A combination of scanning and transmission electron microscopy was used to investigate the morphology and ultrastructure of normal human articular cartilage sampled from adult amputation specimens. This study confirms our previous observations on canine articular cartilage, which showed middle and deep layer chondrocytes surrounded by a pericellular matrix and enclosed within a pericellular capsule composed of filamentous and fine fibrillar materials. Pores in the "felt-like" organization of the capsular weave progressively decreased in size from the inner to the outer border of the capsule. Matrix vesicles were found embedded within the capsular weave and distributed throughout the territorial matrix. It is suggested that the chondrocyte, its pericellular matrix, and capsule together constitute the "chondron," a primary functional and metabolic unit of cartilage that acts hydrodynamically to protect the integrity of the chondrocyte and its pericellular microenvironment during compressive loading.

More than 300 primary cilia have been identified electronmicroscopically in a variety of embryonic and mature connective tissue cells. To further define the enigmatic function of these cilia, we examined the interrelationships between the basal apparatus and cytoplasmic organelles and the ciliary shaft and the extracellular matrix. The basal diplosome was consistently associated with the secretory organelles including the maturing face of the Golgi complex, Golgi vacuoles and vesicles, the microtubular network, the plasma membrane, and coated pits and vesicles. Small vesicles and amorphous granules were also observed within the ciliary lumen and adjacent to the ciliary membrane. Microtubule-membrane bridges linked axonemal tubules to the ciliary membrane. The position, projection, and orientation of the axoneme were influenced by the structural organisation and mechanical properties of the matrix and frequently caused angulation of the ciliary shaft relative to the basal body. Located midway between the secretory apparatus and the extracellular matrix, primary cilia would appear ideally situated to mediate the necessary interaction between the cell and its surrounding environment prerequisite to the formation and maintenance of a functionally effective matrix. We propose that primary cilia in connective tissue cells could act as multifunctional, cellular cybernetic probes, receiving, transducing, and conducting a variety of extrinsic stimuli to the intracellular organelles responsible for effecting the appropriate homeostatic feedback response to changes in the extracellular micro-environment.

Small airways are the major site of airflow obstruction in chronic obstructive pulmonary disease (COPD). This is attributed to loss of elastin in alveoli and fibrosis in small airways. In the present study, it was hypothesised that changes to elastic fibres in alveoli might be paralleled by a similar reduction in elastic fibres in small airways.Tissue blocks from patients who had lobectomy for bronchial carcinoma were studied. Patients were classified as COPD (forced expiratory volume in one second (FEV1) ,80% predicted, FEV1/ forced vital capacity (FVC) ,0.7) or controls (FEV1 o80% pred, FEV1/FVC o0.7). Elastic fibres were visualised using Elastic van Gieson staining and the volume fraction (v/f) of elastic fibres was determined as a percentage of tissue volume using point counting. Elastic fibre networks were also visualised by confocal microscopy.The v/f for elastic fibres in alveoli was 18.6% for COPD and 32.8% in controls. In the airways the v/f was 14.6% for COPD and 25.5% in controls. FEV1% predicted was correlated with v/f in both alveoli and small airways.The volume fraction of elastic fibres was reduced to a similar extent in small airways and alveoli in chronic obstructive pulmonary disease and both were correlated with the extent of airflow obstruction. Loss of elastic fibres in small airways may contribute to the development of airflow obstruction in chronic obstructive pulmonary disease.

Background: COPD is characterised by loss of alveolar elastic fibers and by lack of effective repair. Elastic fibers are assembled at cell surfaces by elastin binding protein (EBP), a molecular chaperone whose function can be reversibility inhibited by chondroitin sulphate of matrix proteoglycans such as versican. This study aimed to determine if alveoli of patients with mild to moderate COPD contained increased amounts of versican and a corresponding decrease in EBP, and if these changes were correlated with decreases in elastin and FEV 1 .

Abstract-The proteoglycan versican is implicated in several atherogenic events, including stimulation of vascular smooth muscle cell (VSMC) growth and migration, retention of lipoproteins, and promotion of thrombogenesis. A high content of intimal versican also correlates with a low content of elastin, suggesting an inhibitory role for versican in elastogenesis. To determine whether reduced production of versican can be used to enhance elastogenesis, we transduced Fischer rat VSMC (FRSMC) with a versican antisense sequence using the retroviral vector LXSN. Stable expression of versican antisense (LVaSN) significantly reduced versican production, induced a flattened morphology, reduced cell proliferation and migration, increased tropoelastin synthesis, increased elastin binding protein (S-Gal/EBP), and increased deposition of elastic fibers in long-term cultures. Add-back of chondroitin sulfate chains, or versican, decreased S-Gal/EBP and elastic fiber formation. LVaSN cells seeded into balloon catheter-injured rat carotid arteries formed neointimae containing low levels versican, increased amounts of S-Gal/EBP, and increased elastin deposits 7 days postinjury. At 4 weeks, neointimae formed from LVaSN cells were highly structured and contained multiple layers of elastic fibers and lamellae.

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Objective Extracellular matrix (ECM) of neointima formed following angioplasty contains elevated levels of versican, loosely arranged collagen, and fragmented deposits of elastin, features associated with lipid and macrophage accumulation. ECM with a low versican content, compact structure and increased elastic fiber content can be achieved by expression of versican variant V3, which lacks chondroitin sufate (CS) glycosaminoglycans (GAG). We hypothesized that V3-expressing arterial smooth muscle cells (ASMC) can be utilized to form a neointima resistant to lipid and macrophage accumulation associated with hypercholesterolemia. Methods and Results ASMC transduced with V3 cDNA were seeded into ballooned rabbit carotid arteries and animals fed a chow diet for four weeks, followed by a cholesterol-enriched diet for four weeks, achieving plasma cholesterol levels of 20–25mmol/L. V3 neointimae at eight weeks were compact, multilayered and elastin-enriched. They were significantly thinner (57%) than control neointimae, contained significantly more elastin (118%), less collagen (22%) and less lipid (76%), and showed significantly reduced macrophage infiltration (85%). Mechanistic studies demonstrated that oxidized LDL stimulated the formation of this monocyte binding ECM which was inhibited in the presence of V3 expressing ASMC. Conclusion These results demonstrate that expression of V3 in vessel wall creates an elastin-rich neointimal matrix that in the presence of hyperlipidemia is resistant to lipid deposition and macrophage accumulation.

The mature chick sternum is divisible almost equally into cephalic calcified and caudal cartilagenous regions . Isolation and culture of cells derived from embryonic precursors of these regions has revealed two discrete populations of cells with distinct morphological features and synthetic capabilities . Both cell populations grew well in culture within or upon collagen gels or upon plastic and maintained morphologies similar to those observed in the parent tissue. Polyacrylamide gel electrophoresis of radiolabeled proteins synthesized by the cells in culture demonstrated large differences in the types of collagens synthesized . Both chondrocyte populations synthesized type II and minor cartilage collagens but only chondrocytes isolated from the presumptive calcification region synthesized the previously identified, low molecular weight collagen, termed G Collagen. Synthesis of G collagen was stimulated by culture within or upon Collagen gels such that it represented an average of 65% of the total collagen synthesized by presumptive calcification region chondrocytes after 7 d of culture within collagen gels. Light and scanning electron microscopy demonstrated that the two chondrocyte types exhibited distinct morphological features and accumulated different extracellular matrices in culture .Type 11 collagen has been recognized as the major collagenous component ofcartilagenous tissues for a number ofyears (19). However, several additional, apparently cartilage specific, collagenous molecules have recently been isolated. These include the 3a, 2a, 1 a chains described by Burgeson and Hollister (5) and a group of possibly related, low molecular weight, collagenous peptides obtained by pepsin digestion ofcartilagenous tissues (1,22,23,25,31,32,34). We have also reported the identification and partial characterization of three further collagenous polypeptides, the G, H, and J chains, synthesized by chondrocytes in culture (11,12) . The H and J chains occur as disulphide-linked aggregates which give rise to chains of 69,000 and 84,000 mol wt, respectively, upon reduction . The major product of mild chymotrypsin digestion of these collagens is a 53,000-mol-wt peptide which exhibits characteristics similar to some of the previously mentioned collagenous peptides that have been isolated from cartilage by pepsin digestion . G collagen has a number of characteristics that distinguish it from other cartilage collagens. The component chains have a molecular weight of59,000 which is reduced to 45,000 by chymotrypsin digestion of the native molecule. It is cleaved to discrete products by mammalian collagenase digestion and digestion with cyanogen bromide, chymotrypsin, or V8 protease, which give rise to distinct peptide fingerprints . The synthesis of G collagen was markedly stimulated by the culture of chondrocytes within collagen gels.It has long been recognized that two major types of cartilage and chondrocytes are found in the embryonic chick; hypertrophic cartilage, which contains large cells and is always assoc...