ABSTRACT
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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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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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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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.
ABSTRACT
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.