Distinctive roles of fibrillar collagen I and collagen III in mediating fibroblast-matrix interaction: A nanoscopic study.

One major goal in tissue engineering is to create functional materials, mimicking scaffolds in native tissues, to modulate cell function for tissue repair. Collagen is the most abundant structural protein in human body. Though collagen I (COLI) and collagen III (COLIII) are the predominant collagen types in connective tissues and they form stable hybrid fibrils at varied ratios, cell responses to the hybrid matrices are underinvestigated. In this work, we aim to explicate the distinctive roles of COLI and COLIII in fibroblast activation. Unidirectionally aligned COLI, COLIII and COLI-COLIII hybrid nanofibrils were generated via epitaxial growth of collagen on mica. AFM analyses revealed that, with the increase of COLI/COLIII ratio, the fibril width and stiffness increased and the binding affinity of cells to the matrix decreased. A hybrid matrix was found to activate fibroblasts the most effectively, characterized by extensive cell polarization with rigid stress fiber bundles and high α-SMA expression, and by the highest-level of collagen synthesis. It is ascribed to the fine balance between biochemical and biophysical cues achieved on the hybrid matrix. Thus, matrices of aligned COLI-COLIII hybrid fibrils and their derived multifunctional composites can be good candidates of implantation scaffolds for tissue regeneration.

Collagen Type III Alpha 1 chain regulated by GATA-Binding Protein 6 affects Type II IFN response and propanoate metabolism in the recurrence of lower grade glioma.

Some studies suggested the prognosis value of immune gene in lower grade glioma (LGG). Recurrence in LGG is a tough clinical problem for many LGG patients. Therefore, prognosis biomarker is required. Multivariate prognosis Cox model was constructed and then calculated the risk score. And differential expressed transcription factors (TFs) and differential expressed immune genes (DEIGs) were co-analysed. Besides, significant immune cells/pathways were identified by single sample gene set enrichment analysis (ssGSEA). Moreover, gene set variation analysis (GSVA) and univariate Cox regression were applied to filter prognostic signalling pathways. Additionally, significant DEIG and immune cells/pathways, and significant DEIG and pathways were co-analysed. Further, differential enriched pathways were identified by GSEA. In sum, a scientific hypothesis for recurrence LGG including TF, immune gene and immune cell/pathway was established. In our study, a total of 536 primary LGG samples, 2,498 immune genes and 318 TFs were acquired. Based on edgeR method, 2,164 DEGs, 2,498 DEIGs and 31 differentials expressed TFs were identified. A total of 106 DEIGs were integrated into multivariate prognostic model. Additionally, the AUC of the ROC curve was 0.860, and P value of Kaplan-Meier curve < 0.001. GATA6 (TF) and COL3A1 (DEIG) were selected (R = 0.900, P < 0.001, positive) as significant TF-immune gene links. Type II IFN response (P < 0.001) was the significant immune pathway. Propanoate metabolism (P < 0.001) was the significant KEGG pathway. We proposed that COL3A1 was positively regulated by GATA6, and by effecting type II IFN response and propanoate metabolism, COL3A1 involved in LGG recurrence.

A Novel Mouse Model for Cilia-Associated Cardiovascular Anomalies with a High Penetrance of Total Anomalous Pulmonary Venous Return.

Primary cilia are small organelles projecting from the cell surface of many cell types. They play a crucial role in the regulation of various signaling pathway. In this study, we investigated the importance of cilia for heart development by conditionally deleting intraflagellar transport protein Ift88 using the col3.6-cre mouse. Analysis of col3.6;Ift88 offspring showed a wide spectrum of cardiovascular defects including double outlet right ventricle and atrioventricular septal defects. In addition, we found that in the majority of specimens the pulmonary veins did not properly connect to the developing left atrium. The abnormal connections found resemble those seen in patients with total anomalous pulmonary venous return. Analysis of mutant hearts at early stages of development revealed abnormal development of the dorsal mesocardium, a second heart field-derived structure at the venous pole intrinsically related to the development of the pulmonary veins. Data presented support a crucial role for primary cilia in outflow tract development and atrioventricular septation and their significance for the formation of the second heart field-derived tissues at the venous pole including the dorsal mesocardium. Furthermore, the results of this study indicate that proper formation of the dorsal mesocardium is critically important for the development of the pulmonary veins. Anat Rec, 302:136-145, 2019. © 2018 Wiley Periodicals, Inc.

The role of an octacalcium phosphate in the re-formation of infraspinatus tendon insertion.

BACKGROUND: To improve the success rate of rotator cuff repair, we investigated whether octacalcium phosphate (OCP) with gelatin (Gel) vehicle had a positive effect on tendon-to-bone healing. METHODS: We assessed the histologic characteristics of the tendon-to-bone healing using the rabbit rotator cuff repair model. We divided the shoulders into 3 groups: control (without OCP/Gel composite), OCP/Gel composite (OCP+group), and Gel alone without OCP (Gel group) to evaluate the effectiveness of gelatin. RESULTS: Both the number of newly formed tendon fibers and the Sharpey fibers at the repair site increased in the OCP+group compared with those in the other 2 groups on hematoxylin-eosin staining (P < .05). On immunohistochemical evaluation, both the bone and the fibers in the OCP+group demonstrated that type I collagen was picked up, whereas the newly formed tendon fibers and Sharpey fibers revealed type III collagen. CONCLUSION: Treatment with OCP made collagen fibers and the Sharpey fibers, constituted by type I and type III collagens, increase at the tendon-to-bone insertion. It might be beneficial for the healing of rotator cuff tendon to bone.

Chondrogenic and fibrotic process in the ligamentum flavum of patients with lumbar spinal canal stenosis.

STUDY DESIGN: A histological, biological, and immunohisto-chemical study of human lumbar ligamentum flavum. OBJECTIVE: To analyze changes in the hypertrophied ligamentum flavum and clarify their etiology. SUMMARY OF BACKGROUND DATA: Hypertrophy of the ligamentum flavum has been considered a major contributor to the development of lumbar spinal canal stenosis (LSCS). Although previous studies have reported some factors related to ligamentum flavum hypertrophy, its etiology is still unclear. METHODS: Ligamentum flavum samples were collected from 20 patients with LSCS (LSCS group) and 10 patients with lumbar disc herniation (LDH group) as a control. The thickness of the ligamentum flavum was measured histologically. The amounts of elastic fibers and proteoglycans were assessed by Elastica-Masson staining and alcian blue staining, respectively. Gene and protein expressions related to fibrosis, inflammation, and chondrogenesis were analyzed by quantitative reverse transcription-polymerase chain reaction and immunohistochemistry. The total genes of the 2 groups were compared by DNA microarray analysis. RESULTS: The ligamentum flavum was significantly thicker in the LSCS group, which had a smaller amount of elastic fibers and a larger amount of proteoglycans. The gene expression related to fibrosis was significantly higher in the LSCS group; however, the immunoreactivities of collagen types I and III were weaker on the dorsal side of the ligamentum flavum in the LSCS group. The gene expression related to chondrogenesis and proteoglycan synthesis was significantly higher in the LSCS group. There was no significant difference in the gene expression related to inflammation between the 2 groups. CONCLUSION: Synthesis of the collagenous fibers and degradation of the elastic and collagenous fibers are both accelerated in the ligamentum flavum of patient with LSCS, which may be the reason for hypertrophy of the tissue. In addition, chondrogenesis and proteoglycan synthesis may have critical roles in the pathogenesis of the ligamentum flavum hypertrophy. LEVEL OF EVIDENCE: 5.

Identifying a novel role for X-prolyl aminopeptidase (Xpnpep) 2 in CrVI-induced adverse effects on germ cell nest breakdown and follicle development in rats.

Environmental exposure to endocrine-disrupting chemicals (EDCs) is one cause of premature ovarian failure (POF). Hexavalent chromium (CrVI) is a heavy metal EDC widely used in more than 50 industries, including chrome plating, welding, wood processing, and tanneries. Recent data from U.S. Environmental Protection Agency indicate increased levels of Cr in drinking water from several American cities, which potentially predispose residents to various health problems. Recently, we demonstrated that gestational exposure to CrVI caused POF in F1 offspring. The current study was performed to identify the molecular mechanism behind CrVI-induced POF. Pregnant rats were treated with 25 ppm of potassium dichromate from Gestational Day (GD) 9.5 to GD 14.5 through drinking water, and the fetuses were exposed to CrVI through transplacental transfer. Ovaries were removed from the fetuses or pups on Embryonic Day (ED) 15.5, ED 17.5, Postnatal Day (PND) 1, PND 4, or PND 25, and various analyses were performed. Results showed that gestational exposure to CrVI: 1) increased germ cell/oocyte apoptosis and advanced germ cell nest (GCN) breakdown; 2) increased X-prolyl aminopeptidase (Xpnpep) 2, a POF marker in humans, during GCN breakdown; 3) decreased Xpnpep2 during postnatal follicle development; and 4) increased colocalization of Xpnpep2 with Col3 and Col4. We also found that Xpnpep2 inversely regulated the expression of Col1, Col3, and Col4 in all the developmental stages studied. Thus, CrVI advanced GCN breakdown and increased follicle atresia in F1 female progeny by targeting Xpnpep2.

Monitoring the healing of combat wounds using Raman spectroscopic mapping.

Soldiers wounded in modern warfare present with extensive and complicated acute wounds, confounded by an overwhelming inflammatory response. The pathophysiology of acute wounds is unknown and timing of wound closure remains subjective. Collagen gene expression profiles are presented for 24 patients. Impaired healing wounds showed a twofold decrease in the up-regulation of COL1A1 and COL3A1 genes in the beginning of the wound healing process, compared with normal healing wounds. By the final debridement, however, collagen gene expression profiles for normal and impaired healing wounds were similar for COL1A1 and COL3A1. In addition, Raman spectroscopic maps were collected of biopsy tissue sections, from the first and last debridements of 10 wounds collected from nine patients. Tissue components obtained for the debridement biopsies were compared to elucidate whether or not a wound healed normally. Raman spectroscopy showed a loss of collagen in five patients, indicated by a negative percent difference in the 1,665/1,445 cm(-1) band area ratios. Four healed patients showed an increased or unchanged collagen content. Here, we demonstrate the potential of Raman spectroscopic analysis of wound biopsies for classification of wounds as normal or impaired healing. Raman spectroscopy has the potential to noninvasively monitor collagen deposition in the wound bed, during surgical wound debridements, to help determine the optimal time for wound closure.

[Thermal lasers and skin cicatrization]. / Lasers thermiques et cicatrisation cutanée.

Any cutaneous damage triggers a cascade of biological effects in the skin responsible for re-establishing skin integrity. Wound healing is a complex biological process inducing dermal remodelling leading at least to a visible scar, and sometimes to hypertrophic or keloid scars. Recent studies suggest that using a laser generates a precisely defined thermal effect in the skin, improving the wound healing process and potentially opening the door to scarless healing.

[Functional histology of dermis]. / Histologie fonctionnelle du derme.

The skin is composed of epidermis, dermis and subcutaneous tissue that interconnect anatomically. The dermis is an integrated system of fibrous and amorphous connective tissue that accommodates nerve and vascular networks, epidermally derived appendages, fibroblasts, macrophages and mast cells. Elastic and collagen tissue are the main types of fibrous connective tissue. The elastic connective tissue is assembled in a continuous network including mature elastic fibers, immature elaunin fibers and oxytalan fibers. Mature elastic fibers and elaunin have microfibrillar and amorphous matrix components while oxytalan fibers only contain microfibrils. Several molecules have been identified as constituents of the elastic fibers. Among the most characterized of these molecules is elastin in amorphous matrix, fibrillins 1 and 2 and LTBP-2 (ligand of latent TGFbeta) in microfibrils and fibulins which interconnect elastin and fibrillins. Elastic fibers provides elasticity to the skin. Under electron microscope, collagen fibers appears as of bundles of periodically banded fibrils which are composed of collagens types I, III and V; type V collagen is believed to assist in regulating fibril diameter. They are associated with FACITs (fibril-associated collagen with interrupted triple helixes) collagens types XIV et XVI. Collagen fibers provide tensile strength to the skin. Non fibrous connective tissue molecules include finely filamentous glycoproteins, glycosaminoglycans and proteoglycans of "the ground substance" (hyaluronic acid and chondroitin sulphate, dermatan sulphate, versican, decorin). Fibroblasts, macrophages and mast cells are regular residents of the dermis. The main function of these cells are well known. Fibroblasts are responsible for the synthesis and the degradation of fibrous and non fibrous connective tissue matrix proteins. Macrophages are phagocytic; they process and present antigen to immunocompetent lymphoid cells. Mast cells are responsible for IgE mediated acute, subacute and chronic inflammation. All these cells have a long list of other functions, in particular they are involved in coagulation, wound healing and tissue remodeling.

Visualization of cartilage formation: insight into cellular properties of skeletal progenitors and chondrodysplasia syndromes.

The cellular events underlying skeletal morphogenesis and the formation of cartilage templates are largely unknown. We generated an imaging system to dynamically visualize limb mesenchymal cells undergoing successive phases in cartilage formation and to delineate the cellular function of key regulators of chondrogenesis found mutated in chondrodysplasia syndromes. We uncovered an unsuspected role for Sox9 in control of cell morphology, independent from its major downstream target ColIIa, critically required for the mesenchyme-to-chondrocyte transition. In contrast, Bmp signaling regulates a cellular program we term "compaction" in which mesenchymal cells acquire a cohesive cell behavior required to delineate the boundaries and size of cartilage elements. Moreover, we visualized labeled progenitor cells from different regions of the limb bud and identified unique cellular properties that may direct their contribution toward specific skeletal elements such as the humerus or digits. These findings shed light on the cellular basis for chondrodysplasia syndromes and formation of the vertebrate skeleton.

Upregulation of heme oxygenase and collagen type III in the rat bladder after partial bladder outlet obstruction.

The objective of the study was to evaluate possible changes of the gene expression and localization of the enzymes, heme oxygenase and nitric oxide synthase (NOS), with reference to increase of collagen type III in response to the partial obstruction of the bladder. Following initial obstruction, whole rat bladders were removed for real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. Real-time RT-PCR demonstrated significantly enhanced expression of HO (p < 0.01) and collagen type III (p < 0.001) gene on postoperative day 14. Enhanced expression of NOS gene was seen only on postoperative day 4 (p < 0.01). Immunohistochemistry revealed that immunoreactivity to HO-1 had much in common in neural cells and fibers, although immunoreactivity to HO-2 and iNOS was relatively weak. This study suggested gene expression of HO, especially HO-1, was more dramatically changed than NOS, and was upregulated simultaneously with increase of collagen type III after obstruction. HO systems could be involved in the pathogenesis of bladder dysfunction related to increase of collagen type III after obstruction.

Multifactor complex containing B element binding factor, BBF, and repressors regulate the human alpha 1(III) collagen gene (COL3A1).

Type III collagen is found in fetal skin and blood vessels. Previously, we characterized the proximal promoter of the human alpha1(III) collagen gene (COL3A1) using the human rhabdomyosarcoma cell line, A204, and NIH3T3 cells (Yoshino et al., Biochim Biophys Acta, 2005). In the present study, we further analyzed this promoter using additional cell lines, namely a human embryonal rhabdomyosarcoma cell line (RD) and bovine vascular smooth muscle cells (vSMCs), both of which show high expression of type III collagen. Using a luciferase assay, electrophoretic mobility shift assays (EMSA), and DNase footprinting assay, 2 types of multifactor complexes were shown to bind to the DNA region in the vicinity of the B element (- 80 to - 58), depending on the cell type. Next, we used cells stably transfected with a GFP-linked type III collagen promoter fragment for analysis of promoter expression. Usually, transfected cells retained the characteristics of the original cells. However, in several clones derived from RD cells, promoter expression as well as cell shape changed to patterns characteristic of the A204 cell line. Nuclear factors expressed by these clones were also characteristic of the A204 line.

Splenic vasculopathy in portal hypertension patients.

AIM: To investigate the interaction between portal hypertension, splanchnic hyperdynamic circulation and splanchnic vasculopathy by observing splenic arterial and venous pathological changes and the ro1e of extra-cellular matrix in the pathogenesis of portal hypertensive vasculopathy by measuring the expression of type I and type III procollagen mRNA in splenic venous walls of portal hypertensive patients. METHODS: Morphological changes of splenic arteries and veins taken from portal hypertensive patients (n=20) and normal controls (n=10) were observed under optical and electron microscope. Total RNA was extracted and the expression of type I and type III procollagen mRNA in splenic venous walls of portal hypertensive patients (n=20) was semi-quantitatively detected using reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Under optical microscope, splenic arterial intima was destroyed and internal elastic membrane and medial elastic fibers of the splenic arterial walls were degenerated and broken. Splenic venous intima became remarkably thick. Endothelia1 cells were not intact with formation of mural thrombus. The tunica media became thickened significantly due to hypertrophy of smooth muscles. Fibers and connective tissues were increased obviously. Under electron microscope, smooth muscle cells of the splenic arteries were degenerated and necrotized. Phenotypes of smooth muscle cells changed from constrictive into synthetic type. Red blood cells and platelets accumulated around the damaged endothelial cells. Synthetic smooth muscle cells were predominant in splenic veins and their cytoplasma had plentiful rough endoplasmic reticulum ribosomes and Golgi bodies. Along the vascular wall, a lot of collagen fibers were deposited, the intima was damaged and blood components accumulated. There was no significant difference in the expression of type I procollagen mRNA in splenic venous wall between the patients with portal hypertension and those without portal hypertension (P>0.05), but the expression of type III procoagen mRNA was significantly stronger in the patients with portal hypertension than in those without portal hypertension (P<0.01). CONCLUSION: Type III procollagen and collagen might be important extra-cellular matrix resulting in neointimal formation and vascular remodeling in the pathogenesis of portal hypertensive vasculopathy. The pathological changes in splenic arteries and veins exist in portal hypertension patients. There might be an interaction between portal hypertension, splanchnic hyperdynamic circulation and splanchnic vasculopathy.

Identification and characterization of endogenous Langerin ligands in murine extracellular matrix.

Langerin is a C-type lectin that is expressed by Langerhans cells (LC) and related immune cells, and believed to play an important role in antigen recognition and uptake. To determine if Langerin has endogenous ligands, we generated S protein binding, bacterial recombinant, mouse soluble Langerin, and utilized it as a probe. Recombinant soluble Langerin did not bind to lymph node or spleen cells, or keratinocytes as assessed via flow cytometry. However, Langerin did bind to surfaces of primary skin fibroblasts and NIH3T3 cells. "Ligand blotting" of fibroblast membrane-enriched fractions with Langerin revealed reproducible binding to 140 and 240 kDa proteins resolved in reduced denaturing gels. Characterization of these proteins using mass spectrometry suggested types I and III procollagen and fibronectin as candidate ligands. Langerin bound to type I procollagen that was immunoprecipitated from fibroblast lysates, but did not bind to fibronectin that was immunoprecipitated from fibroblast-conditioned media or mouse plasma fibronectin. These results indicate that Langerin selectively interacts with at least one ligand in extracellular matrix (type I procollagen). Langerin may have an unanticipated role in cell-matrix interactions that modulate LC development, localization, or function.

Functional changes in bladder tissue from type III collagen-deficient mice.

OBJECTIVE: Collagen fibers impart tensile strength and transfer tension from bladder smooth muscle cells. We have previously shown that fibrotic bladders are characterized by an increased type III:type I collagen ratio. To determine the effect of decreased type III collagen on bladder function, type III collagen-deficient mice (COL3A1) were studied physiologically. METHODS: Bladders from wild-type (+/+) and heterozygous (+/-) COL3A1 mice were biochemically characterized to determine total collagen (hydroxyproline analysis) and collagen subtype concentration (cyanogen bromide digestion and ELISA). Alterations in collagen fiber diameter were assessed by electron microscopy. Bladder muscle strips were used to assess physiologic function. RESULTS: Hydroxyproline content decreased in heterozygous bladders, which had 50% less type III collagen. Wild-type bladders had a biphasic distribution of collagen fiber sizes, whereas heterozygous bladder collagen fibers spanned a broad range. Physiologically, there were no differences in contractile responses between wild-type and heterozygotes when stimulated with ATP, carbachol or KCl, indicating normal contraction via purinergic and muscarinic receptors, and in response to direct membrane depolarization. In contrast, tension generation in heterozygotes was decreased after field stimulation (FS), indicating decreased synaptic transmission. Length-tension studies showed that the heterozygote muscle strips generated less tension per unit length, indicating that they were more compliant than wild-type controls. CONCLUSIONS: Critical levels of type III collagen appear to be a requirement for normal bladder tension development and contraction. Our data show that a decrease in the type III:type I collagen ratio, and altered fiber size, results in a more compliant bladder with altered neurotransmitter function.

Type VI collagen induces cardiac myofibroblast differentiation: implications for postinfarction remodeling.

Cardiac fibroblast (CF) proliferation and differentiation into hypersecretory myofibroblasts can lead to excessive extracellular matrix (ECM) production and cardiac fibrosis. In turn, the ECM produced can potentially activate CFs via distinct feedback mechanisms. To assess how specific ECM components influence CF activation, isolated CFs were plated on specific collagen substrates (type I, III, and VI collagens) before functional assays were carried out. The type VI collagen substrate potently induced myofibroblast differentiation but had little effect on CF proliferation. Conversely, the type I and III collagen substrates did not affect differentiation but caused significant induction of proliferation (type I, 240.7 +/- 10.3%, and type III, 271.7 +/- 21.8% of basal). Type I collagen activated ERK1/2, whereas type III collagen did not. Treatment of CFs with angiotensin II, a potent mitogen of CFs, enhanced the growth observed on types I and III collagen but not on the type VI collagen substrate. Using an in vivo model of myocardial infarction (MI), we measured changes in type VI collagen expression and myofibroblast differentiation after post-MI remodeling. Concurrent elevations in type VI collagen and myofibroblast content were evident in the infarcted myocardium 20-wk post-MI. Overall, types I and III collagen stimulate CF proliferation, whereas type VI collagen plays a potentially novel role in cardiac remodeling through facilitation of myofibroblast differentiation.

Three-dimensional distribution of the collagen fibers in the submucosa of the swine terminal ileum.

Collagen has an important role in controlling mechanical function and physiopathology of intestinal wall. Swine small intestine may be used as biomaterial source for tissue repairing. Changes of collagen arrangement and three-dimensional (3D) distribution may be related to the dissimilar biomechanical proprieties showed by different intestine tracts. 3D spatial distribution of collagen bundles of swine submucosal terminal ileum (SSTI) was studied by a correlated analysis of light (LM) and scanning electron microscopy (SEM) of NaOH macerated samples. Bundles of collagen fibers were greatly represented in the submucosa at the mesenteric border and also extended along the longitudinal folds beneath mucosa layer. Polarized LM of picrosirius stained samples evidenced yellow and red fibers (type I collagen), and green fibers (type III collagen). Silver-impregnated sections showed predominant brown-stained fibers and, in a smaller amount, black-stained ones. By SEM submucosal collagen, isolated by NaOH maceration, appeared arranged in wide bundles forming a complicated 3-D network. The bundles presented a sinuous course, opened and closed repeatedly forming meshes fashioned in a regular net. These observations originally demonstrated that 3-D distribution of SSTI collagen is different from that observed in other gut segments and species. The arrangement of SSTI collagen fibers that we observed seems to be morphofunctionally adjusted to provide appropriate resistance to mechanical forces and to assure compliance to deformations induced by intestinal wall motion. The studies for selection of optimal intestinal patches for surgical replacement should take into consideration the basic morphological evaluation of parietal collagen 3D distribution.

Binding of proteins to the PDZ domain regulates proteolytic activity of HtrA1 serine protease.

HtrA1, a member of the mammalian HtrA (high temperature requirement A) serine protease family, has a highly conserved protease domain followed by a PDZ domain. Accumulating evidence has indicated that PDZ domains regulate protease activity of HtrA proteins. We searched for binding partners of the PDZ domain of mouse HtrA1 by yeast two-hybrid screening, and isolated proteins that were recognized by the HtrA1 PDZ domain through their C-terminal ends with a core consensus Phi-X-Phi-[V/L/F/A]-COOH sequence (where Phi is a hydrophobic/non-polar amino acid). C-propeptides of fibrillar collagens were most frequently isolated. Type III procollagen alpha1 C-propeptide, which was used as a model protein, was digested by HtrA1. HtrA1 cleavage of the collagen C-propeptide was enhanced by reductive denaturation of the C-propeptide and partly inhibited by removal of the C-terminal four amino acids from the C-propeptide, suggesting that the substrate recognition was facilitated by the binding of the free C-terminal ends of substrates to the PDZ domain of HtrA1. The synthetic oligopeptide (GM130Pep) that fitted the consensus recognition sequence bound to HtrA1 with a high affinity (K(d)=6.0 nM). GM130Pep stimulated HtrA1 protease activity 3- to 4-fold, but did not efficiently stimulate the activity of an HtrA1 mutant lacking the PDZ domain, supporting the notion that the PDZ domain enhances protease activity upon ligand binding. The peptide derived from Type III collagen alpha1 C-propeptide specifically stimulated protease activity of HtrA1, but did not stimulate nor significantly bind to HtrA2, suggesting that the collagen C-propeptide is a specific physiological regulator of HtrA1.

Is the tendon embryogenesis process resurrected during tendon healing?

The process of embryonic tendon development, including the nature and purpose of collagen fibril segments, is reviewed. It is proposed that tendon fibrillogenesis of repair is related to the fibrillogenesis of tendon embryonic development. The assembly of collagen fibril segment units into longer fibers occurs on the surface of tendon fibroblasts in embryonic tendon development. The biochemist's view of tendon healing, whereby the spontaneous polymerization of tropocollagen monomers regenerates lost tendon collagen fibers, needs to be reconsidered. Furthermore, the importance of direct fibroblast involvement in collagen fiber reassembly during tendon healing needs to be studied in tendon intrinsic regenerative repair.

Comparison of collagen fibre architecture between slow-twitch cranial and fast-twitch caudal parts of broiler M. latissimus dorsi.

1. Collagen fibre architectures of perimysium and endomysium in the slow-twitch cranial and fast-twitch caudal parts of broiler M. latissimus dorsi were compared. 2. Type I and III collagens were distributed in both perimysium and endomysium as indicated by their positive immunohistochemical reactions to polyclonal antibodies. 3. Cells invested by endomysium with no myofibres were larger in the cranial part because of the presence of larger slow-twitch myofibres. The honeycomb structure of endomysium was divided into several parts by thick perimysium. 4. The thick perimysial collagen fibres with parallel fibrils, which were interconnected by the loose reticular fibrils and thin fibres, were more numerous and thicker in the cranial part than the caudal. 5. Thick endomysial sidewall of cells in the cranial part was composed of a rougher reticulum of slightly thicker collagen fibrils compared with the thin sidewall in the caudal part. 6. These results indicated that both perimysial constitutions of collagen fibres and endomysial collagen fibrils had attained much larger growth in the slow-twitch cranial part than the fast-twitch caudal in broiler latissimus dorsi muscle.