Department of Obstetrics and Gynecology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America.
PLoS One. 2011 Mar 31;6(3):e17834. doi: 10.1371/journal.pone.0017834.
Previous studies highlight a complex relationship between lineage and phenotype for adipose tissue macrophages (ATMs), adipose stem cells (ASCs), and adipocytes, suggesting a high degree of plasticity of these cells. In the present study, using a novel co-culture system, we further characterized the interaction between ATMs, ASCs and adipocytes.
Human adipocytes and the stromal vascular fraction containing ATMs and ASCs were isolated from human adipose tissue and co-cultured for 24 hours. FACS was used to characterize ATMs and ASCs before and after co-culture. Preadipocytes generated after co-culture were characterized by immunostaining for DLK (preadipocytes), CD14 and CD68 (ATMs), CD34 (ASCs), and Nile Red staining for lipid drops. qRT-PCR was used to quantify adipogenic markers such as C/EBPα and PPARγ. A novel fluorescent nanobead lineage tracing method was utilized before co-culture where fluorescent nanobeads were internalized by CD68 (+) ATMs.
Co-culture of adipocytes with ATMs and ASCs increased the formation of new preadipocytes, thereby increasing lipid accumulation and C/EBPα and PPARγ gene expression. Preadipocytes originating after co-culture were positive for markers of preadipocytes, ATMs and ASCs. Moreover, fluorescent nanobeads were internalized by ATMs before co-culture and the new preadipocytes formed after co-culture also contained fluorescent nanobeads, suggesting that new preadipocytes originated in part from ATMs. The formation of CD34(+)/CD68(+)/DLK (+) cell spheres supported the interaction of ATMs, ASCs and preadipocytes.
Cross-talk between adipocytes, ATMs and ASCs promotes preadipocyte formation. The regulation of this novel adipogenic pathway involves differentiation of ATMs to preadipocytes. The presence of CD34(+)/CD68(+)/DLK(+) cells grouped in spheres suggest that paracrine interactions between these cell types plays an important role in the generation and proliferation of new preadipocytes. This phenomenon may reflect the in vivo plasticity of adipose tissue in which ATMs play an additional role during inflammation and other disease states. Understanding this novel pathway could influence adipogenesis, leading to new treatments for obesity, inflammation, and type 2 diabetes.
之前的研究强调了脂肪组织巨噬细胞（ATMs）、脂肪干细胞（ASCs）和脂肪细胞之间的谱系和表型之间存在复杂关系，这表明这些细胞具有高度的可塑性。在本研究中，我们使用一种新的共培养系统，进一步研究了 ATMs、ASCs 和脂肪细胞之间的相互作用。
从人脂肪组织中分离出脂肪细胞和含有 ATMs 和 ASCs 的基质血管部分，并将其进行共培养 24 小时。共培养前后，采用流式细胞术对 ATMs 和 ASCs 进行表型鉴定。用 DLK（前体脂肪细胞）、CD14 和 CD68（ATMs）、CD34（ASCs）免疫染色和尼罗红染色鉴定共培养后生成的前体脂肪细胞的脂质滴。采用 qRT-PCR 定量分析脂肪生成标志物 C/EBPα 和 PPARγ。在共培养之前，采用一种新型的荧光纳米珠谱系示踪方法，将荧光纳米珠内化到 CD68（+）ATMs 中。
脂肪细胞与 ATMs 和 ASCs 共培养后，新前体脂肪细胞的形成增加，从而增加了脂质积累和 C/EBPα 和 PPARγ 基因的表达。共培养后形成的前体脂肪细胞表达前体脂肪细胞、ATMs 和 ASCs 的标志物。此外，共培养前 ATMs 内化了荧光纳米珠，共培养后形成的新前体脂肪细胞也含有荧光纳米珠，提示部分新前体脂肪细胞来源于 ATMs。CD34（+）/CD68（+）/DLK（+）细胞球体的形成支持 ATMs、ASCs 和前体脂肪细胞之间的相互作用。
脂肪细胞、ATMs 和 ASCs 之间的相互作用促进前体脂肪细胞的形成。这种新的脂肪生成途径的调节涉及 ATMs 向前体脂肪细胞的分化。CD34（+）/CD68（+）/DLK（+）细胞聚集在球体中，提示这些细胞类型之间的旁分泌相互作用在新前体脂肪细胞的生成和增殖中发挥重要作用。这种现象可能反映了脂肪组织在体内的可塑性，在炎症和其他疾病状态下，ATMs 发挥额外的作用。了解这种新途径可能会影响脂肪生成，为肥胖、炎症和 2 型糖尿病的新治疗方法提供依据。
