The Pathology-MRI Correlative Study Of Osteoarthritis Models Pre-and Post-intra-articular Injecting Ozone

Part I. The comparison of rabbit osteoarthritis models induced by intra-articular injection of different proteases1. Objective: To research the differences between two kinds of osteoarthritis models induced with two different proteases respectively.2. Material and methods: Twelve New Zealand rabbits were randomly and averagely divided into two groups. 0.3ml of 1.6% papain (4.8mg) or 0.5ml collagenase typeâ…¡(2mg)were injected into the right knee cavities of the animals twice separately. Six weeks after the last injection,Radiography and pathological examination were performed to observe the OA establishment progress. ?3. Results: The osteoarthritis-like degenerations at articular cartilage of medial tibial plateau were found pathologically in both groups, which was much severer in collagenases group than in papain one, further proved by comparison of mankin scores of the groups ( 10.2±1.9 vs 4.3±1.0, P=0.000). Furthermore, significant osteophytes at articular margin were revealed in collagenase group by contrast with no evidence of osteophyte in papain one.4. Conclusions: Both kinds of proteases injected into articular cavities can produce osteoarthritis model successfully. Papain induces similar early stage osteoarthritis-like pathological changes while Collagenase induces the mid-to-late stage ones. Part II. The MRI study on articular cartilage of normal and osteoarthritis models1. Objective: To evaluate the optimal sequences and parameters of MRI on articular cartilage, study the high field MRI appearances of normal and OA rabbit knee articular cartilage.2. Methods: a 1.5T Philip Intera MR system was used in the study, 6 normal rabbits underwent knee MRI with PDW/SPAIR/D, T2W₃D_FFE and 3D_WATSc sequences consecutively, the cartilage SNR and cartilage/subchondoral bone CNR of all MRI sequences were compared . An optimal sequence then applied to imaging the knee cartilage of OA model, followed by comparison of MRI appearances of normal and OA cartilage.3. Results: There was no significant difference of cartilage SNRs among PDW/SPAIR/D, T2W₃D_FFE and 3D_WATSc(P=3.840), but there was significant difference of artilage/subchondoral bone CNR among 3 sequencs(P=0.045). Furthermore, the CNR of 3D_WATSc was higher than those of PDW/SPAIR/D and T2W₃D_FFE(P<0.05),while there was no difference of CNRs between PDW/SPAIR/D and T2W₃D_FFE(P>0.05). The rabbit knee articular cartilage presents as a homogeneous layer of intermediate or hyperintense signal in all 3 sequences, while cartilage of OA model was demonstrated decreased and hetergenous signal intensity and decreased width.4. Conclusions: A 3D-spoiled gradient echo with water excitation technique, that is, 3D_WATSc sequence was the optimal sequence for articular cartilage imaging. The articular cartilage of rabbit knee,imaged by a high filed MRI, was demonstrated as a single layer band with homogeneous signal, both signal intensity and width of cartilage were dereased.. Part III. Experimental Pathology-MRI study of the medical Ozone effects on articular cartilage of Osteoarthritic animal models1. Objective: To evaluate the medical ozone effects on articular cartilage of the osteoarthritis animal modelsthe by pathology-MRI correlative study.2. Methods: 24 New Zealand rabbits were involved. Of them,30 Collagenase II induced OA models were established. The rabbits were randomly divided into 4 groups which named normal group, model group, 10μg/ml ozone Intra-articular injection group,30μg/ml Ozone Intra-articular injection group respectively. 6 animals were in each group. Ozone was administered twice per week for 4 weeks after the model establishment. Comparing with the pathology findings,MRI of each model cartilage were studied,mean thickness and signal intensity of articular cartilage were measured and statistically compared with Mankin Score by linear correlation and regress analysis.3. Results: The articular cartilage in those animals of Model and all Ozone interfering groups became thinner and less intense than those of normal groups (P<0.05), the correlative pathology showed the tough surface, deep fissure and descrease in stain intensity of articular cartilage, while there was no significant difference of mean thickness and signal intensity of articular cartilage among model and ozone interfering groups(P>0.05); The mean thickness and signal intensity showed a positive linear correlation(r=0.691), the former two all showed a negative linear correlation with Mankin Score(r value were -0.839 and -0.669 separately). There was an linear regress relation between mean thickness and Mankin Score(R2=0.703).4. Conclusions: Intra-articular injection of middle or low concentration ozone may not be effective on repairing the degenerated cartilage in OA.