GCM1通过激活Wnt3a/β-catenin信号通路改善绝经后骨质疏松症

目的 探究GCM1对小鼠胚胎成骨细胞前体细胞（MC3T3-E1）成骨分化及矿化的影响。方法 实验设置control组、BMP2诱导组、BMP2+ov-NC组、MP2+ov-GCM1组、BMP2+sh-NC组、BMP2+sh-GCM1组,BMP2用于诱导细胞成骨分化。通过碱性磷酸酶(ALP)染色及茜素红染色检测GCM1对MC3T3-E1成骨分化及矿化的影响;通过Western blot检测成骨分化相关蛋白及Wnt3a/β-catenin蛋白的表达变化。结果 GCM1在绝经后骨质疏松症患者血清中低表达。过表达GCM1能够促进BMP2诱导MC3T3-E1的成骨分化和矿化,而抑制GCM1表达则抑制了BMP2诱导MC3T3-E1的成骨分化和矿化。此外,过表达GCM1增加了Wnt3a/β-catenin蛋白表达,激活Wnt3a/β-catenin信号通路,抑制GCM1表达则与上述结果相反。结论 GCM1在绝经后骨质疏松症患者血清中低表达,过表达GCM1则可能通过激活Wnt3a/β-catenin信号通路、促进MC3T3-E1成骨分化及矿化,进而改善绝经后骨质疏松症。     

MicroRNA-196a靶向调节HDAC9对MC3T3-E1细胞成骨分化的影响

目的 探究微小RNA（miR）-196a靶向调节组蛋白去乙酰化酶9（HDAC9）对MC3T3-E1细胞成骨分化的影响。方法 将MC3T3-E1细胞分为对照组（Cont）组、诱导组、miR-196a-mimics-NC组、miR-196a-mimics组、miR-196a-inhibitor-NC组、miR-196a-inhibitor组、miR-196a-mimics+pCMV-HDAC9-NC组、miR-196a-mimics+pCMV-HDAC9组,根据分组转染后进行成骨诱导。定量荧光PCR检测MC3T3-E1细胞中miR-196a、HDAC9表达量;试剂盒检测碱性磷酸酶（ALP）活性;茜素红染色观察矿化程度;Western blot检测HDAC9、ALP、Runt相关转录因子2（Runx2）、胶原蛋白I（COL1）、骨桥蛋白（OPN）、Histone H3、Histone H3（acetyl K9、K14和K23）表达量。结果 与Cont组相比,诱导组MC3T3-E1细胞中miR-196a表达、ALP、Runx2、COL1、OPN蛋白表达、ALP活性、矿化程度及Histone H3 K9、K14、K23位点乙酰化水平增高（P＜0.05）,HDAC9 mRNA和蛋白表达降低（P＜0.05）。转染miR-196a-mimics可明显增加miR-196a表达,降低HDAC9表达,并增加ALP、Runx2、COL1、OPN蛋白表达、ALP活性、矿化程度及Histone H3乙酰化,转染miR-196a-inhibitor则作用相反。miR-196a可靶向下调HDAC9表达,过表达HDAC9可部分逆转miR-196a mimics对MC3T3-E1细胞成骨分化的促进效应。结论 miR-196a可靶向下调HDAC9表达,增加组蛋白乙酰化水平,促进MC3T3-E1细胞成骨分化。     

健骨胶囊对成骨样细胞MC3T3-E1增殖及分化作用机制

目的 探讨国医大师刘柏龄“健骨胶囊”对MC3T3-E1成骨细胞分化及增殖的影响。方法 制备健骨胶囊水提物,采用CCK-8法和细胞迁移实验检测健骨胶囊提取物对MC3T3-E1细胞增殖和细胞迁移的影响;茜素红染色检测MC3T3-E1细胞的矿化能力;实时荧光定量PCR检测成骨分化基因Runx2、OCN、OPN、Col1a1、ALP、Bcl2、RASSF1A等mRNA表达水平;蛋白质印迹法Western blot检测Col1a1、Bcl2的蛋白表达水平。结果 通过实验结果比对得出,健骨胶囊提取物能促进MC3T3-E1细胞增殖、使细胞迁移率提高;同时健骨胶囊提取物组能明显提高MC3T3-E1细胞钙化能力(P＜0.01),促进Runx2、OCN、OPN、Col1a1、ALP、Bcl2的mRNA表达(P＜0.05),上调Col1a1、Bcl2蛋白量的表达。结论 健骨胶囊能促进成骨细胞MC3T3-E1的增殖及细胞迁移能力,并通过上调成骨基因的表达水平如Runx2、OCN、OPN、Col1a1、ALP、Bcl2等,提高MC3T3-E1细胞的成骨能力。     

组蛋白甲基转移酶2（SMYD2）抑制剂LLY-507对成骨分化的影响

目的 研究SMYD2抑制剂LLY-507对小鼠颅顶前骨细胞亚克隆14（MC3T3-E1）及人骨髓间充质干细胞（hMSCs）成骨分化的影响。方法 通过CCK-8法检测LLY-507对MC3T3-E1和hMSCs增殖的影响;采用碱性磷酸酶( ALP) 染色和活性测定检测不同浓度LLY-507干预下MC3T3-E1和hMSCs早期成骨分化标志物ALP的活性情况;通过茜素红染色及半定量分析检测LLY-507对MC3T3-E1和hMSCs矿化能力的影响;运用荧光定量PCR检测hMSCs的成骨相关基因Osterix、Runx2、OPG、OPN mRNA的表达;Western blot检测hMSCs的Runx2和SMYD2蛋白表达量。结果 CCK-8结果表明LLY-507在0.8 μmol/L的剂量下细胞活性无明显影响,不会明显抑制细胞增殖。ALP染色及活性测定表明,加入50 nmol/L及以上剂量的LLY-507干预7 d后能够明显抑制MC3T3-E1及hMSCs成骨分化以及碱性磷酸酶的表达（P<0.05）;茜素红染色及半定量分析表明100 nmol/L剂量的LLY-507能够明显抑制MC3T3-E1及hMSCs的矿化能力（P<0.05）。通过qPCR,加入25 nmol/L及以上剂量的LLY-507分别干预7 d和14 d后能够明显抑制hMSCs成骨分化相关基因Runx2、Osterix、OPG、OPN的mRNA表达（P<0.05）。通过Western blot, 加入50 nmol/L及以上剂量的LLY-507干预7 d和14 d后均能够明显抑制hMSCs的Runx2蛋白和SMYD2蛋白的表达。结论 抑制SMYD2的表达能够抑制成骨相关基因的表达,说明SMYD2在成骨分化过程中起到促进成骨的作用。     

芍药苷促进小鼠成骨分化抗骨质疏松作用的实验研究

目的 探讨芍药苷对MC3T3-E1成骨细胞分化以及小鼠骨质疏松模型的影响。 方法 体外细胞实验分为对照组、不同剂量芍药苷干预组。通过CCK-8法检测芍药苷对MC3T3-E1成骨细胞活力的影响;采用碱性磷酸酶（ALP）染色以及活性检测芍药苷促进MC3T3-E1成骨分化能力;通过茜素红染色检测芍药苷促矿化能力;运用荧光定量PCR、Western blot检测Runx2、OPG、RANKL、Col1α1的mRNA以及蛋白表达情况。选取8周龄C57BL/6小鼠24只,分为假手术组、骨质疏松模型组、药物干预组。选取各小鼠左侧股骨远端以及胫骨近端的区域进行苏木素-伊红（HE）染色、Runx2免疫组织化学以及micro-CT扫描。 结果 中、高剂量芍药苷干预组可以促进MC3T3-E1细胞ALP的活性（P<0.05）;高剂量芍药苷能够促进MC3T3-E1细胞的矿化能力（P<0.01）;同时中、高剂量能够促进OPG、Runx2蛋白的表达（P<0.05）,抑制RANKL的表达（P<0.05）。与假手术组比较,OVX组骨微结构破坏明显,Runx2蛋白表达显著减少（P<0.01）;芍药苷干预后骨质疏松模型小鼠骨小梁数量以及厚度显著增加（P<0.01）,骨小梁间隔减少明显（P<0.01）,Runx2蛋白提升明显（P<0.01）。 结论 芍药苷能够促进成骨细胞的分化,上调成骨分化基因,改善骨质疏松模型小鼠的骨微结构,具有抗骨质疏松治疗的潜在价值。     

续苓健骨汤含药血清对MC3T3-E1细胞分化及增殖的影响

目的探讨续苓健骨汤含药血清对MC3T3-E1成骨细胞分化及增殖的影响。方法制备续苓健骨汤含药血清,实验分为空白对照组、含药血清低剂量组、中剂量组和高剂量组。采用CCK-8法和流式细胞术检测续苓健骨汤含药血清对MC3T3-E1细胞增殖和细胞周期的影响;碱性磷酸酶(ALP)活性测定MC3T3-E1细胞的成骨分化能力;茜素红染色检测MC3T3-E1细胞的矿化能力;实时荧光定量PCR检测成骨分化基因Runx2、OC、Bmp2、Col1a1mRNA水平。结果与空白对照组比较,中、高剂量续苓健骨汤含药血清能促进MC3T3-E1细胞增殖、S期细胞比率和细胞增殖指数,并且呈现一定的剂量依赖性;同时中高剂量续苓健骨汤含药血清组能明显提高MC3T3-E1细胞ALP活性(P0.01)和钙化能力(P0.01),促进Runx2、OC、Bmp2、Col1a1 mRNA的表达(P0.05)。结论续苓健骨汤含药血清能促进成骨细胞MC3T3-E1的增殖,并通过上调骨形成相关基因Runx2、OC、BMP2、Col1a1的表达水平,提高MC3T3-E1细胞的成骨能力。     

黄芩素通过BMP-2/Smad通路促进MC3T3-E1成骨作用的实验研究

目的 探讨黄芩素（BAI）对小鼠胚胎成骨细胞前体细胞（MC3T3-E1）成骨分化的作用及其分子机制。方法 将MC3T3-E1分为对照组（正常培养）和BAI组（以Baicalein处理）,在成骨分化条件培养下采用CCK-8检测BAI对MC3T3-E1细胞增殖的影响;分别以碱性磷酸酶染色（ALP）、茜素红染色（ARS）检测MC3T3-E1细胞成骨分化水平与矿化能力,实时荧光定量PCR检测成骨标志基因ALP、COL1A1、RUNX2、OSX的mRNA表达水平,通过免疫印迹法（Western-blot）检测MC3T3-E1细胞中BMP-2、Smad1、p-Smad1蛋白表达水平,通过免疫荧光技术（IF）检测RUNX2、COL1A1表达水平。结果 与对照组比较,BAI干预1 d后发现,BAI组COL1A1（P<0.001）、RUNX2（P <0.05）、OSX（P <0.05） mRNA表达水平在成骨分化中表达上升;干预3 d后发现,与对照组比较,BAI组ALP（P <0.05）、RUNX2（P <0.001）mRNA表达上升;干预7 d后发现,与对照组比较,BAI组COL1A1（P <0.05）mRNA表达水平较对照组上升,BMP-2、p-Smad1/Smad1蛋白表达水平上升（P <0.05）。免疫荧光中成骨标志蛋白RUNX2、COL1A1表达增多（P <0.05）。结论 BAI可通过激活BMP-2/Smad通路促进MC3T3-E1成骨分化。     

THSD4基因在小鼠间充质干细胞及MC3T3-E1细胞成骨分化中的作用

目的 探讨THSD4基因对小鼠间充质干细胞和MC3T3-E1细胞成骨分化的影响。方法 提取绝经后骨质疏松症患者的骨髓间充质干细胞进行基因测序分析,与骨关节炎患者的骨髓间充质干细胞进行比较,分析基因表达差异。通过提取不同分化阶段的小鼠骨髓间充质干细胞（M-BMSC）及MC3T3-E1细胞的mRNA来检测THSD4 基因以及成骨分化的标志性基因（ALP、Runx2、Osx）的表达水平。通过构建慢病毒表达载体来实现对M-BMSC及MC3T3-E1细胞中THSD4的敲减及过表达,并观察其对M-BMSC及MC3T3-E1细胞成骨分化能力的影响。结果 THSD4基因在绝经后骨质疏松症患者骨髓间充质干细胞中明显下调,且通过KEGG以及GO富集分析发现THSD4基因可能与PI3K-AKT信号通路及Wnt信号通路相关。随着成骨诱导分化时间的延长,THSD4 mRNA和成骨分化标志性基因（ALP、Runx2、Osx）mRNA在MC3T3-E1以及M-BMSC中表达量均逐渐增加。过表达THSD4可以增强MC3T3-E1细胞和M-BMSC的成骨分化能力,而敲减THSD4则减弱了MC3T3-E1细胞和M-BMSC的成骨分化能力。结论 THSD4基因在绝经后骨质疏松症患者骨髓间充质干细胞中明显下调,且THSD4基因可以增强MC3T3-E1细胞以及M-BMSC的成骨分化能力。     

miR-381-3p通过靶向ERK1/2/ETS1信号通路影响MC3T3-E1细胞成骨分化

目的 探讨miR-381-3p对MC3T3-E1细胞成骨分化的影响和作用机制。方法 慢病毒转染细胞后实验分为NC mimic miR-381-3p组、mimic miR-381-3p组、NC inhibitor miR-381-3p组和inhibitor miR-381-3p组;运用实时荧光定量PCR(qR T-PCR)法检测不同组miR-381-3p的表达水平以验证转染效率;诱导MC3T3-E1细胞成骨分化后,检测各组细胞中碱性磷酸酶(ALP)活性水平;茜素红染色法检测各组细胞的成骨矿化能力; qR T-PCR测定各组细胞中ALP、Runx2、PPARγ和ETS1 mR NA表达水平;蛋白免疫印迹法测定各组细胞中collagenⅠ、ALP、Runx2、PPARγ、ETS1、P-ERK1/2水平;并用MAPK/ERK通路抑制剂(PD98059)干预各组细胞后进行目的蛋白检测。结果 与NC mimic miR-381-3p组、mimic miR-381-3p组及NC inhibitor miR-381-3p组比较,inhibitor miR-381-3p组中细胞中ALP、Runx2、ET...     

pcDNA3-hBMP2转染对成纤维细胞 生物学性状的影响

目的 探讨人BMP2基因转染对成纤维细胞NIH3T3生物学性状的影响。方法 构建重组真核表达载体pcDNA3-hBMP2,并在脂质体介导下,将其导入NIH3T3成纤维细胞,通过G418筛选获得阳性克隆,用细胞原位杂交和免疫组织化学方法检测hBMP2基因在NIH3T3成纤维细胞内的表达情况;MTT法和FCM检测pcDNA3-hBMP2转染pcDNA3-hBMP2后成纤维细胞超微结构的改变,碱性磷酸酶的检测观察转染pcDNA3-hBMP2后成纤维细胞向成骨细胞分化情况。结果 转染pcvDNA3-hBMP2后的NIH3T3细胞内有大量hBMP2mRNA的转录及其蛋白的表达;转染pcDNA3-hBMP2对成纤维细胞增殖和细胞周期无影响;转染pcDNA3-hBMP2后的成纤维细胞超微结构可见粗面内质网丰富,囊腔扩张明显其内充满中等电子密度的蛋白分泌物;碱性磷酸酶活性显著上升。结论 pcDNA3-hBMP2转染对成纤维细胞NIH3T3增殖和细胞周期无影响。转染后的成纤维细胞不仅可形成BMP2,而且具有向成骨细胞系分化的特性。     

Choledochal cysts: Part 3 of 3: Management

Much about the etiology, pathophysiology, natural course and optimal treatment of cystic disease of the biliary tree remains under debate. Gastroenterologists, surgeons and radiologists alike still strive to optimize their roles in the management of choledochal cysts. To that end, much has been written about this disease entity, and the purpose of this 3-part review is to organize the available literature and present the various theories currently argued by the experts. In part 3, we discuss the management of choledochal cysts, thus completing our comprehensive review.     

H3K4m3和H3K9m3修饰对胰岛组织特异性基因表达的影响

目的 通过比较不同细胞类型之间胰腺十二指肠同源盒1(Pdx-1)、配对盒基因4(Pax4)、MafA(mast cell function associated antigen)和Nkx6.1等胰岛组织特异性基因其转录起始区的H3K4m3和H3K9m3修饰的差异,探讨H3K4m3和H3K9m3修饰对胰岛组织特异性基因表达的作用.方法 采用染色质免疫共沉淀一实时定量聚合酶链反应(PCR)法检测小鼠胚胎干细胞(mES,1×10~7)、小鼠成纤维细胞株NIH3T3细胞(1×10~7)和小鼠β细胞株NIT-1细胞(1×10~7)三者中的胰岛组织特异性基因、Oct4基因和MLH1基因转录起始区H3K4m3和H3K9m3修饰的状况.同时采用实时定量逆转录(RT)-PCR检测上述3种细胞各基因mRNA表达水平.分析H3K4m3和H3K9m3修饰改变与基因表达之间的关系.结果 NIT-1细胞中Pdx-1、Pax4、MafA、Nkx6.1等胰岛组织特异性基因转录起始区的H3K4m的修饰水平分别为:(4.84±0.05)%、(9.91±1.33)%、(10.64±0.87)%、(0.23±0.03)%,与mES细胞比较明显增高(P<0.05),基因表达;NIH3T3细胞中Pdx-1、Pax4、MafA、Nkx6.1等胰岛组织特异性基因转录起始区的H3K9m3的修饰水平分别为:(0.64±0.21)%、(7.04±1.29)%、(0.39±0.10)%、(2.35±0.81)%,与mES细胞比较明显增高(P<0.05),基因不表达.结论 H3K4m3与H3K9m3修饰能相互协调,共同调控胰岛组织特异性基因的表达.     

Overexpression of EIF3S3 promotes cancer cell growth

BACKGROUND: Amplification and overexpression of EIF3S3 gene has been demonstrated in breast and prostate cancer. Here, our goal was to study the effect of EIF3S3 on cell growth. METHODS: The effect of EIF3S3 on growth of NIH 3T3 murine fibroblasts as well as breast (SK-Br-3 and ZR-75-1) and prostate (PC-3 and LNCaP) cancer cell lines was examined by using transfection with inducible pTet-Off system and siRNAs. RESULTS: NIH 3T3 cells with overexpression of EIF3S3 grew significantly faster than cells transfected with empty vector and survived longer when grown in soft agar. The EIF3S3 overexpression was associated with increased fraction of cells in S-phase and with phosphorylation of retinoblastoma (Rb) protein. siRNA treatment inhibited significantly (P = 0.0022) the growth of all breast and prostate cancer cell lines studied. CONCLUSIONS: The results suggest that EIF3S3 regulates cell growth and viability, and that overexpression of the gene may provide growth advantage to the cancer cells.     

Identification of the insulin-regulated interaction of phosphodiesterase 3B with 14-3-3 beta protein

Phosphodiesterase (PDE)-3B, a major PDE isoform in adipocytes, plays a pivotal role in the antilipolytic action of insulin. Insulin-induced phosphorylation and activation of PDE3B is phosphatidylinositol 3-kinase (PI3-K) and Akt dependent, but the precise mechanism of PDE3B activation is not fully understood. We have identified 14-3-3 beta, a critical scaffolding molecule in signal transduction, as a protein that interacts with PDE3B using the yeast two-hybrid system. The interaction between PDE3B and 14-3-3 beta was then confirmed in vitro. The glutathione S-transferase (GST)-tagged 14-3-3 beta interacts with endogenous PDE3B of rat adipocytes, and this interaction is enhanced when adipocytes are treated with insulin. Coimmunoprecipitation experiments reveal that endogenous PDE3B also associates with endogenous 14-3-3 beta in rat adipocytes, and this interaction is enhanced by insulin. Two different PI3-K inhibitors, wortmannin and Ly294002, block this induction, suggesting that PI3-K is required. Synthetic 15 amino acid peptides of rat PDE3B containing phosphorylated Ser-279 or -302 inhibit this interaction, indicating that the insulin-regulated phosphorylation of these serine residues is involved. Because insulin receptor substrate-1 also associates with 14-3-3, the dimeric 14-3-3 beta could function as a scaffolding protein in the activation of PDE3B by insulin.     

SH3BP2 mutations potentiate osteoclastogenesis via PLCγ

To determine the mechanism for the increased osteoclastogenesis in the jaw of cherubism patients with SH3BP2 mutations we evaluated the effect of mutant compared to wild‐type SH3BP2 on activation of osteoclast signaling pathways. Indeed mutant forms of SH3BP2 do induce greater osteoclastogenesis. Heterozygous activating mutations in exon 9 of SH3BP2 have been found in most patients with cherubism, an unusual genetic syndrome characterized by excessive remodeling of the mandible and maxilla due to spontaneous and excessive osteoclastic bone resorption. Here we have investigated the functional consequences of SH3BP2 mutations on sRANKL‐induced osteoclastogenesis in RAW 264.7 pre‐osteoclast cells. sRANKL‐stimulated RAW 264.7 cells were transfected with wild‐type or mutant SH3BP2 plasmids. NFAT‐luciferase and tartrate resistant acid phosphatase (TRAP), a marker of osteoclastic differentiation, levels were evaluated. Western immunoblots were also performed to determine phosphorylation of key proteins involved in the PI‐PLC pathway leading to NFATc1 translocation. Our results indicate that forced expression of mutant forms of SH3BP2, found in cherubism patients, in RAW 264.7 cells induce greater NFAT activity and greater expression of TRAP than forced expression of wild‐type SH3BP2. These findings indicate that missense SH3BP2 mutations cause a gain of protein function. Moreover, over expression of SH3BP2 in RAW 264.7 cells potentiates sRANKL‐stimulated phosphorylation of PLCγ1 and PLCγ2. Our studies demonstrate that cherubism is due to gain‐of‐function mutations in SH3BP2 that stimulate RANKL‐induced activation of PLCγ. The consequent activation of calcineurin and NFAT proteins induces the excessive osteoclastic phenotype of cherubism. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1425–1430, 2010     

Effects of carboxy-terminal modifications of proteinase 3 (PR3) on the recognition by PR3-ANCA

BACKGROUND: Autoantibodies directed against neutrophil proteinase 3 (PR3-ANCA) from patients with Wegener's granulomatosis and microscopic polyangiitis recognize conformational epitopes of PR3. During maturation of neutrophils, PR3 undergoes amino-terminal and carboxy-terminal processing. In contrast to amino-terminal processing, the effects of carboxy-terminal processing on recognition of PR3 by PR3-ANCA remain unknown. Carboxy-terminally modified or tagged recombinant PR3 (rPR3) molecules may be useful for the refinement of diagnostic assays and for the study of biological processes. METHODS: This study was designed to determine whether 293 cells can be used to express specifically designed carboxy-terminal variants of rPR3, and to evaluate the effects of different carboxy-terminal modifications on the recognition by PR3-ANCA in the capture ELISA. RESULTS: The rPR3-variants secreted into the media supernatants of transfected 293 cells escaped proteolytic processing. Furthermore, in contrast to the effects of amino-terminal pro-peptide deletion on PR3-ANCA binding, carboxy-terminal modifications (deletion and additions) did not significantly affect recognition by PR3-ANCA. CONCLUSIONS: This expression system is ideally suited for the expression of custom-designed carboxy-terminal rPR3 variants, and major conformational effects of carboxy-terminal modifications seem unlikely.     

Actin and microtubule cytoskeletons of the processes of 3D-cultured MC3T3-E1 cells and osteocytes

Cell shape is the most critical determinant of cell function and is potentially influenced by the organization of a cell's cytoskeletal components. It has been reported that three-dimensionally cultured osteoblasts have a morphology that closely resembles that of osteocytes, most notably including formation of processes. We have previously shown the critical differences between cytoskeletal components in osteoblasts and osteocytes in two-dimensional culture. We have now extended that investigation to the cytoskeletal components of 3D-cultured osteoblasts and osteocytes using 3D cultures of the osteoblast cell line, MC3T3-E1, and primary osteocytes grown in collagen gel. Three-dimensional fluorescent image reconstructions for actin, fimbrin, alpha-actinin, myosin, tropomyosin, and microtubules were made using IMARIS software. Actin, fimbrin, alpha-actinin, myosin, and tropomyosin all appeared in the processes of both cell types, but fimbrin and myosin showed differences in their distribution patterns between cell types. Microtubules were limited in distribution to the proximal region of osteocyte processes but extended the entire length of MC3T3-E1 cell processes. Microtubules were essential for the integrity and formation of MC3T3-E1 cell processes, but osteocyte processes were dependent on actin. These results showed that there are significant differences between the actin and microtubule cytoskeletons in the processes of 3D-cultured MC3T3-E1 cells and in the processes of 3D-cultured primary osteocytes. These differences in the cytoskeleton of the processes of 3D-cultured osteoblasts and of osteocyte dendrites suggest that osteoblast processes may have a different functional role than the osteocyte dendritic network. An erratum to this article is available at .