Collagens in the liver extracellular matrix bind hepatocyte growth factor

Type 1 collagen: Synthesis, structure and key functions in bone mineralization

Collagen is a highly abundant protein in the extracellular matrix of humans and mammals, and it plays a critical role in maintaining the body's structural integrity. Type I collagen is the most prevalent collagen type and is essential for the structural integrity of various tissues. It is present in nearly all connective tissues and is the main constituent of the interstitial matrix. Mutations that affect collagen fiber formation, structure, and function can result in various bone pathologies, underscoring the significance of collagen in sustaining healthy bone tissue. Studies on type 1 collagen have revealed that mutations in its encoding gene can lead to diverse bone diseases, such as osteogenesis imperfecta, a disorder characterized by fragile bones that are susceptible to fractures. Knowledge of collagen's molecular structure, synthesis, assembly, and breakdown is vital for comprehending embryonic and foetal development and several aspects of human physiology. In this review, we summarize the structure, molecular biology of type 1 collagen, its biomineralization and pathologies affecting bone.

Effects of Topography and PDGF on the Response of Corneal Keratocytes to Fibronectin-Coated Surfaces

During corneal wound healing, corneal keratocytes are exposed to both biophysical and soluble cues that cause them to transform from a quiescent state to a repair phenotype. How keratocytes integrate these multiple cues simultaneously is not well understood. To investigate this process, primary rabbit corneal keratocytes were cultured on substrates patterned with aligned collagen fibrils and coated with adsorbed fibronectin. After 2 or 5 days of culture, keratocytes were fixed and stained to assess changes in cell morphology and markers of myofibroblastic activation by fluorescence microscopy. Initially, adsorbed fibronectin had an activating effect on the keratocytes as evidenced by changes in cell shape, stress fiber formation, and expression of alpha-smooth muscle actin (α-SMA). The magnitude of these effects depended upon substrate topography (i.e., flat substrate vs aligned collagen fibrils) and decreased with culture time. When keratocytes were simultaneously exposed to adsorbed fibronectin and soluble platelet-derived growth factor-BB (PDGF-BB), the cells elongated and had reduced expression of stress fibers and α-SMA. In the presence of PDGF-BB, keratocytes plated on the aligned collagen fibrils elongated in the direction of the fibrils. These results provide new information on how keratocytes respond to multiple simultaneous cues and how the anisotropic topography of aligned collagen fibrils influences keratocyte behavior.

Integrated proteome sequencing, bulk RNA sequencing and single-cell RNA sequencing to identify potential biomarkers in different grades of intervertebral disc degeneration

Low back pain (LBP) is a prevalent health problem worldwide that affects over 80% of adults during their lifetime. Intervertebral disc degeneration (IDD) is a well-recognized leading cause of LBP. IDD is classified into five grades according to the Pfirrmann classification system. The purpose of this study was to identify potential biomarkers in different IDD grades through an integrated analysis of proteome sequencing (PRO-seq), bulk RNA sequencing (bRNA-seq) and single-cell RNA sequencing (scRNA-seq) data. Eight cases of grade I-IV IDD were obtained. Grades I and II were considered non-degenerative discs (relatively normal), whereas grades III and IV were considered degenerative discs. PRO-seq analysis was performed to identify differentially expressed proteins (DEPs) in various IDD grades. Variation analysis was performed on bRNA-seq data to differentiate expressed genes (DEGs) in normal and degenerated discs. In addition, scRNA-seq was performed to validate DEGs in degenerated and non-degenerated nucleus pulposus (NP). Machine learning (ML) algorithms were used to screen hub genes. The receiver operating characteristic (ROC) curve was used to validate the efficiency of the screened hub genes to predict IDD. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to analyze function enrichment and signaling pathways. Protein-protein interaction (PPI) network was used to prioritize disease-related proteins. SERPINA1, ORM2, FGG and COL1A1 were identified through PRO-seq as the hub proteins involved in regulating IDD. ML algorithms selected ten hub genes, including IBSP, COL6A2, MMP2, SERPINA1, ACAN, FBLN7, LAMB2, TTLL7, COL9A3, and THBS4 in bRNA-seq. Since serine protease inhibitor clade A member 1 (SERPINA1) was the only common gene, its accuracy in degenerated and non-degenerated NP cells was validated using scRNA-seq. Then, the rat degeneration model of caudal vertebra was established. The expression of SERPINA1 and ORM2 was detected using immunohistochemical staining of human and rat intervertebral discs. The results showed that SERPINA1 was poorly expressed in the degenerative group. We further explored the potential function of SERPINA1 by Gene Set Enrichment Analysis (GSEA) and cell-cell communication. Therefore, SERPINA1 can be used as a biomarker to regulate or predict the progress of disc degeneration.

Two-Chain Mature Hepatocyte Growth Factor-Specific Positron Emission Tomography Imaging in Tumors Using 64Cu-Labeled HiP-8, a Nonstandard Macrocyclic Peptide Probe

Two-chain hepatocyte growth factor (tcHGF), the mature form of HGF, is associated with malignancy and anticancer drug resistance; therefore, its quantification is an important indicator for cancer diagnosis. In tumors, activated tcHGF hardly discharges into the systemic circulation, indicating that tcHGF is an excellent target for molecular imaging using positron emission tomography (PET). We recently discovered HGF-inhibitory peptide-8 (HiP-8) that binds specifically to human tcHGF with nanomolar affinity. The purpose of this study was to investigate the usefulness of HiP-8-based PET probes in human HGF knock-in humanized mice. ⁶⁴Cu-labeled HiP-8 molecules were synthesized using a cross-bridged cyclam chelator, CB-TE1K1P. Radio-high-performance liquid chromatography-based metabolic stability analyses showed that more than 90% of the probes existed in intact form in blood at least for 15 min. In PET studies, significantly selective visualization of hHGF-overexpressing tumors versus hHGF-negative tumors was observed in double-tumor-bearing mice. The accumulation of labeled HiP-8 into the hHGF-overexpressing tumors was significantly reduced by competitive inhibition. In addition, the radioactivity and distribution of phosphorylated MET/HGF receptor were colocalized in tissues. These results demonstrate that the ⁶⁴Cu-labeled HiP-8 probes are suitable for tcHGF imaging in vivo, and secretory proteins like tcHGF can be a target for PET imaging.

The role of hepatic microenvironment in hepatic fibrosis development

AIM

Fibrosis is a common pathological feature of most types of chronic liver injuries. There is no specific treatment for liver fibrosis at present. The liver microenvironment, which fosters the survival and activity of liver cells, plays an important role in maintaining the normal structure and physiological function of the liver. The aim of this review is to deeply understand the role of the liver microenvironment in the dynamic and complicated development of liver fibrosis.

METHODS

After searching in Elsevier ScienceDirect, PubMed and Web of Science databases using 'liver fibrosis' and 'microenvironment' as keywords, studies related to microenvironment in liver fibrosis was compiled and examined.

RESULTS

The homeostasis of the liver microenvironment is disrupted during the development of liver fibrosis, affecting liver cell function, causing various types of cell reactions, and changing the cell-cell and cell-matrix interactions, eventually affecting fibrosis formation.

CONCLUSION

Liver microenvironment may be important for identifying potential therapeutic targets, and restoring microenvironment homeostasis may be an important strategy for promoting the reversal of liver fibrosis.KEY MESSAGESThe homeostasis of the liver microenvironment is disrupted in liver fibrosis;A pro-fibrotic microenvironment is formed during the development of liver fibrosis;Restoring microenvironment homeostasis may be an important strategy for promoting the reversal of liver fibrosis.

Liver regeneration biology: Implications for liver tumour therapies

The liver has remarkable regenerative potential, with the capacity to regenerate after 75% hepatectomy in humans and up to 90% hepatectomy in some rodent models, enabling it to meet the challenge of diverse injury types, including physical trauma, infection, inflammatory processes, direct toxicity, and immunological insults. Current understanding of liver regeneration is based largely on animal research, historically in large animals, and more recently in rodents and zebrafish, which provide powerful genetic manipulation experimental tools. Whilst immensely valuable, these models have limitations in extrapolation to the human situation. In vitro models have evolved from 2-dimensional culture to complex 3 dimensional organoids, but also have shortcomings in replicating the complex hepatic micro-anatomical and physiological milieu. The process of liver regeneration is only partially understood and characterized by layers of complexity. Liver regeneration is triggered and controlled by a multitude of mitogens acting in autocrine, paracrine, and endocrine ways, with much redundancy and cross-talk between biochemical pathways. The regenerative response is variable, involving both hypertrophy and true proliferative hyperplasia, which is itself variable, including both cellular phenotypic fidelity and cellular trans-differentiation, according to the type of injury. Complex interactions occur between parenchymal and non-parenchymal cells, and regeneration is affected by the status of the liver parenchyma, with differences between healthy and diseased liver. Finally, the process of termination of liver regeneration is even less well understood than its triggers. The complexity of liver regeneration biology combined with limited understanding has restricted specific clinical interventions to enhance liver regeneration. Moreover, manipulating the fundamental biochemical pathways involved would require cautious assessment, for fear of unintended consequences. Nevertheless, current knowledge provides guiding principles for strategies to optimise liver regeneration potential.

Influence of cytokines, circulating markers and growth factors on liver regeneration and post-hepatectomy liver failure: a systematic review and meta-analysis

The pathophysiology of post-hepatectomy liver failure is not entirely understood but is rooted in the disruption of normal hepatocyte regeneration and homeostasis. Current investigations of post-hepatectomy liver failure and regeneration are focused on evaluation of circulating hepatic function parameters (transaminases, cholestasis, and coagulation parameters), volumetry and hepatic hemodynamics. However, identification of biochemical factors associated with regeneration and post hepatectomy liver failure is crucial for understanding the pathophysiology and identification of patients at risk. The objective of the present systematic review was to identify circulating factors associated with liver regeneration and post hepatectomy liver failure in patients undergoing hepatectomy. The quantitative analysis was intended if studies provided sufficient data. Electronic databases (MEDLINE via PubMed, Web of Knowledge, Cochrane Library and WHO International Clinical Trials Registry Platform) were searched for publications on cell signaling factors in liver regeneration and post-hepatectomy liver failure following liver resection in clinical setting. No date restriction was given. No language restriction was used. Studies were assessed using MINORS. This study was registered at PROSPERO (CRD42020165384) prior to data extraction. In total 1953 publications were evaluated for titles and abstracts after exclusion of duplicates. Full texts of 167 studies were further evaluated for inclusion. 26 articles were included in the review and 6 publications were included in the meta-analyses. High levels of serum hyaluronic acid even preoperatively are associated with PHLF but especially increased levels early after resection are predictive of PHLF with high sensitivity and specificity. Postoperative elevation of HA to levels between 100 and 500 ng/ml is increased the risk for PHLF ([OR] = 246.28, 95% [CI]: 11.82 to 5131.83; p = 0.0004) Inteleukin-6 levels show contradicting result in association with organ dysfunction. HGF positively correlates with liver regeneration. Overall, due to heterogeneity, scarcity, observational study design and largely retrospective analysis, the certainty of evidence, assessed with GRADE, is very low. High levels of serum hyaluronic acid show a strong association with PHLF and increased levels after resection are predictive of PHLF with high sensitivity and specificity, even on POD1. Interleukin-6 levels need to be studied further due to contradictive results in association with organ dysfunction. For HGF, no quantitative analysis could be made. Yet, most studies find positive correlation between high HGF levels and regeneration. Prospective studies investigating HGF and other growth factors, hyaluronic acid and interleukins 1 and 6 in correlation with liver regeneration measured sequentially through e.g. volumetry, and liver function parameters, preferably expanding the analysis to include dynamic liver function tests, are needed to sufficiently illustrate the connection between biomolecule levels and clinical outcomes.

Matrix adhesion and remodeling diversifies modes of cancer invasion across spatial scales

The metastasis of malignant epithelial tumors begins with the egress of transformed cells from the confines of their basement membrane (BM) to their surrounding collagen-rich stroma. Invasion can be morphologically diverse: when breast cancer cells are separately cultured within BM-like matrix, collagen I (Coll I), or a combination of both, they exhibit collective-, dispersed mesenchymal-, and a mixed collective-dispersed (multimodal)- invasion, respectively. In this paper, we asked how distinct these invasive modes are with respect to the cellular and microenvironmental cues that drive them. A rigorous computational exploration of invasion was performed within an experimentally motivated Cellular Potts-based modeling environment. The model comprised of adhesive interactions between cancer cells, BM- and Coll I-like extracellular matrix (ECM), and reaction-diffusion-based remodeling of ECM. The model outputs were parameters cognate to dispersed- and collective- invasion. A clustering analysis of the output distribution curated through a careful examination of subsumed phenotypes suggested at least four distinct invasive states: dispersed, papillary-collective, bulk-collective, and multimodal, in addition to an indolent/non-invasive state. Mapping input values to specific output clusters suggested that each of these invasive states are specified by distinct input signatures of proliferation, adhesion and ECM remodeling. In addition, specific input perturbations allowed transitions between the clusters and revealed the variation in the robustness between the invasive states. Our systems-level approach proffers quantitative insights into how the diversity in ECM microenvironments may steer invasion into diverse phenotypic modes during early dissemination of breast cancer and contributes to tumor heterogeneity.

Diverse and Productive Source of Biopolymer Inspiration: Marine Collagens

Marine biodiversity is expressed through the huge variety of vertebrate and invertebrate species inhabiting intertidal to deep-sea environments. The extraordinary variety of "forms and functions" exhibited by marine animals suggests they are a promising source of bioactive molecules and provides potential inspiration for different biomimetic approaches. This diversity is familiar to biologists and has led to intensive investigation of metabolites, polysaccharides, and other compounds. However, marine collagens are less well-known. This review will provide detailed insight into the diversity of collagens present in marine species in terms of their genetics, structure, properties, and physiology. In the last part of the review the focus will be on the most common marine collagen sources and on the latest advances in the development of innovative materials exploiting, or inspired by, marine collagens.

Hepatic stellate cells - from past till present: morphology, human markers, human cell lines, behavior in normal and liver pathology

Hepatic stellate cell (HSC), initially analyzed by von Kupffer, in 1876, revealed to be an extraordinary mesenchymal cell, essential for both hepatocellular function and lesions, being the hallmark of hepatic fibrogenesis and carcinogenesis. Apart from their implications in hepatic injury, HSCs play a vital role in liver development and regeneration, xenobiotic response, intermediate metabolism, and regulation of immune response. In this review, we discuss the current state of knowledge regarding HSCs morphology, human HSCs markers and human HSC cell lines. We also summarize the latest findings concerning their roles in normal and liver pathology, focusing on their impact in fibrogenesis, chronic viral hepatitis and liver tumors.

Challenges and effective routes for formulating and delivery of epidermal growth factors in skin care

Epidermal growth factors are important morphogenetic proteins that instruct cell behaviour. They have many inferred applications within regenerative medicine and have shown promising results in skincare treatments. Many growth factors are known to have skin anti-ageing benefits along with further potential in resolving scarring, acne and other skin disorders. Incorporation of these biologics into skincare formulations has been greatly hindered by low transdermal delivery efficacy, intricate material interactions and protein instability - especially within common cosmetic emulsions. This review explores the cosmeceutical capability of growth factors in skin care, current understandings of constituent interactions and advantageous delivery approaches for more effective topical delivery. The first section highlights the influences growth factor product formulation has on stability and synergy. Current understandings of growth factor formulating techniques in cosmetic products is limited, and the performance of other protein structures is an adequate point of reference. The second section examines emerging drug delivery systems to overcome the challenges of topical growth factor treatment. It is important to consider the coaction and durability of all components in a formulation simultaneously: active ingredients, product format and delivery vehicle, in order to engineer an optimal cosmeceutical product.

YAP Orchestrates Heterotypic Endothelial Cell Communication via HGF/c-MET Signaling in Liver Tumorigenesis

The oncogene yes-associated protein (YAP) controls liver tumor initiation and progression via cell extrinsic functions by creating a tumor-supporting environment in conjunction with cell autonomous mechanisms. However, how YAP controls organization of the microenvironment and in particular the vascular niche, which contributes to liver disease and hepatocarcinogenesis, is poorly understood. To investigate heterotypic cell communication, we dissected murine and human liver endothelial cell (EC) populations into liver sinusoidal endothelial cells (LSEC) and continuous endothelial cells (CEC) through histomorphological and molecular characterization. In YAP^S127A-induced tumorigenesis, a gradual replacement of LSECs by CECs was associated with dynamic changes in the expression of genes involved in paracrine communication. The formation of new communication hubs connecting CECs and LSECs included the hepatocyte growth factor (Hgf)/c-Met signaling pathway. In hepatocytes and tumor cells, YAP/TEA domain transcription factor 4 (TEAD4)-dependent transcriptional induction of osteopontin (Opn) stimulated c-Met expression in EC with CEC phenotype, which sensitized these cells to the promigratory effects of LSEC-derived Hgf. In human hepatocellular carcinoma, the presence of a migration-associated tip-cell signature correlated with poor clinical outcome and the loss of LSEC marker gene expression. The occurrence of c-MET-expressing CECs in human liver cancer samples was confirmed at the single-cell level. In summary, YAP-dependent changes of the liver vascular niche comprise the formation of heterologous communication hubs in which tumor cell-derived factors modify the cross-talk between LSECs and CECs via the HGF/c-MET axis. SIGNIFICANCE: YAP-dependent changes of the liver vascular niche comprise the formation of heterologous communication hubs in which tumor cell-derived factors modify the cross-talk between EC subpopulations. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/24/5502/F1.large.jpg.

Targeting Cancer Associated Fibroblasts in Liver Fibrosis and Liver Cancer Using Nanocarriers

Cancer associated fibroblasts (CAF) and the extracellular matrix (ECM) produced by them have been recognized as key players in cancer biology and emerged as important targets for cancer treatment and drug discovery. Apart from their presence in stroma rich tumors, such as biliary, pancreatic and subtypes of hepatocellular cancer (HCC), both CAF and certain ECM components are also present in cancers without an overt intra-tumoral desmoplastic reaction. They support cancer development, growth, metastasis and resistance to chemo- or checkpoint inhibitor therapy by a multitude of mechanisms, including angiogenesis, ECM remodeling and active immunosuppression by secretion of tumor promoting and immune suppressive cytokines, chemokines and growth factors. CAF resemble activated hepatic stellate cells (HSC)/myofibroblasts, expressing α-smooth muscle actin and especially fibroblast activation protein (FAP). Apart from FAP, CAF also upregulate other functional cell surface proteins like platelet-derived growth factor receptor β (PDGFRβ) or the insulin-like growth factor receptor II (IGFRII). Notably, if formulated with adequate size and zeta potential, injected nanoparticles home preferentially to the liver. Several nanoparticular formulations were tested successfully to deliver dugs to activated HSC/myofibroblasts. Thus, surface modified nanocarriers with a cyclic peptide binding to the PDGFRβ or with mannose-6-phosphate binding to the IGFRII, effectively directed drug delivery to activated HSC/CAF in vivo. Even unguided nanohydrogel particles and lipoplexes loaded with siRNA demonstrated a high in vivo uptake and functional siRNA delivery in activated HSC, indicating that liver CAF/HSC are also addressed specifically by well-devised nanocarriers with optimized physicochemical properties. Therefore, CAF have become an attractive target for the development of stroma-based cancer therapies, especially in the liver.

Decellularized extracellular matrix-rich hydrogel-silver nanoparticle mixture as a potential treatment for acute liver failure model

Acute liver failure (ALF) occurs due to severe liver damage that triggers rapid loss of normal liver function. Here, we investigate the usefulness of an injectable liver extracellular matrix (LECM)-rich hydrogel generated from an optimized decellularization protocol incorporated with silver nanoparticles (AgNPs) as a promising therapy for ALF. First, we optimized a non-destructive protocol for rat liver decellularization to obtain ECM-rich well-preserved scaffold. Then, LECM hydrogel generated from two commonly used decellularization protocols were compared by LECM hydrogel obtained from our optimized protocol. The ALF model was induced by an intraperitoneal (IP) thioacetamide (TAA) injection followed by the IP injection of LECM hydrogel, collagen-AgNP mixture, or LECM hydrogel-AgNP mixture. LECM-rich scaffold and hydrogel were successfully obtained using our optimized decellularization protocol. Use of the LECM hydrogel-AgNP mixture to treat TAA-induced ALF greatly improved liver injury and histological liver regeneration. Interleukin-6 and transforming growth factor-beta expressions were significantly reduced, while albumin, hepatocyte growth factor, and Ki67-positive cells were highly expressed. Moreover, aspartate transaminase and alanine transaminase plasma levels and liver homogenate nitric oxide level were significantly lowered. In conclusion, the LECM hydrogel-AgNP mixture has potential efficient therapeutic and regenerative effects on TAA-induced liver injury.

TLR3 promotes hepatocyte proliferation after partial hepatectomy by stimulating uPA expression and the release of tissue-bound HGF

TLR3 is implicated in anti-viral immune responses, but may also act as a sensor of tissue damage in the absence of infection. Here, we provide evidence for an essential role of TLR3 in liver regeneration after an acute loss of tissue due to partial hepatectomy. Mice lacking TLR3 had a severe and sustained defect in the restoration of liver tissue with reduced liver-to-body weight ratios even after an extended recovery period of 2 weeks. Hepatocyte cell cycle progression into S phase was impaired in TLR3-deficient mice. Mechanistic analyses revealed that TLR3-deficient mice had markedly reduced systemic levels of active HGF, but had increased amounts of inactive tissue-bound HGF. Importantly, expression of uPA, which orchestrates the processing and release of HGF from the hepatic extracellular matrix, was reduced in regenerating livers of TLR3-deficient mice. In addition, expression of the HGF maturation factor HGFAC was transiently diminished in TLR3-deficient mice. In vitro, engagement of TLR3 directly stimulated expression of uPA by hepatic stellate cells. Thus, TLR3 supports liver regeneration through upregulation of uPA, which promotes the release of preformed HGF from extracellular matrix stores.

Markers of liver regeneration-the role of growth factors and cytokines: a systematic review

BACKGROUND

Post-hepatectomy liver failure contributes significantly to postoperative mortality after liver resection. The prediction of the individual risk for liver failure is challenging. This review aimed to provide an overview of cytokine and growth factor triggered signaling pathways involved in liver regeneration after resection.

METHODS

MEDLINE and Cochrane databases were searched without language restrictions for articles from the time of inception of the databases till March 2019. All studies with comparative data on the effect of cytokines and growth factors on liver regeneration in animals and humans were included.

RESULTS

Overall 3.353 articles comprising 40 studies involving 1.498 patients and 101 animal studies were identified and met the inclusion criteria. All included trials on humans were retrospective cohort/observational studies. There was substantial heterogeneity across all included studies with respect to the analyzed cytokines and growth factors and the described endpoints.

CONCLUSION

High-level evidence on serial measurements of growth factors and cytokines in blood samples used to predict liver regeneration after resection is still lacking. To address the heterogeneity of patients and potential markers, high throughput serial analyses may offer a method to predict an individual's regenerative potential in the future.

Integrative Analysis of Proteomics and DNA Methylation in Orbital Fibroblasts From Graves' Ophthalmopathy

BACKGROUND

Graves' ophthalmopathy (GO) is a frequent extrathyroidal complication of Graves' hyperthyroidism. Orbital fibroblasts contribute to both orbital tissue inflammation and remodeling in GO, and as such are crucial cellular elements in active GO and inactive GO. However, so far it is largely unknown whether GO disease progression is associated with functional reprogramming of the orbital fibroblast effector function. Therefore, the aim of this study was to compare both the proteome and global DNA methylation patterns between orbital fibroblasts isolated from active GO, inactive GO and healthy controls.

METHODS

Orbital fibroblasts from inactive GO (n=5), active GO (n=4) and controls (n=5) were cultured and total protein and DNA was isolated. Labelled and fractionated proteins were analyzed with a liquid chromatography tandem-mass spectrometer (LC-MS/MS). Data are available via ProteomeXchange with identifier PXD022257. Furthermore, bisulphite-treated DNA was analyzed for methylation pattern with the Illumina Infinium Human Methylation 450K beadchip. In addition, RNA was isolated from the orbital fibroblasts for real-time quantitative (RQ)-PCR. Network and pathway analyses were performed.

RESULTS

Orbital fibroblasts from active GO displayed overexpression of proteins that are typically involved in inflammation, cellular proliferation, hyaluronan synthesis and adipogenesis, while various proteins associated with extracellular matrix (ECM) biology and fibrotic disease, were typically overexpressed in orbital fibroblasts from inactive GO. Moreover, orbital fibroblasts from active GO displayed hypermethylation of genes that linked to inflammation and hypomethylated genes that linked to adipogenesis and autoimmunity. Further analysis revealed networks that contained molecules to which both hypermethylated and hypomethylated genes were linked, including NF-κB, ERK1/2, Alp, RNA polymerase II, Akt and IFNα. In addition, NF-κB, Akt and IFNα were also identified in networks that were derived from the differentially expressed proteins. Generally, poor correlation between protein expression, DNA methylation and mRNA expression was observed.

CONCLUSIONS

Both the proteomics and DNA methylation data support that orbital fibroblasts from active GO are involved in inflammation, adipogenesis, and glycosaminoglycan production, while orbital fibroblasts from inactive disease are more skewed towards an active role in extracellular matrix remodeling. This switch in orbital fibroblast effector function may have therapeutic implications and further studies into the underlying mechanism are thus warranted.

Extracellular matrix-cell interactions: Focus on therapeutic applications

Extracellular matrix (ECM) macromolecules together with a multitude of different molecules residing in the extracellular space play a vital role in the regulation of cellular phenotype and behavior. This is achieved via constant reciprocal interactions between the molecules of the ECM and the cells. The ECM-cell interactions are mediated via cell surface receptors either directly or indirectly with co-operative molecules. The ECM is also under perpetual remodeling process influencing cell-signaling pathways on its part. The fragmentation of ECM macromolecules provides even further complexity for the intricate environment of the cells. However, as long as the interactions between the ECM and the cells are in balance, the health of the body is retained. Alternatively, any dysregulation in these interactions can lead to pathological processes and finally to various diseases. Thus, therapeutic applications that are based on retaining normal ECM-cell interactions are highly rationale. Moreover, in the light of the current knowledge, also concurrent multi-targeting of the complex ECM-cell interactions is required for potent pharmacotherapies to be developed in the future.

Distinct Localization of Mature HGF from its Precursor Form in Developing and Repairing the Stomach

Hepatocyte growth factor (HGF) is secreted as an inactive single-chain HGF (scHGF); however, only proteolytically processed two-chain HGF (tcHGF) can activate the MET receptor. We investigated the localization of tcHGF and activated/phosphorylated MET (pMET) using a tcHGF-specific antibody. In day 16.5 mouse embryos, total HGF (scHGF + tcHGF) was mainly localized in smooth muscle cells close to, but separate from, MET-positive epithelial cells in endodermal organs, including the stomach. In the adult stomach, total HGF was localized in smooth muscle cells, and tcHGF was mainly localized in the glandular base region. Immunostaining for pMET and Lgr5-driven green fluorescent protein (GFP) indicated that pMET localization overlapped with Lgr5⁺ gastric stem cells. HGF promoted organoid formation similar to EGF, indicating the potential for HGF to promote the survival and growth of gastric stem cells. pMET and tcHGF localizations changed during regeneration following gastric injury. These results indicate that MET is constantly activated in gastric stem cells and that the localization of pMET differs from the primary localization of precursor HGF but has a close relationship to tcHGF. Our results suggest the importance of the microenvironmental generation of tcHGF in the regulation of development, regeneration, and stem cell behavior.

The congenital clubfoot - immunohistological analysis of the extracellular matrix

Purpose

Congenital clubfoot is one of the most common limb disorders in humans and its etiology is still unclear. In order to better understand the pathogenesis of patients with primary clubfoot, we examined whether there are quantitative changes in the extracellular matrix (ECM; based on common interstitial collagens [C] like CI and CIII, microfilamentous collagens like CVI, noncollagenous proteins like undulin, and enzymes like matrixmetalloproteinase [MMP]-2 and tissue inhibitor of matrixmetalloproteinase [TIMP]-2 that are known to play a role in fibrogenesis and fibrolysis) of muscles involved in the foot deformity of patients with primary clubfoot corresponding to fibrosis.

Patients and methods

Thirty patients (age ranging from 4 months to 5 years and 7 months) with primary clubfoot were examined (23 male and 7 female patients), among whom 18 patients were affected on one side and 12 affected on both sides. Twenty-five biopsies were taken during the first operative foot correction (Crawford-McKay) and 5 in the context of relapses. Muscle biopsies were taken from the muscles involved in the defect (Musculus [M.] gastrocnemius and M. tibialis anterior) and from the M. vastus lateralis of the M. quadriceps femoris, which were treated as healthy comparison muscles. Quantitative analysis of the components of the ECM was performed using a computer-assisted fibrosis measurement of the immunohistochemically processed tissue samples.

Results

We found higher values for M. gastrocnemius for CI, CIII, CVI and undulin in comparison with M. vastus lateralis. However, values for TIMP-2 were reduced. We found no significant differences for the components of M. tibialis anterior and M. vastus lateralis. There were no quantitative differences between male and female or between patients affected on one side and both sides. In patients who underwent relapse surgery, CI, CIII, CVI, and undulin of the gastrocnemius were significantly higher, while TIMP-2 was significantly lower.

Conclusion

In the present study, we found manifest fibrosis in gastrocnemius due to quantitative changes in the ECM. In contrast to other studies, we found increasing fibrosis not just in contracted tissues but also in the muscle itself. Further studies are needed to clarify whether these changes are primarily responsible for the malfunction or whether they occur secondarily in the consequence of the dysfunction.

Keratin 19 Expression in Hepatocellular Carcinoma Is Regulated by Fibroblast-Derived HGF via a MET-ERK1/2-AP1 and SP1 Axis

Keratin (KRT) 19 is a poor prognostic marker for hepatocellular carcinoma (HCC); however, regulatory mechanisms underlying its expression remain unclear. We have previously reported the presence of fibrous tumor stroma in KRT19-positive HCC, suggesting that cross-talk between cancer-associated fibroblasts (CAF) and tumor epithelial cells could regulate KRT19 expression. This was investigated in this study using an in vitro model of paracrine interaction between HCC cell lines (HepG2, SNU423) and hepatic stellate cells (HSC), a major source of hepatic myofibroblasts. HSCs upregulated transcription and translation of KRT19 in HCC cells via paracrine interactions. Mechanistically, hepatocyte growth factor (HGF) from HSCs activated c-MET and the MEK-ERK1/2 pathway, which upregulated KRT19 expression in HCC cells. Furthermore, AP1 (JUN/FOSL1) and SP1, downstream transcriptional activators of ERK1/2, activated KRT19 expression in HCC cells. In clinical specimens of human HCC (n = 339), HGF and KRT19 protein expression correlated with CAF levels. In addition, HGF or MET protein expression was associated with FOSL1 and KRT19 expression and was found to be a poor prognostic factor. Analysis of data from The Cancer Genome Atlas also revealed KRT19 expression was closely associated with CAF and MET-mediated signaling activities. These results provide insights into the molecular background of KRT19-positive HCC that display an aggressive phenotype.Significance: These findings reveal KRT19 expression in hepatocellular carcinoma is regulated by cross-talk between cancer-associated fibroblasts and HCC cells, illuminating new therapeutic targets for this aggressive disease. Cancer Res; 78(7); 1619-31. ©2018 AACR.

Growth Factor Delivery Systems for Tissue Engineering and Regenerative Medicine

Growth factors (GFs) are often a key component in tissue engineering and regenerative medicine approaches. In order to fully exploit the therapeutic potential of GFs, GF delivery vehicles have to meet a number of key design criteria such as providing localized delivery and mimicking the dynamic native GF expression levels and patterns. The use of biomaterials as delivery systems is the most successful strategy for controlled delivery and has been translated into different commercially available systems. However, the risk of side effects remains an issue, which is mainly attributed to insufficient control over the release profile. This book chapter reviews the current strategies, chemistries, materials and delivery vehicles employed to overcome the current limitations associated with GF therapies.

Bioinspiring Chondrosia reniformis (Nardo, 1847) Collagen-Based Hydrogel: A New Extraction Method to Obtain a Sticky and Self-Healing Collagenous Material

Collagen is a natural and abundant polymer that serves multiple functions in both invertebrates and vertebrates. As collagen is the natural scaffolding for cells, collagen-based hydrogels are regarded as ideal materials for tissue engineering applications since they can mimic the natural cellular microenvironment. Chondrosia reniformis is a marine demosponge particularly rich in collagen, characterized by the presence of labile interfibrillar crosslinks similarly to those described in the mutable collagenous tissues (MCTs) of echinoderms. As a result single fibrils can be isolated using calcium-chelating and disulphide-reducing chemicals. In the present work we firstly describe a new extraction method that directly produces a highly hydrated hydrogel with interesting self-healing properties. The materials obtained were then biochemically and rheologically characterized. Our investigation has shown that the developed extraction procedure is able to extract collagen as well as other proteins and Glycosaminoglycans (GAG)-like molecules that give the collagenous hydrogel interesting and new rheological properties when compared to other described collagenous materials. The present work motivates further in-depth investigations towards the development of a new class of injectable collagenous hydrogels with tailored specifications.

Collagen XIV and a related recombinant fragment protect human vascular smooth muscle cells from calcium-/phosphate-induced osteochondrocytic transdifferentiation

Transdifferentiation of vascular smooth muscle cells (VSMC) promotes the development of vascular calcifications such as arteriosclerosis. The aim was to investigate effects of specific extracellular matrix (ECM) components on transdifferentiation of VSMC to identify novel ECM-based therapeutic tools. Human collagens I & IV (CI, CIV) along with collagen XIV (CXIV) and a CXIV-derived fragment (CXIV-F), both of which induce differentiation, were applied in an in-vitro model of calcium-/phosphate (Ca/P)-induced osteochondrocytic transdifferentiation of human and murine VSMC. Transdifferentiation was determined by RT-PCR and calcium contents of VSMC cultures. Signaling pathways involved were determined by western-blot and luciferase reporter plasmid assays. Under normal culture conditions, CI induced VSMC proliferation and a more epithelioid/synthetic phenotype while CIV and predominantly CXIV provoked opposite effects. CIV and CXIV further blocked Ca/P-induced osteochondrocytic transdifferentiation of VSMC displayed e.g. by reduced gene expressions of Runx2, Sox9, osterix and increased expressions of αSMA and SM22α. This involved impaired activation of ERK1/2, NF-ĸB and Wnt-signaling. Similar preventive effects were achieved by applying CXIV-F. Impaired preventive effects of CXIV by co-treatment with a cluster of differentiation (CD)44 agonist propose CD44 as a CXIV-target structure on VSMC. In conclusion, CXIV and CXIV-F interfere with osteochondrocytic transdifferentiation of VSMC and should be further explored as potential therapeutic tools in vascular calcification.

Mechanism of impairment on liver regeneration in elderly patients: Role of hepatic stellate cell function

Japan, along with most other countries in the world, is facing an increasingly aging population with a prolonged life expectancy. Concurrently, the need for medical intervention, including hepatectomy, has also increased for the elderly. Although surgical outcomes for older patients are reported to be comparable with those for younger patients, additional care in the selection of older patients for hepatectomy is considered necessary. Although the effect of aging on human liver regeneration is not fully understood, the regeneration of liver tissue after hepatectomy in elderly patients is shown to be generally worse than in younger patients and, to date, the mechanisms involved in the impairment of liver regeneration have not been fully clarified. Hepatic stellate cells (HSCs) are liver-specific mesenchymal cells that play critical roles in liver physiology and fibrogenesis. Recent studies in liver regeneration have increasingly focused on HSCs rather than on hepatocytes, Kupffer cells, endothelial cells, or infiltrating immune cells and suggest that HSCs might play a critical role in liver regeneration. In this review, we summarize the mechanisms involved in the impairment of liver regeneration in elderly patients, especially focusing on HSCs. We also discuss how HSCs contribute to the impairment of liver regeneration.

Collagen-based silver nanoparticles: Study on cell viability, skin permeation, and swelling inhibition

Collagen is considered the most abundant protein in the animal kingdom, comprising 30% of the total amount of proteins and 6% of the human body by weight. Studies that examine the interaction between silver nanoparticles and proteins have been highlighted in the literature in order to understand the stability of the nanoparticle system, the effects observed in biological systems, and the appearance of new chemical pharmaceutical products. The objective of this study was to analyze the behavior of silver nanoparticles stabilized with collagen (AgNPcol) and to check the skin permeation capacity and action in paw edema induced by carrageenan. AgNPcol synthesis was carried out using solutions of reducing agent sodium borohydride (NaBH₄), silver nitrate (AgNO₃) and collagen. Characterization was done by using dynamic light scattering (DLS) and X-ray diffraction (XRD) and AFM. Cellular viability testing was performed by using flow cytometry in human melanoma cancer (MV3) and murine fibroblast (L929) cells. The skin permeation study was conducted using a Franz diffusion cell, and the efficiency of AgNPcol against the formation of paw edema in mice was evaluated. The hydrodynamic diameter and zeta potential of AgNPcol were 140.7±7.8nm and 20.1±0.7mV, respectively. AgNPcol failed to induce early apoptosis, late apoptosis, and necrosis in L929 cells; however, it exhibited enhanced toxicity in cancer cells (MV3) compared to normal cells (L929). AgNPcol demonstrated increased toxicological effects in cancer MV3 cells, promoting skin permeation, and preventing paw edema.

New physiologically-relevant liver tissue model based on hierarchically cocultured primary rat hepatocytes with liver endothelial cells

To develop an in vitro liver tissue equivalent, hepatocytes should be cocultured with liver non-parenchymal cells to mimic the in vivo physiological microenvironments. In this work, we describe a physiologically-relevant liver tissue model by hierarchically organizing layers of primary rat hepatocytes and human liver sinusoidal endothelial cells (TMNK-1) on an oxygen-permeable polydimethylsiloxane (PDMS) membrane, which facilitates direct oxygenation by diffusion through the membrane. This in vivo-mimicking hierarchical coculture was obtained by simply proceeding the overlay of TMNK-1 cells on the hepatocyte layer re-formed on the collagen immobilized PDMS membranes. The comparison of hepatic functionalities was achieved between coculture and sandwich culture with Matrigel, in the presence and absence of direct oxygenation. A complete double-layered structure of functional liver cells with vertical contact between hepatocytes and TMNK-1 was successfully constructed in the coculture with direct oxygen supply and was well-maintained for 14 days. The hepatocytes in this hierarchical culture exhibited improved survival, functional bile canaliculi formation, cellular level polarization and maintenance of metabolic activities including Cyp1A1/2 activity and albumin production. By contrast, the two cell populations formed discontinuous monolayers on the same surfaces in the non-oxygen-permeable cultures. These results demonstrate that (i) the direct oxygenation through the PDMS membranes enables very simple formation of a hierarchical structure consisting of a hepatocyte layer and a layer of TMNK-1 and (ii) we may include other non-parenchymal cells in this format easily, which can be widely applicable to other epithelial organs.

Analysis of different components in the peritumoral tissue microenvironment of colorectal cancer: A potential prospect in tumorigenesis

The present study aimed to observe the varying expression of biomarkers in the microenvironment adjacent to colorectal cancer lesions to provide additional insight into the functions of microenvironment components in carcinogenesis and present a novel or improved indicator for early diagnosis of cancer. A total of 144 human samples from three different locations in 48 patients were collected, these locations were 10, 5 and 2 cm from the colorectal cancer lesion, respectively. The biomarkers analyzed included E‑cadherin, cytokeratin 18 (CK18), hyaluronidase‑1 (Hyal‑1), collagen type I (Col‑I), Crumbs3 (CRB3), vimentin, proteinase activated receptor 3 (PAR‑3), α‑smooth muscle actin (α‑SMA), cyclin D1 (CD1) and cluster of differentiation (CD)133. In addition, crypt architecture was observed. Related functional analysis of proteins was performed using hierarchical index cluster analysis. More severe destroyed crypt architecture closer to the cancer lesions was observed compared with the 10 cm sites, with certain crypts degraded entirely. Expression levels of E‑cadherin, CK18, CRB3 and PAR‑3 were lower in 2 cm sites compared with the 10 cm sites (all P<0.001), while the expression levels of the other biomarkers in the 2 cm sites were increased compared with 10 cm sites (all P<0.0001). Notably, the expression of CK18 in 2 cm sites was higher than in the 5 cm site (P<0.0001), which was different from the expression of E‑cadherin, CRB3 and PAR‑3. The expression levels of Hyal‑1 and Col‑I at the 2 cm sites were lower than that of the 5 cm sites (P>0.05 and P=0.0001, respectively), while the expression of vimentin, α‑SMA, CD1 and CD133 were not. Hyal‑1 and Col‑I may be independently important in cancer initiation in the tumor microenvironment. The results of the present study suggest that the biomarkers in the tissue microenvironment are associated with early tumorigenesis and may contribute to the development of carcinomas. These observations may be useful for early diagnosis of colorectal cancer.

Engineering growth factors for regenerative medicine applications

Growth factors are important morphogenetic proteins that instruct cell behavior and guide tissue repair and renewal. Although their therapeutic potential holds great promise in regenerative medicine applications, translation of growth factors into clinical treatments has been hindered by limitations including poor protein stability, low recombinant expression yield, and suboptimal efficacy. This review highlights current tools, technologies, and approaches to design integrated and effective growth factor-based therapies for regenerative medicine applications. The first section describes rational and combinatorial protein engineering approaches that have been utilized to improve growth factor stability, expression yield, biodistribution, and serum half-life, or alter their cell trafficking behavior or receptor binding affinity. The second section highlights elegant biomaterial-based systems, inspired by the natural extracellular matrix milieu, that have been developed for effective spatial and temporal delivery of growth factors to cell surface receptors. Although appearing distinct, these two approaches are highly complementary and involve principles of molecular design and engineering to be considered in parallel when developing optimal materials for clinical applications.

STATEMENT OF SIGNIFICANCE

Growth factors are promising therapeutic proteins that have the ability to modulate morphogenetic behaviors, including cell survival, proliferation, migration and differentiation. However, the translation of growth factors into clinical therapies has been hindered by properties such as poor protein stability, low recombinant expression yield, and non-physiological delivery, which lead to suboptimal efficacy and adverse side effects. To address these needs, researchers are employing clever molecular and material engineering and design strategies to both improve the intrinsic properties of growth factors and effectively control their delivery into tissue. This review highlights examples of interdisciplinary tools and technologies used to augment the therapeutic potential of growth factors for clinical applications in regenerative medicine.

A perspective on structural and computational work on collagen

Collagen is the single most abundant protein in the extracellular matrix in the animal kingdom, with remarkable structural and functional diversity and regarded one of the most useful biomaterials.

Role of tyrosine-sulfated proteins in retinal structure and function

The extracellular matrix (ECM) plays a significant role in cellular and retinal health. The study of retinal tyrosine-sulfated proteins is an important first step toward understanding the role of ECM in retinal health and diseases. These secreted proteins are members of the retinal ECM. Tyrosine sulfation was shown to be necessary for the development of proper retinal structure and function. The importance of tyrosine sulfation is further demonstrated by the evolutionary presence of tyrosylprotein sulfotransferases, enzymes that catalyze proteins' tyrosine sulfation, and the compensatory abilities of these enzymes. Research has identified four tyrosine-sulfated retinal proteins: fibulin 2, vitronectin, complement factor H (CFH), and opticin. Vitronectin and CFH regulate the activation of the complement system and are involved in the etiology of some cases of age-related macular degeneration. Analysis of the role of tyrosine sulfation in fibulin function showed that sulfation influences the protein's ability to regulate growth and migration. Although opticin was recently shown to exhibit anti-angiogenic properties, it is not yet determined what role sulfation plays in that function. Future studies focusing on identifying all of the tyrosine-sulfated retinal proteins would be instrumental in determining the impact of sulfation on retinal protein function in retinal homeostasis and diseases.

Novel insights into the function and dynamics of extracellular matrix in liver fibrosis

Emerging evidence suggests that altered components and posttranslational modifications of proteins in the extracellular matrix (ECM) may both initiate and drive disease progression. The ECM is a complex grid consisting of multiple proteins, most of which play a vital role in containing the essential information needed for maintenance of a sophisticated structure anchoring the cells and sustaining normal function of tissues. Therefore, the matrix itself may be considered as a paracrine/endocrine entity, with more complex functions than previously appreciated. The aims of this review are to 1) explore key structural and functional components of the ECM as exemplified by monogenetic disorders leading to severe pathologies, 2) discuss selected pathological posttranslational modifications of ECM proteins resulting in altered functional (signaling) properties from the original structural proteins, and 3) discuss how these findings support the novel concept that an increasing number of components of the ECM harbor signaling functions that can modulate fibrotic liver disease. The ECM entails functions in addition to anchoring cells and modulating their migratory behavior. Key ECM components and their posttranslational modifications often harbor multiple domains with different signaling potential, in particular when modified during inflammation or wound healing. This signaling by the ECM should be considered a paracrine/endocrine function, as it affects cell phenotype, function, fate, and finally tissue homeostasis. These properties should be exploited to establish novel biochemical markers and antifibrotic treatment strategies for liver fibrosis as well as other fibrotic diseases.

Cooperativity to increase Turing pattern space for synthetic biology

It is hard to bridge the gap between mathematical formulations and biological implementations of Turing patterns, yet this is necessary for both understanding and engineering these networks with synthetic biology approaches. Here, we model a reaction-diffusion system with two morphogens in a monostable regime, inspired by components that we recently described in a synthetic biology study in mammalian cells.1 The model employs a single promoter to express both the activator and inhibitor genes and produces Turing patterns over large regions of parameter space, using biologically interpretable Hill function reactions. We applied a stability analysis and identified rules for choosing biologically tunable parameter relationships to increase the likelihood of successful patterning. We show how to control Turing pattern sizes and time evolution by manipulating the values for production and degradation relationships. More importantly, our analysis predicts that steep dose-response functions arising from cooperativity are mandatory for Turing patterns. Greater steepness increases parameter space and even reduces the requirement for differential diffusion between activator and inhibitor. These results demonstrate some of the limitations of linear scenarios for reaction-diffusion systems and will help to guide projects to engineer synthetic Turing patterns.

Morphogen and proinflammatory cytokine release kinetics from PRGF-Endoret fibrin scaffolds: evaluation of the effect of leukocyte inclusion

The potential influence of leukocyte incorporation in the kinetic release of growth factors from platelet-rich plasma (PRP) may explain the conflicting efficiency of leukocyte platelet-rich plasma (L-PRP) scaffolds in tissue regeneration. To assess this hypothesis, leukocyte-free (PRGF-Endoret) and L-PRP fibrin scaffolds were prepared, and both morphogen and proinflammatory cytokine release kinetics were analyzed. Clots were incubated with culture medium to monitor protein release over 8 days. Furthermore, the different fibrin scaffolds were morphologically characterized. Results show that leukocyte-free fibrin matrices were homogenous while leukocyte-containing ones were heterogeneous, loose and cellular. Leukocyte incorporation produced a significant increase in the contents of proinflammatory cytokines interleukin (IL)-1β and IL-16 but not in the platelet-derived growth factors release (<1.5-fold). Surprisingly, the availability of vascular endothelial growth factor suffered an important decrease after 3 days of incubation in the case of L-PRP matrices. While the release of proinflammatory cytokines was almost absent or very low from PRGF-Endoret, the inclusion of leukocytes induced a major increase in these cytokines, which was characterized by the presence of a latent period. The PRGF-Endoret matrices were stable during the 8 days of incubation. The inclusion of leukocytes alters the growth factors release profile and also increased the dose of proinflammatory cytokines.

Imbalanced matriptase pericellular proteolysis contributes to the pathogenesis of malignant B-cell lymphomas

Membrane-associated serine protease matriptase is widely expressed by epithelial/carcinoma cells in which its proteolytic activity is tightly controlled by the Kunitz-type protease inhibitor, hepatocyte growth factor activator inhibitor (HAI-1). We demonstrate that, although matriptase is not expressed in lymphoid hyperplasia, roughly half of the non-Hodgkin B-cell lymphomas analyzed express significant amounts of matriptase. Furthermore, a significant proportion of these tumors express matriptase in the absence of HAI-1. Aggressive Burkitt lymphoma was more likely than indolent follicular lymphoma to express matriptase alone (86% versus 36%). In the absence of significant HAI-1 expression, the lymphoma cells activate and shed active matriptase when the cells are stimulated with mildly acidic buffer or the hypoxia-mimicking agent, CoCl2. The shed active matriptase can initiate pericellular proteolytic cascades by activating urokinase-type plasminogen activator on the cell surface of monocytes, and it can activate prohepatocyte growth factor. In addition, matriptase knockdown suppressed proliferation and colony-forming ability of neoplastic B cells in culture and growth as tumor xenografts in mice. Furthermore, exogenous expression of HAI-1 significantly suppressed proliferation of neoplastic B cells. These studies suggest that dysregulated pericellular proteolysis as a result of unregulated matriptase expression with limited HAI-1 may contribute to the pathological characteristics of several human B-cell lymphomas through modulation of the tumor microenvironment and enhanced tumor growth.

Stress-induced ECM alteration modulates cellular microRNAs that feedback to readjust the extracellular environment and cell behavior

The extracellular environment is a complex entity comprising of the extracellular matrix (ECM) and regulatory molecules. It is highly dynamic and under cell-extrinsic stress, transmits the stressed organism’s state to each individual ECM-connected cell. microRNAs (miRNAs) are regulatory molecules involved in virtually all the processes in the cell, especially under stress. In this review, we analyse how miRNA expression is regulated downstream of various signal transduction pathways induced by changes in the extracellular environment. In particular, we focus on the muscular dystrophy-associated cell adhesion molecule dystroglycan capable of signal transduction. Then we show how exactly the same miRNAs feedback to regulate the extracellular environment. The ultimate goal of this bi-directional signal transduction process is to change cell behavior under cell-extrinsic stress in order to respond to it accordingly.

Principles of liver regeneration and growth homeostasis

Liver regeneration is perhaps the most studied example of compensatory growth aimed to replace loss of tissue in an organ. Hepatocytes, the main functional cells of the liver, manage to proliferate to restore mass and to simultaneously deliver all functions hepatic functions necessary to maintain body homeostasis. They are the first cells to respond to regenerative stimuli triggered by mitogenic growth factor receptors MET (the hepatocyte growth factor receptor] and epidermal growth factor receptor and complemented by auxiliary mitogenic signals induced by other cytokines. Termination of liver regeneration is a complex process affected by integrin mediated signaling and it restores the organ to its original mass as determined by the needs of the body (hepatostat function). When hepatocytes cannot proliferate, progenitor cells derived from the biliary epithelium transdifferentiate to restore the hepatocyte compartment. In a reverse situation, hepatocytes can also transdifferentiate to restore the biliary compartment. Several hormones and xenobiotics alter the hepatostat directly and induce an increase in liver to body weight ratio (augmentative hepatomegaly). The complex challenges of the liver toward body homeostasis are thus always preserved by complex but unfailing responses involving orchestrated signaling and affecting growth and differentiation of all hepatic cell types.

Matriptase expression and zymogen activation in human pilosebaceous unit

Studies of human genetic disorders and mouse models reveal the important roles of matriptase in hair growth. Here, we investigate matriptase expression and zymogen activation in hair follicles. We show: 1) layer-dependent distribution patterns, with much higher matriptase expression in cells of the outer root sheath and matrix cells of the hair bulb than in cells of the inner root sheath; 2) cycle-dependent expression patterns, with matriptase expressed in the anagen and catagen phases of the hair lifecycle, but not in the telogen phase; 3) reduced expression of the matriptase inhibitor, HAI-1, in the catagen phase, suggesting increased proteolytic activity in this phase; and 4) definitive matriptase zymogen activation patterns, with the highest matriptase activation observed in matrix cells and outer root sheath cells in the isthmus/bulge region. In sebaceous glands, matriptase is highly expressed in basal and ductal cells, with much lower expression in the differentiated, lipid-filled cells of the interior. We also show that matriptase potently activates hepatocyte growth factor (HGF) in vitro, and that the HGF receptor, c-Met, is co-expressed in those cells that express activated matriptase. Our observations suggest that the matriptase-HGF-c-MET pathway has the potential to be engaged, primarily in proliferative cells rather than terminally differentiated epithelial cells of the human pilosebaceous unit.

Hepatic stellate cells in liver development, regeneration, and cancer

Hepatic stellate cells are liver-specific mesenchymal cells that play vital roles in liver physiology and fibrogenesis. They are located in the space of Disse and maintain close interactions with sinusoidal endothelial cells and hepatic epithelial cells. It is becoming increasingly clear that hepatic stellate cells have a profound impact on the differentiation, proliferation, and morphogenesis of other hepatic cell types during liver development and regeneration. In this Review, we summarize and evaluate the recent advances in our understanding of the formation and characteristics of hepatic stellate cells, as well as their function in liver development, regeneration, and cancer. We also discuss how improved knowledge of these processes offers new perspectives for the treatment of patients with liver diseases.

Hepatocyte growth factor and lung fibrosis

Idiopathic pulmonary fibrosis is currently believed to be driven by alveolar epithelial cells, with abnormally activated alveolar epithelial cells accumulating in an attempt to repair injured alveolar epithelium (1). Thus, targeting the alveolar epithelium to prevent or inhibit the development of pulmonary fibrosis might be an interesting therapeutic option in this disease. Hepatocyte growth factor (HGF) is a growth factor for epithelial and endothelial cells, which is secreted by different cell types, especially fibroblasts and neutrophils. HGF has mitogenic, motogenic, and morphogenic properties and exerts an antiapoptotic action on epithelial and endothelial cells. HGF has also proangiogenic effect. In vitro, HGF inhibits epithelial-to-mesenchymal cell transition and promotes myofibroblast apoptosis. In vivo, HGF has antifibrotic properties demonstrated in experimental models of lung, kidney, heart, skin, and liver fibrosis. Hence, the modulation of HGF may be an attractive target for the treatment of lung fibrosis.

Signals and cells involved in regulating liver regeneration

Liver regeneration is a complex phenomenon aimed at maintaining a constant liver mass in the event of injury resulting in loss of hepatic parenchyma. Partial hepatectomy is followed by a series of events involving multiple signaling pathways controlled by mitogenic growth factors (HGF, EGF) and their receptors (MET and EGFR). In addition multiple cytokines and other signaling molecules contribute to the orchestration of a signal which drives hepatocytes into DNA synthesis. The other cell types of the liver receive and transmit to hepatocytes complex signals so that, in the end of the regenerative process, complete hepatic tissue is assembled and regeneration is terminated at the proper time and at the right liver size. If hepatocytes fail to participate in this process, the biliary compartment is mobilized to generate populations of progenitor cells which transdifferentiate into hepatocytes and restore liver size.

Protein-hydrogel interactions in tissue engineering: mechanisms and applications

Recent advances in our understanding of the sophistication of the cellular microenvironment and the dynamics of tissue remodeling during development, disease, and regeneration have increased our appreciation of the current challenges facing tissue engineering. As this appreciation advances, we are better equipped to approach problems in the biology and therapeutics of even more complex fields, such as stem cells and cancer. To aid in these studies, as well as the established areas of tissue engineering, including cardiovascular, musculoskeletal, and neural applications, biomaterials scientists have developed an extensive array of materials with specifically designed chemical, mechanical, and biological properties. Herein, we highlight an important topic within this area of biomaterials research, protein-hydrogel interactions. Due to inherent advantages of hydrated scaffolds for soft tissue engineering as well as specialized bioactivity of proteins and peptides, this field is well-posed to tackle major needs within emerging areas of tissue engineering. We provide an overview of the major modes of interactions between hydrogels and proteins (e.g., weak forces, covalent binding, affinity binding), examples of applications within growth factor delivery and three-dimensional scaffolds, and finally future directions within the area of hydrogel-protein interactions that will advance our ability to control the cell-biomaterial interface.

Regulation of the g1/s transition in hepatocytes: involvement of the cyclin-dependent kinase cdk1 in the DNA replication

A singular feature of adult differentiated hepatocytes is their capacity to proliferate allowing liver regeneration. This review emphasizes the literature published over the last 20 years that established the most important pathways regulating the hepatocyte cell cycle. Our article also aimed at illustrating that many discoveries in this field benefited from the combined use of in vivo models of liver regeneration and in vitro models of primary cultures of human and rodent hepatocytes. Using these models, our laboratory has contributed to decipher the different steps of the progression into the G1 phase and the commitment to S phase of proliferating hepatocytes. We identified the mitogen dependent restriction point located at the two-thirds of the G1 phase and the concomitant expression and activation of both Cdk1 and Cdk2 at the G1/S transition. Furthermore, we demonstrated that these two Cdks contribute to the DNA replication. Finally, we provided strong evidences that Cdk1 expression and activation is correlated to extracellular matrix degradation upon stimulation by the pro-inflammatory cytokine TNFα leading to the identification of a new signaling pathway regulating Cdk1 expression at the G1/S transition. It also further confirms the well-orchestrated regulation of liver regeneration via multiple extracellular signals and pathways.

Repair of segmental bone defects in rabbit tibia promoted by a complex of β-tricalcium phosphate and hepatocyte growth factor

BACKGROUND

Segmental bone defect repair remains a clinical and scientific challenge with increasing interest focused on bone tissue engineering. Clinical studies are ongoing to address application of hepatocyte growth factor (HGF) for treatment of some diseases; however, the use of HGF in bone tissue engineering has not been addressed. This study was performed to evaluate the effect of HGF in a complex of β-tricalcium phosphate (β-TCP) and collagen in repairing segmental bone defects.

METHODS

Segmental bone defects 5 mm long were created in the middle of the tibial shafts of rabbits. The defect was stabilized with external fixators and implanted with a complex of β-TCP granules and collagen, with or without 100 μg recombinant human HGF. Biweekly, bone regeneration and β-TCP resorption were assessed radiographically and histologically. At 4 and 8 weeks, bone regeneration was evaluated by use of micro-computed tomography and mechanical tests.

RESULTS

Compared with the bone tissue treated with β-TCP and collagen, mineralization, angiogenesis, new bone formation, and absorption of β-TCP were promoted 4 weeks postoperatively by treatment with HGF in the β-TCP and collagen group. These changes were associated with promoting biomechanical regeneration. By 8 weeks, the formation of bone marrow in newly generated bone and absorption of the β-TCP granules were completed in a shorter period by combining HGF with β-TCP and collagen, compared with tissues without HGF.

CONCLUSIONS

The combined application of HGF in a β-TCP and collagen matrix promoted histological bone healing and augmented mechanical strength of the healing bone, particularly in the early stages. The combined use of HGF and β-TCP for treatment of bone defects made a substantial difference.

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Bottom-up signaling from HGF-containing surfaces promotes hepatic differentiation of mesenchymal stem cells

The capacity of stem cells to differentiate into specific cell types makes them very promising in tissue regeneration and repair. However, realizing this promise requires novel methods for guiding lineage-specific differentiation of stem cells. In this study, hepatocyte growth factor (HGF), an important morphogen in liver development, was co-printed with collagen I (Col) to create arrays of protein spots on glass. Human adipose stem cells (ASCs) were cultured on top of the HGF/Col spots for 2weeks. The effects of surface-immobilized HGF on hepatic differentiation of ASCs were analyzed using RT-PCR, ELISA and immunocytochemistry. Stimulation of stem cells with HGF from the bottom-up caused an upregulation in synthesis of α-fetoprotein and albumin, as determined by immunocytochemistry and ELISA. RT-PCR results showed that the mRNA levels for albumin, α-fetoprotein and α1-antitrypsin were 10- to 20-fold higher in stem cells cultured on the HGF/Col arrays compared to stem cells on Col only spots. Our results show that surfaces containing HGF co-printed with ECM proteins may be used to differentiate mesenchymal stem cells such as ASCs into hepatocyte-like cells. These results underscore the utility of growth factor-containing culture surfaces for stem cell differentiation.