Ascorbic acid increases the severity of spontaneous knee osteoarthritis in a guinea pig model

OBJECTIVE: To determine whether ascorbic acid might be of benefit for the treatment of spontaneous osteoarthritis (OA) when administered over a long period of time. METHODS: We investigated the effects of 8 months' exposure to low, medium, and high doses of ascorbic acid on the in vivo development of histologic knee OA in the male Hartley guinea pig. The low dose represented the minimum amount needed to prevent scurvy. The medium dose was the amount present in standard laboratory guinea pig chow and resulted in plasma levels comparable with those achieved in a person consuming 200 mg/day (5 fruits and vegetables daily). The high dose was the amount shown in a previous study of the guinea pig to slow the progression of surgically induced OA. RESULTS: We found an association between ascorbic acid supplementation and increased cartilage collagen content but, in contrast to findings in a previous study of surgically induced OA in the guinea pig, ascorbic acid worsened the severity of spontaneous OA. Active transforming growth factor beta (TGF beta) was expressed in marginal osteophytes, whose size and number were significantly increased with increasing intake of ascorbic acid. Synovial fluid levels of cartilage oligomeric matrix protein, a biomarker of cartilage turnover, corroborated the histologic findings. CONCLUSION: Ascorbic acid has been shown to activate latent TGF beta. Prolonged intraarticular exposure to TGF beta has been shown to cause OA-like changes. We found expression of active TGF beta in osteophytes, a prominent feature of the joint histology seen in association with ascorbic acid treatment. Thus, the deleterious effects of prolonged ascorbic acid exposure may be mediated in part by TGF beta. This worsening of OA with ascorbic acid supplementation suggests that ascorbic acid intake should not be supplemented above the currently recommended dietary allowance (90 mg/day for men and 75 mg/day for women).     

Macrophage depletion test in guinea pigs]

In the present investigations heterologous lymphokine-containing fluids were examined in albino guinea pigs for their macrophage depletion activity. Cell-free ascites from Ehrlich ascites tumor and leukemia L 1210 of mice as well as supernatants of PHA-stimulated peripheral blood lymphocyte cultures were used. Ascites of Ehrlich's ascitic tumor and Leukemia L 1210 led to a significant depletion of macrophages. The application of supernatants of PHA-stimulated human lymphocyte cultures resulted in a dose-dependent reduction of peritoneal macrophages. On the other hand, a stimulation of the number of peritoneal macrophages by control supernatants of non-stimulated lymphocyte cultures was observed. The findings indicate the existence of two lymphokines having opposite effects.     

Effects of body weight restriction on the development and progression of spontaneous osteoarthritis in guinea pigs

Hartley albino guinea pigs develop spontaneous osteoarthritis (OA) of the knee joint. A study was done to determine the importance of body weight in the pathogenesis of this disease. Two groups of 20 male guinea pigs each were maintained on the same diets. The control group was allowed ad libitum feed consumption and the other group was restricted to 30-35 gm of feed per day. Ten animals from each group were killed at 9 months of age to evaluate histologic features of the knee joints. The severity of the OA lesions was reduced by 40%, in conjunction with a 28% decrease in body weight, in the diet-restricted group. The remaining animals were killed at 18 months of age. Those in the diet-restricted group had a 56% reduction in severity of lesions, with a 29% decrease in body weight. These results indicate that body mass in guinea pigs, as in humans, is an important predisposing factor for the development of spontaneous OA of the knee.     

Effects of growth factors and cytokines on proteoglycan and collagen synthesis by chondrocytes in guinea pigs with spontaneous osteoarthritis

We examined the effects of various growth factors and cytokines on proteoglycan (PG) and collagen synthesis by chondrocytes isolated from osteoarthritic and normal articular cartilage of Hartley strain guinea pigs. The guinea pig represents a useful animal model of spontaneous osteoarthritis (OA). Cartilage tissue samples were obtained from the knee joints of under-3-month-old guinea pigs (control group) as well as 5- to 8-month-old guinea pigs with OA changes (OA group). Chondrocytes were isolated enzymatically and maintained in suspension culture. Growth factor addition groups were then prepared from both the OA group and the control group, using the factors TGF-β, bFGF, and IGF-1 (1.25 ng/ml each). Cytokine addition groups were also prepared using IL-1α and IL-1β (10 ng/ml each). An addition group was also prepared for sodium hyaluronate (HA) (500 μg/ml). In each group, ³⁵S was added as a PG metabolic marker, ³H-proline was added as a collagen metabolic marker, and the groups were cultured. Next, ³⁵S and ³H-proline uptake was measured by a liquid scintillation counter. The results revealed that (1) both PG synthesis and collagen synthesis were promoted significantly more in OA chondrocytes than in normal chondrocytes; (2) with the addition of growth factors, PG and collagen synthesis was enhanced in OA chondrocytes; and (3) PG synthesis and collagen synthesis were inhibited in both normal and OA chondrocytes with the addition of IL-1α and -β. This result suggests that the repair function is activated more in OA chondrocytes than in normal chondrocytes, thereby promoting the synthesis of the cartilage matrix by chondrocytes. This synthesizing capability is enhanced and acts to effectively repair degenerative articular cartilage further through the addition of growth factors. Received September 20, 1999 / Accepted December 6, 1999     

电针对膝骨性关节炎家兔模型软骨细胞凋亡的影响

目的观察电针对膝骨性关节炎(KOA)家兔模型软骨细胞凋亡的影响。方法将36只新西兰大白兔随机分成正常组(A组)、模型组(B组)、电针组(C组)和氨基葡萄糖胶囊组(D组),每组9只。除A组外,其余三组新西兰大白兔采用左后肢膝关节伸直位石膏固定6 w,建立KOA动物模型。造模成功后,解除石膏制动,A组和B组给予正常饲养;C组取左后肢足三里、犊鼻、血海、阳陵泉、膝眼、梁丘六个穴位,用毫针进行针刺,直刺或斜刺15³0 mm,得气后,针柄接电针治疗仪,疏密波型,频率230 mm,得气后,针柄接电针治疗仪,疏密波型,频率2¹00 Hz,强度以局部皮肤肌肉轻微颤动为度。每次电针两组,每次留针20 min,每日1次,连续治疗3 w;D组按90 mg·kg-1·d-1灌服3 w。处理后,分别取各组家兔膝关节软骨标本,采用TUNEL法检测软骨细胞凋亡并计算凋亡指数(AI)。结果经治疗后,C组与B组比较有显著性差异(P=0.001)。结论电针能改善KOA家兔模型软骨细胞的过度凋亡,以发挥对KOA的防治作用。     

Role of leukocyte depletion in noncholinergic bronchoconstriction of guinea pigs.

To test the role of leukocytes in the activation of afferent C-fibers in the lung, 33 guinea pigs, 18 control and 15 experimental or leukocyte depleted, were used. The leukocyte depletion was accomplished with an intraperitoneal injection of cyclophosphamide (100 mg/kg) 96 h prior to the study. On the day of the study, bronchial constriction was produced either by exsanguination (n = 17) or by capsaicin injection (16 micrograms/kg, i.v.) (n = 16) in anesthetized-paralyzed animals. Venous blood samples were collected for leukocyte counts. At 1-30 min following the above treatment, the maximal expiratory flow maneuver was performed and a decrease in the maximal expiratory flow at 50% baseline total lung capacity (Vmax50) was used as an index of bronchoconstriction. The leukocyte count decreased significantly following the pretreatment with cyclophosphamide [an average of 6217 +/- 612 (control) vs. 2242 +/- 334/mm3 (experimental)]. Exsanguination caused a gradual decrease in Vmax50 with time, indicating a temporal increase in bronchoconstriction. Capsaicin injection, on the other hand, caused an immediate (1 min) marked bronchoconstriction, which attenuated gradually with time. At a specific time point, leukocyte depletion did not produce any significant change in Vmax50 compared to the control group for both types of bronchoconstrictions. Based on these results, we conclude that leukocytes may play an insignificant role in the bronchoconstriction caused by the activation of afferent C-fibers in guinea pig lungs under our experimental conditions.     

Ouabain binding and inotropy in acute potassium depletion in guinea pigs

In hypokalaemia the incidence of cardiac toxicity with digitalis is increased, possibly through changes in the affinity or capacity of the digitalis receptor in the heart. Previous studies have reported an increased ouabain binding capacity or Na+-K+ ATPase activity after hypokalaemia in human erythrocytes and rabbit and guinea pig hearts and no change or decreases in rabbit or rat skeletal muscles with no changes in ouabain affinity. The present study determined (a) the effect of potassium on 3H-ouabain binding to normokalaemic guinea pig cardiac cell membranes, (b) the effect of acute hypokalaemia induced by a potassium deficient diet for 14-18 days in guinea pigs on 3H-ouabain binding to erythrocytes and cardiac and skeletal muscle homogenates, and (c) ouabain induced inotropy in isolated contracting guinea pig left atria, right ventricular papillary muscles, and soleus muscle strips from normokalaemic and hypokalaemic guinea pigs. 3H-ouabain binds to cardiac cell membranes in the presence of magnesium and inorganic phosphate with an affinity (KD value) of 1.13 X 10(-7) mol X litre-1. Potassium decreased this affinity without changing the binding capacity. Erythrocytes and heart muscle homogenates showed the same affinity as cardiac cell membranes, whereas soleus muscle homogenates had a higher affinity for ouabain (KD 5.1 X 10(-8) mol X litre-1). After hypokalaemia, the ouabain affinity did not change in any tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Granulocyte depletion prevents tumor necrosis factor-mediated acute lung injury in guinea pigs

To examine the role of polymorphonuclear neutrophils (PMN) and other granulocytes in the pathogenesis of acute lung injury caused by tumor necrosis factor alpha (TNF), we compared the permeability edema and pulmonary histopathology in normal (granulocyte sufficient) guinea pigs and in granulocytopenic guinea pigs treated with TNF. Circulating granulocytes were depleted with cyclophosphamide. Two groups of normal animals were treated with either saline (PMN+/Control) or 1.4 x 10(6) U/kg recombinant human TNF (PMN+/TNF). Three granulocytopenic groups were treated with either saline (PMN-/Control), TNF (PMN-/TNF), or intravenous infusion of 2 x 10(9) E. coli strain J96 (PMN-/Sepsis). We measured the amount of 125I-labeled albumin in bronchoalveolar lavage (BAL) fluid and whole lung tissue and the wet/dry lung weight ratio to assess pulmonary transvascular protein flux and edema. We also quantified PMN in BAL fluid and fixed lung tissue. There were no statistically significant differences in any of these parameters between the PMN+/Control, PMN-/Control, or PMN-/TNF groups, except that the PMN+/Control predictably had more PMN/alveolus than the PMN- groups. However, both the PMN+/TNF and the PMN-/Sepsis groups had increased amounts of 125I-labeled albumin in BAL fluid and lung tissue (p less than 0.01) and increased wet/dry lung weight ratios (p less than 0.05), compared to all other groups. Histopathologically, capillary congestion and moderate inflammation were seen in the PMN+/TNF group, and acute inflammation and gross alveolar hemorrhage were seen in the PMN-/Sepsis group.(ABSTRACT TRUNCATED AT 250 WORDS)     

大黄素对豚鼠胃窦环形肌自发性收缩活动的影响及相关机制

目的:观察大黄素(emodin)对豚鼠胃窦环形肌自发性收缩活动的影响及相关机制.方法:用四道生理记录仪记录豚鼠胃窦环形肌自发性收缩活动;用膜片钳记录豚鼠胃窦环形肌细胞上L型钙电流,观察L型钙电流在大黄素增强豚鼠胃窦环形肌自发性收缩活动中的作用.结果:大黄素在一定的浓度范围内增强豚鼠胃窦环形肌自发性收缩活动并呈剂量依赖性,给予5、10、15、20、25、50mol/L的大黄素后豚鼠胃窦环形肌自发性收缩的幅度分别为对照组的108.2%±6.2%、150.6%±8.3%、198.2%±7.6%、200.2%±8.6%、160.0%±6.8%、81.2%±6.2%.预先加入10mol/L的硝苯地平,完全阻断大黄素增强豚鼠胃窦环形肌自发性收缩活动.10mol/L和20mol/L的大黄素明显增强豚鼠胃窦环形肌细胞上钡电流(IBa),用10mol/L的大黄素灌流开始后200s左右时IBa电流峰值变化趋于稳定,20mol/L的大黄素灌流开始后170s左右时IBa电流峰值变化趋于稳定.加药后IBa电流峰值分别增加到对照组电流最大值的137.88%±5.79%和158.69%±6.11%.结论:大黄素增强豚鼠胃窦环形肌自发性收缩,细胞外钙通过L型钙通道内流入细胞内引起平滑肌收缩是大黄素促进豚鼠胃窦环形肌自发性收缩的作用机制之一.     

Correlation of morphologic and biochemical changes in the natural history of spontaneous osteoarthrosis in guinea pigs

Objective. To study how the concentrations of proteoglycans (PGs) and collagen change in various parts of tibial articular cartilage during aging, and to evaluate the development of spontaneous osteoarthrosis (OA) in guinea pigs. Methods. PGs were extracted from guinea pig cartilage samples using 4M guanidine hydrochloride, and the amount of hydroxyproline was determined in the extraction remainder. The molecular size and aggregation of PGs were analyzed by electrophoresis, and the glycosaminoglycan composition was assessed by highperformance liquid chromatography. Results. The PG concentration was proportional to the load distribution. However, when OA became histologically manifest, the PG concentration decreased by 50% (from a mean of 44 μg to 22 μg per mg fresh tissue) and the collagen level decreased by 40% (from a mean of 17 μg to 10 μg per mg fresh tissue), while the proportion of water increased by 13% (from a mean of 710 mg to 800 mg per mg fresh tissue). Conclusion. Unmineralized cartilage can, within physiologic load limits, respond to increased mechanical demands by increasing the PG and collagen concentrations. Beyond a certain limit, however, the cartilage can no longer compensate for further increases in stress, which results in cartilage degeneration and losses of matrix constituents. These losses seemed to appear earlier in the disease process than has been described in previous animal models of secondary OA.     

Intra-articular hyaluranic acid compared with progressive knee exercises in osteoarthritis of the knee: a prospective randomized trial with long-term follow-up

The goal of this study was to determine whether hyaluronic acid (HA) or progressive knee exercises (PE) can improve functional parameters in patients with osteoarthritis (OA) of the knee. In a prospective clinical trial 200 knees (105 patients) with radiographic Kellgren Lawrence grade III OA were randomized and received either three intra-articular injections of hyaluronic acid (Hylan G-F 20) at one-week intervals or PE for 6 weeks. Patients were evaluated by use of the Hospital for Special Surgery (HSS) Knee Score and followed-up for 18 months. Total HSS score for HA and PE patients improved from 62.6±13.8 to 88.8±11.1 and from 65.4±12.3 to 88.3±9.1, respectively, at the end of the trial (P<0.01). There were no statistically significant differences between the groups. Twenty-one patients of the HA group were excluded from the study because they had received another form of therapy. All patients in the PE group completed the trial. The patients who dropped out had also significant improvement from 57.0±12.9 to 76.7±11.9 (P<0.01). This prospective randomized trial confirmed that both HA injections and PE result in functional improvement. HA injections also increase the levels of satisfaction of the OA patients.     

Mediation of guinea pig gastric secretion in vitro by cyclic nucleotides.

The effect of methacholine, theophylline, and cyclic adenyl and guanyl nucleotides on gastric secretion from antral and proximal duodenal mucosa of the guinea pig was studied. Both 2 mM dibutyryl (db) cAMP and 5 mM theophylline produced significant increases in gastrin secretion, 4.3 +/- 0.7 (P less than 0.001) and 9.3 +/- 2.4 pg mg-1 min-1 (P less than 0.005) respectively, above basal gastrin secretion (1.5 +/- 0.4 pg mg-1 min-1). The combined effect of the two agents was additive (14.5 +/- 3.6 pg mg-1 min-1). Db cGMP (2 mM) had no effect on gastrin secretion. Methacholine produced a dose-related increase in gastrin secretion which at maximum equaled the combined effect of theophylline and db cAMP. The results suggest that gastrin secretion is mediated in part by intracellular cAMP but do not exclude a cooperative involvement of cGMP.     

Gait changes in patients with knee osteoarthritis are replicated by experimental knee pain

Objective

Medial knee osteoarthritis (OA) is characterized by pain and associated with abnormal knee moments during walking. The relationship between knee OA pain and gait changes remains to be clarified, and a better understanding of this link could advance the treatment and prevention of disease progression. This study investigated changes in knee moments during walking following experimental knee pain in healthy volunteers, and whether these changes replicated the joint moments observed in medial knee OA patients.

Methods

In a crossover study, 34 healthy subjects were tested on 3 different days; gait analyses were conducted before, during, and after pain induced by hypertonic saline injections (0.75 ml) into the infrapatellar fat pad. Isotonic saline and sham injections were used as control conditions. Peak moments in frontal and sagittal planes were analyzed. The results were compared with data from 161 medial knee OA patients. The patients were divided into less severe OA and severe OA categories, which was based on radiographic disease severity of the medial compartment.

Results

Experimental knee pain led to reduced peak moments in the frontal and sagittal planes in the healthy subjects, which were similar to the patterns observed in less severe OA patients while walking at the same speed.

Conclusion

In healthy subjects, pain was associated with reductions in knee joint moments during walking in a manner similar to less severe knee OA patients. The experimental model may be used to study mechanically‐driven knee OA progression and preventive measures against abnormal joint loading in knee OA.     

Role of subchondral bone in osteoarthritis development: a comparative study of two strains of guinea pigs with and without spontaneously occurring osteoarthritis

OBJECTIVE: To evaluate the relationships among cartilage and subchondral bone before and after the onset of cartilage degeneration in the Hartley guinea pig model of spontaneous osteoarthritis (OA) as compared with those in Weiser-Maple guinea pigs, which do not develop OA. METHODS: Mice from each strain were used at ages 2, 3, 5, and 8 months (n = 7 at each time point). The region observed was the medial tibial plateau. Cartilage degeneration was evaluated histologically. Subchondral bone structure was evaluated based on subchondral bone plate thickness and subchondral cancellous bone trabecular parameters calculated from the microfocal computed tomography 3-dimensional reconstruction image. The bone mineral density (BMD) of the subchondral cancellous bone as well as levels of urinary N-telopeptide of type I collagen (NTX) and serum osteocalcin (OC) were measured. RESULTS: In Hartley guinea pigs, the number of chondrocytes in the surface layer started to decrease at 3 months. At 8 months, fibrillation expanded to the radial zone. In Weiser-Maple guinea pigs, no cartilage degeneration was noted even at 8 months. Subchondral bone plate thickness was significantly lower in Hartley guinea pigs than in Weiser-Maple guinea pigs at 2 months. The subchondral bone had a rod-like and convex structure at 2 months in Hartley guinea pigs. BMD was significantly lower in Hartley guinea pigs than in Weiser-Maple guinea pigs at 2 months. The serum OC level was significantly higher in Hartley guinea pigs than in Weiser-Maple guinea pigs at 2 months and 3 months, whereas the urinary NTX level was significantly lower in Hartley guinea pigs at 3 months. CONCLUSION: Subchondral bone is fragile, and bone formation may be promoted in subchondral bone before the onset of cartilage degeneration in Hartley guinea pigs. Subchondral bone may be involved in the development of OA.     

Low-level increases in serum C-reactive protein are present in early osteoarthritis of the knee and predict progressive disease

Objective. To examine the role of low-grade inflammation in the etiology and progression of early osteoarthritis (OA) of the knee. Methods. We used a new, high-sensitivity, automated monoclonal antibody immunoassay for the classic acute-phase protein, C-reactive protein (CRP), in serum. Anteroposterior radiographs of the knee with weight bearing were obtained on 845 women (ages 44–67) on entry into a population-based study of OA in Chingford, North London. In those defined radiologically as “cases,” the knee radiographs were repeated after 4 years. Results. Levels of CRP were higher in 105 women with knee OA defined radiologically as Kellgren-Lawrence grade 2+ (median 2.4 mg/liter, interquartile range [IQR] 1.0–5.1), compared with 740 women without OA (median 0.7 mg/liter, IQR 0.3–1.8) (P < 0.001). Median levels of CRP were higher in the 31 women whose disease progressed at least 1 Kellgren-Lawrence grade (median 2.6 mg/liter, IQR 1.9–4.6), compared with the 39 whose disease did not (median 1.3 mg/liter, IQR 0.6–2.4) (P = 0.006). The significance of these differences persisted after adjustment for age, weight, height, smoking, knee pain, or injury. Classifying disease by the presence of joint space narrowing or osteophytes alone produced similar results. Conclusion. CRP levels are modestly but significantly increased in women with early knee OA, and higher levels predict those whose disease will progress over 4 years, suggesting that low-grade inflammation may be a significant aspect of early OA and may be amenable to therapeutic intervention and secondary prevention.     

Mechanisms of bronchoconstriction induced by anaphylaxis in sensitized guinea pigs

Anaphylactic reaction in sensitized guinea pigs is known to induce bronchoconstriction when an adequate amount of antigen is administrated. This phenomenon has been established as a model of bronchial asthma. To evaluate the mechanism of bronchoconstriction in anaphylaxis, we analyzed the change of endobronchial pressure in sensitized guinea pigs. Guinea pigs weighing 300-600 g were actively sensitized by intracutaneously administrated ovalbumin (10 mg). Two weeks later they were anesthetized and mechanically ventilated with a volume type Harvard respirator. Antigen was administrated intravenously and monitoring of endotracheal pressure and systemic blood pressure was performed. Drugs to modify these reactions were administrated intraperitoneally 30 minutes before antigen challenge. In the control group, the endotracheal pressure showed a curve with the first peak between 0.5 and 1.5 minutes after the antigen challenge. When cyclooxygenase inhibitor (indomethacin) was administered before the antigen, the first peak was markedly suppressed. However, the histamine (H1)-receptor blocker did not suppress the first peak. On the other hand when 5-lipoxygenase inhibitor (AA-861) was administered before the antigen, the increase of intratracheal pressure was suppressed between 2 and 4 minutes after the antigen challenge. The above results may suggest that the first peak of intratracheal pressure derives from bronchoconstriction caused by prostaglandins or thromboxanes, and that the increase of intratracheal pressure at between 2 and 4 minutes derives from bronchoconstriction caused by leukotrienes.