生物医学工程系学术报告11.26(报告人:Zheng YANG)
发布时间: 2009-11-24 03:35:00
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北京大学工学院 生物医学工程系学术报告 |
报告一：Chondrogenic Differentiation of Human Embryonic Stem Cells
报告二：Functionalisation of scaffold for cartilage tissue engineering
报告人 Zheng YANG
Department of Orthopaedic Surgery
NUS Tissue Engineering Program,National University of Singapore
主持人：葛子钢 特聘研究员
时 间：11月26日（周四）上午9:00
地 点：廖凯原楼2-102会议室
报告内容摘要：
Part one: Embryonic stem cells (ESCs) represent an important potential cell source for regenerative therapy and tissue engineering due to their indefinite self-renewal ability and the capability to differentiate into various cell type. However, due to the spontaneity of ESCs to differentiate simultaneously into different cellular lineages, one of the challenges in utilizing ESCs in regenerative therapy is to control their differentiation process. Studies on adult and embryonic stem cells have utilised TGFβ superfamily members, such as TGFβ1, TGFβ3, BMP2, and BMP4, to regulate chondrogenic differentiation. In this study, we examined the effect of TGFβ1 in chondrogenic differentiation as well as pluripotent status of human ESCs. The effect of TGF1 was compared to cells differentiated in serum-free chondrogenic basal medium without growth factor supplement. Analysis by real-time PCR, type II collagen ELISA, sulfated glycoaminoglycan quantification and fluorescence immunostaining demonstrated substantial chondrogenic differentiation of ESCs in the absence of the growth factor. Addition of TGF1 however significantly inhibited chondrogenic gene expression and collagen deposition. Our study using a TGFβ/activin/nodal signaling inhibitor suggested that TGF inhibited early chondrogenic induction but was required at the later stage of differentiation. Analysis of the pluripotency markers demonstrated sustained Oct4 and Nanog expression in the presence of TGF1 with Oct4-positive cells detected in sub-populations of the differentiated culture. Our results suggest that TGFβ1 suppresses ESC chondrogenic induction and the degree of suppression is dependent on the differentiation-stage of the ESC. Our finding that TGF can sustain an undifferentiated population of hESCs within the differentiation culture suggests that caution should be exercised when using this growth factor as an ESC chondrogenic inducer and highlights the importance of close examination of classically known differentiation inducer when applying in the context of ESC-based tissue engineering.
Part two: Stem cells differentiation is influenced not only by bioactive element in the form of growth factors, but also the biochemical cues and biophysical property including the topography and stiffness of the material that is in contact with the cells. There are increasing efforts to develop scaffolds that mimic physiological aspects of the structure and function of natural extracellular matrix (ECM). Cartilage ECM is predominantly composed of proteoglycan, with massive glycoaminoglycan side chains, and type II collagen. We compared three different ECM molecules, collagen type 2 (Col2), chondroitin sulphate (CS), and hyaluronic acid (HA) for mesenchymal stem cell (MSC) chondrogenic differentiation using a microbead platform. Alginate microbead was coated with the 3 components and interaction with MSC in terms of cell attachment, proliferation and chondrogenic differentiation was determined. Our results identified the chondrogenic enhancement effect of Col2 and CS for MSC differentiation. In addition CS has the added advantage of the inhibiting hypertrophy development of the chondrocytes. Our results indicate that provision of appropriate biochemical environment can potentially be used to direct MSC chondrogenic differentiation.
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