LARP6 Meets Collagen mRNA: Specific Regulation of Type I Collagen Expression

Genome-wide investigation of the LARP gene family: focus on functional identification and transcriptome profiling of ZmLARP6c1 in maize pollen

BACKGROUND

The La-related proteins (LARPs) are a superfamily of RNA-binding proteins associated with regulation of gene expression. Evidence points to an important role for post-transcriptional control of gene expression in germinating pollen tubes, which could be aided by RNA-binding proteins.

RESULTS

In this study, a genome-wide investigation of the LARP proteins in eight plant species was performed. The LARP proteins were classified into three families based on a phylogenetic analysis. The gene structure, conserved motifs, cis-acting elements in the promoter, and gene expression profiles were investigated to provide a comprehensive overview of the evolutionary history and potential functions of ZmLARP genes in maize. Moreover, ZmLARP6c1 was specifically expressed in pollen and ZmLARP6c1 was localized to the nucleus and cytoplasm in maize protoplasts. Overexpression of ZmLARP6c1 enhanced the percentage pollen germination compared with that of wild-type pollen. In addition, transcriptome profiling analysis revealed that differentially expressed genes included PABP homologous genes and genes involved in jasmonic acid and abscisic acid biosynthesis, metabolism, signaling pathways and response in a Zmlarp6c1::Ds mutant and ZmLARP6c1-overexpression line compared with the corresponding wild type.

CONCLUSIONS

The findings provide a basis for further evolutionary and functional analyses, and provide insight into the critical regulatory function of ZmLARP6c1 in maize pollen germination.

Comparative Analysis of Acute Kidney Injury Models and Related Fibrogenic Responses: Convergence on Methylation Patterns Regulated by Cold Shock Protein

BACKGROUND

Fibrosis is characterized by excessive extracellular matrix formation in solid organs, disrupting tissue architecture and function. The Y-box binding protein-1 (YB-1) regulates fibrosis-related genes (e.g., Col1a1, Mmp2, and Tgfβ1) and contributes significantly to disease progression. This study aims to identify fibrogenic signatures and the underlying signaling pathways modulated by YB-1.

METHODS

Transcriptomic changes associated with matrix gene patterns in human chronic kidney diseases and murine acute injury models were analyzed with a focus on known YB-1 targets. Ybx1-knockout mouse strains (Ybx1ΔRosaERT+TX and Ybx1ΔLysM) were subjected to various kidney injury models. Fibrosis patterns were characterized by histopathological staining, transcriptome analysis, qRT-PCR, methylation analysis, zymography, and Western blotting.

RESULTS

Integrative transcriptomic analyses revealed that YB-1 is involved in several fibrogenic signatures related to the matrisome, the WNT, YAP/TAZ, and TGFß pathways, and regulates Klotho expression. Changes in the methylation status of the Klotho promoter by specific methyltransferases (DNMT) are linked to YB-1 expression, extending to other fibrogenic genes. Notably, kidney-resident cells play a significant role in YB-1-modulated fibrogenic signaling, whereas infiltrating myeloid immune cells have a minimal impact.

CONCLUSIONS

YB-1 emerges as a master regulator of fibrogenesis, guiding DNMT1 to fibrosis-related genes. This highlights YB-1 as a potential target for epigenetic therapies interfering in this process.

Abstinence Restores Cardiac Function in Mice with Established Alcohol-Induced Cardiomyopathy

Alcohol-induced cardiomyopathy (ACM) has a poor prognosis with up to a 50% chance of death within four years of diagnosis. There are limited studies investigating the potential of abstinence for promoting repair after alcohol-induced cardiac damage, particularly in a controlled preclinical study design. Here, we developed an exposure protocol that led to significant decreases in cardiac function in C57BL6/J mice within 30 days; dP/dt max decreased in the mice fed alcohol for 30 days (8054 ± 664.5 mmHg/s compared to control mice: 11,188 ± 724.2 mmHg/s, p < 0.01), and the dP/dt min decreased, as well (-7711 ± 561 mmHg/s compared to control mice: -10,147 ± 448.2 mmHg/s, p < 0.01). Quantitative PCR was used to investigate inflammatory and fibrotic biomarkers, while histology was used to depict overt changes in cardiac fibrosis. We observed a complete recovery of function after abstinence (dP/dt max increased from 8054 ± 664 mmHg/s at 30 days to 11,967 ± 449 mmHg/s after abstinence, p < 0.01); further, both inflammatory and fibrotic biomarkers decreased after abstinence. These results lay the groundwork for future investigation of the molecular mechanisms underlying recovery from alcohol-induced damage in the heart.

Sex differences in the genetic and molecular mechanisms of coronary artery disease

Sex differences in coronary artery disease (CAD) presentation, risk factors and prognosis have been widely studied. Similarly, studies on atherosclerosis have shown prominent sex differences in plaque biology. Our understanding of the underlying genetic and molecular mechanisms that drive these differences remains fragmented and largely understudied. Through reviewing genetic and epigenetic studies, we identified more than 40 sex-differential candidate genes (13 within known CAD loci) that may explain, at least in part, sex differences in vascular remodeling, lipid metabolism and endothelial dysfunction. Studies with transcriptomic and single-cell RNA sequencing data from atherosclerotic plaques highlight potential sex differences in smooth muscle cell and endothelial cell biology. Especially, phenotypic switching of smooth muscle cells seems to play a crucial role in female atherosclerosis. This matches the known sex differences in atherosclerotic phenotypes, with men being more prone to lipid-rich plaques, while women are more likely to develop fibrous plaques with endothelial dysfunction. To unravel the complex mechanisms that drive sex differences in CAD, increased statistical power and adjustments to study designs and analysis strategies are required. This entails increasing inclusion rates of women, performing well-defined sex-stratified analyses and the integration of multi-omics data.

Environmental stiffness restores mechanical homeostasis in vimentin-depleted cells

Recent experimental evidence indicates a role for the intermediate filament vimentin in regulating cellular mechanical homeostasis, but its precise contribution remains to be discovered. Mechanical homeostasis requires a balanced bi-directional interplay between the cell's microenvironment and the cellular morphological and mechanical state-this balance being regulated via processes of mechanotransduction and mechanoresponse, commonly referred to as mechanoreciprocity. Here, we systematically analyze vimentin-expressing and vimentin-depleted cells in a swatch of in vitro cellular microenvironments varying in stiffness and/or ECM density. We find that vimentin-expressing cells maintain mechanical homeostasis by adapting cellular morphology and mechanics to micromechanical changes in the microenvironment. However, vimentin-depleted cells lose this mechanoresponse ability on short timescales, only to reacquire it on longer time scales. Indeed, we find that the morphology and mechanics of vimentin-depleted cell in stiffened microenvironmental conditions can get restored to the homeostatic levels of vimentin-expressing cells. Additionally, we observed vimentin-depleted cells increasing collagen matrix synthesis and its crosslinking, a phenomenon which is known to increase matrix stiffness, and which we now hypothesize to be a cellular compensation mechanism for the loss of vimentin. Taken together, our findings provide further insight in the regulating role of intermediate filament vimentin in mediating mechanoreciprocity and mechanical homeostasis.

Woven bone formation and mineralization by rat mesenchymal stromal cells imply increased expression of the intermediate filament desmin

Background

Disordered and hypomineralized woven bone formation by dysfunctional mesenchymal stromal cells (MSCs) characterize delayed fracture healing and endocrine -metabolic bone disorders like fibrous dysplasia and Paget disease of bone. To shed light on molecular players in osteoblast differentiation, woven bone formation, and mineralization by MSCs we looked at the intermediate filament desmin (DES) during the skeletogenic commitment of rat bone marrow MSCs (rBMSCs), where its bone-related action remains elusive.

Results

Monolayer cultures of immunophenotypically- and morphologically - characterized, adult male rBMSCs showed co-localization of desmin (DES) with vimentin, F-actin, and runx2 in all cell morphotypes, each contributing to sparse and dense colonies. Proteomic analysis of these cells revealed a topologically-relevant interactome, focused on cytoskeletal and related enzymes//chaperone/signalling molecules linking DES to runx2 and alkaline phosphatase (ALP). Osteogenic differentiation led to mineralized woven bone nodules confined to dense colonies, significantly smaller and more circular with respect to controls. It significantly increased also colony-forming efficiency and the number of DES-immunoreactive dense colonies, and immunostaining of co-localized DES/runx-2 and DES/ALP. These data confirmed pre-osteoblastic and osteoblastic differentiation, woven bone formation, and mineralization, supporting DES as a player in the molecular pathway leading to the osteogenic fate of rBMSCs.

Conclusion

Immunocytochemical and morphometric studies coupled with proteomic and bioinformatic analysis support the concept that DES may act as an upstream signal for the skeletogenic commitment of rBMSCs. Thus, we suggest that altered metabolism of osteoblasts, woven bone, and mineralization by dysfunctional BMSCs might early be revealed by changes in DES expression//levels. Non-union fractures and endocrine - metabolic bone disorders like fibrous dysplasia and Paget disease of bone might take advantage of this molecular evidence for their early diagnosis and follow-up.

Temperature-Controlled Expression of a Recombinant Human-like Collagen I Peptide in Escherichia coli

Collagen is the functional protein of the skin, tendons, ligaments, cartilage, bone, and connective tissue. Due to its extraordinary properties, collagen has a wide range of applications in biomedicine, tissue engineering, food, and cosmetics. In this study, we designed a functional fragment of human type I collagen (rhLCOL-I) and expressed it in Escherichia coli (E. coli) BL21(DE3) PlysS containing a thermal-induced plasmid, pBV-rhLCOL-I. The results indicated that the optimal expression level of the rhLCOL-I reached 36.3% of the total protein at 42 °C, and expressed in soluble form. In a 7 L fermentation, the yield of purified rhLCOL-I was 1.88 g/L. Interestingly, the plasmid, pBV220-rhLCOL-I, was excellently stable during the fermentation process, even in the absence of antibiotics. Functional analyses indicated that rhLCOL-I had the capacity to promote skin cell migration and adhesion in vitro and in vivo. Taken together, we developed a high-level and low-cost approach to produce collagen fragments suitable for medical applications in E. coli.

Dietary threonine improves muscle nutritional value and muscle hardness associated with collagen synthesis in grass carp (Ctenopharyngodon idella)

To further explain the improvement effect of threonine (Thr) on the fillet quality of fish, a 9-week feeding experiment was conducted. After feeding graded levels of Thr (2.38, 5.38, 8.38, 11.38, 14.38 and 17.38 g/kg), the compositions of fillet hydrolyzed amino acid and fatty acid, and the muscle hardness associated with collagen biosynthesis were mainly analyzed in grass carp (Ctenopharyngodon idella). The results showed that Thr increased the pH value, changed the amino acids and fatty acid composition of fillets, especially essential amino acid (EAA), C22:6n3 (DHA) and C20:5n3 (EPA). Furthermore, this study revealed for the first time that the improvement of muscle hardness by Thr was associated with collagen biosynthesis, and the TGF-β1/Smads, LARP6a and Hsp47 regulate transcriptional processes, translation initiation and post-translational modifications in collagen biosynthesis, respectively. This study offered a basis for exploring the contribution of Thr in improving muscle quality in sub-adult grass carp.

Macrophage-Derived MMP-9 and MMP-2 are Closely Related to the Rupture of the Fibrous Capsule of Hepatocellular Carcinoma Leading to Tumor Invasion

BACKGROUND

Hepatocellular carcinoma (HCC) is an aggressive tumor with a poor clinical prognosis. Rupture of the fibrous capsule (FC) is a very important clinical phenomenon in the invasion and metastasis of HCC. FC is mainly composed of type I collagen (COL1A1). However, it is not clear what caused the FC rupture. In this study, we aimed to determine whether the rupture of FC in HCC patients was related to macrophage-derived MMP-9 and MMP-2, and their clinical diagnostic value for FC rupture.

RESULTS

By performing immunohistochemical and immunofluorescence staining of ruptured FC and intact FC, the results showed that the ruptured area of FC aggregated a large number of macrophages with MMP-9 and MMP-2. Western blot analysis and Quantitative real-time PCR were used to assess the expression of MMP-9 and MMP-2 in the ruptured and relatively intact area of FC in ruptured FC patients, and the results revealed a significantly different expression of MMP-9 and MMP-2. ELISA experiments show that we could discriminate effectively between ruptured FC and intact FC by MMP-9 and MMP-2.

CONCLUSIONS

Taken together, macrophage-derived MMP-9 and MMP-2 were closely related to the rupture of the FC of HCC and subsequently led to the migration and invasion of the tumor cells through the ruptured area of FC to the para cancer. It is suggested that when performing surgical resection, it is necessary to expand the range of tumor resection for patients with ruptured FC and hence reduce the possibility of recurrence and metastasis in HCC patients.

Emodin inhibiting epithelial-mesenchymal transition in pulmonary fibrosis through the c-MYC/miR-182-5p/ZEB2 axis

Emodin is a natural anthraquinone compound, which is the main component found in the traditional Chinese herb Polygonum cuspidatum. The anti-fibrosis effects of Emodin have been reported. This study aimed to explore the specific mechanism of Emodin in the epithelial-mesenchymal transition (EMT) of pulmonary fibrosis. The pulmonary fibrosis mice models were constructed with bleomycin, the EMT models of alveolar epithelial cells were stimulated by TGF-β1, and Emodin was used for intervention. c-MYC and miR-182-5p were overexpressed or silenced by cell transfection. Our results demonstrated that Emodin attenuated pulmonary fibrosis induced by bleomycin in mice, and inhibited EMT, meanwhile downregulated c-MYC, upregulated miR-182-5p, and downregulated ZEB2 in vitro and vivo. Next, overexpression of c-MYC promoted EMT, while silencing c-MYC and overexpressing miR-182-5p inhibited EMT. Then, c-MYC negatively regulated the expression of miR-182-5p with a direct binding relationship. And miR-182-5p inhibited ZEB2 expression in a targeted manner. Finally, Emodin inhibited EMT that had been promoted by overexpression of c-MYC. In conclusion, Emodin could attenuate pulmonary fibrosis and EMT by regulating the c-MYC/miR-182-5p/ZEB2 axis, which might provide evidence for the application of Emodin in the treatment of pulmonary fibrosis.

Transcriptome Analysis Reveals Vimentin-Induced Disruption of Cell-Cell Associations Augments Breast Cancer Cell Migration

In advanced metastatic cancers with reduced patient survival and poor prognosis, expression of vimentin, a type III intermediate filament protein is frequently observed. Vimentin appears to suppress epithelial characteristics and augments cell migration but the molecular basis for these changes is not well understood. Here, we have ectopically expressed vimentin in MCF-7 and investigated its genomic and functional implications. Vimentin changed the cell shape by decreasing major axis, major axis angle and increased cell migration, without affecting proliferation. Vimentin downregulated major keratin genes KRT8, KRT18 and KRT19. Transcriptome-coupled GO and KEGG analyses revealed that vimentin-affected genes were linked to either cell-cell/cell-ECM or cell cycle/proliferation specific pathways. Using shRNA mediated knockdown of vimentin in two cell types; MCF-7FV (ectopically expressing) and MDA-MB-231 (endogenously expressing), we identified a vimentin-specific signature consisting of 13 protein encoding genes (CDH5, AXL, PTPRM, TGFBI, CDH10, NES, E2F1, FOXM1, CDC45, FSD1, BCL2, KIF26A and WISP2) and two long non-coding RNAs, LINC00052 and C15ORF9-AS1. CDH5, an endothelial cadherin, which mediates cell-cell junctions, was the most downregulated protein encoding gene. Interestingly, downregulation of CDH5 by shRNA significantly increased cell migration confirming our RNA-Seq data. Furthermore, presence of vimentin altered the lamin expression in MCF-7. Collectively, we demonstrate, for the first time, that vimentin in breast cancer cells could change nuclear architecture by affecting lamin expression, which downregulates genes maintaining cell-cell junctions resulting in increased cell migration.

LARP6 Regulates Keloid Fibroblast Proliferation, Invasion, and Ability to Synthesize Collagen

Keloid is a skin fibroproliferative disease currently having no uniformly successful treatment. The lesion is composed of actively proliferating and collagen-overproducing fibroblasts. LARP6 is an RNA-binding protein able to regulate collagen synthesis in fibroblasts and to promote proliferation and invasion of tumor cells. To explore LARP6's likely functions in keloid pathogenesis, we performed immunohistochemistry staining on human keloid tissues and discovered markedly upregulated LARP6 expression in lesion fibroblasts compared with that of normal skin and hypertrophic scar tissues. In addition, the keloid tissue‒derived fibroblasts showed constitutive upregulation of LARP6 expression as well as significantly upregulated mRNA and protein expressions of type I collagen and enhanced cell proliferation and invasive behavior in cell culture system. Intriguingly, LARP6 knockdown by targeting with small interfering RNAs significantly inhibited type I collagen expression, proliferation, and invasion capability of keloid tissue‒derived fibroblasts relative to that of normal skin‒ and hypertrophic scar‒derived fibroblasts and control keloid tissue‒derived fibroblasts that were transfected with a scrambled small interfering RNA. In conclusion, the abnormally upregulated expression of LARP6 in fibroblasts may play an important role in the growth and invasive behavior of keloid lesions.

A Trichinella spiralis new born larvae-specific protein, Ts-NBL1, interacts with host's cell vimentin

The parasitic nematode Trichinella has a special relationship with its host as it has a unique intracellular location within the feeder cell which is a structure derived from skeletal muscle fiber. It has been proposed that “parakines” secreted by Trichinella larvae serve as messengers to implement communication between the parasite and the muscle cells through a molecular cross-talk to ensure permanent coexistence within the host. The Ts-NBL1 protein is considered to be a potential key “parakine” involved in the early invasion of the muscle fiber and its transformation into a feeder cell during Trichinella spiralis infection. This study used for the first time yeast two-hybrid (Y2H) technology in Trichinella to identify Ts-NBL1 interacting proteins. GST co-affinity purification experiments confirmed vimentin as an important interactor. The discovery of the new host proteins interacting with Ts-NBL1 will help to suggest that Ts-NBL1 contributes to participate in the capsule formation of feeder cells and provide ideas for understanding the molecular and cellular mechanisms involved in the survival of Trichinella in the host.

Heterogeneity and dynamic of EMT through the plasticity of ribosome and mRNA translation

Growing evidence exposes translation and its translational machinery as key players in establishing and maintaining physiological and pathological biological processes. Examining translation may not only provide new biological insight but also identify novel innovative therapeutic targets in several fields of biology, including that of epithelial-to-mesenchymal transition (EMT). EMT is currently considered as a dynamic and reversible transdifferentiation process sustaining the transition from an epithelial to mesenchymal phenotype, known to be mainly driven by transcriptional reprogramming. However, it seems that the characterization of EMT plasticity is challenging, relying exclusively on transcriptomic and epigenetic approaches. Indeed, heterogeneity in EMT programs was reported to depend on the biological context. Here, by reviewing the involvement of translational control, translational machinery and ribosome biogenesis characterizing the different types of EMT, from embryonic and adult physiological to pathological contexts, we discuss the added value of integrating translational control and its machinery to depict the heterogeneity and dynamics of EMT programs.

Impact of Vimentin on Regulation of Cell Signaling and Matrix Remodeling

Vimentin expression contributes to cellular mechanoprotection and is a widely recognized marker of fibroblasts and of epithelial-mesenchymal transition. But it is not understood how vimentin affects signaling that controls cell migration and extracellular matrix (ECM) remodeling. Recent data indicate that vimentin controls collagen deposition and ECM structure by regulating contractile force application to the ECM and through post-transcriptional regulation of ECM related genes. Binding of cells to the ECM promotes the association of vimentin with cytoplasmic domains of adhesion receptors such as integrins. After initial adhesion, cell-generated, myosin-dependent forces and signals that impact vimentin structure can affect cell migration. Post-translational modifications of vimentin determine its adaptor functions, including binding to cell adhesion proteins like paxillin and talin. Accordingly, vimentin regulates the growth, maturation and adhesive strength of integrin-dependent adhesions, which enables cells to tune their attachment to collagen, regulate the formation of cell extensions and control cell migration through connective tissues. Thus, vimentin tunes signaling cascades that regulate cell migration and ECM remodeling. Here we consider how specific properties of vimentin serve to control cell attachment to the underlying ECM and to regulate mesenchymal cell migration and remodeling of the ECM by resident fibroblasts.

Targeting Type I Collagen for Cancer Treatment

Collagen is the most abundant protein in animals. Interactions between tumor cells and collagen influence every step of tumor development. Type I collagen is the main fibrillar collagen in the extracellular matrix and is frequently up-regulated during tumorigenesis. The binding of type I collagen to its receptors on tumor cells promotes tumor cell proliferation, epithelial-mesenchymal transition, and metastasis. Type I collagen also regulates the efficacy of tumor therapies, such as chemotherapy, radiotherapy, and immunotherapy. Furthermore, type I collagen fragments are diagnostic markers of metastatic tumors and have prognostic value. Inhibition of type I collagen synthesis has been reported to have anti-tumor effects in animal models. However, collagen has also been shown to possess anti-tumor activity. Therefore, the roles that type I collagen plays in tumor biology are complex and tumor type-dependent. In this review, we discuss the expression and regulation of synthesis of type I collagen, as well as the role up-regulated type I collagen plays in various stages of cancer progression. We also discuss the role of collagen in tumor therapy. Finally, we highlight several recent approaches targeting type I collagen for cancer treatment. This article is protected by copyright. All rights reserved.

Genetic associations with carotid intima-media thickness link to atherosclerosis with sex-specific effects in sub-Saharan Africans

Atherosclerosis precedes the onset of clinical manifestations of cardiovascular diseases (CVDs). We used carotid intima-media thickness (cIMT) to investigate genetic susceptibility to atherosclerosis in 7894 unrelated adults (3963 women, 3931 men; 40 to 60 years) resident in four sub-Saharan African countries. cIMT was measured by ultrasound and genotyping was performed on the H3Africa SNP Array. Two new African-specific genome-wide significant loci for mean-max cIMT, SIRPA (p = 4.7E-08), and FBXL17 (p = 2.5E-08), were identified. Sex-stratified analysis revealed associations with one male-specific locus, SNX29 (p = 6.3E-09), and two female-specific loci, LARP6 (p = 2.4E-09) and PROK1 (p = 1.0E-08). We replicate previous cIMT associations with different lead SNPs in linkage disequilibrium with SNPs primarily identified in European populations. Our study find significant enrichment for genes involved in oestrogen response from female-specific signals. The genes identified show biological relevance to atherosclerosis and/or CVDs, sex-differences and transferability of signals from non-African studies.

Characterization of Sequence-Specific Binding of LARP6 to the 5' Stem-Loop of Type I Collagen mRNAs and Implications for Rational Design of Antifibrotic Drugs

Excessive synthesis of type I collagen is a hallmark of fibrotic diseases. Binding of La-related protein 6 (LARP6) to the 5' stem-loop (5'SL) of collagen mRNAs regulates their translation leading to an unnaturally elevated rate of collagen biosynthesis in fibrosis. Previous work suggested that LARP6 needs two domains to form stable complex with 5'SL RNA, the La domain and the juxtaposed RNA recognition motif (RRM), jointly called the La-module. Here we describe that La domain of LARP6 is necessary and sufficient for recognition of 5'SL in RNA sequence specific manner. A three-amino-acid motif located in the flexible loop connecting the second α-helix to the β-sheet of the La domain, called the RNK-motif, is critical for binding. Mutation of any of these three amino acids abolishes the binding of the La domain to 5'SL. The major site of crosslinking of LARP6 to 5'SL RNA was mapped to this motif, as well. The RNK-motif is not found in other LARPs, which cannot bind 5'SL. Presence of RRM increases the stability of complex between La domain and 5'SL RNA and RRM domain does not make extensive contacts with 5'SL RNA. We propose a model in which the initial recognition of 5'SL by LARP6 is mediated by the RNK epitope and further stabilized by the RRM domain. This discovery suggests that the interaction between LARP6 and collagen mRNAs can be blocked by small molecules that target the RNK epitope and will help rational design of the LARP6 binding inhibitors as specific antifibrotic drugs.

METHODS FOR QUANTITATIVE ASSESSMENT OF COLLAGEN ACCUMULATION PROCESSES IN DAMAGED TRAUMATIC INTEGUMENTARY TISSUES

OBJECTIVE

The aim: To study the level of expression of type I, III collagen under conditions of traumatic damage to integumentary tissues and to develop quantitative criteria for collagen formation processes for choosing the volume of reconstruction of a wound defect.

PATIENTS AND METHODS

Materials and methods: Studies were performed for 62 victims. Clinical group 1 (n = 16) - patients with wound surface sizes of the body surface area, group 2 (n = 32) consisted of patients who received integumentary tissue defects due to or together with damage osteoarticular apparatus of the limb, group 3 (n = 14) - patients with combined trauma.

RESULTS

Results: In the skin samples of patients of groups 1 and 2 of the affected groups, a statistically significant difference was established between the indicators of the relative accumulation area of type I, type III collagen (W = 675, p = 0.01 and W = 697, p = 0.03, respectively). In patients of groups 2 and 3, when analyzing relationships, a direct moderate strength was observed between the areas of collagen deposition of type I, type III (rs = 0.52 and 0.54). Collagen deposition coefficient (Кd) was used as a quantitative criterion for assessing the prognosis of the results of restoration of integumentary tissues according to the proposed scale, which made it possible to obtain postoperative complications in only 3.2 % of cases.

CONCLUSION

Conclusions: A positive treatment result taking into account the quantitative criterion (Kd) was obtained in 96.8 % of the examined patients.

Inhibitory Effect of Mitoxantrone on Collagen Synthesis in Dermal Fibroblasts

Background

Fibroblasts produce collagen molecules that support the structure of the skin. The decrease and hypersynthesis of collagen causes skin problems such as skin atrophy, wrinkles and scars.

Objective

The purpose of this study is to investigate the mechanism of mitoxantrone on collagen synthesis in fibroblasts.

Methods

Cultured fibroblasts were treated with mitoxantrone, and then collagen synthesis was confirmed by reverse transcription-polymerase chain reaction and Western blot.

Results

Mitoxantrone inhibited the expression of type I collagen in fibroblasts at both the mRNA and protein levels. In the collagen gel contraction assay, mitoxantrone significantly inhibited gel contraction compared to the control group. Mitoxantrone inhibited transforming growth factor (TGF)-β-induced phosphorylation of SMAD3. Finally, mitoxantrone inhibited the expression of LARP6, an RNA-binding protein that regulates collagen mRNA stability.

Conclusion

These results suggest that mitoxantrone reduces collagen synthesis by inhibiting TGF-β/SMAD signaling and LARP6 expression in fibroblasts, which can be developed as a therapeutic agent for diseases caused by collagen hypersynthesis.

Noncanonical ER-Golgi trafficking and autophagy of endogenous procollagen in osteoblasts

Secretion and quality control of large extracellular matrix proteins remain poorly understood and debated, particularly transport intermediates delivering folded proteins from the ER to Golgi and misfolded ones to lysosomes. Discrepancies between different studies are related to utilization of exogenous cargo, off-target effects of experimental conditions and cell manipulation, and identification of transport intermediates without tracing their origin and destination. To address these issues, here we imaged secretory and degradative trafficking of type I procollagen in live MC3T3 osteoblasts by replacing a region encoding N-propeptide in endogenous Col1a2 gDNA with GFP cDNA. We selected clones that produced the resulting fluorescent procollagen yet had normal expression of key osteoblast and ER/cell stress genes, normal procollagen folding, and normal deposition and mineralization of extracellular matrix. Live-cell imaging of these clones revealed ARF1-dependent transport intermediates, which had no COPII coat and delivered procollagen from ER exit sites (ERESs) to Golgi without stopping at ER-Golgi intermediate compartment (ERGIC). It also confirmed ERES microautophagy, i.e., lysosomes engulfing ERESs containing misfolded procollagen. Beyond validating these trafficking models for endogenous procollagen, we uncovered a probable cause of noncanonical cell stress response to procollagen misfolding. Recognized and retained only at ERESs, misfolded procollagen does not directly activate the canonical UPR, yet it disrupts the ER lumen by blocking normal secretory export from the ER.

LARP6 proteins in plants

RNA binding proteins, through control of mRNA fate and expression, are key players of organism development. The LARP family of RBPs sharing the La motif, are largely present in eukaryotes. They classify into five subfamilies which members acquired specific additional domains, including the RRM1 moiety which teams up with the La motif to form a versatile RNA binding unit. The LARP6 subfamily has had a peculiar history during plant evolution. While containing a single LARP6 in algae and non-vascular plants, they expanded and neofunctionalized into three subclusters in vascular plants. Studies from Arabidopsis thaliana, support that they acquired specific RNA binding properties and physiological roles. In particular LARP6C participates, through spatiotemporal control of translation, to male fertilization, a role seemingly conserved in maize. Interestingly, human LARP6 also acts in translation control and mRNA transport and similarly to LARP6C which is required for pollen tube guided elongation, is necessary to cell migration, through protrusion extension. This opens the possibility that some cellular and molecular functions of LARP6 were retained across eukaryote evolution. With their peculiar evolutionary history, plants provide a unique opportunity to uncover how La-module RNA binding properties evolved and identify species specific and basal roles of the LARP6 function. Deciphering of how LARP6, in particular LARP6C, acts at the molecular level, will foster novel knowledge on translation regulation and dynamics in changing cellular contexts. Considering the seemingly conserved function of LARP6C in male reproduction, it should fuel studies aimed at deriving crop species with improved seed yields.

Runt-related transcription factor-2 (Runx2) is required for bone matrix protein gene expression in committed osteoblasts in mice

Runt-related transcription factor-2 (Runx2) is an essential transcription factor for osteoblast differentiation. However, its functions after the commitment into osteoblasts are controversial and remain to be clarified. We generated enhanced green fluorescent protein (EGFP)-Cre transgenic mice driven by the 2.3-kilobase (kb) Col1a1 promoter, and Runx2 was deleted in osteoblasts and odontoblasts in Runx2^fl/flCre mice. The sutures and fontanelles were more widely opened in Runx2^fl/flCre newborns than in Runx2^fl/fl newborns. Runx2^fl/flCre mice exhibited dwarfism with shorter incisors and 37% had irregularly aligned incisors. The volume of trabecular bone in femurs and vertebrae and their bone mineral density (BMD), in addition to the cortical thickness and BMD were reduced in Runx2^fl/flCre mice compared with Runx2^fl/fl mice in both sexes. The bone formation of both trabecular and cortical bone, osteoblast number, osteoclast surface, osteoblast proliferation, and the serum levels of procollagen type 1 N-terminal propeptide (P1NP), tartrate-resistant acid phosphatase 5b (TRAP5b), and C-terminal cross-linked telopeptide of type 1 collagen (CTX1) were reduced in Runx2^fl/flCre mice. The expression of major bone matrix protein genes, including Col1a1, Col1a2, Spp1, Ibsp, and Bglap&Bglap2, and of Tnfsf11 was lower in Runx2^fl/flCre mice than in Runx2^fl/fl mice. The expression of Runx2 target genes, including Ihh, Fgfr1, Fgfr2, Fgfr3, Tcf7, Wnt10b, Pth1r, Sp7, and Dlx5, was also reduced. Osteoblasts in Runx2^fl/fl mice were cuboidal and contained abundant type I collagen α1 (Col1a1), whereas those in Runx2^fl/flCre mice were deflated and contained a small amount of Col1a1. Runx2 activated the reporter activity of the 2.3-kb Col1a1 promoter and bound the region around the Col1a1 transcription start site. The deletion of Runx2 by Cre-expressing adenovirus in Runx2^fl/fl primary osteoblasts impaired osteoblast differentiation and the expression of genes encoding major bone matrix proteins, and osteoclastogenesis was inhibited due to the reduction of Tnfsf11 expression in the osteoblasts. This study demonstrated that Runx2 is required for the expression of the major bone matrix protein genes and Tnfsf11 after commitment into osteoblasts in mice. © 2021 American Society for Bone and Mineral Research (ASBMR).

Single-cell and bulk transcriptomics of the liver reveals potential targets of NASH with fibrosis

Fibrosis is characterized by the excessive production of collagen and other extracellular matrix (ECM) components and represents a leading cause of morbidity and mortality worldwide. Previous studies of nonalcoholic steatohepatitis (NASH) with fibrosis were largely restricted to bulk transcriptome profiles. Thus, our understanding of this disease is limited by an incomplete characterization of liver cell types in general and hepatic stellate cells (HSCs) in particular, given that activated HSCs are the major hepatic fibrogenic cell population. To help fill this gap, we profiled 17,810 non-parenchymal cells derived from six healthy human livers. In conjunction with public single-cell data of fibrotic/cirrhotic human livers, these profiles enable the identification of potential intercellular signaling axes (e.g., ITGAV-LAMC1, TNFRSF11B-VWF and NOTCH2-DLL4) and master regulators (e.g., RUNX1 and CREB3L1) responsible for the activation of HSCs during fibrogenesis. Bulk RNA-seq data of NASH patient livers and rodent models for liver fibrosis of diverse etiologies allowed us to evaluate the translatability of candidate therapeutic targets for NASH-related fibrosis. We identified 61 liver fibrosis-associated genes (e.g., AEBP1, PRRX1 and LARP6) that may serve as a repertoire of translatable drug target candidates. Consistent with the above regulon results, gene regulatory network analysis allowed the identification of CREB3L1 as a master regulator of many of the 61 genes. Together, this study highlights potential cell-cell interactions and master regulators that underlie HSC activation and reveals genes that may represent prospective hallmark signatures for liver fibrosis.

What Mediates Fibrosis in the Tumor Microenvironment of Clear Renal Cell Carcinoma

Previous studies have demonstrated that direct targeting of interstitial cancer-associated fibroblasts (CAF) and tumor fibrosis alone seemed to be an unpromising treatment option for malignant tumors. Therefore, it is necessary to further explore the mechanism of the influence of collagen and tumor fibrosis on the biological behavior of malignant tumors. The current study aimed to explore the effect of intratumor fibrosis on the prognosis of renal clear cell carcinoma (ccRCC) and its mechanism. With the bioinformatic analysis of The Cancer Genome Atlas (TCGA) database (n = 537), the study showed that high Collagen type I α 1 (COL1A1) mRNA expression indicated the poor prognosis of ccRCC patients compared with low expression ones. We further used the Two-photon-excited fluorescence (TPEF)/second harmonic generation (SHG) microscopy to determine the intratumor fibrosis of 68 patients with surgical resection of ccRCC and confirmed that a high fibrosis level in the tumor was associated with a poor prognosis compared with patients with low expression (Progression-Free Survival: p = 0.030). We further measured the protein chips of 640 cytokines in ccRCC specimens and found that several cytokines, including prolactin (PRL), were associated with the degree of fibrosis in the tumor, as confirmed by the prolactin receptor (PRLR) immunohistochemical method. In addition, the study showed that PRLR expression decreased significantly in the ccRCC compared with adjacent normal tissue (p < 0.05). Our research shows that low expression of PRLR predicted the poor survival of the patient. We used the Cell Counting Kit-8 experiment, the transwell and the plate clone formation assay to evaluate the role of PRL in the 7860 and the ACHN cell lines. We found that PRL promoted ccRCC cell proliferation and migration. JAK-STAT3 activation was found in the high prolactin expression group by mass spectrum analysis. This study delineated the fibrosis-based tumor microenvironment characteristics of ccRCC. PRL/PRLR may be involved in the fibrosis process and are essential prognostic risk factors for ccRCC.

Hypusinated eIF5A is required for the translation of collagen

Translation of mRNAs that encode peptide sequences with consecutive prolines (polyproline) requires the conserved and essential elongation factor eIF5A to facilitate the formation of peptide bonds. It has been shown that, upon eIF5A depletion, yeast ribosomes stall in polyproline motifs, but also in tripeptide sequences that combine proline with glycine and charged amino acids. Mammalian collagens are enriched in putative eIF5A-dependent Pro-Gly-containing tripeptides. Here, we show that depletion of active eIF5A in mouse fibroblasts reduced collagen type I α1 chain (Col1a1) content, which concentrated around the nuclei. Moreover, it provoked the upregulation of endoplasmic reticulum (ER) stress markers, suggesting retention of partially synthesized collagen 1 (Col1) in the ER. We confirmed that eIF5A is needed for heterologous collagen synthesis in yeast and, using a double luciferase reporter system, showed that eIF5A depletion interrupts translation at Pro-Gly collagenic motifs. A dramatically lower level of Col1a1 protein was also observed in functional eIF5A-depleted human hepatic stellate cells treated with the profibrotic cytokine TGF-β1. In sum, our results show that collagen expression requires eIF5A and imply its potential as a target for regulating collagen production in fibrotic diseases.

LARP6C orchestrates posttranscriptional reprogramming of gene expression during hydration to promote pollen tube guidance

Increasing evidence suggests that posttranscriptional regulation is a key player in the transition between mature pollen and the progamic phase (from pollination to fertilization). Nonetheless, the actors in this messenger RNA (mRNA)-based gene expression reprogramming are poorly understood. We demonstrate that the evolutionarily conserved RNA-binding protein LARP6C is necessary for the transition from dry pollen to pollen tubes and the guided growth of pollen tubes towards the ovule in Arabidopsis thaliana. In dry pollen, LARP6C binds to transcripts encoding proteins that function in lipid synthesis and homeostasis, vesicular trafficking, and polarized cell growth. LARP6C also forms cytoplasmic granules that contain the poly(A) binding protein and possibly represent storage sites for translationally silent mRNAs. In pollen tubes, the loss of LARP6C negatively affects the quantities and distribution of storage lipids, as well as vesicular trafficking. In Nicotiana benthamiana leaf cells and in planta, analysis of reporter mRNAs designed from the LARP6C target MGD2 provided evidence that LARP6C can shift from a repressor to an activator of translation when the pollen grain enters the progamic phase. We propose that LARP6C orchestrates the timely posttranscriptional regulation of a subset of mRNAs in pollen during the transition from the quiescent to active state and along the progamic phase to promote male fertilization in plants.

LARP6C orchestrates posttranscriptional reprogramming of gene expression during hydration to promote pollen tube guidance

Increasing evidence suggests that posttranscriptional regulation is a key player in the transition between mature pollen and the progamic phase (from pollination to fertilization). Nonetheless, the actors in this messenger RNA (mRNA)-based gene expression reprogramming are poorly understood. We demonstrate that the evolutionarily conserved RNA-binding protein LARP6C is necessary for the transition from dry pollen to pollen tubes and the guided growth of pollen tubes towards the ovule in Arabidopsis thaliana. In dry pollen, LARP6C binds to transcripts encoding proteins that function in lipid synthesis and homeostasis, vesicular trafficking, and polarized cell growth. LARP6C also forms cytoplasmic granules that contain the poly(A) binding protein and possibly represent storage sites for translationally silent mRNAs. In pollen tubes, the loss of LARP6C negatively affects the quantities and distribution of storage lipids, as well as vesicular trafficking. In Nicotiana benthamiana leaf cells and in planta, analysis of reporter mRNAs designed from the LARP6C target MGD2 provided evidence that LARP6C can shift from a repressor to an activator of translation when the pollen grain enters the progamic phase. We propose that LARP6C orchestrates the timely posttranscriptional regulation of a subset of mRNAs in pollen during the transition from the quiescent to active state and along the progamic phase to promote male fertilization in plants.

ER-anchored CRTH2 antagonizes collagen biosynthesis and organ fibrosis via binding LARP6

Excessive deposition of extracellular matrix, mainly collagen protein, is the hallmark of organ fibrosis. The molecular mechanisms regulating fibrotic protein biosynthesis are unclear. Here, we find that chemoattractant receptor homologous molecule expressed on TH2 cells (CRTH2), a plasma membrane receptor for prostaglandin D2, is trafficked to the endoplasmic reticulum (ER) membrane in fibroblasts in a caveolin-1-dependent manner. ER-anchored CRTH2 binds the collagen mRNA recognition motif of La ribonucleoprotein domain family member 6 (LARP6) and promotes the degradation of collagen mRNA in these cells. In line, CRTH2 deficiency increases collagen biosynthesis in fibroblasts and exacerbates injury-induced organ fibrosis in mice, which can be rescued by LARP6 depletion. Administration of CRTH2 N-terminal peptide reduces collagen production by binding to LARP6. Similar to CRTH2, bumetanide binds the LARP6 mRNA recognition motif, suppresses collagen biosynthesis, and alleviates bleomycin-triggered pulmonary fibrosis in vivo. These findings reveal a novel anti-fibrotic function of CRTH2 in the ER membrane via the interaction with LARP6, which may represent a therapeutic target for fibrotic diseases.

Mutation of the 5'-untranslated region stem-loop mRNA structure reduces type I collagen deposition and arterial stiffness in male obese mice

Arterial stiffening, a characteristic feature of obesity and type 2 diabetes, contributes to the development and progression of cardiovascular diseases (CVD). Currently, no effective prophylaxis or therapeutics is available to prevent or treat arterial stiffening. A better understanding of the molecular mechanisms underlying arterial stiffening is vital to identify newer targets and strategies to reduce CVD burden. A major contributor to arterial stiffening is increased collagen deposition. In the 5'-untranslated regions of mRNAs encoding for type I collagen, an evolutionally conserved stem-loop (SL) structure plays an essential role in its stability and post-transcriptional regulation. Here, we show that feeding a high-fat/high-sucrose (HFHS) diet for 28 wk increases adiposity, insulin resistance, and blood pressure in male wild-type littermates. Moreover, arterial stiffness, assessed in vivo via aortic pulse wave velocity, and ex vivo using atomic force microscopy in aortic explants or pressure myography in isolated femoral and mesenteric arteries, was also increased in those mice. Notably, all these indices of arterial stiffness, along with collagen type I levels in the vasculature, were reduced in HFHS-fed mice harboring a mutation in the 5'SL structure, relative to wild-type littermates. This protective vascular phenotype in 5'SL-mutant mice did not associate with a reduction in insulin resistance or blood pressure. These findings implicate the 5'SL structure as a putative therapeutic target to prevent or reverse arterial stiffening and CVD associated with obesity and type 2 diabetes.NEW & NOTEWORTHY In the 5'-untranslated (UTR) regions of mRNAs encoding for type I collagen, an evolutionally conserved SL structure plays an essential role in its stability and posttranscriptional regulation. We demonstrate that a mutation of the SL mRNA structure in the 5'-UTR decreases collagen type I deposition and arterial stiffness in obese mice. Targeting this evolutionarily conserved SL structure may hold promise in the management of arterial stiffening and CVD associated with obesity and type 2 diabetes.

Chronic lung inflammation and pulmonary fibrosis after multiple intranasal instillation of PM2 .5 in mice

Fine particulate matter (PM_2.5 ) is an important component of air pollution and can induce lung inflammation and oxidative stress. We hypothesized that PM_2.5 could play a role in the induction of pulmonary fibrosis. We examined whether multiple intranasal instillation of PM_2.5 can induce pulmonary fibrosis in the mouse, and also investigated the underlying pro-fibrotic signaling pathways. C57/BL6 mice were intranasally instilled with 50 μl of PM_2.5 suspension (7.8 μg/g body weight) or PBS three times a week over 3 weeks, 6 weeks or 9 weeks. To observe the recovery of pulmonary fibrosis after the termination of PM_2.5 exposure, 9 week-PM_2.5 instilled mice were also studied at 3 weeks after termination of instillation. There were significant decreases in total lung capacity (TLC) and compliance (Cchord) in the 9-week PM_2.5 -instilled mice, while there were increased histological fibrosis scores with enhanced type I collagen and hydroxyproline deposition, increased mitochondrial ROS levels and NOX activity, decreased total SOD and GSH levels, accompanied by decreased mitochondrial number and aberrant mitochondrial morphology (swelling, vacuolization, cristal disruption, reduced matrix density) in PM_2.5 -instilled mice. Multiple PM_2.5 instillation resulted in increased expression of TGFβ1, increases of N-Cadherin and Vimentin and a decrease of E-Cadherin. It also led to decreases in OPA1 and MFN2, and increases in Parkin, SQSTM1/p62, the ratio of light china (LC) 3B II to LC3B I, PI3k/Akt phosphorylation, and NLRP3 expression. Intranasal instillation of PM_2.5 for 9 weeks induced lung inflammation and pulmonary fibrosis, which was linked with aberrant epithelial-mesenchymal transition, oxidative stress, mitochondrial damage and mitophagy, as well as activation of TGFβ1-PI3K/Akt, TGFβ1- NOX and TGFβ1-NLRP3 pathways.

Imaging of type I procollagen biosynthesis in cells reveals biogenesis in highly organized bodies; Collagenosomes

Mechanistic aspects of type I procollagen biosynthesis in cells are poorly understood. To provide more insight into this process we designed a system to directly image type I procollagen biogenesis by co-expression of fluorescently labeled full size procollagen α1(I) and one α2(I) polypeptides. High resolution images show that collagen α1(I) and α2(I) polypeptides are produced in coordination in discrete structures on the ER membrane, which we termed the collagenosomes. Collagenosomes are disk shaped bodies, 0.5-1 μM in diameter and 200-400 nm thick, in the core of which folding of procollagen takes place. Collagenosomes are intimately associated with the ER membrane and their formation requires intact translational machinery, suggesting that they are the sites of nascent procollagen biogenesis. Collagenosomes show little co-localization with the COPII transport vesicles, which export type I procollagen from the ER, suggesting that these two structures are distinct. LARP6 is the protein which regulates translation of type I collagen mRNAs. The characteristic organization of collagenosomes depends on binding of LARP6 to collagen mRNAs. Without LARP6 regulation, collagenosomes are poorly organized and the folding of α1(I) and α2(I) polypeptides into procollagen in their cores is diminished. This indicates that formation of collagenosomes is dependent on regulated translation of collagen mRNAs. In live cells the size, number and shape of collagenosomes show little change within several hours, suggesting that they are stable structures of type I procollagen biogenesis. This is the first report of structural organization of type I collagen biogenesis in collagenosomes, while the fluorescent reporter system based on simultaneous imaging of both type I collagen polypeptides will enable the detailed elucidation of their structure and function.

Cytoplasmic polyadenylation by TENT5A is required for proper bone formation

Osteoblasts orchestrate bone formation through the secretion of type I collagen and other constituents of the matrix on which hydroxyapatite crystals mineralize. Here, we show that TENT5A, whose mutations were found in congenital bone disease osteogenesis imperfecta patients, is a cytoplasmic poly(A) polymerase playing a crucial role in regulating bone mineralization. Direct RNA sequencing revealed that TENT5A is induced during osteoblast differentiation and polyadenylates mRNAs encoding Col1α1, Col1α2, and other secreted proteins involved in osteogenesis, increasing their expression. We postulate that TENT5A, possibly together with its paralog TENT5C, is responsible for the wave of cytoplasmic polyadenylation of mRNAs encoding secreted proteins occurring during bone mineralization. Importantly, the Tent5a knockout (KO) mouse line displays bone fragility and skeletal hypomineralization phenotype resulting from quantitative and qualitative collagen defects. Thus, we report a biologically relevant posttranscriptional regulator of collagen production and, more generally, bone formation.

Discovery of a Lead Compound for Specific Inhibition of Type I Collagen Production in Fibrosis

Fibrosis is a major medical problem caused by excessive synthesis of the extracellular matrix, composed predominantly of type I collagen, in various tissues. There are no approved antifibrotic drugs, and the major obstacle in finding clinically relevant compounds is the lack of specificity of current experimental drugs for type I collagen. Here we describe the discovery of a lead compound that specifically inhibited secretion of type I collagen by fibroblasts in culture at IC₅₀ = 4.5 μM. The inhibition was specific for type I collagen, because secretion of fibronectin was not affected. In vitro, the compound inhibited binding of LARP6, the master regulator of translation of type I collagen mRNAs, to the 5' stem-loop sequence element which regulates their translation. Because binding of LARP6 to collagen mRNAs is crucial for the development of fibrosis, this inhibitor represents a promising lead for optimization into specific antifibrotic drugs.

Distribution, organization an evolutionary history of La and LARPs in eukaryotes

The fate of any cellular RNA is largely influenced by the nature and diversity of its interactions with various RNA-binding proteins (RBPs) leading to the formation of a biologically significant ribonucleoprotein (RNP) complex. La motif-containing proteins (composed of genuine La and La-related proteins (LARPs)) represent an evolutionary conserved family of RBPs that encompass a large range of crucial functions, involving coding and non-coding RNAs. In this work, we provide data that extend our previous knowledge on the distribution, organization and evolutionary history of this important protein family. Using a repertoire of 345 La motif-containing proteins from 135 species representing all major eukaryotic lineages, we were able to pinpoint many lineage-specific variations in the structural organization of La and LARPs and propose new evolutive scenarios to explain their modern genomic distribution.

Force dependent effects of chronic overuse on fibrosis-related genes and proteins in skeletal muscles

AIM

To examine the chronic effect of force on mRNA and protein expression levels of fibrosis-related genes in flexor digitorum muscles in a rat model of repetitive overuse injury that induces muscle fibrosis at high force levels.

MATERIALS AND METHODS

Two groups of rats were trained to perform a voluntary repetitive lever-pulling task at either a high (HFHR) or a low force (LFHR) for 18 weeks, while a control group (FRC) performed no task. RNA and protein were prepared from forelimb flexor digitorum muscles. Fibrosis-related gene RNA transcripts were evaluated using quantitative PCR (qPCR) and analyzed using the geometric mean of three housekeeping genes or the mean of each individually as reference. Protein levels were quantified using ELISA, western blot, or immunohistofluorescence.

RESULTS

Of eight fibrosis-related mRNAs examined, only FGF2 demonstrated a consistent significant increase in the HFHR group, compared to the FRC group. However, protein amounts of collagen type 1, collagen type 3, and TGFβ1 were significantly higher in the HFHR, compared to the FRC and LFHR groups, while CCN2 and FGF2 were higher in both HFHR and LFHR, compared to the FRC group.

CONCLUSIONS

Our results suggest that there is steady-state transcription of fibrogenic genes in muscles with established fibrosis, implying that post-transcriptional processes are responsible for the increased protein levels of fibrotic factors during muscle overuse conditions. We hypothesize that targeting such pathways represents a valid approach to treat overuse injury. Alternatively, FGF2 gene expression may represent a valid target for therapy.

Collagen I Induces Preeclampsia-Like Symptoms by Suppressing Proliferation and Invasion of Trophoblasts

Preeclampsia is a common obstetric disorder affecting 2-8% of pregnancy worldwide. Fibrosis is an important histological change occurring in preeclamptic placenta, and might depend on the excess deposition of collagen I. However, the role of fibrotic placenta and collagen I in the pathogenesis of preeclampsia remains unclear. Therefore, we analyzed the collagen deposition and the expression of Collagen I in human placenta by Masson staining, Sirius red staining and western blotting. Further, the role of collagen I in preeclampsia pathogenesis was studied in C57BL/6 mice. HTR-8/SVneo cells were used to investigate the mechanisms underlying the effects of collagen I in trophoblasts by transcriptome sequencing and pharmacological agonists. Human preeclamptic placenta exhibited a significantly higher degree of fibrosis in stem villi and terminal villi than normal placenta, and was characterized by collagen I deposition. In vivo, a single injection of collagen I on gestational day 0.5 led to an increase in systolic pressure of pregnant mice from gestational days 4.5-17.5, to a decrease in weight and number of embryos, and to enhanced placental collagen I expression and degree of fibrosis compared with control mice. In vitro, collagen I attenuated the proliferation and invasion of HTR-8SV/neo cells. This effect could be reversed by treatment with agonists of ERK and β-catenin. Moreover, transcriptome sequencing demonstrated that signaling pathways related to cell proliferation and invasion were significantly downregulated in HTR-8SV/neo cells. Thus, we propose that collagen I induced preeclampsia-like symptoms by suppressing the proliferation and invasion of trophoblasts through inhibition of the ERK phosphorylation and WNT/β-catenin signaling pathways. Our findings could pave the way to the discovery of small-molecule inhibitors for preeclampsia treatment and future studies with larger sample size are required.

Low Basal CB2R in Dopamine Neurons and Microglia Influences Cannabinoid Tetrad Effects

There are two well-characterized cannabinoid receptors (CB1R and CB2R and other candidates): the central nervous system (CNS) enriched CB1R and peripheral tissue enriched CB2R with a wide dynamic range of expression levels in different cell types of human tissues. Hepatocytes and neurons express low baseline CB1R and CB2R, respectively, and their cell-type-specific functions are not well defined. Here we report inducible expression of CB1R in the liver by high-fat and high sugar diet and CB2R in cortical neurons by methamphetamine. While there is less controversy about hepatocyte CB1R, the presence of functional neuronal CB2R is still debated to date. We found that neuron CB2R basal expression was higher than that of hepatocyte CB1R by measuring mRNA levels of specific isoform CB2A in neurons isolated by fluorescence-activated cell sorting (FACS) and CB1A in hepatocytes isolated by collagenase perfusion of liver. For in vivo studies, we generated hepatocyte, dopaminergic neuron, and microglia-specific conditional knockout mice (Abl-Cnr1Δ, Dat-Cnr2Δ, and Cx3cr1-Cnr2Δ) of CB1R and CB2R by crossing Cnr1f/f and Cnr2f/f strains to Abl-Cre, Dat-Cre, and Cx3cr1-Cre deleter mouse strains, respectively. Our data reveals that neuron and microglia CB2Rs are involved in the "tetrad" effects of the mixed agonist WIN 55212-2, CB1R selective agonist arachidonyl-2'-chloroethylamide (ACEA), and CB2R selective agonist JWH133. Dat-Cnr2Δ and Cx3cr1-Cnr2Δ mice showed genotypic differences in hypomobility, hypothermia, analgesia, and catalepsy induced by the synthetic cannabinoids. Alcohol conditioned place preference was abolished in DAT-Cnr2Δ mice and remained intact in Cx3cr1-Cnr2Δ mice in comparison to WT mice. These Cre-loxP recombinant mouse lines provide unique approaches in cannabinoid research for dissecting the complex endocannabinoid system that is implicated in many chronic disorders.

β1 integrin, ILK and mTOR regulate collagen synthesis in mechanically loaded tendon cells

Tendons are specialized tissues composed primarily of load-responsive fibroblasts (tenocytes) embedded in a collagen-rich extracellular matrix. Habitual mechanical loading or targeted exercise causes tendon cells to increase the stiffness of the extracellular matrix; this adaptation may occur in part through collagen synthesis or remodeling. Integrins are likely to play an important role in transmitting mechanical stimuli from the extracellular matrix to tendon cells, thereby triggering cell signaling pathways which lead to adaptive regulation of mRNA translation and protein synthesis. In this study, we discovered that mechanical stimulation of integrin β1 leads to the phosphorylation of AKT, an event which required the presence of integrin-linked kinase (ILK). Repetitive stretching of tendon cells activates the AKT and mTOR pathways, which in turn regulates mRNA translation and collagen expression. These results support a model in which integrins are an upstream component of the mechanosensory cellular apparatus, regulating fundamental tendon cell functions relevant to exercise-induced adaptation and mechanotherapy.

Transcriptome profile analysis reveals a silica-induced immune response and fibrosis in a silicosis rat model

Silicosis is a type of pneumoconiosis caused by the inhalation of silica dust. It is characterized by inflammation and fibrosis of the lung. Although many studies have reported that crystalline silica-inhalation into the lung initiates the immune response, activating effector cells and triggering the inflammatory cascade with subsequent elaboration of the extracellular matrix and fibrosis, the mechanism of silicosis pathogenesis remains unclear. In the present study, we established a silica inhalation-induced silicosis rat model validated by histological and cytokine analyses. RNA-seq and bioinformatic analyses showed that 600 genes were upregulated and 537 genes were downregulated in the silica-treated group. GO enrichment analysis indicates that these differentially expressed genes are enriched in several biological processes including immune response and organism remodeling. KEGG enrichment analysis showed that 53 enriched pathways were mainly associated with human diseases, immune response, signal transduction, and fibrosis process. Since alternative splicing of pre-mRNAs is also essential for the regulation of gene expression, we identified several alternative pre-mRNA splicing events in the fibrotic process. This study will provide a foundation to understand the molecular mechanism of the pulmonary fibrosis caused by silica.

Crystal Structure of a Variant PAM2 Motif of LARP4B Bound to the MLLE Domain of PABPC1

Eukaryotic cells determine the protein output of their genetic program by regulating mRNA transcription, localization, translation and turnover rates. This regulation is accomplished by an ensemble of RNA-binding proteins (RBPs) that bind to any given mRNA, thus forming mRNPs. Poly(A) binding proteins (PABPs) are prominent members of virtually all mRNPs that possess poly(A) tails. They serve as multifunctional scaffolds, allowing the recruitment of diverse factors containing a poly(A)-interacting motif (PAM) into mRNPs. We present the crystal structure of the variant PAM motif (termed PAM2w) in the N-terminal part of the positive translation factor LARP4B, which binds to the MLLE domain of the poly(A) binding protein C1 cytoplasmic 1 (PABPC1). The structural analysis, along with mutational studies in vitro and in vivo, uncovered a new mode of interaction between PAM2 motifs and MLLE domains.

Maternal Larp6 controls oocyte development, chorion formation and elevation

La-related protein 6 (Larp6) is a conserved RNA-binding protein found across eukaryotes that has been suggested to regulate collagen biogenesis, muscle development, ciliogenesis, and various aspects of cell proliferation and migration. Zebrafish have two Larp6 family genes: larp6a and larp6b Viable and fertile single and double homozygous larp6a and larp6b zygotic mutants revealed no defects in muscle structure, and were indistinguishable from heterozygous or wild-type siblings. However, larp6a mutant females produced eggs with chorions that failed to elevate fully and were fragile. Eggs from larp6b single mutant females showed minor chorion defects, but chorions from eggs laid by larp6a;larp6b double mutant females were more defective than those from larp6a single mutants. Electron microscopy revealed defective chorionogenesis during oocyte development. Despite this, maternal zygotic single and double mutants were viable and fertile. Mass spectrometry analysis provided a description of chorion protein composition and revealed significant reductions in a subset of zona pellucida and lectin-type proteins between wild-type and mutant chorions that paralleled the severity of the phenotype. We conclude that Larp6 proteins are required for normal oocyte development, chorion formation and egg activation.

Technology for Discovery of Antifibrotic Drugs: Phenotypic Screening for LARP6 Inhibitors Using Inverted Yeast Three Hybrid System

Fibrosis is defined by excessive production of type I collagen in various organs. Excessive type I collagen production in fibrosis is stimulated by binding of RNA protein LARP6 to the structural element of collagen mRNAs, the 5' stem loop (5'SL). The LARP6-dependent regulation is specific for type I collagen and critical for fibrosis development. Inhibitors of LARP6 binding have potential to be specific antifibrotic drugs, as evidenced by the discovery of one such inhibitor. To create technology for phenotypic screening of additional compounds we developed an inverted yeast three hybrid system. The system is based on expression of human LARP6 and a short RNA containing the 5'SL of human collagen α1(I) mRNA in Saccharomyces cerevisiae cells. The cells were engineered in such a way that when LARP6 is bound to 5'SL RNA they fail to grow in a specific synthetic medium. Dissociation of LARP6 from 5'SL RNA permits the cell growth, allowing identification of the inhibitors of LARP6 binding. The assay simply involves measuring optical density of cells growing in multiwall plates and is pertinent for high throughput applications. We describe the specificity of the system and its characteristics for high throughput screening. As a proof of principle, the result of one screen using collection of FDA approved drugs is also presented. This screen demonstrates that using this technology discovery of novel LARP6 inhibitors is possible.

Discovery and evaluation of inhibitor of LARP6 as specific antifibrotic compound

Fibrosis is characterized by excessive production of type I collagen. Biosynthesis of type I collagen in fibrosis is augmented by binding of protein LARP6 to the 5' stem-loop structure (5'SL), which is found exclusively in type I collagen mRNAs. A high throughput screen was performed to discover inhibitors of LARP6 binding to 5'SL, as potential antifibrotic drugs. The screen yielded one compound (C9) which was able to dissociate LARP6 from 5' SL RNA in vitro and to inactivate the binding of endogenous LARP6 in cells. Treatment of hepatic stellate cells (liver cells responsible for fibrosis) with nM concentrations of C9 reduced secretion of type I collagen. In precision cut liver slices, as an ex vivo model of hepatic fibrosis, C9 attenuated the profibrotic response at 1 μM. In prophylactic and therapeutic animal models of hepatic fibrosis C9 prevented development of fibrosis or hindered the progression of ongoing fibrosis when administered at 1 mg/kg. Toxicogenetics analysis revealed that only 42 liver genes changed expression after administration of C9 for 4 weeks, suggesting minimal off target effects. Based on these results, C9 represents the first LARP6 inhibitor with significant antifibrotic activity.

Visualization of specific collagen-producing cells by Col1-GFP transgenic mice revealed novel type I collagen-producing cells other than fibroblasts in systemic organs/tissues

Type I collagen is one of the most abundant proteins in mammals and plays important roles in maintaining the integrity of many tissues. Although fibroblasts are the main source of type I collagen, other cells also produce it; however, these cells are not well-defined owing to the lack of a specific marker. A transgenic (Tg) mouse line has been generated in which type I collagen-producing cells are labeled with enhanced green fluorescent protein (EGFP), which enables the monitoring of these cells without requiring an additional cell marker. This Tg mouse line has since been widely used to study type I collagen-producing cells and fibrosis; one study revealed that podocytes, which were not previously considered to produce type I collagen, expressed EGFP. This raises a question regarding the specificity of EGFP expression in this Tg mouse line. To exclude the possibility of non-specific EGFP expression in the existing Tg mouse line and specifically monitor type I collagen-producing cells, we generated a new Tg mouse line and histologically confirmed the specificity of EGFP expression throughout the body. Moreover, we explored type I collagen-producing cells other than fibroblasts and revealed for the first time that Leydig cells have the ability to produce type I collagen. Because of its highly specific and physiologically accurate expression, our new Tg mouse line will help to accurately elucidate not only type I collagen-producing cells in normal tissues but also the potential cells in fibrotic tissues, providing new insights into the pathology of fibrosis.