Loading and knee alignment have significant influence on cartilage MRI T2 in porcine knee joints.

OBJECTIVE: Physiological magnetic resonance imaging (MRI) under loading or knee malalignment conditions has not been thoroughly investigated. We assessed the influence of static loading and knee alignment on T2 (transverse relaxation time) mapping of the knee femoral cartilage of porcine knee joints using a non-metallic pressure device. METHODS: Ten porcine knee joints were harvested en bloc with intact capsules and surrounding muscles and imaged using a custom-made pressure device and 3.0-T MRI system. Sagittal T2 maps were obtained (1) at knee neutral alignment without external loading (no loading), (2) under mechanical compression of 140 N (neutral loading), and (3) under the same loading conditions as in (2) with the knee at 10 degrees varus alignment (varus loading). T2 values of deep, intermediate, and superficial zones of the medial and lateral femoral cartilages at the weight-bearing area were compared among these conditions using custom-made software. Cartilage contact pressure between the femoral and tibial cartilages, measured by a pressure-sensitive film, was correlated with cartilage T2 measurements. RESULTS: In the medial cartilage, mean T2 values of the deep, intermediate, and superficial zones decreased by 1.4%, 13.0%, and 6.0% under neutral loading. They further decreased by 4.3%, 19.3%, and 17.2% under varus loading compared to no loading. In the lateral cartilage, these mean T2 values decreased by 3.9%, 7.7%, and 4.2% under neutral loading, but increased by 1.6%, 9.6%, and 7.2% under varus loading. There was a significant decrease in T2 values in the intermediate zone of the medial cartilage under both neutral and varus loading, and in the superficial zone of the medial cartilage under varus loading (P<0.05). Total contact pressure values under neutral loading and varus loading conditions significantly correlated with T2 values in the superficial and intermediate zones of the medial cartilages. CONCLUSIONS: The response of T2 to change in static loading or alignment varied between the medial and lateral cartilages, and among the deep, intermediate, and superficial zones. These T2 changes were significantly related to the contact pressure measurements. Our results indicate that T2 mapping under loading allows non-invasive, biomechanical assessment of site-specific stress distribution in the cartilage.

Calcium hydroxyapatite ceramic implants in bone tumour surgery. A long-term follow-up study.

We reviewed the results of 51 patients with benign bone tumours treated by curettage and implantation of calcium hydroxyapatite ceramic (CHA). The mean follow-up was 11.4 years (10 to 15.5). Post-operative fractures occurred in two patients and three had local recurrences; three had slightly limited movement of the adjacent joint and one had mild osteoarthritis. There were no allergic or neoplastic complications. In all cases, radiographs showed that the CHA was well incorporated into the host bone. Statistical analysis showed that absorption of the implanted CHA was greater in males (odds ratio, 6.2; 95% CI, 1.6 to 23.7) and younger patients (odds ratio, 0.6 for increase in age of 10 years; 95% CI, 0.91 to 0.99). However, the implanted CHA was not completely absorbed in any patient. We conclude that CHA is a useful and safe bone substitute for the treatment of benign bone tumours.

Comparison of the activities of multinucleated bone-resorbing giant cells derived from CD14-positive cells in the synovial fluids of rheumatoid arthritis and osteoarthritis patients.

OBJECTIVE: To investigate the morphology and function of multinucleated bone-resorbing giant cells derived from CD14-positive cells in the synovial fluids (SF) of patients with rheumatoid arthritis (RA) or osteoarthritis (OA). METHODS: CD14-positive cells were obtained by magnetic-activated cell sorting of primary cultures of mononuclear cells from the SF. Multinucleated bone-resorbing giant cells were induced from the CD14-positive cells in the presence or absence of cytokines. We examined various characteristics, including osteoclast markers, fusion index and bone-resorption activities of the multinucleated giant cells. RESULTS: Multinucleated giant cells were induced from the CD14-positive cells in the SF of the RA and OA patients by the addition of interleukin (IL)-3, IL-5 and IL-7, or granulocyte-macrophage colony-stimulating factor (GM-CSF), respectively. These multinucleated giant cells were positive for tartrate-resistant acid phosphatase (TRAP), carbonic anhydrase II, actin, vitronectin receptor and the calcitonin receptor. However, the average values for the number of nuclei, fusion index and bone-resorption functions of the SF cells from the RA patients were significantly higher than those derived from the OA patients. CONCLUSION: These results suggest that the induction and activities of multinucleated bone-resorbing giant cells may play a pivotal role in bone destruction, and that these processes may be enhanced significantly in RA patients.

Localization of bone morphogenetic protein-2 in human osteoarthritic cartilage and osteophyte.

OBJECTIVES: To examine the localization of bone morphogenetic protein (BMP)-2 mRNA and protein in human osteoarthritic (OA) articular cartilage and osteophyte. DESIGN: Five normal, four growing and 14 OA human cartilage samples, graded histomorphologically by Mankin Score, were studied by in situ hybridization and immunohistochemistry for the expression of BMP-2. RESULTS: BMP-2 mRNA was present in chondrocytes in neonatal growing articular cartilage, but was scarcely present in normal adult articular cartilage. In OA articular cartilage, BMP-2 mRNA and protein were detected in both clustering and individual chondrocytes in moderately or severely damaged OA cartilage. In moderately damaged OA cartilage, BMP-2 mRNA was localized in both upper and middle zone chondrocytes, but was not detected in deep layer chondrocytes. In severely damaged OA cartilage, cellular localization of BMP-2 mRNA was extended to the deep zone. In the area of osteophyte formation, BMP-2 mRNA was intensely localized in fibroblastic mesenchymal cells, fibrochondrocytes, chondrocytes and osteoblasts in newly formed osteophytic tissue. The pattern of BMP-2/4 immunolocalization was associated with that of mRNA localization. CONCLUSIONS: BMP-2 mRNA and BMP-2/4 were detected in cells appearing in OA tissues. BMP-2 was localized in cells of degenerating cartilage as well as osteophytic tissue. Given the negative localization of BMP-2 in normal adult articular cartilage, BMP-2 might be involved in the regenerating and anabolic activities of OA cells, which respond to cartilage damage occurring in osteoarthritis.

Expression and distribution of transcripts for sonic hedgehog in the early phase of fracture repair.

Localization and expression of mRNAs for sonic hedgehog (Shh) at a fracture site in the early phase postfracture were investigated by in situ hybridization and reverse transcription and polymerase chain reaction (RT-PCR). A closed fracture was made in the midshaft of the right tibia of 5-week-old ICR mice, and fractured sites were harvested prefracture (day 0) and on days 2 and 12. In situ hybridization revealed that transcripts for Shh were not detected on day 0, but they were detected in proliferating callus-forming cells in the periosteum and the surrounding tissue, and in the medullary cavity prior to apparent new cartilage and bone formation. Gli 1 (a signaling mediator for Shh) and bone morphogenetic protein-4 transcripts were colocalized with those for Shh transcripts on day 2. The RT-PCR showed that Shh mRNA was detected in the PCR product from day 2, but not from days 0 and 12. These findings are the first description about the activation of Shh gene in the early postfracture reaction.

Frequent expression of smooth muscle markers in malignant fibrous histiocytoma of bone.

BACKGROUND/AIMS: Malignant fibrous histiocytoma (MFH) of bone, a relatively rare primary malignant bone tumour, is a distinct clinicopathological entity as opposed to MFH derived from soft tissue. Although the true histogenesis of this condition is still controversial, a considerable number of cases of MFH in soft tissue show positive immunohistochemical reactivity for muscle markers such as desmin, common muscle actin (HHF35), and alpha smooth muscle actin (SMA), suggesting that MFH cells are myofibroblastic in nature. METHODS: This study investigated immunoreactivity for several different muscle markers in 19 cases of MFH of bone together with reverse transcription polymerase chain reaction (RT-PCR) analysis on frozen tissue samples that were available in four cases, and compared the data with those found in 11 cases of osteosarcoma and 11 cases of soft tissue MFH treated over the same period. RESULTS: Immunohistochemistry revealed that MFH of bone showed relatively frequent expression of smooth muscle markers, including calponin (nine cases), alpha-SMA (nine cases), and SM22alpha (18 cases), and this was confirmed by RT-PCR analysis. However, only one, two, and three cases of MFH of bone showed positive staining for desmin, MyoD1, and HHF35, respectively. Similarly, 11 osteosarcoma cases were relatively frequently positive for alpha-SMA (five cases), calponin (four cases), and SM22alpha (seven cases), and less frequently positive for desmin (one case), MyoD1 (none), and HHF35 (none). In contrast, very few MFH of soft tissue cases (n = 11) showed positive reactivity for all of these muscle markers. It has recently been reported that human bone marrow stromal cells also express various kinds of smooth muscle markers including alpha-SMA and calponin. CONCLUSIONS: These results suggested that MFH of bone may derive from mesenchymal stromal cells in bone marrow and has a more myofibroblastic differentiation than soft tissue MFH.

Mechanisms of age-related decline in insulin-like growth factor-I dependent proteoglycan synthesis in rat intervertebral disc cells.

STUDY DESIGN: Age-related fluctuations in insulin-like growth factor-I dependent proteoglycan synthesis in rat intervertebral disc cells were investigated. OBJECTIVES: The purpose of this study was to determine whether synthetic responses to insulin-like growth factor-I decline with age and to explore the possibility that an age-related increase in the expression of insulin-like growth factor binding proteins suppresses matrix synthesis in intervertebral disc cells. SUMMARY AND BACKGROUND DATA: Several studies have reported that the responsiveness of chondrocytes to insulin-like growth factor-I decreases with age and furthermore that this phenomenon may be related to increased expression of insulin-like growth factor binding proteins by chondrocytes. MATERIALS AND METHODS: Nucleus pulposus tissue and cells were obtained from the coccygeal vertebrae of 8-week-old, 40-week-old, and 120-week-old rats. Age-related changes in the expression of insulin-like growth factor-I and its receptor were assessed together with insulin-like growth factor-I dependent proteoglycan synthesis by the cultured nucleus pulposus cells. Also, western blot analysis of insulin-like growth factor binding protein-1 was carried out, and further examination was performed of insulin-like growth factor-I signal transduction through tyrosine phosphorylation of insulin receptor substrate-1, which is a signal transducer of insulin-like growth factor-I. RESULTS: Semiquantitative reverse transcription polymerase chain reaction analysis indicated that the expression of insulin-like growth factor-I receptor in 120-week cells decreased clearly in comparison with the cells of younger animals. By contrast, insulin-like growth factor-I dependent proteoglycan synthesis decreased with age, and the sharpest decline of synthesis was found between 8-week and 40-week cells, although the level of insulin-like growth factor-I/insulin-like growth factor-I receptor gene expression was maintained in 40-week-old animals. Consistent with the results of proteoglycan synthesis, the expression of phosphorylated insulin receptor substrate-1 decreased with age. Thus, the expression of insulin-like growth factor binding protein-1 and proteoglycan synthesis was investigated by use of Long R3 insulin-like growth factor-I, which was not influenced by insulin-like growth factor binding proteins. Insulin-like growth factor binding protein-1 was strongly expressed in 40-week cells in comparison with the expression in 8-week cells. Furthermore, proteoglycan synthesis in 40-week cells supplemented with Long R3 insulin-like growth factor-I was upregulated in comparison with that in 40-week cells supplemented with insulin-like growth factor-I. CONCLUSION: The present findings indicate that the age-related decline in insulin-like growth factor-I dependent proteoglycan synthesis in nucleus pulposus is caused, at least in part, by the increase in insulin-like growth factor binding proteins at the early stages of aging, and further suggest that a loss of proteoglycan synthesis during the late stages of aging is caused by the downregulation of insulin-like growth factor-I receptor in addition to an increase in insulin-like growth factor binding proteins.

Immunohistochemical detection of parathyroid hormone-related peptide, Indian hedgehog, and patched in the process of endochondral ossification in the human.

Parathyroid hormone-related peptide (PTHrP), Indian hedgehog (Ihh), and patched (Ptc; a receptor for Ihh) were immunolocalized in tissue undergoing endochondral ossification in the human. PTHrP, Ihh, and Ptc were immunolocalized in prehypertrophic and hypertrophic chondrocytes in mature cartilage matrix. PTHrP and Ptc were immunostained in proliferating chondrocytes and perichondrial cells, whereas Ihh was not. PTHrP, Ihh, and Ptc showed positive immunostaining in osteoblasts in the bone-forming area. In the bone resorption site, PTHrP was immunolocalized in osteoclasts, whereas Ihh and Ptc were not. The present findings indicated that PTHrP, Ihh, and Ptc were associated with the process of endochondral ossification, and suggested the possible involvement of Ihh and PTHrP signaling in the regulation of proliferation and hypertrophy of chondrocytes in human chondrogenesis.

Ossification of the ligamentum flavum associated with osteoblastoma: a report of three cases.

We report three cases of spinal osteoblastoma with ossification of the ligamentum flavum (OLF) adjacent to the tumor. The patients in this report, all young adults, had no symptoms except for back pain. Computed tomography (CT) demonstrated a typical radiolucent nidus in the spinal pedicle/lamina with a dense sclerotic rim. In addition, ectopic bone formation at the insertion point of the ligamentum flavum adjacent to the tumor was clearly illustrated. Magnetic resonance imaging (MRI) revealed the tumor and surrounding inflammatory responses, but OLF was not detected clearly. Histological examination revealed endochondral ossification of the ligamentum flavum that is quite unusual for normal young adults. Immunohistochemical assays in one case demonstrated that bone morphogenetic protein (BMP)-2/4 was expressed in the osteoblastic tumor cells. This case raises the possibility that BMPs secreted from the tumor cells triggered ectopic ossification in the spinal ligament.

Localization and expression of osteopontin in the rotator cuff tendons in patients with calcifying tendinitis.

Calcifying tendinitis of rotator cuff tendons is a common and painful condition caused by ectopic calcification in humans. To examine the involvement of osteopontin (OPN), a potent regulator of calcium deposition on connective tissues, localization and expression of OPN protein and messenger (m)RNA were investigated in human tissue samples of calcified rotator cuff tendons. Immunohistochemistry demonstrated that OPN was localized in cells surrounding the calcified area. OPN was localized in two distinct cell types, i.e., fibroblast-like cells negative for CD68 and tartrate-resistant acid phosphatase (TRAP) and multinucleated macrophages positive for CD68 and TRAP. In situ hybridization revealed that the mRNA expression of OPN in these cells coincided with the immunohistochemistry results, and these results were supported by reverse transcriptase polymerase chain reaction analysis using human OPN-specific oligonucleotides. Cells located away from the calcified area did not express OPN. The present findings indicate the involvement of OPN in the process of calcification of rotator cuff tendons and suggest that OPN plays a role in such painful disorders through the actions of at least two cell types.