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Objective @#To investigate the histological damage recovery of temporomandibular joint condylar cartilage caused by chronic unpredictable moderate stress, aiming to provide an experimental basis for the prevention and treatment of temporomandibular disorder.@*Methods @#This animal experiment was approved by the Laboratory Animal Ethical Inspection, School of Stomatology, The Fourth Military Medical University (No. 2020081). 60 male SD rats were randomly divided into control group, stress group, and 2-, 4- and 8-week post-stress recovery groups. Rats were subjected to chronic unpredictable moderate stress (CUMS) for 8 weeks including damp sawdust for 24 hours, tilted cage for 12 hours, noise for 4 hours, light/dark cycle reversal, water immersion, tail clamp, and restraint stress. The serum assessment, behavioral tests, histological and ultrastructural observation were performed 2-, 4- and 8-weeks after stress factors were removed. Serum levels of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were determined with ELISA. The sucrose preference test (SPT) and the forced swim test (FST) were used to assess the depressive-like behavior. The expression level of interleukin-1α (IL-1α) and matrix metalloproteinases-3 (MMP-3) were determined by Immunohistochemistry and Western blot.@*Results @#At the end of 8 weeks of CUMS, the serum levels of CORT and ACTH were significantly higher in stress group compared with control group (P<0.01). The sucrose preference decreased significantly and the immobility time increased significantly in the stressed rats compared with those in the control group, indicating a successful establishment of CUMS. The condylar cartilage showed significant degenerative changes, with disorganized collagen fibers and reduced proteoglycan synthesis on the cartilage surface. IL-1α and MMP-3 were expressed in the intracellular and extracellular matrix of the condylar cartilage, and their expression levels were increased (P<0.01). After 2 weeks of stress removal, the serum levels of CORT and ACTH were decreased but higher than control group (P<0.01), and behavioral changes were still different from the control group (P<0.01); the loosened collagen fibers could still be seen on the surface of condylar cartilage, and some free cell areas were visible within the proliferative layer; additionally, IL-1α and MMP-3 expression in the condyle was reduced in all layers of cartilage when compared with the stress group, but was still higher than in the control group (P<0.01). After 4 weeks of stress removal, the serum levels of CORT and ACTH changes returned to normal levels and behavioral changes were still different from control group (P<0.05); a few collagen fibers could be seen on the surface of the condylar cartilage and the expressions of IL-1α and MMP-3 decreased significantly compared with the stress group (P<0.01), with the similar level of IL-1α (P>0.05) and higher expression of MMP-3 comparing with the control group (P<0.01). After 8 weeks of stress removal, behavioral changes returned to normal levels, with no statistically significant differences compared with the control group (P>0.05). The condylar collagen fibers increased and showed a corrugated pattern, and no serious subchondral bone damage as well as irreversible damage occurred. Both of the expression levels of IL-1α and MMP-3 approached those of the control group after 8 weeks of stress removal (P>0.05). @*Conclusion@# The behavioral changes and condylar cartilage damage caused by CUMS could be self-repaired. The decline in IL-1α and MMP-3 expression may be one of the intrinsic mechanisms of this self-repair process.
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Objective: To observe the effect of type 1 bone morphogenetic protein (BMP) receptor activin A receptor type 1 ( ACVRl) on the morphology, proliferation and differentiation of the mandibular condylar cartilage (MCC) cells in the postnatal mice, and to provide the reference for the study on etiology and treatment of MCC-related disease. Methods: The C57BL/6J mouse model of conditional deletion of ACVRl gene was constructed by using the Cre-LoxP system. The female and male mice with Acvrl1" ; RS/RS and Acvrl ; Osterix (+)/( ) genotypes were paired off with each other; the offspring Osterix-Cre ( + ); Acvrl'∗ ; RS/+ genotype mice were selected as experiment group, and the Osterix-Cre ( + ); Acvrl1" ; RS/+ mice were selected as control group. The newborn (n-3). postnatal day 21 (n=4) and PN42 (n=5) male mice were selected. X-gal staining was used to detect the expressions of Osterix-Cre in MCC tissue of the mice in two groups. micro-CT was used to detect the condylar widths and condylar head lengths of mandible of the mice in two groups. HE and Toluidine blue staining were used to analyze the morphology of MCC cells and the thickness of caritilage in each layer of MCC tissue of the mice in two groups, immunohistochemical (1HC) staining was used to detect the number of proliferating cell nuclear antigen (PCNA)-positive cells and the level of type X collagen in MCC tissue of the mice in two groups. Results: The X-gal staining and 1HC results showed that the mouse model of ACVRl gene conditional deletion was successfully constructed. At PN21. compared with control group, the condylar width and the condylar head length of mandible of the mice in experiment group were significantly shortened ( P<0. 05); the morphology of the MCC cells of the mice in two groups had no significant difference. Compared with control group, the number of PCNA-positive cells in the MCC cells of hypertrophic chondrocyte zone (Hy) and chondroblastic zone (Ch) and single Hy of the mice in experiment group were significantly increased ( P<0. 05 or P-<0. 01). At PN42. compared with control group, the shape of parts of the mandibular condylar cartilage cells of the mice in experiment group was abnormal, and the arrangement of some condylar chondrocytes was disordered, the cell thickness of the Ar. Pr and Ch in intermediate part and Hy in anterior part of the condylar cartilage of the mice in experiment group were significantly increased ( P<0. 05 or P<.0. 01); compared with control group, the number of PCNA-positive cells in each zone and the level of type X collagen in Ch of MCC tissue of the mice in experiment group were incresed. Conclusion: ACVRl affects the morphology of MCC cells and structure of MCC tissue by inhibiting the proliferation of MCC cells and the differentiation of chondroblasts into hypertrophic chondrocytes.
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BACKGROUND: Although it has been found in many studies that three-dimensional finite element analysis can be used in the study of knee joint biomechanics, there are few researches on different defect areas of medial condyle cartilage of the femur. OBJECTIVE: To analyze the stress change trend of perimeter articular cartilage before and after the occurrence of different defect areas of medial femoral condyle cartilage, providing biomechanical data for patients with knee medial femoral condyle cartilage defect. METHODS: One normal adult had been selected to establish a three-dimensional finite element model. Material mechanical properties were input to Abaques software with divided grid model. After controlling boundary condition with mechanical load, structural nonlinear finite element was calculated. First, the load stress distribution of knee cartilage and meniscus was observed under normal stress. Articular cartilage stress distribution was observed with load conditions in different defects (0, 6, 8, 10, 12, 14, 16, 18 and 20 mm) of medial femoral condyle. The stress changes on the cartilage were analyzed during the defect of medial femoral condyle. This study was approved by the Ethics Committee of First Affiliated Hospital of Kunming Medical University. The volunteer signed the informed consent. RESULTS AND CONCLUSION: (1) Material properties, boundary conditions and the introduction of loads were defined successfully. The stress cloud chart and its stress data were obtained from different diameter defects of cartilage in medial condyle of knee joint. According to statistical analysis, the stress on the femoral condyle and tibial plateau cartilage had significant changes compared with no defects when the medial femoral condyle cartilage had defects of 10 mm (area 0. 78 cm2) and 12 mm (area 1. 13 cm2). (2) The stress change trend of the cartilage of the medial condyle of the knee joint under the condition of different diameter defects was calculated based on the analysis of the application of three-dimensional finite element method. (3) Results suggest that the defect with the diameter of 10 mm (area 0. 78 cm2) of medial femoral condyle may be the minimum diameter advised for operation intervention of cartilage repair.
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BACKGROUND: Bisphosphonates are a novel inhibitor of bone resorption that can inhibit the activity and function of osteoclasts. OBJECTIVE: To observe the effects of sodium ibandronate on the expression of dentin matrix protein 1, Caspace3, Bcl-2 and Bax in condylar cartilage in osteoporosis rats. METHODS: Thirty-six female rats were randomly divided into sham group, osteoporosis group and sodium ibandronate group, twelve in each group. The sham group did not excise ovaries during surgery. Bilateral ovaries of rats were removed in the osteoporosis and sodium ibandronate groups. On the 7th day after operation, rats in the sodium ibandronate group were intraperitoneally given sodium ibandronate 10 µg/kg, once every 7 days. After 90 days, the rat ovaries were taken. Bone mineral density was measured in each group. The changes of condylar cartilage were observed by toluidine blue staining and TUNEL staining. The expression of dentin matrix protein 1 protein was detected by immunohistochemistry. The levels of Caspase3, Bcl-2 and Bax were detected by western blot assay. The study protocol was approved by the Animal Ethics Committee of Nanhua Hospital in China with the approval No. SLXD_201804010. RESULTS AND CONCLUSION: Compared with the sham group or sodium ibandronate group, the bone mineral density in the osteoporosis group was significantly decreased (P < 0.05). The results of toluidine blue staining showed that the hypertrophic layer of condylar cartilage in the sodium ibandronate group was significantly thicker than that in the osteoporosis group. Compared with the sham group or sodium ibandronate group, the number of apoptotic cells in condylar cartilage and subchondral bone increased significantly in the osteoporosis group (P < 0.05). The expression of dentin matrix protein 1 protein was significantly lower in the osteoporosis group than the sham group, but it increased after treatment with sodium ibandronate (P < 0.05). Compared with the sham group, the expression of Caspase 3 and Bax in the osteoporosis group increased significantly, and the expression of Bcl-2 decreased. However, treatment with sodium ibandronate decreased the expression of Caspase 3 and Bax and increased the expression of Bcl-2 significantly. Overall, our findings reveal that sodium ibandronate can inhibit the apoptosis of condylar chondrocytes and the number of osteoclasts in osteoporotic state, which may be related to the regulation of Caspase 3, Bcl-2, Bax and dentin matrix protein 1 expression.
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Objective: To study the effects of estrogen on the degenerative changes of condylar cartilage and subchondral bone in rats. Methods: 18 female SD rats aged 6 weeks were divided into control(C),unilateral anterior cross-bite(UAC) and UAC treated with estrogen(UAC + E) groups(n = 6). UAC metal prosthesis was cemented to the left incisors of maxilla and mandible of the rats in group UAC and UAC + E. Rats in UAC + E group were given pexitoneal injection of 80 μg 17β-estradiol per day. The rats in group C were untreated. Animal were sacrificed at the 4th weeks. The micro-structure of subchondral bone was observed by Micro-CT scanning. HE staining,Safranin O staining,immunohistochemical staining,TUNEL staining and TRAP staining for the observation of pathological changes of histomorphology,extracellular matrix,chondrocyte apoptosis in condylar cartilage,and osteoclasts number in subchondral bone. Results: UAC and UAC + E group showed evident osteoarthritis(OA)-like lesions. Compare with UAC group,there was a significant decrease in the expression of proteoglycan(P ＜ 0. 05),type Ⅱ collagen(P ＜ 0. 01),and a significant increase in the number of apoptotic chondrocytes(P ＜ 0. 01) in UAC + E group. As for subchondral bone,the BV/TV,Tb. Th parameters in C and UAC + E groups were significant higher than in UAC group(P ＜ 0. 01),while the BS /BV,Tb. N,Tb. Sp parameters and the osteoclasts number in C and UAC + E groups were significant fewer than in UAC groups(P ＜ 0. 01). There was no significant difference in bone ultra-parameters and osteoclasts number between C and UAC + E groups(P＞ 0. 05). Conclusion: In the model of rat TMJOA induced by unilateral anterior crossbite prosthesis,supra-physiological level of estrogen can reverse bone loss in subchondral bone,but accelerate the degradation of condylar cartilage.
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Objective:To study the effects of hyaluronic acid(HA) and TGF-β1 on the growth of mandibular condylar cartilage and the hyperthophic differentiation of the condylar chondrocyts.Methods:60 condyle samples from newborn mice were in vitro cultured and treated with HA(0.5 mg/ml),TGF-beta 1 (5 ng/ml) and without additional agent(the control) respectively.The Morphological observation,Alizarin Red Staining,Alkaline phosphatase staining and condylar cartilage surface area measurement were conducted after 1,2,4,6 and 8 weeks of culture respectively.Results:High-density photoresist area was observed in the condylar cartilage of the control group after 4 weeks of culture.Alizarin Red Staining and Alkaline phosphatase staining showed condylar cartilage matrix production and calcification.The HA group showed no high-density photoresist area at all time points,however,the cartilage area was significantly increased (P ＜ 0.05);the TGF-beta 1 group showed high-density photoresist area after 2 weeks of culture.but the cartilage area were not significantly changed(P ＞ 0.05).Conclusion:HA can promote the growth of condylar cartilage in vitro,but have an inhibitory effect on chondrocyte differentiation.TGF-β1 plays a role in mandibular condylar chondrocyte hypertrophic differentiation in the early days of in vitro culture.
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<p><b>OBJECTIVE</b>To determine the influence of altered masticatory loading on Indian hedgehog (Ihh)-parathyroid hormone-like related protein (PThrP) pathway in the condylar cartilage of growing rabbits.</p><p><b>METHODS</b>A total of 48 10-day-old rabbits were randomly divided into two groups and fed different kinds of food, such as solid diet and soft diet. The animals were sacrificed after 2, 4, 6, and 8 weeks. Difference of Ihh and PThrP expression levels induced by altered masticatory loading was tested by hematoxylin-eosin (HE), immunohistochemistry, Western blot, and real-time polymerase chain reaction (PCR).</p><p><b>RESULTS</b>The thickness of condylar cartilage and expression levels of Ihh and PThrP proteins and mRNA of the solid diet groups exceeded those of the soft diet groups. The decreasing tendencies of the expression levels of Ihh and PThrP proteins and mRNA were observed at 2, 4, 6, 8 weeks.</p><p><b>CONCLUSIONS</b>Low masticatory loading may delay or inhibit the development of condylar cartilage and its growing factors Ihh and PThrP. Therefore, masticatory loading plays an important role in the development of condylar cartilage.</p>
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Animals , Rabbits , Blotting, Western , Cartilage , Chondrocytes , Hedgehog Proteins , Immunohistochemistry , Mastication , Parathyroid Hormone , Real-Time Polymerase Chain ReactionABSTRACT
The condylar cartilage was adapted to hypoxic conditions in vivo. However, condylar cartilage cells exposed in normoxia in vitro affect the chondrocyte phenotype and cartilage matrix formation. This condition also resulted in great difficulty in chondrocyte research. Culturing chondrocyte should be simulated in in vivo hypoxia environment as much as possible. The hypoxia-inducible factor-1α (HIF-1α) demonstrates an important transcription factor of adaptive response to hypoxic conditions. HIF-1α also plays an active role in maintaining homeostasis and function of chondrocytes. This review summarized current knowledge of the HIF-1α structure, signaling pathway, and mechanism of HIF-1α in the condylar cartilage repair.
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Humans , Cartilage , Chondrocytes , Hypoxia , Hypoxia-Inducible Factor 1, alpha Subunit , Signal TransductionABSTRACT
Objective To observe the dynamic histological changes of condylar cartilage ,and detect expression of estrogen re‐ceptors and collagen typeⅡin the ovariectomized rat ,exploring the relationship between OA and abnormity of shorting estrogen . Methods Histological changes of condylar cartilage of the ovariectomized rat at different ages were observed by HE staining meth‐od .The expression of estrogen receptors and collagen typeⅡwere determined by immunohistochemical method ,and the average per‐centage of positive staining area was measured by image analyzer .Results The lack of estrogen led to the degeneration of condylar cartilage .The expression of ER and ColⅡ were suppressed at low concentration of estrogen ,and these effects were enhanced when the treating time was prolonged .Conclusion The lack of estrogen might lead to the rat′s condylar cartilage lesion ,and the low con‐centration of estrogen could suppress the expression of ER .These results highlight the results that expression of condylar cartilage collagen is associated with estrogen .
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Objective To examine the distribution and expression of dentin matrix protein1 ( DMP1 ) in the condylar cartilage and subchondral bone of osteoporosis rats. Methods Female Sprague-Dawley rats aged 6 months (n=30)wererandomlydividedinto3groups. TheShamgroupunderwentshamoperationonly(n=10),theOVX group ( n = 10 ) received a bilateral ovariectomy first and then saline solution treatment subcutaneously for 3 months. The RIS group ( n=10 ) also received a bilateral ovariectomy and then with risedronate treatment ( 2. 4μg/kg) subcutaneously for 3 months. Three months after the operation, the animals were sacrificed. Toluidine blue staining showed the structure changes of rat condylar cartilage region. The changes of osteoclasts in the bony subcondylar region were evaluated by tartrate-resistant acid phosphatase ( TRAP) staining. The expression of DMP1 was analyzed immunohistochemically and then performed by semi-quantitative imaging analyses. Results Toluidine blue staining showed a thickened hypertrophic layers of condylar cartilage in RIS group. The results of TRAP staining indicated that the number of osteoclasts was significantly greater in OVX group than RIS group (P<0. 05). Immunohistochemistry showed that DMP1 localized mainly in the chondrogenic layers and osteocytes, bony subcondylar region in three groups. The expression levels of DMP1 proteins statistically decreased in OVX group than the other two groups(both P<0. 05). Conclusion Bisphophonates may reduce the the number of osteoclasts in the condyle from osteoporosis rats, with increasing of the expression of DMP1, which may influences condylar cartilage biomineralization.
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Objective:To investigate hypoxia location in condylar cartilage in the early growth stage of rats.Methods:40 Sprague-Dawley rats were breastfed from 1 4 d to 21 d of age.1 0 rats were sacrificed at 1 2,24,48 and 96 h respectively after initiation of normal food at 21 d of age.The rats were administered pimonidazole hydrochloride (HP-1 )at a dose of 60 mg/kg by intraperitoneal injection 2 h before sacrifice.The expression of HP-1 in the whole condylar cartilage was detected by immunohistochemical staining.Results:HP-1 was mainly expressed in the chondrocytes of the fibrous and proliferative layer of cartilage,primarily concentrated in the weight-bearing area of joint-anterior aspect of the condyle and posterior aspect of the articular eminence at all time points.The highest expres-sion was observed at 24 h after initiation of normal food (P <0.01 ).Conclusion:In the early growth stage of rats,dietary loading may directly induce hypoxia in uper layer of condylar cartilage,the hyoxia level may change with time of dietary loading.
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Objective To investigate the effect of the asymmetric of masticatory force on the remodeling of bilateral mandibular condylar cartilage of SD rats. Methods The animal models were established respectively by excising the unilateral temporalis, and injecting botulinum toxin A into the unilateral masseter. Dividing three batch processing 3 weeks, 6 weeks, and 9 weeks after the animal modeling, six rats were killed in each group. The expression of CTGF in condylar cartilage was observed by immunohistochemical staining. Results CTGF expressed in proliferative layer,chondroblast layer and hypertrophic layer of the condylar cartilage. The expression of CTGF in the experimental groups was increased than control groups (0.05), the expression of CTGF after 6 weeks of operation was stronger than the group after 3 weeks of operation, the expression of CTGF after 9 weeks of operation was the strongest than all of other groups ( <0.05) . Conclusions The asymmetric of masticatory force can up-regulate the expression of CTGF mRNA in rat mandibular condylar chondrocytes. CTGF induces the effect of stress-mediated on the mandibular condylar cartilage remodeling.
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Objective:To examine the relation between the alteration of condylar endochondral in response to mandibular protrusion and the action time length by establishing a model of mandibular protrusion on young adult rats. Methods: 75 female Sprague-Dawley rats aged 9 weeks were divided into two experimental groups and one control group. In two experimental groups, bite jumping appliances created forward positioning of the condyle for twelve hours and whole day, respectively. The experimental rats, together with the control rats, were sacrificed on days 3, 7, 14, 21 and 30, respectively. Tissue sections were cut in the sagittal plane through the mandibular condyle and were processed for in situ hybridization and immunostaining of type X collagen. Results: The peak of type X collagen protein expression in 24-hour experimental groups appeared on day 21 which was on the top of all experimental groups, while in 12-hour experimental groups it was found on day 30. The results of in situ hybridization were basically in agreement with the results of immunostaining. Conclusion: Both intermittent and continuous mandibular advancement can provoke endochondral ossification in young adult rat condylar, while 24-hour ones can produce more obvious and quicker effect.
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To elucidate the histological findings of the anlage of the mandibular condyle during very early developmental stages, we analyzed sagittal and frontal plane serial sections of mouse fetuses for which the gestational period was precisely determined. An aggregate of mesenchymal cells around the buccal nerve (peripheral cell aggregate) could be seen at 12.0 days post-conception (dpc). Another cell aggregate (core cell aggregate), which almost coincided with the outline of the condylar head, was detected on the inside of the dome-shaped peripheral cell aggregate at 12.75 dpc. The cells of the peripheral cell aggregate were gradually flattened in accordance with cell differentiation, and formed a fibrous sheath covering the condylar head by 15.0 dpc. The cells of the central region of the core cell aggregate differentiated into hypertrophic chondrocytes by 14.5 dpc, whereas the cells of the fringe of the core cell aggregate differentiated into osteogenic cells to form the bone collar by 15.0 dpc. The continuity of the anlage of the condyle with that of the mandibular ramus was first recognized at 13.0 dpc. As the anlage of the mandibular condyle was observed histologically during very early developmental stages, further research is necessary to characterize the development of this anlage in greater detail.
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Objective To elucidate the relationship between mandibular lateral displacement and mandible asymmetry by observing the morphological changes of condylar head and mandible during mandibular lateral displacement in growing rats.Methods Forty-eight male Wistar rats at the age of four weeks were divided at random into experimental and control groups,with 24 rats in each group.A super-hard resin plate was cemented to upper incisors to displace rat mandibles 2 mm to the left during closure(Ipsilateral side).A metal crown was fitted to lower incisors.The rats were killed 2,4,8 or 12 weeks after appliance attachment.The mandible was dissected out and halved.The length and width of condylar head were measured with a caliper.Radiographic films of the mandibles were exposed,and selected measurements were made.Results The length of condylar cartilage on the ipsilateral side was significantly larger than contralateral side in experimental group(P
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PURPOSE: This study was undertaken to quantitatively estimate the degree of the damage and recovery of the irradiated rat condylar cartilage using the Image Analyzer. MATERIALS AND METHODS: Experimental animals were 16 male rats of the Sprague-Dawley strain at the age of 20 day irradiated with the dose of 10 Gy in their head and neck region. Four rats were sacrificed at the each of the
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Animals , Humans , Male , Rats , Cartilage , Extracellular Matrix , Head , Mandibular Condyle , Neck , Rats, Sprague-Dawley , Tolonium ChlorideABSTRACT
This investigation examined the effect of lateral shift of mandible from functional occlusal interference on the growth of mandible and the growth pattern of mandible shown after the removal of occlusal interference. The followings were performed with the results below : the changes in mandible and condylar cartilage were studied in the experimental group with upper right, lower left incisors cut for 2 and 4 weeks- an 4-week-old rats and the experimental group which had cut for 4 weeks and suspended for 2 weeks. 1. In the 2-week experimental group, the left mandibular length, condylar length, mandibular height and condylar area seemed smaller than those on the right and the normal group ; the right mandibular length and condylar area were smaller than the normal group. 2. In the 4-week experimental group, left condylar area was smaller than the right, but due to the quick changes in adaptability of left mandible, right and left mandibular lengths were similar. compared with the normal group, however, mandibular length and condylar area still remained small. 3. In the 6-week experimental group, the left and the right appeared similar with the mandibular length remaining still shorter than the normal group. 4. In the sagittal plane, the proliferation of the cartilage layers of the left condylar cartilage of the 2-week group appeared to have general repression compared with the right and the normal group. The right side also showed repressed growth compared with the normal group. In the 4 and 6-week groups, however, it was similar to the normal group. 5. In condylar cartilage volume, no significant difference was noted in the comparisions of left and right of the experimental group, nor in the comparison of the same sides of experimental wand normal groups. Based on the above, in case of contralateral incisal cutting in rats, it was observed that the growth of mandible and condyle of the cutting side was repressed , at the same time, the quick adaptability led to similar changes of growth in left and right mandibles. But judging fiuui the similar phenomena throughout the whole experimental period in the changes of condylar cartilage volume in the experimental, right and left, and normal groups, the general overall growth of condylar cartilage was found unrepressed. It was also recognized that the growth of condylar cartilage can take in various directions.
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Animals , Rats , Cartilage , Incisor , Mandible , Repression, PsychologyABSTRACT
Objective:To examine the relation between the alteration of condylar endochondral in response to mandibular protrusion and the action time length by establishing a model of mandibular protrusion on young adult rats.Methods:75 female Sprague-Dawley rats aged 9 weeks were divided into two experimental groups and one control group.In two experimental groups,bite jumping appliances created forward positioning of the condyle for twelve hours and whole day,respectively.The experimental rats,together with the control rats,were sacrificed on days 3,7,14,21 and 30,respectively.Tissue sections were cut in the sagittal plane through the mandibular condyle and were processed for in situ hybridization and immunostaining of type X collagen.Results:The peak of type X collagen protein expression in 24-hour experimental groups appeared on day 21 which was on the top of all experimental groups,while in 12-hour experimental groups it was found on day 30.The results of in situ hybridization were basically in agreement with the results of immunostaining.Conclusion:Both intermittent and continuous mandibular advancement can provoke endochondral ossification in young adult rat condylar,while 24-hour ones can produce more obvious and quicker effect.
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The purpose of this study was to evaluate the effect of intrinsic factor and extrinsic factor for growth of the mandibular condylar cartilage of 4 day-old rats In a serum-tree medium for 1, 4, 7,14 days. They were compared with normal growth in vivo and with growth of spheno-occipital synchondrosis in serum-free medium. The cellular kinetics of cartilages were evaluated by autoradiography of tritiated thymidine. 1. Condylar cartilage was enlarged with rounded head on day 14 of experiment while in vivo the rounded-headed shape changed into functionally flattened appearance. 2. On day 14 of experiment, a severe reduction of the proliferative zone and a considerable increase of the hypertrophic zone were observed while in normal control group endochondrol bone formation and bone marrow were observed. 3. The proliferative activity in the proliferative zone of condylar cartilage detected by 3H-thymidine incorporation was lower than that of normal control group and decreased more than that of spheno-occipital synchondrosis, but it continued during the 14 days of culture. 4. The continued maintenance of condylar cartilage and morphologic change were disturbed in this culture system, but cell division within the proliferative zone was continued and probably linked to intrinsic factor.