人胎关节软骨细胞体外培养的生物学特性

目的 研究软骨组织工程中传代软骨细胞与原代的差异。方法 用５个月人胎关节软骨分离培养细胞,观察细胞存活率、贴壁率、生长曲线和组织形态学的改变。结果 ⑴软骨块在４℃下,３ｄ内细胞存活率可达９３．４％～９７．６％。⑵原代细胞为圆形或三角形;第４代有一半转变成梭形,到第６代全部变为长梭形。⑶传代细胞贴壁时间（２～３ｈ）短于原代（４～７ｈ）。玻璃瓶内贴壁率传代细胞为７８．７％～８５．５％,原代８．８％。⑷     

Biological freezing of human articular chondrocytes

AIM: To preserve viable, metabolically active chondrocytes cultured in alginate beads at -196 degrees C for further use in in vitro and in vivo studies. METHODS: Human articular chondrocytes were isolated from femoral condyles within 24 h post mortem. To optimize the biological freezing procedure, the chondrocytes were control-rate frozen in different concentrations of dimethyl sulfoxide (DMSO) in Dulbecco's MEM supplemented with 10% FCS before being thawed and the cell viability was determined by Trypan Blue exclusion test. To investigate the effect of control-rate freezing on chondrocyte metabolism, control-rate frozen chondrocytes in 5% DMSO were thawed and cultured in gelled agarose for 2 weeks. Non-frozen chondrocytes cultured in agarose served as controls. Furthermore, human articular chondrocytes were cultured in 2% alginate beads for 2 weeks after which the beads were incubated with 5% DMSO for 0 h, 2.5 h, 5 h and 10 h and frozen at -196 degrees C. Non-frozen alginate beads containing chondrocytes and incubated with 5% DMSO served as a control. After 2 weeks in culture, chondrocytes in agarose or in alginate were sulfated with 10 microCi(35)SO(4)/ml for 48 h. The total production of aggrecans, and the aggrecan subtypes, were subsequently determined. RESULTS: Five percent DMSO in the culture medium was the optimal condition to control-rate freeze and recover viable and functional isolated chondrocytes. Total aggrecan synthesis of control-rate frozen chondrocytes cultured in gelled agarose was not significantly reduced when compared with control cells. The proportion of aggrecan in the aggregate form of control-rate frozen chondrocytes kept in agarose remained unaltered. Chondrocytes, control-rate frozen in the alginate matrix, showed a 0-30% decrease in total aggrecan synthesis rates in culture when compared with the non-frozen chondrocytes. The optimal pre-incubation time of the alginate beads with 5% DMSO was 5 h, without any change in aggrecan synthesis rates when compared with the control situation. Shorter pre-incubation times resulted in an insufficient diffusion of DMSO into the beads and in cell death. There was no difference in the synthesis of the different aggrecan subtypes between frozen and non-frozen chondrocytes in alginate. CONCLUSION: Human articular chondrocytes can be stored at -196 degrees C for 24 h without important decreases in their aggrecan synthesis rates when control-rate frozen as a cell suspension in 5% DMSO. Proportions of the aggrecan subtypes (monomers, aggregates) synthesized by chondrocytes cultured in agarose remained unchanged. The control-rate freezing procedure in the alginate beads pre-incubated with 5% DMSO for 5 h produced no decrease in total aggrecan synthesis rates and no change in the synthesized aggrecan subtypes. Further experiments have to confirm the suitability of this freezing method for long-term storage of chondrocytes allowing us to set up a 'chondrocyte' bank for further use in in vitro and in vivo manipulations.     

兔胚胎关节软骨细胞体外培养的研究

目的 探讨兔胚胎软骨细胞体外培养的生物学特性。方法 对孕4周兔胚胎关节软骨用酶消化法分离培养细胞。观察细胞存活率、贴壁率、生长曲线和组织形态学改变。结果 兔胚胎软骨细胞可从胚胎软骨组织中消化分离出来，经鉴定具有软骨细胞的特性。原代兔胚软骨细胞存活率达97％以上，细胞贴壁率达80％以上，从原代到第4代都有高增殖力，到第8代时增殖力降低。到第12代时几乎丧失细胞增殖。结论 体外培养的胚胎软骨细胞前4代适合于作修复关节软骨缺损的组织工程细胞。     

Mitochondrial proteomic characterization of human normal articular chondrocytes

OBJECTIVE: Mitochondrial dysfunctions have been associated with apoptosis, aging and osteoarthritis (OA). Chondrocyte mitochondrial proteins are attractive targets for the study of the metabolism of cartilage degradation. The copurification of "contaminating" proteins has been the major problem in all phases of mitochondrial proteome research. Therefore, we set up a procedure for the proteomic analysis of human chondrocyte mitochondrial proteins. METHOD: Four types of protein extracts were obtained from primary cultured chondrocytes isolated from healthy donors: (1) initial total chondrocyte extract (CE), (2) cytosol-enriched supernatant fraction (CY), (3) crude mitochondria fraction (CM), and (4) pure mitochondria fraction (PM). Mitochondria were purified by density gradient ultracentrifugation. Mitochondrial proteins were separated by means of two-dimensional gel electrophoresis (2-DE) and silver stained. Protein spots were then identified by mass spectrometry using MALDI-TOF/TOF technology. RESULTS: The best 2-DE reference map of mitochondrial proteome was constructed employing PM fraction. Thirty-nine percent of the identified proteins were functionally distributed in the mitochondria, 14% in the endoplasmic reticulum and 36% in the cytoplasm. Examining their biological function, 22% are involved in protein targeting, 12% in signaling, 12% in glycolysis, 10% in RNA, DNA or protein synthesis, 10% in oxidative phosphorylation and 4% in redox. The analysis of mitochondrial Mn-superoxide dismutase (SODM) revealed an age-dependent decrease of this protein. CONCLUSION: PM fraction allowed the obtention of a high quality proteomic map for the study of mitochondrial proteins in human articular chondrocytes. This proteomic approach may be also efficient to analyze both quantitative and qualitative modulations of the mitochondrial proteome in human chondrocytes during aging and pathological conditions such as OA.     

Gene expression during redifferentiation of human articular chondrocytes

OBJECTIVE: The aim of the present study was to investigate gene expression during the in vitro redifferentiation process of human articular chondrocytes isolated from clinical samples from patient undergoing an autologous chondrocyte transplantation therapy (ACT). METHOD: Monolayer (ML) expanded human articular chondrocytes from four donors were cultured in a 3D pellet model and the redifferentiation was investigated by biochemistry, histology, immunohistochemistry and microarray analysis. RESULTS: The culture expanded chondrocytes redifferentiated in the pellet model as seen by an increase in collagen type II immunoreactivity between day 7 and 14. The gene expression from ML to pellet at day 7 included an increase in cartilage matrix proteins like collagen type XI, tenascin C, dermatopontin, COMP and fibronectin. The late phase consisted of a strong downregulation of extracellular signal-regulated protein kinase (ERK-1) and an upregulation of p38 kinase and SOX-9, suggesting that the late phase mimicked parts of the signaling processes involved in the early chondrogenesis in limb bud cells. Other genes, which indicated a transition from proliferation to tissue formation, were the downregulated cell cycle genes GSPT1 and the upregulated growth-arrest-specific protein (gas). The maturation of the pellets included no signs of hypertrophy or apoptosis as seen by downregulation of collagen type X, Matrix Gla protein and increased expression of caspase 3. CONCLUSION: Our data show that human articular chondrocytes taken from surplus cells of patient undergoing ACT treatment and expanded in ML, redifferentiate and form cartilage like matrix in vitro and that this dynamic process involves genes known to be expressed in early chondrogenesis.     

Distribution of chondrocytes containing alpha-smooth muscle actin in human articular cartilage.

Relatively little is known about the contractile behavior of the human articular chondrocyte. Other connective tissue cells are known to express a contractile actin isoform, alpha-smooth muscle actin, in response to injury, at selected stages of wound healing, and in certain pathological conditions. This and recent work demonstrating contractile behavior in adult canine articular chondrocytes in vitro prompted the present study of the distribution of alpha-smooth muscle actin-containing chondrocytes in human articular cartilage. Approximately 75% of the chondrocytes in the superficial region of cartilage expressed alpha-smooth muscle actin as demonstrated by immunohistochemistry. In contrast, only approximately 10% of the cells in the deep region stained for this contractile actin isoform. There was no correlation of the percentage of alpha-smooth muscle actin-positive cells in either region with Mankin grade or with age. This is the first report of a contractile potential for human articular chondrocytes. The roles of alpha-smooth muscle actin in these cells warrant further investigation. The question of whether it is necessary to refer to these cells as myochondrocytes is considered.     

Optimization of cryopreservative procedures for human articular cartilage chondrocytes

Procedures are being developed which use isolated articular cartilage (AC) chondrocytes to restore damaged articular surfaces. The availability of isolated human chondrocytes for transplantation may be increased by low-temperature storage (banking). At present, no single method of freezing chondrocytes has been proven to be optimal. In this project, two different freezing protocols, I and II, were compared. Protocol I used freezing rates of –1° C/min down to a temperature of –40°C. Protocol II used a freezing rate of –1° C/min down to –10° C and faster rates thereafter. Cells were stored for 2 weeks at –196°C. Survival and function of the cells after thawing were evaluated by histological examination and determination of ³⁵S-and ³H-thymidine incorporation after 1 and 2 weeks of high-density monolayer culture. Cells frozen with protocol 1 showed better function and survival (99.75%) than cells frozen with protocol II (85%). Both groups showed slowing of metabolism and replication after freezing when compared with controls. We conclude that controlled freezing of adult human chondrocytes at rates of –1° C/min improves survival. Banking of human AC chondrocytes may be feasible using protocol I, although some questions regarding the long-term behaviour of human AC chondrocytes after cryopreservation remain to be answered.     

Chemotaxis of human articular chondrocytes and mesenchymal stem cells

Migration of chondrocytes and mesenchymal stem cells (MSCs) may be important in cartilage development, tissue response to injury, and in tissue engineering. This study analyzed growth factors and cytokines for their ability to induce migration of human articular chondrocytes and bone marrow‐derived mesenchymal stem cells in Boyden chamber assays.In human articular chondrocytes serum induced dose‐ and time‐dependent increases in cell migration. Among a series of growth factors and cytokines tested only PDGF induced a significant increase in cell migration. The PDGF isoforms AB and BB were more potent than AA. There was an aging‐related decline in the ability of chondrocytes to migrate in response to serum and PDGF. Human bone marrow MSC showed significant chemotaxis responses to several factors, including FBS, PDGF, VEGF, IGF‐1, IL‐8, BMP‐4, and BMP‐7. In summary, these results demonstrate that directed cell migration is inducible in human articular chondrocytes and MSC. PDGF is the most potent factor analyzed, and may be useful to promote tissue integration during cartilage repair or tissue engineering. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1407–1412, 2008     

关节软骨细胞的凋亡

细胞凋亡(Apoptosis)又称程序性细胞死亡(Programmed Cell Death,PCD),为Kerr于1972年首次描述,是一种不同于坏死的细胞死亡方式.通常认为导致细胞凋亡的程序(即自杀程序)事先就装配在细胞中,如该程序在机体的内、外因素作用下被启动,细胞凋亡即开始发生.     

Repair of human articular cartilage after implantation of autologous chondrocytes

Tissue engineering is an increasingly popular method of addressing pathological disorders of cartilage. Recent studies have demonstrated its clinical efficacy, but there is little information on the structural organisation and biochemical composition of the repair tissue and its relation to the adjacent normal tissue. We therefore analysed by polarised light microscopy and immunohistochemistry biopsies of repair tissue which had been taken 12 months after implantation of autologous chondrocytes in two patients with defects of articular cartilage. Our findings showed zonal heterogeneity throughout the repair tissue. The deeper zone resembled hyaline-like articular cartilage whereas the upper zone was more fibrocartilaginous. The results indicate that within 12 months autologous chondrocyte implantation successfully produces replacement cartilage tissue, a major part of which resembles normal hyaline cartilage.     

生长因子对成人关节软骨细胞的促增殖作用

目的观察不同生长因子对成人关节软骨细胞（adult human articular chondrocytes，AHAC）增殖的影响，探索AHAC体外大量扩增的方法。方法以酶消化法从成人关节软骨分离细胞，条件培养基培养；传2代细胞分别用不同浓度成纤维细胞生长因子2（fibroblast growth factor-2，FGF-2）、转化生长因子β1（transforming growth factor β1，TGF—β1）、血小板衍生因子bb（platelet derived growth factor-bb，PDGF-hb）、肝细胞生长因子（hepatocyte growth factor，HGF）或其不同组合作用。用MTT法比较细胞增殖情况，用组化和免疫组化检测观察细胞表型变化。结果FGF-2、TGF—β1、PDGF—bb、HGF均有促AHAC增殖的作用，其最大效应剂量分别是50ng/ml、1ng／ml、1ng／ml、20ng／ml。5ng／ml FGF-2＋1ng/ml TGF-β1有最强的促增殖作用，继续加用PDGF—bb和（或）HGF无进一步促进作用；用这一因子组合培养AHAC，可以传10代以上，细胞扩增2000倍以上，且传9代细胞仍弱表达Ⅱ型胶原和aggrecan。结论FGF-2、TGF-β1、PDGF—bb、HGF均对AHAC有一定的促增殖作用；5ng／ml FGF-2＋1ng/ml TGF-β1有最大的促增殖效应，细胞短期内大量扩增，且在大量扩增的同时维持了一定的软骨细胞表型，因此是合适的AHAC体外大量扩增促进剂。     

A low temperature method of isolating normal human articular chondrocytes

OBJECTIVE: Numerous methods for isolation of human chondrocytes are reported in the literature, most based on isolation from animal cartilage. Normal human articular cartilage (NHAC) poses particular problems for isolating chondrocytes when compared to animal or other types of human cartilage: a hardy matrix, combined with few and friable chondrocytes makes isolation difficult. Our objective was to develop an efficient method of isolating chondrocytes from NHAC without jeopardising the viability of these cells. DESIGN: In this study we demonstrate that lowering the enzymatic digestion temperature to 27 degrees C increases cell yield and chondrocyte viability. We then optimised this low temperature isolation of chondrocytes from NHAC by comparing the relative efficacies of trypsin and protease and hyaluronidase in combination with different types of collagenase (I, II and XI) at releasing chondrocytes from their surrounding cartilaginous matrix. Enzymes were tested at different concentrations and for differing times. Outcome measures included determining the amount of cartilage digested, the number of viable chondrocytes isolated per gram of cartilage and cell adherence rates. CONCLUSIONS: From these set of experiments, the method that maximised cell yield without jeopardising cell viability proved to be a two stage process: pre-digestion step using trypsin for 15 min; followed by overnight digestion with a combination of two types of collagenase (types I and II) and at a lower temperature of 27 degrees C. This has resulted in an efficient and robust method of releasing chondrocytes from cartilage, without jeopardising the viability of these cells.     

关节软骨细胞库

本文介绍了关节软骨细胞的分离、冷冻保存和复苏技术，并在阐明胶原酶的细胞毒性作用的基础上，提出了分阶段消化法，以减少分离细胞的损伤，由于低温保护剂ＤＭＳＯ也具有细胞毒性，因而应尽量缩短ＤＭＳＯ与软骨细胞在４℃以上的接触时间。降温和复温速度是影响细胞存活的关键因素。降温速度从４℃～－８０℃以Ｉ℃／ｍｉｎ为佳，之后迅速投入－１９６℃的液氮中长期保存，细胞复苏应采用３７℃水浴快速复温法，虽然检测冻存细胞的存活率可采用苔盼蓝拒染试验，但最可靠的方法是细胞培养，利用关节软骨细胞库进行细胞培养、电镜观察和激光流式细胞计量分析，结果证明冻存软骨细胞复苏后仍具有正常的结构和形态并保持新陈代谢和自我复制功能。     

The role of the cytoskeleton in the viscoelastic properties of human articular chondrocytes.

Biomechanical factors are believed to play an important role in regulating the metabolic activity of chondrocytes in articular cartilage. Previous studies suggest that cytoskeletal proteins such as actin, vimentin, and tubulin influence cellular mechanical properties, and may therefore influence the mechanical interactions between the chondrocyte and the surrounding tissue matrix. In this study, we investigated the role of specific cytoskeletal components on the mechanical properties of individual chondrocytes isolated from normal or osteoarthritic hip articular cartilage. Chondrocytes were exposed to a range of concentrations of chemical agents that disrupt the primary cytoskeletal elements (cytochalasin D for F-actin microfilaments, acrylamide for vimentin intermediate filaments, and colchicine for microtubules). Chondrocyte mechanical properties were determined using the micropipette aspiration technique coupled with a viscoelastic solid model of the cell. Chondrocyte stiffness (elastic modulus) was significantly increased with osteoarthritis. With increasing cytochalasin D treatment, chondrocyte stiffness decreased by up to 90% and apparent viscosity decreased by up to 80%. The effect of cytochalasin D was greater on normal chondrocytes than those isolated from osteoarthritic cartilage. Treatment with acrylamide also decreased the moduli and viscosity, but only at the highest concentration tested. No consistent changes in cell mechanical properties were observed with colchicine treatment. These findings suggest that microfilaments and possibly intermediate filaments provide the viscoelastic properties of the chondrocyte, and changes in the structure and properties of these cytoskeletal elements may reflect changes in the chondrocyte with osteoarthritis.     

Expression of NG2/human melanoma proteoglycan in human adult articular chondrocytes

OBJECTIVE: NG2 is a transmembrane chondroitin sulfate (CS) rich proteoglycan originally identified in rats. It has recently been shown to be identical to human melanoma proteoglycan (HMPG). In rats NG2 has a limited distribution in adult tissues, being expressed predominantly by neuronal and glial cells whereas during development it is also expressed in developing mesenchyme including cartilage. NG2/HMPG has putative roles in interactions between glial and melanoma cells with extracellular matrix (ECM) molecules. This study was undertaken to assess whether NG2/HMPG was expressed by normal and osteoarthritic human articular chondrocytes. DESIGN: Cryostat sections of human fetal knee joints and normal and osteoarthritic articular cartilage were immunostained with antibodies against rat NG2 (N143.8) and HMPG (M28B5, 9.2.27). Immunoprecipitation and Western blotting was carried out on protein extracts of chondrocytes from normal and osteoarthritic cartilage. Immunofluorescence of NG2 and potential ligands was carried out in vitro on cells from normal and osteoarthritic cartilage. RESULTS: Fetal and both normal and osteoarthritic adult cartilage showed strong immunoreactivity for NG2/HMPG. Western blotting showed a smeared component of molecular weight greater than 400 kDa and a faint band at 250 kDa which became predominant upon digestion with chondroitinase ABC. Immunofluorescence of chondrocytes in vitro showed NG2 to be distributed in a punctate pattern without co-localization of actin or several ECM proteins including fibronectin and type VI collagen. CONCLUSION: NG2/HMPG is expressed by human fetal and adult chondrocytes and in adult articular chondrocytes the core protein is chondroitin sulfated. The function of this molecular in human articular cartilage remains to be defined.