Development of Partial-thickness Articular Cartilage Injury in a Rabbit Model

In humans, partial-thickness cartilage lesions frequently result in premature osteoarthritis. While rabbits often are used as a model for partial-thickness cartilage lesions, the natural course of cartilage surrounding such a lesion is largely unknown. We developed a rabbit model of a chronic partial-thickness cartilage defect and asked whether these defects led to (1) deterioration of surrounding cartilage macroscopically and microscopically (increased Mankin score) and (2) disturbances in proteoglycan metabolism. In 55 rabbits, we created a 4-mm-diameter partial-thickness cartilage defect on one medial femoral condyle. The surrounding cartilage was characterized during the course of 26 weeks. Contralateral knees were sham-operated. In experimental knees, we found cartilage softening and fibrillation at 13 and 26 weeks. High Mankin scores observed at 1 week were partially restored at 13 weeks but worsened later and were most pronounced at 26 weeks. Mankin scores in the experimental groups were worse at 1 and 26 weeks when compared with the sham groups. Mankin scores at 26 weeks improved compared with 1 week in the sham groups. Disturbances in proteoglycan metabolism were less evident. In this rabbit model, a partial-thickness cartilage lesion resulted in early markers of degenerative changes resembling the human situation. Each author certifies that he has no commercial associations (e.g., consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. Each author certifies that his or her institution has approved the animal protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.     

活性维生素D3对体外原代培养人骨关节炎软骨细胞的影响

目的探讨不同浓度的1α,25二羟基维生素D3[1,25-（OH）2D3]对体外培养的人骨关节炎患者关节软骨细胞的增殖及凋亡率的影响。方法酶二步消化法体外分离培养人软骨细胞,以碱性磷酸酶染色法鉴定。加入不同剂量的[1,25-（OH）2D3],通过噻唑蓝比色试验检测细胞存活和增殖情况,以及用流式细胞仪检测软骨细胞在不同药物浓度、不同作用时间的凋亡率。结论 [1,25-（OH）2D3]作用于人骨关节炎软骨细胞的最佳作用浓度为1×10-5umol/L,最佳作用时间点为48 h。高浓度的[1,25-（OH）2D3]能明显促进细胞坏死,极低浓度的[1,25-（OH）2D3]对软骨细胞增殖、凋亡无明显影响。     

Low Vitamin D Levels in Children with Fractures: a Comparative Cohort Study

Background

The currently accepted ranges for “normal” serum vitamin D have recently been challenged in adults on the basis that healthy bone metabolism requires higher levels of vitamin D than previously thought.

Purpose

The purpose of this study was to evaluate whether a new “biologically based” classification based on 25(OH)vitamin D levels that invoke an endocrine biomarker response (<20 ng/mL for deficiency and <32 ng/mL for insufficiency) is more appropriate for children with fractures than historical criteria.

Methods

Serum 25(OH)vitamin D levels were collected from 58 children with acute low-energy fractures from an outpatient orthopedic clinic from 2009 to 2012. These vitamin D levels were compared with a cohort of 103 children with chronic kidney disease (CKD) from an adjacent clinic, a condition with acknowledged low levels of vitamin D. Then, the prevalence of vitamin D sufficiency in the fracture cohort was evaluated and compared using both historical guidelines and newer biologically based criteria.

Results

25(OH)vitamin D levels in the fracture cohort did not differ from levels in the CKD cohort (27.5 vs. 24.6 ng/mL) indicating a similar distribution of vitamin D levels. This finding was consistent when controlling for significant covariables using linear regression analyses. In the fracture cohort, there was a discrepancy between historical and biologically based criteria in 64% of children.

Conclusions

The results of the current study suggest that fracture patients are more frequently vitamin D deficient than previously thought. This finding is more readily apparent when newer biologically based criteria for vitamin D sufficiency are used.

Electronic supplementary material

The online version of this article (doi:10.1007/s11420-015-9447-7) contains supplementary material, which is available to authorized users.     

应力导致关节软骨退变机制的实验研究

目的　本实验的目的是探讨应力导致关节软骨退变的病理过程与生物力学机制。方法　以 32只中国白兔为实验对象 ,在关节面施以持续高 低压应力 ,观察 4、12周 ,用组织学、组织化学、免疫组化及透射电镜为方法 ,分析退变软骨。结果　低压应力引起的退变首先表现为早期软骨细胞功能减退 ,软骨细胞代偿增生反应轻 ,然后基质破坏 ,最终导致整个软骨退变。高压应力引起的退变首先是早期基质破坏 ,软骨细胞代偿增生同时发生 ,继而软骨细胞退变 ,最终整个关节软骨退变。细胞因子主要在退变软骨的浅、移行层软骨细胞胞浆内阳性染色 ,偶可在浅层细胞近周及裂隙处见基质阳性染色。结论　高、低压应力均可导致关节软骨退变 ,低压应力首先引起软骨细胞退变 ;高压应力首先引起基质破坏。退变软骨的软骨细胞可异常合成、分泌细胞因子 ,细胞因子在软骨退变中发挥作用。     

Deleterious Effects of Intermittent Recombinant Parathyroid Hormone on Cartilage Formation in a Rabbit Microfracture Model: a Preliminary Study

Intermittent parathyroid hormone administration can enhance fracture healing in an animal model. Despite the success of exogenous parathyroid hormone on fracture healing and spine fusion, few studies have examined the role of parathyroid hormone on cartilage formation. We determined the effects of intermittent parathyroid hormone on cartilage formation in a rabbit microfracture model of cartilage regeneration. Twelve rabbits were divided into three equal groups: (1) microfracture alone, (2) microfracture + parathyroid hormone daily for 7 days, and (3) microfracture + parathyroid hormone for 28 days. Nonoperated contralateral knees were used as controls. The animals were sacrificed at 3 months and gross and histologic analysis was performed. The microfracture alone group demonstrated the most healing on gross and histologic analysis. Treatment with either 1 or 4 weeks of parathyroid hormone inhibited cartilage formation. Although discouraging from a cartilage repair point of view, this study suggests that the role parathyroid hormone administration has in clinical fracture healing must be examined carefully. Although parathyroid hormone is beneficial to promote healing in spine fusion and midshaft fractures, its deleterious effects on cartilage formation suggests that it may have adverse effects on the outcomes of periarticular fractures such as tibial plateau injuries that require cartilage healing for a successful clinical outcome.     

bFGF对关节软骨缺损的修复作用

目的观察碱性成纤维细胞生长因了对关节软骨缺损修复的影响。方法在兔双侧股骨髁间窝造成骨软骨缺损．一侧应用碱性成纤维细胞生长因子．另一侧作对照。术后3个月．利用组织切片及扫描电镜等方法，观察两侧骨软骨缺损修复情况。结果修复3个月后．对照侧软骨缺损难以完全修复．修复细胞形态多样，似成纤维细胞。蛋白多糖颗粒较少。应用碱性成纤维细胞生长因子删软骨缺损基本修复．修复细胞似软骨细胞．有较多的蛋白多糖颗粒与胶原纤维结合。缺损修复组织评分。碱性成纤维细胞生长因子组优于对照组。结论碱性成纤维细胞生长因子可促进骨软骨缺损的修复。     

Effect of Vitamin D Metabolites and Analogs on Renal and Intestinal Calbindin-D in the Rat

The effects on renal and intestinal calbindin-D of vitamin D₃ metabolites and synthetic 20-epi-vitamin D₃ analogs with different calcemic actions were examined in Wistar rats. The compounds were administered intraperitoneally once daily for 5 days. The dosages of the metabolites were 1,25-(OH)₂D₃ 0.01, 0.05, 0.1, and 0.4 μg/kg × d, 24,25-(OH)₂D₃ 0.1, 1 and 10 μg/kg × d, and 25-(OH)D₃ 10 and 400 μg/kg × d. The dosage of the synthetic analogs were MC903 0.1, 10, and 100 μg/kg × d, EB1213 0.1 and 10 μg/kg × d, KH1060 0.1 and 0.4 μg/kg × d, and GS1725 0.01 and 0.1 μg/kg × d. Two control groups had either vehicle alone or no treatment. N= 8 in each group. 1,25-(OH)₂D₃ increased renal and intestinal calbindin-D levels, induced hypercalcemia, and suppressed plasma PTH and magnesium concentrations. 24,25-(OH)₂D₃ increased intestinal calbindin-D9k and plasma calcium, but had no effect on renal calbindin-D28k, plasma PTH, and magnesium. The dosage of 24,25-(OH)₂D₃ that was required to increase plasma calcium was larger than the dosage required to increase intestinal calbindin-D9k. 25-(OH)D₃ did not change the calcium metabolic parameters. MC903, a low calcemic analog with a relative high affinity for the vitamin D receptor and a short half-life, increased renal calbindin-D28k without increasing ionized calcium or intestinal calbindin-D9k. EB1213, an analog with a reduced calcemic action and short half-life, increased renal calbindin-D28k and ionized calcium without increasing intestinal calbindin-D9k. The effect of the high calcemic vitamin D analogs KH1060 and GS1725 on calbindin-D was directly related to their calcemic activity. In conclusion, these results demonstrate that 24,25-(OH)₂D₃ increases intestinal calbindin-D9k, but has no effect on renal calbindin-D28k, that low calcemic analogs may increase renal calbindin-D28k without increasing intestinal calbindin-D9k, and that the effect of high calcemic analogs on calbindin-D is directly related to their calcemic activity. Received: 26 May 1995 / Accepted: 29 February 1996     

MMP-3/TIMP-1在大鼠肢体再灌注后关节软骨损伤的作用

目的　探讨缺血再灌注后关节软骨中MMP - 3/TIMP - 1比例变化与软骨损伤的关系。方法　采用大鼠后肢股动脉夹闭的方法模拟缺血再灌注的动物模型 ,用Wistar大鼠 4 0只 ,随机分成正常对照组 (NG)、肢体单纯缺血组 (IG)和缺血再灌注组 (IR)。运用免疫组化技术 ,分别测定TIMP - 1和MMP - 3在关节软骨中不同时相的表达变化并进行半定量分析 ,观察关节软骨病理改变及蛋白多糖 (PG)的变化。结果　缺血再灌注后 ,关节软骨中的MMP - 3和TIMP - 1表达均有增加 ,但MMP - 3增加的幅度大于TIMP ,导致MMP - 3/TIMP - 1比值增大 ,与再灌注后引起的关节软骨损伤相关。结论　MMP/TIMP的失平衡表达是导致缺血再灌注后关节软骨损伤的重要因素     

Genetic Regulation of Vitamin D Levels

Vitamin D plays several roles in the body, influencing bone health as well as serum calcium and phosphate levels. Further, vitamin D may modify immune function, cell proliferation, differentiation, and apoptosis. Vitamin D deficiency has been associated with numerous health outcomes, including bone disease, cancer, autoimmune disease, infectious disease, type 1 and type 2 diabetes, hypertension, and heart disease, although it is unclear whether or not these associations are causal. Various twin and family studies have demonstrated moderate to high heritability for circulating vitamin D levels. Accordingly, many studies have investigated the genetic determinants of this hormone. Recent advances in the methodology of large-scale genetic association studies, including coordinated international collaboration, have identified associations of CG, DHCR1, CYP2R1, VDR, and CYP24A1 with serum levels of vitamin D. Here, we review the genetic determinants of vitamin D levels by focusing on new findings arising from candidate gene and genomewide association studies.     

Calcification of Aging Articular Cartilage in Man

Calcification of the articular cartilage was studied ultrastructurally using normal femoral heads obtained from necropsies of persons ranging in age from 11 months to 80 years. Mineral crystals which appeared during the initial stages of deposition were morphologically divided into two types. Type A crystals were slender, twisted and curved, measuring from 100 nm to 360 nm in length. Type B crystals were short, needle-like and slightly curved, measuring from 30 nm to 160 nm in length. Type A crystals were found mainly in the developing epiphysis during childhood. Type B crystals were generally found in the calcified zone of adult articular cartilage. Both types of crystals initially appeared in close proximity to extracellular membrane-invested electron dense particles called “matrix vesicles”, and gradually increased in number to form calcified cartilage matrix. The morphological differences between type A and B crystals might be caused by biochemical alterations of the cartilage matrices and/or biomechanical changes in the joints of children and adults.     

Effects of Loading Conditions on Articular Cartilage in a Metal‐on‐Cartilage Pairing

The aim of this in vitro study was to investigate the response of articular cartilage to frictional load when sliding against a metal implant, and identify potential mechanisms of damage to articular cartilage in a metal‐on‐cartilage pairing. Bovine osteochondral cylinders were reciprocally slid against metal cylinders (cobalt–chromium–molybdenum alloy) with several variations of load and sliding velocity using a microtribometer. The effects of different loads and velocities, and the resulting friction coefficients on articular cartilage, were evaluated by measuring histological and metabolic outcomes. Moreover, the biotribocorrosion of the metal was determined. Chondrocytes stimulated with high load and velocity showed increased metabolic activity and cartilage‐specific gene expression. In addition, higher load and velocity resulted in biotribocorrosion of the metal implant and damage to the surface of the articular cartilage, whereas low velocity and a high coefficient of friction increased the expression of catabolic genes. Articular cartilage showed particular responses to load and velocity when sliding against a metal implant. Moreover, metal implants showed tribocorrosion. Therefore, corrosion particles may play a role in the mechano‐biochemical wear of articular cartilage after implantation of a metal implant. These findings may be useful to surgeons performing resurfacing procedures and total knee arthroplasty. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 37:2531–2539, 2019