Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
Biomaterials. 2011 Oct;32(29):6946-52. doi: 10.1016/j.biomaterials.2011.06.014. Epub 2011 Jul 1.
Despite significant advances in stem cell differentiation and tissue engineering, directing progenitor cells into three-dimensionally (3D) organized, native-like complex structures with spatially-varying mechanical properties and extra-cellular matrix (ECM) composition has not yet been achieved. The key innovations needed to achieve this would involve methods for directing a single stem cell population into multiple, spatially distinct phenotypes or lineages within a 3D scaffold structure. We have previously shown that specific combinations of natural and synthetic biomaterials can direct marrow-derived stem cells (MSC) into varying phenotypes of chondrocytes that resemble cells from the superficial, transitional, and deep zones of articular cartilage. In this current study, we demonstrate that layer-by-layer organization of these specific biomaterial compositions creates 3D niches that allow a single MSC population to differentiate into zone-specific chondrocytes and organize into a complex tissue structure. Our results indicate that a three-layer polyethylene glycol (PEG)-based hydrogel with chondroitin sulfate (CS) and matrix metalloproteinase-sensitive peptides (MMP-pep) incorporated into the top layer (superficial zone, PEG:CS:MMP-pep), CS incorporated into the middle layer (transitional zone, PEG:CS) and hyaluronic acid incorporated in the bottom layer (deep zone, PEG:HA), creates native-like articular cartilage with spatially-varying mechanical and biochemical properties. Specifically, collagen II levels decreased gradually from the superficial to the deep zone, while collagen X and proteoglycan levels increased, leading to an increasing gradient of compressive modulus from the superficial to the deep zone. We conclude that spatially-varying biomaterial compositions within single 3D scaffolds can stimulate efficient regeneration of multi-layered complex tissues from a single stem cell population.
尽管在干细胞分化和组织工程方面取得了重大进展，但将祖细胞定向分化为具有空间变化的机械性能和细胞外基质（ECM）组成的三维（3D）组织化、类似于天然的复杂结构尚未实现。实现这一目标所需的关键创新将涉及将单个干细胞群体定向分化为 3D 支架结构内多个空间上不同的表型或谱系的方法。我们之前已经表明，天然和合成生物材料的特定组合可以将骨髓来源的干细胞（MSC）定向分化为具有不同表型的软骨细胞，这些细胞类似于关节软骨的浅层、过渡层和深层的细胞。在本研究中，我们证明了这些特定生物材料组成的逐层组织可以创建 3D 龛位，允许单个 MSC 群体分化为具有区域特异性的软骨细胞，并组织成复杂的组织结构。我们的结果表明，具有软骨素硫酸盐（CS）和基质金属蛋白酶敏感肽（MMP-pep）的三层聚乙二醇（PEG）水凝胶（顶层为浅层区，PEG:CS:MMP-pep）、中间层为 CS（过渡区，PEG:CS）和底层为透明质酸（深层区，PEG:HA）的三层 PEG 水凝胶可以创建具有空间变化的机械和生化特性的类似于天然的关节软骨。具体来说，从浅层到深层，胶原 II 水平逐渐降低，而胶原 X 和蛋白聚糖水平增加，导致从浅层到深层的压缩模量逐渐增加。我们得出结论，单个 3D 支架内的空间变化的生物材料组成可以从单个干细胞群体中刺激多层复杂组织的有效再生。
