Defining the lineage of thermogenic perivascular adipose tissue [Thoracic PVAT]

Brown adipose tissue can expend large amounts of energy and thus increasing its amount or activity is a promising therapeutic approach to combat metabolic disease. In humans, major deposits of brown fat cells are found intimately associated with large blood vessels, corresponding to perivascular adipose tissue (PVAT). However, the cellular origins of PVAT are poorly understood. We applied single cell transcriptomic analyses, ex vivo adipogenesis assays, and genetic fate mapping to determine the identity of perivascular adipocyte progenitors. In mice, we found that thoracic PVAT develops from a fibroblastic lineage, consisting of progenitor cells (Pdgfra+; Ly6a+; Pparg-) and preadipocytes (Pdgfra+; Ly6a+; Pparg+). Progenitor and preadipocyte cells in PVAT shared transcriptional similarity with analogous cell types in white adipose tissue, pointing towards a conserved hierarchical structure of adipose lineage cells. Interestingly, the aortic adventitia of adult animals contained a novel population of adipogenic smooth muscle cells (SMCs) (Myh11+; Pdgfra-; Pparg+) that contributed to perivascular adipocyte formation. Similarly, human PVAT contained presumptive fibroblastic and SMC-like adipocyte progenitors, as revealed by single nucleus RNAseq. Taken together, these studies define distinct populations of progenitor cells for thermogenic PVAT, providing a foundation for developing strategies to augment brown fat activity. Single Cell RNA Sequencing of cells from digested mouse aortas and associated perivascular adipose tissue at ages E18,P3, Adulthood (13 weeks) and single nucleus sequencing of human perivascular adipose tissue. For mice, individual analysis of each sample as well as integration of E18 and P3 datasets was performed. For humans samples, datasets were integrated and analyzed.棕色脂肪组织（Brown adipose tissue）可消耗大量能量，因此增加其数量或活性是对抗代谢性疾病的极具前景的治疗策略。在人类体内，棕色脂肪细胞的主要沉积部位与大血管紧密结合，该组织即为血管周围脂肪组织（perivascular adipose tissue, PVAT）。然而，目前对PVAT的细胞起源尚缺乏深入认知。本研究采用单细胞转录组分析、体外脂肪生成实验及遗传命运图谱技术，旨在鉴定血管周围脂肪细胞祖细胞的身份。在小鼠模型中，胸腔PVAT起源于成纤维细胞谱系，该谱系包含祖细胞（Pdgfra+; Ly6a+; Pparg-）与前脂肪细胞（Pdgfra+; Ly6a+; Pparg+）。PVAT中的祖细胞与前脂肪细胞与白色脂肪组织中的同类细胞具有相似的转录特征，提示脂肪谱系细胞存在保守的层级组织结构。值得注意的是，成年动物的主动脉外膜中存在一类全新的成脂性平滑肌细胞（smooth muscle cells, SMCs）群体（Myh11+; Pdgfra-; Pparg+），这类细胞可参与血管周围脂肪细胞的形成。同理，通过单细胞核RNA测序结果显示，人类PVAT中也存在推测的成纤维细胞样与平滑肌细胞样脂肪祖细胞。综上，本研究明确了产热型PVAT的不同祖细胞群体，为开发增强棕色脂肪活性的治疗策略奠定了理论基础。本数据集包含消化后的小鼠主动脉及相关血管周围脂肪组织在胚胎期18天（E18）、出生后3天（P3）、成年（13周龄）阶段的单细胞RNA测序数据，以及人类血管周围脂肪组织的单细胞核测序数据。针对小鼠样本，本研究开展了单样本独立分析，并整合了E18与P3阶段的数据集；针对人类样本，则完成了数据集的整合与分析。