摘要目的:探讨瘢痕疙瘩和局限性硬皮病组织中周细胞的异质性及其演化轨迹差异，为研究2种皮肤纤维化疾病的致病机制和治疗靶点提供新的线索。方法:选取GEO和GSA-Human数据库中的3例局限性硬皮病、4例瘢痕疙瘩及其对应的邻近正常皮肤样本细胞的单细胞转录组测序数据，绘制数据的表达矩阵。采用R语言的Seurat 4.3.0包进行处理后分群绘制 t-SNE可视化图谱。采用Monocle 2.24.0包对其中的周细胞进行拟时序轨迹分析。 结果:瘢痕疙瘩和局限性硬皮病皮肤组织无监督聚类为19个不同的细胞群体，其中周细胞为C7、C11群，高表达PDGFRB和RGS5基因，占总细胞数的7.53%。周细胞进一步可分为8个亚群，拟时序分析发现基因表达变化主要有细胞命运1(fate 1)和细胞命运2(fate 2)2个分支轨迹，依照时序周细胞可分为5个状态(S1~S5);其中S4占前分支的绝大部分，代表最初状态的周细胞；S5构成细胞命运1分支的大部分，代表分化较早期状态的周细胞；S1、S2、S3构成命运2分支的大部分，其中S3代表分化中期状态的周细胞，而S1、S2则代表分化晚期状态的周细胞。在正常皮肤中，各分化状态的周细胞均匀分布，而瘢痕疙瘩周细胞主要分布于前支(S4)、分支1(S5)及分支2中的前一部分(S3)，分别代表初始、早期及分化中期的细胞状态，分支基因表达动态分析显示其高表达SOX4、COL4A1、COL6A3、AHR、CXCL3和IL1R1等基因；而局限性硬皮病的周细胞主要分布于分支2的中后部分(S1、S2)，代表分化末期的细胞，高表达ACTA2和MYH11等基因。结论:瘢痕疙瘩和局限性硬皮病中周细胞具有异质性以及不同的演化轨迹；瘢痕疙瘩周细胞更具有干细胞样特性，通过高表达与细胞干性、上皮-间质转换、侵袭性和免疫微环境调控相关的基因，对其侵袭性和复发的病理特性发挥重要作用；而局限性硬皮病中周细胞可能主要转分化为肌成纤维细胞，导致其纤维化病理表型。

abstractsObjective:To explore the cellular heterogeneity and the differences in branched trajectory of pericytes between keloids and localized scleroderma, and to provide new clues for the pathogenesis and therapeutic targets of the two skin fibrotic diseases.Methods:Single cell transcriptome sequencing (scRNA-seq) data of 3 cases of scleroderma, 4 cases of keloid and their corresponding 4 cases of adjacent normal skin samples were selected from GEO and GSA-Human databases, and the expression matrix of the data was drawn. Seurat 4.3.0 of R (4.2.2) was used to process the t-distributed stochastic neighbor embedding ( t-SNE) visualization map. Monocle 2.24.0 was used to analyze the pseudo-temporal trajectory of pericytes. Results:The unsupervised clustering of keloid and scleroderma skin tissues revealed 19 different cell populations, among which C7 and C11 cells were pericytes, marked by high expression levels of PDGFRB and RGS5 genes, accounting for 7.53% of the total cells. Pericytes can be further divided into 8 subgroups. Pseudo-temporal analysis revealed a branched trajectory with two major branches, that is, cell fate 1 and cell fate 2, which could be further divided into 5 cellular states of pericytes (S1-S5). S4 constituted the most of the prebranch, which represented the cellular state of the initial pericyte phenotype. S5 constituted the most of the cell fate 1 branch, which represented the early differentiation state of the pericyte phenotype. S1, S2, S3 constituted the most of the cell fate 2 branch. S3 represented the intermediate differentiation state of the pericyte phenotype, while S1 and S2 represented the terminal differentiation states of the pericyte phenotype. Compared with the uniform distribution of various differentiation states of pericytes in normal skin, the keloid pericytes mainly distributed in the prebranch (S4), cell fate 1 (S5) and the first half of cell fate 2 (S3), representing cellular states of the initial, early and intermediate phases of the pericyte phenotype. Branched expression analysis modeling revealed the overexpression of SOX4, COL4A1, COL6A3, AHR, CXCL3 and IL1R1 genes, et cetera. On the other hand, the localized scleroderma pericytes mainly distributed in the bottom half of cell fate 2 (S1, S2), representing the final differentiated phase of pericyte phenotype, which overexpressed ACTA2 and MYH11 genes.Conclusion:Pericytes in keloid and scleroderma are heterogenous and have different differentiation trajectories. Pericytes in keloid have stem-like characteristics, and play an important role in the pathologic characteristics of invasiveness and recurrence through high expression of genes related to cell stemness, epithelial-mesenchymal transition, invasiveness, and immune microenvironment regulation. However, pericytes in localized scleroderma may mainly transdifferentiate into myofibroblasts, leading to their fibrotic pathological phenotype.