Quantification of the whole-body burden of radiographic osteoarthritis using factor analysis

Multiple joint osteoarthritis (MJOA): What's in a name?

OBJECTIVE

To summarize the current state of the literature regarding multi-joint osteoarthritis (MJOA) and discuss important future directions.

DESIGN

A narrative review of the author's work and other key references on this topic with a focus on the Johnston County studies, definitions of MJOA and their impact, multi-site pain in osteoarthritis (OA), genetics and biomarkers in MJOA, and perspectives on future work.

RESULTS

MJOA is variably defined and lacks a clear consensus definition, making comprehensive study challenging. Involvement of both symptoms and structural changes of OA in multiple joints in an individual is common, but patterns vary by sex, race/ethnicity, and other factors. Outcomes (e.g., general health, function, falls, mortality) are negatively impacted by a greater whole-body OA burden. Recent genetic and biomarker studies including whole-body OA assessments have begun to shed some light on potentially unique factors in the MJOA population.

CONCLUSIONS

Consideration of MJOA is essential for ongoing study of OA phenotypes, epidemiology, risk factors, genetics, biomarkers, and outcomes, to fully understand and eventually limit the negative impact of OA burden on health.

P62/SQSTM1 beyond Autophagy: Physiological Role and Therapeutic Applications in Laboratory and Domestic Animals

Inflammation is the preceding condition for the development of mild and severe pathological conditions, including various forms of osteopenia, cancer, metabolic syndromes, neurological disorders, atherosclerosis, cardiovascular, lung diseases, etc., in human and animals. The inflammatory status is induced by multifarious intracellular signaling cascades, where cytokines, chemokines, arachidonic acid metabolites, adhesion molecules, immune cells and other components foster a “slow burn” at a local or systemic level. Assuming that countering inflammation limits the development of inflammation-based diseases, a series of new side-effects-free therapies was assessed in experimental and domestic animals. Within the targets of the drug candidates for quenching inflammation, an archetypal autophagic gear, the p62/sqstm1 protein, has currently earned attention from researchers. Intracellular p62 has been recently coined as a multi-task tool associated with autophagy, bone remodeling, bone marrow integrity, cancer progression, and the maintenance of systemic homeostasis. Accordingly, p62 can act as an effective suppressor of inflamm-aging, reducing oxidative stress and proinflammatory signals. Such an operational schedule renders this protein an effective watchdog for degenerative diseases and cancer development in laboratory and pet animals. This review summarizes the current findings concerning p62 activities as a molecular hub for cell and tissues metabolism and in a variety of inflammatory diseases and other pathological conditions. It also specifically addresses the applications of exogenous p62 (DNA plasmid) as an anti-inflammatory and homeostatic regulator in the treatment of osteoporosis, metabolic syndrome, age-related macular degeneration and cancer in animals, and the possible application of p62 plasmid in other inflammation-associated diseases.

Genome-wide association and functional studies identify a role for matrix Gla protein in osteoarthritis of the hand

OBJECTIVE

Osteoarthritis (OA) is the most common form of arthritis and the leading cause of disability in the elderly. Of all the joints, genetic predisposition is strongest for OA of the hand; however, only few genetic risk loci for hand OA have been identified. Our aim was to identify novel genes associated with hand OA and examine the underlying mechanism.

METHODS

We performed a genome-wide association study of a quantitative measure of hand OA in 12 784 individuals (discovery: 8743, replication: 4011). Genome-wide significant signals were followed up by analysing gene and allele-specific expression in a RNA sequencing dataset (n=96) of human articular cartilage.

RESULTS

We found two significantly associated loci in the discovery set: at chr12 (p=3.5 × 10-10) near the matrix Gla protein (MGP) gene and at chr12 (p=6.1×10-9) near the CCDC91 gene. The DNA variant near the MGP gene was validated in three additional studies, which resulted in a highly significant association between the MGP variant and hand OA (rs4764133, Betameta=0.83, Pmeta=1.8*10-15). This variant is high linkage disequilibrium with a coding variant in MGP, a vitamin K-dependent inhibitor of cartilage calcification. Using RNA sequencing data from human primary cartilage tissue (n=96), we observed that the MGP RNA expression of the hand OA risk allele was significantly lowercompared with the MGP RNA expression of the reference allele (40.7%, p<5*10-16).

CONCLUSIONS

Our results indicate that the association between the MGP variant and increased risk for hand OA is caused by a lower expression of MGP, which may increase the burden of hand OA by decreased inhibition of cartilage calcification.

Establishment of reference intervals for osteoarthritis-related soluble biomarkers: the FNIH/OARSI OA Biomarkers Consortium

OBJECTIVE

To establish reference intervals for osteoarthritis (OA)-related biomarkers used in the Foundation for the National Institutes of Health (FNIH) OA Biomarkers Consortium Project.

METHODS

A total of 129 'multijoint controls' were selected from 2722 African-American and Caucasian men and women in the Johnston County Osteoarthritis Project. The majority (79%) of those eligible (with biospecimens and baseline data) also had one or more follow-up evaluations 5-15 years later. Multijoint controls were selected to be free of radiographic hand, hip, knee and lumbar spine osteoarthritis (OA), to have no knee or hip symptoms, and minimal hand and spine symptoms at all available time points. Eighteen biomarkers were evaluated in serum (s) and/or urine (u) by ELISA. Reference intervals and partitioning by gender and race were performed with EP Evaluator software.

RESULTS

Controls were 64% women, 33% African-Americans, mean age 59 years and mean body mass index 29 kg/m². Three biomarkers were associated with age: sHyaluronan (positively), sN-terminal propeptide of collagen IIA (positively) and sCol2-3/4 C-terminal cleavage product of types I and II collagen (negatively). Exploratory analyses suggested that separate reference intervals may be warranted on the basis of gender for uC-terminal cross-linked telopeptide of type II collagen (uCTXII), sMatrix metalloproteinase-3, uNitrated type II collagen degradation fragment (uCol2-1 NO2) and sHyaluronan, and on the basis of race for uCTXII, sCartilage oligomeric matrix protein, sC-terminal cross-linked telopeptide of type I collagen and uCol2-1 NO2.

CONCLUSIONS

To our knowledge, this represents the best and most stringent control group ever assayed for OA-related biomarkers. These well-phenotyped controls, representing a similar age demographic to that of the OA Initiative-FNIH main study sample, provide a context for interpretation of OA subject biomarker data. The freely available data set also provides a reference for future human studies.

Composite measures of multi-joint symptoms, but not of radiographic osteoarthritis, are associated with functional outcomes: the Johnston County Osteoarthritis Project

PURPOSE

To determine associations between multiple joint symptoms and radiographic osteoarthritis (rOA) and functional outcomes.

METHOD

Complete cross-sectional data for multi-joint symptoms and radiographs, Health Assessment Questionnaire (HAQ) scores, and gait speed were available for 1307 Johnston County Osteoarthritis Project participants (34% men, 32% African American, mean age 66 years). Factor analysis of symptom scores and radiographic grades for the lumbosacral spine, bilateral hands, knees, and hips provided composite scores. Regression models were used to determine associations between composite scores, HAQ, and gait speed, adjusting for age, body mass index, gender, and race.

RESULTS

Five rOA factors were identified: (1) IP/CMC factor (carpometacarpal [CMC] and all interphalangeal [IP] joints); (2) MCP factor (metacarpophalangeal joints 2-5); (3) Knee factor (tibiofemoral and patellofemoral joints); (4) Spine factor (L1/2 to L5/S1); and (5) Symptom factor. After adjustment, only the Symptom composite was significantly associated with HAQ and gait speed; a 1-standard deviation increase in Symptom score was associated with 9 times higher odds of having poorer function on the HAQ (odds ratio 9.32, 95% confidence interval [CI] 6.80, 12.77), and a clinically significant decline in gait speed (0.06 m/s, 95% CI -0.07, -0.05).

CONCLUSIONS

A novel Symptom composite score was associated with poorer functional outcomes.

IMPLICATIONS FOR REHABILITATION

Osteoarthritis (OA) commonly affects multiple joints and is the most common form of arthritis. Symptomatic assessments, which can be easily executed by rehabilitation practitioners, are more closely related to self-reported and performance-based functional status than are less accessible and more costly radiographs. Symptomatic assessments are likely to be more informative for understanding, treating, and potentially preventing functional limitations than radiographic assessments.

Lumbar spine radiographic features and demographic, clinical, and radiographic knee, hip, and hand osteoarthritis

OBJECTIVE

To determine the prevalence of lumbar spine individual radiographic features (IRFs) of disc space narrowing (DSN), osteophytes (OST), and facet joint osteoarthritis (FOA); to describe the frequencies of demographic, clinical, and radiographic knee, hip, and hand osteoarthritis (OA) across lumbar spine IRFs; and to determine factors associated with lumbar spine IRFs.

METHODS

We conducted a cross-sectional study of 840 participants enrolled in the Johnston County Osteoarthritis Project (2003-2004). Sample-based prevalence estimates were generated for each lumbar spine IRF. The associations between lumbar spine IRFs and demographic, clinical, and peripheral joint OA were determined with logistic regression models.

RESULTS

Sample-based prevalence estimates were similar for DSN (57.6%) and FOA (57.9%) but higher for OST (88.1%), with significant differences across race and sex. Hand and knee OA frequencies increased across IRFs, whereas the effect was absent for hip OA. African Americans had lower odds of FOA (adjusted odds ratio [OR(adj) ] 0.45 [95% confidence interval (95% CI) 0.32-0.62]), while there was no racial association with DSN and OST. Low back symptoms were associated with DSN (OR(adj) 1.37 [95% CI 1.04-1.80]) but not OST or FOA. Knee OA was associated with OST (OR(adj) 1.62 [95% CI 1.16-2.27]) and FOA (OR(adj) 1.69 [95% CI 1.15-2.49]) but not DSN. Hand OA was associated with FOA (OR(adj) 1.67 [95% CI 1.20-2.28]) but not with DSN or OST. No associations were found with hip OA.

CONCLUSION

These findings underscore the importance of analyzing lumbar spine IRFs separately as the associations with demographic, clinical, and radiographic knee, hip, and hand OA differ widely.