Introduction

Mesenchymal stem cells (MSCs) represent a very important cell source in the field of regenerative medicine and for bone and cartilage tissue engineering applications. Three-dimensional (3D) bioprinting has the potential to improve the classical tissue engineering concept as this technique allows the printing of cells with high spatial control of cell allocation within a 3D construct. In this study, we systematically compared different hydrogel blends for 3D bioprinting of MSCs by testing their cytocompatibility, ability to support osteogenic differentiation and their mechanical properties. In addition, we compared four different MSC populations isolated from different human tissues for their osteogenic differentiation capacity in combination with different hydrogels. The aim of this study was to identify the best MSC source and the most suitable hydrogel blend for extrusion-based bioprinting of 3D large-scaled osteogenic constructs.

Materials and Methods

MSCs were isolated from different tissues (umbilical cord, adipose tissue, bone marrow). MSCs were seed onto or into different hydrogels and analyzed for cell viability, proliferation and osteogenic differentiation. In addition, viscoelastic properties of the hydrogels were determined. MSC-containing cubes with the size of 1 cm³ were printed by means of 3D extrusion-based bioprinting and analyzed by (immuno)histology for cell survival and production of a calcified extracellular matrix.

Results

Adipose tissue derived MSCs (ASCs) showed the highest osteogenic differentiation potential. A complex hydrogel blend consisting of fibrin, gelatin, hyaluronic acid, glycerol (F/G/H/Gl), tuned with hydroxyapatite, showed the best viscoelastic properties in combination with an excellent biocompatibility towards ASCs. This cell/hydrogel combination was used to bioprint 3D cubes. The cubes showed good mechanical stability and the printed ASCs were viable and able to calcify the hydrogel after bioprinting.

Conclusions

The combination of the HA-tuned F/G/H/Gl hydrogel blend along with ASCs can be considered as a very promising bioink for 3D bioprinting of artificial bone tissue equivalents for prospective applications in tissue engineering and regenerative medicine.

中文翻译：

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检查水凝胶和间充质干细胞来源的人工成骨组织的生物打印。

介绍

间充质干细胞（MSCs）是再生医学领域以及骨和软骨组织工程应用中非常重要的细胞来源。三维（3D）生物打印具有改善经典组织工程学概念的潜力，因为该技术允许在3D构造中对细胞进行高度空间控制的细胞打印。在这项研究中，我们通过测试MSCs的细胞相容性，支持成骨分化的能力及其机械性能，系统地比较了不同的水凝胶混合物用于MSC的3D生物打印。此外，我们比较了从不同人体组织中分离得到的四种不同MSC群体与不同水凝胶的成骨分化能力。

材料和方法

从不同的组织（脐带，脂肪组织，骨髓）中分离出MSC。将MSCs接种到不同的水凝胶上或其中，并分析细胞活力，增殖和成骨分化。另外，测定了水凝胶的粘弹性。通过基于3D挤压的生物打印法打印出大小为1 cm ³的含MSC的立方体，并通过（免疫）组织学分析细胞存活率和钙化细胞外基质的产生。

结果

来自脂肪组织的MSC（ASC）显示出最高的成骨分化潜能。由纤维蛋白，明胶，透明质酸，甘油（F / G / H / Gl）组成的复合水凝胶混合物，经羟基磷灰石微调，显示出最佳的粘弹性质，并具有与ASCs优异的生物相容性。该细胞/水凝胶组合用于生物打印3D立方体。立方体显示出良好的机械稳定性，并且印刷的ASC可行，并且在生物印刷后能够钙化水凝胶。

结论

经过HA调节的F / G / H / G1水凝胶掺合物与ASC的结合可以被视为非常有前途的生物墨水，可用于对组织工程和再生医学进行前瞻性应用的人造骨组织等效物的3D生物打印。