Fibrillin assemblies: extracellular determinants of tissue formation and fibrosis

Skeletal muscle transcriptomics of sheep acclimated to cold desert and tropical regions identifies genes and pathways accentuating their diversity

The current study attempts to investigate the differences in gene expression in longissimus thoracis muscles between sheep breeds acclimated to diverse environments. Changthangi sheep inhabits the cold arid plateau of Ladakh, at an altitude above 3000 m with prevalence of rarefied atmosphere. Muzzafarnagri sheep, on the other hand is found in the sub-tropical hot and humid plains at an altitude of about 250 m. Comparative transcriptomics was used to provide a molecular perspective of the differential adaptation of the two breeds. RNA sequencing data was generated from four biological replicates of the longissimus thoracis muscles from both breeds. The common genes expressed in both breeds were involved in muscle contraction and muscle fibre organization. The most significant pathways enriched in Changthangi muscles were glycogen metabolism, reduction of cytosolic Ca++ levels and NFE2L2 regulating anti-oxidant, while those in Muzzafarnagri were extracellular matrix organization and collagen formation. The hub genes identified in Changthangi were involved in hematopoiesis and HIF signaling pathway, suggesting the molecular acclimatization of Changthangi to the high altitude cold desert of Ladakh. The nodal genes discovered in Muzzafarnagri sheep were associated with the extracellular matrix which accentuates its significance in the development, growth and repair of muscles. The observed transcriptomic differences underscore the morphological and adaptive disparity between the two breeds. The candidate genes and pathways identified in this study will form the basis for future research on adaptation to high altitude and body size in small ruminants.

Proteomic analysis of aqueous humor reveals novel regulators of diabetic macular edema

Diabetic macular edema (DME) is the most common cause of blindness in patients with diabetic retinopathy. To investigate the proteomic profiles of the aqueous humor (AH) of individuals with diabetic macular edema (DME), AH samples were collected from patients with non-diabetes mellitus (NDM), DM, nonproliferative diabetic retinopathy (NPDR), and DME. We performed comparative proteomic analyses using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and bioinformatics analyses. We identified 425 proteins in these AH samples, of which 113 showed changes in expression in DME compared with NDM, 95 showed changes in expression in DME vs. DM, and 84 showed changes in expression in DME compared with NPDR. The bioinformatics analysis suggested that DME is closely associated with platelet degranulation, oxidative stress-related pathway, and vascular-related pathways. Upregulation of haptoglobin (HP) and downregulation of fibrillin 1 (FBN1) were validated by ELISA. Receiver operating characteristic (ROC) analysis showed that HP and FBN1 could distinguish DME from NPDR with areas under the curve of 0.987 (p = 0.00608) and 0.791 (p = 0.00629), respectively. The findings provide potential clues for further analysis of the molecular mechanisms and the development of new treatments for DME. HP and FBN1 may be potential key proteins and therapeutic targets in human DME. The proteomics dataset generated has been deposited to the ProteomeXchange/iProX Consortium with Identifier: PXD033404/IPX0004353001.

Residual periodontal ligament in the extraction socket promotes the dentin regeneration potential of DPSCs in the rabbit jaw

BACKGROUND

Because of the low regeneration efficiency and unclear underlying molecular mechanism, tooth regeneration applications are limited. In this study, we explored the influence of residual periodontal ligament on the dentin regeneration potential of dental pulp stem cells (DPSCs) in the jaw.

METHODS

To establish a tooth regeneration model, the incisors of New Zealand white rabbits were extracted while preserving residual periodontal ligament, followed by the implantation of DPSCs. After 3 months, micro-computed tomography (micro-CT), stereomicroscopy and scanning electron microscopy (SEM) were used to observe the volume, morphology and microstructure of regenerated tissue. Histological staining and immunostaining analyses were used to observe the morphological characteristics and expression of the dentin-specific proteins DMP1 and DSPP. To explore the mechanism, DPSCs and periodontal ligament stem cells (PDLSCs) were cocultured in vitro, and RNA was collected from the DPSCs for RNA-seq and bioinformatic analysis.

RESULTS

The results of micro-CT and stereomicroscopy showed that the number of sites with regeneration and the volume of regenerated tissue in the DPSCs/PDL group (6/8, 1.07 ± 0.93 cm³) were larger than those in the DPSCs group (3/8, 0.23 ± 0.41 cm³). The results of SEM showed that the regenerated dentin-like tissue in the DPSCs and DPSCs/PDL groups contained dentin tubules. Haematoxylin and eosin staining and immunohistochemical staining indicated that compared with the DPSCs group, the DPSCs/PDL group showed more regular regenerated tissue and higher expression levels of the dentin-specific proteins DMP1 and DSPP (DMP1: P = 0.02, DSPP: P = 0.01). RNA-seq showed that the coculture of DPSCs with PDLSCs resulted in the DPSCs differentially expressing 427 mRNAs (285 upregulated and 142 downregulated), 41 lncRNAs (26 upregulated and 15 downregulated), 411 circRNAs (224 upregulated and 187 downregulated), and 19 miRNAs (13 upregulated and 5 downregulated). Bioinformatic analysis revealed related Gene Ontology function and signalling pathways, including extracellular matrix (ECM), tumour necrosis factor (TNF) signalling and chemokine signalling pathways.

CONCLUSIONS

Residual periodontal ligament in the extraction socket promotes the dentin regeneration potential of DPSCs in the jaw. RNA-seq and bioinformatic analysis revealed that ECM, TNF signalling and chemokine signalling pathways may represent the key factors and signalling pathways.

Myelofibrosis progression grading based on type I and type III collagen and fibrillin 1 expression boosted by whole slide image analysis

AIMS

The progression of primary myelofibrosis is characterised by ongoing extracellular matrix deposition graded based on 'reticulin' and 'collagen' fibrosis, as revealed by Gomori's silver impregnation. Here we studied the expression of the major extracellular matrix proteins of fibrosis in relation to diagnostic silver grading supported by image analysis.

METHODS AND RESULTS

By using automated immunohistochemistry, in this study we demonstrate that the expression of both types I and III collagens and fibrillin 1 by bone marrow stromal cells can reveal the extracellular matrix scaffolding in line with myelofibrosis progression as classified by silver grading. 'Reticulin' fibrosis indicated by type III collagen expression and 'collagen' fibrosis featured by type I collagen expression were parallel, rather than sequential, events. This is line with the proposed role of type III collagen in regulating type I collagen fibrillogenesis. The uniformly strong fibrillin 1 immune signals offered the best inter-rater agreements and the highest statistical correlations with silver grading of the three markers, which was robustly confirmed by automated whole slide digital image analysis using a machine learning-based algorithm. The progressive up-regulation of fibrillin 1 during myelofibrosis may result from a negative feedback loop as fibrillin microfibrils sequester TGF-β, the major promoter of fibrosis. This can also reduce TGF-β-induced RANKL levels, which would stimulate osteoclastogenesis and thus can support osteosclerosis in advanced myelofibrosis.

CONCLUSIONS

Through the in-situ detection of these extracellular matrix proteins, our results verify the molecular pathobiology of fibrosis during myelofibrosis progression. In particular, fibrillin 1 immunohistochemistry, with or without image analysis, can complement diagnostic silver grading at decent cell morphology.

Multi-Scale Analysis of the Composition, Structure, and Function of Decellularized Extracellular Matrix for Human Skin and Wound Healing Models

The extracellular matrix (ECM) is a complex mixture of structural proteins, proteoglycans, and signaling molecules that are essential for tissue integrity and homeostasis. While a number of recent studies have explored the use of decellularized ECM (dECM) as a biomaterial for tissue engineering, the complete composition, structure, and mechanics of these materials remain incompletely understood. In this study, we performed an in-depth characterization of skin-derived dECM biomaterials for human skin equivalent (HSE) models. The dECM materials were purified from porcine skin, and through mass spectrometry profiling, we quantified the presence of major ECM molecules, including types I, III, and VI collagen, fibrillin, and lumican. Rheological analysis demonstrated the sol-gel and shear-thinning properties of dECM materials, indicating their physical suitability as a tissue scaffold, while electron microscopy revealed a complex, hierarchical structure of nanofibers in dECM hydrogels. The dECM materials were compatible with advanced biofabrication techniques, including 3D printing within a gelatin microparticle support bath, printing with a sacrificial material, or blending with other ECM molecules to achieve more complex compositions and structures. As a proof of concept, we also demonstrate how dECM materials can be fabricated into a 3D skin wound healing model using 3D printing. Skin-derived dECM therefore represents a complex and versatile biomaterial with advantageous properties for the fabrication of next-generation HSEs.

Identification of Novel FBN2 Variants in a Cohort of Congenital Contractural Arachnodactyly

Congenital contractural arachnodactyly (CCA) is a rare autosomal dominant disorder of connective tissue characterized by crumpled ears, arachnodactyly, camptodactyly, large joint contracture, and kyphoscoliosis. The nature course of CCA has not been well-described. We aim to decipher the genetic and phenotypic spectrum of CCA. The cohort was enrolled in Beijing Jishuitan Hospital and Peking Union Medical College Hospital, Beijing, China, based on Deciphering disorders Involving Scoliosis and COmorbidities (DISCO) study (http://www.discostudy.org/). Exome sequencing was performed on patients’ blood DNA. A recent published CCA scoring system was validated in our cohort. Seven novel variants and three previously reported FBN2 variants were identified through exome sequencing. Two variants outside of the neonatal region of FBN2 gene were found. The phenotypes were comparable between patients in our cohort and previous literature, with arachnodactyly, camptodactyly and large joints contractures found in almost all patients. All patients eligible for analysis were successfully classified into likely CCA based on the CCA scoring system. Furthermore, we found a double disease-causing heterozygous variant of FBN2 and ANKRD11 in a patient with blended phenotypes consisting of CCA and KBG syndrome. The identification of seven novel variants broadens the mutational and phenotypic spectrum of CCA and may provide implications for genetic counseling and clinical management.

A 36-Year-Old Female With Congenital Contractural Arachnodactyly and Pectus Excavatum Requiring Fourth-Time Redo Surgical Correction

Congenital contractural arachnodactyly (CCA) is a rare connective tissue disorder that has several phenotypic similarities to Marfan syndrome. Among the phenotypic characteristics of patients with CCA, severe kyphoscoliosis and thoracic cage abnormalities are commonly reported. In this case report, we describe a patient with coexisting CCA and severe pectus excavatum requiring multiple surgical repairs. The impact severe scoliosis and pectus excavatum in isolation have on cardiopulmonary anatomy and physiology can be significant, and their effects can be profound concomitantly. These defects have the propensity of causing restrictive lung disease and external cardiac compression.

Spatiotemporal changes in mechanical matrisome components of the human ovary from prepuberty to menopause

STUDY QUESTION

How do elastic matrisome components change during the lifetime of the human ovary?

SUMMARY ANSWER

The deposition and remodeling of mechanical matrisome components (collagen, elastin, elastin microfibril interface-located protein 1 (EMILIN-1), fibrillin-1 and glycosaminoglycans (GAGs)) that play key roles in signaling pathways related to follicle activation and development evolve in an age- and follicle stage-related manner.

WHAT IS KNOWN ALREADY

The mechanobiology of the human ovary and dynamic reciprocity that exists between ovarian cells and their microenvironment is of high importance. Indeed, while the localization of primordial follicles in the collagen-rich ovarian cortex offers a rigid physical environment that supports follicle architecture and probably plays a role in their survival, ovarian extracellular matrix (ECM) stiffness limits follicle expansion and hence oocyte maturation, maintaining follicles in their quiescent state. As growing follicles migrate to the medulla of the ovary, they encounter a softer, more pliant ECM, allowing expansion and development. Thus, changes in the rigidity of the ovarian ECM have a direct effect on follicle behavior. Evidence supporting a role for the physical environment in follicle activation was provided in clinical practice by ovarian tissue fragmentation, which promoted actin polymerization and disrupted ovarian Hippo signaling, leading to increased expression of downstream growth factors, promotion of follicle growth and generation of mature oocytes.

STUDY DESIGN, SIZE, DURATION

We investigated quantitative spatiotemporal changes in collagen, elastin, EMILIN-1, fibrillin-1 and GAGs from prepuberty to menopause, before conducting a closer analysis of the ECM surrounding follicles, from primordial to secondary stages, in both prepubertal and tissue from women of reproductive age. The study included ovarian tissue (cortex) from 68 patients of different ages: prepubertal (n = 16; mean age [±SD]=8 ± 2 years); reproductive (n = 21; mean age [±SD]=27 ± 4 years); menopausal with estrogen-based HRT (n = 7; mean age [±SD]=58 ± 4 years); and menopausal without HRT (n = 24; mean age [±SD]=61 ± 5 years).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Quantitative investigations of collagen and GAG deposition in ovarian tissue throughout a woman's lifetime were conducted by analyzing brightfield images. Characteristic features of collagen fiber content were based on polarized light microscopy, since polarized light changes with fiber thickness. To evaluate the deposition and distribution of elastin, fibrillin-1 and EMILIN-1, multiplex immunofluorescence was used on at least three sections from each patient. Image processing and tailored bioinformatic analysis were applied to enable spatiotemporal quantitative evaluation of elastic system component deposition in the human ovary over its lifetime.

MAIN RESULTS AND THE ROLE OF CHANCE

While collagen levels increased with age, fibrillin-1 and EMILIN-1 declined. Interestingly, collagen and elastin reached their peak in reproductive-age women compared to prepubertal (P < 0.01; P = 0.262) and menopausal subjects with (P = 0.706; P < 0.01) and without (P = 0.987; P = 0.610) HRT, indicating a positive impact of secreted estrogen and hormone treatment on collagen and elastin preservation. Interestingly, HRT appears to affect elastin presence in ovarian tissue, since a significantly higher (P < 0.05) proportion of elastin was detected in biopsies from menopausal women taking HRT compared to those not. Higher GAG levels were found in adult ovaries compared to prepubertal ovaries (P < 0.05), suggesting changes in tissue ultrastructure and elasticity with age. In this context, elevated GAG values are suspected to participate in hampering formation of the fibrillin-1 network (r = -0.2475; P = 0.04687), which explains its decline over time. This decline partially accounts for the decrease in EMILIN-1 (r = 0.4149; P = 0.00059). Closer examination of the ECM surrounding follicles from the primordial to the secondary stage, both before and after puberty, points to high levels of mechanical stress placed on prepubertal follicles compared to the more compliant ECM around reproductive-age follicles, as suggested by the higher collagen levels and lower elastin content detected mainly around primordial (P < 0.0001; P < 0.0001, respectively) and primary (P < 0.0001; P < 0.001, respectively) follicles. Such a stiff niche is nonpermissive to prepubertal follicle activation and growth, and is more inclined to quiescence.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

The duration and form of administered HRT were not considered when studying the menopausal patient group undergoing treatment. Moreover, we cannot exclude interference from other nongynecological medications taken by the study patients on ovarian ECM properties since there is no information in the literature describing the impact of each medication on the ECM. Finally, since the ECM is by definition a very heterogeneous meshwork of proteins, the use of two-dimensional histology could be a limitation. Single time points on fixed tissues could also present limitations, since following ovary dynamics from prepuberty to menopause in the same patient is not feasible.

WIDER IMPLICATIONS OF THE FINDINGS

From a biomechanical perspective, our study revealed important changes to ECM properties dictating the mechanical features of ovarian tissue, in line with the existing literature. Our findings pave the way for possible therapeutic targets at the ECM level in the context of female fertility and ovarian rejuvenation, such as mechanical stimulation, antifibrotic treatments, and prevention or reversion of elastic ECM degradation. Our study also sheds light on the follicle-specific ECM composition that is dependent on follicle stage and age. These data will prove very useful in designing biomimetic scaffolds and tissue-engineered models like the artificial ovary. Indeed, they emphasize the importance of encapsulating each type of isolated follicle in an appropriate biomaterial that must replicate the corresponding functional perifollicular ECM and respect ovarian tissue heterogeneity in order to guarantee its biomimicry.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (FNRS) (C.A.A. is an FRS-FNRS research associate; grant 5/4/150/5 awarded to M.M.D.) and the Université Catholique de Louvain (PhD grant 'Coopération au développement' awarded to E.O.). None of the authors have any competing interests to declare.

Reversion-inducing cysteine-rich protein with Kazal motifs and MT1-MMP promote the formation of robust fibrillin fibers

Fibrillins (FBNs) form mesh-like structures of microfibrils in various elastic tissues. RECK and FBN1 are co-expressed in many human tissues, suggesting a functional relationship. We found that dermal FBN1 fibers show atypical morphology in mice with reduced RECK expression (RECK-Hypo mice). Dermal FBN1 fibers in mice-lacking membrane-type 1-matrix metalloproteinase (MT1-MMP) show a similar atypical morphology, despite the current notion that MT1-MMP (a membrane-bound protease) and RECK (a membrane-bound protease inhibitor) have opposing functions. Our experiments using dermal fibroblasts indicated that RECK promotes pro-MT1-MMP activation, increases cell-associated gelatinase/collagenase activity, and decreases diffusible gelatinase/collagenase activity, while MT1-MMP stabilizes RECK in these cells. Experiments using purified proteins indicate that RECK and its binding partner ADAMTS10 keep the proteolytic activity of MT1-MMP within a certain range. These findings suggest that RECK, ADAMTS10, and MT1-MMP cooperate to support the formation of robust FBN1 fibers.

Molecular Aspects of Regeneration Mechanisms in Holothurians

Holothurians, or sea cucumbers, belong to the phylum Echinodermata. They show good regenerative abilities. The present review provides an analysis of available data on the molecular aspects of regeneration mechanisms in holothurians. The genes and signaling pathways activated during the asexual reproduction and the formation of the anterior and posterior parts of the body, as well as the molecular mechanisms that provide regeneration of the nervous and digestive systems, are considered here. Damage causes a strong stress response, the signs of which are recorded even at late regeneration stages. In holothurian tissues, the concentrations of reactive oxygen species and antioxidant enzymes increase. Furthermore, the cellular and humoral components of the immune system are activated. Extracellular matrix remodeling and Wnt signaling play a major role in the regeneration in holothurians. All available morphological and molecular data show that the dedifferentiation of specialized cells in the remnant of the organ and the epithelial morphogenesis constitute the basis of regeneration in holothurians. However, depending on the type of damage, the mechanisms of regeneration may differ significantly in the spatial organization of regeneration process, the involvement of different cell types, and the depth of reprogramming of their genome (dedifferentiation or transdifferentiation).

The systemic influence of chronic smoking on skin structure and mechanical function

One of the major functions of human skin is to provide protection from the environment. Although we cannot entirely avoid, for example, sun exposure, it is likely that exposure to other environmental factors could affect cutaneous function. A number of studies have identified smoking as one such factor that leads to both facial wrinkle formation and a decline in skin function. In addition to the direct physical effects of tobacco smoke on skin, its inhalation has additional profound systemic effects for the smoker. The adverse effects on the respiratory and cardiovascular systems from smoking are well known. Central to the pathological changes associated with smoking is the elastic fibre, a key component of the extracellular matrices of lungs. In this study we examined the systemic effect of chronic smoking (>40 cigarettes/day; >5 years) on the histology of the cutaneous elastic fibre system, the nanostructure and mechanics of one of its key components, the fibrillin-rich microfibril, and the micromechanical stiffness of the dermis and epidermis. We show that photoprotected skin of chronic smokers exhibits significant remodelling of the elastic fibre network (both elastin and fibrillin-rich microfibrils) as compared to the skin of age- and sex-matched non-smokers. This remodelling is not associated with increased gelatinase activity (as identified by in situ zymography). Histological remodelling is accompanied by significant ultrastructural changes to extracted fibrillin-rich microfibrils. Finally, using scanning acoustic microscopy, we demonstrated that chronic smoking significantly increases the stiffness of both the dermis and the epidermis. Taken together, these data suggest an unappreciated systemic effect of chronic inhalation of tobacco smoke on the cutaneous elastic fibre network. Such changes may in part underlie the skin wrinkling and loss of skin elasticity associated with smoking. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

A disease-associated mutation in fibrillin-1 differentially regulates integrin-mediated cell adhesion

Fibrillins serve as scaffolds for the assembly of elastic fibers that contribute to the maintenance of tissue homeostasis and regulate growth factor signaling in the extracellular space. Fibrillin-1 is a modular glycoprotein that includes 7 latent transforming growth factor β (TGFβ)-binding protein-like (TB) domains and mediates cell adhesion through integrin binding to the RGD motif in its 4th TB domain. A subset of missense mutations within TB4 cause stiff skin syndrome (SSS), a rare autosomal dominant form of scleroderma. The fibrotic phenotype is thought to be regulated by changes in the ability of fibrillin-1 to mediate integrin binding. We characterized the ability of each RGD-binding integrin to mediate cell adhesion to fibrillin-1 or a disease-causing variant. Our data show that 7 of the 8 RGD-binding integrins can mediate adhesion to fibrillin-1. A single amino acid substitution responsible for SSS (W1570C) markedly inhibited adhesion mediated by integrins α5β1, αvβ5, and αvβ6, partially inhibited adhesion mediated by αvβ1, and did not inhibit adhesion mediated by α8β1 or αIIbβ3. Adhesion mediated by integrin αvβ3 depended on the cell surface expression level. In the SSS mutant background, the presence of a cysteine residue in place of highly conserved tryptophan 1570 alters the conformation of the region containing the exposed RGD sequence within the same domain to differentially affect fibrillin's interactions with distinct RGD-binding integrins.

Proteomics reveals a set of highly enriched proteins in epiretinal membrane compared with inner limiting membrane

Few data exist regarding the protein composition of idiopathic epiretinal membrane (iERM). In the present study we compared the proteome of epiretinal membrane of iERM with the proteome of the inner limiting membrane (ILM) of idiopathic macular hole (iMH). Twelve epiretinal membrane samples were obtained from patients with iERM undergoing therapeutic vitrectomy. Twelve ILM samples from patients with iMH were used as controls. Proteomic analysis was conducted with discovery-based label-free quantitative nano-liquid chromatography - tandem mass spectrometry (LFQ nLC-MS/MS). Verification of results was performed with targeted MS using selected reaction monitoring on a different set of samples. Discovery data were searched against the Uniprot Homo sapiens protein database using MaxQuant Software. Identified proteins were filtered with Perseus software. Bioinformatic analysis of the differences in protein expression between epiretinal membrane from iERM and ILM from iMH was performed using STRING. A total of 2,183 different proteins were identified. 357 proteins were found to be present in all samples. The protein profile of iERM was highly different from iMH with 62 proteins found at significantly higher levels in iERM. The proteins upregulated more than 10-fold in iERM were: fibrillin-1, tenascin, prolargin, biglycan, opticin, collagen alpha-1(II) chain, protein-glutamine gamma-glutamyltransferase 2, fibronectin, filamin-A, collagen alpha-2(IX) chain, spectrin alpha chain, transforming growth factor beta induced protein ig-h3, dihydropyrimidinase - related protein 3, endoplasmin and glutamate dehydrogenase 1. Proteins with high level in iERM consisted of proteins that especially localized to the actin cytoskeleton, the extracellular matrix and the mitochondrion. Analysis of all proteins indicated that the disease process in iERM at least in part can be characterized as skin formation with perturbation of nucleotide metabolism. Our study identified proteins that have not earlier been associated with iERM. Fifteen proteins are found at very high concentration, 10-fold or more, and amongst these four proteins, fibrillin-1, tenascin, prolargin and biglycan were found at more than a 100-fold higher content compared to ILM of iMH. These proteins may be potential therapeutic targets. Data are available via ProteomeXchange with identifier PXD014286.

microRNA-29b mediates fibrotic induction of human xylosyltransferase-I in human dermal fibroblasts via the Sp1 pathway

Diminished microRNA-29b levels have recently been revealed to provoke increased expression and accumulation of extracellular matrix molecules, such as collagens in fibrotic remodeling. Subsequently, the aim of this study was to find out whether microRNA-29b might also regulate human xylosyltransferase (XT)-I expression. XT-I has been characterized previously as a fibrosis biomarker catalyzing the key step of proteoglycan biosynthesis. While we demonstrate that XYLT1 is neither a target of microRNA-29b identified in silico nor a direct 3' untranslated region binding partner of microRNA-29b, transfection of normal human dermal fibroblasts with microRNA-29b inhibitor strongly increased XYLT1 mRNA expression and XT activity. Combined results of the target prediction analysis and additional transfection experiments pointed out that microRNA-29b exerts indirect influence on XT-I by targeting the transcription factor specificity protein 1 (Sp1). We could confirm our hypothesis due to the decrease in XYLT1 promoter activity after Sp1 binding site mutation and the approval of occupancy of these binding sites by Sp1 in vitro. Taken together, a hitherto unidentified pathway of XT-I regulation via microRNA-29b/Sp1 was determined in this study. Our observations will facilitate the understanding of complex molecular fibrotic pathways and provide new opportunities to investigate microRNA-based antifibrotic tools.

MicroRNA-206 suppresses TGF-β signalling to limit tumor growth and metastasis in lung adenocarcinoma

MicroRNA-206 (miR-206) has demonstrated tumor suppressive effects in a variety of cancers. Numerous studies have identified aberrantly expressed targets of miR-206 that contribute to tumor progression and metastasis, however, the broader gene-networks and pathways regulated by miR-206 remain poorly defined. Here, we have ectopically expressed miR-206 in lung adenocarcinoma cell lines and tumors to identify differentially expressed genes, and study the effects on tumor growth and metastasis. In H1299 tumor xenograft assays, stable expression of miR-206 suppressed both tumor growth and metastasis in mice. Profiling of xenograft tumors using small RNA sequencing and a targeted panel of tumor progression and metastasis-related genes revealed a network of genes involved in TGF-β signalling that were regulated by miR-206. Among these were the TGFB1 ligand, as well as direct transcriptional targets of Smad3. Other differentially expressed genes included components of the extracellular matrix involved in TGF-β activation and signalling, including Thrombospondin-1, which is responsible for the activation of latent TGF-β in the stroma. In cultured lung adenocarcinoma cells treated with recombinant TGF-β, ectopic expression of miR-206 impaired canonical signalling, and expression of TGF-β target genes linked to epithelial-mesenchymal transition. This was due at least in part to the suppression of Smad3 protein levels in lung adenocarcinoma cells with ectopic miR-206 expression. Together, these findings indicate that miR-206 can suppress tumor progression and metastasis by limiting autocrine production of TGF-β, and highlight the potential utility of TGF-β inhibitors for the treatment of lung adenocarcinomas.

Molecular mechanisms of fission in echinoderms: Transcriptome analysis

Echinoderms are capable of asexual reproduction by fission. An individual divides into parts due to changes in the strength of connective tissue of the body wall. The structure of connective tissue and the mechanisms of variations in its strength in echinoderms remain poorly studied. An analysis of transcriptomes of individuals during the process of fission provides a new opportunity to understand the mechanisms of connective tissue mutability. In the holothurian Cladolabes schmeltzii, we have found a rather complex organization of connective tissue. Transcripts of genes encoding a wide range of structural proteins of extracellular matrix, as well as various proteases and their inhibitors, have been discovered. All these molecules may constitute a part of the mechanism of connective tissue mutability. According to our data, the extracellular matrix of echinoderms is substantially distinguished from that of vertebrates by the lack of elastin, fibronectins, and tenascins. In case of fission, a large number of genes of transcription factors and components of different signaling pathways are expressed. Products of these genes are probably involved in regulation of asexual reproduction, connective tissue mutability, and preparation of tissues for subsequent regeneration. It has been shown that holothurian tensilins are a special group of tissue inhibitors of metalloproteinases, which has formed within the class Holothuroidea and is absent from other echinoderms. Our data can serve a basis for the further study of the mechanisms of extracellular matrix mutability, as well as the mechanisms responsible for asexual reproduction in echinoderms.

Gene polymorphisms of fibronectin rs2289202 and fibrillin 2 rs331069 associate with vascular disease, the TAMRISK study

Cell surface heparan sulfate (HS) proteoglycans interact with other extracellular matrix (ECM) components, and HS-binding regions are present in ECM proteins such as fibronectin and fibrillin. Because of their previously established role in susceptibility to intracranial aneurysms, the authors sought to determine whether polymorphisms of fibronectin (FN1, rs2289202) and fibrillin 2 (FBN2, rs331069) associate with selected cardiovascular risk factors and events in the TAMRISK study. A 50-year-old Finnish cohort of 810 subjects of whom 340 had diagnosed hypertension was analyzed. Samples were genotyped for FN1 rs2289202 and FBN2 rs331069 polymorphisms. Incidence of myocardial infarction (I21-I22), transient cerebral ischemic attacks (TIA, G45) and cerebrovascular diseases (I60-I69) were followed up until the subjects were on the average 60 years old. Subjects with FN1 rs2289202 (G>A) minor genotype AA had significantly more cerebrovascular disease than those with the G allele [P<0.001, odds ratio (OR), 8.73; confidence index (CI), 2.79-27.31], although those with the A allele had lower body mass index (P=0.008). Subjects with fibrillin rs331069 (T>C) minor genotype CC had more atherothrombotic disease (P=0.012, OR, 3.16; CI, 1.29-7.71), as measured by combined myocardial infarction and TIA, than those with the T allele. The gene polymorphisms for fibronectin and fibrillin 2 appear to associate with vascular disease.

Environmental preconditioning rejuvenates adult stem cells' proliferation and chondrogenic potential

Adult stem cells are a promising cell source for cartilage regeneration. Unfortunately, due to donor age and ex vivo expansion, stem cell senescence becomes a huge hurdle for these cells to be used clinically. Increasing evidence indicates that environmental preconditioning is a powerful approach in promoting stem cells' ability to resist a harsh environment post-engraftment, such as hypoxia and inflammation. However, few reports organize and evaluate the literature regarding the rejuvenation effect of environmental preconditioning on stem cell proliferation and chondrogenic differentiation capacity, which are important variables for stem cell based tissue regeneration. This report aims to identify several critical environmental factors such as oxygen concentration, growth factors, and extracellular matrix and to discuss their preconditioning influence on stem cells' rejuvenation including proliferation and chondrogenic potential as well as underlying molecular mechanisms. We believe that environmental preconditioning based rejuvenation is a simpler and safer strategy to program pre-engraftment stem cells for better survival and enhanced proliferation and differentiation capacity without the undesired effects of some treatments, such as genetic manipulation.

Life under pressure: The role of ocular cribriform cells in preventing glaucoma

Primary open-angle glaucoma is a multifactorial blinding disease often impacting the two pressure-sensitive regions of the eye: the conventional outflow pathway and the optic nerve head (ONH). The connective tissues that span these two openings in the globe are the trabecular meshwork of the conventional outflow pathway and the lamina cribrosa of the ONH. Resident cribiform cells of these two regions are responsible for actively remodeling and maintaining their connective tissues. In glaucoma, aberrant maintenance of the juxtacanalicular tissues (JCT) of the conventional outflow pathway results in ocular hypertension and pathological remodeling of the lamina cribrosa results in ONH cupping, damaging retinal ganglion cell axons. Interestingly, cells cultured from the lamina cribrosa and the JCT of the trabecular meshwork have similarities regarding gene expression, protein production, plus cellular responses to growth factors and mechanical stimuli. This review compares and contrasts the current knowledge of these two cell types, whose health is critical for protecting the eye from glaucomatous changes. In response to pressure gradients across their respective cribiform tissues, the goal is to better understand and differentiate healthy from pathological behavior of these two cell types.

Genetic Predictors of Susceptibility to Dermatophytoses

Countless observational studies conducted over the last century reveal that dermatophytes infect humans of every age, race, gender, and socioeconomic status with strikingly high rates. The curious disparity in dermatophyte infection patterns observed within and between populations has led countless investigators to explore whether genetics underlie a susceptibility to, or confer protection against, dermatophyte infections. This paper examines the data that offer a link between genetics and dermatophytoses and discusses the underlying mechanisms that support these observations.

Agonists and Antagonists of TGF-β Family Ligands

The discovery of the transforming growth factor β (TGF-β) family ligands and the realization that their bioactivities need to be tightly controlled temporally and spatially led to intensive research that has identified a multitude of extracellular modulators of TGF-β family ligands, uncovered their functions in developmental and pathophysiological processes, defined the mechanisms of their activities, and explored potential modulator-based therapeutic applications in treating human diseases. These studies revealed a diverse repertoire of extracellular and membrane-associated molecules that are capable of modulating TGF-β family signals via control of ligand availability, processing, ligand-receptor interaction, and receptor activation. These molecules include not only soluble ligand-binding proteins that were conventionally considered as agonists and antagonists of TGF-β family of growth factors, but also extracellular matrix (ECM) proteins and proteoglycans that can serve as "sink" and control storage and release of both the TGF-β family ligands and their regulators. This extensive network of soluble and ECM modulators helps to ensure dynamic and cell-specific control of TGF-β family signals. This article reviews our knowledge of extracellular modulation of TGF-β growth factors by diverse proteins and their molecular mechanisms to regulate TGF-β family signaling.

Cathepsin-Mediated Alterations in TGFß-Related Signaling Underlie Disrupted Cartilage and Bone Maturation Associated With Impaired Lysosomal Targeting

Hypersecretion of acid hydrolases is a hallmark feature of mucolipidosis II (MLII), a lysosomal storage disease caused by loss of carbohydrate-dependent lysosomal targeting. Inappropriate extracellular action of these hydrolases is proposed to contribute to skeletal pathogenesis, but the mechanisms that connect hydrolase activity to the onset of disease phenotypes remain poorly understood. Here we link extracellular cathepsin K activity to abnormal bone and cartilage development in MLII animals by demonstrating that it disrupts the balance of TGFß-related signaling during chondrogenesis. TGFß-like Smad2,3 signals are elevated and BMP-like Smad1,5,8 signals reduced in both feline and zebrafish MLII chondrocytes and osteoblasts, maintaining these cells in an immature state. Reducing either cathepsin K activity or expression of the transcriptional regulator Sox9a in MLII zebrafish significantly improved phenotypes. We further identify components of the large latent TGFß complex as novel targets of cathepsin K at neutral pH, providing a possible mechanism for enhanced Smad2,3 activation in vivo. These findings highlight the complexity of the skeletal disease associated with MLII and bring new insight to the role of secreted cathepsin proteases in cartilage development and growth factor regulation.

The ocular phenotype of stiff-skin syndrome

PURPOSE Stiff skin syndrome (SSS; MIM#184900) is a rare autosomal dominantly inherited Mendelian disorder characterised by thickened and stone-hard indurations of the skin, mild hypertrichosis, and limitation of joint mobility with flexion contractures. It is autosomal dominant with high penetrance and results from mutations in the fibrillin 1 (FBN1; MIM*134797) gene. Here we present the associated ocular phenotype in a two generation nonconsanguineous Northern Irish family.METHODS The affected patients underwent complete ophthalmic and orthoptic assessment and genetic testing.RESULTS All three patients had ophthalmoplegia of varying degrees. Direct sequencing of the FBN1 gene detected a heterozygous pathogenic mutation (c.4710G>C; p.Trp1570Cys) in all affected patients.CONCLUSIONS This is the first report of ophthalmoplegia in association with SSS.

Chondrogenic priming of human fetal synovium-derived stem cells in an adult stem cell matrix microenvironment

Cartilage defects are a challenge to treat clinically due to the avascular nature of cartilage. Low immunogenicity and extensive proliferation and multidifferentiation potential make fetal stem cells a promising source for regenerative medicine. In this study, we aimed to determine whether fetal synovium-derived stem cells (FSDSCs) exhibited replicative senescence and whether expansion on decellularized extracellular matrix (dECM) deposited by adult SDSCs (AECM) promoted FSDSCs' chondrogenic potential. FSDSCs from passage 2 and 9 were compared for chondrogenic potential, using Alcian blue staining for sulfated glycosaminoglycans (GAGs), biochemical analysis for DNA and GAG amounts, and real-time PCR for chondrogenic genes including ACAN and COL2A1. Passage 3 FSDSCs were expanded for one passage on plastic flasks (PL), AECM, or dECM deposited by fetal SDSCs (FECM). During expansion, cell proliferation was evaluated using flow cytometry for proliferation index, stem cell surface markers, and resistance to hydrogen peroxide. During chondrogenic induction, expanded FSDSCs were evaluated for tri-lineage differentiation capacity. We found that cell expansion enhanced FSDSCs' chondrogenic potential at least up to passage 9. Expansion on dECMs promoted FSDSCs' proliferative and survival capacity and adipogenic differentiation but not osteogenic capacity. AECM-primed FSDSCs exhibited an enhanced chondrogenic potential.

TGFβ signaling promotes matrix assembly during mechanosensitive embryonic salivary gland restoration

Mechanical properties of the microenvironment regulate cell morphology and differentiation within complex organs. However, methods to restore morphogenesis and differentiation in organs in which compliance is suboptimal are poorly understood. We used mechanosensitive mouse salivary gland organ explants grown at different compliance levels together with deoxycholate extraction and immunocytochemistry of the intact, assembled matrices to examine the compliance-dependent assembly and distribution of the extracellular matrix and basement membrane in explants grown at permissive or non-permissive compliance. Extracellular matrix and basement membrane assembly were disrupted in the glands grown at low compliance compared to those grown at high compliance, correlating with defective morphogenesis and decreased myoepithelial cell differentiation. Extracellular matrix and basement membrane assembly as well as myoepithelial differentiation were restored by addition of TGFβ1 and by mechanical rescue, and mechanical rescue was prevented by inhibition of TGFβ signaling during the rescue. We detected a basal accumulation of active integrin β1 in the differentiating myoepithelial cells that formed a continuous peripheral localization around the proacini and in clefts within active sites of morphogenesis in explants that were grown at high compliance. The pattern and levels of integrin β1 activation together with myoepithelial differentiation were interrupted in explants grown at low compliance but were restored upon mechanical rescue or with application of exogenous TGFβ1. These data suggest that therapeutic application of TGFβ1 to tissues disrupted by mechanical signaling should be examined as a method to promote organ remodeling and regeneration.

Immunohistochemical expression of fibrillin-1 and fibrillin-2 during tooth development

BACKGROUND AND OBJECTIVE

Oxytalan fibers are categorized as a microfibril assembly without elastin deposition, and are unique components in the periodontal ligament (PDL). However, little is known about their formation during PDL development. To clarify the mechanisms of oxytalan fiber formation in developing PDL, we performed immunohistochemical analysis to detect the direct expression of fibrillin-1 and fibrillin-2, which are major components of microfibrils.

MATERIAL AND METHODS

Frozen sections of lower molars from mice at several stages of growth were prepared without chemical fixation and decalcification using the film transfer method. Immunostaining was performed with anti-fibrillin-1 and -2, and anticytokeratin antibodies.

RESULTS

Fibrillin-1 was not expressed in the dental follicle during the crown forming stage. At postneonatal day 9, fibrillin-1 expression started with meshwork appearance between the epithelial cells from Hertwig's epithelial root sheath at the root dentin surface. Fibirillin-2 was detected much earlier than fibrillin-1 expression. Fibrillin-2 was expressed with a liner appearance, running parallel to the root axis in PDL, and was partially co-expressed with cytokeratin 14 expression in Hertwig's epithelial root sheath. Furthermore, we detected both fibrillin-1 and fibrillin-2 expression in human PDL. Fibrillin-1 was detected in fibers with a vertically oriented root axis in PDL. Fibrillin-2 was widely expressed in PDL, including around the epithelial cell rests of Malassez. Fibrillin-1 and fibrillin-2 were clearly co-expressed in thick fiber structures in human PDL.

CONCLUSION

Our results suggest that both fibrillin-1 and fibrillin-2 expression is required to form thick oxytalan fibers in PDL. Based on the expression patterns for fibrillin-1 and fibrillin-2, they have different functions during tooth root and PDL development. Early expression of fibrillin-2 may regulate dental epithelial cell behavior during root and PDL development.

Proinflammation of aging central arteries: a mini-review

Arterial aging is a cornerstone of organismal aging. The central arterial wall structurally and functionally remodels under chronic proinflammatory stress over a lifetime. The low-grade proinflammation that accompanies advancing age causes arterial wall thickening and stiffening. These structural and functional alterations are consequences of adverse molecular and cellular events, e.g. an increase in local angiotensin II signaling that induces an inflammatory phenotypic shift of endothelial and smooth muscle cells. Thus, interventions to restrict proinflammatory signaling are a rational approach to delay or prevent age-associated adverse arterial remodeling.

C-terminal propeptide is required for fibrillin-1 secretion and blocks premature assembly through linkage to domains cbEGF41-43

Fibrillin microfibrils are 10-12 nm diameter, extracellular matrix assemblies that provide dynamic tissues of metazoan species with many of their biomechanical properties as well as sequestering growth factors and cytokines. Assembly of fibrillin monomers into microfibrils is thought to occur at the cell surface, with initial steps including proprotein processing, multimerization driven by the C terminus, and the head-to-tail alignment of adjacent molecules. At present the mechanisms that regulate microfibril assembly are still to be elucidated. We have used structure-informed protein engineering to create a recombinant, GFP-tagged version of fibrillin-1 (GFP-Fbn) to study this process. Using HEK293T cells transiently transfected with GFP-Fbn constructs, we show that (i) the C-terminal propeptide is an essential requirement for the secretion of full-length fibrillin-1 from cells; (ii) failure to cleave off the C-terminal propeptide blocks the assembly of fibrillin-1 into microfibrils produced by dermal fibroblasts; and (iii) the requirement of the propeptide for secretion is linked to the presence of domains cbEGF41-43, because either deletion or exchange of domains in this region leads to cellular retention. Collectively, these data suggest a mechanism in which the propeptide blocks a key site at the C terminus to prevent premature microfibril assembly.

Rare and common variants in extracellular matrix gene Fibrillin 2 (FBN2) are associated with macular degeneration

Neurodegenerative diseases affecting the macula constitute a major cause of incurable vision loss and exhibit considerable clinical and genetic heterogeneity, from early-onset monogenic disease to multifactorial late-onset age-related macular degeneration (AMD). As part of our continued efforts to define genetic causes of macular degeneration, we performed whole exome sequencing in four individuals of a two-generation family with autosomal dominant maculopathy and identified a rare variant p.Glu1144Lys in Fibrillin 2 (FBN2), a glycoprotein of the elastin-rich extracellular matrix (ECM). Sanger sequencing validated the segregation of this variant in the complete pedigree, including two additional affected and one unaffected individual. Sequencing of 192 maculopathy patients revealed additional rare variants, predicted to disrupt FBN2 function. We then undertook additional studies to explore the relationship of FBN2 to macular disease. We show that FBN2 localizes to Bruch's membrane and its expression appears to be reduced in aging and AMD eyes, prompting us to examine its relationship with AMD. We detect suggestive association of a common FBN2 non-synonymous variant, rs154001 (p.Val965Ile) with AMD in 10 337 cases and 11 174 controls (OR = 1.10; P-value = 3.79 × 10(-5)). Thus, it appears that rare and common variants in a single gene--FBN2--can contribute to Mendelian and complex forms of macular degeneration. Our studies provide genetic evidence for a key role of elastin microfibers and Bruch's membrane in maintaining blood-retina homeostasis and establish the importance of studying orphan diseases for understanding more common clinical phenotypes.

Rejuvenation of chondrogenic potential in a young stem cell microenvironment

Autologous cells suffer from limited cell number and senescence during ex vivo expansion for cartilage repair. Here we found that expansion on extracellular matrix (ECM) deposited by fetal synovium-derived stem cells (SDSCs) (FE) was superior to ECM deposited by adult SDSCs (AE) in promoting cell proliferation and chondrogenic potential. Unique proteins in FE might be responsible for the rejuvenation effect of FE while advantageous proteins in AE might contribute to differentiation more than to proliferation. Compared to AE, the lower elasticity of FE yielded expanded adult SDSCs with lower elasticity which could be responsible for the enhancement of chondrogenic and adipogenic differentiation. MAPK and noncanonical Wnt signals were actively involved in ECM-mediated adult SDSC rejuvenation.

Immunolocalisation of fibrillin microfibrils in the calf metacarpal and vertebral growth plate

Overgrowth of limbs and spinal deformities are typical clinical manifestations of Marfan syndrome (MFS) and congenital contractural arachnodactyly (CCA), caused by mutations of the genes encoding fibrillin-1 (FBN1) and fibrillin-2 (FBN2), respectively. FBN1 mutations are also associated with acromicric (AD) and geleophysic dysplasias (GD), and with Weill-Marchesani syndrome (WMS), which is characterised by short stature. The mechanisms leading to such abnormal skeletal growth and the involvement of the fibrillins are not understood. Postnatal longitudinal bone growth mainly occurs in the epiphyseal growth plate. Here we investigated the organisation of fibrillin microfibrils in the growth plate of the long bone and vertebra immunohistochemically. Fibrillin-1 was dual-immunostained with elastin, with fibrillin-2 or with collagen X. We report that fibrillin microfibrils are distributed throughout all regions of the growth plate, and that fibrillin-1 and fibrillin-2 were differentially organised. Fibrillin-1 was more abundant in the extracellular matrix of the resting and proliferative zones of the growth plate than in the hypertrophic zone. More fibrillin-2 was found in the calcified region than in the other regions. No elastin fibres were observed in either the proliferative or hypertrophic zones. This study indicates that, as fibrillin microfibrils are involved in growth factor binding and may play a mechanical role, they could be directly involved in regulating bone growth. Hence, mutations of the fibrillins could affect their functional role in growth and lead to the growth disorders seen in patients with MFS, CCA, AD, GD and WMS.

Early cell changes and TGFβ pathway alterations in the aortopathy associated with bicuspid aortic valve stenosis

Previous studies on BAV (bicuspid aortic valve)-related aortopathy, whose aetiology is still debated, have focused mainly on severe dilatations. In the present study, we aimed to detect earlier signs of aortopathy. Specimens were collected from the 'concavity' (lesser curvature) and the 'convexity' (greater curvature) of mildly dilated AAs (ascending aortas; diameter ≤4 cm) with stenotic TAV (tricuspid aortic valve) or BAV and from donor normal aortas. Specimens were submitted to morphometry, immunohistochemistry and differential gene-expression analysis, focusing on SMC (smooth muscle cell) phenotype, remodelling, MF (myofibroblast) differentiation and TGFβ (transforming growth factor β) pathway. Smoothelin and myocardin mRNAs decreased in all the samples from patients, with the exception of those from BAV convexity, where a change in orientation of smoothelin-positive SMCs and an increase of α-SMA (α-smooth muscle actin) mRNA occurred. Dilated aortas from BAV and TAV patients showed both shared and distinct alterations concerning the TGFβ pathway, including an increased TGFβ and TGFβR2 (TGFβ receptor 2) expression in both groups and a decreased TGFβR1 expression in BAV samples only. Despite a decrease of the mRNA coding for the ED-A (extra domain-A) isoform of FN (fibronectin) in the BAV convexity, the onset of the expression of the corresponding protein in the media was observed in dilated aortas, whereas the normal media from donors was negative for this isoform. This discrepancy could be related to modifications in the intima, normally expressing ED-A FN and showing an altered structure in mild aortic dilatations in comparison with donor aorta. Our results suggest that changes in SMC phenotype and, likely, MF differentiation, occur early in the aortopathy associated with valve stenosis. The defective expression of TGFβR1 in BAV might be a constitutive feature, while other changes we reported could be influenced by haemodynamics.

Structure and function of the mammalian fibrillin gene family: implications for human connective tissue diseases

Fibrillins and latent transforming growth factor β binding proteins (LTBPs) are components of the extracellular matrix of connective tissue. While fibrillins are integral to the 10nm microfibrils, and often associated with elastin, all family members are likely to have an additional role in regulating the bioavailability of transforming growth factor β (TGBβ). Both fibrillins and LTBPs are large glycoproteins, containing a series of calcium binding epidermal growth factor domains as well as a number of copies of a unique 8 cysteine domain found only in this protein superfamily. There are three mammalian fibrillins and four LTBPs. Fibrillin monomers link head to tail in microfibrils which can then form two and three dimensional structures. In some tissues elastin is recruited to the fibrillin microfibrils to provide elasticity to the tissue. LTBPs are part of the TGBβ large latent complex which sequesters TGBβ in the extracellular matrix. Fibrillin-1 appears to bind to LTBPs to assist in this process and is thus involved in regulating the bioavailability of TGBβ. Mutation of fibrillin genes results in connective tissue phenotypes which reflect both the increased level of active TGBβ and the structural failure of the extracellular matrix due to the absence or abnormality of fibrillin protein. Fibrillinopathies include Marfan syndrome, familial ectopia lentis, familial thoracic aneurysm (mutations of FBN1) and congenital contractural arachnodactyly (mutation of FBN2). There are no diseases currently associated with mutation of FBN3 in humans, and this gene is no longer active in rodents. Expression patterns of fibrillin genes are consistent with their role in extracellular matrix structure of connective tissue. FBN1 expression is high in most cell types of mesenchymal origin, particularly bone. Human and mouse FBN2 expression is high in fetal cells and has more restricted expression in mesenchymal cell types postnatally. FBN3 is expressed early in development (embryonic and fetal tissues) in humans. The fibrillins are thus important in maintaining the structure and integrity of the extracellular matrix and, in combination with their sequence family members the LTBPs, also contribute to the regulation of the TGFβ family of major growth factors.

Fibrillin-2, tenascin-C, matrilin-2, and matrilin-4 are strongly expressed in the epithelium of human granular and lattice type I corneal dystrophies

PURPOSE

To determine the extracellular matrix proteins involved in the formation of human granular and lattice type I corneal stromal dystrophies, the expression patterns of fibrillin-2, tenascin-C, matrilin-2, and matrilin-4 were compared in human corneal stromal dystrophy samples.

METHODS

Ten cases of granular dystrophy, 7 cases of lattice dystrophy, and 6 normal corneal buttons collected during corneal transplantation were examined for their expression patterns of fibrillin-2, tenascin-C, matrilin-2, and matrilin-4 by immunohistochemistry.

RESULTS

Highly elevated fibrillin-2, tenascin-C, matrilin-2, and matrilin-4 were observed in the epithelial layer of both granular and lattice type I dystrophies. Fibrillin-2, tenascin-C, and matrilin-4 in the granular dystrophy and all antibodies in the lattice dystrophy showed statistically significant staining in the corneal stroma (p<0.05). Interestingly, fibrillin-2, matrilin-2, and matrilin-4 stained significantly in amyloid plaques of lattice type 1 dystrophy.

CONCLUSIONS

Fibrillin-2, tenascin-C, matrilin-2, and matrilin-4 may be markers of the pathogenesis of either granular or lattice type I corneal dystrophy, as revealed by immunohistochemical analysis. Each molecule seems to be involved in the regeneration and reorganization of the corneal matrix in granular and lattice type I dystrophies.

Structure and function of ameloblastin as an extracellular matrix protein: adhesion, calcium binding, and CD63 interaction in human and mouse

The functional significance of extracellular matrix proteins in the life of vertebrates is underscored by a high level of sequence variability in tandem with a substantial degree of conservation in terms of cell-cell and cell-matrix adhesion interactions. Many extracellular matrix proteins feature multiple adhesion domains for successful attachment to substrates, such as integrin, CD63, and heparin. Here we have used homology and ab initio modeling algorithms to compare mouse ameloblastin (mAMBN) and human ameloblastin (hABMN) isoforms and to analyze their potential for cell adhesion and interaction with other matrix molecules as well as calcium binding. Sequence comparison between mAMBN and hAMBN revealed a 26-amino-acid deletion in mAMBN, corresponding to a helix-loop-helix frameshift. The human AMBN domain (174Q-201G), homologous to the mAMBN 157E-178I helix-loop-helix region, formed a helix-loop motif with an extended loop, suggesting a higher degree of flexibility of hAMBN compared with mAMBN, as confirmed by molecular dynamics simulation. Heparin-binding domains, CD63-interaction domains, and calcium-binding sites in both hAMBN and mAMBN support the concept of AMBN as an extracellular matrix protein. The high level of conservation between AMBN functional domains related to adhesion and differentiation was remarkable when compared with only 61% amino acid sequence homology.

Genetic predictors of susceptibility to cutaneous fungal infections: a pilot genome wide association study to refine a candidate gene search

BACKGROUND

Trichophyton tonsurans is the foremost fungal pathogen of minority children in the U.S. Despite overwhelming infection rates, it does not appear that this fungus infects children in a non-specific manner.

OBJECTIVE

This study was designed to identify genes that may predispose or protect a child from T. tonsurans infection.

METHODS

Children participating in an earlier longitudinal study wherein infection rates could be reliably determined were eligible for inclusion. DNA from a subset (n=40) of these children at the population extremes underwent whole genome genotyping (WGG). Allele frequencies between cases and controls were examined and significant SNPs were used to develop a candidate gene list for which the remainder of the cohort (n=115) were genotyped. Cumulative infection rate was examined by genotype and the ability of selected genotypes to predict the likelihood of infection explored by multivariable analysis.

RESULTS

23 genes with a putative mechanistic role in cutaneous infection were selected for evaluation. Of these, 21 demonstrated significant differences in infection rate between genotypes. A risk index assigned to genotypes in the 21 genes accounted for over 60% of the variability observed in infection rate (adjusted r(2)=0.665, p<0.001). Among these, 8 appeared to account for the majority of variability that was observed (r(2)=0.603, p<0.001). These included genes involved in: leukocyte activation and migration, extracellular matrix integrity and remodeling, epidermal maintenance and wound repair, and cutaneous permeability.

CONCLUSIONS

Applying WGG to individuals at the extremes of phenotype can help to guide the selection of candidate genes in populations of small cohorts where disease etiology is likely polygenic in nature.

LTBPs, more than just an escort service

Latent transforming growth factor beta (TGF-β) binding proteins (LTBPs) are large extracellular glycoproteins structurally similar to fibrillins. They perform intricate and important roles in the extracellular matrix (ECM) and perturbations of their function manifest as a wide range of diseases. LTBPs are major regulators of TGF-β bioavailability and action. In addition, LTBPs interact with other ECM proteins-from cytokines to large multi-factorial aggregates like microfibrils and elastic fibers, affecting their genesis, structure, and performance. In the present article, we review recent advancements in the field and relate the complex roles of LTBP in development and homeostasis.