Molecular Basis of Laminin-Integrin Interactions

Polymerizing Laminins in Development, Health and Disease

Polymerizing laminins are multi-domain basement membrane (BM) glycoproteins that self-assemble into cell-anchored planar lattices to establish the initial BM scaffold. Nidogens, collagen-IV and proteoglycans then bind to the scaffold at different domain loci to create a mature BM. The LN domains of adjacent laminins bind to each other to form a polymer node, while the LG domains attach to cytoskeletal-anchoring integrins and dystroglycan, as well as to sulfatides and heparan sulfates. The polymer node, the repeating unit of the polymer scaffold, is organized into a near-symmetrical triskelion. The structure, recently solved by cryo-electron microscopy in combination with AlphaFold2 modelling and biochemical studies, reveals how the LN surface residues interact with each other and how mutations cause failures of self-assembly in an emerging group of diseases, the LN-lamininopathies, that include LAMA2-related dystrophy and Pierson syndrome.

Periapical lesion-derived decellularized extracellular matrix as a potential solution for regenerative endodontics

Pulp regeneration remains a crucial target in the preservation of natural dentition. Using decellularized extracellular matrix is an appropriate approach to mimic natural microenvironment and facilitate tissue regeneration. In this study, we attempted to obtain decellularized extracellular matrix from periapical lesion (PL-dECM) and evaluate its bioactive effects. The decellularization process yielded translucent and viscous PL-dECM, meeting the standard requirements for decellularization efficiency. Proteomic sequencing revealed that the PL-dECM retained essential extracellular matrix components and numerous bioactive factors. The PL-dECM conditioned medium could enhance the proliferation and migration ability of periapical lesion-derived stem cells (PLDSCs) in a dose-dependent manner. Culturing PLDSCs on PL-dECM slices improved odontogenic/angiogenic ability compared to the type I collagen group. In vivo, the PL-dECM demonstrated a sustained supportive effect on PLDSCs and promoted odontogenic/angiogenic differentiation. Both in vitro and in vivo studies illustrated that PL-dECM served as an effective scaffold for pulp tissue engineering, providing valuable insights into PLDSCs differentiation. These findings pave avenues for the clinical application of dECM's in situ transplantation for regenerative endodontics.

The occurrence and development of induced pluripotent stem cells

The ectopic expression of four transcription factors, Oct3/4, Sox2, Klf4, and c-Myc (OSKM), known as "Yamanaka factors," can reprogram or stimulate the production of induced pluripotent stem cells (iPSCs). Although OSKM is still the gold standard, there are multiple ways to reprogram cells into iPSCs. In recent years, significant progress has been made in improving the efficiency of this technology. Ten years after the first report was published, human pluripotent stem cells have gradually been applied in clinical settings, including disease modeling, cell therapy, new drug development, and cell derivation. Here, we provide a review of the discovery of iPSCs and their applications in disease and development.

CHRFAM7A diversifies human immune adaption through Ca2+ signalling and actin cytoskeleton reorganization

BACKGROUND

Human restricted genes contribute to human specific traits in the immune system. CHRFAM7A, a uniquely human fusion gene, is a negative regulator of the α7 nicotinic acetylcholine receptor (α7 nAChR), the highest Ca2+ conductor of the ACh receptors implicated in innate immunity. Understanding the mechanism of how CHRFAM7A affects the immune system remains unexplored.

METHODS

Two model systems are used, human induced pluripotent stem cells (iPSC) and human primary monocytes, to characterize α7 nAChR function, Ca2+ dynamics and decoders to elucidate the pathway from receptor to phenotype.

FINDINGS

CHRFAM7A/α7 nAChR is identified as a hypomorphic receptor with mitigated Ca2+ influx and prolonged channel closed state. This shifts the Ca2+ reservoir from the extracellular space to the endoplasmic reticulum (ER) leading to Ca2+ dynamic changes. Ca2+ decoder small GTPase Rac1 is then activated, reorganizing the actin cytoskeleton. Observed actin mediated phenotypes include cellular adhesion, motility, phagocytosis and tissue mechanosensation.

INTERPRETATION

CHRFAM7A introduces an additional, human specific, layer to Ca2+ regulation leading to an innate immune gain of function. Through the actin cytoskeleton it drives adaptation to the mechanical properties of the tissue environment leading to an ability to invade previously immune restricted niches. Human genetic diversity predicts profound translational significance as its understanding builds the foundation for successful treatments for infectious diseases, sepsis, and cancer metastasis.

FUNDING

This work is supported in part by the Community Foundation for Greater Buffalo (Kinga Szigeti) and in part by NIH grant R01HL163168 (Yongho Bae).

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.

The relevance of the hematopoietic niche for therapy resistance in acute myeloid leukemia

The expansion of acute myeloid leukemia (AML) blasts not only suppresses normal hematopoiesis, but also alters the microenvironment. The interplay of different components of the bone marrow gives rise to altered metabolic states and activates signaling pathways which lead to resistance and impede effective therapy. Therefore, the underlying processes and mechanisms represent attractive therapeutic leverage points for overcoming therapy resistance in AML. Here, we briefly discuss resistance mechanisms based on cell interactions and secreted soluble factors in the hematopoietic niche and provide an overview of niche-related therapeutic targets currently undergoing preclinical and clinical investigation which may help improve the outcome in AML therapy.

"Small Hepatocytes" in the Liver

Mature hepatocytes (MHs) in an adult rodent liver are categorized into the following three subpopulations based on their proliferative capability: type I cells (MH-I), which are committed progenitor cells that possess a high growth capability and basal hepatocytic functions; type II cells (MH-II), which possess a limited proliferative capability; and type III cells (MH-III), which lose the ability to divide (replicative senescence) and reach the final differentiated state. These subpopulations may explain the liver's development and growth after birth. Generally, small-sized hepatocytes emerge in mammal livers. The cells are characterized by being morphologically identical to hepatocytes except for their size, which is substantially smaller than that of ordinary MHs. We initially discovered small hepatocytes (SHs) in the primary culture of rat hepatocytes. We believe that SHs are derived from MH-I and play a role as hepatocytic progenitors to supply MHs. The population of MH-I (SHs) is distributed in the whole lobules, a part of which possesses a self-renewal capability, and decreases with age. Conversely, injured livers of experimental models and clinical cases showed the emergence of SHs. Studies demonstrate the involvement of SHs in liver regeneration. SHs that appeared in the injured livers are not a pure population but a mixture of two distinct origins, MH-derived and hepatic-stem-cell-derived cells. The predominant cell-derived SHs depend on the proliferative capability of the remaining MHs after the injury. This review will focus on the SHs that appeared in the liver and discuss the significance of SHs in liver regeneration.

Defined extracellular matrix compositions support stiffness-insensitive cell spreading and adhesion signaling

Integrin-dependent adhesion to the extracellular matrix (ECM) mediates mechanosensing and signaling in response to altered microenvironmental conditions. In order to provide tissue- and organ-specific cues, the ECM is composed of many different proteins that temper the mechanical properties and provide the necessary structural diversity. Despite most human tissues being soft, the prevailing view from predominantly in vitro studies is that increased stiffness triggers effective cell spreading and activation of mechanosensitive signaling pathways. To address the functional coupling of ECM composition and matrix rigidity on compliant substrates, we developed a matrix spot array system to screen cell phenotypes against different ECM mixtures on defined substrate stiffnesses at high resolution. We applied this system to both cancer and normal cells and surprisingly identified ECM mixtures that support stiffness-insensitive cell spreading on soft substrates. Employing the motor-clutch model to simulate cell adhesion on biochemically distinct soft substrates, with varying numbers of available ECM-integrin-cytoskeleton (clutch) connections, we identified conditions in which spreading would be supported on soft matrices. Combining simulations and experiments, we show that cell spreading on soft is supported by increased clutch engagement on specific ECM mixtures and even augmented by the partial inhibition of actomyosin contractility. Thus, "stiff-like" spreading on soft is determined by a balance of a cell's contractile and adhesive machinery. This provides a fundamental perspective for in vitro mechanobiology studies, identifying a mechanism through which cells spread, function, and signal effectively on soft substrates.

Protein ligand and nanotopography separately drive the phenotype of mouse embryonic stem cells

Biochemical and biomechanical signals regulate stem cell function in the niche environments in vivo. Current in vitro culture of mouse embryonic stem cells (mESC) uses laminin (LN-511) to provide mimetic biochemical signaling (LN-521 for human systems) to maintain stemness. Alternative approaches propose topographical cues to provide biomechanical cues, however combined biochemical and topographic cues may better mimic the in vivo environment, but are largely unexplored for in vitro stem cell expansion. In this study, we directly compare in vitro signals from LN-511 and/or topographic cues to maintain stemness, using systematically-varied submicron pillar patterns or flat surfaces with or without preadsorbed LN-511. The adhesion of cells, colony formation, expression of the pluripotency marker,octamer-binding transcription factor 4 (Oct4), and transcriptome profiling were characterized. We observed that either biochemical or topographic signals could maintain stemness of mESCs in feeder-free conditions, indicated by high-level Oct4 and gene profiling by RNAseq. The combination of LN-511 with nanotopography reduced colony growth, while maintaining stemness markers, shifted the cellular phenotype indicating that the integration of biochemical and topographic signals is antagonistic. Overall, significantly faster (up to 2.5 times) colony growth was observed at nanotopographies without LN-511, suggesting for improved ESC expansion.

The Glycosaminoglycan Side Chains and Modular Core Proteins of Heparan Sulphate Proteoglycans and the Varied Ways They Provide Tissue Protection by Regulating Physiological Processes and Cellular Behaviour

This review examines the roles of HS-proteoglycans (HS-PGs) in general, and, in particular, perlecan and syndecan as representative examples and their interactive ligands, which regulate physiological processes and cellular behavior in health and disease. HS-PGs are essential for the functional properties of tissues both in development and in the extracellular matrix (ECM) remodeling that occurs in response to trauma or disease. HS-PGs interact with a biodiverse range of chemokines, chemokine receptors, protease inhibitors, and growth factors in immune regulation, inflammation, ECM stabilization, and tissue protection. Some cell regulatory proteoglycan receptors are dually modified hybrid HS/CS proteoglycans (betaglycan, CD47). Neurexins provide synaptic stabilization, plasticity, and specificity of interaction, promoting neurotransduction, neurogenesis, and differentiation. Ternary complexes of glypican-1 and Robbo-Slit neuroregulatory proteins direct axonogenesis and neural network formation. Specific neurexin-neuroligin complexes stabilize synaptic interactions and neural activity. Disruption in these interactions leads to neurological deficits in disorders of functional cognitive decline. Interactions with HS-PGs also promote or inhibit tumor development. Thus, HS-PGs have complex and diverse regulatory roles in the physiological processes that regulate cellular behavior and the functional properties of normal and pathological tissues. Specialized HS-PGs, such as the neurexins, pikachurin, and Eyes-shut, provide synaptic stabilization and specificity of neural transduction and also stabilize the axenome primary cilium of phototoreceptors and ribbon synapse interactions with bipolar neurons of retinal neural networks, which are essential in ocular vision. Pikachurin and Eyes-Shut interactions with an α-dystroglycan stabilize the photoreceptor synapse. Novel regulatory roles for HS-PGs controlling cell behavior and tissue function are expected to continue to be uncovered in this fascinating class of proteoglycan.

Laminin fragments conjugated with perlecan's growth factor-binding domain differentiate human induced pluripotent stem cells into skin-derived precursor cells

Deriving stem cells to regenerate full-thickness human skin is important for treating skin disorders without invasive surgical procedures. Our previous protocol to differentiate human induced pluripotent stem cells (iPSCs) into skin-derived precursor cells (SKPs) as a source of dermal stem cells employs mouse fibroblasts as feeder cells and is therefore unsuitable for clinical use. Herein, we report a feeder-free method for differentiating iPSCs into SKPs by customising culture substrates. We immunohistochemically screened for laminins expressed in dermal papillae (DP) and explored the conditions for inducing the differentiation of iPSCs into SKPs on recombinant laminin E8 (LM-E8) fragments with or without conjugation to domain I of perlecan (PDI), which binds to growth factors through heparan sulphate chains. Several LM-E8 fragments, including those of LM111, 121, 332, 421, 511, and 521, supported iPSC differentiation into SKPs without PDI conjugation. However, the SKP yield was significantly enhanced on PDI-conjugated LM-E8 fragments. SKPs induced on PDI-conjugated LM111-E8 fragments retained the gene expression patterns characteristic of SKPs, as well as the ability to differentiate into adipocytes, osteocytes, and Schwann cells. Thus, PDI-conjugated LM-E8 fragments are promising agents for inducing iPSC differentiation into SKPs in clinical settings.

Human CD34+ hematopoietic stem cell hierarchy: how far are we with its delineation at the most primitive level?

The ability to isolate and characterize different hematopoietic stem cell (HSC) or progenitor cell populations opens avenues to understand how hematopoiesis is regulated during development, homeostasis, and regeneration as well as in age-related conditions such as clonal hematopoiesis and leukemogenesis. Significant progress has been made in the past few decades in determining the composition of the cell types that exist in this system, but the most significant advances have come from mouse studies. However, recent breakthroughs have made significant strides that have enhanced the resolution of the human primitive hematopoietic compartment. Therefore, we aim to review this subject not only from a historical perspective but also to discuss the progress made in the characterization of the human postnatal CD34+ HSC-enriched populations. This approach will enable us to shed light on the potential future translational applicability of human HSCs.

Mimicking the neural stem cell niche: An engineer’s view of cell: material interactions

Neural stem cells have attracted attention in recent years to treat neurodegeneration. There are two neurogenic regions in the brain where neural stem cells reside, one of which is called the subventricular zone (SVZ). The SVZ niche is a complicated microenvironment providing cues to regulate self-renewal and differentiation while maintaining the neural stem cell’s pool. Many scientists have spent years understanding the cellular and structural characteristics of the SVZ niche, both in homeostasis and pathological conditions. On the other hand, engineers focus primarily on designing platforms using the knowledge they acquire to understand the effect of individual factors on neural stem cell fate decisions. This review provides a general overview of what we know about the components of the SVZ niche, including the residing cells, extracellular matrix (ECM), growth factors, their interactions, and SVZ niche changes during aging and neurodegenerative diseases. Furthermore, an overview will be given on the biomaterials used to mimic neurogenic niche microenvironments and the design considerations applied to add bioactivity while meeting the structural requirements. Finally, it will discuss the potential gaps in mimicking the microenvironment.

Targeting integrin pathways: mechanisms and advances in therapy

Integrins are considered the main cell-adhesion transmembrane receptors that play multifaceted roles as extracellular matrix (ECM)-cytoskeletal linkers and transducers in biochemical and mechanical signals between cells and their environment in a wide range of states in health and diseases. Integrin functions are dependable on a delicate balance between active and inactive status via multiple mechanisms, including protein-protein interactions, conformational changes, and trafficking. Due to their exposure on the cell surface and sensitivity to the molecular blockade, integrins have been investigated as pharmacological targets for nearly 40 years, but given the complexity of integrins and sometimes opposite characteristics, targeting integrin therapeutics has been a challenge. To date, only seven drugs targeting integrins have been successfully marketed, including abciximab, eptifibatide, tirofiban, natalizumab, vedolizumab, lifitegrast, and carotegrast. Currently, there are approximately 90 kinds of integrin-based therapeutic drugs or imaging agents in clinical studies, including small molecules, antibodies, synthetic mimic peptides, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, imaging agents, etc. A serious lesson from past integrin drug discovery and research efforts is that successes rely on both a deep understanding of integrin-regulatory mechanisms and unmet clinical needs. Herein, we provide a systematic and complete review of all integrin family members and integrin-mediated downstream signal transduction to highlight ongoing efforts to develop new therapies/diagnoses from bench to clinic. In addition, we further discuss the trend of drug development, how to improve the success rate of clinical trials targeting integrin therapies, and the key points for clinical research, basic research, and translational research.

The burden of diabetes on the soft tissue seal surrounding the dental implants

Soft tissue seal around implant prostheses is considered the primary barrier against adverse external stimuli and is a critical factor in maintaining dental implants' stability. Soft tissue seal is formed mainly by the adhesion of epithelial tissue and fibrous connective tissue to the transmembrane portion of the implant. Type 2 diabetes mellitus (T2DM) is one of the risk factors for peri-implant inflammation, and peri-implant disease may be triggered by dysfunction of the soft tissue barrier around dental implants. This is increasingly considered a promising target for disease treatment and management. However, many studies have demonstrated that pathogenic bacterial infestation, gingival immune inflammation, overactive matrix metalloproteinases (MMPs), impaired wound healing processes and excessive oxidative stress may trigger poor peri-implant soft tissue sealing, which may be more severe in the T2DM state. This article reviews the structure of peri-implant soft tissue seal, peri-implant disease and treatment, and moderating mechanisms of impaired soft tissue seal around implants due to T2DM to inform the development of treatment strategies for dental implants in patients with dental defects.

Junctional epidermolysis bullosa: genotype-phenotype correlations

Junctional epidermolysis bullosa most commonly results from mutations in theLAMA3, LAMB3, LAMC2, COL17A1, ITGA6 and ITGB4genes. Junctional epidermolysis bullosa is characterized by clinical heterogeneity. To date, scientific findings allow to evaluate correlations between the severity of clinical manifestations and genetic defects underlying in the development of the disease. A systematic literature search was performed using PubMed and RSCI, and keywords including junctional epidermolysis bullosa, laminin 332, collagen XVII, 64 integrin. The review includes description of clinical findings of junctional epidermolysis bullosa, mutation location and types, its impact on protein production and functions. To evaluate the impact of gene mutation on protein functions, this review explores the structure and functions of lamina lucida components, including laminin 332, collagen XVII and 64 integrin, which are frequently associated with the development of junctional epidermolysis bullosa. The correlation between severe types of junctional epidermolysis bullosa and mutations resulting in premature stop codon generation and complete absence of protein expression has been described. Although, genotype-phenotype correlations should be analyzed carefully due to mechanisms which enable to improve protein expression.

Laminin-bound integrin α6β4 promotes non-small cell lung cancer progression via the activation of YAP/TAZ signaling pathway

Laminin is an extracellular matrix multidomain trimeric glycoprotein, that has a potential role in tumor progression. Here, we studied the effects of non-small cell lung cancer (NSCLC) cells interaction on laminin and explored the underlying mechanism of laminin associated NSCLC progression. Culture of A549 and NCI-1299 cells on 2D collagen gels (containing laminin) significantly promoted the proliferative and tumorigenic characteristics, as well as cell invasion of tumor cells in vitro. Consistently, comparing the clinical NSCLC tumor tissues, a poor overall survival was observed in patients with high laminin expression. Mechanistically, the expression of integrin α6β4 was required for the pro-tumor effects of laminin. Meanwhile, we showed that the downstream signaling of integrin α6β4, involved the focal adhesion kinase (FAK)/Yes-Associated Protein (YAP)/TAZ signaling pathway. The activation of FAK/YAP/TAZ signaling pathway induced by laminin was validated in tumor tissues from NSCLC patients. Suppression of integrin α6β4/FAK/YAP/TAZ signaling pathway efficiently suppressed the laminin-induced tumor growth, and strengthened the anticancer effects of chemotherapy, describing a novel target for NSCLC treatment.

The role of the dystrophin glycoprotein complex in muscle cell mechanotransduction

Dystrophin is the central protein of the dystrophin-glycoprotein complex (DGC) in skeletal and heart muscle cells. Dystrophin connects the actin cytoskeleton to the extracellular matrix (ECM). Severing the link between the ECM and the intracellular cytoskeleton has a devastating impact on the homeostasis of skeletal muscle cells, leading to a range of muscular dystrophies. In addition, the loss of a functional DGC leads to progressive dilated cardiomyopathy and premature death. Dystrophin functions as a molecular spring and the DGC plays a critical role in maintaining the integrity of the sarcolemma. Additionally, evidence is accumulating, linking the DGC to mechanosignalling, albeit this role is still less understood. This review article aims at providing an up-to-date perspective on the DGC and its role in mechanotransduction. We first discuss the intricate relationship between muscle cell mechanics and function, before examining the recent research for a role of the dystrophin glycoprotein complex in mechanotransduction and maintaining the biomechanical integrity of muscle cells. Finally, we review the current literature to map out how DGC signalling intersects with mechanical signalling pathways to highlight potential future points of intervention, especially with a focus on cardiomyopathies.

A review of the function of the Dystrophic Glycoprotein Complex (DGC) in mechanosignaling provides an overview of the various components of DGC and potential mechanopathogenic mechanisms, particularly as they relate to muscular dystrophy.

Semi-three-dimensional cultures using laminin 221 as a coating material for human induced pluripotent stem cells

It was previously believed that human induced pluripotent stem cells (hiPSCs) did not show adhesion to the coating material Laminin 221, which is known to have specific affinity for cardiomyocytes. In this study, we report that human mononuclear cell-derived hiPSCs, established with Sendai virus vector, form peninsular-like colonies rather than embryonic stem cell-like colonies; these peninsular-like colonies can be passaged more than 10 times after establishment. Additionally, initialization-deficient cells with residual Sendai virus vector adhered to the coating material Laminin 511 but not to Laminin 221. Therefore, the expression of undifferentiated markers tended to be higher in hiPSCs established on Laminin 221 than on Laminin 511. On Laminin 221, hiPSCs15M66 showed a semi-floating colony morphology. The expression of various markers of cell polarity was significantly lower in hiPSCs cultured on Laminin 221 than in hiPSCs cultured on Laminin 511. Furthermore, 201B7 and 15M66 hiPSCs showed 3D cardiomyocyte differentiation on Laminin 221. Thus, the coating material Laminin 221 provides semi-floating culture conditions for the establishment, culture and induced differentiation of hiPSCs.

The Role of ECM Remodeling, EMT, and Adhesion Molecules in Cancerous Neural Invasion: Changing Perspectives

Perineural invasion (PNI) refers to the cancerous invasion of nerves. It provides an alternative route for metastatic invasion and can exist independently in the absence of lymphatic or vascular invasion. It is a prominent characteristic of specific aggressive malignancies where it correlates with poor prognosis. The clinical significance of PNI is widely recognized despite a lack of understanding of the molecular mechanisms underlying its pathogenesis. The interaction between the nerve and the cancer cells is the most pivotal PNI step which is mediated by the activation or inhibition of multiple signaling pathways that include chemokines, interleukins, nerve growth factors, and matrix metalloproteinases, to name a few. The nerve-cancer cell interaction brings about specific changes in the perineural niche, which not only affects the regular nerve functions, but also enhances the migratory, invasive, and adherent properties of the tumor cells. This review aims to elucidate the vital role of adhesion molecules, extracellular matrix, and epithelial-mesenchymal proteins that promote PNI, which may serve as therapeutic targets in the future.

Novel adult cortical neuron processing and screening method illustrates sex- and age-dependent effects of pharmaceutical compounds

Neurodegenerative diseases and neurotraumatic injuries are typically age-associated disorders that can reduce neuron survival, neurite outgrowth, and synaptic plasticity leading to loss of cognitive capacity, executive function, and motor control. In pursuit of reducing the loss of said neurological functions, novel compounds are sought that promote neuron viability, neuritogenesis, and/or synaptic plasticity. Current high content in vitro screenings typically use cells that are iPSC-derived, embryonic, or originate from post-natal tissues; however, most patients suffering from neurodegenerative diseases and neurotrauma are of middle-age and older. The chasm in maturity between the neurons used in drug screens and those in a target population is a barrier for translational success of in vitro results. It has been historically challenging to culture adult neurons let alone conduct screenings; therefore, age-appropriate drug screenings have previously not been plausible. We have modified Miltenyi’s protocol to increase neuronal yield, neuron purity, and neural viability at a reduced cost to expand our capacity to screen compounds directly in primary adult neurons. To our knowledge, we developed the first morphology-based screening system using adult cortical neurons and the first to incorporate age and sex as biological variables in a screen using adult cortical neurons. By using primary adult cortical neurons from mice that were 4 to 48 weeks old for screening pharmaceutical agents, we have demonstrated age- and sex-dependent effects on neuritogenesis and neuron survival in vitro. Utilizing age- and sex-appropriate in vitro models to find novel compounds increasing neuron survival and neurite outgrowth, made possible by our modified adult neuron processing method, will greatly increase the relevance of in vitro screening for finding neuroprotective compounds.

Laminin-221-derived recombinant fragment facilitates isolation of cultured skeletal myoblasts

Introduction

Laminin is a major component of the basement membrane, containing multiple domains that bind integrin, collagen, nidogen, dystroglycan, and heparan sulfate. Laminin-221, expressed in skeletal and cardiac muscles, has strong affinity for the cell-surface receptor, integrin α7X2β1. The E8 domain of laminin-221, which is essential for cell integrin binding, is commercially available as a purified recombinant protein fragment. In this study, recombinant E8 fragment was used to purify primary rodent myoblasts. We established a facile and inexpensive method for primary myoblast culture exploiting the high affinity binding of integrin α7X2β1 to laminin-221.

Methods

Total cell populations from dissociated muscle tissue were enzymatically digested and seeded onto laminin-221 E8 fragment-coated dishes. The culture medium containing non-adherent floating cells was removed after 2-hour culture at 37 °C. The adherent cells were subjected to immunofluorescence staining of desmin, differentiation experiments, and gene expression analysis.

Results

The cells obtained were 70.3 ± 5.49% (n = 5) desmin positive in mouse and 67.7 ± 1.65% (n = 3) in rat. Immunofluorescent staining and gene expression analyses of cultured cells showed phenotypic traits of myoblasts.

Conclusion

This study reports a novel facile method for primary culture of myoblasts obtained from mouse and rat skeletal muscle by exploiting the high affinity of integrin α7X2β1 to laminin-221.

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Myoblasts are muscle progenitor cells that differentiate into skeletal muscle.

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Various methods have been reported to isolate myoblasts, such as FACS and MACS.

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Integrin α7X2, predominantly expressed in myocytes and cardiomyocytes, binds laminin-221 with high affinity.

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We established a novel method for primary culture of myoblasts by utilizing the high affinity of integrin α7X2β1 to laminin-221.

Laminin-integrin a6b4 interaction activates notch signaling to facilitate bladder cancer development

Background

Laminins are high-molecular weight (400 ~ 900 kDa) proteins in extracellular matrix, which serve as major component of the basal lamina, and play a crucial role in promoting tumor cell migration. This study aimed at characterizing the role of laminin in promoting cancer development, and elucidating the mechanism of tumor progression driven by laminin-Notch signaling in bladder cancer.

Methods

2D collagen/laminin culture system was established and CCK-8/transwell assay was conducted to evaluate the proliferation/migration ability of Biu-87 and MB49 cells cultured on 2D gels. Activation of integrins-Notch1 signaling was determined by western blotting. Orthotopic bladder cancer mice model was established to assess the therapeutic effects of Notch inhibitor.

Results

Our study demonstrated that extracellular laminin can trigger tumor cell proliferation/migration through integrin α6β4/Notch1 signaling in bladder cancer. Inhibition of Telomere repeat-binding factor 3 (TRB3)/Jagged Canonical Notch Ligand 1 (JAG1) signaling suppressed Notch signals activation induced by laminin-integrin axis. In MB49 orthotopic bladder cancer mice model, Notch inhibitor SAHM1 efficiently improved tumor suppressive effects of chemotherapy and prolonged survival time of tumor-bearing mice.

Conclusion

In conclusion, we show that, in bladder cancer, extracellular laminin induced the activation of Notch pathway through integrin α6β4/TRB3/JAG3, and disclosed a novel role of laminin in bladder cancer cells proliferation or migration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09645-7.

Distinct contributions of ECM proteins to basement membrane mechanical properties in Drosophila

The basement membrane is a specialized extracellular matrix (ECM) that is crucial for the development of epithelial tissues and organs. In Drosophila, the mechanical properties of the basement membrane play an important role in the proper elongation of the developing egg chamber; however, the molecular mechanisms contributing to basement membrane mechanical properties are not fully understood. Here, we systematically analyze the contributions of individual ECM components towards the molecular composition and mechanical properties of the basement membrane underlying the follicle epithelium of Drosophila egg chambers. We find that the Laminin and Collagen IV networks largely persist in the absence of the other components. Moreover, we show that Perlecan and Collagen IV, but not Laminin or Nidogen, contribute greatly towards egg chamber elongation. Similarly, Perlecan and Collagen, but not Laminin or Nidogen, contribute towards the resistance of egg chambers against osmotic stress. Finally, using atomic force microscopy we show that basement membrane stiffness mainly depends on Collagen IV. Our analysis reveals how single ECM components contribute to the mechanical properties of the basement membrane controlling tissue and organ shape.

Biobased Elastomer Nanofibers Guide Light-Controlled Human-iPSC-Derived Skeletal Myofibers

Generating skeletal muscle tissue that mimics the cellular alignment, maturation, and function of native skeletal muscle is an ongoing challenge in disease modeling and regenerative therapies. Skeletal muscle cultures require extracellular guidance and mechanical support to stabilize contractile myofibers. Existing microfabrication-based solutions are limited by complex fabrication steps, low throughput, and challenges in measuring dynamic contractile function. Here, the synthesis and characterization of a new biobased nanohybrid elastomer, which is electrospun into aligned nanofiber sheets to mimic the skeletal muscle extracellular matrix, is presented. The polymer exhibits remarkable hyperelasticity well-matched to that of native skeletal muscle (≈11-50 kPa), with ultimate strain ≈1000%, and elastic modulus ≈25 kPa. Uniaxially aligned nanofibers guide myoblast alignment, enhance sarcomere formation, and promote a ≈32% increase in myotube fusion and ≈50% increase in myofiber maturation. The elastomer nanofibers stabilize optogenetically controlled human induced pluripotent stem cell derived skeletal myofibers. When activated by blue light, the myofiber-nanofiber hybrid constructs maintain a significantly higher (>200%) contraction velocity and specific force (>280%) compared to conventional culture methods. The engineered myofibers exhibit a power density of ≈35 W m-3 . This system is a promising new skeletal muscle tissue model for applications in muscular disease modeling, drug discovery, and muscle regeneration.

Superoxide Dismutase-3 Downregulates Laminin α5 Expression in Tumor Endothelial Cells via the Inhibition of Nuclear Factor Kappa B Signaling

The balance between laminin isoforms containing the α5 or the α4 chain in the endothelial basement membrane determines the site of leukocyte diapedesis under inflammatory conditions. Extracellular superoxide dismutase (SOD3) induces laminin α4 expression in tumor blood vessels, which is associated with enhanced intratumor T cell infiltration in primary human cancers. We show now that SOD3 overexpression in neoplastic and endothelial cells (ECs) reduces laminin α5 in tumor blood vessels. SOD3 represses the laminin α5 gene (LAMA5), but LAMA5 expression is not changed in SOD1-overexpressing cells. Transcriptomic analyses revealed SOD3 overexpression to change the transcription of 1682 genes in ECs, with the canonical and non-canonical NF-κB pathways as the major SOD3 targets. Indeed, SOD3 reduced the transcription of well-known NF-κB target genes as well as NF-κB-driven promoter activity in ECs stimulated with tumor necrosis factor (TNF)-α, an NF-κB signaling inducer. SOD3 inhibited the phosphorylation and degradation of IκBα (nuclear factor of the kappa light polypeptide gene enhancer in B-cells inhibitor alpha), an NF-κB inhibitor. Finally, TNF-α was found to be a transcriptional activator of LAMA5 but not of LAMA4; LAMA5 induction was prevented by SOD3. In conclusion, SOD3 is a major regulator of laminin balance in the basement membrane of tumor ECs, with potential implications for immune cell infiltration into tumors.

Laminin Triggers Neutrophil Extracellular Traps (NETs) and Modulates NET Release Induced by Leishmania amazonensis

Neutrophils are recruited from the blood and transmigrate through the endothelium to reach tissues, where they are prone to respond through different mechanisms, including the release of neutrophil extracellular traps (NETs). These responses occur in close contact with proteins from the basement membrane and extracellular matrix, where laminins are abundant. Thus, we investigated the interactions between neutrophils and different laminin (LM) isoforms and analyzed the induction of NETs. We showed that neutrophils stimulated with LM isoforms 111, 211, 332, 411, 421, and 511 released NETs. The same occurred when neutrophils interacted with polymerized LMs 111, 411, and 511. LM-induced NETs were partially inhibited by pretreatment of neutrophils with an anti-α6 integrin antibody. Furthermore, NETs triggered by laminins were dependent on elastase and peptidylarginine deiminase (PAD)-4, enzymes that participate in chromatin decondensation. We also found that LMs 411 and LM 511 potentiated the NET release promoted by promastigotes of the protozoan parasite Leishmania, and that NETs stimulated by LMs alone display leishmanicidal activity. The ability of LM to induce NET release may have potential implications for the course of inflammation or infection.

High-Fat-Diet-Induced Extracellular Matrix Deposition Regulates Integrin - FAK Signals in Adipose Tissue to Promote Obesity

SCOPE

High-fat-diet (HFD) is an important factor in obesity. Extracellular matrix (ECM) regulates white adipose tissue (WAT), but its mechanism is unknown.

METHODS AND RESULTS

We used three models- HFD-fed mice, human with obesity and 3T3-L1 adipocytes with oleic acid (OA)/macromolecular crowders (MMC) treatment. We observed glucose and lipids metabolic disorders, increased collagen I/IV and LAMA2/4 and upregulated integrins (ITGA1/ITGA7) - FAK - JNK/ERK1/2 signals in obese WAT from mice and human. The upregulation of ECM - integrin - FAK signals was stronger in subcutaneous WAT than in visceral WAT of mice, but these results were reversed in human. In vitro, oleic acid (OA) promoted lipid accumulation and upregulated collagen IV, LAMA4 and p-JNK. MMC was used to induce ECM deposition in adipocytes. MMC promoted adipocyte differentiation and integrins - FAK - JNK/ERK1/2 signals. When FAK phosphorylation was inhibited, downstream p-JNK decreased. Inhibition of FAK phosphorylation reduced adipocyte differentiation, but MMC partially reversed this effect.

CONCLUSION

HFD-induced ECM deposition, whose signals were transmitted into adipocytes through upregulating ITGA1/ITGA7, activated the phosphorylation of intracellular FAK - JNK/ERK1/2 signals, and promoted adipogenesis in WAT. This mechanism provides novel therapeutic targets to treat obesity. This article is protected by copyright. All rights reserved.

The extracellular matrix of hematopoietic stem cell niches

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Comprehensive overview of different classes of ECM molecules in the HSC niche.

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Overview of current knowledge on role of biophysics of the HSC niche.

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Description of approaches to create artificial stem cell niches for several application.

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Importance of considering ECM in drug development and testing.

Hematopoietic stem cells (HSCs) are the life-long source of all types of blood cells. Their function is controlled by their direct microenvironment, the HSC niche in the bone marrow. Although the importance of the extracellular matrix (ECM) in the niche by orchestrating niche architecture and cellular function is widely acknowledged, it is still underexplored. In this review, we provide a comprehensive overview of the ECM in HSC niches. For this purpose, we first briefly outline HSC niche biology and then review the role of the different classes of ECM molecules in the niche one by one and how they are perceived by cells. Matrix remodeling and the emerging importance of biophysics in HSC niche function are discussed. Finally, the application of the current knowledge of ECM in the niche in form of artificial HSC niches for HSC expansion or targeted differentiation as well as drug testing is reviewed.

The laminin-binding integrins regulate nuclear factor κB-dependent epithelial cell polarity and inflammation

The main laminin-binding integrins α3β1, α6β1 and α6β4 are co-expressed in the developing kidney collecting duct system. We previously showed that deleting the integrin α3 or α6 subunit in the ureteric bud, which gives rise to the kidney collecting system, caused either a mild or no branching morphogenesis phenotype, respectively. To determine whether these two integrin subunits cooperate in kidney collecting duct development, we deleted α3 and α6 in the developing ureteric bud. The collecting system of the double knockout phenocopied the α3 integrin conditional knockout. However, with age, the mice developed severe inflammation and fibrosis around the collecting ducts, resulting in kidney failure. Integrin α3α6-null collecting duct epithelial cells showed increased secretion of pro-inflammatory cytokines and displayed mesenchymal characteristics, causing loss of barrier function. These features resulted from increased nuclear factor kappa-B (NF-κB) activity, which regulated the Snail and Slug (also known as Snai1 and Snai2, respectively) transcription factors and their downstream targets. These data suggest that laminin-binding integrins play a key role in the maintenance of kidney tubule epithelial cell polarity and decrease pro-inflammatory cytokine secretion by regulating NF-κB-dependent signaling.

ECM-integrin signalling instructs cellular position-sensing to pattern the early mouse embryo

Development entails patterned emergence of diverse cell types within the embryo. In mammals, cells positioned inside the embryo give rise to the inner cell mass (ICM), which eventually forms the embryo itself. Yet, the molecular basis of how these cells recognise their ‘inside’ position to instruct their fate is unknown. Here, we show that provision of extracellular matrix (ECM) to isolated embryonic cells induces ICM specification and alters the subsequent spatial arrangement between epiblast (EPI) and primitive endoderm (PrE) cells that emerge within the ICM. Notably, this effect is dependent on integrin β1 activity and involves apical-to-basal conversion of cell polarity. We demonstrate that ECM-integrin activity is sufficient for ‘inside’ positional signalling and is required for correct EPI/PrE patterning. Thus, our findings highlight the significance of ECM-integrin adhesion in enabling position sensing by cells to achieve tissue patterning.

Summary: The importance of patterned cell-extracellular matrix (ECM) interactions in early mouse development: ECM signals can modulate both cell fate and the relative spatial arrangement between cells.

Roles of Integrins in Gastrointestinal Cancer Metastasis

Integrins are a large family of heterodimeric transmembrane receptors which mediate cell adhesion and transmit signals to the cell interior. The mechanistic roles of integrins have long been an enigma in cancer, given its complexity in regulating different cellular behaviors. Recently, however, increasing research is providing new insights into its function and the underlying mechanisms, which collectively include the influences of altered integrin expression on the aberrant signaling pathways and cancer progression. Many studies have also demonstrated the potentiality of integrins as therapeutic targets in cancer treatment. In this review, we have summarized these recent reports and put a particular emphasis on the dysregulated expression of integrins and how they regulate related signaling pathways to facilitate the metastatic progression of gastrointestinal cancer, including gastric cancer (GC) and colorectal cancer (CRC), which will address the crucial roles of integrins in gastrointestinal cancer.

The adhesive heterogeneity of different compartments of oral mucosal rete ridges

Rete ridges play a critical role in maintaining epidermal structure and mechanical properties. Notably, rete ridges can be divided into three compartments: the base, slope and tip. The present study aims to explore whether these three compartments have distinct adhesive functions. We collected 28 normal masticatory mucosae to prepare paraffin-embedded sections. Immunohistochemistry and immunofluorescent staining were used to analyse the expression pattern of integrin α6 and β4 in different compartments of the rete ridges. To observe whether the different compartments had distinct adhesive forces, dermal-epidermal junction separation experiments were performed by peeling the oral epithelium from the lamina propria after treatment with cold saline for 72 h. The results showed that integrin α6 and β4 prefer the basal layer keratinocytes closely adjacent to the base compartment of the rete ridges. The oral mucosal epithelium separated from the underlying lamina propria at the tip of rete ridges when they were peeled after the cold saline treatment. In conclusion, the adhesive force of the basal layer keratinocytes at the base of the rete ridges is stronger than at the tip.

Extracellular matrix protein laminin β1 regulates pain sensitivity and anxiodepression-like behaviors in mice

Patients with neuropathic pain often experience comorbid psychiatric disorders. Cellular plasticity in the anterior cingulate cortex (ACC) is assumed to be a critical interface for pain perception and emotion. However, substantial efforts have thus far been focused on the intracellular mechanisms of plasticity rather than the extracellular alterations that might trigger and facilitate intracellular changes. Laminin, a key element of the extracellular matrix (ECM), consists of one α-, one β-, and one γ-chain and is implicated in several pathophysiological processes. Here, we showed in mice that laminin β1 (LAMB1) in the ACC was significantly downregulated upon peripheral neuropathy. Knockdown of LAMB1 in the ACC exacerbated pain sensitivity and induced anxiety and depression. Mechanistic analysis revealed that loss of LAMB1 caused actin dysregulation via interaction with integrin β1 and the subsequent Src-dependent RhoA/LIMK/cofilin pathway, leading to increased presynaptic transmitter release probability and abnormal postsynaptic spine remodeling, which in turn orchestrated the structural and functional plasticity of pyramidal neurons and eventually resulted in pain hypersensitivity and anxiodepression. This study sheds new light on the functional capability of ECM LAMB1 in modulating pain plasticity and identifies a mechanism that conveys extracellular alterations to intracellular plasticity. Moreover, we identified cingulate LAMB1/integrin β1 signaling as a promising therapeutic target for the treatment of neuropathic pain and associated anxiodepression.

Canine junctional epidermolysis bullosa due to a novel mutation in LAMA3 with severe upper respiratory involvement

BACKGROUND

Junctional epidermolysis bullosa (JEB) is a group of congenital blistering skin diseases characterized by clefting through the lamina lucida of the basement membrane zone.

OBJECTIVES

To characterize the clinical and morphological features of a congenital mechanobullous disease in a litter of puppies with severe upper respiratory involvement, and to identify an associated genetic variant.

ANIMALS

Five of eight puppies in an Australian cattle dog cross-bred litter showed signs of skin fragility. Three were stillborn and one died at one month of age. The two surviving puppies were presented with blistering skin disease and severe respiratory distress. Additionally, one unaffected sibling was examined and blood was obtained for genetic testing.

METHODS AND MATERIALS

Post-mortem examination, histopathological evaluation and electron microscopy were performed. Whole genome sequencing (WGS) of one affected puppy was compared to a database of 522 dogs of 55 different breeds for variant analysis. Sanger sequencing of one additional affected and one unaffected sibling confirmed the variant.

RESULTS

Clinically, severe mucocutaneous ulcers occurred in frictional areas with claw sloughing. Histopathological results revealed subepidermal clefts and electron microscopy confirmed the split in the lamina lucida. Post-mortem examination documented extensive pharyngeal and laryngeal lesions with granulation tissue and fibrinous exudate obscuring the airway. Moderate tracheal hypoplasia contributed. The WGS revealed a novel missense variant in the laminin α3-chain XP_537297.2p(Asp2867Val), with an autosomal recessive mode of inheritance.

CONCLUSIONS AND CLINICAL RELEVANCE

A novel variant in LAMA3 caused a generalized and severe phenotype of JEB with an unique clinical presentation of upper airway obstruction.

Primary angle closure glaucoma is characterized by altered extracellular matrix homeostasis in the iris

PURPOSE

To characterize the proteome of the iris in primary angle closure glaucoma (PACG).

EXPERIMENTAL DESIGN

In this cross-sectional study, iris samples were obtained from surgical iridectomy of 48 adults with PACG and five normal controls. Peptides from iris were analysed using liquid chromatography-tandem mass spectrometry on an Orbitrap Q Exactive Plus mass spectrometer. Verification of proteins of interest was conducted using selected reaction monitoring on a triple quadrupole mass spectrometer. The main outcome was proteins with a log₂ two-fold difference in expression in iris between PACG and controls.

RESULTS

There were 3,446 non-redundant proteins identified in human iris, of which 416 proteins were upregulated and 251 proteins were downregulated in PACG compared with controls. Thirty-two upregulated proteins were either components of the extracellular matrix (ECM) (fibrillar collagens, EMILIN-2, fibrinogen, fibronectin, matrilin-2), matricellular proteins (thrombospondin-1), proteins involved in cell-matrix interactions (integrins, laminin, histidine-rich glycoprotein, paxillin), or protease inhibitors known to modulate ECM turnover (α-2 macroglobulin, tissue factor pathway inhibitor 2, papilin). Two giant proteins, titin and obscurin, were up- and down-regulated, respectively, in the iris in PACG compared with controls.

CONCLUSIONS AND CLINICAL RELEVANCE

This proteomic study shows that ECM composition and homeostasis are altered in the iris in PACG.

Laminins in metabolic tissues

Laminins are extracellular matrix proteins that reside in the basement membrane and provide structural support in addition to promoting cellular adhesion and migration. Through interactions with cell surface receptors, laminins stimulate intracellular signaling cascades which direct specific survival and differentiation outcomes. In metabolic tissues such as the pancreas, adipose, muscle, and liver, laminin isoforms are expressed in discrete temporal and spatial patterns suggesting that certain isoforms may support the development and function of particular metabolic cell types. This review focuses on the research to date detailing the expression of laminin isoforms, their potential function, as well as known pathways involved in laminin signaling in metabolic tissues. We will also discuss the current biomedical therapies involving laminins in these tissues in addition to prospective applications, with the goal being to encourage future investigation of laminins in the context of metabolic disease.

Structural mechanism of laminin recognition by integrin

Recognition of laminin by integrin receptors is central to the epithelial cell adhesion to basement membrane, but the structural background of this molecular interaction remained elusive. Here, we report the structures of the prototypic laminin receptor α6β1 integrin alone and in complex with three-chain laminin-511 fragment determined via crystallography and cryo-electron microscopy, respectively. The laminin-integrin interface is made up of several binding sites located on all five subunits, with the laminin γ1 chain C-terminal portion providing focal interaction using two carboxylate anchor points to bridge metal-ion dependent adhesion site of integrin β1 subunit and Asn189 of integrin α6 subunit. Laminin α5 chain also contributes to the affinity and specificity by making electrostatic interactions with large surface on the β-propeller domain of α6, part of which comprises an alternatively spliced X1 region. The propeller sheet corresponding to this region shows unusually high mobility, suggesting its unique role in ligand capture.

Basal lamina characterization in frozen-thawed and long-term grafted human prepubertal ovarian tissue

RESEARCH QUESTION

Are there differences in the composition and structure of the basal lamina surrounding follicles in prepubertal versus adult human ovarian tissue?

DESIGN

Frozen-thawed human ovarian tissue from six prepubertal and seven adult patients was divided into three fragments in each case: two for non-grafted tissue evaluation and one for long-term xenografting to mice. Collagen IV and laminin expression were investigated by immunohistochemistry before and after grafting. The basal lamina was analysed by transmission electron microscopy on frozen-thawed tissue.

RESULTS

In frozen-thawed tissue, collagen IV was significantly less expressed around prepubertal follicles than around adult follicles (primordial, P = 0.02; intermediate/growing follicles, P = 0.03), while laminin was significantly more expressed (primordial, P = 0.03; intermediate, P = 0.01). Collagen IV expression was significantly higher around prepubertal primordial follicles in grafted tissue than in non-grafted tissue, reaching similar levels to those in adult tissue. Ultrastructure analysis showed the basal lamina around follicles in prepubertal frozen-thawed tissue to be rather patchy and thinner than around adult follicles (primordial/intermediate, P = 0.001; primary, P = 0.02).

CONCLUSIONS

In frozen-thawed tissue, the basal lamina around prepubertal follicles is less mature than around adult follicles, but it becomes similar in both prepubertal and adult subjects after grafting. Grafting could therefore induce maturation of the basal lamina around prepubertal follicles.

A laminin-based local regulatory network in the testis that supports spermatogenesis

In adult rat testes, the basement membrane is structurally constituted by laminin and collagen chains that lay adjacent to the blood-testis barrier (BTB). It plays a crucial scaffolding role to support spermatogenesis. On the other hand, laminin-333 comprised of laminin-α3/ß3/γ3 at the apical ES (ectoplasmic specialization, a testis-specific cell-cell adherens junction at the Sertoli cell-step 8-19 spermatid interface) expressed by spermatids serves as a unique cell adhesion protein that forms an adhesion complex with α6ß1-integrin expressed by Sertoli cells to support spermiogenesis. Emerging evidence has shown that biologically active fragments are derived from basement membrane and apical ES laminin chains through proteolytic cleavage mediated by matrix metalloproteinase 9 (MMP9) and MMP2, respectively. Two of these laminin bioactive fragments: one from the basement membrane laminin-α2 chain called LG3/4/5-peptide, and one from the apical ES laminin-γ3 chain known as F5-peptide, are potent regulators that modify cell adhesion function at the Sertoli-spermatid interface (i.e., apical ES) but also at the Sertoli cell-cell interface designated basal ES at the blood-testis barrier (BTB) with contrasting effects. These findings not only highlight the physiological significance of these bioactive peptides that create a local regulatory network to support spermatogenesis, they also open a unique area of research. For instance, it is likely that several other bioactive peptides remain to be identified. These bioactive peptides including their downstream signaling proteins and cascades should be studied collectively in future investigations to elucidate the underlying mechanism(s) by which they coordinate with each other to maintain spermatogenesis. This is the goal of this review.

Potential Therapeutic Significance of Laminin in Head and Neck Squamous Carcinomas

Simple Summary

Head and neck cancers (HNC) account for approximately 500,000 new cases of tumors annually worldwide and are represented by upper aerodigestive tract malignant neoplasms, which particularly arise in oral cavity, larynx, and pharynx tissues. Thus, due to the biological diversity between the upper aerodigestive organs, and to the heterogeneity of risk factors associated with their malignant transformation, HNC behavior, and prognosis seem to strongly vary according to the tumor site. However, despite to the heterogeneity which characterizes head and neck tumors, squamous cell carcinomas (SCC) represent the predominant histopathologic HNC subtype. In this sense, it has been reported that SCC tumor biology is strongly associated with deregulations within the extracellular matrix compartment. Accordingly, it has been shown that laminin plays a remarkable role in the regulation of crucial events associated with head and neck squamous cell carcinomas (HNSCC) progression, which opens the possibility that laminin may represent a convergence point in HNSCC natural history.

Abstract

Head and neck squamous cell carcinomas (HNSCC) are among the most common and lethal tumors worldwide, occurring mostly in oral cavity, pharynx, and larynx tissues. The squamous epithelia homeostasis is supported by the extracellular matrix (ECM), and alterations in this compartment are crucial for cancer development and progression. Laminin is a fundamental component of ECM, where it represents one of the main components of basement membrane (BM), and data supporting its contribution to HNSCC genesis and progression has been vastly explored in oral cavity squamous cell carcinoma. Laminin subtypes 111 (LN-111) and 332 (LN-332) are the main isoforms associated with malignant transformation, contributing to proliferation, adhesion, migration, invasion, and metastasis, due to its involvement in the regulation of several pathways associated with HNSCC carcinogenesis, including the activation of the EGFR/MAPK signaling pathway. Therefore, it draws attention to the possibility that laminin may represent a convergence point in HNSCC natural history, and an attractive potential therapeutic target for these tumors.

Laminin-411 and -511 Modulate the Proliferation, Adhesion, and Morphology of Gastric Cancer Cells

Laminins (Ln), a type of extracellular matrix glycoprotein, are key regulators of cellular behavior. Recent work revealed that in various tumor cell lines, laminin isoforms influence specific responses, such as cell anchorage, survival, proliferation, migration, organization, and specialization. The contribution of laminin isoforms to the function of gastric cancer cells, however, remain unclear. Here, we revealed that in gastric cancer, laminin isoforms Ln411, Ln421, Ln511, and Ln521 promote cellular proliferation; Ln511 and Ln521 increase cell cytoplasmic volume; Ln511 hampers invadopodia formation in some cells, Ln511 enables prompt adhesion of cells to plates, and Ln411 and Ln511 do not alter the gastric cancer stem cell markers CD44 and Lgr5. These results indicate that Ln411 and Ln511 dynamically modulate the proliferation, adhesion, and morphology of gastric cancer cells in different ways that are independent of stem cell properties. In particular, Ln511 showed a high affinity for gastric cancer cells. Our observations broaden the possible options for controlling cancer cell progression and metastasis by modulating laminin-integrin interactions.

Spermatogonia Loss Correlates with LAMA 1 Expression in Human Prepubertal Testes Stored for Fertility Preservation

Fertility preservation for male childhood cancer survivors not yet capable of producing mature spermatozoa, relies on experimental approaches such as testicular explant culture. Although the first steps in somatic maturation can be observed in human testicular explant cultures, germ cell depletion is a common obstacle. Hence, understanding the spermatogonial stem cell (SSC) niche environment and in particular, specific components such as the seminiferous basement membrane (BM) will allow progression of testicular explant cultures. Here, we revealed that the seminiferous BM is established from 6 weeks post conception with the expression of laminin alpha 1 (LAMA 1) and type IV collagen, which persist as key components throughout development. With prepubertal testicular explant culture we found that seminiferous LAMA 1 expression is disrupted and depleted with culture time correlating with germ cell loss. These findings highlight the importance of LAMA 1 for the human SSC niche and its sensitivity to culture conditions.

Abnormal promoter DNA hypermethylation of the integrin, nidogen, and dystroglycan genes in breast cancer

Cell transmembrane receptors and extracellular matrix components play a pivotal role in regulating cell activity and providing for the concerted integration of cells in the tissue structures. We have assessed DNA methylation in the promoter regions of eight integrin genes, two nidogen genes, and the dystroglycan gene in normal breast tissues and breast carcinomas (BC). The protein products of these genes interact with the basement membrane proteins LAMA1, LAMA2, and LAMB1; abnormal hypermethylation of the LAMA1, LAMA2, and LAMB1 promoters in BC has been described in our previous publications. In the present study, the frequencies of abnormal promoter hypermethylation in BC were 13% for ITGA1, 31% for ITGA4, 4% for ITGA7, 39% for ITGA9, 38% for NID1, and 41% for NID2. ITGA2, ITGA3, ITGA6, ITGB1, and DAG1 promoters were nonmethylated in normal and BC samples. ITGA4, ITGA9, and NID1 promoter hypermethylation was associated with the HER2 positive tumors, and promoter hypermethylation of ITGA1, ITGA9, NID1 and NID2 was associated with a genome-wide CpG island hypermethylated BC subtype. Given that ITGA4 is not expressed in normal breast, one might suggest that its abnormal promoter hypermethylation in cancer is non-functional and is thus merely a passenger epimutation. Yet, this assumption is not supported by our finding that it is not associated with a hypermethylated BC subtype. ITGA4 acquires expression in a subset of breast carcinomas, and methylation of its promoter may be preventive against expression in some tumors. Strong association of abnormal ITGA4 hypermethylation with the HER2 positive tumors (p = 0.0025) suggests that simultaneous presence of both HER2 and integrin α4 receptors is not beneficial for tumor cells. This may imply HER2 and integrin α4 signaling pathways interactions that are yet to be discovered.

Stromal Protein-Mediated Immune Regulation in Digestive Cancers

Simple Summary

Solid cancers are surrounded by a network of non-cancerous cells comprising different cell types, including fibroblasts, and acellular protein structures. This entire network is called the tumor microenvironment (TME) and it provides a physical barrier to the tumor shielding it from infiltrating immune cells, such as lymphocytes, or therapeutic agents. In addition, the TME has been shown to dampen efficient immune responses of infiltrated immune cells, which are key in eliminating cancer cells from the organism. In this review, we will discuss how TME proteins in particular are involved in this dampening effect, known as immunosuppression. We will focus on three different types of digestive cancers: pancreatic cancer, colorectal cancer, and gastric cancer. Moreover, we will discuss current therapeutic approaches using TME proteins as targets to reverse their immunosuppressive effects.

Abstract

The stromal tumor microenvironment (TME) consists of immune cells, vascular and neural structures, cancer-associated fibroblasts (CAFs), as well as extracellular matrix (ECM), and favors immune escape mechanisms promoting the initiation and progression of digestive cancers. Numerous ECM proteins released by stromal and tumor cells are crucial in providing physical rigidity to the TME, though they are also key regulators of the immune response against cancer cells by interacting directly with immune cells or engaging with immune regulatory molecules. Here, we discuss current knowledge of stromal proteins in digestive cancers including pancreatic cancer, colorectal cancer, and gastric cancer, focusing on their functions in inhibiting tumor immunity and enabling drug resistance. Moreover, we will discuss the implication of stromal proteins as therapeutic targets to unleash efficient immunotherapy-based treatments.

Hold on or Cut? Integrin- and MMP-Mediated Cell-Matrix Interactions in the Tumor Microenvironment

The tumor microenvironment (TME) has become the focus of interest in cancer research and treatment. It includes the extracellular matrix (ECM) and ECM-modifying enzymes that are secreted by cancer and neighboring cells. The ECM serves both to anchor the tumor cells embedded in it and as a means of communication between the various cellular and non-cellular components of the TME. The cells of the TME modify their surrounding cancer-characteristic ECM. This in turn provides feedback to them via cellular receptors, thereby regulating, together with cytokines and exosomes, differentiation processes as well as tumor progression and spread. Matrix remodeling is accomplished by altering the repertoire of ECM components and by biophysical changes in stiffness and tension caused by ECM-crosslinking and ECM-degrading enzymes, in particular matrix metalloproteinases (MMPs). These can degrade ECM barriers or, by partial proteolysis, release soluble ECM fragments called matrikines, which influence cells inside and outside the TME. This review examines the changes in the ECM of the TME and the interaction between cells and the ECM, with a particular focus on MMPs.

Sustained activation of C3aR in a human podocyte line impairs the morphological maturation of the cells

The C3a receptor (C3aR) has been reported to be involved in various physiological and pathological processes, including the regulation of cellular structure development. Expression of C3aR has been reported in podocytes; however, data concerning the role of C3aR in podocyte morphology is scarce. The aim of the present study was to examine the effect of C3aR activation on the architectural development of podocytes. An immortal human podocyte line (HPC) was transfected with a C3a expression lentivirus vector or recombinant C3a. SB290157 was used to block the activation of C3aR. The expression of C3a in HPC cells was analyzed by reverse transcription-quantitative PCR (RT-qPCR) and ELISAs. Phase contrast and fluorescence microscopy were used to observe the morphology of the podocytes. The adhesive ability of HPC cells was analyzed using an attachment assay. RT-qPCR, cyto-immunofluorescence and western blotting were used to determine the expression levels of the adhesion-associated genes. The expression levels of carboxypeptidases in HPC cells was also detected by RT-qPCR. Compared with the untransfected and control virus-transfected HPC cells, the C3a-overexpressing cells (HPC-C3a) failed to expand their cell bodies and develop an arborized appearance in the process of maturation, which the control cells exhibited. In addition, HPC-C3a cells presented with decreased adhesive capacity, altered focal adhesion (FA) plaques and decreased expression of FA-associated genes. These effects were blocked by a C3aR antagonist; however, the addition of purified C3a could not completely mimic the effects of C3a overexpression. Furthermore, HPC cells expressed carboxypeptidases, which have been reported to be able to inactivate C3a. In summary, the results demonstrated that sustained C3aR activation impaired the morphological maturation of HPC cells, which may be associated with the altered expression of FA-associated genes and impaired FA. Since chronic complement activation has been reported in renal diseases, which indicate sustained C3aR activation in renal cells, including podocytes and podocyte progenitors, the possible role of C3aR in the dysregulation of podocyte architecture and podocyte regeneration requires further research.

Integrin-mediated adhesion and mechanosensing in the mammary gland

The mammary gland is dynamically remodelled during its postnatal development and the reproductive cycles. This inherent plasticity has been suggested to increase the susceptibility of the organ to carcinogenesis. Morphological changes in the mammary epithelium involve cell proliferation, differentiation, apoptosis, and migration which, in turn, are affected by cell adhesion to the extracellular matrix (ECM). Integrin adhesion receptors function in the sensing of the biochemical composition, patterning and mechanical properties of the ECM surrounding the cells, and strongly influence cell fate. This review aims to summarize the existing literature on how different aspects of integrin-mediated adhesion and mechanosensing, including ECM composition; stiffness and topography; integrin expression patterns; focal adhesion assembly; dynamic regulation of the actin cytoskeleton; and nuclear mechanotransduction affect mammary gland development, function and homeostasis. As the mechanical properties of a complex tissue environment are challenging to replicate in vitro, emphasis has been placed on studies conducted in vivo or using organoid models. Outright, these studies indicate that mechanosensing also contributes to the regulation of mammary gland morphogenesis in multiple ways.

Extracellular Control of Radial Glia Proliferation and Scaffolding During Cortical Development and Pathology

During the development of the cortex, newly generated neurons migrate long-distances in the expanding tissue to reach their final positions. Pyramidal neurons are produced from dorsal progenitors, e.g., radial glia (RGs) in the ventricular zone, and then migrate along RG processes basally toward the cortex. These neurons are hence dependent upon RG extensions to support their migration from apical to basal regions. Several studies have investigated how intracellular determinants are required for RG polarity and subsequent formation and maintenance of their processes. Fewer studies have identified the influence of the extracellular environment on this architecture. This review will focus on extracellular factors which influence RG morphology and pyramidal neuronal migration during normal development and their perturbations in pathology. During cortical development, RGs are present in different strategic positions: apical RGs (aRGs) have their cell bodies located in the ventricular zone with an apical process contacting the ventricle, while they also have a basal process extending radially to reach the pial surface of the cortex. This particular conformation allows aRGs to be exposed to long range and short range signaling cues, whereas basal RGs (bRGs, also known as outer RGs, oRGs) have their cell bodies located throughout the cortical wall, limiting their access to ventricular factors. Long range signals impacting aRGs include secreted molecules present in the embryonic cerebrospinal fluid (e.g., Neuregulin, EGF, FGF, Wnt, BMP). Secreted molecules also contribute to the extracellular matrix (fibronectin, laminin, reelin). Classical short range factors include cell to cell signaling, adhesion molecules and mechano-transduction mechanisms (e.g., TAG1, Notch, cadherins, mechanical tension). Changes in one or several of these components influencing the RG extracellular environment can disrupt the development or maintenance of RG architecture on which neuronal migration relies, leading to a range of cortical malformations. First, we will detail the known long range signaling cues impacting RG. Then, we will review how short range cell contacts are also important to instruct the RG framework. Understanding how RG processes are structured by their environment to maintain and support radial migration is a critical part of the investigation of neurodevelopmental disorders.