Early changes in morphology, bone mineral density and matrix composition of vertebrae lead to disc degeneration in aged collagen IX -/- mice.

Collagen IX (Col IX) is an important component of the cartilage extracellularmatrix and has been associated with degenerative cartilage disorders and chondrodysplasias in humans. Further, polymorphisms in Col IX are known risk factors for the development of early intervertebral disc (IVD) degeneration. To understand the role of Col IX in the pathogenesis of IVD disorders, the spine of newborn and older Col IX deficient mice was systematically analyzed and compared to C57BL/6N controls. Morphology and bone parameters of the spine from newborn, 6 and 10 months old animals were investigated using µCT measurements. Histological staining was used to evaluate tissue structure and degree of degeneration. Localization and expression of extracellularmatrix proteins was analyzed in depth by immunofluorescence staining, immunoblotting, RT-PCR and in situ hybridization. High resolution imaging and stiffness measurements were performed by atomic force microscopy (AFM). Vertebral bodies of newborn Col IX-deficient mice were smaller and showed an increased mineral density compared to wild type animals. At birth, lack of Col IX led to a disrupted cellular organization in the cartilaginous endplate and a smaller nucleus pulposus of the IVD.Expression levels and localization of other extracellularmatrix proteins were strongly altered accompanied by a softening of cartilaginous tissues. In older animals, absence of Col IX caused earlier and more pronounced disc degeneration with annular fissures. The absence of Col IX induces early developmental, structural and biomechanical alterations in both vertebral body and intervertebral disc which eventually cause severe degenerative changes in the aging spine.

Moderate cyclic tensile strain alters the assembly of cartilage extracellular matrix proteins in vitro.

Mechanical loading influences the structural and mechanical properties of articular cartilage. The cartilage matrix protein collagen II essentially determines the tensile properties of the tissue and is adapted in response to loading. The collagen II network is stabilized by the collagen II-binding cartilage oligomeric matrix protein (COMP), collagen IX, and matrilin-3. However, the effect of mechanical loading on these extracellular matrix proteins is not yet understood. Therefore, the aim of this study was to investigate if and how chondrocytes assemble the extracellular matrix proteins collagen II, COMP, collagen IX, and matrilin-3 in response to mechanical loading. Primary murine chondrocytes were applied to cyclic tensile strain (6%, 0.5 Hz, 30 min per day at three consecutive days). The localization of collagen II, COMP, collagen IX, and matrilin-3 in loaded and unloaded cells was determined by immunofluorescence staining. The messenger ribo nucleic acid (mRNA) expression levels and synthesis of the proteins were analyzed using reverse transcription-polymerase chain reaction (RT-PCR) and western blots. Immunofluorescence staining demonstrated that the pattern of collagen II distribution was altered by loading. In loaded chondrocytes, collagen II containing fibrils appeared thicker and strongly co-stained for COMP and collagen IX, whereas the collagen network from unloaded cells was more diffuse and showed minor costaining. Further, the applied load led to a higher amount of COMP in the matrix, determined by western blot analysis. Our results show that moderate cyclic tensile strain altered the assembly of the extracellular collagen network. However, changes in protein amount were only observed for COMP, but not for collagen II, collagen IX, or matrilin-3. The data suggest that the adaptation to mechanical loading is not always the result of changes in RNA and/or protein expression but might also be the result of changes in matrix assembly and structure.

Stabilization effectiveness and functionality of different thumb orthoses in female patients with first carpometacarpal joint osteoarthritis.

BACKGROUND: Thumb orthoses have to reconcile and satisfy competing goals: stability and mobility. The purpose of the study was to characterize the stabilization effectiveness and functionality of different thumb carpometacarpal osteoarthritis orthoses. METHODS: Eighteen female carpometacarpal osteoarthritis subjects were included. Four orthoses were compared: BSN medical (BSN); Push braces (PUSH); Sporlastic (SPOR); and medi (MEDI). Three-dimensional thumb kinematics during active opposition-reposition with and without orthosis was quantified. Ranges-of-motion of the carpometacarpal and metacarpophalangeal joint in x- (flexion-extension), y- (adduction-abduction) and z-direction (pronation-supination) were determined. Hand functionality was examined by Sollerman test. FINDINGS: All orthoses restricted carpometacarpal range-of-motion in all directions. In x-direction carpometacarpal range-of-motion was smallest with MEDI and BSN, in y-direction largest with PUSH compared to all other orthoses, in z-direction smaller with BSN and MEDI compared to PUSH, but similar to SPOR. All orthoses restricted metacarpophalangeal range-of-motion in x-direction, except PUSH. In x-direction metacarpophalangeal range-of-motion was smallest with MEDI compared to all other orthoses. In y-direction and z-direction only BSN and MEDI restricted metacarpophalangeal range-of-motion. Sollerman score was highest with PUSH, lowest with MEDI and both differed from other orthoses. Values for BSN and SPOR were similar and lay between PUSH and MEDI. INTERPRETATION: Stabilization is borne by functionality. The high stabilization effectiveness provided by MEDI resulted in lowest hand functionality. PUSH, which partially stabilized the CMC joint and allowed large motions in the MCP joint, afforded largest hand functionality. Best compromise of stability and functionality could be reached with BSN. Long-term studies are needed to monitor clinical efficacy.

Effect of carpometacarpal joint osteoarthritis, sex, and handedness on thumb in vivo kinematics.

PURPOSE: To investigate the influence of trapeziometacarpal (TMC) osteoarthritis (OA) on the 3-dimensional motion capability of the TMC and thumb metacarpophalangeal (MCP) joints. In order to examine other factors affecting the thumb's motion kinematics, we further aimed to address the influence of sex and handedness on the motion capability of normal TMC and MCP joints. METHODS: We included 18 healthy subjects (9 women, 9 men; 8 dominant hands, 10 nondominant hands) and 18 women with stage II/III TMC OA. A motion analysis system using surface markers was used to quantify the thumb's 3-dimensional opposition-reposition kinematics. The range of motion of the thumb's TMC and MCP joints in flexion-extension, abduction-adduction, and pronation-supination were determined. RESULTS: TMC OA led to a loss in abduction-adduction in the TMC joint (38° in controls, 26° in TMC OA subjects), although neither flexion-extension nor pronation-supination were affected. At the MCP joint, the TMC OA subjects showed a 48% reduction in abduction-adduction (32° controls, 16° TMC OA subjects) and 42% reduction in pronation-supination (34° in controls, 20° in TMC OA subjects) than the healthy controls. Ranges of motion of the healthy TMC and MCP joints were similar in dominant and nondominant hands as well as in women and men. DISCUSSION: The study demonstrated that stage II/III TMC OA restricts the motion of the TMC joint in abduction-adduction and of the MCP joint in abduction-adduction and pronation-supination. Thumb motion capability was unaffected by sex and handedness. CLINICAL RELEVANCE: Osteoarthritis-induced loss of TMC motion did not reflect a generalizable clinical parameter, rather, it seemed to distinctly affect the TMC and the MCP joints and their motion planes and directions. As neither sex nor handedness influenced the motion capabilities of the healthy thumb, kinematic factors contributing to TMC OA may develop at a later age.

Topographical variations in articular cartilage and subchondral bone of the normal rat knee are age-related.

In osteoarthritis animal models the rat knee is one of the most frequently investigated joint. However, it is unknown whether topographical variations in articular cartilage and subchondral bone of the normal rat knee exist and how they are linked or influenced by growth and maturation. Detailed knowledge is needed in order to allow interpretation and facilitate comparability of published osteoarthritis studies. For the first time, the present study maps topographical variations in cartilage thickness, cartilage compressive properties and subchondral bone microarchitecture between the medial and lateral tibial compartment of normal growing rat knees (7 vs. 13 weeks). Thickness and compressive properties (aggregate modulus) of cartilage were determined and the subchondral bone was analyzed by micro-computed tomography. We found that articular cartilage thickness is initially homogenous in both compartments, but then differentiates during growth and maturation resulting in greater cartilage thickness in the medial compartment in the 13-week-old animals. Cartilage compressive properties did not vary between the two sites independently of age. In both age-groups, subchondral plate thickness as well as trabecular bone volume ratio and trabecular thickness were greater in the medial compartment. While a high porosity of subchondral bone plate with a high topographical variation (medial/lateral) could be observed in the 7-week-old animals, the porosity was reduced and was accompanied by a reversion in topographical variation when reaching maturity. Our findings highlight that there is a considerable topographical variation in articular cartilage and subchondral bone within the normal rat knee in relation to the developmental status.

Effect of whole-body vibration and insulin-like growth factor-I on muscle paralysis-induced bone degeneration after botulinum toxin injection in mice.

Botulinum toxin A (BTX)-induced muscle paralysis results in pronounced bone degradation with substantial bone loss. We hypothesized that whole-body vibration (WBV) and insulin-like growth factor-I (IGF-I) treatment can counteract paralysis-induced bone degradation following BTX injections by activation of the protein kinase B (Akt) signaling pathway. Female C57BL/6 mice (n = 60, 16 weeks) were assigned into six groups (n = 10 each): SHAM, BTX, BTX+WBV, BTX+IGF-I, BTX+WBV+IGF-I, and a baseline group, which was killed at the beginning of the study. Mice received a BTX (1.0 U/0.1 mL) or saline (SHAM) injection in the right hind limb. The BTX+IGF-I and BTX+WBV+IGF-I groups obtained daily subcutaneous injections of human IGF-I (1 µg/day). The BTX+WBV and BTX+WBV+IGF-I groups underwent WBV (25 Hz, 2.1 g, 0.83 mm) for 30 min/day, 5 days/week for 4 weeks. Femora were scanned by pQCT, and mechanical properties were determined. On tibial sections TRAP staining, static histomorphometry, and immunohistochemical staining against Akt, phospho-Akt, IGF-IR (IGF-I receptor), and phospho-IGF-IR were conducted. BTX injection decreased trabecular and cortical bone mineral density. The WBV and WBV+IGF-I groups showed no difference in trabecular bone mineral density compared to the SHAM group. The phospho-IGF-IR and phospho-Akt stainings were not differentially altered in the injected hind limbs between groups. We found that high-frequency, low-magnitude WBV can counteract paralysis-induced bone loss following BTX injections, while we could not detect any effect of treatment with IGF-I.

Doxycycline-induced expression of transgenic human tumor necrosis factor α in adult mice results in psoriasis-like arthritis.

OBJECTIVE: To generate doxycycline-inducible human tumor necrosis factor α (TNFα)-transgenic mice to overcome a major disadvantage of existing transgenic mice with constitutive expression of TNFα, which is the limitation in crossing them with various knockout or transgenic mice. METHODS: A transgenic mouse line that expresses the human TNFα cytokine exclusively after doxycycline administration was generated and analyzed for the onset of diseases. RESULTS: Doxycycline-inducible human TNFα-transgenic mice developed an inflammatory arthritis- and psoriasis-like phenotype, with fore and hind paws being prominently affected. The formation of "sausage digits" with characteristic involvement of the distal interphalangeal joints and nail malformation was observed. Synovial hyperplasia, enthesitis, cartilage and bone alterations, formation of pannus tissue, and inflammation of the skin epidermis and nail matrix appeared as early as 1 week after the treatment of mice with doxycycline and became aggravated over time. The abrogation of human TNFα expression by the removal of doxycycline 6 weeks after beginning stimulation resulted in fast resolution of the most advanced macroscopic and histologic disorders, and 3-6 weeks later, only minimal signs of disease were visible. CONCLUSION: Upon doxycycline administration, the doxycycline-inducible human TNFα-transgenic mouse displays the major features of inflammatory arthritis. It represents a unique animal model for studying the molecular mechanisms of arthritis, especially the early phases of disease genesis and tissue remodeling steps upon abrogation of TNFα expression. Furthermore, unlimited crossing of doxycycline-inducible human TNFα-transgenic mice with various knockout or transgenic mice opens new possibilities for unraveling the role of various signaling molecules acting in concert with TNFα.

Growth-related structural, biochemical, and mechanical properties of the functional bone-cartilage unit.

Articular cartilage and subchondral bone act together, forming a unit as a weight-bearing loading-transmitting surface. A close interaction between both structures has been implicated during joint cartilage degeneration, but their coupling during normal growth and development is insufficiently understood. The purpose of the present study was to examine growth-related changes of cartilage mechanical properties and to relate these changes to alterations in cartilage biochemical composition and subchondral bone structure. Tibiae and femora of both hindlimbs from 7- and 13-week-old (each n = 12) female Sprague-Dawley rats were harvested. Samples were processed for structural, biochemical and mechanical analyses. Immunohistochemical staining and protein expression analyses of collagen II, collagen IX, COMP and matrilin-3, histomorphometry of cartilage thickness and COMP staining height were performed. Furthermore, mechanical testing of articular cartilage and micro-CT analysis of subchondral bone was conducted. Growth decreased cartilage thickness, paralleled by a functional condensation of the underlying subchondral bone due to enchondral ossification. Cartilage mechanical properties seem to be rather influenced by growth-related changes in the assembly of major ECM proteins such as collagen II, collagen IX and matrilin-3 than by growth-related alterations in its underlying subchondral bone structure. Importantly, the present study provides a first insight into the growth-related structural, biochemical and mechanical interaction of articular cartilage and subchondral bone. Finally, these data contribute to the general knowledge about the cooperation between the articular cartilage and subchondral bone.

The effect of level and downhill running on cortical and trabecular bone in growing rats.

Mechanical loading is essential for bone development and prevention of age-related bone diseases. Muscular contractions during physical activity and the generated strain magnitude are primary determinants for the osteogenic response. However, the adaptation capacity of bones, especially due to different muscle contraction types, is largely unknown. In the present study we examined the effect of different running modes characterized by different muscle contraction types and loading patterns on the morphological, structural, and mechanical properties of different sites in the femur of growing rats. Thirty-six female Sprague-Dawley rats were randomly assigned to a nonactive age-matched control (AMC), a level running (LEVEL), and a 20° decline downhill running (DOWN) group (n = 12 each). Running groups were trained on a treadmill for 30 min/day, 5 days/week for 6 weeks. After death, pQCT analysis of the meta- and diaphyses, micro-CT analysis of the epiphysis, and mechanical testing of the femur were performed. The Tb.BMD in the metaphysis was significantly (P < 0.05) increased in the DOWN compared to the AMC group, whereas level running had no effect on Tb.BMD. While Young's modulus was significantly different (P < 0.05) between the DOWN and LEVEL groups, no structural alterations were found in the diaphysis between the groups. Further, subchondral trabecular bone did not show exercise-induced changes caused by the different running modes but displayed a remarkably high intraepiphyseal variability. Downhill running seems to be a potent osteogenic stimulus in the femoral metaphysis.