Obesity and its related health complications cause billions of dollars in healthcare costs annually in the United States, and there are yet to be safe and long-lasting anti-obesity approaches. Using brown adipose tissue (BAT) is a promising approach, as it uses fats for energy expenditure. However, the effect of the microenvironment on human thermogenic brown adipogenesis and how to generate clinically relevant sized and functioning BAT are still unknown. In our current study, we evaluated the effects of endothelial growth medium exposure on brown adipogenesis of human brown adipose progenitors (BAP). We found that pre-exposing BAP to angiogenic factors promoted brown adipogenic differentiation and metabolic activity. We further 3D bioprinted brown and white adipose progenitors within hydrogel-based bioink with controllable physicochemical properties and evaluated the cell responses in 3D bioprinted environments. We used soft, stiff, and stiff-porous constructs to encapsulate the cells. All three types had high cell viability and allowed for varying levels of function for both white and brown adipocytes. We found that the soft hydrogel constructs promoted white adipogenesis, while the stiff-porous hydrogel constructs improved both white and brown adipogenesis and were the optimal condition for promoting brown adipogenesis. Consistently, stiff-porous hydrogel constructs showed higher metabolic activities than stiff hydrogel constructs, as assessed by 2-deoxy glucose uptake (2-DOG) and oxygen consumption rate (OCR). These findings show that the physicochemical environments affect the brown adipogenesis and metabolic function, and further tuning will be able to optimize their functions. Our results also demonstrate that 3D bioprinting of brown adipose tissues with clinically relevant size and metabolic activity has the potential to be a viable option in the treatment of obesity and type 2 diabetes.

Statement of Significance

One promising strategy for the treatment or prevention of obesity-mediated health complications is augmenting brown adipose tissues (BAT), which is a specialized fat that actively dissipate energy in the form of heat and maintain energy balance. In this study, we determined how pre-exposing human brown adipose progenitors (BAP) to angiogenic factors in 2D and how bioprinted microenvironments in 3D affected brown adipogenic differentiation and metabolic activity. We demonstrated that white and brown adipogenesis, and thermogenesis were regulated by tuning the bioprintable matrix stiffness and construct structure. This study not only unveils the interaction between BAP and 3D physiological microenvironments, but also presents a novel tissue engineered strategy to manage obesity and other related metabolic disorders.

中文翻译：

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可调的3D生物打印水凝胶对人褐色脂肪细胞行为和代谢功能的影响。

肥胖症及其相关的健康并发症在美国每年导致数十亿美元的医疗费用，并且还存在安全且持久的抗肥胖症方法。使用棕色脂肪组织（BAT）是一种很有前途的方法，因为它使用脂肪来消耗能量。然而，微环境对人类产热棕色脂肪形成的影响以及如何产生临床相关大小和功能的BAT仍是未知的。在我们目前的研究中，我们评估了内皮生长培养基暴露对人棕色脂肪祖细胞（BAP）棕色脂肪形成的影响。我们发现，将BAP预先暴露于血管生成因子可促进褐色脂肪形成分化和代谢活性。我们进一步在具有可控理化特性的水凝胶基生物墨水中进行3D生物打印的棕色和白色脂肪祖细胞，并评估了3D生物打印环境中的细胞反应。我们使用柔软，坚硬和坚硬多孔的结构来封装细胞。所有这三种类型均具有高细胞活力，并允许白色和棕色脂肪细胞具有不同水平的功能。我们发现，软水凝胶构建体促进白色脂肪形成，而硬孔水凝胶构建体改善白色和棕色脂肪形成，并且是促进棕色脂肪形成的最佳条件。一致地，如通过2-脱氧葡萄糖摄取（2-DOG）和耗氧率（OCR）所评估的，硬质多孔水凝胶构建体显示出比硬质水凝胶构建体更高的代谢活性。这些发现表明，理化环境会影响棕色脂肪的生成和代谢功能，进一步的调节将能够优化其功能。我们的结果还证明，具有临床相关大小和代谢活性的棕色脂肪组织的3D生物打印有可能成为治疗肥胖症和2型糖尿病的可行选择。

重要声明

一种治疗或预​​防肥胖症介导的健康并发症的有前途的策略是增加棕色脂肪组织（BAT），后者是一种特殊的脂肪，可以以热量的形式主动耗散能量并保持能量平衡。在这项研究中，我们确定了如何将人类棕色脂肪祖细胞（BAP）预先暴露于2D血管生成因子，以及3D的生物打印微环境如何影响棕色脂肪形成分化和代谢活性。我们证明了白色和棕色脂肪形成和生热作用是通过调节可生物印刷的基质刚度和构建结构来调节的。这项研究不仅揭示了BAP和3D生理微环境之间的相互作用，而且提出了一种新颖的组织工程化策略来控制肥胖症和其他相关的代谢性疾病。