A composite Gelatin/hyaluronic acid hydrogel as an ECM mimic for developing mesenchymal stem cell‐derived epithelial tissue patches

Here we report fabrication of Gelatin‐based biocomposite films and their application in developing epithelial patches. The films were loaded with an epithelial cell growth factor cocktail and used as an extracellular matrix mimic for in vitro regeneration of organized respiratory epithelium using Calu‐3 cell line and mesenchymal stem cells (MSCs). Our data show differentiation of Calu‐3 cells on composite films as evidenced by tight junction protein expression and barrier formation. The films also supported attachment, migration, and proliferation of alveolar basal epithelial cell line A549. We also show the suitability of the composite films as a biomimetic scaffold and growth factor delivery platform for differentiation of human MSCs to epithelial cells. MSCs differentiation to the epithelial lineage was confirmed by staining for epithelial and stem cell specific markers. Our data show that the MSCs acquire the epithelial characteristics after 2 weeks with significant reduction in vimentin, increase in pan cytokeratin expression, and morphological changes. However, despite the expression of epithelial lineage markers, these cells did not form fully functional tight junctions as evidenced by low expression of junctional protein ZO1. Further optimisation of culture conditions and growth factor cocktail is required to enhance tight junction formation in MSCs‐derived epithelial cells on the composite hydrogels. Nevertheless, our data clearly highlight the possibility of using MSCs in epithelial tissue engineering and the applicability of the composite hydrogels as transferrable extracellular matrix mimics and delivery platforms with potential applications in regenerative medicine and in vitro modelling of barrier tissues.     

Developing a tissue‐engineered model of the human bronchiole

Scientists are always looking for new tools to better mimic human anatomy and physiology, especially to study chronic respiratory disease. Airway remodelling is a predominant feature in asthma and occurs in conjunction with chronic airway inflammation. Both the inflammatory and repair processes alter the airway wall which is marked by anatomical, physiological and functional changes. A tissue‐engineered model of bronchiole remodelling presents a novel approach to investigating the initiation and progression of airway remodelling. By developing a unique bioreactor system, cylindrical‐shaped bronchioles constructed from well‐characterized human lung primary cells have been engineered and examined with a much greater control over experimental variables. We have grown human bronchioles composed of fibroblasts, airway smooth muscle cells, small airway epithelial cells and extracellular matrices. The various cell types are in close proximity to one another for cell–cell signalling and matrix interactions. The cylindrical geometry of the tissue applies radial distension for mechanotransduction and the air interface provides a natural environment for the epithelial cells. Optimal cell density, extracellular matrix concentration and media composition were determined. Immunohistochemistry verified bronchiole phenotypic stability. Quiescence was gauged by protein expression which verified a change in phenotype after the initial fabrication stage and implementation of the air interface. A fabrication timeline was devised for repeatable bronchiole fabrication and to understand tissue contraction and cell‐seeding duration. The stability of the bronchiole structures and their cellular composition lends these bronchioles to study cell–cell interactions and remodelling events while maintaining in vivo geometrical dimensions and relationships. Copyright © 2010 John Wiley & Sons, Ltd.     

曲伏前列腺素对体外培养人眼睫状肌细胞基质金属蛋白酶2的作用

背景:曲伏前列腺素可通过增加眼睫状肌细胞间间隙,使葡萄膜巩膜房水流出通道流出阻力下降,进而降低眼压,这一作用途径是否通过增强睫状肌基质金属蛋白酶的表达而完成?目的:观察曲伏前列腺素干预人眼睫状肌细胞基质金属蛋白酶2表达活性的作用。设计:观察对比分析。单位:中山大学附属第二医院眼科。材料:实验于2005-08/2006-04在中山大学附属眼科中心完成。供体摘自1例死亡1h内无眼疾青年尸体单侧眼球(均经其家属同意),取自中山眼科医院,供体排除眼部疾患。兔抗人基质金属蛋白酶2多克隆抗体(武汉博士德生物工程有限公司),曲伏前列腺素(美国ALCON公司,批号:86610F,0.004%溶液)。方法:实验干预:在人睫状肌细胞无牛血清培养基中加入1μmol/L曲伏前列腺素为实验组,同时以无药物干预的细胞为对照组,实验组于加药后6,12,24h收集细胞进行观察。实验评估:采用RT-PCR和ELISA法分别检测各组人睫状肌细胞基质金属蛋白酶2在基因和蛋白水平的表达;采用Zymography技术分别检测各组细胞基质金属蛋白酶2的活性。主要观察指标:人眼睫状体细胞内基质金属蛋白酶2 mRNA的表达,细胞外液基质金属蛋白酶2蛋白表达以及基质金属蛋白酶2活性。结果:①基质金属蛋白酶2 mRNA的表达:实验组加药后6,12,24h基质金属蛋白酶2 mRNA相对表达量呈逐渐升高趋势(F=236.959,P<0.01)。②基质金属蛋白酶2蛋白表达:实验组加药后6,12,24h基质金属蛋白酶2表达随曲伏前列腺素作用时间延长逐渐升高(F=38.110,P<0.01)。③基质金属蛋白酶2活性:Zymography技术检测实验组加药后6,12,24h基质金属蛋白酶2活性随曲伏前列腺素作用时间延长而逐渐增强(F=74.348,P<0.01)。结论:体外培养的人睫状肌细胞接受曲伏前列腺素作用后,基质金属蛋白酶2表达随药物作用时间延长逐渐增加,活性逐渐增强。     

Respiratory epithelial cell expression of human transforming growth factor-alpha induces lung fibrosis in transgenic mice.

Increased production of EGF or TGF-alpha by the respiratory epithelial cells has been associated with the pathogenesis of various forms of lung injury. Growth factors and cytokines are thought to act locally, via paracrine and autocrine mechanisms, to stimulate cell proliferation and matrix deposition by interstitial lung cells resulting in pulmonary fibrosis. To test whether TGF-alpha mediates pulmonary fibrotic responses, we have generated transgenic mice expressing human TGF-alpha under control of regulatory regions of the human surfactant protein C (SP-C) gene. Human TGF-alpha mRNA was expressed in pulmonary epithelial cells in the lungs of the transgenic mice. Adult mice bearing the SP-C-TGF-alpha transgene developed severe pulmonary fibrosis. Fibrotic lesions were observed in peribronchial, peribronchiolar, and perivascular regions, as well as subjacent to pleural surfaces. Lesions consisted of fibrous tissue that included groups of epithelial cells expressing endogenous SP-C mRNA, consistent with their identification as distal respiratory epithelial cells. Peripheral fibrotic regions consisted of thickened pleura associated with extensive collagen deposition. Alveolar architecture was disrupted in the transgenic mice with loss of alveoli in the lung parenchyma. Pulmonary epithelial cell expression of TGF-alpha in transgenic mice disrupts alveolar morphogenesis and produces fibrotic lesions mediated by paracrine signaling between respiratory epithelial and interstitial cells of the lung.     

IL-13 alters mucociliary differentiation and ciliary beating of human respiratory epithelial cells

In animal models of asthma, interleukin-13 (IL-13) induces goblet cell metaplasia, eosinophil infiltration of the bronchial mucosa, and bronchial hyperreactivity, but the basis of its effects on airway epithelia remain unknown. Lesions of the epithelial barrier, frequently observed in asthma and other chronic lung inflammatory diseases, are repaired through proliferation, migration, and differentiation of epithelial cells. An inflammatory process may then, therefore, influence epithelial regeneration. We have thus investigated the effect of IL-13 on mucociliary differentiation of human nasal epithelial cells in primary culture. We show that IL-13 alters ciliated cell differentiation and increases the proportion of secretory cells. IL-13 downregulates the actin-binding protein ezrin and other cytoskeletal components. IL-13 also impairs lateral cell contacts and interferes with the apical localization of ezrin seen in differentiated ciliated cells. In addition, an IL-4 antagonistic mutant protein (Y124D), which binds to the IL-4 receptor alpha subunit, a common chain of IL-4 and IL-13 receptors, inhibits IL-13's effects. IL-13 also decreases ciliary beat frequency in a time- and dose-dependent manner. These results suggest that, in human allergic asthmatic responses, IL-13 affects both ciliated and secretory cell differentiation, leading to airway damage and obstruction.     

Nanoparticulate mineralized collagen glycosaminoglycan materials directly and indirectly inhibit osteoclastogenesis and osteoclast activation

The ability of the extracellular matrix (ECM) to direct cell fate has generated the potential for developing a materials‐only strategy for tissue regeneration. Previously, we described a nanoparticulate mineralized collagen glycosaminoglycan (MC‐GAG) material that efficiently induced osteogenic differentiation of human mesenchymal stem cells (hMSCs) and calvarial bone healing without exogenous growth factors or progenitor cell expansion. In this work, we evaluated the interactions between MC‐GAG and primary human osteoclasts (hOCs). In the absence of hMSCs, mineralized Col‐GAG materials directly inhibited hOC viability, proliferation, and resorption in contrast to nonmineralized Col‐GAG, which demonstrated a modest inhibition of resorptive activity only. Cocultures containing differentiating hMSCs with hOCs demonstrated increased hOC‐mediated resorption only on Col‐GAG while MC‐GAG cocultures continued to inhibit resorption. Unlike Col‐GAG, hMSCs on MC‐GAG expressed increased amounts of osteoprotegerin (OPG) protein, the major endogenous osteoclast inhibitor. Interestingly, OPG expression was found to be antagonized by small mothers against decapentaplegic1/5 (Smad1/5) phosphorylation, an obligate pathway for osteogenic differentiation of hMSCs on MC‐GAG, and potentiated by extracellular signal‐regulated kinase (ERK1/2) phosphorylation. Collectively, these results suggested that the MC‐GAG material both directly inhibited the osteoclast viability, proliferation, and resorptive activity as well as induced hMSCs to secrete osteoprotegerin, an antiosteoclastogenic factor, via a signalling pathway distinct from osteogenic differentiation.     

Gene transfer into respiratory epithelial cells by targeting the polymeric immunoglobulin receptor.

A system for targeting foreign DNA to epithelial cells in vitro has been developed by exploiting receptor-mediated endocytosis. The polymeric immunoglobulin receptor transports dimeric immunoglobulin A and immunoglobulin M through epithelial cells, including those of the respiratory tract, by binding the immunoglobulins at the basolateral surface and transporting them across the cell. Fab fragments of antibodies directed against the extracellular portion of the receptor, secretory component, are similarly transported. Anti-human secretory component Fab fragments were covalently linked to a polycation, and complexed to various expression plasmids. When bound to an expression plasmid containing the Escherichia coli lacZ gene ligated to the Rous sarcoma virus promoter, the complexes transfected HT29.74 human colon carcinoma cells induced to express polymeric immunoglobulin receptor, but not those lacking the receptor. Primary cultures of human tracheal epithelial cells grown on collagen gels, which induce the expression of polymeric immunoglobulin receptor, were also transfected with the complexes. From 5 to 66% of the respiratory epithelial cells had beta-galactosidase activity after treatment, comparable to the percentage of cultured human tracheal epithelial cells that express polymeric immunoglobulin receptor (8-35%). The addition of excess human secretory component (Fab ligand) to the culture medium at the time of transfection blocked the delivery of DNA. The expression plasmid, either alone, complexed to the polycation, or complexed to a carrier based on an irrelevant Fab fragment, was not effective in transfecting either cell type. This DNA carrier system introduces DNA specifically into epithelial cells that contain pIgR in vitro.     

Collagen vitrigels with low‐fibril density enhance human embryonic stem cell‐derived retinal pigment epithelial cell maturation

Structural and biochemical cues of extracellular matrix can substantially influence the differentiation and maturation of cultured retinal pigment epithelial (RPE) cells. In this study, thin collagen vitrigels were engineered to create collagen nanofibrillar structures of different fibril densities in an effort to evaluate the maturation of human embryonic stem cell–derived retinal pigment epithelial (hESC‐RPE) cells. The ultrastructure of the different collagen vitrigels was characterized by transmission electron microscopy, and the mechanical properties were evaluated by tensile testing. The pigmentation and polarization of cells, in addition to key RPE marker gene and protein expression levels, were analyzed to determine the differentiation of hESCs on the gels. The hESC‐RPE differentiation was most significant in collagen vitrigels with low fibril density with mature collagen fibrils with diameter of around 60 nm and Young's modulus of 2.41 ± 0.13 MPa. This study provides insight into the influence of collagen nanofibrillar structures on hESC‐RPE maturation and presents a potential bioengineered substratum for hESC‐RPE for future preclinical and clinical applications.     

Matrix in cartilage and bone development: current views on the function and regulation of major organic components

Study of the growth and development of cartilage and bone has been difficult because the structure of the tissues makes biological experiments hard to conduct. Recent advances in molecular biology have offered new possibilities for studying these processes. Many cartilage and bone specific cDNAs have been cloned and characterized and consequently used to localize the corresponding mRNAs in tissue sections. Developing cartilage and bone serve as a model for the study of extracellular matrix gene regulation during the proliferation, growth and differentiation of connective tissue cells. Normal skeletal growth and development are regulated by both systemic and local factors. The effects of many systemic hormones on bone metabolism have been studied extensively, but the pathways triggered by these hormones in the target cells are less well known. Recent evidence suggests that some growth factors, such as TGF-beta, IGFs and PDGF, act as local regulators of cartilage and bone metabolism. The different extracellular matrix components, e.g. collagens, are expressed differently in distinct cell types and developmental stages during cartilage and bone development. This model, therefore, facilitates the study of relations between the production of the various extracellular matrix components and the growth factors and the proto-oncogenes which may regulate them. Existing knowledge of the expression of major cartilage and bone components and their regulation during growth, differentiation and development is reviewed. An understanding of the normal growth and development of cartilage and bone is fundamental for elucidating the mechanisms underlying the various diseases -- both hereditary and acquired -- affecting the human skeleton.     

Matrix metalloproteinases: potential therapeutic target in spinal cord injury.

Mediators of extracellular matrix proteins degradation, the matrix metalloproteinases (MMPs), involved in inflammation as well as facilitation of process outgrowth of oligodendrocytes are interesting targets for neural repair. Recent data reported their activation after seizures, cerebral ischemia and spinal cord injury. The present study was designed to localize at cellular level the gelatinase activity by in situ zymography in a rat spinal cord contusion model. The kinetic of gelatinase activation was monitored by in situ zymography on 20 microm cryostat sections. The fluorescein-quenched DQ gelatin digestion yielded cleaved fluorescent peptides enabling the detection of gelatinase activity at cellular level. Twenty four hours and 48 h after injury, a strong gelatinase activity was detected at the lesion site in and around vascular structures and infiltrated cells. A preincubation with either MMP-2 or MMP-9 antibodies significantly decreases the gelatinase activity pattern, suggesting the involvement of at least both MMPs. Our results are consistent with a role for MMPs in the blood spinal barrier disruption, the leukocytes infiltration, the disruption of the extracellular matrix and the clearance of debris.     

Three‐dimensional polymer scaffolds for enhanced differentiation of human mesenchymal stem cells to hepatocyte‐like cells: a comparative study

Stem cell‐based tissue engineering has emerged as a promising avenue for the treatment of liver diseases and as drug metabolism and toxicity models in drug discovery and development. The in vitro simulation of a micro‐environmental niche for hepatic differentiation remains elusive, due to lack of information about crucial factors for the stem cell niche. For generation of functional hepatocytes, an in vivo three‐dimensional (3D) micro‐environment and architecture should be reproduced. Towards this, we fabricated three scaffolds as dextran–gelatin (DG1), chitosan–hyaluronic acid (CH1) and gelatin–vinyl acetate (GEVAC). Hepatic differentiation of human umbilical cord‐derived mesenchymal stem cells (hUC‐MSCs) was induced by culturing hUC‐MSCs on these scaffolds. The scaffolds support hepatic differentiation by mimicking the native extracellular matrix (ECM) micro‐environment and architecture to facilitate 3D cell–cell and cell–matrix interactions. The expression of hepatic markers, glycogen storage, urea production, albumin secretion and cytochrome P450 (CYP450) activity indicated the hepatic differentiation of hUC‐MSCs. The differentiated hUC‐MSCs on the 3D scaffolds formed hepatospheroids (3D hepatocyte aggregates), as illustrated by scanning electron microscopy (SEM), confocal microscopy and cytoskeleton organization. It was observed that the 3D scaffolds supported improved cell morphology, expression of hepatic markers and metabolic activities, as compared to Matrigel‐coated plates. To the best of our knowledge, this is the first report demonstrating the use of a well‐characterized scaffold (GEVAC) for enhanced differentiation of hUC‐MSCs to hepatocyte‐like cells (HLCs). Copyright © 2016 John Wiley & Sons, Ltd.     

Type 1 neurofibromatosis: selective expression of extracellular matrix genes by Schwann cells, perineurial cells, and fibroblasts in mixed cultures.

Cutaneous neurofibromas, characteristic lesions of neurofibromatosis 1, are composed of an abundant extracellular matrix and nerve connective tissue-derived cell types: Schwann cells, perineurial cells, and fibroblasts. In this study, the extracellular matrix gene expression by these cells was examined under culture conditions that allowed them to be metabolically active and readily identifiable by morphologic and immunocytochemical criteria. Northern hybridizations demonstrated expression of genes for type I, III, IV, and VI collagens, as well as for fibronectin, laminin, and elastin. In situ hybridizations revealed that all three cell types expressed pro alpha 1 (I), pro alpha 2 (VI), and laminin B1 chain genes. However, fibroblasts did not contain [35S]cDNA-mRNA hybrids specific for type IV collagen, whereas both Schwann cells and perineurial cells expressed these genes. Perineurial cells and fibroblasts readily expressed the fibronectin gene whereas Schwann cells were essentially devoid of the corresponding mRNA. Perineurial cells also expressed the gene for laminin A chain. The results indicate that the extracellular matrix gene expression profiles of Schwann cells, perineurial cells, and fibroblasts are distinct: all three cell types are capable of expressing some of the genes for extracellular matrix components, such as type I and VI collagens, whereas Schwann cells and perineurial cells may have the primary role in synthesizing basement membrane zone components, type IV collagen and laminin. These observations potentially relate to the mechanisms of growth and development of human neurofibromas. The results attest to the applicability of the methodology utilized here to study other human tumors with mixed cell populations.     

Carnitine and acetylcarnitine modulate mesenchymal differentiation of adult stem cells

Cellular metabolic activity, especially mitochondrial metabolism, plays a vital role in regulating cell proliferation and differentiation. Metabolism could therefore be an important factor to consider when using engineering technologies to stimulate tissue development and repair. The small metabolite carnitine and its derivative acetylcarnitine affect the activities of several pathways in mitochondrial metabolism, but their influence on cell differentiation has not yet been thoroughly studied. To elucidate the effects of these two small molecules on mesenchymal tissue engineering, we used adult stem cells as a platform in both monolayer and 3D hydrogel culture systems. We investigated the impact of these two small molecules on the differentiation of adult stem cells and analysed gene expression, cell proliferation and extracellular matrix deposition. We found that the molecules reduced adipogenesis but stimulated osteogenesis and chondrogenesis in both culture systems. Our results suggest that carnitine and acetylcarnitine could affect the differentiation rate of adult stem cells by regulating mitochondrial metabolism. The effects of these two small molecules give rise to the possibility of employing such metabolites in tissue‐engineering systems to enhance cell differentiation and tissue development. Copyright © 2013 John Wiley & Sons, Ltd.     

Cultured cell‐derived extracellular matrices to enhance the osteogenic differentiation and angiogenic properties of human mesenchymal stem/stromal cells

Cell‐derived extracellular matrix (ECM) consists of a complex assembly of fibrillary proteins, matrix macromolecules, and associated growth factors that mimic the composition and organization of native ECM micro‐environment. Therefore, cultured cell‐derived ECM has been used as a scaffold for tissue engineering settings to create a biomimetic micro‐environment, providing physical, chemical, and mechanical cues to cells, and support cell adhesion, proliferation, migration, and differentiation. Here, we present a new strategy to produce different combinations of decellularized cultured cell‐derived ECM (dECM) obtained from different cultured cell types, namely, mesenchymal stem/stromal cells (MSCs) and human umbilical vein endothelial cells (HUVECs), as well as the coculture of MSC:HUVEC and investigate the effects of its various compositions on cell metabolic activity, osteogenic differentiation, and angiogenic properties of human bone marrow (BM)‐derived MSCs, vital features for adult bone tissue regeneration and repair. Our findings demonstrate that dECM presented higher cell metabolic activity compared with tissue culture polystyrene. More importantly, we show that MSC:HUVEC ECM enhanced the osteogenic and angiogenic potential of BM MSCs, as assessed by in vitro assays. Interestingly, MSC:HUVEC (1:3) ECM demonstrated the best angiogenic response of MSCs in the conditions tested. To the best of our knowledge, this is the first study that demonstrates that dECM derived from a coculture of MSC:HUVEC impacts the osteogenic and angiogenic capabilities of BM MSCs, suggesting the potential use of MSC:HUVEC ECM as a therapeutic product to improve clinical outcomes in bone regeneration.     

Oxygen metabolites stimulate release of high-molecular-weight glycoconjugates by cell and organ cultures of rodent respiratory epithelium via an arachidonic acid-dependent mechanism.

Several common pulmonary disorders characterized by mucus hypersecretion and airway obstruction may relate to increased levels of inhaled or endogenously generated oxidants (O2 metabolites) in the respiratory tract. We found that O2 metabolites stimulated release of high-molecular-weight glycoconjugates (HMG) by respiratory epithelial cells in vitro through a mechanism involving cyclooxygenase metabolism of arachidonic acid. Noncytolytic concentrations of chemically generated O2 metabolites (purine + xanthine oxidase) stimulated HMG release by cell and explant cultures of rodent airway epithelium, an effect which is inhibitable by coaddition of specific O2 metabolite scavengers or inhibitors of arachidonic acid metabolism. Addition of O2 metabolites to epithelial cells provoked production of PGF2a, an effect also inhibitable by coaddition of O2 metabolite scavengers or inhibitors of arachidonic acid metabolism. Finally, addition of exogenous PGF2a to cell cultures stimulated HMG release. We conclude that O2 metabolites increase release of respiratory HMG through a mechanism involving cyclooxygenase metabolism of arachidonic acid with production mainly of PGF2a. This mechanism may be fundamental to the pathogenesis of a variety of lung diseases associated with hypersecretion of mucus and/or other epithelial fluids, as well as a basic cellular response to increased oxidants.     

De novo production of human extracellular matrix supports increased throughput and cellular complexity in 3D skin equivalent model

Three‐dimensional (3D) tissue models of human skin are being developed to better understand disease phenotypes and to screen new drugs for potential therapies. Several factors will increase the value of these in vitro 3D skin tissues for these purposes. These include the need for human‐derived extracellular matrix (ECM), higher throughput tissue formats, and greater cellular complexity. Here, we present an approach for the fabrication of 3D skin‐like tissues as a platform that addresses these three considerations. We demonstrate that human adult and neonatal fibroblasts deposit an endogenous ECM de novo that serves as an effective stroma for full epithelial tissue development and differentiation. We have miniaturized these tissues to a 24‐well format to adapt them for eventual higher throughput drug screening. We have shown that monocytes from the peripheral blood can be incorporated into this model as macrophages to increase tissue complexity. This humanized skin‐like tissue decreases dependency on animal‐derived ECM while increasing cellular complexity that can enable screening inflammatory responses in tissue models of human skin.