The chondrocyte channelome: A narrative review

Chondrocytes are the main cells in the extracellular matrix (ECM) of articular cartilage and possess a highly differentiated phenotype that is the hallmark of the unique physiological functions of this specialised load-bearing connective tissue. The plasma membrane of articular chondrocytes contains a rich and diverse complement of membrane proteins, known as the membranome, which defines the cell surface phenotype of the cells. The membranome is a key target of pharmacological agents and is important for chondrocyte function. It includes channels, transporters, enzymes, receptors, and anchors for intracellular, cytoskeletal and ECM proteins and other macromolecular complexes. The chondrocyte channelome is a sub-compartment of the membranome and includes a complete set of ion channels and porins expressed in these cells. Many of these are multi-functional proteins with “moonlighting” roles, serving as channels, receptors and signalling components of larger molecular assemblies. The aim of this review is to summarise our current knowledge of the fundamental aspects of the chondrocyte channelome, discuss its relevance to cartilage biology and highlight its possible role in the pathogenesis of osteoarthritis (OA). Excessive and inappropriate mechanical loads, an inflammatory micro-environment, alternative splicing of channel components or accumulation of basic calcium phosphate crystals can result in an altered chondrocyte channelome impairing its function. Alterations in Ca²⁺ signalling may lead to defective synthesis of ECM macromolecules and aggravated catabolic responses in chondrocytes, which is an important and relatively unexplored aspect of the complex and poorly understood mechanism of OA development.     

Membrane-seeded autologous chondrocytes: cell viability and characterization at surgery

The implantation of chondrocytes, seeded on matrices such as hyaluronic acid or collagen membranes, is a method that is being widely used for the treatment of chondral defects. The aim of the present study was to evaluate the distribution, viability and phenotype expression of the cells seeded on a collagen membrane just at the time of the implantation. Twelve patients who were suffering from articular cartilage lesions were treated by the MACI^® procedure. The residual part of each membrane was tested by colorimetric assay (MTT) and histochemical and ultrastructural analyses were carried out. In all of the samples a large number of viable cells, quite homogenously distributed, was detected. The cells expressed the markers of the differentiated hyaline chondrocytes. These data reassure in that the MACI procedure provides a suitable engineered tissue for cartilage repair, in line with the clinical evidences emerging in the literature.     

骨髓基质干细胞修复兔关节软骨缺损的实验研究

目的研究以多聚乙醇酸(PGA)为支架的骨髓基质干细胞(BMSCs)复合物修复兔膝关节软骨缺损的情况。方法体外培养扩增的自体BMSCs种植于PGA支架并培养72h,然后将支架-细胞复合物植入兔关节软骨缺损模型。术后12周处死动物,标本行大体观察、组织学检查及Ⅱ型胶原免疫组化染色。结果BMSCs-PGA复合物植入后形成丰富的透明软骨样修复组织,新生软骨无明显退变。对照组主要为纤维组织及软骨下骨修复。结论BMSCs-PGA复合物可修复关节软骨缺损。     

胚胎颅骨骨膜移植修复髋关节软骨大面积缺损

１９９０年５月～１９９４年４月，对４２例（４７个髋）关节软骨全厚缺损患者采用冷冻保存胚胎颅骨骨膜移植进行修复，其中１４例股骨头骨质Ⅳ期坏死者，同时施行带旋髂深血管蒂髂骨植骨。对３４例（３８个髋）进行了２年～６年（平均４０个月）随访。结果表明，按照吴之康髋关节人工置换术后疗效评定标准，优良２５例，很好５例，好３例，尚可１例。认为，与自体移植物修复关节软骨大面积缺损相比，这种方法无附加损伤，具有移植材料、形态与股骨头相似等特点，是治疗髋关节软骨大面积缺损的一种有效方法。     

游离骨膜移植修复关节软骨缺损的实验研究

在家兔的股骨内髁上作一关节软骨全层缺损,且从同侧胫骨近端取下一片骨膜骨块,将骨膜生发层向外包绕骨块,嵌入缺损处,观察其作用。实验表明,骨膜在一定条件下可以化生成软骨;滑液环境与关节运动在软骨化生过程中起重要作用;透明软骨化生和再生率与运动量及开始时间相关;自体骨可作为一种将游离骨膜固定在软骨缺损内的填充材料。     

Synovial chondromatosis of four compartments of the knee: medial and lateral tibiofemoral spaces,patellofemoral joint and proximal tibiofibular joint

A case of synovial chondromatosis of the proximal tibiofibular joint in addition to lateral and medial tibiofemoral spaces and patellofemoral joint has been presented.     

软骨下骨钻孔术对兔软骨缺损修复的远期效果观察

目的　观察软骨缺损的修复过程 ,比较不同数目钻孔术对软骨缺损修复的远期效果。方法　用中国白兔 4 0只 ,在股骨髁关节面造成 6mm× 8mm全层软骨缺损 ,分别施行 10孔及 5孔钻孔术 ,孔径1mm ,于术后 12周及 13个月取材 ,做组织学及电镜观察 ,并进行评估。结果　 (1) 12周时 10孔、5孔和对照组的修复组织中类透明软骨分别占 70 %、5 0 %、0 % ;13个月时 10孔、5孔和对照组的修复组织中类透明软骨分别占 90 %、10 0 %、0 %。 (2 )修复组织厚度 :12周时 10孔及 5孔组均明显高出毗邻软骨 ,且 10孔明显高于 5孔 ;13个月时 10孔与 5孔无显著性差异 ,且已接近毗邻软骨厚度。 (3)修复组织覆盖缺损的面积 :12周时 10孔 >5孔 >对照组 ;13个月时 10孔与 5孔无显著性差异 ,但二者均明显大于对照组。结论　软骨下骨钻孔对关节软骨缺损修复的远期效果良好 ,能长期适应关节的生理运动和功能负重 ,10孔与 5孔的远期修复效果无显著性差异。