DSS-induced damage to basement membranes is repaired by matrix replacement and crosslinking

Translocation of gut bacteria promotes tumor-associated mortality by inducing immune-activated renal damage

Paraneoplastic syndrome represents severe and complex systemic clinical symptoms manifesting in multiple organs of cancer patients, but its cause and cellular underpinnings remain little explored. In this study, establishing a Drosophila model of paraneoplastic syndrome triggered by tumor transplantation, we found that the innate immune response, initiated by translocated commensal bacteria from a compromised intestine, significantly contributes to reduced lifespan in tumor-bearing hosts. Our data identify the renal system as a central hub of this paraneoplastic syndrome model, wherein the pericardial nephrocytes undergo severe damage due to an elevated immune response triggered by gut dysbiosis and bacterial translocation. This innate immune response-induced nephrocyte damage is a major contributor to reduced longevity in tumor-bearing hosts, as blocking the NF-kB/Imd pathway in nephrocytes or removing gut bacteria via germ-free derivation or antibiotic treatment ameliorates nephrocyte deterioration and extends the lifespan of tumor-bearing flies. Consistently, treatment with a detoxifying drug also extended the lifespan of the tumor hosts. Our findings highlight a critical role of the gut-kidney axis in the paraneoplastic complications observed in cancer-bearing flies, suggesting potential therapeutic targets for mitigating similar complications in cancer patients.

Chondroitin sulfate regulates proliferation of Drosophila intestinal stem cells

The basement membrane (BM) plays critical roles in stem cell maintenance and activity control. Here we show that chondroitin sulfate (CS), a major component of the Drosophila midgut BM, is required for proper control of intestinal stem cells (ISCs). Loss of Chsy, a critical CS biosynthetic gene, resulted in elevated levels of ISC proliferation during homeostasis, leading to midgut hyperplasia. Regeneration assays demonstrated that Chsy mutant ISCs failed to properly downregulate mitotic activity at the end of regeneration. We also found that CS is essential for the barrier integrity to prevent leakage of the midgut epithelium. CS is known to be polymerized by the action of the complex of Chsy and another critical protein, Chondroitin polymerizing factor (Chpf). We found that Chpf mutants show increased ISC division during midgut homeostasis and regeneration, similar to Chsy mutants. As Chpf is induced by a tissue damage during regeneration, our data suggest that Chpf functions with Chsy to facilitate CS remodeling and stimulate tissue repair. We propose that the completion of the repair of CS-containing BM acts as a prerequisite to properly terminate the regeneration process.

Piezo-dependent surveillance of matrix stiffness generates transient cells that repair the basement membrane

Basement membranes are extracellular matrix sheets separating tissue layers and providing mechanical support, and collagen IV (Col4) is their most abundant structural protein. Although basement membranes are repaired after damage, little is known about repair, including whether and how damage is detected, what cells repair the damage, and how repair is controlled to avoid fibrosis. Using the intestinal basement membrane of adult Drosophila as a model, we show that after basement membrane damage, there is a sharp increase in enteroblasts transiently expressing Col4, termed "matrix mender" cells. Enteroblast-derived Col4 is specifically required for matrix repair. The increase in matrix mender cells requires the mechanosensitive ion channel Piezo, expressed in intestinal stem cells. Matrix menders are induced by the loss of matrix stiffness, as specifically inhibiting Col4 crosslinking is sufficient for Piezo-dependent induction of matrix mender cells. Our data suggest that epithelial stem cells control basement membrane integrity by monitoring stiffness.

The transmembrane protein Syndecan is required for stem cell survival and maintenance of their nuclear properties

Tissue maintenance is underpinned by resident stem cells whose activity is modulated by microenvironmental cues. Using Drosophila as a simple model to identify regulators of stem cell behaviour and survival in vivo, we have identified novel connections between the conserved transmembrane proteoglycan Syndecan, nuclear properties and stem cell function. In the Drosophila midgut, Syndecan depletion in intestinal stem cells results in their loss from the tissue, impairing tissue renewal. At the cellular level, Syndecan depletion alters cell and nuclear shape, and causes nuclear lamina invaginations and DNA damage. In a second tissue, the developing Drosophila brain, live imaging revealed that Syndecan depletion in neural stem cells results in nuclear envelope remodelling defects which arise upon cell division. Our findings reveal a new role for Syndecan in the maintenance of nuclear properties in diverse stem cell types.

Piezo-dependent surveillance of matrix stiffness generates transient cells that repair the basement membrane

Basement membranes are extracellular matrix sheets separating tissue layers and providing mechanical support, and Collagen IV (Col4) is their most abundant protein. Although basement membranes are repaired after damage, little is known about repair, including whether and how damage is detected, what cells repair the damage, and how repair is controlled to avoid fibrosis. Using the intestinal basement membrane of adult Drosophila as a model, we show that after basement membrane damage, there is a sharp increase in enteroblasts transiently expressing Col4, or "matrix mender" cells. Enteroblast-derived Col4 is specifically required for matrix repair. The increase in matrix mender cells requires the mechanosensitive ion channel Piezo, expressed in intestinal stem cells. Matrix menders are induced by the loss of matrix stiffness, as specifically inhibiting Col4 crosslinking is sufficient for Piezo-dependent induction of matrix mender cells. Our data suggest that epithelial stem cells control basement membrane integrity by monitoring stiffness.

Basement Membranes, Brittlestar Tendons, and Their Mechanical Adaptability

Basement membranes (BMs) are thin layers of extracellular matrix that separate epithelia, endothelia, muscle cells, and nerve cells from adjacent interstitial connective tissue. BMs are ubiquitous in almost all multicellular animals, and their composition is highly conserved across the Metazoa. There is increasing interest in the mechanical functioning of BMs, including the involvement of altered BM stiffness in development and pathology, particularly cancer metastasis, which can be facilitated by BM destabilization. Such BM weakening has been assumed to occur primarily through enzymatic degradation by matrix metalloproteinases. However, emerging evidence indicates that non-enzymatic mechanisms may also contribute. In brittlestars (Echinodermata, Ophiuroidea), the tendons linking the musculature to the endoskeleton consist of extensions of muscle cell BMs. During the process of brittlestar autotomy, in which arms are detached for the purpose of self-defense, muscles break away from the endoskeleton as a consequence of the rapid destabilization and rupture of their BM-derived tendons. This contribution provides a broad overview of current knowledge of the structural organization and biomechanics of non-echinoderm BMs, compares this with the equivalent information on brittlestar tendons, and discusses the possible relationship between the weakening phenomena exhibited by BMs and brittlestar tendons, and the potential translational value of the latter as a model system of BM destabilization.

Stilbenoid compounds inhibit NF-κB-mediated inflammatory responses in the Drosophila intestine

Introduction

Stilbenoid compounds have been described to have anti-inflammatory properties in animal models in vivo, and have been shown to inhibit Ca2+-influx through the transient receptor potential ankyrin 1 (TrpA1).

Methods

To study how stilbenoid compounds affect inflammatory signaling in vivo, we have utilized the fruit fly, Drosophila melanogaster, as a model system. To induce intestinal inflammation in the fly, we have fed flies with the intestinal irritant dextran sodium sulphate (DSS).

Results

We found that DSS induces severe changes in the bacteriome of the Drosophila intestine, and that this dysbiosis causes activation of the NF-κB transcription factor Relish. We have taken advantage of the DSS-model to study the anti-inflammatory properties of the stilbenoid compounds pinosylvin (PS) and pinosylvin monomethyl ether (PSMME). With the help of in vivo approaches, we have identified PS and PSMME to be transient receptor ankyrin 1 (TrpA1)-dependent antagonists of NF-κB-mediated intestinal immune responses in Drosophila. We have also computationally predicted the putative antagonist binding sites of these compounds at Drosophila TrpA1.

Discussion

Taken together, we show that the stilbenoids PS and PSMME have anti-inflammatory properties in vivo in the intestine and can be used to alleviate chemically induced intestinal inflammation in Drosophila.

Analysis of Drosophila and mouse mutants reveals that Peroxidasin is required for tissue mechanics and full viability

Basement membranes are thin strong sheets of extracellular matrix. They provide mechanical and biochemical support to epithelia, muscles, nerves, and blood vessels, among other tissues. The mechanical properties of basement membranes are conferred in part by Collagen IV (Col4), an abundant protein of basement membrane that forms an extensive two-dimensional network through head-to-head and tail-to-tail interactions. After the Col4 network is assembled into a basement membrane, it is crosslinked by the matrix-resident enzyme Peroxidasin to form a large covalent polymer. Peroxidasin and Col4 crosslinking are highly conserved, indicating they are essential, but homozygous mutant mice have mild phenotypes. To explore the role of Peroxidasin, we analyzed mutants in Drosophila, including a newly generated catalytic null, and found that homozygotes were mostly lethal with 13% viable escapers. A Mendelian analysis of mouse mutants shows a similar pattern, with homozygotes displaying ~50% lethality and ~50% escapers. Despite the strong mutations, the homozygous escapers had low but detectable levels of Col4 crosslinking, indicating that inefficient alternative mechanisms exist and that are probably responsible for the viable escapers. Further, fly mutants have phenotypes consistent with a decrease in stiffness. Interestingly, we found that even after adult basement membranes are assembled and crosslinked, Peroxidasin is still required to maintain stiffness. These results suggest that Peroxidasin crosslinking may be more important than previously appreciated.

Dextran sodium sulfate alters antioxidant status in the gut affecting the survival of Drosophila melanogaster

Inflammatory bowel disease (IBD) is a group of disorders characterized by chronic inflammation in the intestine. Several studies confirmed that oxidative stress induced by an enormous amount of reactive free radicals triggers the onset of IBD. Currently, there is an increasing trend in the global incidence of IBD and it is coupled with a lack of adequate long-term therapeutic options. At the same time, progress in research to understand the pathogenesis of IBD has been hampered due to the absence of adequate animal models. Currently, the toxic chemical Dextran Sulfate Sodium (DSS) induced gut inflammation in rodents is widely perceived as a good model of experimental colitis or IBD. Drosophila melanogaster, a genetic animal model, shares ~ 75% sequence similarity to genes causing different diseases in humans and also has conserved digestion and absorption features. Therefore, in the current study, we used Drosophila as a model system to induce and investigate DSS-induced colitis. Anatomical, biochemical, and molecular analyses were performed to measure the levels of inflammation and cellular disturbances in the gastrointestinal (GI) tract of Drosophila. Our study shows that DSS-induced inflammation lowers the levels of antioxidant molecules, affects the life span, reduces physiological activity and induces cellular damage in the GI tract mimicking pathophysiological features of IBD in Drosophila. Such a DSS-induced Drosophila colitis model can be further used for understanding the molecular pathology of IBD and screening novel drugs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03349-2.

Mechanisms of mucosal healing: treating inflammatory bowel disease without immunosuppression?

Almost all currently available treatments for inflammatory bowel disease (IBD) act by inhibiting inflammation, often blocking specific inflammatory molecules. However, given the infectious and neoplastic disease burden associated with chronic immunosuppressive therapy, the goal of attaining mucosal healing without immunosuppression is attractive. The absence of treatments that directly promote mucosal healing and regeneration in IBD could be linked to the lack of understanding of the underlying pathways. The range of potential strategies to achieve mucosal healing is diverse. However, the targeting of regenerative mechanisms has not yet been achieved for IBD. Stem cells provide hope as a regenerative treatment and are used in limited clinical situations. Growth factors are available for the treatment of short bowel syndrome but have not yet been applied in IBD. The therapeutic application of organoid culture and stem cell therapy to generate new intestinal tissue could provide a novel mechanism to restore barrier function in IBD. Furthermore, blocking key effectors of barrier dysfunction (such as MLCK or damage-associated molecular pattern molecules) has shown promise in experimental IBD. Here, we review the diversity of molecular targets available to directly promote mucosal healing, experimental models to identify new potential pathways and some of the anticipated potential therapies for IBD.

Mechanisms of mucosal healing: treating inflammatory bowel disease without immunosuppression?

Almost all currently available treatments for inflammatory bowel disease (IBD) act by inhibiting inflammation, often blocking specific inflammatory molecules. However, given the infectious and neoplastic disease burden associated with chronic immunosuppressive therapy, the goal of attaining mucosal healing without immunosuppression is attractive. The absence of treatments that directly promote mucosal healing and regeneration in IBD could be linked to the lack of understanding of the underlying pathways. The range of potential strategies to achieve mucosal healing is diverse. However, the targeting of regenerative mechanisms has not yet been achieved for IBD. Stem cells provide hope as a regenerative treatment and are used in limited clinical situations. Growth factors are available for the treatment of short bowel syndrome but have not yet been applied in IBD. The therapeutic application of organoid culture and stem cell therapy to generate new intestinal tissue could provide a novel mechanism to restore barrier function in IBD. Furthermore, blocking key effectors of barrier dysfunction (such as MLCK or damage-associated molecular pattern molecules) has shown promise in experimental IBD. Here, we review the diversity of molecular targets available to directly promote mucosal healing, experimental models to identify new potential pathways and some of the anticipated potential therapies for IBD.

Integrin-ECM interactions and membrane-associated Catalase cooperate to promote resilience of the Drosophila intestinal epithelium

Balancing cellular demise and survival constitutes a key feature of resilience mechanisms that underlie the control of epithelial tissue damage. These resilience mechanisms often limit the burden of adaptive cellular stress responses to internal or external threats. We recently identified Diedel, a secreted protein/cytokine, as a potent antagonist of apoptosis-induced regulated cell death in the Drosophila intestinal midgut epithelium during aging. Here, we show that Diedel is a ligand for RGD-binding Integrins and is thus required for maintaining midgut epithelial cell attachment to the extracellular matrix (ECM)-derived basement membrane. Exploiting this function of Diedel, we uncovered a resilience mechanism of epithelial tissues, mediated by Integrin-ECM interactions, which shapes cell death spreading through the regulation of cell detachment and thus cell survival. Moreover, we found that resilient epithelial cells, enriched for Diedel-Integrin-ECM interactions, are characterized by membrane association of Catalase, thus preserving extracellular reactive oxygen species (ROS) balance to maintain epithelial integrity. Intracellular Catalase can relocalize to the extracellular membrane to limit cell death spreading and repair Integrin-ECM interactions induced by the amplification of extracellular ROS, which is a critical adaptive stress response. Membrane-associated Catalase, synergized with Integrin-ECM interactions, likely constitutes a resilience mechanism that helps balance cellular demise and survival within epithelial tissues.

Kidney organoids recapitulate human basement membrane assembly in health and disease

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

The matrix in focus: new directions in extracellular matrix research from the 2021 ASMB hybrid meeting

The extracellular matrix (ECM) is a complex assembly of macromolecules that provides both architectural support and molecular signals to cells and modulate their behaviors. Originally considered a passive mechanical structure, decades of research have since demonstrated how the ECM dynamically regulates a diverse set of cellular processes in development, homeostasis, and disease progression. In September 2021, the American Society for Matrix Biology (ASMB) organized a hybrid scientific meeting, integrating in-person and virtual formats, to discuss the latest developments in ECM research. Here, we highlight exciting scientific advances that emerged from the meeting including (1) the use of model systems for fundamental and translation ECM research, (2) ECM-targeting approaches as therapeutic modalities, (3) cell-ECM interactions, and (4) the ECM as a critical component of tissue engineering strategies. In addition, we discuss how the ASMB incorporated mentoring, career development, and diversity, equity, and inclusion initiatives in both virtual and in-person events. Finally, we reflect on the hybrid scientific conference format and how it will help the ASMB accomplish its mission moving forward.

Nonlinear elasticity of biological basement membrane revealed by rapid inflation and deflation

Basement membrane (BM) is a thin layer of extracellular matrix that surrounds most animal tissues, serving as a physical barrier while allowing nutrient exchange. Although they have important roles in tissue structural integrity, physical properties of BMs remain largely uncharacterized, which limits our understanding of their mechanical functions. Here, we perform pressure-controlled inflation and deflation to directly measure the nonlinear mechanics of BMs in situ. We show that the BMs behave as a permeable, hyperelastic material whose mechanical properties and permeability can be measured in a model-independent manner. Furthermore, we find that BMs exhibit a remarkable nonlinear stiffening behavior, in contrast to the reconstituted Matrigel. This nonlinear stiffening behavior helps the BMs to avoid the snap-through instability (or structural softening) widely observed during the inflation of most elastomeric balloons and thus maintain sufficient confining stress to the enclosed tissues during their growth.

Atypical basement membranes and basement membrane diversity - what is normal anyway?

The evolution of basement membranes (BMs) played an essential role in the organization of animal cells into tissues and diversification of body plans. The archetypal BM is a compact extracellular matrix polymer containing laminin, nidogen, collagen IV and perlecan (LNCP matrix) tightly packed into a homogenously thin planar layer. Contrasting this clear-cut morphological and compositional definition, there are numerous examples of LNCP matrices with unusual characteristics that deviate from this planar organization. Furthermore, BM components are found in non-planar matrices that are difficult to categorize as BMs at all. In this Review, I discuss examples of atypical BM organization. First, I highlight atypical BM structures in human tissues before describing the functional dissection of a plethora of BMs and BM-related structures in their tissue contexts in the fruit fly Drosophila melanogaster To conclude, I summarize our incipient understanding of the mechanisms that provide morphological, compositional and functional diversity to BMs. It is becoming increasingly clear that atypical BMs are quite prevalent, and that even typical planar BMs harbor a lot of diversity that we do not yet comprehend.

Glycation alters the mechanical behavior of kidney extracellular matrix

The mechanical properties of the extracellular matrix (ECM) are important in maintaining normal physiological function, and changes in ECM mechanics drive disease. The biochemical structure of the ECM is modified with aging and in diseases such as diabetes. One mechanism of ECM modification is the non-enzymatic reaction between sugars and ECM proteins resulting in formation of advanced glycation end products (AGEs). Some AGE reactions result in formation of molecular crosslinks within or between matrix proteins, but it is not clear how sugar-mediated biochemical modification of the ECM translates to changes in kidney ECM mechanical properties. AGE-mediated changes in ECM mechanics may have pathological consequences in diabetic kidney disease. To determine how sugars alter the mechanical properties of the kidney ECM, we employ custom methodologies to evaluate the mechanical properties of isolated tubular basement membrane (TBM) and glomerular ECM. Results show that the mechanical properties of TBM and glomerular ECM stiffness were altered by incubation in glucose and ribose. Mechanical behavior of TBM and glomerular ECM were further evaluated using mechanical models for hyperelastic materials in tension and compression. Increased ECM stiffness following sugar modification corresponded to increased crosslinking as determined by ECM fluorescence and reduced pepsin extractability of sugar modified ECM. These results show that sugar-induced modifications significantly affect the mechanical properties of kidney ECM. AGE-mediated changes in ECM mechanics may be important in progression of chronic diseases including diabetic kidney disease.

In-silico definition of the Drosophila melanogaster matrisome

The extracellular matrix (ECM) is an assembly of hundreds of proteins that structurally supports the cells it surrounds and biochemically regulates their functions. Drosophila melanogaster has emerged as a powerful model organism to study fundamental mechanisms underlying ECM protein secretion, ECM assembly, and ECM roles in pathophysiological processes. However, as of today, we do not possess a well-defined list of the components forming the ECM of this organism. We previously reported the development of computational pipelines to define the matrisome - the ensemble of genes encoding ECM and ECM-associated proteins - of humans, mice, zebrafish and C. elegans. Using a similar approach, we report here that our pipeline has identified 641 genes constituting the Drosophila matrisome. We further classify these genes into different structural and functional categories, including an expanded way to classify genes encoding proteins forming apical ECMs. We illustrate how having a comprehensive list of Drosophila matrisome proteins can be used to annotate large proteomic datasets and identify unsuspected roles for the ECM in pathophysiological processes. Last, to aid the dissemination and usage of the proposed definition and categorization of the Drosophila matrisome by the scientific community, our list has been made available through three public portals: The Matrisome Project (http://matrisome.org), The FlyBase (https://flybase.org/), and GLAD (https://www.flyrnai.org/tools/glad/web/).

Beyond proteases: Basement membrane mechanics and cancer invasion

In epithelial cancers, cells must invade through basement membranes (BMs) to metastasize. The BM, a thin layer of extracellular matrix underlying epithelial and endothelial tissues, is primarily composed of laminin and collagen IV and serves as a structural barrier to cancer cell invasion, intravasation, and extravasation. BM invasion has been thought to require protease degradation since cells, which are typically on the order of 10 µm in size, are too large to squeeze through the nanometer-scale pores of the BM. However, recent studies point toward a more complex picture, with physical forces generated by cancer cells facilitating protease-independent BM invasion. Moreover, collective cell interactions, proliferation, cancer-associated fibroblasts, myoepithelial cells, and immune cells are all implicated in regulating BM invasion through physical forces. A comprehensive understanding of BM structure and mechanics and diverse modes of BM invasion may yield new strategies for blocking cancer progression and metastasis.