Chondrocytes or adult stem cells for cartilage repair: the indisputable role of growth factors

Articular cartilage is easily injured but difficult to repair and cell therapies are proposed as tools to regenerate the defects in the tissue. Both differentiated chondrocytes and adult mesenchymal stem cells (MSCs) are regarded as cells potentially able to restore a functional cartilage. However, it is a complex process from the cell level to the tissue end product, during which growth factors play important roles from cell proliferation, extracellular matrix synthesis, maintenance of the phenotype to induction of MSCs towards chondrogenesis. Members of the TGF-β superfamily, are especially important in fulfilling these roles. Depending on the cell type chosen to restore cartilage, the effect of growth factors will vary. In this review, the roles of these factors in the maintenance of the chondrocyte phenotype are discussed and compared with those of factors involved in the repair of cartilage defects, using chondrocytes or adult mesenchymal stem cells.     

不同来源间充质干细胞在膝关节软骨修复中的临床研究进展

近年来由于器官修复干细胞治疗技术的提出,使得不能自身修复的关节软骨成为研究热点之一,间充质干细胞对膝关节软骨修复已表现出明显的治疗优势。学者们临床上初步研究了不同来源的间充质干细胞膝关节软骨修复作用,并通过结合移植、软骨组织工程等技术提高了骨髓、脂肪、滑膜、脐带血等来源干细胞修复人类软骨效果,均取得了较好的临床疗效。不同干细胞来源不同各自会有一定的优缺点。目前临床研究仍处于试验阶段,尚无确切定论何种干细胞及何种技术处理最适合于人类软骨的修复。大规模和或结合新处理技术的临床试验以及远期疗效的验证,需要进一步临床深入研究。     

Traditional techniques and experimental therapeutic approach for the restore of degenerate cartilages

Cartilage is unable to repair itself. The actual treatments for cartilage lesions primarily cover up symptoms only and this had led to develop alternative means to restore degenerated cartilage, above all by using cell therapy. The therapeutic approaches initially focused on the implantation of autologous chondrocytes, but this technique proved unsatisfactory. The discovery that several adult human tissues contain mesenchymal stem cells (MSCs) capable of differentiating into chondrocytes raised the possibility of using MSCs to repair cartilages. In the present study we investigated whether mesenchymal stem cells from adipose tissue (hADAS) are able to differentiate into cartilage cells. We isolated cells from lipoaspirates, characterized them detecting specific surface markers by FACS analysis and immunofluorescence. We differentiate hADAS towards condrogenic line in a culture media supplemented with some specific factors and in a specific condition called pellet culture. The isolation of hADAS cells is reproducible and characterized by an high reproductivity, non dependent from the donor age. The expression of surface markers suits with the literature data. The cells differentiated towards chondrogenic line in pellet culture show a different morphology from the undifferentiated cells. The potential application of MSC therapy provides new hope for the development of innovative treatments for the repair of cartilage lesions and disorders.     

不同应力环境对兔骨髓间充质干细胞修复关节软骨缺损的影响

目的探讨不同应力环境对骨髓间充质干细胞(MSCs)修复关节软骨缺损的影响. 方法将日本大耳白兔15只制成髌骨外侧脱位动物模型,平均分成3组,每组5只:即单纯载体脱位组(对照组)、移植物正常应力组及移植物脱位组.对兔MSCs进行分离、培养,以兔MSCs为种子细胞构建自体组织工程移植物修复关节软骨缺损.6周后处死动物,观察修复组织的成分和结构. 结果术后6周,移植物正常应力组修复组织浅层为软骨组织,甲苯胺蓝染色接近正常关节软骨;深层为软骨下骨,与正常关节软骨结构相似.移植物脱位组为骨组织所修复,缺损周围的正常关节软骨变薄,软骨下血管侵入正常关节软骨内,遗留在股骨髁滑车槽内的移植物在滑车槽正常关节软骨表面形成新生类透明软骨组织.单纯载体脱位组为纤维组织修复. 结论 MSCs修复关节软骨缺损,只有在正常应力状态下修复效果最佳;提示维持负重关节正常的应力刺激,对组织工程软骨修复组织的形成和维持必不可少.     

Exogenous collagen-enhanced recruitment of mesenchymal stem cells during rabbit articular cartilage repair

Background?Despite the well-known effect of type-I collagen in promoting cartilage repair, the mechanism still remains unknown. In this study we investigated this mechanism using a rabbit model of cartilage defects.

Animals and methods?5-mm-diameter full-thickness defects were created on both patellar grooves of 53 Japanese white rabbits (approximately 13 weeks old). The left defect was filled with collagen gel and the right defect was left empty. The rabbits were killed and examined morphometrically until the twenty-fourth postoperative week, by (1) evaluation of matrix production, (2) enumeration of the total number of cells engaged in cartilage repair, (3) enumeration of the proliferating cells, (4) localization of mesenchymal stem cells, and (v) localization of apoptotic cells.

Results?We found that type-I collagen enhances cell recruitment, and thereby increases the number of proliferating cells. A considerable proportion of the proliferating cells were identified as bone marrow-derived mesenchymal stem cells. However, type-I collagen does not prevent the chondrocyte precursors from undergoing apoptotic disengagement from the chondrogenic lineage.

Interpretation?Type-I collagen promotes cartilage repair by enhancing recruitment of bone marrowderived mesenchymal stem cells. Additional use of agent(s) that sustain mesenchymal stem cells along the chondrogenic path of differentiation may constitute an appropriate environment for cartilage repair.     

Exogenous collagen-enhanced recruitment of mesenchymal stem cells during rabbit articular cartilage repair

Background Despite the well-known effect of type-I collagen in promoting cartilage repair, the mechanism still remains unknown. In this study we investigated this mechanism using a rabbit model of cartilage defects.

Animals and methods 5-mm-diameter full-thickness defects were created on both patellar grooves of 53 Japanese white rabbits (approximately 13 weeks old). The left defect was filled with collagen gel and the right defect was left empty. The rabbits were killed and examined morphometrically until the twenty-fourth postoperative week, by (1) evaluation of matrix production, (2) enumeration of the total number of cells engaged in cartilage repair, (3) enumeration of the proliferating cells, (4) localization of mesenchymal stem cells, and (v) localization of apoptotic cells.

Results We found that type-I collagen enhances cell recruitment, and thereby increases the number of proliferating cells. A considerable proportion of the proliferating cells were identified as bone marrow-derived mesenchymal stem cells. However, type-I collagen does not prevent the chondrocyte precursors from undergoing apoptotic disengagement from the chondrogenic lineage.

Interpretation Type-I collagen promotes cartilage repair by enhancing recruitment of bone marrowderived mesenchymal stem cells. Additional use of agent(s) that sustain mesenchymal stem cells along the chondrogenic path of differentiation may constitute an appropriate environment for cartilage repair.     

Mesenchymal stem cells in kidney inflammation and repair

Mesenchymal stem cells are a heterogeneous population of fibroblast-like stromal cells that have been isolated from the bone marrow and a number of organs and tissues including the kidney. They have multipotent and self-renewing properties and can differentiate into cells of the mesodermal lineage. Following their administration in vivo, mesenchymal stem cells migrate to damaged kidney tissue where they produce an array of anti-inflammatory cytokines and chemokines that can alter the course of injury. Mesenchymal stem cells are thought to elicit repair through paracrine and/or endocrine mechanisms that modulate the immune response resulting in tissue repair and cellular replacement. This review will discuss the features of mesenchymal stem cells and the factors they release that protect against kidney injury; the mechanisms of homing and engraftment to sites of inflammation; and further elucidate the immunomodulatory effect of mesenchymal stem cells and their ability to alter macrophage phenotype in a setting of kidney damage and repair.     

膝关节牵伸术修复膝关节软骨的研究进展

膝关节牵伸术是近年来治疗膝骨关节炎的新技术,它能减轻膝关节疼痛和改善膝关节功能,这与其修复软骨的作用密不可分。膝关节牵伸术修复软骨的作用机制和影响因素作为当前研究的热点,本文通过回顾文献发现,膝关节牵伸术能减轻膝关节负荷为软骨修复提供适宜的力学环境,引起的膝关节流体静水压波动不仅能帮助软骨吸收营养,还能促进软骨形成基因和抑制软骨基质降解酶基因表达。此外,膝关节牵伸术为滑液间充质干细胞募集到软骨损伤处创造了条件,并提升了滑液间充质干细胞增殖、分化为成软骨谱系的能力。膝关节牵伸术还能通过减少膝关节内部炎性因子含量和抑制炎性基因表达,减轻膝关节炎症反应和软骨损伤。目前已知的影响膝关节牵伸术修复软骨的因素包括适当增加膝关节负重活动、牵伸高度和牵伸时间有助于软骨修复,男性患者、膝关节炎严重程度更高的患者膝关节牵伸术后软骨修复效果更好。而膝关节牵伸术后第1年软骨修复疗效越好,预示着膝关节牵伸术保留膝关节的远期生存率越高。但目前对上述热点的研究只停留在初期阶段,仍需进行更深入的探索,才能对膝关节牵伸术的临床应用起到更好的指导。     

A review of the effects of insulin-like growth factor and platelet derived growth factor on in vivo cartilage healing and repair

Growth factors may enhance current cartilage repair techniques via multiple mechanisms including recruitment of chondrogenic cells (chemotaxis), stimulation of chondrogenic cell proliferation (mitogenesis) and enhancement of cartilage matrix synthesis. Two growth factors that have been studied in cartilage repair are insulin-like growth factor (IGF) and platelet derived growth factor (PDGF). IGF plays a key role in cartilage homeostasis, balancing proteoglycan synthesis and breakdown. Incorporating IGF into a fibrin clot placed in an equine cartilage defect improved the quality and quantity of repair tissue and reduced synovial inflammation. PDGF is a potent mitogenic and chemotactic factor for all cells of mesenchymal origin, including chondrocytes and mesenchymal stem cells. Resting zone chondrocytes cultured with PDGF demonstrated increased cell proliferation and proteoglycan production, while maturation of these cells along the endochondral pathway was inhibited. Pretreating chondrocytes with PDGF promotes heterotopic cartilage formation in the absence of any mechanical stimulus. PDGF has also been shown to be a potent stimulator of meniscal cell proliferation and migration. These studies and others suggest a potential role for these potent biological regulators of chondrocytes in cartilage repair. More work needs to be performed to define their appropriate dosing and the optimum delivery method. Combining tissue growth factors with a biological matrix can provide a physical scaffold for cell adhesion and growth as well as a means to control the release of these potent molecules. This could result in biological devices that enhance the predictability and quality of current cartilage repair techniques.     

骨髓基质干细胞及其应用研究进展

骨髓基质干细胞(BMSCs)作为一种干细胞，由于具有很强的自我更新能力和多分化潜能，近年来引起了广泛的注意，体内外试验中已发现BMSCs可以分化为骨组织和软骨组织、神经组织等组织的细胞，并且具有修复以上各组织缺损的能力；同时发现BMSCs是一种理想的基因载体，从而达到基因治疗的目的。本文旨在对BMSCs的分离、培养、生物学特性、基因治疗及其组织修复中的应用研究进展作一综述。