Distinct osteogenic mechanisms of bones of distinct origins

Mammalian bones have three distinct origins (paraxial mesoderm, lateral plate mesoderm, and neural crest) and undergo two different modes of formation (intra-membranous and endochondral). Bones derived from the paraxial mesoderm and lateral plate mesoderm mainly form through the endochondral process. During this process, hypertrophic chondrocytes play a vital role in inducing both osteogenesis and angiogenesis. One of the essential osteogenic factors secreted from hypertrophic chondrocytes is Indian hedgehog (Ihh). In contrast, bones derived from the neural crest mainly form through the intramembranous pro-cess and do not require Ihh. Thus, depending on their origin, bones have distinct signaling properties, which need to be considered in the research and application of bone biology.Presented at the 18th Annual Research Meeting of the Japanese Orthopaedic Association, Kitakyushu, Japan, October 17, 2003     

Cyclic tensile stretch load and oxidized low density lipoprotein synergistically induce lectin-like oxidized ldl receptor-1 in cultured bovine chondrocytes, resulting in decreased cell viability and proteoglycan synthesis.

Mechanical stimulation is known to be an essential factor in the regulation of cartilage metabolism. We tested the hypothesis that expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) can be modulated by cyclic tensile stretch load in chondrocytes. Cyclic loading of repeated stretch stress at 10 cycles per minute with 10 kPa of stress for 6 h induced expression of LOX-1 to 2.6 times control in cultured bovine articular chondrocytes, equivalent to the addition of 10 microg/mL oxidized low density lipoprotein (ox-LDL) (2.4 times control). Application of the cyclic load to the chondrocytes along with 10 microg/mL ox-LDL resulted in synergistically increased LOX-1 expression to 6.3 times control. Individual application of cyclic loading and 10 microg/mL ox-LDL significantly suppressed chondrocytes viability (84.6% +/- 3.4% and 80.9% +/- 3.2% of control at 24 h, respectively; n = 3; p < 0.05) and proteoglycan synthesis [81.0% +/- 7.1% and 85.7% +/- 5.2% of control at 24 h, respectively; p < 0.05 when compared with 94.6% +/- 4.6% for native-LDL (n = 3)]. Cyclic loading and 10 microg/mL ox-LDL synergistically affected cell viability and proteoglycan synthesis, which were significantly suppressed to 45.6% +/- 4.9% and 48.7% +/- 6.7% of control at 24 h, respectively (n = 3; p < 0.01 when compared with individual application of cyclic loading or 10 microg/mL ox-LDL). In this study, we demonstrated synergistic effects of cyclic tensile stretch load and ox-LDL on cell viability and proteoglycan synthesis in chondrocytes, which may be mediated through enhanced expression of LOX-1 and which has important implications in the progression of cartilage degeneration in osteoarthritis.     

鹿茸生长素对家兔关节软骨细胞代谢的影响

目的 研究鹿茸生长素对关节软骨细胞增殖的影响。方法 采用家兔关节软骨细胞体外培养和加入同位素3H—TdR标记方法，观察其对3H—TdR掺入细胞DNA合成的影响。结果 加入鹿茸生长素组的3H—TdR的掺入值与对照组有明显差异，细胞增殖作用明显。结论 鹿茸生长素能明显刺激关节软骨细胞的增殖。     

An ultrastructural study of cartilage resorption at the site of initial endochondral bone formation in the fetal mouse mandibular condyle

An ultrastructural study was undertaken on cartilage resorption at the site of initial endochondral bone formation in the mouse mandibular condyle on d 16 of pregnancy. After resorbing the bone collar, the osteoclasts extended their cell processes into the cartilage matrix and made contact with hypertrophic chondrocytes. By means of cell processes or vacuolar structures, these osteoclasts entrapped the calcified cartilage matrices, cell debris, and the degraded uncalcified cartilage matrices. In particular, since the calcified cartilage matrices were sometimes seen to be disrupted within the osteoclastic vacuolar structures, they were probably disposed of by the osteoclasts. Invading endothelial cells giving rise to capillaries also directly surrounded the degraded uncalcified cartilage matrices and small deposits of cell debris. In addition, hypertrophic chondrocytes that had attached to or were in the process of attaching to the invading osteoclasts often enclosed the small calcified cartilage matrices. Other cell types that have often been reported in other regions of cartilage resorption were not seen at the site of initial endochondral bone formation in this study. Our findings in relation to cartilage resorption may therefore represent unique features of the site of initial endochondral bone formation site. We consider that the manner of cartilage resorption is likely to vary by site, age, and species.     

Expansion of human nasal chondrocytes on macroporous microcarriers enhances redifferentiation

Articular cartilage has a limited capacity for self-repair. To overcome this problem, it is expected that functional cartilage replacements can be created from expanded chondrocytes seeded in biodegradable scaffolds. Expansion of chondrocytes in two-dimensional culture systems often results in dedifferentiation. This investigation focuses on the post-expansion phenotype of human nasal chondrocytes expanded on macroporous gelatin CultiSpher G microcarriers. Redifferentiation was evaluated in vitro via pellet cultures in three different culture media. Furthermore, the chondrogenic potential of expanded cells seeded in polyethylene glycol terephthalate/ polybuthylene terephthalate (PEGT/PBT) scaffolds, cultured for 14 days in vitro, and subsequently implanted subcutaneously in nude mice, was assessed.

Chondrocytes remained viable during microcarrier culture and yielded doubling times (1.07±0.14 days) comparable to T-flask expansion (1.20±0.36 days). Safranin-O staining from pellet culture in different media demonstrated that production of GAG per cell was enhanced by microcarrier expansion. Chondrocyte–polymer constructs with cells expanded on microcarriers contained significantly more proteoglycans after subcutaneous implantation (288.5±29.2 μg) than those with T-flask-expanded cells (164.0±28.7 μg). Total collagen content was similar between the two groups.

This study suggests that macroporous gelatin microcarriers are effective matrices for nasal chondrocyte expansion, while maintaining the ability of chondrocyte differentiation. Although the exact mechanism by which chondrocyte redifferentiation is induced through microcarrier expansion has not yet been elucidated, this technique shows promise for cartilage tissue engineering approaches.     

Correlation of freeze-fracture and scanning electron microscopy of epiphyseal chondrocytes

Summary Chondrocytes in epiphyseal cartilage were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using freeze-fracture techniques. Freeze-fracture replicas showed large numbers of fingerlike, 0.11–0.15 m diameter, projections from the chondrocyte surface, with numerous 95–180 Å diameter intramembranous particles associated with both the cell membrane surface and these projections. With SEM, these cytoplasmic projections were also obvious, but appeared collapsed into clusters of globular-shaped projections on the surface of the chondrocytes. With freeze-fracture techniques, in which shrinkage artifacts were essentially eliminated, the cytoplasmic projections were often seen in intimate contact with the extracapsular matrix. However, with chondrocytes prepared by both SEM and conventional TEM, there was evidence of shrinkage, the cytoplasmic projections having little contact with the extracapsular matrix. These findings show that the cytoplasmic processes are not artifacts of tissue processing and provide morphological evidence in support of the hypothesis that matrix vesicles are of cellular origin.Correlation of Freeze-Fracture and Scanning Electron Microscopy of Epiphyseal Chondrocytes     

杀莠素A对兔软骨细胞增殖和产生NO的影响

研究杀莠素Ａ对ＩＬ－１抑制软骨细胞增殖和诱导ＮＯ产生的作用。方法：ＩＬ－１单独或与杀莠素Ａ共育于软骨细胞,用结晶紫染色法测定软骨细胞增殖,Ｇｒｉｅｓｓ法测定ＮＯ的产生。结果：ＩＬ－１抑制软骨细胞增殖,杀莠素Ａ剂量依赖地逆转ＩＬ－１的作用。杀莠素Ａ还能剂量依赖地抑制ＩＬ－１诱导软骨细胞产生ＮＯ。结论：杀莠素Ａ逆转ＩＬ－１换制软骨细胞增殖的作用可能是通过ＮＯ介导的。     

喹诺酮类药物对离体兔软骨细胞的毒性

目的 :评价几种喹诺酮类药物对幼龄兔软骨细胞的相对毒性 ,软骨毒性与浓度、时间、年龄的关系。方法 :采用兔软骨细胞体外培养的技术 ,观察细胞形态 ,四氮甲基唑蓝 (MTT)法评价细胞的增殖 ,二甲基亚甲蓝 (DMB)法评价细胞蛋白多糖的含量。观察环丙沙星、左氧氟沙星、氟罗沙星、帕珠沙星对 1月龄兔软骨细胞的影响 ,及环丙沙星对 1,3,5月龄兔软骨细胞的影响。结果 :喹诺酮类药物使细胞形态发生改变 ;抑制细胞的增殖的作用依次为环丙沙星 >左氧氟沙星 >氟罗沙星 >帕珠沙星 ;对蛋白多糖含量的作用为环丙沙星 >左氧氟沙星 >氟罗沙星、帕珠沙星 ;环丙沙星的抑制作用随作用时间的延长和浓度的增加而增加 ,随兔年龄的增大而减少。结论 :喹诺酮类几种药物的软骨毒性存在着差异 ,且随浓度、时间、年龄不同而不同。     

独活寄生汤含药血清通过调控SOX6对体外软骨细胞表型的影响

目的 研究大鼠独活寄生汤含药血清对体外软骨细胞表型稳定性,SOX6及培养基中细胞因子IL-1β、IL-6、TNF-α表达的影响。方法 取大鼠股骨头软骨帽,提取软骨细胞,并在体外单层传代培养。培养体系为含高、中、低浓度的独活寄生汤含药血清及生理盐水血清,通过免疫组织化学分析软骨细胞表型Ⅱ型胶原的变化及SOX6表达分布,通过Westernblot及ELISA检测SOX6、Collagen Ⅱ、Aggrecan及IL-1β、IL-6、TNF-α表达的变化。结果 不同浓度的独活寄生汤含药血清均可对体外培养的软骨细胞产生增殖促进作用,并能增加Ⅱ型胶原稳定其软骨表型;其中以中浓度最为显著（P<0.01）;与生理盐水血清组相比,独活寄生汤含药血清可以增加SOX6在细胞核的分布,而且能抑制培养基中细胞因子IL-1β、IL-6、TNF-α的表达水平。结论 独活寄生汤含药血清可以上调体外软骨细胞SOX6及抑制炎症因子的表达以稳定软骨细胞的表型。     

大鼠关节软骨细胞的培养

目的探讨大鼠关节软骨细胞培养方法。方法采用胶原酶NB4消化法从1周龄SD大鼠的关节软骨中分离出软骨细胞并进行原代和传代培养,每日在倒置显微镜下观察细胞形态及其生长情况,并用HE、甲苯胺蓝染色和Ⅱ型胶原免疫组织化学染色进行鉴定。结果软骨细胞形成单层的时间在原代培养1周左右,5d左右即可传代。第5代后部分变为梭形,第7代后绝大部分变为长梭形,增殖能力减弱。结论采用此法可在短时间内获得大量纯化的大鼠软骨细胞。