Despite their outstanding potential and the success that has already been achieved with three-dimensional (3D) printed hydrogel scaffolds, there has been little investigation into their application in the regeneration of damaged or missing adipose tissue (AT). Due to their macroscopic shape, microarchitecture, extracellular matrix-mimicking structure, degradability and soft tissue biomimetic mechanical properties, 3D printed hydrogel scaffolds have great potential for use in aesthetic, structural and functional restoration of AT. Here, we propose a simple and cost-effective 3D printing strategy using gelatin-based ink to fabricate scaffolds suitable for AT engineering. The ink, successfully printed here for the first time, was prepared by mixing gelatin and methylenebisacrylamide (a crosslinker) to initiate the crosslinking reaction. The solution was then loaded into the cartridge (temperature T = 35 °C) of a pneumatic extrusion-based 3D printer and printed on a cooled surface (T = 4 °C) in the appropriate time window for ink printability as verified by rheological tests. Subsequently, the printed gelatin hydrogels were crosslinked at different temperatures to optimize their stability and fix the printed structure. The gelatin scaffolds crosslinked at 20 °C remained stable for 21 days at physiological temperature, with compressive mechanical properties mimicking those of AT (i.e. elastic modulus = 20 kPa). The 3D printed scaffolds showed no indirect cytotoxic effects on a 3T3-L1 pre-adipocyte cell line. Moreover, the printed scaffolds successfully promoted adhesion and proliferation of primary human pre-adipocytes, as demonstrated by LIVE/DEAD staining and Alamar Blue assay. The differentiation of primary human pre-adipocytes isolated from three different donors according to adipogenic phenotype was demonstrated by an increase in PPARγ gene expression detected by real-time PCR and accumulated lipid droplets stained by Oil Red O, thus proving the potential of the 3D printed gelatin hydrogels as scaffolds for AT engineering.

中文翻译：

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用于脂肪组织工程的化学交联明胶水凝胶的三维印刷。

尽管它们具有巨大的潜力，并且已经通过三维（3D）打印的水凝胶支架取得了成功，但很少研究对其在受损或缺失的脂肪组织（AT）再生中的应用。由于其宏观的形状，微结构，模拟细胞外基质的结构，可降解性和软组织的仿生机械性能，因此3D打印水凝胶支架在AT的美学，结构和功能恢复中具有巨大的潜力。在这里，我们提出了一种简单且具有成本效益的3D打印策略，该方法使用基于明胶的墨水来制造适用于AT工程的支架。通过将明胶和亚甲基双丙烯酰胺（交联剂）混合以引发交联反应，可以制备出在此首次成功印刷的油墨。然后将溶液装入基于气动挤压的3D打印机的墨盒（温度T = 35°C）中，并在适当的时间范围内在冷却表面（T = 4°C）上进行打印，以实现油墨的可印刷性，这已通过流变测试验证。随后，将印刷的明胶水凝胶在不同温度下交联以优化其稳定性并固定印刷的结构。在生理温度下在20°C交联的明胶支架在21天内保持稳定，其压缩机械性能与AT相似（即弹性模量= 20 kPa）。3D打印支架对3T3-L1前脂肪细胞系没有间接的细胞毒性作用。此外，如LIVE / DEAD染色和Alamar Blue分析所证明的，印刷的支架成功地促进了人类原代前脂肪细胞的粘附和增殖。