Synovial fibroblast gene expression is associated with sensory nerve growth and pain in rheumatoid arthritis

It has been presumed that rheumatoid arthritis (RA) joint pain is related to inflammation in the synovium; however, recent studies reveal that pain scores in patients do not correlate with synovial inflammation. We developed a machine-learning approach (graph-based gene expression module identification or GbGMI) to identify an 815-gene expression module associated with pain in synovial biopsy samples from patients with established RA who had limited synovial inflammation at arthroplasty. We then validated this finding in an independent cohort of synovial biopsy samples from patients who had early untreated RA with little inflammation. Single-cell RNA sequencing analyses indicated that most of these 815 genes were most robustly expressed by lining layer synovial fibroblasts. Receptor-ligand interaction analysis predicted cross-talk between human lining layer fibroblasts and human dorsal root ganglion neurons expressing calcitonin gene-related peptide (CGRP+). Both RA synovial fibroblast culture supernatant and netrin-4, which is abundantly expressed by lining fibroblasts and was within the GbGMI-identified pain-associated gene module, increased the branching of pain-sensitive murine CGRP+ dorsal root ganglion neurons in vitro. Imaging of solvent-cleared synovial tissue with little inflammation from humans with RA revealed CGRP+ pain-sensing neurons encasing blood vessels growing into synovial hypertrophic papilla. Together, these findings support a model whereby synovial lining fibroblasts express genes associated with pain that enhance the growth of pain-sensing neurons into regions of synovial hypertrophy in RA.

Computer Vision Analysis of Rheumatoid Arthritis Synovium Reveals Lymphocytic Inflammation Is Associated With Immunoglobulin Skewing in Blood

OBJECTIVE

We sought to develop computer vision methods to quantify aggregates of cells in synovial tissue and compare these with clinical and gene expression parameters.

METHODS

We assembled a computer vision pipeline to quantify five features encompassing synovial cell density and aggregates and compared these with pathologist scores, disease classification, autoantibody status, and RNA expression in a cohort of 156 patients with rheumatoid arthritis (RA) and 149 patients with osteoarthritis (OA).

RESULTS

All five features were associated with pathologist scores of synovial lymphocytic inflammation (P < 0.0001). Three features that related to the cells per unit of tissue were significantly increased in patients with both seronegative and seropositive RA compared with those with OA; on the other hand, aggregate features (number and diameter) were significantly increased in seropositive, but not seronegative, RA compared with OA. Aggregate diameter was associated with the gene expression of immunoglobulin heavy-chain genes in the synovial tissue. Compared with blood, synovial immunoglobulin isotypes were skewed from IGHM and IGHD to IGHG3 and IGHG1. Further, patients with RA with high levels of lymphocytic infiltrates in the synovium demonstrated parallel skewing in their blood with a relative decrease in IGHGM (P < 0.002) and IGHD (P < 0.03) and an increase in class-switched immunoglobulin genes IGHG3 (P < 0.03) and IGHG1 (P < 0.002).

CONCLUSION

High-resolution automated identification and quantification of synovial immune cell aggregates uncovered skewing in the synovium from naïve IGHD and IGHM to memory IGHG3 and IGHG1 and revealed that this process is reflected in the blood of patients with high inflammatory synovium.

Deconstruction of rheumatoid arthritis synovium defines inflammatory subtypes

Rheumatoid arthritis is a prototypical autoimmune disease that causes joint inflammation and destruction1. There is currently no cure for rheumatoid arthritis, and the effectiveness of treatments varies across patients, suggesting an undefined pathogenic diversity1,2. Here, to deconstruct the cell states and pathways that characterize this pathogenic heterogeneity, we profiled the full spectrum of cells in inflamed synovium from patients with rheumatoid arthritis. We used multi-modal single-cell RNA-sequencing and surface protein data coupled with histology of synovial tissue from 79 donors to build single-cell atlas of rheumatoid arthritis synovial tissue that includes more than 314,000 cells. We stratified tissues into six groups, referred to as cell-type abundance phenotypes (CTAPs), each characterized by selectively enriched cell states. These CTAPs demonstrate the diversity of synovial inflammation in rheumatoid arthritis, ranging from samples enriched for T and B cells to those largely lacking lymphocytes. Disease-relevant cell states, cytokines, risk genes, histology and serology metrics are associated with particular CTAPs. CTAPs are dynamic and can predict treatment response, highlighting the clinical utility of classifying rheumatoid arthritis synovial phenotypes. This comprehensive atlas and molecular, tissue-based stratification of rheumatoid arthritis synovial tissue reveal new insights into rheumatoid arthritis pathology and heterogeneity that could inform novel targeted treatments.

Machine Learning Reveals Synovial Fibroblast Genes Associated with Pain Affect Sensory Nerve Growth in Rheumatoid Arthritis

It has been presumed that rheumatoid arthritis (RA) joint pain is related to inflammation in the synovium; however, recent studies reveal that pain scores in patients do not correlate with synovial inflammation. We identified a module of 815 genes associated with pain, using a novel machine learning approach, Graph-based Gene expression Module Identification (GbGMI), in samples from patients with longstanding RA, but limited synovial inflammation at arthroplasty, and validated this finding in an independent cohort of synovial biopsy samples from early, untreated RA patients. Single-cell RNA-seq analyses indicated these genes were most robustly expressed by lining layer fibroblasts and receptor-ligand interaction analysis predicted robust lining layer fibroblast crosstalk with pain sensitive CGRP+ dorsal root ganglion sensory neurons. Netrin-4, which is abundantly expressed by lining fibroblasts and associated with pain, significantly increased the branching of pain-sensitive CGRP+ neurons in vitro . We conclude GbGMI is a useful method for identifying a module of genes that associate with a clinical feature of interest. Using this approach, we find that Netrin-4 is produced by synovial fibroblasts in the absence of inflammation and can enhance the outgrowth of CGRP+ pain sensitive nerve fibers.

One Sentence Summary

Machine Learning reveals synovial fibroblast genes related to pain affect sensory nerve growth in Rheumatoid Arthritis addresses unmet clinical need.

Machine learning identification of thresholds to discriminate osteoarthritis and rheumatoid arthritis synovial inflammation

BACKGROUND

We sought to identify features that distinguish osteoarthritis (OA) and rheumatoid arthritis (RA) hematoxylin and eosin (H&E)-stained synovial tissue samples.

METHODS

We compared fourteen pathologist-scored histology features and computer vision-quantified cell density (147 OA and 60 RA patients) in H&E-stained synovial tissue samples from total knee replacement (TKR) explants. A random forest model was trained using disease state (OA vs RA) as a classifier and histology features and/or computer vision-quantified cell density as inputs.

RESULTS

Synovium from OA patients had increased mast cells and fibrosis (p < 0.001), while synovium from RA patients exhibited increased lymphocytic inflammation, lining hyperplasia, neutrophils, detritus, plasma cells, binucleate plasma cells, sub-lining giant cells, fibrin (all p < 0.001), Russell bodies (p = 0.019), and synovial lining giant cells (p = 0.003). Fourteen pathologist-scored features allowed for discrimination between OA and RA, producing a micro-averaged area under the receiver operating curve (micro-AUC) of 0.85±0.06. This discriminatory ability was comparable to that of computer vision cell density alone (micro-AUC = 0.87±0.04). Combining the pathologist scores with the cell density metric improved the discriminatory power of the model (micro-AUC = 0.92±0.06). The optimal cell density threshold to distinguish OA from RA synovium was 3400 cells/mm2, which yielded a sensitivity of 0.82 and specificity of 0.82.

CONCLUSIONS

H&E-stained images of TKR explant synovium can be correctly classified as OA or RA in 82% of samples. Cell density greater than 3400 cells/mm2 and the presence of mast cells and fibrosis are the most important features for making this distinction.

Dynamic spectrum of ectopic lymphoid B cell activation and hypermutation in the RA synovium characterized by NR4A nuclear receptor expression

Ectopic lymphoid structures (ELS) can develop in rheumatoid arthritis (RA) synovial tissue, but the precise pathways of B cell activation and selection are not well understood. Here, we identify a synovial B cell population characterized by co-expression of a family of orphan nuclear receptors (NR4A1-3), which is highly enriched in RA synovial tissue. A transcriptomic profile of NR4A synovial B cells significantly overlaps with germinal center light zone B cells and an accrual of somatic hypermutation that correlates with loss of naive B cell state. NR4A B cells co-express lymphotoxins α and β and IL-6, supporting functions in ELS promotion. Expanded and shared clones between synovial NR4A B cells and plasma cells and the rapid upregulation with BCR stimulation point to in situ differentiation. Together, we identify a dynamic progression of B cell activation in RA synovial ELS, with NR4A transcription factors having an important role in local adaptive immune responses.

Rheumatoid Arthritis Synovial Inflammation Quantification Using Computer Vision

OBJECTIVE

We quantified inflammatory burden in rheumatoid arthritis (RA) synovial tissue by using computer vision to automate the process of counting individual nuclei in hematoxylin and eosin images.

METHODS

We adapted and applied computer vision algorithms to quantify nuclei density (count of nuclei per unit area of tissue) on synovial tissue from arthroplasty samples. A pathologist validated algorithm results by labeling nuclei in synovial images that were mislabeled or missed by the algorithm. Nuclei density was compared with other measures of RA inflammation such as semiquantitative histology scores, gene-expression data, and clinical measures of disease activity.

RESULTS

The algorithm detected a median of 112,657 (range 8,160-821,717) nuclei per synovial sample. Based on pathologist-validated results, the sensitivity and specificity of the algorithm was 97% and 100%, respectively. The mean nuclei density calculated by the algorithm was significantly higher (P < 0.05) in synovium with increased histology scores for lymphocytic inflammation, plasma cells, and lining hyperplasia. Analysis of RNA sequencing identified 915 significantly differentially expressed genes in correlation with nuclei density (false discovery rate is less than 0.05). Mean nuclei density was significantly higher (P < 0.05) in patients with elevated levels of C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, and cyclized citrullinated protein antibody.

CONCLUSION

Nuclei density is a robust measurement of inflammatory burden in RA and correlates with multiple orthogonal measurements of inflammation.

Defining inflammatory cell states in rheumatoid arthritis joint synovial tissues by integrating single-cell transcriptomics and mass cytometry

To define the cell populations that drive joint inflammation in rheumatoid arthritis (RA), we applied single-cell RNA sequencing (scRNA-seq), mass cytometry, bulk RNA sequencing (RNA-seq) and flow cytometry to T cells, B cells, monocytes, and fibroblasts from 51 samples of synovial tissue from patients with RA or osteoarthritis (OA). Utilizing an integrated strategy based on canonical correlation analysis of 5,265 scRNA-seq profiles, we identified 18 unique cell populations. Combining mass cytometry and transcriptomics revealed cell states expanded in RA synovia: THY1(CD90)+HLA-DRAhi sublining fibroblasts, IL1B+ pro-inflammatory monocytes, ITGAX+TBX21+ autoimmune-associated B cells and PDCD1+ peripheral helper T (TPH) cells and follicular helper T (TFH) cells. We defined distinct subsets of CD8+ T cells characterized by GZMK+, GZMB+, and GNLY+ phenotypes. We mapped inflammatory mediators to their source cell populations; for example, we attributed IL6 expression to THY1+HLA-DRAhi fibroblasts and IL1B production to pro-inflammatory monocytes. These populations are potentially key mediators of RA pathogenesis.

Flares in Patients with Rheumatoid Arthritis after Total Hip and Total Knee Arthroplasty: Rates, Characteristics, and Risk Factors

OBJECTIVE

Rates of total knee arthroplasty (TKA) and total hip arthroplasty (THA) remain high for patients with rheumatoid arthritis (RA), who are at risk of flaring after surgery. We aimed to describe rates, characteristics, and risk factors of RA flare within 6 weeks of THA and TKA.

METHODS

Patients with RA were recruited prior to elective THA and TKA surgery and prospectively followed. Clinicians evaluated RA clinical characteristics 0-2 weeks before and 6 weeks after surgery. Patients answered questions regarding disease activity including self-reported joint counts and flare status weekly for 6 weeks. Per standard of care, biologics were stopped before surgery, while glucocorticoids and methotrexate (MTX) were typically continued. Multivariable logistic regression was used to identify baseline characteristics associated with postsurgical RA flares.

RESULTS

Of 120 patients, the mean age was 62 years and the median RA duration 14.8 years. Ninety-eight (82%) met 2010/1987 American College of Rheumatology/European League Against Rheumatism criteria, 53 (44%) underwent THA (and the rest TKA), and 61 (51%) were taking biologics. By 6 weeks, 75 (63%) had flared. At baseline, flarers had significantly higher disease activity (as measured by the 28-joint Disease Activity Score), erythrocyte sedimentation rate, C-reactive protein, and pain. Numerically more flarers used biologics, but stopping biologics did not predict flares, and continuing MTX was not protective. A higher baseline disease activity predicted flaring by 6 weeks (OR 2.12, p = 0.02).

CONCLUSION

Flares are frequent in patients with RA undergoing arthroplasty. Higher baseline disease activity significantly increases the risk. Although more patients stopping biologics flared, this did not independently predict flaring. The effect of early postsurgery flares requires further study.

The influence of synovial inflammation and hyperplasia on symptomatic outcomes up to 2 years post-operatively in patients undergoing partial meniscectomy

OBJECTIVE

Synovitis is associated with pain and other symptoms in patients with knee osteoarthritis (OA), and in patients with meniscal tears even in the absence of radiographic OA. Patients undergoing arthroscopic partial meniscectomy were followed for 2 years to determine whether synovitis predicts post-operative symptoms.

DESIGN

Thirty-three patients scheduled for arthroscopy were recruited for this pilot study. Symptoms were assessed using a knee pain scale, the Lysholm score, and the short form-12 (SF-12(®)) pre-operatively and at 16 weeks, 1 year and 2 years post-operatively. Synovial inflammation and hyperplasia were graded on surgical biopsies. Linear mixed effects models were tested to determine whether inflammation or hyperplasia is associated with outcome scores over time.

RESULTS

Lysholm scores and SF-12(®) physical component sub-scores were worse pre-operatively in patients with inflammation (Lysholm: 52.42 [95% confidence interval (CI) 42.37, 62.47] vs 72.38 [66.03, 78.72], P < 0.001; SF-12: 36.81 [28.26, 45.37] vs 46.23 [40.14, 52.32], P < 0.05). Up to 2-years post-operatively, patients with inflammation achieved mean scores similar to those without inflammation. As a result, the mean improvement in Lysholm scores was 13.01 [1.48-24.53] points higher than patients without inflammation, P = 0.03. 33% (4/12) of patients with inflammation still had fair to poor Lysholm scores 2 years after surgery compared to 7% (1/15, P=0.14) without inflammation. No association between hyperplasia and symptoms was noted.

CONCLUSIONS

In this pilot study of patients undergoing partial meniscectomy, synovial inflammation was associated with worse pre-operative symptoms, but not with poorer outcomes in the first 2 years post-arthroscopy. Larger cohorts and longer follow-up should be pursued to confirm this relationship, and determine if the initial response is sustained.

Aseptic lymphocyte dominated vasculitis-associated lesion resulting from trunnion corrosion in a cobalt-chrome unipolar hemiarthroplasty

Most of the published descriptions of adverse soft tissue reactions that have been reported in the context of a metal-on-metal articulation have been in cases of total hip arthroplasty or resurfacing arthroplasty. Recently, several case reports have been published describing aseptic lymphocyte dominated vasculitis-associated lesions (ALVAL) in metal-on-polyethylene. To our knowledge, there has not been a description of a similar, aggressive reaction secondary to metal debris from the head-neck junction of a unipolar hemiarthroplasty component. In this case report, we describe a patient with a catastrophic failure of a unipolar hip hemiarthroplasty, secondary to aggressive osteolysis and an inflammatory mediated immunological reaction to metal debris.

Infrared fiber optic probe evaluation of degenerative cartilage correlates to histological grading

BACKGROUND

Osteoarthritis (OA), a degenerative cartilage disease, results in alterations of the chemical and structural properties of tissue. Arthroscopic evaluation of full-depth tissue composition is limited and would require tissue harvesting, which is inappropriate in daily routine. Fourier transform infrared (FT-IR) spectroscopy is a modality based on molecular vibrations of matrix components that can be used in conjunction with fiber optics to acquire quantitative compositional data from the cartilage matrix.

PURPOSE

To develop a model based on infrared spectra of articular cartilage to predict the histological Mankin score as an indicator of tissue quality.

STUDY DESIGN

Comparative laboratory study.

METHODS

Infrared fiber optic probe (IFOP) spectra were collected from nearly normal and more degraded regions of tibial plateau articular cartilage harvested during knee arthroplasty (N = 61). Each region was graded using a modified Mankin score. A multivariate partial least squares algorithm using second-derivative spectra was developed to predict the histological modified Mankin score.

RESULTS

The partial least squares model derived from IFOP spectra predicted the modified Mankin score with a prediction error of approximately 1.4, which resulted in approximately 72% of the Mankin-scored tissues being predicted correctly and 96% being predicted within 1 grade of their true score.

CONCLUSION

These data demonstrate that IFOP spectral parameters correlate with histological tissue grade and can be used to provide information on tissue composition.

CLINICAL RELEVANCE

Infrared fiber optic probe studies have significant potential for the evaluation of cartilage tissue quality without the need for tissue harvest. Combined with arthroscopy, IFOP analysis could facilitate the definition of tissue margins in debridement procedures.

High- and low-dose OPG-Fc cause osteopetrosis-like changes in infant mice

BACKGROUND

Receptor activator of nuclear factor-κB ligand (RANKL) inhibitors are being considered for use in children with osteogenesis imperfecta (OI). We sought to assess efficacy of two doses of a RANKL inhibitor, osteoprotegerin-immunoglobulin Fc segment complex (OPG-Fc), in a growing animal model of OI, the col1α2-deficient mouse (oim/oim) and its wild-type controls (+/+).

METHODS

Treated mice showed runting and radiographic evidence of osteopetrosis with either high- (20 mg/kg twice weekly) or low-dose (1 mg/kg/week) OPG-Fc. Because of this adverse event, OPG-Fc treatment was halted, and the mice were killed or monitored for recovery with monthly radiographs and assessment of serum osteoclast activity (tartrate-resistant acid phosphatase 5b, TRACP-5b) until 25 wk of age.

RESULTS

Twelve weeks of OPG-Fc treatment resulted in radiographic and histologic osteopetrosis with no evidence of bone modeling and negative tartrate-resistant acid phosphatase staining, root dentin abnormalities, and TRACP-5b activity suppression. Signs of recovery appeared 4-8 wk post-treatment.

CONCLUSION

Both high- and low-dose OPG-Fc treatment resulted in osteopetrotic changes in infant mice, an outcome that was not seen in studies with the RANKL inhibitor RANK-immunoglobulin Fc segment complex (RANK-Fc) or in studies with older animals. Further investigations of RANKL inhibitors are necessary before their consideration for use in children.

Comparable outcomes in fracture reduction and bone properties with RANKL inhibition and alendronate treatment in a mouse model of osteogenesis imperfecta

We report a direct comparison of receptor activator of nuclear factor kappa B ligand (RANKL) inhibition (RANK-Fc) with bisphosphonate treatment (alendronate, ALN) from infancy through early adulthood in a mouse model of osteogenesis imperfecta. Both ALN and RANK-Fc decreased fracture incidence to the same degree with increases in metaphyseal bone volume via increased number of thinner trabeculae.

INTRODUCTION

The potential therapeutic benefit of RANKL inhibitors in osteogenesis imperfecta (OI) is under investigation. We report a direct comparison of RANKL inhibition (RANK-Fc) with bisphosphonate treatment (ALN) from infancy through early adulthood in a model of OI, the oim/oim mouse.

METHODS

Two-week-old oim/oim, oim/+, and wildtype (+/+) mice were treated with RANK-Fc 1.5 mg/kg twice per week, ALN 0.21 mg/kg/week or saline (n = 12-20 per group) for 12 weeks.

RESULTS

ALN and RANK-Fc both decreased fracture incidence (9.0 ± 3.0 saline 4.4 ± 2.7 ALN, 4.3 ± 3.0 RANK-Fc fractures per mouse). Serum TRACP-5b activity decreased to 65% after 1 month in all treated mice, but increased sacrifice with RANK-Fc to 130-200% at sacrifice. Metaphyseal density was significantly increased with ALN in +/+ and oim/oim mice (p < 0.05) and tended to increase with RANK-Fc in +/+ mice. No changes in oim/oim femur biomechanical parameters occurred with treatment. Both ALN and RANK-Fc significantly increased trabecular number (3.73 ± 0.77 1/mm for oim/oim saline vs 7.93 ± 0.67 ALN and 7.34 ± 1.38 RANK-Fc) and decreased trabecular thickness (0.045 mm ± 0.003 for oim/oim saline vs 0.034 ± 0.003 ALN and 0.032 ± 0.002 RANK-Fc) and separation in all genotypes (0.28 ± 0.08 mm for oim/oim saline vs 0.12 ± 0.010 ALN and 13 ± 0.03 RANK-Fc)., with significant increase in bone volume fraction (BVF) with ALN, and a trend towards increased BVF in RANK-Fc.

CONCLUSION

Treatment of oim/oim mice with either a bisphosphonate or a RANK-Fc causes similar decreases in fracture incidence with increases in metaphyseal bone volume via increased number of thinner trabeculae.

Synovial inflammation in patients undergoing arthroscopic meniscectomy: molecular characterization and relationship to symptoms

OBJECTIVE

Traumatic and degenerative meniscal tears have different anatomic features and different proposed etiologies, yet both are associated with the development or progression of osteoarthritis (OA). In established OA, synovitis is associated with pain and progression, but a relationship between synovitis and symptoms in isolated meniscal disease has not been reported. Accordingly, we sought to characterize synovial pathology in patients with traumatic meniscal injuries and determine the relationships between inflammation, meniscal and cartilage pathology, and symptoms.

METHODS

Thirty-three patients without evidence of OA who were undergoing arthroscopic meniscectomy for meniscal injuries were recruited. Pain and function were assessed preoperatively; meniscal and cartilage abnormalities were documented at the time of surgery. Inflammation in synovial biopsy specimens was scored, and associations between inflammation and clinical outcomes were determined. Microarray analysis of synovial tissue was performed, and gene expression patterns in patients with and those without inflammation were compared.

RESULTS

Synovial inflammation was present in 43% of the patients and was associated with worse preoperative pain and function scores, independent of age, sex, or cartilage pathology. Microarray analysis and real-time polymerase chain reaction revealed a chemokine signature in synovial biopsy specimens with increased inflammation scores.

CONCLUSION

Our findings indicate that in patients with traumatic meniscal injury undergoing arthroscopic meniscectomy without radiographic evidence of OA, synovial inflammation occurs frequently and is associated with increased pain and dysfunction. Synovia with increased inflammation scores exhibit a unique chemokine signature. Chemokines may contribute to the development of synovial inflammation in patients with meniscal pathology; they also represent potential therapeutic targets for reducing inflammatory symptoms.

Spatial variation in osteonal bone properties relative to tissue and animal age

Little is known about osteonal bone mineral and matrix properties, although these properties are of major importance for the understanding of bone alterations related to age and bone diseases such as osteoporosis. During aging, bone undergoes modifications that compromise their structural integrity as shown clinically by the increase of fracture incidence with age. Based on Fourier transform infrared (FTIR) analysis from baboons between 0 and 32 yr of age, consistent systematic variations in bone properties as a function of tissue age are reported within osteons. The patterns observed were independent of animal age and positively correlated with bone tissue elastic behavior measured by nano-indentation. As long as tissue age is expressed as a percentage of the entire osteon radius, osteonal analyses can be used to characterize disease changes independent of the size of the osteon. These mineral and matrix analyses can be used to explain bone fragility. The mineral content (mineral-to-matrix ratio) was correlated with the animal age in both old (interstitial) and newly formed bone tissue, showing for the first time that age-related changes in BMC can be explain by an alteration in the mineralization process itself and not only by an imbalance in the remodeling process.

PFC knee replacement: osteolytic failures from extreme polyethylene degradation

Despite the long-term success of press-fit condylar (PFC) knee prostheses, premature failures caused by aggressive rapid osteolysis have been reported. To investigate why patients experience such failures, we reviewed 48 retrieved implants and surrounding tissues together with demographic and radiographic data. Polyethylene degradation was determined from density profiles taken through the retrieved inserts. We compared the histology of tissues around PFC implants with that from around failed implants of similar designs from patients matched to length of implantation, body mass index, and age. The pathologic response in PFC patients showed more widespread, dense, sheet-like cellular infiltrate, whereas in the matched patients, the infiltrate was generally scattered discontinuously. The dominant wear mode of the PFC inserts was severe delamination on the articular surfaces. Wear damage was worse with increased length of implantation and was correlated with oxidative degradation and osteolysis. Degradation and osteolysis were more severe with inserts stored longer and sterilized by gamma radiation in air. These results underscore that degradation and increased shelf life lead to osteolysis and loosening. However, they raise questions concerning the cellular reaction to the debris from PFC implants that could lead to a better general understanding of osteolysis.

Suppression of the effector phase of inflammatory arthritis by double-stranded RNA is mediated by type I IFNs

Innate immune receptors that recognize nucleic acids, such as TLRs and RNA helicases, are potent activators of innate immunity that have been implicated in the induction and exacerbation of autoimmunity and inflammatory arthritis. Polyriboinosine-polyribocytidylic acid sodium salt (poly(IC)) is a mimic of dsRNA and viral infection that activates TLR3 and the RNA helicases retinoic acid-induced gene-1 and melanoma differentiation-associated gene-5, and strongly induces type I IFN production. We analyzed the effects of systemic delivery of poly(IC) on the inflammatory effector phase of arthritis using the collagen Ab-induced and KRN TCR-transgenic mouse serum-induced models of immune complex-mediated experimental arthritis. Surprisingly, poly(IC) suppressed arthritis, and suppression was dependent on type I IFNs that inhibited synovial cell proliferation and inflammatory cytokine production. Administration of exogenous type I IFNs was sufficient to suppress arthritis. These results suggest a regulatory role for innate immune receptors for dsRNA in modulating inflammatory arthritis and provide additional support for an anti-inflammatory function of type I IFNs in arthritis that directly contrasts with a pathogenic role in promoting autoimmunity in systemic lupus.

Comparison of mineral quality and quantity in iliac crest biopsies from high- and low-turnover osteoporosis: an FT-IR microspectroscopic investigation

Fourier-transform infrared microspectroscopy (FTIRM) allows analysis of mineral content, mineral crystal maturity and mineral composition at approximately 10-micron spatial resolution. Previous FTIRM analyses comparing 4-micron thick sections from non-decalcified iliac crest biopsies from women with post-menopausal osteoporosis, as contrasted with iliac crest tissue from individuals without evidence of metabolic bone disease, demonstrated significant differences in average mineral content (decreased in osteoporosis) and mineral crystal size/perfection (increased in osteoporosis). More importantly, these parameters, which vary throughout the tissue in relation to the tissue age in healthy bone, showed no such variation in bone biopsies from patients with osteoporosis. The present study compares the spatial and temporal variation in mineral quantity and properties in trabecular bone in high- and low-turnover osteoporosis. Specifically, six biopsies from women (n=5) and one man with high-turnover osteoporosis (age range 39-77) and four women and two men with low turnover osteoporosis (age range 37-63) were compared to ten "normal" biopsies from three men and seven woman (age range: 27-69). "High turnover" was defined as the presence of increased resorptive surface, higher than normal numbers of osteoclasts and greater than or equal to normal osteoblastic activity. "Low turnover" was defined as lower than normal resorptive surface, decreased osteoclast number and less than normal osteoblastic activity. Comparing variations in FTIR-derived values for each of the parameters measured at the surfaces of the trabecular bone to the maximum value observed in multiple trabeculae from each person, the high-turnover samples showed little change in the mineral: matrix ratio, carbonate: amide I ratio, crystallinity and acid phosphate content. The low-turnover samples also showed little change in these parameters, but in contrast to the high-turnover samples, the low-turnover samples showed a slight increase in these parameters, indicative of retarded, but existent resorption and formation. These data indicate that FTIR microspectroscopy can provide quantitative information on mineral changes in osteoporosis that are consistent with proposed mechanisms of bone loss.

Value of power Doppler imaging and the hypoechoic halo in the sonographic detection of foreign bodies: correlation with histopathologic findings

OBJECTIVE

To present the power Doppler findings and evaluate the hypoechoic rim in increasing the conspicuity of foreign bodies detected on sonography and to correlate the sonographic and histopathologic findings.

METHODS

Between 1998 and 2001, all sonographic examinations for evaluation of possible foreign bodies were reviewed retrospectively. Patients who had surgical exploration and pathologic evaluation were included in the study. Gray scale and power Doppler examinations were performed with high-frequency linear array transducers. Histologic evaluation was then correlated with the sonographic findings.

RESULTS

Twenty-five patients were referred for evaluation of possible foreign bodies. Twelve patients underwent surgery and had pathologic correlation. Sonography had sensitivity of 92% for the overall detection of foreign bodies. There were 2 false-positive findings in which discrete foreign bodies were not seen at gross inspection, but inflammation and scar tissue were present at histologic examination. Pathologic findings were thought to represent chronic foreign body reactions. Hypervascularity immediately surrounding the foreign bodies was shown on power Doppler imaging in all cases, correlating with granulation tissue and neovascularity on pathologic examinations. The hypoechoic halo was shown in all but 2 cases and correlated with fibrinous exudate, granulation tissue, and collagenous capsule formation.

CONCLUSIONS

Sonography is an effective and sensitive tool for the detection of soft tissue foreign bodies. The use of power Doppler imaging may aid in detection of possible foreign bodies by increasing the conspicuity of both the hypoechoic halo and the foreign body itself.

Distribution of collagen cross-links in normal human trabecular bone

Infrared imaging analysis of normal human iliac crest biopsy specimens shows a characteristic spatial variation in the nonreducible:reducible collagen cross-links at trabecular surfaces, depending on the surfaces' metabolic status.

INTRODUCTION

Bone is a composite material consisting of mineral, collagen, non-collagenous proteins, and lipids. Bone collagen, mainly type I, provides the scaffold on which mineral is deposited and imparts specific mechanical properties, determined in part by the amount of collagen present, its orientation and fibril diameter, and the distribution of its cross-links.

MATERIALS AND METHODS

In this study, the technique of Fourier transform infrared imaging (FTIRI) was used to determine the ratio of nonreducible:reducible cross-links, in 2- to 4-microm-thick sections from human iliac crest biopsy specimens (N = 14) at trabecular surfaces as a function of surface activity (forming versus resorbing), with an approximately 6.3-mm spatial resolution. The biopsy specimens were obtained from patients devoid of any metabolic bone disease based on histomorphometric and bone densitometric parameters.

RESULTS AND CONCLUSIONS

Distributions of collagen cross-links within the first 50 mm at forming trabecular surfaces demonstrated a progressive increase in the nonreducible:reducible collagen cross-link ratio, unlike in the case of resorbing surfaces, in which the collagen cross-links ratio (as defined for the purposes of the present report) was relatively constant.

Clinical and pathologic findings in hemochromatosis hip arthropathy

During a 9-year period, 15 patients with hemochromatosis hip arthropathy required 19 total hip arthroplasties for disabling hip pain. Preoperative presentation, hip function, pathologic evaluation of the femoral head, and radiographic findings were reviewed. Postoperative followup averaging 5.7 years (range, 2-11 years) was performed to assess hip pain and function after total hip arthroplasty. The average preoperative Hospital for Special Surgery hip score was 15 points (range, 4-24 points), and this improved to 30 points (range, 4-38 points) after total hip arthroplasty. Only one of 15 patients required revision surgery at 10 years for acetabular loosening. All other patients were pain free, with improved function at latest followup. Histologic evaluation of the resected femoral heads revealed evidence of primary or secondary osteonecrosis in seven of 19 (37%) specimens. Articular cartilage avulsion at the level of the tidemark was identified in eight of 19 (42%) specimens, and calcium pyrophosphate deposition was identified in five of 19 (26%) specimens. These pathologic findings suggest a predictable progression of the arthritic process in patients with hemochromatosis.

FTIR microspectroscopic analysis of normal human cortical and trabecular bone

Fourier transform infrared microspectroscopy (FTIRM) has been used to study the changes in mineral and matrix content and composition in replicate biopsies of nonosteoporotic human cortical and trabecular bone. Changes in osteonal bone in these same samples were reported previously. Spectral maps along and across the lamellae were obtained from iliac crest biopsies of two necropsy cases. Mineral:matrix ratios, calculated from the integrated areas of the phosphate nu1, nu3 band at 900-1200 cm-1 and the amide I band at approximately 1585-1725 cm-1, respectively, were relatively constant in both directions of analysis, i.e., along and across the lamellae. Analysis of the components of the nu1, nu3 phosphate band with a combination of second-derivative spectroscopy and curve fitting revealed the presence of 11 major underlying moieties. Of these, the ratio of the relative areas of the two underlying bands at approximately 1020 and approximately 1030 cm-1 has been shown to be a sensitive index of variation in crystal perfection in both human osteonal bone and in synthetic, poorly crystalline apatites. This ratio was calculated in both cortical and trabecular bone from human iliac crest biopsies along and across the lamellae. The ratio decreased, going from the periosteum to the medullary cavity in the cortical bone, and from the periphery towards the center of trabeculae. These observations were consistent within serial sections obtained from the same biopsy, multiple biopsies obtained from the same necropsy specimen, and biopsies obtained from the two different necropsy specimens. The results presented here along with previously reported changes in osteonal bone show a relation between bone age and "crystallinity/maturity" (a parameter dependent on crystallite size, hydroxyapatite-like stoichiometry, abundance of substituting ions such as CO32-; the more crystalline/mature, the more hydroxyapatite-like stoichiometry, the bigger the crystallite size, the less the ion substitution by ions such as CO32-) as deduced by the 1020/1030 cm-1 ratio. Invariably, younger normal bone is less mature/crystalline than older. These results provide a "baseline" for description of mineral properties, to which diseased bones may be compared.

FTIR microspectroscopic analysis of human iliac crest biopsies from untreated osteoporotic bone

Historically, osteoporosis has been defined as a disease in which there is "too little bone, but what there is, is normal." As a result of research design and sample selection limitations, published data contradict and confirm the historical definition. Because of these limitations, it has been hard to assess the contribution of mineral quality to mechanical properties, and to select therapeutic protocols that optimize bone mineral properties. The coupling of an optical microscope to an infrared spectrometer enables the acquisition of spectral data at known sites in a histologic section of mineralized tissue without loss of topography and/or orientation. The use of second-derivative spectroscopy coupled with curve-fitting techniques allows the qualitative and quantitative assessment of mineral quality (crystallite size and perfection, mineral:matrix ratio) at well-defined morphologic locations. We have previously applied these techniques to the study of normal human osteonal, cortical, and trabecular bone. The results indicated that the newly deposited bone mineral is less "crystalline/mature" than the older one. In the present study, Fourier transform infrared microspectroscopy (FTIRM) was applied to the study of human osteonal and cortical bone from iliac crest biopsies of untreated osteoporotic patients. The hypothesis tested was that osteoporotic bone mineral is monotonically different in its properties expressed as "crystallinity/maturity" than the normal. The results indicate significant differences in the mineral properties as expressed by crystal size and perfection, with the mineral from osteoporotic bone being more crystalline/mature than the normal.

FTIR microspectroscopic analysis of human osteonal bone

Fourier Transform Infrared Microspectroscopy (FTIRM) has been used to study the changes in mineral and matrix content and composition in replicate biopsies of nonosteoporotic human osteonal bone. Spectral maps in four orthogonal directions (in 10 microm steps) from the centers towards the peripheries of individual osteons were obtained from iliac crest biopsies of two necropsy cases. Mineral to matrix ratios, calculated from the ratio of integrated areas of the phosphate nu1,nu3 band at 900-1200 cm-1 to the amide I band at 1585-1725 cm-1, increased from the center to the periphery of the osteon. The total carbonate (based on the nu2 band at approximately 850-900 cm-1) to phosphate nu1,nu3 ratio decreased as the mineral to matrix ratio increased. Analysis of the nu2 CO32- band with a combination of second-derivative spectroscopy and curve fitting revealed a decrease in "labile" carbonate, a slight decrease in Type A and a slight increase in Type B carbonate from the center to the periphery of the osteon. Similar analysis of the components of the nu1,nu3 phosphate band with a combination of second-derivative spectroscopy and curve fitting revealed the presence of 11 major underlying moieties. These components were assigned by comparison with published frequencies for apatite and acid-phosphate containing calcium phosphates. The most consistent variations were alterations in the relative percent areas of bands at approximately 1020 and approximately 1030 cm-1, which had previously been assigned to nonstoichiometric and stoichiometric apatites, respectively. This ratio was used as an index of variation in crystal perfection throughout the osteon. This ratio decreased as the mineral to matrix ratio increased. The reproducibility of these parameters at multiple sites in multiple biopsies suggests their applicability for the analysis of mineral changes in disease.

Anatomy of the Achilles tendon and plantar fascia in relation to the calcaneus in various age groups

Ten adult cadaver feet, three neonatal feet, and the feet of two fetuses were dissected to investigate whether an anatomical continuity exists between the fibers of the Achilles tendon and the plantar fascia. Histologic sections of the feet were done in three age groups: neonate, persons in their mid-20s, and the elderly. As the foot ages, there appears to be continued diminution of the number of fibers connecting the Achilles tendon and plantar fascia. The neonate has a thick continuation of fibers, while the middle-aged foot has only superficial periosteal fibers that continue from tendon to fascia. The elderly feet show simply an insertion of fibers of both structures into the calcaneus with periosteum in between.

Spindle cell lipoma of the foot: a case report and literature review

Lipomas are among the most commonly encountered soft tissue tumors in clinical practice, though they are rare in the foot. Although a presumptive diagnosis is typically made clinically, those tumors with atypical clinical features may require radiological consultation. Difficulty arises when radiographic features are not typical of lipoma. We present a fatty soft tissue tumor of the foot with nonadipose elements on magnetic resonance imaging evaluation. Differentiation of lipoma variants (e.g., spindle cell lipoma, atypical lipoma, pleomorphic lipoma, lipoblastoma, angiolipoma) from liposarcoma based on imaging features is not possible, necessitating surgical resection for definitive histological diagnosis.

The effect of gallium nitrate on healing of vitamin D- and phosphate-deficient rickets in the immature rat

The effect of gallium on rapid in vivo mineralization was studied in a rachitic rat model in which rickets were induced in immature rats then reversed ("healed") with repletion of vitamin D and phosphate. Gallium was administered to selected groups of animals before and during the healing phase. In nonrachitic animals and rachitic animals before healing, the mineral content of diaphyseal and metaphyseal bone was increased, and the crystal size was decreased in those animals that received gallium compared with those that did not. Mineralization of the undermineralized osteoid appeared histologically normal by 72 hours in all animals. However, animals that received gallium both before and during the healing phase had less well-mineralized bones at 18 hours, and by 72 hours, they had lesser increases in osteocalcin and mineral content, which was associated with smaller crystal sizes, than did any animal that did not receive gallium at any time. Prior to the healing phase, the ratio of gallium to hydroxyproline in the metaphyses of rachitic animals was similar to that in nonrachitic animals. Likewise, this ratio did not change in the animals receiving gallium both before and during the healing phase. The ratio of gallium to calcium was higher in rachitic animals compared with controls, and this ratio lowered significantly by the end of the healing phase. Results may be explained in part by direct effect of gallium on the physical process of mineral formation during the rapid healing phase as well as by effects of gallium on osteoblasts and osteoclasts during the induction of rickets.

Anatomy, histology, and vascularity of the glenoid labrum. An anatomical study

We studied the gross, histological, and vascular anatomy of the glenoid labrum in twenty-three fresh-frozen shoulders from cadavera to demonstrate its cross-sectional anatomy, its microvascularity, and its attachments. The superior and anterosuperior portions of the labrum are loosely attached to the glenoid, and the macro-anatomy of those portions is similar to that of the meniscus of the knee. The superior portion of the labrum also consistently inserts directly into the biceps tendon, while its inferior portion is firmly attached to the glenoid rim and appears as a fibrous, immobile extension of the articular cartilage. The arteries supplying the periphery of the glenoid labrum come from the suprascapular, circumflex scapular, and posterior circumflex humeral arteries. In general, the superior and anterosuperior parts of the labrum have less vascularity than do the posterosuperior and inferior parts, and the vascularity is limited to the periphery of the labrum. Vessels supplying the labrum originate from either capsular or periosteal vessels and not from the underlying bone.

Cervical myelopathy due to calcium pyrophosphate dihydrate deposition disease

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FT-IR microscopy of endochondral ossification at 20 mu spatial resolution

A Fourier transform infrared spectrometer has been coupled with an optical microscope to study the distribution and characteristics of the mineral phase in calcifying tissues at 20 mu spatial resolution. This represents the first biophysical application of this technique. High quality spectra were obtained in a relatively short scan time (1-2 minutes) from thin longitudinal sections of normal and rachitic rat femurs. Substantial spatial variations in the extent and structure of the mineral phase were observed as a function of spatial position both within and beyond the growth plates, as judged by the phosphate vibrations in the 900-1200 cm-1 spectral region. The current experiments reveal the utility of FT-IR microscopy in identification of sites where mineralization has occurred. In addition to vibrations from the inorganic components, the Amide I and Amide II motions of the protein constituents are readily observed and may be useful as a probe of protein/mineral interactions.