Hypertension is a common comorbidity of osteoarthritis (OA) with known autonomic dysregulation; thus, the autonomic nervous system may provide a shared underlying mechanism. The objective of this ...study was to examine the role of the autonomic nervous system in a preclinical model of OA and hypertension.
Experiments were conducted in spontaneously hypertensive rats and a normotensive control strain, including male and female rats. OA was surgically induced via medial meniscus transection with skin incision used as a sham control (n = 7-8/strain/sex/surgery). Tactile sensitivity, anxiety-related behavior, and serum corticosterone were measured at baseline then bi-weekly across 8 weeks. At weeks 9-10, cardiovascular responses to a chemical vagal nerve agonist were determined to indirectly evaluate vagus nerve function. The joint structure was assessed via grading of histological sections.
In males, OA resulted in thinner cartilage in both hypertensive (OA vs. non-OA p < 0.001) and normotensive (OA vs. non-OA p < 0.001). Only females with comorbid hypertension and OA displayed thinner cartilage (p = 0.013). Male hypertensive OA animals had increased calcified subchondral bone compared to normotensive OA animals (p = 0.043) while female hypertensive OA animals had increased calcified subchondral bone compared to hypertensive sham animals (p < 0.001). All MCLT+MMT groups developed low-grade synovitis; interestingly, hypertensive OA females had higher synovitis scores than normotensive OA females (p = 0.046). Additionally, hypertension led to larger drops in blood pressure with vagal activation in both OA (hypertensive vs. normotensive p = 0.018) and sham (hypertensive vs. normotensive p < 0.001) male animals. In females, this trend held true only in OA animals (normotensive vs. hypertensive p = 0.005).
These data provide preliminary evidence that hypertension influences OA progression and encourages further study into the autonomic nervous system as a possible mechanism.
Intra-articular injections are the most direct route for administering osteoarthritis (OA) therapies, yet how drug carriers distribute within the joint remains understudied. To this end, we developed ...a magnetic composite nanoparticle that can be tracked with fluorescence in vivo via an in vivo imaging system (IVIS), and quantified ex vivo via electron paramagnetic resonance (EPR) spectroscopy. Using this particle, the effects of age and OA pathogenesis on particle clearance and distribution were evaluated in the medial meniscus transection model of OA (5-, 10-, and 15-month old male Lewis rats). At 9 weeks after meniscus transection, composite nanoparticles were injected and joint clearance was assessed via IVIS. At 2 weeks after injection, animals were euthanized and particle distribution was quantified ex vivo via EPR spectroscopy. IVIS and EPR spectroscopy data indicate a predominant amount of particles remained in the joint after 14 days. EPR spectroscopy data suggests particles cleared more slowly from OA knees than from the contralateral control, with particles clearing more slowly from 15-month old rats than from 5- and 10-month old rats. This study demonstrates the importance of including both age and OA as factors when evaluating nanoparticles for intra-articular drug delivery.
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•Electron paramagnetic resonance spectroscopy can sensitively assess biodistribution.•Particles clear more slowly from OA knees compared to contralateral controls.•Intra-articular particle retention is increased in older animals.
In oxygenic photosynthesis, light-driven oxidation of water to molecular oxygen is carried out by the oxygen-evolving complex (OEC) in photosystem II (PS II). Recently, we reported the ...roomtemperature structures of PS II in the four (semi)stable S-states, S₁, S₂, S₃, and S₀, showing that a water molecule is inserted during the S₂ → S₃ transition, as a new bridging O(H)-ligand between Mn1 and Ca. To understand the sequence of events leading to the formation of this last stable intermediate state before O₂ formation, we recorded diffraction and Mn X-ray emission spectroscopy (XES) data at several time points during the S₂ → S₃ transition. At the electron acceptor site, changes due to the two-electron redox chemistry at the quinones, QA and QB, are observed. At the donor site, tyrosine YZ and His190 H-bonded to it move by 50 μs after the second flash, and Glu189 moves away from Ca. This is followed by Mn1 and Mn4 moving apart, and the insertion of OX(H) at the open coordination site of Mn1. This water, possibly a ligand of Ca, could be supplied via a “water wheel”-like arrangement of five waters next to the OEC that is connected by a large channel to the bulk solvent. XES spectra show that Mn oxidation (τ of ∼350 μs) during the S₂ → S₃ transition mirrors the appearance of OX electron density. This indicates that the oxidation state change and the insertion of water as a bridging atom between Mn1 and Ca are highly correlated.
In oxygenic photosynthesis, light-driven oxidation of water to molecular oxygen is carried out by the oxygen-evolving complex (OEC) in photosystem II (PS II). Recently, we reported the ...room-temperature structures of PS II in the four (semi)stable S-states, S
, S
, S
, and S
, showing that a water molecule is inserted during the S
→ S
transition, as a new bridging O(H)-ligand between Mn1 and Ca. To understand the sequence of events leading to the formation of this last stable intermediate state before O
formation, we recorded diffraction and Mn X-ray emission spectroscopy (XES) data at several time points during the S
→ S
transition. At the electron acceptor site, changes due to the two-electron redox chemistry at the quinones, Q
and Q
, are observed. At the donor site, tyrosine Y
and His190 H-bonded to it move by 50 µs after the second flash, and Glu189 moves away from Ca. This is followed by Mn1 and Mn4 moving apart, and the insertion of O
(H) at the open coordination site of Mn1. This water, possibly a ligand of Ca, could be supplied via a "water wheel"-like arrangement of five waters next to the OEC that is connected by a large channel to the bulk solvent. XES spectra show that Mn oxidation (τ of ∼350 µs) during the S
→ S
transition mirrors the appearance of O
electron density. This indicates that the oxidation state change and the insertion of water as a bridging atom between Mn1 and Ca are highly correlated.
With age, susceptibility to osteoarthritis (OA) and OA‐related pain and disability increases. Like in OA patients, gait patterns in rodent OA models shift to protect the injured limb during loading. ...However, unlike in OA patients, it is unknown how age affects gait changes in rodent OA models. In this study, gait compensations following meniscal injury in 3‐, 6‐, and 9‐month‐old rats were evaluated to examine age‐effects of OA‐related joint dysfunction. Rats 3, 6, and 9 months received medial collateral ligament transection plus medial meniscus transection (MCLT + MMT) surgery (n = 8/age group) or a skin incision (n = 8/age group). Postsurgery, rats underwent gait testing at 2, 4, 6, and 8 weeks. Postmortem, joints were processed for histology to assess cartilage damage. MCLT + MMT rats walked with reduced vertical loading in their injured limbs immediately after injury and throughout OA progression. Compared to sham‐operated limbs, 6‐ and 9‐month MCLT + MMT animals reduced loading in their injured limbs while 3‐month MCLT + MMT animals did not. MCLT + MMT rats also increased stance time on the injured limb compared to the contralateral limb. Additionally, for the MCLT + MMT animals, 6‐ and 9‐month animals had significantly worse cartilage damage compared to 3‐month animals. These data indicated age at injury onset affects how animals load the OA‐affected joint, with older animals developing gait compensations that more markedly reduce weight on the injured limb during walking.
Osteoarthritis (OA) is driven by low-grade inflammation, and controlling local inflammation may offer symptomatic relief. Here, we developed an indoleamine 2,3-dioxygenase and galectin-3 fusion ...protein (IDO-Gal3), where IDO increases the production of local anti-inflammatory metabolites and Gal3 binds carbohydrates to extend IDO's joint residence time. In this study, we evaluated IDO-Gal3's ability to alter OA-associated inflammation and pain-related behaviors in a rat model of established knee OA.
Joint residence was first evaluated with an analog Gal3 fusion protein (NanoLuc™ and Gal3, NL-Gal3) that produces luminescence from furimazine. OA was induced in male Lewis rats via a medial collateral ligament and medial meniscus transection (MCLT + MMT). At 8 weeks, NL or NL-Gal3 were injected intra-articularly (n = 8 per group), and bioluminescence was tracked for 4 weeks. Next, IDO-Gal3s's ability to modulate OA pain and inflammation was assessed. Again, OA was induced via MCLT + MMT in male Lewis rats, with IDO-Gal3 or saline injected into OA-affected knees at 8 weeks post-surgery (n = 7 per group). Gait and tactile sensitivity were then assessed weekly. At 12 weeks, intra-articular levels of IL6, CCL2, and CTXII were assessed.
The Gal3 fusion increased joint residence in OA and contralateral knees (p < 0.0001). In OA-affected animals, both saline and IDO-Gal3 improved tactile sensitivity (p = 0.008), but IDO-Gal3 also increased walking velocities (p ≤ 0.033) and improved vertical ground reaction forces (p ≤ 0.04). Finally, IDO-Gal3 decreased intra-articular IL6 levels within the OA-affected joint (p = 0.0025).
Intra-articular IDO-Gal3 delivery provided long-term modulation of joint inflammation and pain-related behaviors in rats with established OA.
Behavioral assays of animal pain and disability can increase the clinical relevance of a preclinical study. However, pain and symptoms are difficult to measure in preclinical models. Because animals ...often alter their movement patterns to reduce or avoid joint pain, gait analysis can be an important tool for quantifying OA-related symptoms in rodents. Technologies to measure rodent gait continue to advance and have been the focus of prior reviews. Regardless of the techniques used, the analysis of rodent gait data can be complex due to multiple confounding variables. The goal of this review is to discuss recent advances in the understanding of OA-related gait changes and provide recommendations on the analysis of gait data. Recent studies suggest OA-affected animals reduce vertical loading through their injured limb while walking, indicating dynamic ground reaction forces are important data to collect when possible. Moreover, gait data analysis depends on accurately measuring and accounting for the confounding effects of velocity and other covariates (such as animal size) when interpreting shifts in various gait parameters. Herein, we discuss different statistical techniques to account for covariates and interpret gait shifts. In particular, this review will discuss residualization and linear mixed effects models, including how both techniques can account for inter- and intra-animal variability and the effects of velocity. Furthermore, this review discusses future considerations for using rodent gait analysis, while highlighting the intricacies of gait analysis as a tool to measure joint function and behavioral outcomes.
From the inception of money market funds (MMFs), all MMFs reported a fixed $1 NAV (Net Asset Value). In July 2014, the Securities and Exchange Commission (SEC) issued new regulations for MMFs that ...require Prime institutional MMFs to report floating NAVs. The SEC did not expect a significant impact on the MMF industry from requiring floating NAVs for Prime institutional funds. We find that over 70% of the assets under management in Prime MMFs left Prime funds with over half the Prime funds closing. We find that more than half of the Prime retail MMFs (which are not required to switch to floating NAV) closed with more than 50% of the assets under management exiting these funds. Finally, we find that for every dollar that exited Prime MMFs a dollar was added to Government MMFs. Based on the SEC's economic discussions, these results all represent unexpected consequences.
Nanoparticles are a promising approach for improving intra-articular drug delivery and tissue targeting. However, techniques to non-invasively track and quantify their concentration in vivo are ...limited, resulting in an inadequate understanding of their retention, clearance, and biodistribution in the joint. Currently, fluorescence imaging is often used to track nanoparticle fate in animal models; however, this approach has limitations that impede long-term quantitative assessment of nanoparticles over time. The goal of this work was to evaluate an emerging imaging modality, magnetic particle imaging (MPI), for intra-articular tracking of nanoparticles. MPI provides 3D visualization and depth-independent quantification of superparamagnetic iron oxide nanoparticle (SPION) tracers. Here, we developed and characterized a polymer-based magnetic nanoparticle system incorporated with SPION tracers and cartilage targeting properties. MPI was then used to longitudinally assess nanoparticle fate after intra-articular injection. Magnetic nanoparticles were injected into the joints of healthy mice, and evaluated for nanoparticle retention, biodistribution, and clearance over 6 weeks using MPI. In parallel, the fate of fluorescently tagged nanoparticles was tracked using in vivo fluorescence imaging. The study was concluded at day 42, and MPI and fluorescence imaging demonstrated different profiles in nanoparticle retention and clearance from the joint. MPI signal was persistent over the study duration, suggesting NP retention of at least 42 days, much longer than the 14 days observed based on fluorescence signal. These data suggest that the type of tracer - SPIONs or fluorophores – and modality of imaging can affect interpretation of nanoparticle fate in the joint. Given that understanding particle fate over time is paramount for attaining insights about therapeutic profiles in vivo, our data suggest MPI may yield a quantitative and robust method to non-invasively track nanoparticles following intra-articular injection on an extended timeline.
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Exercise and physical activity are recommended to reduce pain and improve joint function in patients with knee 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 aims to evaluate how voluntary wheel running following a surgically induced meniscal injury affects gait characteristics and joint remodeling in C57Bl/6 mice. We hypothesize injured mice will reduce physical activity levels as OA develops following meniscal injury and will engage in wheel running to a lesser extent than the uninjured animals.
Seventy-two C57Bl/6 mice were divided into experimental groups based on sex, lifestyle (physically active versus sedentary), and surgery (meniscal injury or sham control). Voluntary wheel running data was continuously collected throughout the study and gait data was collected at 3, 7, 11, and 15 weeks after surgery. At endpoint, joints were processed for histology to assess cartilage damage.
Following 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. Additionally, 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.
Taken together, these data indicate a discordance between structural joint damage and joint function. While wheel running following meniscal injury did worsen OA-related joint damage, physical activity did not necessarily inhibit or worsen OA-related joint dysfunction or pain in mice.
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