Effects of low-intensity exercise on spontaneously developed knee osteoarthritis in male senescence-accelerated mouse prone 8

BACKGROUND

Osteoarthritis (OA) is a degenerative joint disease associated with aging, which often leads to joint stiffness and disability. Exercise is one of the most important non-pharmacological treatments and is prescribed as an indispensable treatment for OA. However, whether physical exercise is beneficial for preventing the progression of OA symptoms with age is poorly understood. We investigated the effects of exercise on spontaneously developed knee OA using male senescence-accelerated mouse prone 8 (SAMP8).

METHODS

To examine age-related changes in the knee joints of SAMP8, knee articular cartilage changes, synovitis, knee joint flexion and extension angles, swelling, walking ability, and quadriceps muscle atrophy were analyzed at 3, 5, 7, and 9 months. SAMP8 were required to run at a speed of 10 m/min for 15 min/day from 7 to 9 months of age. The knee joint pathologies and symptoms of exercising and non-exercising mice were compared by histological, immunohistochemical, and morphometrical analyses.

RESULTS

The mice presented with various histological changes, including cartilage destruction, osteocyte formation, synovitis, declined joint angles, and swelling. Notably, medial and posterior cartilage destruction was more severe than that of the lateral and anterior cartilage. Knee joint angles were significantly correlated with the histological scores (modified Mankin and OARSI, osteophyte formation and synovial lining cell layer). Exercise did not attenuate cartilage degeneration in the medial and posterior tibial plateau, although the articular cartilage of the anterior and lateral tibial plateau and its histological scores was remained and significantly improved, respectively, by exercise. Exercise suppressed the age-related decline of collagen type II-positive areas in the remaining articular cartilage and improved the OA symptoms. Exercise reduced the expression of monocyte chemoattractant protein (MCP)-1 and tumor necrosis factor (TNF)-α positive macrophages in the synovium.

CONCLUSION

This study revealed that SAMP8 developed spontaneous knee OA with age, which resembled the disease symptoms in humans. Low-intensity exercise temporarily alleviated degeneration of the remaining cartilage, synovitis, and age-related decreases in knee flexion angle, stride length, and muscle atrophy in SAMP8. However, exercise during OA progression with age may cause mechanical stress that could be both beneficial and detrimental to joint health.

Wheel Running Exacerbates Joint Damage after Meniscal Injury in Mice, but Does Not Alter Gait or Physical Activity Levels

PURPOSE

Exercise and physical activity are recommended to reduce pain and improve joint function in patients with knee osteoarthritis (OA). However, exercise has dose effects, with excessive exercise accelerating OA development and sedentary behaviors also promoting OA development. Prior work evaluating exercise in preclinical models has typically used prescribed exercise regimens; however, in-cage voluntary wheel running creates opportunities to evaluate how OA progression affects self-selected physical activity levels. This study aimed to evaluate how voluntary wheel running after a surgically induced meniscal injury affects gait characteristics and joint remodeling in C57Bl/6 mice. We hypothesize that injured mice will reduce physical activity levels as OA develops after meniscal injury and will engage in wheel running to a lesser extent than the uninjured animals.

METHODS

Seventy-two C57Bl/6 mice were divided into experimental groups based on sex, lifestyle (physically active vs sedentary), and surgery (meniscal injury or sham control). Voluntary wheel running data were continuously collected throughout the study, and gait data were collected at 3, 7, 11, and 15 wk after surgery. At end point, joints were processed for histology to assess cartilage damage.

RESULTS

After meniscal injury, physically active mice showed more severe joint damage relative to sedentary mice. Nevertheless, injured mice engaged in voluntary wheel running at the same rates and distances as mice with sham surgery. In addition, physically active mice and sedentary mice both developed a limp as meniscal injury progressed, yet exercise did not further exacerbate gait changes in the physically active mice, despite worsened joint damage.

CONCLUSIONS

Taken together, these data indicate a discordance between structural joint damage and joint function. Although wheel running after meniscal injury did worsen OA-related joint damage, physical activity did not necessarily inhibit or worsen OA-related joint dysfunction or pain in mice.

Low-level cyclic tibial compression attenuates early osteoarthritis progression after joint injury in mice

OBJECTIVE

Mechanical loading and joint health have a unique relationship in osteoarthritis (OA) onset and progression. Although high load levels adversely affect cartilage health, exercise that involves low to moderate load levels can alleviate OA symptoms. We sought to isolate the beneficial effects of mechanical loading using controlled in vivo cyclic tibial compression. We hypothesized that low-level cyclic compression would attenuate post-traumatic OA symptoms induced by destabilization of the medial meniscus (DMM).

METHODS

10-week-old C57Bl/6J male mice underwent DMM surgery (n = 51). After a 5-day post-operative recovery period, we applied daily cyclic tibial compression to the operated limbs at low (1.0N or 2.0N) or moderate (4.5N) magnitudes for 2 or 6 weeks. At the completion of loading, we compared cartilage and peri-articular bone features of mice that underwent DMM and loading to mice that only underwent DMM.

RESULTS

Compared to DMM alone, low-level cyclic compression for 6 weeks attenuated DMM-induced cartilage degradation (OARSI score, P = 0.008, 95% confidence interval (CI): 0.093 to 0.949). Low-level loading attenuated DMM-induced osteophyte formation after 2 weeks (osteophyte size, P = 0.033, 95% CI: 3.27-114.45 μm), and moderate loading attenuated subchondral bone sclerosis after 6 weeks (tissue mineral density (TMD), P = 0.011, 95% CI: 6.32-70.60 mg HA/ccm) compared to limbs that only underwent DMM. Finally, loading had subtle beneficial effects on cartilage cellularity and aggrecanase activity after DMM.

CONCLUSION

Low-level cyclic compression is beneficial to joint health after an injury. Therefore, the progression of early OA may be attenuated by applying well controlled, low-level loading shortly following joint trauma.

Impairment-Based Rehabilitation With Patterned Electrical Neuromuscular Stimulation and Lower Extremity Function in Individuals With Patellofemoral Pain: A Preliminary Study

CONTEXT

Patellofemoral pain (PFP) is a chronic condition that presents with lower extremity muscle weakness, decreased flexibility, subjective functional limitations, pain, and decreased physical activity. Patterned electrical neuromuscular stimulation (PENS) has been shown to affect muscle activation and pain after a single treatment, but its use has not been studied in a rehabilitation trial.

OBJECTIVE

To determine the effects of a 4-week impairment-based rehabilitation program using PENS on subjective function, pain, strength, range of motion, and physical activity in individuals with PFP.

DESIGN

Randomized controlled trial.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 21 patients with PFP (5 males, 16 females; age = 23.4 ± 7.6 years, height = 168.0 ± 7.5 cm, mass = 69.0 ± 19.5 kg).

INTERVENTION(S)

Participants completed a 4-week supervised rehabilitation program in conjunction with random assignment to receive PENS or sham treatments.

MAIN OUTCOME MEASURE(S)

Subjective function, pain, strength, range of motion, and physical activity levels were assessed prerehabilitation and postrehabilitation. Subjective function and pain were also assessed at 6 and 12 months postrehabilitation. Repeated-measures analyses of variance and Tukey post hoc testing were conducted with α ≤ .05. We calculated Cohen d effect sizes with 95% confidence intervals.

RESULTS

Both groups had statistically and clinically meaningful differences in subjective function, pain, strength, range of motion, and activity level after 4 weeks of impairment-based rehabilitation. Improved subjective function was observed in both groups at 6 and 12 months after the interventions. The PENS group had improvements in current pain for all 3 postrehabilitation times compared with baseline measures.

CONCLUSIONS

An impairment-based intervention effectively improved subjective function, pain, strength, range of motion, and physical activity levels in individuals with PFP. Participants who received PENS in addition to the rehabilitation program had improved current pain at 6 and 12 months postrehabilitation compared with baseline scores.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02441712.

Collagen XI mutation lowers susceptibility to load-induced cartilage damage in mice

Interactions among risk factors for osteoarthritis (OA) are not well understood. We investigated the combined impact of two prevalent risk factors: mechanical loading and genetically abnormal cartilage tissue properties. We used cyclic tibial compression to simulate mechanical loading in the cho/+ (Col11a1 haploinsufficient) mouse, which has abnormal collagen fibrils in cartilage due to a point mutation in the Col11a1 gene. We hypothesized that the mutant collagen would not alter phenotypic bone properties and that cho/+ mice, which develop early onset OA, would develop enhanced load-induced cartilage damage compared to their littermates. To test our hypotheses, we applied cyclic compression to the left tibiae of 6-month-old cho/+ male mice and wild-type (WT) littermates for 1, 2, and 6 weeks at moderate (4.5 N) and high (9.0 N) peak load magnitudes. We then characterized load-induced cartilage and bone changes by histology, microcomputed tomography, and immunohistochemistry. Prior to loading, cho/+ mice had less dense, thinner cortical bone compared to WT littermates. In addition, in loaded and non-loaded limbs, cho/+ mice had thicker cartilage. With high loads, cho/+ mice experienced less load-induced cartilage damage at all time points and displayed decreased matrix metalloproteinase (MMP)-13 levels compared to WT littermates. The thinner, less dense cortical bone and thicker cartilage were unexpected and may have contributed to the reduced severity of load-induced cartilage damage in cho/+ mice. Furthermore, the spontaneous proteoglycan loss resulting from the mutant collagen XI was not additive to cartilage damage from mechanical loading, suggesting that these risk factors act through independent pathways. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:711-720, 2018.

Acute Ankle Sprain in a Mouse Model: Changes in Knee-Joint Space

CONTEXT

  Ankle sprains remain the most common orthopaedic injury. Conducting long-term studies in humans is difficult and costly, so the long-term consequences of an ankle sprain are not entirely known.

OBJECTIVE

  To measure knee-joint space after a single surgically induced ankle sprain in mice.

DESIGN

  Randomized controlled trial.

SETTING

  University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Thirty male mice (CBA/2J) were randomly placed into 1 of 3 surgical groups: the transected calcaneofibular ligament (CFL) group, the transected anterior talofibular ligament/CFL group, or a sham treatment group. The right ankle was operated on in all mice.

MAIN OUTCOME MEASURE(S)

  Three days after surgery, all of the mice were individually housed in cages containing a solid-surface running wheel, and daily running-wheel measurements were recorded. Before surgery and every 6 weeks after surgery, a diagnostic ultrasound was used to measure medial and lateral knee-joint space in both hind limbs.

RESULTS

  Right medial (P = .003), right lateral (P = .002), left medial (P = .03), and left lateral (P = .002) knee-joint spaces decreased across the life span. The mice in the anterior talofibular ligament/CFL group had decreased right medial (P = .004) joint space compared with the sham and CFL groups starting at 24 weeks of age and continuing throughout the life span. No differences occurred in contralateral knee-joint degeneration among any of the groups.

CONCLUSIONS

  Based on current data, mice that sustained a surgically induced severe ankle sprain developed greater joint degeneration in the ipsilateral knee. Knee degeneration could result from accommodation to the laxity of the ankle or biomechanical alterations secondary to ankle instability. A single surgically induced ankle sprain could significantly affect knee-joint function.

Using mouse models to investigate the pathophysiology, treatment, and prevention of post-traumatic osteoarthritis

Post-traumatic osteoarthritis (PTOA) is defined by its development after joint injury. Factors contributing to the risk of PTOA occurring, the rate of progression, and degree of associated disability in any individual, remain incompletely understood. What constitutes an "OA-inducing injury" is not defined. In line with advances in the traumatic brain injury field, we propose the scope of PTOA-inducing injuries be expanded to include not only those causing immediate structural damage and instability (Type I), but also those without initial instability/damage from moderate (Type II) or minor (Type III) loading severity. A review of the literature revealed this full spectrum of potential PTOA subtypes can be modeled in mice, with 27 Type I, 6 Type II, and 4 Type III models identified. Despite limitations due to cartilage anatomy, joint size, and bio-fluid availability, mice offer advantages as preclinical models to study PTOA, particularly genetically modified strains. Histopathology was the most common disease outcome, cartilage more frequently studied than bone or synovium, and meniscus and ligaments rarely evaluated. Other methods used to examine PTOA included gene expression, protein analysis, and imaging. Despite the major issues reported by patients being pain and biomechanical dysfunction, these were the least commonly measured outcomes in mouse models. Informative correlations of simultaneously measured disease outcomes in individual animals, was rarely done in any mouse PTOA model. This review has identified knowledge gaps that need to be addressed to increase understanding and improve prevention and management of PTOA. Preclinical mouse models play a critical role in these endeavors. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:424-439, 2017.

Mouse Models of Frailty: an Emerging Field

Frailty is highly prevalent in the elderly, increasing the risk of poor outcomes that include falls, incident disability, hospitalization, and mortality. Thus, a great need exists to characterize the underlying mechanisms and ultimately identify strategies that prevent, delay, and even reverse frailty. Mouse models can provide insight into molecular mechanisms of frailty by reducing variability in lifestyle and genetic factors that can complicate interpretation of human clinical data. Frailty, generally recognized as a syndrome involving reduced homeostatic reserve in response to physiologic challenges and increasing susceptibility to poor health outcomes, is predominantly assessed using two independent strategies, integrated phenotype and deficit accumulation. The integrated phenotype defines frailty by the presentation of factors affecting functional capacity such as weight loss, exhaustion, low activity levels, slow gait, and grip strength. The deficit accumulation paradigm draws parameters from a greater range of physiological systems, such as the ability to perform daily activities, coordination and gait, mental components, physiological problems, and history and presence of medical morbidities. This strategic division also applies within the emerging field of mouse frailty models, with both methodologies showing usefulness in providing insight into physiologic mechanisms and testing interventions. Our review will explore the strategies used, caveats in methodology, and future directions in the application of animal models for the study of the frailty syndrome.

Physical Activity Levels in College Students With Chronic Ankle Instability

CONTEXT

Ankle sprains are the most common orthopaedic pathologic condition, and more concerning is the high percentage of persons who develop chronic ankle instability (CAI). Researchers have reported that patients with CAI are restricted occupationally, have more functional limitations, and have a poorer health-related quality of life. We do not know if these limitations decrease physical activity levels.

OBJECTIVE

To assess total weekly steps taken between persons with CAI and persons with healthy ankles.

DESIGN

Case-control study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 20 participants with unilateral CAI (9 men, 11 women; age = 21.2 ± 1.9 years, height = 174.3 ± 6.9 cm, mass = 71.9 ± 11.7 kg) and 20 healthy participants (9 men, 11 women; age = 20.4 ± 2.1 years, height = 172.1 ± 5.5 cm, mass = 73.1 ± 13.4 kg) volunteered.

MAIN OUTCOME MEASURE(S)

We provided all participants with a pedometer and instructed them to wear it every day for 7 days and to complete a daily step log. They also completed the Foot and Ankle Ability Measure (FAAM), the FAAM Sport version, and the International Physical Activity Questionnaire. A 2-way analysis of variance (group × sex) was used to determine if differences existed in the total number of weekly steps, ankle laxity, and answers on the International Physical Activity Questionnaire between groups and between sexes.

RESULTS

We found no group × sex interaction for step count (F range = 0.439-2.108, P = .08). A main effect for group was observed (F(1,38) = 10.45, P = .04). The CAI group took fewer steps than the healthy group (P = .04). The average daily step count was 6694.47 ± 1603.35 for the CAI group and 8831.01 ± 1290.01 for the healthy group. The CAI group also scored lower on the FAAM (P = .01) and the FAAM Sport version (P = .01).

CONCLUSIONS

The decreased step count that the participants with CAI demonstrated is concerning. This decreased physical activity may be secondary to the functional limitations reported. If this decrease in physical activity level continues for an extended period, CAI may potentially be a substantial health risk if not treated appropriately.

The beneficial effects of exercise on cartilage are lost in mice with reduced levels of ECSOD in tissues

Osteoarthritis (OA) is associated with increased mechanical damage to joint cartilage. We have previously found that extracellular superoxide dismutase (ECSOD) is decreased in OA joint fluid and cartilage, suggesting oxidant damage may play a role in OA. We explored the effect of forced running as a surrogate for mechanical damage in a transgenic mouse with reduced ECSOD tissue binding. Transgenic mice heterozygous (Het) for the human ECSOD R213G polymorphism and 129-SvEv (wild-type, WT) mice were exposed to forced running on a treadmill for 45 min/day, 5 days/wk, over 8 wk. At the end of the running protocol, knee joint tissue was obtained for histology, immunohistochemistry, and protein analysis. Sedentary Het and WT mice were maintained for comparison. Whole tibias were studied for bone morphometry, finite element analysis, and mechanical testing. Forced running improved joint histology in WT mice. However, when ECSOD levels were reduced, this beneficial effect with running was lost. Het ECSOD runner mice had significantly worse histology scores compared with WT runner mice. Runner mice for both strains had increased bone strength in response to the running protocol, while Het mice showed evidence of a less robust bone structure in both runners and untrained mice. Reduced levels of ECSOD in cartilage produced joint damage when joints were stressed by forced running. The bone tissues responded to increased loading with hypertrophy, regardless of mouse strain. We conclude that ECSOD plays an important role in protecting cartilage from damage caused by mechanical loading.