performed. The highest value of plating efficiency was found in the HL-332-PIPAAm group (83.1 ± 0.7%). The HL-332-PIPAAm group also showed the highest cellular confluency (98.6 ± 0.5%). Islet cells cultured on the HL-332-PIPAAm surfaces showed a positive response in the glucose-stimulated insulin secretion test. By reducing culture temperature from 37°C to 20°C in the HL-332-PIPAAm group, cells were able to be harvested as a monolithic islet sheet. The present study showed that HL-332 was an optimal human-derived ECM on a PIPAAm coating for preparing islet cell sheets.

Analysis of nidogen-1/laminin γ1 interaction by cross-linking, mass spectrometry, and computational modeling reveals multiple binding modes

We describe the detailed structural investigation of nidogen-1/laminin γ1 complexes using full-length nidogen-1 and a number of laminin γ1 variants. The interactions of nidogen-1 with laminin variants γ1 LEb2–4, γ1 LEb2–4 N836D, γ1 short arm, and γ1 short arm N836D were investigated by applying a combination of (photo-)chemical cross-linking, high-resolution mass spectrometry, and computational modeling. In addition, surface plasmon resonance and ELISA studies were used to determine kinetic constants of the nidogen-1/laminin γ1 interaction. Two complementary cross-linking strategies were pursued to analyze solution structures of laminin γ1 variants and nidogen-1. The majority of distance information was obtained with the homobifunctional amine-reactive cross-linker bis(sulfosuccinimidyl)glutarate. In a second approach, UV-induced cross-linking was performed after incorporation of the diazirine-containing unnatural amino acids photo-leucine and photo-methionine into laminin γ1 LEb2–4, laminin γ1 short arm, and nidogen-1. Our results indicate that Asn-836 within laminin γ1 LEb3 domain is not essential for complex formation. Cross-links between laminin γ1 short arm and nidogen-1 were found in all protein regions, evidencing several additional contact regions apart from the known interaction site. Computational modeling based on the cross-linking constraints indicates the existence of a conformational ensemble of both the individual proteins and the nidogen-1/laminin γ1 complex. This finding implies different modes of interaction resulting in several distinct protein-protein interfaces.

Neuromuscular disorders in zebrafish: state of the art and future perspectives

Neuromuscular disorders are a broad group of inherited conditions affecting the structure and function of the motor system with polymorphic clinical presentation and disease severity. Although individually rare, collectively neuromuscular diseases have an incidence of 1 in 3,000 and represent a significant cause of disability of the motor system. The past decade has witnessed the identification of a large number of human genes causing muscular disorders, yet the underlying pathogenetic mechanisms remain largely unclear, limiting the developing of targeted therapeutic strategies. To overcome this barrier, model systems that replicate the different steps of human disorders are increasingly being developed. Among these, the zebrafish (Danio rerio) has emerged as an excellent organism for studying genetic disorders of the central and peripheral motor systems. In this review, we will encounter most of the available zebrafish models for childhood neuromuscular disorders, providing a brief overview of results and the techniques, mainly transgenesis and chemical biology, used for genetic manipulation. The amount of data collected in the past few years will lead zebrafish to became a common functional tool for assessing rapidly drug efficacy and off-target effects in neuromuscular diseases and, furthermore, to shed light on new etiologies emerging from large-scale massive sequencing studies.

Laminin and integrin expression in the ventral ectodermal ridge of the mouse embryo: implications for regulation of BMP signalling

BACKGROUND

The ventral ectodermal ridge (VER) is an important signalling centre in the mouse tail-bud following completion of gastrulation. BMP regulation is essential for VER function, but how these signals are transmitted between adjacent tissues is unclear.

RESULTS

We investigated the idea that extracellular matrix components might be involved, using immunohistochemistry and in situ hybridisation to detect all known α, β, and γ laminin chains and their mRNAs in the early tail bud. We identified an apparently novel laminin variant, comprising α5, β3 and γ2 chains, as a major component of the VER basement membrane at E9.5. Strikingly, only the mRNAs for these chains were co-expressed in VER cells, suggesting that lamin532 may be the sole basement membrane laminin at this stage. Since α6 integrin was also expressed in VER cells, this raises the possibility of cell-matrix interactions regulating BMP signalling at this site of caudal morphogenesis.

CONCLUSIONS

Laminin532 could interact with α6-containing integrin to direct differentiation of the specialised VER cells from surface ectoderm.

Laminin α5 guides tissue patterning and organogenesis

Laminins (LM) are extracellular matrix molecules that contribute to and are required for the formation of basement membranes. They participate in the modulation of epithelial/mesenchymal interactions and are implicated in organogenesis and maintenance of organ homeostasis. Among the LM molecules, the LM α5 chain (LMα5) is one of the most widely distributed LM in the developing and mature organism. Its presence in some basement membranes during embryogenesis is absolutely required for maintenance of basement membrane integrity and thus for proper organogenesis. LMα5 also regulates the expression of genes important for major biological processes, in part by repressing or activating signaling pathways, depending upon the physiological context.

Epistatic dissection of laminin-receptor interactions in dystrophic zebrafish muscle

Laminins form essential components of the basement membrane and are integral to forming and maintaining muscle integrity. Mutations in the human Laminin-alpha2 (LAMA2) gene result in the most common form of congenital muscular dystrophy, MDC1A. We have previously identified a zebrafish model of MDC1A called candyfloss (caf), carrying a loss-of-function mutation in the zebrafish lama2 gene. In the skeletal muscle, laminins connect the muscle cell to the extracellular matrix (ECM) by binding either dystroglycan or integrins at the cell membrane. Through epistasis experiments, we have established that both adhesion systems individually contribute to the maintenance of fibre adhesions and exhibit muscle detachment phenotypes. However, larval zebrafish in which both adhesion systems are simultaneously genetically inactivated possess a catastrophic failure of muscle attachment that is far greater than a simple addition of individual phenotypes would predict. We provide evidence that this is due to other crucial laminins present in addition to Lama2, which aid muscle cell attachments and integrity. We have found that lama1 is important for maintaining attachments, whereas lama4 is localized and up-regulated in damaged fibres, which appears to contribute to fibre survival. Importantly, our results show that endogenous secretion of laminins from the surrounding tissues has the potential to reinforce fibre attachments and strengthen laminin-ECM attachments. Collectively these findings provide a better understanding of the cellular pathology of MDC1A and help in designing effective therapies.

Human pathogens utilize host extracellular matrix proteins laminin and collagen for adhesion and invasion of the host

Laminin (Ln) and collagen are multifunctional glycoproteins that play an important role in cellular morphogenesis, cell signalling, tissue repair and cell migration. These proteins are ubiquitously present in tissues as a part of the basement membrane (BM), constitute a protective layer around blood capillaries and are included in the extracellular matrix (ECM). As a component of BMs, both Lns and collagen(s), thus function as major mechanical containment molecules that protect tissues from pathogens. Invasive pathogens breach the basal lamina and degrade ECM proteins of interstitial spaces and connective tissues using various ECM-degrading proteases or surface-bound plasminogen and matrix metalloproteinases recruited from the host. Most pathogens associated with the respiratory, gastrointestinal, or urogenital tracts, as well as with the central nervous system or the skin, have the capacity to bind and degrade Lns and collagen(s) in order to adhere to and invade host tissues. In this review, we focus on the adaptability of various pathogens to utilize these ECM proteins as enhancers for adhesion to host tissues or as a targets for degradation in order to breach the cellular barriers. The major pathogens discussed are Streptococcus, Staphylococcus, Pseudomonas, Salmonella, Yersinia, Treponema, Mycobacterium, Clostridium, Listeria, Porphyromonas and Haemophilus; Candida, Aspergillus, Pneumocystis, Cryptococcus and Coccidioides; Acanthamoeba, Trypanosoma and Trichomonas; retrovirus and papilloma virus.

Pierson syndrome in an adolescent girl with nephrotic range proteinuria but a normal GFR

BACKGROUND

Pierson syndrome, caused by mutations in the LAMB2 gene, was originally described as a combination of microcoria and congenital nephrotic syndrome, rapidly progressing to end-stage renal failure.

CASE-DIAGNOSIS/TREATMENT

We report a minor variant of Pierson syndrome in a teenage girl with severe myopia since early infancy and proteinuria first detected at age 6. At the age of 11 she was found to carry a unique homozygous non-truncating LAMB2 mutation in exon 2: c.T240G (p.S80R). Renal biopsy revealed mild diffuse mesangial sclerosis and residual expression of laminin β2. Today at age 14, on treatment with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, she continues to have nephrotic range proteinuria, but a normal glomerular filtration rate.

CONCLUSIONS

LAMB2 mutations should be considered in all patients with glomerular proteinuria and abnormal ocular phenotype, irrespective of age and disease severity.

Mouse stem cells seeded into decellularized rat kidney scaffolds endothelialize and remodel basement membranes

INTRODUCTION

To address transplant organ shortage, a promising strategy is to decellularize kidneys in a manner that the scaffold retains signals for seeded pluripotent precursor cells to differentiate and recapitulate native structures: matrix-to-cell signaling followed by cell-cell and cell-matrix interactions, thereby remodeling and replacing the original matrix. This would reduce scaffold antigenicity and enable xeno-allografts.

RESULTS

DAPI-labeled cells in arterial vessels and glomeruli were positive for both endothelial lineage markers, BsLB4 and VEGFR2. Rat scaffold's basement membrane demonstrated immunolabeling with anti-mouse laminin β1. Labeling intensified over time with 14 day incubations.

CONCLUSION

We provide new evidence for matrix-to-cell signaling in acellular whole organ scaffolds that induces differentiation of pluripotent precursor cells to endothelial lineage. Production of mouse basement membrane supports remodeling of host (rat)-derived scaffolds and thereby warrants further investigation as a promising approach for xenotransplantation.

METHODS

We previously showed that murine embryonic stem cells arterially seeded into acellular rat whole kidney scaffolds multiply and demonstrate morphologic, immunohistochemical and gene expression evidence for differentiation. Vascular cell endothelialization was now further tested by endothelial specific BsLB4 lectin and anti-VEGFR2 (Flk1) antibodies. Remodeling of the matrix basement membranes from rat to mouse ("murinization") was assessed by a monoclonal antibody specific for mouse laminin β1 chain.

Expression of multisubunit proteins in Leishmania tarentolae

Heterologous gene expression in mammalian cells is the first choice for the production of recombinant proteins when posttranslational modifications affect the biological activity of target proteins. However, the expression efficiency of mammalian cells is relatively low compared to other expression systems, such as Escherichia coli or yeast. Recently, a novel protein expression system based on Leishmania tarentolae, a protozoan parasite of gecko, was developed. This system allows not only easy handling like E. coli and yeast, but also full eukaryotic protein folding and the mammalian-type posttranslational modifications of target proteins. Here, we attempt to produce recombinant human laminin (LM)-332, a large heterotrimeric glycoprotein, in the L. tarentolae expression system. A recombinant strain harboring three subunits of LM-332 efficiently formed a heterotrimer and secreted it into the medium. The purified rLM-332 showed similar cell adhesion activity to rLM-332 purified from mammalian cells, indicating its proper folding and assembly. In this chapter, we describe a detailed protocol for multiple gene expression in the L. tarentolae expression system.

The γ3 chain of laminin is widely but differentially expressed in murine basement membranes: expression and functional studies

Laminins are heterotrimeric extracellular glycoproteins found in, but not confined to, basement membranes (BMs). They are important components in formation of the molecular networks of BMs as well as in cell polarity, cell differentiation and tissue morphogenesis. Each laminin is composed by an α, a β and a γ chain. Previous studies have shown that the γ3 chain is partnered with either the β1 chain (in placenta) or β2 chain (in the CNS) (Libby et al., 2000). Several studies, including our own, suggested that the γ3 chain is expressed in both apical and basal compartments (Koch et al., 1999; Gersdorff et al., 2005; Yan and Cheng, 2006). This study investigates the expression pattern of the γ3 chain in mouse. We developed three new γ3-reactive antibodies, and we show that the γ3 chain is present in BMs. The distribution pattern is considerably more restricted than that of the γ1 chain and within any tissue there is differential deposition into BM compartments. This is particularly true in the retina and brain, where γ3 is uniquely expressed in a subset of the vascular basement membranes and the pial surface. We used conventional genetic ablation techniques to remove the γ3 chain in mice; unlike other laminin null mice (α5, β2, γ1 nulls), these mice live a normal lifespan and have only minor abnormalities, the most striking of which are ectopic granule cells in the cerebellum and an apparent increase in capillary branching in the outer retina. These data support the suggestion that the γ3 chain is deposited in BMs and contributes some unique properties to their function, particularly in the nervous system.

Laminin-β1 impairs spatial learning through inhibition of ERK/MAPK and SGK1 signaling

Laminin is a major structural element of the basal lamina consisting of an α-chain, a β-chain, and a γ-chain arranged in a cross-like structure, with their C-terminal inter-coiled. Laminin is abundantly expressed in the hippocampus of mature brain and is implicated in several psychiatric disorders, but its possible role involved in learning and memory function is not known. This issue was examined here. Our results revealed that water maze training significantly decreased laminin-β1 (LB1) expression in the rat hippocampal CA1 area. Transfection of LB1 WT plasmid to hippocampal CA1 neurons impaired water maze performance in rats. Meanwhile, it decreased the phosphorylation level of ERK/MAPK and protein kinase serum- and glucocorticoid-inducible kinase-1 (SGK1). By contrast, knockdown of endogenous LB1 expression using RNA interference (LB1 siRNA) enhanced water maze performance. Meanwhile, it increased the phosphorylation level of ERK/MAPK and SGK1. The enhancing effect of LB1 siRNA on spatial learning and on the phosphorylation of ERK/MAPK and SGK1 was blocked by co-treatment with the MEK inhibitor U0126 at a concentration that did not apparently affect spatial learning and ERK/MAPK phosphorylation alone. Further, the enhancing effect of LB1 siRNA on spatial learning and SGK1 phosphorylation was similarly blocked by co-transfection with SGK1 siRNA at a concentration that did not markedly affect spatial learning and SGK1 expression alone. These results together indicate that LB1 negatively regulates spatial learning in rats. In addition, LB1 impairs spatial learning through decreased activation of the ERK/MAPK-SGK1 signaling pathway in the rat hippocampus.

Matrix components and scaffolds for sustained islet function

The clinical treatment of diabetes by islet transplantation is limited by low islet survival rates. A fundamental reason for this inefficiency is likely due to the removal of islets from their native environment. The isolation process not only disrupts interactions between blood vessels and endocrine cells, but also dramatically changes islet cell interaction with the extracellular matrix (ECM). Biomolecular cues from the ECM are important for islet survival, proliferation, and function; however, very little is known about the composition of islet ECM and the role each component plays. Without a thorough understanding of islet ECM, current endeavors to prolong islet survival via scaffold engineering lack a systematic basis. The following article reviews current knowledge of islet ECM and attempts to explain the roles they play in islet function. In addition, the effects of in vitro simulations of the native islet scaffold will be evaluated. Greater understanding in these areas will provide a preliminary platform from which a sustainable bioartificial pancreas may be developed.

Infection of retinal epithelial cells with L. amazonensis impacts in extracellular matrix proteins

One of the manifestations of leishmaniases is eye injuries which main characteristics are the injury of the anterior chamber of the eye and the resistance to specific treatments. The retinal pigment epithelial (RPE) cells participate in pathogen-induced intraocular inflammatory processes. We investigated Leishmania amazonensis-RPE cells relationship and its impact in laminin and fibronectin production. Using RPE cell (ARPE-19), we demonstrated that L. amazonensis adhere to these cells in the first hour of infection, whereas parasite internalization was only observed after 6 h. Seventy-two hours after infection, vacuoles with parasites debris were observed intracellularly, and no parasite were observed intra- or extracellularly at the 96 h, suggesting that Leishmania can infect ARPE-19 cells although this cells are able to clear the infection. Fibronectin and laminin were associated with L. amazonensis-ARPE-19 interaction. Confocal analysis showed no substantial alterations in fibronectin presence in ARPE-19-infected or ARPE-19-noninfected cells, whereas laminin levels increased three times 10 h after L. amazonensis infection. After this time, laminin levels decreased in infected cells. These results suggest that L. amazonensis-ARPE-19 infection induces increased production of laminin in the beginning of infection which may facilitate parasite-host cell interactions.

A novel mutation of LAMB2 in a multigenerational mennonite family reveals a new phenotypic variant of Pierson syndrome

PURPOSE

To describe a novel laminin β-2 (LAMB2) mutation associated with nephrotic syndrome and severe retinal disease without microcoria in a large, multigenerational family with Pierson syndrome.

DESIGN

Retrospective chart review and prospective family examination.

PARTICIPANTS

An extended consanguineous family of 52 members.

METHODS

The eyes, urine, and serum DNA were evaluated in all family members after discovering 2 patients, both younger than 10 years, with bilateral retinal detachments and concurrent renal dysfunction. Linkage analysis was performed in the 9 living affected individuals, 7 using the Illumina Human Hap370 Duo Bead Array (Illumina, San Diego, CA) and 2 using GeneChip 10K (Affymetrix, Santa Clara, CA) mapping arrays.

MAIN OUTCOME MEASURES

The prevalence and severity of ocular and kidney involvement and genetic findings.

RESULTS

Eleven affected family members were identified (9 living), all manifesting chronic kidney disease and bilateral chorioretinal pigmentary changes, with or without retinal detachments, but without microcoria or neurodevelopmental deficits, segregating in an autosomal recessive pattern. The causative gene was localized to a 9-Mb region on chromosome 3. Comprehensive gene sequencing revealed a novel LAMB2 variant (c.440A → G; His147R) that was homozygous in the 9 living, affected family members, observed at a frequency of 2.1% in the Old Order Mennonite population, and absent in 91 non-Mennonite controls. The mutation is located in a highly conserved site in the N-terminal domain VI of LAMB2.

CONCLUSIONS

This study describes a novel mutation of LAMB2 and further expands the spectrum of eye and renal manifestations associated with defects in the laminin β-2 chain.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Laminin isoform profiles in salivary glands in Sjögren's syndrome

Five different laminin (LM) alpha, four LM-beta, and three LM-gamma chains form the 15-16 currently known approximately 400-900 kDa heterodimeric LM-monomers, which self-assemble in the lamina lucida of the basement membrane (BM) to a network, connected with nidogens and perlecans with the underlying type IV collagen network. In labial salivary glands (LSG), the structurally organizing/polarizing BM separates the tubuloacinar epithelium from the connective tissue stroma but plays regulatory roles as well. Tissue distribution of LM-alpha, -beta, and -gamma chains is described, and application of the known combinatorial rules allows some conclusions also on the corresponding distribution of the LM-trimers. Currently, known integrin (Int) and non integrin (e.g., dystroglycans and Lutheran blood group antigens) LM-receptors are described. LMs are regulated at transcriptional, translational, and posttranslational levels, together with the regulation of alternative splicing, binding partners (assembly), secretion, and degradation. In LSGs, LM-alpha1, -alpha2, and -alpha4 are only found in the acinar (not ductal) BM, LM-alpha4 also in the periductal/ interstitial stroma. Pattern recognition disclosed irregular expression in the acinar BM, suggesting some dynamic and/or regulatory role. It seems that in a female-dominant autoimmune exocrinopathy, Sjögren's syndrome (SS), LM-alpha1 and -alpha2 are decreased, together with their Int alpha1beta1 and alpha2beta1 receptors. Because LM-111/211-to-Int-alpha1beta1/alpha2beta1 interactions play a crucial role in the transdifferentiation of the intercalated duct progenitors to secretory acinar cells, acinar remodeling is impaired in SS. Disturbed hemidesmosomal Int alpha6beta4/LM-332 interactions in SS may lead to acinar cell anoikis. Interestingly, dehydroepiandrosterone (DHEA) prohormone and its intracrine androgenic dihydrotestosterone (DHT) end product upregulate at least Int alpha1beta1/alpha2beta1, whereas LM-alpha1 is upregulated by outside-in LM-111/211-to-Int-alpha1beta1/alpha2beta1 signaling. It seems that LM alterations precede the lymphocyte infiltration, suggesting that acinar BM-Int pathology, perhaps related to endo- and intracrine sex steroid metabolism, represents an early pathogenic phases in SS.

Mutations in the human laminin beta2 (LAMB2) gene and the associated phenotypic spectrum

Mutations of LAMB2 typically cause autosomal recessive Pierson syndrome, a disorder characterized by congenital nephrotic syndrome, ocular and neurologic abnormalities, but may occasionally be associated with milder or oligosymptomatic disease variants. LAMB2 encodes the basement membrane protein laminin beta2, which is incorporated in specific heterotrimeric laminin isoforms and has an expression pattern corresponding to the pattern of organ manifestations in Pierson syndrome. Herein we review all previously reported and several novel LAMB2 mutations in relation to the associated phenotype in patients from 39 unrelated families. The majority of disease-causing LAMB2 mutations are truncating, consistent with the hypothesis that loss of laminin beta2 function is the molecular basis of Pierson syndrome. Although truncating mutations are distributed across the entire gene, missense mutations are clearly clustered in the N-terminal LN domain, which is important for intermolecular interactions. There is an association of missense mutations and small in frame deletions with a higher mean age at onset of renal disease and with absence of neurologic abnormalities, thus suggesting that at least some of these may represent hypomorphic alleles. Nevertheless, genotype alone does not appear to explain the full range of clinical variability, and therefore hitherto unidentified modifiers are likely to exist.

Computational modeling of laminin N-terminal domains using sparse distance constraints from disulfide bonds and chemical cross-linking

Basement membranes are thin extracellular protein layers, which separate endothelial and epithelial cells from the underlying connecting tissue. The main noncollagenous components of basement membranes are laminins, trimeric glycoproteins, which form polymeric networks by interactions of their N-terminal (LN) domains; however, no high-resolution structure of laminin LN domains exists so far. To construct models for laminin β(1) and γ(1) LN domains, 14 potentially suited template structures were determined using fold recognition methods. For each target/template-combination comparative models were created with Rosetta. Final models were selected based on their agreement with experimentally obtained distance constraints from natural cross-links, that is, disulfide bonds as well as chemical cross-links obtained from reactions with two amine-reactive cross-linkers. We predict that laminin β(1) and γ(1) LN domains share the galactose-binding domain-like fold.

Nerve invasion distance is dependent on laminin gamma2 in tumors of pancreatic cancer

The distance of nerve invasion is an important prognostic factor in pancreatic cancer. The extracellular matrix (ECM) of nerve, mainly composed of laminin, collagen IV and anchoring fibrils, might affect nerve invasion. However, this relationship has not been demonstrated. Our study aimed at discovering the promoting factor of nerve invasion within the tumoral ECM. An animal model was established to evaluate the distance of nerve invasion in murine sciatic nerves by intraneural injection of 6 human pancreatic cancer cell lines. mRNA expression of laminins and anchoring fibrils was compared to the distance of nerve invasion for each cancer cell line. A target molecule provided the strong association between mRNA expression and the distance of nerve invasion. To evaluate the role of a target molecule in nerve invasion, protein expression and function were examined using an animal model and surgical cases. Cancer cells with high laminin gamma2 mRNA and protein expression in their basement membranes were associated with long nerve invasion. Knockdown of laminin gamma2 in cancer cells significantly shortened nerve invasion in the animal model. In 75 patients with pancreatic cancer, a large distance of nerve invasion was associated with high expression levels of laminin gamma2 mRNA and basement membranous deposition of laminin gamma2 protein. Our results indicate that laminin gamma2 plays an important role in nerve invasion. The measurement of the nerve invasion distance in our mouse nerve invasion model is useful for evaluating the molecular mechanisms of nerve invasion.

Laminin deposition in the extracellular matrix: a complex picture emerges

Laminins are structural components of basement membranes. In addition, they are key extracellular-matrix regulators of cell adhesion, migration, differentiation and proliferation. This Commentary focuses on a relatively understudied aspect of laminin biology: how is laminin deposited into the extracellular matrix? This topic has fascinated researchers for some time, particularly considering the diversity of patterns of laminin that can be visualized in the matrix of cultured cells. We discuss current ideas of how laminin matrices are assembled, the role of matrix receptors in this process and how laminin-associated proteins modulate matrix deposition. We speculate on the role of signaling pathways that are involved in laminin-matrix deposition and on how laminin patterns might play an important role in specifying cell behaviors, especially directed migration. We conclude with a description of new developments in the way that laminin deposition is being studied, including the use of tagged laminin subunits that should allow the visualization of laminin-matrix deposition and assembly by living cells.

Extracellular matrix in pancreatic islets: relevance to scaffold design and transplantation

Intrahepatic islet transplantation provides a potentially more benign alternative to pancreatic transplantation. However, islet transplants are associated with limited engraftment potential. This inefficiency is likely at least partially attributable to the isolation process, which removes islets from their native environment. Isolation not only disrupts the internal vascularization and innervation of islets, but also fundamentally changes interactions between islet cells and macromolecules of the extracellular matrix (ECM). Signaling interactions between islet cells and ECM are known to regulate multiple aspects of islet physiology, including survival, proliferation, and insulin secretion. Although it is highly likely that disruptions to these interactions during isolation significantly affect transplant outcomes, the true implications of these conditions are not well understood. The following article reviews current understandings and uncertainties in islet-ECM interactions and explains their potential impact on posttransplant engraftment. Topics covered include matrix and receptor compositions in native islets, effects of isolation and culture on islet-ECM interactions, and potential for postisolation restoration of islet-ECM interactions. Greater understanding in these areas may help to reduce isolation and transplantation stresses and improve islet engraftment.

Neuroprotective effects of laminin and its KDI domain

Successful treatment of neurodegenerative diseases and CNS trauma are the most intractable problems in modern medicine. Numerous reports have shown the strong role that laminins have on the survival, regeneration and development of various types of cells, including neural cells. It would be desirable to take advantage of laminin activities for therapeutic purposes. However, there are at least ten laminin variants and the trimeric molecules are of the order of 800,000 molecular weight. Furthermore, human laminins are not available in quantity. Therefore, we and others have taken the approach of determining which domains of the laminin molecules are functional in the CNS, and whether short peptides from these regions exhibit biological activities with the intent of testing their potential for therapeutic use. Understanding the role of laminins and their small biologically active peptide domains, such as the KDI (lysine–aspartic acid–isoleucine) peptide from γ1 laminin, in neuronal development, CNS trauma (spinal cord injury and stroke) and neurodegenerative disorders (amyotrophic lateral sclerosis, Alzheimer’s disease and Parkinson’s disease) may help to develop clinically applicable methods to treat the presently untreatable CNS diseases and trauma even in the near future.

Genetics of nephrotic syndrome: new insights into molecules acting at the glomerular filtration barrier

Nephrotic syndrome is caused by increased permeability of the glomerular filtration barrier for macromolecules. The identification of mutations of various podocyte-expressed proteins as causes of familial nephrotic syndrome has significantly contributed to shedding light into the molecular pathogenesis of nephrotic proteinuria and into the physiology of the glomerular sieve. More recent findings have changed our conception of the glomerular filtration barrier from a relatively static structure to a highly dynamic one. Both the multiprotein slit diaphragm complex around nephrin and the integrin receptor complex that mediates binding of the podocyte to the glomerular basement membrane, may translate outside-inside signaling and lead to podocyte actin cytoskeleton rearrangement. This may enable the podocyte network to adapt to environmental changes and respond to injury. Disturbance in these processes may not only be involved in the pathogenesis of hereditary nephrotic syndrome but also in that of more common acquired proteinuric diseases. Elucidation of the molecular mechanisms involved will possibly open the way to new therapeutic approaches.