Biomedical subjects

Stefan Milz

Publications and source records attributed to Stefan Milz.

At least 19 recordsLinked to original sources

PubMed2006

Biomechanical and immunohistochemical analysis of high hydrostatic pressure-treated Achilles tendons.

BACKGROUND: Reconstruction of bone defects caused by malignant tumors is carried out in different ways. At present, tumor-bearing bone segments are devitalized mainly by extracorporeal irradiation or autoclaving, but both methods have substantial disadvantages. In this regard, high hydrostatic pressure (HHP) treatment of the bone is a new, advancing technology that has been used in preclinical testing to inactivate normal cells and tumor cells without altering the biomechanical properties of the bone. The aim of this study was to examine the biomechanical and immunohistochemical properties of tendons after exposure to HHP and to evaluate whether preservation of the bony attachment of tendons and ligaments is possible. METHODS: For this, 19 paired Achilles tendons were harvested from both hindlimbs of 4-month-old pigs. After preparation, the cross-sectional area of each tendon was determined by magnetic resonance imaging (MRI). For each animal, one of the two tendons was taken at random and exposed to a pressure of 300 MPa (n = 9) or 600 MPa (n = 10). RESULTS: The contralateral tendon served as an untreated control. The biomechanical properties of the tendons remained unchanged with respect to the tested parameters: Young's modulus (MPa) and tensile strength (MPa). This finding is in line with immunohistochemical labeling results, as no difference in the labeling pattern of collagen I and versican was observed when comparing the HHP group (at 600 MPa) to the untreated control group. CONCLUSIONS: We anticipate that during orthopedic surgery HHP can serve as a novel, promising methodical approach to inactivate Achilles tendon and bone cells without altering the biomechanical properties of the tendons. This should allow one to preserve the attachment of tendon and ligaments to the devitalized bone and to facilitate functional reconstruction.

Achilles Tendon↗

PubMed2006

[Biomechanical properties of articular cartilage after high hydrostatic pressure treatment].

AIM: Reconstruction of bone defects due to malignant tumors can be realized by several methods. Up to now, two methods, irradiation and autoclaving, are available for extracorporeally devitalizing resected tumor-bearing osteochondral segments. Previous investigations have shown that human normal and tumor cells in culture were irreversibly impaired when subjected to extracorporeal high hydrostatic pressure (HHP) of 350 MPa. The aim of this study was to examine the biomechanical and immunohistochemical properties of cartilage after exposure to HHP MATERIALS AND METHODS: Osteochondral segments of bovine femoral condyles were exposed to pressure of 300 and 600 MPa (n=20 each). Biomechanical and biological properties of untreated and treated segments were evaluated by repetitive ball indention testing and immunohistochemical labelling aggrecan, link protein and collagen II. The contralateral segments served as untreated control. RESULTS: No significant alterations concerning stiffness and relaxation of osteochondral segments even after 600 MPa were observed. Immunohistochemically, staining was positive in all cases and no differences in the labeling pattern of proteoglycanes were observed between untreated and HHP-treated specimens. CONCLUSION: These findings give hope that HHP eventually will be used as a new gentle way of treating resected cartilage and bone without alteration of biomechanical properties to inactivate tumor cells in order to allow autologous reimplantation.

Animals↗

PubMed2006

Material properties of and tissue reaction to the Slocum TPLO plate.

OBJECTIVE: To determine the material properties of Slocum TPLO plates and assess the soft tissue reaction adjacent to these plates in dogs that had undergone tibial plateau leveling osteotomy (TPLO). SAMPLE POPULATION: 3 new TPLO plates, 8 retrieved TPLO plates, and 1 new Synthes dynamic compression plate. PROCEDURES: Metallurgic analyses were performed. Tissue samples were obtained from areas adjacent to retrieved plates and submitted for histologic examination. RESULTS: All of the TPLO plates had a 2-phase microstructure consisting of austenite and ferrite in various amounts. Residua, inclusions, and cavities were seen during microscopic examination of the plate surface. The major differences between new and retrieved TPLO plates were the presence of small gaps separating many inclusions from the surrounding matrix and the presence of various-sized pits on the surface of the retrieved plates. The dynamic compression plate had a nearly pure austenitic structure and was largely free from residua, inclusions, and cavities. Histologic examination of tissue samples obtained from areas adjacent to retrieved TPLO plates revealed intra- and extracellular particulate debris. Two types of particles (one consisting of chromium, nickel, molybdenum, and iron and the other consisting of aluminum and silicon) were seen. CONCLUSIONS AND CLINICAL RELEVANCE: Results determined that new and retrieved TPLO plates were manufactured from 316L stainless steel and produced by a casting process, but not all plates met specifications for chemical composition of cast surgical implants (American Society for Testing Materials standard F745); tissues surrounding retrieved plates had evidence of adverse reactions, probably as a result of plate corrosion.

Animals↗

PubMed2005

An immunohistochemical study of the tissue bridging adult spondylolytic defects--the presence and significance of fibrocartilaginous entheses.

UNLABELLED: Introduction Spondylolytic spondylolisthesis is an osseous discontinuity of the vertebral arch that predominantly affects the fifth lumbar vertebra. Biomechanical factors are closely related to the condition. An immunohistochemical investigation of lysis-zone tissue obtained from patients with isthmic spondylolisthesis was performed to determine the molecular composition of the lysis-zone tissue and enable interpretation of the mechanical demands to which the tissue is subject. METHODS: During surgery, the tissue filling the spondylytic defects was removed from 13 patients. Twelve spondylolistheses were at the L5/S1 level with slippage being less than Meyerding grade II. Samples were methanol fixed, decalcified and cryosectioned. Sections were labelled with a panel of monoclonal antibodies directed against collagens, glycosaminoglycans and proteoglycans. RESULTS: The lysis-zone tissue had an ordered collagenous structure with distinct fibrocartilaginous entheses at both ends. Typically, these had zones of calcified and uncalcified fibrocartilage labelling strongly for type II collagen and aggrecan. Labelling was also detected around bony spurs that extended from the enthesis into the lysis-zone. The entheses also labelled for types I, III and VI collagens, chondroitin four and six sulfate, keratan and dermatan sulfate, link protein, versican and tenascin. CONCLUSIONS: Although the gap filled by the lysis tissue is a pathological feature, the tissue itself has hallmarks of a normal ligament-i.e. fibrocartilaginous entheses at either end of an ordered collagenous fibre structure. The fibrocartilage is believed to dissipate stress concentration at the hard/soft tissue boundary. The widespread occurrence of molecules typical of cartilage in the attachment of the lysis tissue, suggests that compressive and shear forces are present to which the enthesis is adapted, in addition to the expected tensile forces across the spondylolysis. Such a combination of tensile, shear and compressive forces must operate whenever there is any opening or closing of the spondylolytic gap.

Adult↗

PubMed2005

Local statin therapy differentially interferes with smooth muscle and endothelial cell proliferation and reduces neointima on a drug-eluting stent platform.

OBJECTIVE: Therapeutic strategies to provide local inhibition of mitogen mediated proliferation and migration of human coronary artery smooth muscle cells (CASMC) by means of drug-eluting stents have been shown to enable effective limitation of neointimal hyperplasia. However, currently available drug-eluting stents utilize compounds that may also adversely affect endothelial regrowth, thus possibly precipitating subsequent cardiac events. Accordingly, identification of compounds that differentially inhibit smooth muscle and endothelial cell migration and proliferation could be of substantial clinical usefulness. METHODS AND RESULTS: In addition to lipid lowering, statins are known to display auxiliary pleiotropic activities. The purpose of this study was to evaluate the effect of local administration of cerivastatin on proliferation, migration and cytotoxicity of CASMC as well as coronary artery endothelial cells (CAEC) and to evaluate the effect of cerivastatin-coated stents on the inhibition of neointima formation as well as endothelial regrowth within the stented vessel. Cerivastatin displayed a differential effect on CASMC as compared to CAEC with regard to proliferation and migration; both were more profoundly inhibited in CASMC. Appreciable cytotoxicity and pro-apoptotic effects were low in both cell lines at therapeutic concentrations. Cerivastatin-elution led to significant inhibition of neointima formation in the rat carotid stent model, endothelial coverage of in-stent vascular tissue was similar with control and cerivastatin-eluting stents. CONCLUSIONS: As proof of principle, our study provides evidence that local application of a HMG-CoA reductase inhibitor on a drug-eluting stent platform can efficiently limit neointima formation. Consequently, these compounds warrant further clinical evaluation to confirm this finding. Our data further suggest that the anti-restenotic effect of local statin administration might be associated with a more protective interaction with the endothelium than that observed with compounds currently employed on drug-eluting stents.

Animals↗

PubMed2005

Detailed pathological changes of human lumbar facet joints L1-L5 in elderly individuals.

Facet joints play an important role in intervertebral load transmission and are crucial for rotational kinematics. Clinically, the role of facet joints as a possible source of low back pain is seen as controversial and at present is not sufficiently investigated. In this study, human lumbar facet (zygapopyhysial) joints from donors with advanced age were analyzed macroscopically, for degenerative changes. The aim was to determine the extent and morphology of degenerative changes in these joints. Lumbar facet joints (L1-L5) of 32 donors were studied (mean age 80.1+/-11.2 years). Joint capsules were carefully removed and joint surfaces (5 zones) examined using magnifying glasses and probes. In the result, the majority of facet joints showed cartilage defects of varying extent. Defects were located mostly at the margins of the articular surface, the central zone being relatively well preserved. Defect localization was different between superior (most cartilage defects in superior zone) and inferior (most defects inferiorly) facets. Further, defects were more severe caudal (level of L5) and in older persons. Osteophytes were present in up to 30%, located mostly at the latero-dorsal enthesis of the joint capsule on the superior facet. In conclusion, most margins of the articular facets are subject to degenerative changes in the lumbar spine of elderly persons, the topographical pattern being different in superior and inferior facets. This observation can be explained by the segmental motion patterns during extension/flexion movements of the facets. Sometimes, due to the marginal extension, it is obvious that not all changes can be assessed by CT or MRI.

Age Factors↗

PubMed2005

Inhibition of neointima formation by a novel drug-eluting stent system that allows for dose-adjustable, multiple, and on-site stent coating.

OBJECTIVE: The risk of in-stent restenosis can be considerably reduced by stents eluting cytostatic compounds. We created a novel drug-eluting stent system that includes several new features in the rapidly evolving field of stent-based drug delivery. METHODS AND RESULTS: The aim of the present study was the preclinical evaluation of a stent-coating system permitting individual, on-site coating of stents with a unique microporous surface allowing for individualizable, dose-adjustable, and multiple coatings with identical or various compounds, designated ISAR (individualizable drug-eluting stent system to abrogate restenosis). Stents were coated with 0.75% rapamycin solution, and high-performance liquid chromatography (HPLC)-based determination of drug release profile indicated drug release for >21 days. Rapamycin-eluting microporous (REMP) stents implanted in porcine coronary arteries were safe. To determine the efficacy of REMP stents, this novel drug-eluting stent platform was compared with the standard sirolimus-eluting stent. At 30 days, in-stent neointima formation in porcine coronary arteries was similar in both groups, yielding a significant decrease of neointimal area and injury-dependent neointimal thickness compared with bare-metal stents. CONCLUSIONS: The ISAR drug-eluting stent platform as a novel concept for stent coating allows for a safe, effective, on-site stent coating process, thus justifying further clinical evaluation to decrease in-stent restenosis in humans.

Animals↗

PubMed2005

In vivo animal trials with a scanning CO2 laser osteotome.

BACKGROUND AND OBJECTIVES: We report first results of animal trials using an improved laser osteotomy technique. This technique allows effective bone cutting without the usual thermal tissue damage. STUDY DESIGN/MATERIALS AND METHODS: A comparative in vivo study on mandibles of seven canines was done with a mechanical saw and a CO(2) laser based osteotome with a pulse duration of 80 microseconds. The laser incisions were performed in a multipass mode using a PC-controlled galvanic beam scanner and an assisting water spray. RESULTS: A complete healing through a whole bony rearrangement of the osteotomy gap with newly build lamellar Haversian bone was observed 22 days after the laser operations under optimal irradiation conditions. CONCLUSIONS: An effective CO(2) laser osteotomy without aggravating thermal side effects and healing delay is possible using the described irradiation technique. It allows an arbitrary cut geometry and may result in new advantageous bone surgery procedures.

Animals↗

PubMed2005

Hydroxyapatite scaffolds for bone tissue engineering made by 3D printing.

Nowadays, there is a significant need for synthetic bone replacement materials used in bone tissue engineering (BTE). Rapid prototyping and especially 3D printing is a suitable technique to create custom implants based on medical data sets. 3D printing allows to fabricate scaffolds based on Hydroxyapatite with complex internal structures and high resolution. To determine the in vitro behaviour of cells cultivated on the scaffolds, we designed a special test-part. MC3T3-E1 cells were seeded on the scaffolds and cultivated under static and dynamic setups. Histological evaluation was carried out to characterise the cell ingrowth. In summary, the dynamic cultivation method lead to a stronger population compared to the static cultivation method. The cells proliferated deep into the structure forming close contact to Hydroxyapatite granules.

3T3 Cells↗

PubMed2005

Polychrome labeling of bone with seven different fluorochromes: enhancing fluorochrome discrimination by spectral image analysis.

Bone formation and remodeling in vivo can be assessed by polychrome labeling using calcium-binding fluorescent dyes. The number of fluorochromes, however, limits this technique due to the fact that with increasing number, fluorescent spectra inevitably overlap, which makes discrimination more difficult. In order to enhance discrimination, we performed spectral image analysis. Non-critical size defects of the femur of male Wistar rats served as a model for bone formation. Eight different fluorochromes (calcein blue, xylenol orange, calcein, alizarine complexone, doxycycline, rolitetracycline, hematoporphyrin, and BAPTA) were administered sequentially subcutaneously every third day starting at day 4 after surgery. Following, bone specimen were embedded in methylmethacrylate and analyzed by spectral image acquisition using a Sagnac type interferometer (ASI, Israel). Seven of the eight applied fluorochromes could be resolved using spectral image examination. With BAPTA, we present a new fluorochrome suitable for bone labeling. Due to the superior sensitivity of the spectral image acquisition, the thickness of the bone sections could be reduced so that 5 mum thick sections could be analyzed. Spectral decomposition and subsequent linear unmixing allows depiction of each individual fluorochrome without interference of any other, enabling a reliable and superior morphometric analysis of labeled regions.

Animals↗

PubMed2005

An immunohistochemical study of the extracellular matrix of the tarsal plate in the upper eyelid in human beings.

The superior tarsus is a plate of tissue that stiffens the upper eyelid, gives it support and determines its form. The purpose of the present study was to relate the composition of its extracellular matrix to its function and to report regional differences that may influence the activity of its Meibomian glands. Fourteen methanol-fixed specimens were cryosectioned for immunohistochemistry and labelled with a panel of monoclonal antibodies against a wide range of collagens, glycosaminoglycans and proteoglycans. Labelling was detected with avidin-biotin-peroxidase. A further six specimens were formalin-fixed for routine histology. The tarsal plate immunolabelled strongly for types I, III and VI collagen and for aggrecan, versican, tenascin, cartilage oligomeric matrix protein (COMP) together with a variety of glycosaminoglycans (notably chondroitin 6 sulphate). A region of strong labelling for aggrecan, dermatan sulphate and chondroitin 6 sulphate immediately surrounded the Meibomian glands. The site of labelling corresponded to a layer of acellular and amorphous matrix seen histologically that we have termed the 'territorial matrix'. The results suggested that the tarsal plate is a specialized connective tissue that is neither purely fibrous nor cartilaginous, yet has an aggrecan content that probably contributes to its stiffness. Its unique character highlights the challenge in choosing an ideal mechanical substitute. As patients with rheumatoid arthritis often have problems relating to tear film deficiency, the ability of aggrecan or COMP to act as autoantigens may be significant. An immune reaction directed against these molecules could alter tarsal gland function by interfering with the interaction between the glands and their territorial matrix.

Adult↗

PubMed2004

Local cyclin-dependent kinase inhibition by flavopiridol inhibits coronary artery smooth muscle cell proliferation and migration: Implications for the applicability on drug-eluting stents to prevent neointima formation following vascular injury.

In-stent restenosis is a hyperproliferative disease which can be successfully treated by drug-eluting stents releasing compounds that exhibit cell-cycle inhibitory properties to inhibit coronary smooth muscle cell (CASMC) proliferation and migration, resembling the key pathomechanisms of in-stent restenosis. Cyclin-dependent kinases (CDK) are key regulators of the eukaryotic cell cycle. CDK activity may be blocked by novel compounds such as flavopiridol. Therefore, CDK inhibitors are attractive drugs to be used for the local prevention of in-stent restenosis. In this study, we demonstrate that flavopiridol leads to potent inhibition of CASMC proliferation and migration. Molecular effects on cell-cycle regulatory mechanisms and distribution were evaluated by post-transcriptional assessment of distinct cyclins and cyclin-dependent kinase inhibitor (CKI) levels and flow cytometry. Cellular necrosis and apoptosis was assessed in CASMC and coronary endothelial cells. Flavopiridol induced a potent antiproliferative effect by cell-cycle inhibition in G1 and G2/M and led to increased protein levels of CKIs p21cip1 and p27kip1 as well as p53 in CASMC. Hyperphosphorylation of retinoblastoma protein was abrogated and mitogen-mediated smooth muscle cell migration significantly reduced. No accelerated cytotoxicity or increased apoptosis was detectable. Flavopiridol-coated stents, implanted in rat carotid arteries, led to significant decrease of neointima formation. As proof of principle, our results demonstrate that stents eluting CDK inhibitors such as flavopiridol effectively inhibit neointima formation. Therefore, this new class of therapeutics may be suitable for further clinical investigations on drug-eluting stents to prevent in-stent restenosis.

Animals↗

PubMed2004

Dual role of CCR2 during initiation and progression of collagen-induced arthritis: evidence for regulatory activity of CCR2+ T cells.

Chemokines play an important role in the recruitment of leukocytes and have recently been shown to also attract regulatory T cells. Using blocking mAbs, we analyzed the role of the chemokine receptor CCR2 during initiation and progression of collagen-induced arthritis in mice. Blockade of CCR2 from days 0 to 15 markedly improved clinical signs of arthritis and histological scores measuring leukocyte infiltration, synovial hyperplasia, and bone and cartilage erosion. CCR2 blockade during disease initiation significantly reduced plasma titers of collagen Abs in vivo. In vitro CCR2 blockade also interfered with collagen-specific activation and proliferation of T cells. Surprisingly, CCR2 blockade from days 21 to 36 markedly aggravated clinical and histological signs of arthritis and increased the humoral immune response against collagen. We show that CCR2 is expressed on regulatory T cells. Purified CCR2+ T cells are fully anergic toward polyclonal and collagen-specific activation and potently suppress activation of other T and B cells. The subpopulation of CCR2+ CD25+ regulatory T cells increases approximately 5-fold in the progression phase, while CCR2 expression on other leukocyte populations remains unchanged. These findings identify CCR2+ T cells as regulatory T cells and indicate that CCR2 also plays an important role in down-modulating an inflammatory response.

Animals↗

PubMed2004

The use of four-colour immunofluorescence techniques to identify mesenchymal stem cells.

In stem-cell research a major difficulty is caused by the lack of distinctive features that allow the identification of human mesenchymal stem cells (hMSC). Until now, there has been no specific marker and the most common way to identify hMSC is by their characteristic stem-cell properties: self-replication and differentiation potential. However, these findings can only be revealed retrospectively, and, once differentiated, hMSC lose their stem-cell character. The aim of this study was to establish four-colour immunofluorescence of several markers simultaneously in order to address the problem of how to identify hMSC on the single-cell level. The four markers collagen-I, collagen-IV, fibronectin and CD44 are known to be expressed by hMSC. Antibody binding was detected using secondary antibodies conjugated to FITC, Alexa546, TexasRed and AMCA. Because the distinction between Alexa546 and TexasRed was not possible on conventional digital images using standard filter sets, we performed spectral image acquisition. The image was subsequently decomposed into its pure spectral components, which permitted linear unmixing. Using this procedure we were able to demonstrate four-colour immunofluorescence on hMSC. With the possibility of using more sophisticated marker profiles and/or additional markers, four-colour immunofluorescence offers the opportunity of identifying hMSC on the single-cell level without performing differentiation assays.

Cell Separation↗

PubMed2003

Substance P and prostaglandin E2 release after shock wave application to the rabbit femur.

The biologic action of extracorporeal shock wave application on the musculoskeletal system is poorly understood. To prove the hypothesis that alterations of tissue concentrations of substance P and prostaglandin E(2) are involved in the biologic action of shock waves, extracorporeal shock waves with energy flux density of 0.9 mJ/mm2 (1500 pulses at 1/second) were applied in vivo to the distal femur of rabbits. The concentrations of substance P and prostaglandin E(2) eluted from the periosteum of the femur were measured. Compared with the untreated contralateral hindlimbs, substance P release from the periosteum from the femur was increased 6 hours and 24 hours after extracorporeal shock wave application, but was decreased 6 weeks after extracorporeal shock wave application. By contrast, extracorporeal shock wave application did not result in altered prostaglandin E(2) release from the periosteum from the femur. Remarkably, there was a close relationship between the time course of substance P release found here, and the well-known clinical time course of initial pain occurrence and subsequent pain relief after extracorporeal shock wave application to tendon diseases. Accordingly, substance P might be involved in the biologic action of extracorporeal shock wave application on tissue of the musculoskeletal system. This is the first study providing insights into the molecular mechanisms of extracorporeal shock wave application to the musculoskeletal system.

Analysis of Variance↗

PubMed2003

Immunohistochemical analysis of the extracellular matrix in the posterior capsule of the zygapophysial joints in patients with degenerative L4-5 motion segment instability.

OBJECT: Although the hypertrophied shape of the zygapophysial joints in degenerative instability of the lumbar spine is well known, its underlying pathophysiological mechanism is unclear. The authors sought to provide evidence that there is increased fibrocartilaginous metaplasia in the posterior joint capsule resulting from greater mechanical loading; the authors suggest that these capsular changes are central to understanding the altered joint shape. METHODS: The LA-5 posterior articular complex was removed in 14 patients undergoing fusion for degenerative instability. After methanol-assisted fixation, cryosections were immunolabeled for a wide range of extracellular matrix molecules. These were collagens (Types I, II, III, V, and VI), glycosaminoglycans (chondroitin 4 and 6 sulfates; dermatan- and keratan-sulfate), and proteoglycans (versican, tenascin, aggrecan, and its associated link protein). The grade of degeneration of the articular complexes was assessed radiologically and histologically. CONCLUSIONS: The results of this study provide molecular evidence for an altered loading history on the joint capsule. The pronounced loss of intervertebral disc height that occurred in all patients with severe degeneration of the lumbar motion segment promotes an increased range of axial rotation that places the posterior capsule under greater mechanical load. Compared with normal joints studied previously, the posterior capsules involved in these degenerative joint complexes were hypertrophied and fibrocartilaginous throughout. Cartilaginous metaplasia was especially pronounced at the attachment sites (entheses) where the fibrocartilage now extended beyond the original level of the joint space, and capped the osseous spurs arising from these attachment sites.

Adult↗

PubMed2003

The structure and histopathology of the "enthesis organ" at the navicular insertion of the tendon of tibialis posterior.

OBJECTIVE: To investigate the structure, histopathology, and molecular composition of tissue specializations of the tibialis posterior enthesis. They collectively reduce stress concentration at the insertion site and are part of an "enthesis organ." This has implications for understanding the basis of enthesopathy. METHODS: Fifty-two specimens of tibialis posterior and the associated superomedial part of the calcaneonavicular ligament taken from cadavers were sectioned longitudinally and examined by routine histology (42 samples) or immunohistochemistry (10 samples). Serial sections of formalin fixed material were stained with Masson's trichrome, toluidine blue, or hematoxylin, eosin and alcian blue. A panel of antibodies against collagens, glycosaminoglycans, and proteoglycans was used to immunolabel methanol fixed material. RESULTS: The enthesis organ consists of the enthesis itself, the superomedial part of the calcaneonavicular ligament (which may fuse with the tendon), the tendon sheath, and associated accessory bones. The accessory bones lay in a region of fibrocartilage that was present even in specimens where the bones themselves were absent. Degenerative changes were seen at the enthesis, around the accessory bones, and in the walls of the tendon sheath. The navicular and accessory bone entheses, together with the calcaneonavicular ligament, were all rich in fibrocartilage. This immunolabeled for aggrecan, link protein, type II collagen, and versican. CONCLUSION: The complexity of the enthesis organ, and the diversity of sites showing histopathological changes, suggest that enthesopathy may not be located precisely at the osteotendinous junction. It could target a number of adjacent locations, in accord with what happens at other entheses; e.g., in patients with spondyloarthropathy. The prominence of fibrocartilage in the enthesis organ, and the degenerative changes to which it is subject, support the view that spondyloarthropathy has an underlying biomechanical basis.

Aged↗

PubMed2003

Expression of a wide range of fibrocartilage molecules at the entheses of the alar ligaments - possible antigenic targets for rheumatoid arthritis?

OBJECTIVE: To provide evidence for the existence of a wide range of molecules characteristic of fibrocartilage at normal alar ligament entheses, that may have a bearing on the pathogenesis of rheumatoid arthritis. The alar ligaments provide the mechanical restraint for head rotation and their integrity can be compromised in patients with RA and occasionally in those with spondyloarthropathy. METHODS: Both alar ligaments from 6 cadavers were fixed in 90% methanol and cryosectioned longitudinally. Sections were immunolabelled with antibodies against collagens, glycosaminoglycans, and proteoglycans. The immunohistochemical data were related to estimates of insertional angle change at the entheses that were calculated from measurements of ligament length and dens diameter. RESULTS: Molecules typical of fibrocartilage (including type II collagen, link protein, and aggrecan) were found at both entheses, but labelling was more prominent at the odontoid end. This correlated with a 3-fold greater insertional angle change during 40 degrees of head rotation at the attachment of the ligament to the dens. At the odontoid enthesis, fibrocartilage differentiation was most conspicuous posteriorly. CONCLUSION: The changes in insertional angle mean that compressive forces are prominent at both entheses, but particularly at the odontoid end, where the ligament partly wraps around the dens during head rotation. Thus, mechanical conditions are created that lead to pronounced fibrocartilage development, hence the expression of type II collagen, link protein, and aggrecan. The prominence of these molecules at the entheses raises the possibility that they could be antigenic targets for an autoimmune response in rheumatic diseases.

Aged↗