| Objective: Condylar cartilage maintains a remodeling state throughout the life process. Except for being subject to the control of such as the body’s own inheritance, body fluids and nerves, various stress stimuli acted on local parts also play an important role. Condylar cartilage cells are able to experience all kinds of stress stimuli. With the action of biomechanical stress, condylar cartilage will produce the conversion of machinery-chemistrybiological signals, showing a series of reactions like cells proliferation, differentiation, an programmed cell death. Application of functional appliance purpose to stimulate the remodeling of the condylar bychanging biomechanica l envi-ronment around condylar. However, we still fail to realize how internal chondrocytes respond to mechanical stress stimulation and mediate the transduction of stimulation signals into cells after that condylar cartilages are subject to mechanical stress, thereby regulating cellular mechanisms of the remodeling of condylar cartilages. Recently, researchs have found that the transcription factor Gli2 has involved in the signal transduction and regulation of condylar cartilage remodeling. Gli2 is closely linked to cartilage cell proliferation, differentiation and bone formation.PCNA is the cell cycle phasespecific expression of nuclear acidic protein,be recognized as one of the signs of cell proliferation activity, can effectively reflect cell proliferation, in this paper as a transcription factor Gli2 promote cell proliferation reference and enrolled in the study. In this experiment, immunohistochemical staining was used to detect the expression and varying patterns of PCNA and Gli2 in condyle during mandibular functional protrusion in growing rats. Then applied to evaluate the effect of functional orthopedic on the remodeling of condylarcartilage, and it may offer the experimental basis for the clinical therapy.Methods: Seventy 4-week-old healthy male Sprague-Dawley(SD) rats were selected, weighing about 90 g. They were randomly and equally divided into experimental group(n=35) and control group(n=35). According to the experimental period(1, 3, 7, 14, 21, 28 and 35 days), the groups were respectively classified into 7 subgroups(5 in each), so there were a total of 14 subgroups. The study was performed after that the rats were allowed to acclimate for a week. In the experimental group, self-made mandibular advancement inclined bite plate appliance was cemented on rat incisors by 3M glass ionomer. Through a chain rubber ring, it was connected with face bow on both sides via nasomaxillary complex, thereby making the inclined bite plate get a stable retention. The rats’ limbs were wrapped tightly with a medical adhesive plaster, which effectively prevented any damage caused by the rats’ forepaws to the appliance and facial tissue. The appliance was used for 24 h. In the control group, no experimental operation was done.All animals were allowed to soft food, drinking water freely. They were reared under the same environment till the end of the experiment. The animals of experimental group, together with their matched control, were sacrificed 1d, 3d, 7d, 14 d, 21 d, 28 d and 35 d after the appliance insertion(n=10 per group each time). Drawing materials, conventional fixation, demineralization, dehy-dration and encapsulation were conducted. After the paraffin section, the routine HE staining observation on condylar histological changes should be made; detected the expressions of Gli2 and PCNA by SP immunohistochemi-cal method, adopted the cell image analysis system to make the rating for immumohistochemical staining and took IHS value to show the staining intensity. All the data results should be processed by SPSS19.0 statistical software. When making the statistic analysis, adopted to test for the comparisons between the experimental group and control group, and adopted one-way ANOVA method for intra-group comparison. Bivariate correlation analysis was used to the experimental group Gli2 and PCNA. P<0.05 means that they had statistical difference, and the test level α=0.05.1 General observationIn the experimental group, rats’ mandibles were in a moderately forwarding condition. Their upper and lower anterior teeth were corresponding. After removing the appliance, the jaw could not retreat. In the control group, the rats’ anterior teeth covered about 3mm.2 Condylar morphological changesIn the control group, with the time extension, the condylar cartilage showed age-related changes, demonstrating thinner cartilage and more significant middle and rear of the changes in the cartilage. In the experimental group, since Day 3rd, different tissue layers of condylar cartilage were thicker; the number of cartilage cells increased. There were significant changes in condylar middle and rear parts while the former part did not change significantly. On Day 21 th, different layers of condylar cartilage gradually stabilized; the transitional layer was still significantly thicker than the control group; and the late chondrocytes, osteoblasts, and a large number of original bone trabeculas and underground marrow cavity were visible.3 Gil2 protein and PCNA expression level and distributionNo positive colored particles were seen in the blank control group(PBS replaced primary antibodies). In the control group, only a small number of Gil2 proteins were positive in the hypertrophic cartilage layer, and they have been maintaining a low expression level until Day 21th; later their expression gradually decreased to a very low level. The difference between groups was not statistically significance(P>0.05). On Day 3rd Gli2 proteins in the experimental group were enhanced significantly in the condylar cartilage, which had significant difference compared to the control group HIS=1.0±0.70(P<0.05). On Day 7th, the experimental group IHS=41.33±3.06 positive expression continued to improve, which had significant difference compared to the control group IHS=5.67±1.53(P<0.05). On Day 14 th, the experimental group IHS=99.00±6.00, basically remaining at the same expression level as Day 7th. On Day 21 th, the experimental group IHS=44.67±6.43. Positive cells in most samples began to decrease, which still had significant difference Results: compared with the control group(P<0.05). On Day 28 th, the experimental group IHS=17.33±6.11, showing no statistical difference with the control group IHS=4.33±1.53. On Day 35 th, Gli2 protein dropped to an extremely low level; the experimental group IHS=7.33±2.08, and the control group IHS=4.33±1.54, showing no statistical difference. In the control group, only a small number of PCNA proteins were positive in the hypertrophic cartilage layer, and they have been maintaining a low expression level until Day 21th; later their expression gradually decreased to a very low level. The difference between groups was not statistically significance(P>0.05). On Day 3rd PCNA proteins in the experimental group were enhanced significantly in the condylar cartilage, which had significant difference compared to the control group IHS=49.67±13.50(P<0.01). On Day 7th, the experimental group IHS= 124.0±7.55 positive expression continued to improve, which had significant difference compared to the control group IHS=9.00±2.00(P<0.01). On Day 14 th, PCNA positive expression of experimental group began to decrease, IHS=108.33±8.50, but they had still significant difference(P<0.01) compared with the control group IHS=8.67±0.58; On Day 21 th, the experimental group IHS= 34.00±15.87. Positive cells in most samples began to decrease, which had no significant difference compared with the control group(P>0.05). There still were no statistical significances(P>0.05) for the experimental group and control group on 28 th and 35 th day, and dropped to an extremely low level.Conclusions:1 Gli2 participated in condylar cartilage adaptive remodeling during the process of mandibular protrusion of rats, and promoted condylar cartilage proliferation and endochondral ossification.2 Gli2 participated in the process of transduction process from mechanical stress to biological signal during the bone remodeling of condylar cartilage of rats. |
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