Region-specific knee cartilage degradation associates with altered kinematics in exercise and immobilized osteoarthritis rats
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cartilage loss results in pain, the main symptoms of OA patients. OA pain involves a complex integration of sensory, affective, and cognitive pro- cesses. The correlation between structural damage of the joint and pain is weak, the prevalence of knee pain in patients with radiographic knee OA ranges from 15% e81% in different studies. Still, gradual increase of pain seems to be connected with OA progression and therefore pain is discussed as an indicator of disease activity. Recent MRI studies further revealed a positive relationship between in flammatory changes in the joint and pain raising the intriguing question of which in flammatory mechanisms and mediators might be involved in pain generation. Nociceptors are located throughout the joint in tissues peripheral to cartilage but not in cartilage itself. Increased nociceptive inputs from the joints cause complex changes in the central nervous system. In the state of central sensitization, nociceptive neurons at different levels of the neuraxis are hyperexcitable, and hence, the nociceptive processing is ampli fied. Peripheral nociceptors are important targets in analgesic therapy due to the fact that many pathological conditions such as in flammation induce receptor excitation and sensitization. Numerous ion channels and receptors take part in nociception and might function as targets in pain therapy. Therefore, we analyzed electrophysiological properties of neuronal cells under the in fluence of conditioned medium derived from chondrocytes and synoviocytes from OA patients. Methods: Neuroblastoma cells (MHH) were grown in the presence of conditioned medium (CM) derived from chondrocytes (CM-c) and synoviocytes (CM-s) isolated from OA patients. After 5 days of treat- ment MHH cells were tested for their electrophysiological behavior by the patch clamp technique. Expression of ion channels including the peripheral Na þ channels Nav1.6 e1.9 and the K þ channels KCNQ2 and KCNQ3 respectively was assessed by qPCR. Both types of CM from all five patients were tested for the content of thirteen cytokines including MCP1, Il-6 and IL-8 via the human in flammation panel (Legendplex). Results: Whole cell Na þ current measurements revealed, in four out of five samples, a reduction of the maximal conductance (g max ) of MHH cells under CM-c, CM-s reduced g max in three out of five cases. The steady state activation in all cases was shifted to a more positive membrane potential (E m ), the inactivation and recovery kinetics were unchanged. For the K þ current a reduction in I max was observed in four out of five samples under both treatment conditions (CM-c and CM-s), the steady state activation was unchanged. Expression studies showed changes of voltage dependent Na þ channels with the most prominent effect for Nav1.7, the expression of the two K þ channels KCNQ2, 3 was down regulated. Results from the in flammation panel showed IL-6, IL-8 and MCP1 to be present in the CM-c and CM-s. Conclusions: Treatment with conditioned medium changes the elec- trophysiological behavior of neuroblastoma cells. Changes in channel expression indicate a rearrangement of the channel composition which could explain changes in the observed Na þ and K þ currents. Altered cytokine and chemokine production of OA chondrocytes or synovio- cytes could contribute to changes in gene expression by binding to their respective receptors on MHH cells. We hope that identifying changes in electrophysiological properties association with detecting biochemical mediators involved in the generation of pain can open up new OA treatment strategies. 677 ANALGESIC EFFECTS OF MORPHINE AT REST AND DURING MOVEMENT ON KNEE OSTEOARTHRITIS INDUCED BY INTRA- ARTICULAR MONOSODIUM IODOACETATE IN YOUNG RATS J. Morko, J. Vaaraniemi, J. Lehtimaki, J. Zdrojewska, Z. Peng, J.M. Halleen. Pharmatest Services Ltd, Turku, Finland Purpose: Several experimental animal models have been developed for human osteoarthritis (OA) and used to study the preclinical ef ficacy of disease and symptom modifying OA drug candidates. One of these models is induced chemically by an intra-articular injection of monosodium iodoacetate (MIA) into rat knee. Intra-articular MIA disrupts chondrocyte glycolysis through the inhibition of glyceraldehyde-3-phosphate dehy- drogenase. This leads to chondrocyte death and cartilage damage in the entire knee joint and results in OA symptoms including joint pain. Pre- viously, we have characterized the effects of intra-articular MIA injection on knee joint discomfort and pain brie fly, and on articular cartilage, synovium and bone in more detailed in young adult rats. In this study, we characterized the effects of intra-articular MIA injection on knee joint discomfort and pain in more detailed and evaluated the analgesic effects of opioid morphine at rest and during movement in young rats. Methods: This study was conducted using young male Sprague-Dawley rats. The rats were randomized into the following three experimental groups by strati fication according to body weight (150e208 g): 1) intact control rats; 2) MIA-injected rats; 3) MIA-injected rats treated with mor- phine (3 mg/kg s.c.; Takeda, Linz, Austria). At the beginning of the study, rats were weighed and baseline values for knee joint discomfort and pain parameters were determined. Unilateral OA was induced by the intra- articular injection of MIA (Sigma-Aldrich, St. Louis, MO, USA) at 2 mg into the right knee joint of rats in study groups 2 and 3. The effects of intra- articular MIA on body weight and knee joint discomfort and pain, and the analgesic effects of morphine were analyzed at 2 days and at 1, 2, 3 and 4 weeks after the MIA injection. Knee joint discomfort was determined as static weight bearing and measured as hind paw weight distribution (HPWD) using Incapacitance Tester (Linton Instrumentation, Norfolk, UK). Knee joint pain was determined as static mechanical/tactile secondary allodynia and analyzed as paw withdrawal threshold (PWT) using von Frey mono filaments (1e15 g; Aesthesio; DanMic Global, San Jose, CA, USA). Changes in gait were used as an index of knee joint discomfort and pain during movement. The gait was analyzed using CatWalk XT computer- assisted method of locomotor analysis (Noldus Information Technology, Wageningen, Netherlands). The analgesic effects of morphine were stud- ied by von Frey mono filaments 1 hour, by CatWalk 1.5 hours and by Incapacitance Tester 2 hours after treatment. This experimental protocol was approved by National Animal Experiment Board, Regional State Administrative Agency for Southern Finland, Hameenlinna, Finland. Results: Intra-articular MIA injection decreased PWT during the entire 4-week-long study period demonstrating static mechanical allodynia and neuropathic pain in MIA-injected hind limb. Treatment with mor- phine reversed the reduction in PWT completely at all time points studied indicating signi ficant analgesic effects on static mechanical allodynia. The intra-articular MIA injection decreased static HPWD during the entire study period as well demonstrating knee joint dis- comfort in MIA-injected hind limb. Treatment with morphine reversed this reduction partly during the first 3 weeks indicating analgesic effects on knee joint discomfort. The MIA injection decreased dynamic weight bearing and slowed down and impaired movement during the entire study period. This was demonstrated by changes in various gait parameters in MIA-injected hind limb at all time points studied, including decreased print area, max contact area, print length, print width, weight bearing, stand index, swing speed, duty cycle, single stance, stride length and coupling (right hind e left front), and increased swing time. As analgesic effects during movement, treatment with morphine reversed changes in various gait parameters, including in weight bearing, single stance and the coupling at all time points studied. Conclusions: This study demonstrated that the intra-articular injection of MIA into the knee joint of young rats induced static mechanical allodynia, impaired weight bearing capacity, and slowed down and impaired movement during the entire 4-week-long study period. Treatment with morphine prevented static mechanical allodynia com- pletely and the impairment in weight bearing capacity and movement Download 389.18 Kb. Do'stlaringiz bilan baham: |
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