Li Siwei, Sengers Bram G, Oreffo Richard O C, Tare Rahul S
Centre for Human Development, Stem Cells and Regeneration, Faculty of Medicine, University of Southampton, Southampton, UK.
Faculty of Engineering and the Environment, Bioengineering Science, University of Southampton, Southampton, UK.
J Biomater Appl. 2015 Jan;29(6):824-36. doi: 10.1177/0885328214548604. Epub 2014 Aug 20.
Regenerative medicine strategies have increasingly focused on skeletal stem cells (SSCs), in response to concerns such as donor site morbidity, dedifferentiation and limited lifespan associated with the use of articular chondrocytes for cartilage repair. The suitability of SSCs for cartilage regeneration, however, remains to be fully determined. This study has examined the chondrogenic potential of human STRO-1-immunoselected SSCs (STRO-1(+) SSCs), in comparison to human articular chondrocytes (HACs), by utilising two bioengineering strategies, namely "scaffold-free" three-dimensional (3-D) pellet culture and culture using commercially available, highly porous, 3-D scaffolds with interconnected pore networks. STRO-1(+) SSCs were isolated by magnetic-activated cell sorting from bone marrow samples of haematologically normal osteoarthritic individuals following routine hip replacement procedures. Chondrocytes were isolated by sequential enzymatic digestion of deep zone articular cartilage pieces dissected from femoral heads of the same individuals. After expansion in monolayer cultures, the harvested cell populations were centrifuged to form high-density 3-D pellets and also seeded in the 3-D scaffold membranes, followed by culture in serum-free chondrogenic media under static conditions for 21 and 28 days, respectively. Chondrogenic differentiation was determined by gene expression, histological and immunohistochemical analyses. Robust cartilage formation and expression of hyaline cartilage-specific markers were observed in both day-21 pellets and day-28 explants generated using HACs. In comparison, STRO-1(+) SSCs demonstrated significantly lower chondrogenic differentiation potential and a tendency for hypertrophic differentiation in day-21 pellets. Culture of STRO-1(+) SSCs in the 3-D scaffolds improved the expression of hyaline cartilage-specific markers in day-28 explants, however, was unable to prevent hypertrophic differentiation of the SSC population. The advantages of application of SSCs in tissue engineering are widely recognised; the results of this study, however, highlight the need for further development of cell culture protocols that may otherwise limit the application of this stem cell population in cartilage bioengineering strategies.
由于使用关节软骨细胞进行软骨修复存在供体部位发病率、去分化和寿命有限等问题,再生医学策略越来越关注骨骼干细胞(SSCs)。然而,SSCs在软骨再生中的适用性仍有待充分确定。本研究通过两种生物工程策略,即“无支架”三维(3-D)微团培养和使用具有相互连接孔网络的市售高度多孔3-D支架进行培养,比较了人类STRO-1免疫筛选的SSCs(STRO-1(+) SSCs)与人类关节软骨细胞(HACs)的软骨生成潜力。STRO-1(+) SSCs是通过磁激活细胞分选从血液学正常的骨关节炎个体的骨髓样本中分离出来的,这些个体接受了常规髋关节置换手术。软骨细胞是通过对从同一患者股骨头切下的深层关节软骨片进行顺序酶消化分离得到的。在单层培养中扩增后,收获的细胞群体被离心形成高密度3-D微团,并接种到3-D支架膜上,然后分别在无血清软骨生成培养基中静态培养21天和28天。通过基因表达、组织学和免疫组织化学分析来确定软骨分化情况。在使用HACs生成的第21天微团和第28天外植体中均观察到了强大的软骨形成和透明软骨特异性标志物的表达。相比之下,STRO-1(+) SSCs在第21天微团中表现出明显较低的软骨分化潜力和肥大分化趋势。在3-D支架中培养STRO-1(+) SSCs可改善第28天外植体中透明软骨特异性标志物的表达,然而,无法阻止SSC群体的肥大分化。SSCs在组织工程中的应用优势已得到广泛认可;然而,本研究结果强调需要进一步开发细胞培养方案,否则可能会限制这种干细胞群体在软骨生物工程策略中的应用。