Biomedical subjects

C W Archer

Publications and source records attributed to C W Archer.

At least 19 recordsLinked to original sources

PubMed2006

Mechanically loaded ex vivo bone culture system 'Zetos': systems and culture preparation.

This paper introduces the culture preparation of ovine, bovine and human cancellous bone cores to be used in an explants model Zetos. The three dimensional (3D) bone cores were prepared and evaluated for all three animals. Bone cells in vivo constantly interact with each other, migratory cells, surrounding extracellular matrix (ECM) and interstitial fluid in a microenvironment, which continuously responds to various endogenous and exogenous stimuli. The Zetos system was designed to culture and mechanically load viable cancellous bone explants in their near natural microenvironment. This 3D ex vivo system bridges the current gap between in vitro and in vivo methods. One aim of this work was to compare the macro and micro-architecture of ovine, bovine and human cancellous bone tissue in preparation for culture within the Zetos system in order to determine the optimal source of experimental material. A second aim was to optimise the preparations of the bone cores as well as develop techniques involved during tissue maintenance. Bone core response was visualised using histological and immunohistochemical methods. The results demonstrate that cancellous bone explants vary greatly in trabecular density and bone volume depending on species, age and location. Sheep and human samples displayed the greatest variation between bones cores when compared to bovine. Even cores taken from the same animal possessed very different characteristics. The histology demonstrated normal bone and cell structure after the core preparation. Immunohistochemistry results demonstrated antigen retention after preparation methods.

Aged↗

PubMed2006

Differential regulation of GDF-5 and FGF-2/4 by immobilisation in ovo exposes distinct roles in joint formation.

Members of the fibroblast growth factor (FGF) family and growth and differentiation factor 5 (GDF-5) have been implicated in joint specification, but their roles in subsequent cavity formation are not defined. Cavity formation (cavitation) depends upon limb movement in embryonic chicks and factors involved in joint formation are often identified by their expression at the joint-line. We have sought support for the roles of FGF-2, FGF-4, and GDF-5 in cavitation by defining expression patterns, immunohistochemically, during joint formation and establishing whether these are modified by in ovo immobilisation. We found that FGF-2 exhibited low level nuclear expression in chondrocytes and fibrocartilage cells close to presumptive joints, but showed significantly higher expression levels in cells at, and directly bordering, the forming joint cavity. This high-level joint line FGF-2 expression was selectively diminished in immobilised limbs. In contrast, we show that FGF-4 does not exhibit differential joint-line expression and was unaffected by immobilisation. GDF-5 protein also failed to show joint-line selective labelling, and although immobilisation induced a cartilaginous fusion across presumptive joints, it did not affect cellular GDF-5 expression patterns. Examining changes in GDF-5 expression in response to a direct mechanical strain stimulus in primary embryonic chick articular surface (AS) cells in vitro discloses only small mechanically-induced reductions in GDF-5 expression, suggesting that GDF-5 does not exert a direct positive contribution to the mechano-dependent joint cavitation process. This notion was supported by retroviral overexpression of UDPGD, a characteristic factor involved in hyaluronan (HA) accumulation at presumptive joint lines, which was also found to produce small decreases in AS cell GDF-5 expression. These findings support a direct mechano-dependent role for FGF-2, but not FGF-4, in the cavitation process and indicate that GDF-5 is likely to influence chondrogenesis positively without contributing directly to joint cavity formation.

Animals↗

PubMed2005

The ultrastructure of mouse articular cartilage: collagen orientation and implications for tissue functionality. A polarised light and scanning electron microscope study and review.

Adult mouse articular cartilage (AC) has not been thoroughly described using high resolution imaging techniques, despite the fact that the availability of knockout mice with specific extracellular matrix (ECM) mutations have renewed interest in using the mouse as a model for a variety of different human conditions. With osteoarthritis affecting millions of people worldwide, investigations into the structure and, therefore, the ability of AC to act as a load-bearing tissue, are crucial for developing treatments and prevention techniques to limit the degree of severity in this condition. Cryofixation and formaldehyde fixation as well as chemical digestion of the uncalcified regions of AC were used in combination with bright field light, polarised light and scanning electron microscopy to image the structure of adult mouse AC. Chemical digestion of the tissue revealed unique insights into the structure of mouse AC and the high cellular density of the tissue. Tightly packed sheets of collagen fibrils formed the territorial matrix (TM) of the deep zone. These were observed closely surrounding the chondrons, after applying both chemical and cryofixation techniques. The interterritorial matrix (IM), in contrast, was more isotropically arranged. The results of the study have implications for the interpretation of biomechanical functionality of mouse AC with probable applications to other species.

Animals↗

PubMed2005

Current strategies for articular cartilage repair.

Defects of articular cartilage that do not penetrate to the subchondral bone fail to heal spontaneously. Defects that penetrate to the subchondral bone elicit an intrinsic repair response that yields a fibrocartilaginous repair tissue which is a poor substitute for hyaline articular cartilage. Many arthroscopic repair strategies employed utilise this intrinsic repair response to induce the formation of a repair tissue within the defect. The goal, however, is to produce a repair tissue that has the same functional and mechanical properties of hyaline articular cartilage. To this end, autologous osteochondral transfer can provide symptomatic relief. This technique involves the excision of healthy cartilage plugs from 'non-load bearing' regions of the joint for implantation into the defect. Cell based transplantation methods currently involve the transplantation of expanded autologous chondrocytes to the defects to form a repair tissue. This technique again involves the excision of healthy cartilage from the joint for expansion. Current research is exploring the potential use of mesenchymal stem cells as a source for tissue engineering, as well as the combination of cells with biodegradable scaffolds. Although current repair strategies improve joint function, further research is required to prevent future degeneration of repair tissue.

Animals↗

PubMed2004

Cell-cell contact and membrane spreading in an ultrasound trap.

An ultrasonic standing wave trap [Langmuir 19 (2003) 3635] in which the morphologies of 2-D latex-microparticle aggregates, forming a pressure node plane, were characterised has been applied here to different cell suspensions with increasing order of specificity of cross-linking molecule, i.e. polylysine with chondrocytes; wheat germ agglutinin (WGA) with erythrocytes and surface receptors on neural cells. The outcome of initial cell-cell contact, i.e. whether the cells stuck at the point of contact (collision efficiency = 1) or rolled around each other (collision efficiency = 0), was monitored in situ by video-microscopy. The perimeter fractal dimensions (FD) of 2-D hexagonally symmetric, closely packed aggregates of control erythrocytes and chondrocytes were 1.16 and 1.18, respectively while those for the dendrititc aggregates formed initially by erythrocytes in 0.5microg/ml WGA and chondrocytes in 20 microg/ml polylysine were 1.49 and 1.66. The FDs for control and molecularly cross-linked cells were typical of reaction-limited aggregation (RLA) and transport diffusion-limited aggregation (DLA), respectively. The FDs of the aggregates of cross-linked cells decreased with time to give more closely packed aggregates without clear hexagonal symmetry. Suspensions of neural cells formed dendritic aggregates. Spreading of inter-cellular membrane contact area occurred over 15 min for both erythrocyte and neural cell dendritic aggregates. The potential of the technique to characterise and control the progression of cell adhesion in suspension away from solid substrata is discussed.

Animals↗

PubMed2004

The cellular responses of articular cartilage to sharp and blunt trauma.

OBJECTIVE: To determine the response of immature articular cartilage to both sharp and blunt trauma in terms of cell death, cell proliferation and matrix synthesis. DESIGN: Blunt wounds were made with a trephine in full depth immature bovine articular cartilage explants which were cut in half through the center of the trephine wound with a sharp scalpel to produce blunt and sharp trauma on the same explant. Explants were maintained in culture for up to 10 days. Prior to fixation at days 2, 5 and 10, medium was supplemented with 10 microCi ml-1 35S-sulphate, [3H]-proline or [3H]-thymidine for 24h to assess matrix synthesis and cell proliferation. Cell death was assessed using a Live/Dead label. RESULTS: In the case of blunt wounds, a band of cell death was observed adjacent to the lesion edge. Microautoradiography demonstrated little radiolabel incorporation and, therefore, no new matrix synthesis or cell proliferation within this region. In contrast, wounds made with a sharp scalpel showed restricted cell death, with radiolabel incorporation adjacent to the lesion edge at all time points. This demonstrated not only chondrocyte proliferation and new matrix synthesis at the wound margin, but also an up-regulation of matrix synthesis adjacent to the lesion edge. CONCLUSIONS: In terms of clinical relevance, the use of sharp precise instruments during the surgical management of cartilage defects may be necessary to reduce cell death and promote matrix elaboration at the lesion edge in order to facilitate successful integration.

Animals↗

PubMed2003

Immunohistochemistry of matrix markers in Technovit 9100 New-embedded undecalcified bone sections.

Trabecular bone is routinely analysed by histomorphological-histometrical and immunohistochemical techniques as means of assessing the differentiation status of bone deposition and growth. Currently few embedding resins exist for which both morphological and immunohistochemical analyses can be performed on mineralised tissue. Paraffin, the standard embedding medium for bone enzyme and immunohistochemistry, can only be used on demineralised tissue, but then trabecular structure may be badly preserved. Methyl methacrylate (MMA), the resin of choice for undecalcified bone histology can only be used for bone immunohistochemistry if the usual, highly exothermic polymerisation procedure is avoided which destroys tissue antigenicity. Consequently, most current practices involve cutting samples in half to be processed in separate resins when more than one type of analysis is required. Technovit 9100 New is a low temperature MMA embedding system that is purported to significantly improve tissue antigenicity preservation allowing polymerisation at -20 degrees C. In this study, Technovit 9100 New-embedded undecalcified trabecular bone samples (adult human, young bovine and ovine) yielded immunolabelling with several bone matrix markers and preserved morphological features in 7 microm sections when stained with Masson-Goldner, von Kossa, or toluidine blue. Bone samples from all resins used were immunolabelled with antibodies against osteocalcin, alkaline phosphatase, osteopontin, osteonectin, bone sialoprotein and procollagen type I amino-terminal propeptide. Technovit-embedded bone yielded more reliable immunolabelling of the matrix proteins when compared with heat or cold-cured LR White or standard embedded MMA samples. Technovit 9100 New provided better routine histology than LR White, and was comparable to MMA. Results demonstrated that Technovit 9100 New can be used as a low-temperature acrylic resin embedding method for routine undecalcified bone histology, as well as for immunohistochemistry.

Acrylic Resins↗

PubMed2003

A mechanism underlying the movement requirement for synovial joint cavitation.

Many studies have highlighted the importance of movement-induced mechanical stimuli in the development of functional synovial joints. However, such phenomenological results have failed to provide a full explanation of the mechanism essential for the morphogenesis of fluid-filled joint cavities. We have previously demonstrated that the large glycosaminoglycan hyaluronan (HA), in association with its principal cell surface receptor CD44, plays a major role during the morphogenesis of chick joints. We have taken cells from the surface of recently cavitated joints and subjected them to a brief period of dynamic mechanical strain (3800 microE for 10 min) and measured changes in HA synthesis/release, CD44 expression and HA synthase gene expression. In addition, we subjected cells to matrix depletion prior to the application of mechanical strain in order to examine any potential modulatory function of the ECM during the cell response to strain. Removal of the cell-associated HA-containing matrix with hyaluronidase significantly increased the release of HA into tissue culture media over 24 h and is associated with increased CD44 expression, alterations in HA synthase gene expression and enhanced binding of HA to the cell surface. Such changes in HA release were shown to be blocked by addition of exogenous HA and synergistically enhanced by the application of dynamic mechanical strain. These results show that cell-matrix interactions modify the response of embryonic cells to mechanical strain and provide further insight into the mechano-dependent mechanism of joint cavity morphogenesis.

Animals↗

PubMed2003

The distribution of Notch receptors and their ligands during articular cartilage development.

We examined the distribution of Notch family members and their ligands during the development of articular cartilage and the growth plate. Notch 1 was expressed by the chondrocytes of the developing articular surface but became increasingly restricted to the deeper layers after birth whilst expression of this family member was restricted to hypertrophic chondrocytes in the growth plate. Notch 2 and 4, Delta and Jagged 2 showed a broadly similar distribution, being present throughout the articular cartilage during development and becoming increasingly restricted to deeper layers with age. Hypertrophic chondrocytes within the growth plate also expressed Notch 2 and 4, Delta and Jagged 2 (which was also expressed in prehypertrophs). Notch 3 and Jagged 1 were absent from developing articular cartilage but were present in deeper layers at later time points (> 1 month) and both receptor and ligand were expressed in hypertrophic chondrocytes at all ages examined. These results highlight the complex Notch signalling interactions that result in the formation of the heterogeneous articular cartilage and allow for the co-ordinated ossification and elongation of the growth plate. Mechanisms by which these processes are controlled are discussed in light of recent advances in the understanding of Notch signalling pathways.

Animals↗

PubMed2001

Expression of clusterin in the superficial zone of bovine articular cartilage.

OBJECTIVE: To investigate the differences between chondrocytes of the superficial and underlying zones of articular cartilage at the level of gene expression. METHODS: Messenger RNA (mRNA) was isolated from chondrocytes harvested from the superficial and deep zones of immature bovine articular cartilage. This mRNA was reverse transcribed, radiolabeled, and then each complementary DNA (cDNA) sample was used to screen duplicate filters of a bovine chondrocyte cDNA library. By comparing autoradiographic signals on matching filter sets, clones exclusively expressed in the superficial zone of articular cartilage were isolated and characterized further. RESULTS: Of the superficial-specific gene clones isolated, 25% were found to be a single gene product, clusterin. Northern hybridization was used to show that clusterin is expressed specifically in the superficial zone of articular cartilage and that its expression is up-regulated in mature cartilage. In situ hybridization was used to precisely localize clusterin transcripts in articular cartilage, where it was found that clusterin expression was confined to the articular surface in both immature and mature samples. CONCLUSION: The discovery of clusterin expression at the articular cartilage surface extends previous observations that superficial articular chondrocytes are highly specialized cells. Clusterin is a multifunctional, secreted glycoprotein that has been shown to be expressed in diverse locations that have in common a tissue-fluid boundary. Additionally, clusterin has been implicated in regulating complement activation and cell death in injured and degenerating tissues.

Animals↗

PubMed2001

The development of articular cartilage: evidence for an appositional growth mechanism.

It is well-established that cartilage grows by a combination of matrix secretion, cell hypertrophy and cell proliferation. The extent to which this growth is by appositional, as opposed to interstitial mechanisms, however, remains unclear. Using the knee joints of the marsupial Monodelphis domestica to study cartilage growth, we have combined an immunohistochemical study of the TGF-beta family of cartilage growth and differentiation factors between 30 days postpartum to 8 months, together with a stereological analysis of cartilage morphology during growth. Furthermore, to gain an insight into the generation of the characteristic zones within cartilage, we have examined the effects of intra-articular administration of bromodeoxyuridine, an agent that is incorporated into DNA during cell division and blocks further cell cycling. During early growth, TGF-beta2 and -beta3 were widely expressed but TGF-beta1 was less so. After the formation of the secondary centre of ossification, all isoforms became more restricted to the upper half of the tissue depth and their distribution was similar to that previously described for IGFs, and PCNA-positive cells. Stereological analysis of tissue sections from the femoral condylar cartilage at 3 and 6 months showed that there was a 17% increase in total cartilage volume but a 31% decrease in cell density on a unit volume basis. Finally, cell-cycle perturbation with BrDU, which was injected into the knee joints of 3-month-old animals and analysed 1 and 4 months post-injection, revealed that the chondrocytes occupying the transitional zone were depleted 1 month post-injection, resulting in thinning of the articular cartilage. This effect was reversed 4 months post-injection. Immunohistochemical analysis revealed that BrDU-treatment altered the expression patterns of all TGF-beta isoforms, with a marked reduction in labelling of TGF-beta1 and -beta3 isoforms in the upper half of the cartilage depth. Overall, the data lends further support to the notion of articular cartilage growing by apposition from the articular surface rather than by interstitial mechanisms.

Animals↗

PubMed2001

Visceral artery aneurysm rupture.

PURPOSE: Aneurysms of the visceral arteries are infrequently encountered. Many are found incidentally and are thought to have a benign outcome. To better characterize these lesions and their clinical course, we reviewed our experience with visceral artery aneurysms (VAAs) at a single institution. METHODS: A retrospective analysis of all VAAs diagnosed at our institution over the past 10 years was performed. The presentation, management, and outcome of therapy was examined for each patient. RESULTS: Thirty-four VAAs in 26 patients were diagnosed over the past 10 years. Four patients had multiple VAAs: splenic (17), hepatic (7), celiac (3), superior mesenteric (2), gastroduodenal (2), pancreaticoduodenal (1), right gastric (1), ileal (1) artery aneurysms. Associated aneurysms were found in 31% of patients and involved the thoracic aorta (3 patients), abdominal aorta (4 patients), renal arteries (2 patients), iliac artery (3 patients), lower extremity (1 patient), and intracranium (1 patient). In 15 patients (58%), VAAs were detected before rupture by chance or because abdominal symptoms resulted in diagnostic evaluation. Eight of these underwent elective surgery, and there were no deaths. Of those 15 patients with known VAAs, one patient died of rupture and hemorrhage from an untreated splenic artery aneurysm. Eleven patients (42%) presented unexpectedly with rupture, and two died despite prompt surgical treatment. The mortality rate in patients who had ruptured VAAs was 25%, including those who presented with ruptured aneurysms and those observed whose aneurysms eventually ruptured. CONCLUSIONS: Aneurysms of the visceral arteries are rare but important vascular lesions. Associated aneurysms are common. Because of the risk of rupture, often with a fatal outcome, an aggressive approach to the treatment of VAA is essential.

Adolescent↗

PubMed2001

Differences in repair responses between immature and mature cartilage.

Cartilage has a poor reparative capacity although it is unclear as to what extent this may be dependent on age or maturation. In the current study, the cellular responses of chondrocytes to experimental wounding in vitro using embryonic, immature, and mature cartilage have been compared. In all cases, the response was consistent (a combination of cell death that included apoptosis and proliferation). The speed of response varied in terms of cell death with embryonic cartilage showing the most rapid response and mature cartilage showing the slowest response. Intrinsic repair as assessed by the ability to heal the lesion was not detected in any of the culture systems used. It was concluded that the poor repair potential of cartilage is not maturation dependent in the systems studied.

Animals↗

PubMed2001

Growth/differentiation factor-5 (GDF-5) and skeletal development.

BACKGROUND: Growth/differentiation factor-5 (GDF-5) has been shown to be essential for normal appendicular skeletal and joint development in humans and mice. In brachypod, a Gdf-5 gene mouse mutant, the defect is first apparent during early chondrogenesis, with the cartilage blastema already reduced in size by E12.5. This defect is associated with changes in the expression of cell surface molecules. METHODS: To understand further how GDF-5 controls cartilage formation, we first mapped the expression of the Gdf-5 gene during skeletal development (please note that the abbreviation for the gene is given in italics and the abbreviation for the protein expressed by the gene is given in capital letters). Subsequently, we over-expressed GDF-5 in the developing chick embryo using a replication competent retrovirus, RCAS(BP). We determined its effects on skeletal development by histological examination and its effects on early growth by autoradiography of proliferating cells. In addition, we examined the effect of GDF-5 on chondrogenic differentiation using micromass and single cell suspension cultures of limb mesenchymal cells, RESULTS: These studies show that the Gdf-5 gene is expressed in the early cartilage condensation, the perichondrium, and the joint interzone. Over-expresSion of GDF-5 in chick limb buds, during the condensation stage or later when the skeletal elements have formed, increased the size of the affected elements. In both cases, the increase in size was associated with an increase in cell number and, at later stages, this was correlated with an increase in S-phase cells. In vitro studies showed that GDF-5 could increase cell adhesiveness, and this may be a mechanism through which GDF-5 initiates condensation formation. CONCLUSION: These studies show that GDF-5 acts at two stages of skeletal development and by two distinct mechanisms. First, GDF-5 promotes the initial stages of chondrogenesis by promoting cell adhesion, which is consistent with the expression of Gdf-5 in the cartilage condensation. Second, GDF-5 can increase the size of the skeletal elements by increasing proliferation within the epiphyseal cartilage adjacent to its expression within the joint interzone.

Animals↗

PubMed2000

The reactions of articular cartilage to experimental wounding: role of apoptosis.

OBJECTIVE: To determine the cellular and matrix responses to experimental wounding of articular cartilage. METHODS: Immature and mature bovine articular cartilage was used as an in vitro model system to study the cellular responses to cartilage wounding. Explant cultures were wounded centrally with a trephine and maintained for up to 10 days. TUNEL labeling together with ultrastructural analyses were used to assess the nature of the observed cell death. In vitro labeling with 3H-thymidine was used to detect cell proliferation, and 2 antibodies (COL2-3/4M and BC-13) were used to detect changes in matrix turnover. RESULTS: Cell death was observed as a response to wounding and was considered to be a combination of necrosis and apoptosis. In immature tissue, cell death was more pronounced, particularly in the articular surface region. Within the area of cell death, many cells that did not die subsequently underwent proliferation. The collagenous network showed evidence of denaturation in the area of the wound, but "aggrecanase" activity was not detected. CONCLUSION: There are 2 contrasting, but related, responses to cartilage wounding--apoptosis and proliferation. In order to improve cartilage repair, future studies need to elucidate the regulatory mechanisms that determine these responses.

Animals↗

PubMed2000

Cellular responses of embryonic hyaline cartilage to experimental wounding in vitro.

It is well established that the reparative potential of many tissues is greatest during embryonic development. Despite the extensive literature documenting repair in nonembryonic cartilage models, there is no comparable wealth of experience relating to embryonic cartilage repair. With the embryonic chick sternum as a model of hyaline cartilage, this paper accounts cellular responses and alterations in extracellular matrix composition in response to experimental wounding in vitro. Creation of an experimental lesion induced a rapid (<20 minutes) apoptotic response in chondrocytes adjacent to the lesion edge; the presence of perichondrium delayed this response. Alterations in the extracellular matrix included immediate mechanical damage to type-II collagen fibrils and an increase in the expression of chondroitin-4 sulphate next to the lesion. Creation of the lesion induced an increased proliferative response in chondrocytes behind the zone of apoptosis and the expression of alpha5 and alpha6 integrin subunits.

Animals↗

PubMed1999

BMP/GDF-signalling interactions during synovial joint development.

The synovial joint arises from an initial condensation of cells that subsequently develops into distinct skeletal structures, separated by the joint. Bone morphogenetic proteins (BMPs) and growth and differentiation factors (GDFs) have a fundamental role during skeletogenesis, including joint formation. Development of the joint appears to be dependent on the differential expression/activity of the related BMP and GDF subfamilies. Gdf-5 is expressed in the developing joints and is necessary for the formation of some joints. In contrast, recent data has shown that antagonism of the BMP family is crucial for joint formation. Here, we review mechanisms of how BMP signalling may be antagonised/modified. We also describe the expression of Bmp-2 and Bmp-4 together with two BMP antagonists, chordin and noggin, during chick joint development. Finally, we discuss possible mechanisms of how a joint forms and the evidence that the joint is a 'signalling centre' that may coordinate the development of adjacent skeletal structures.

Animals↗

PubMed1999

The effect of mechanical strain on hyaluronan metabolism in embryonic fibrocartilage cells.

The development of the synovial joint cavity between the cartilage anlagen of the long bones is thought to be mediated by differential matrix synthesis at the developing articular surfaces. In addition, many studies have shown that removal of movement-induced mechanical stimuli from developing diarthrodial joints prevents cavity formation or produces a secondary fusion of previously cavitated joints. Herein, we describe an inductive influence of mechanical strain on hyaluronan metabolism and the expression of hyaluronan-binding proteins in cultured cells isolated from the articular surface of the distal tibial condyles of 18-day chick embryos. The effect of 10 min of mechanical strain on hyaluronan release into culture media, intracellular uridine diphospho-glucose dehydrogenase activity (an enzyme required for hyaluronan saccharide precursor production), cell surface hyaluronan-binding protein expression and HA synthase mRNA expression were analysed up to 24 h later. Six hours after the application of strain, there was a significant increase in the accumulation of hyaluronan released into tissue culture media by strained fibrocartilage cells compared with controls, an effect still detectable after 24 h. Strained cells also showed increased activity for uridine diphospho-glucose dehydrogenase and expressed higher levels of the hyaluronan-binding protein CD44 at 24 h. In addition, at 24 h mRNA for HA synthase 2 was expressed in all samples whereas mRNA for HA synthase 3 was only expressed in strained cells. These results further highlight the role for movement-induced stimuli in differential extracellular matrix metabolism during joint development and also show that strain may facilitate differential HA synthase gene expression.

Animals↗