Tao Wang,1,* Liping Zhang,2,* Wei Chen,3 Yubin Long,3 Yingze Zhang,3– 6 Ling Wang,3 Zhiyong Hou3– 6 

1Department of Lower Limb Trauma, Beijing Jishuitan Hospital, Guizhou Hospital, Guiyang, Guizhou, People’s Republic of China; 2Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, People’s Republic of China; 3Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, People’s Republic of China; 4Engineering Research Center of Orthopedic Minimally Invasive Intelligent Equipment, Ministry of Education, Shanghai, People’s Republic of China; 5Key Laboratory of Biomechanics of Hebei Province, Shijiazhuang, Hebei, People’s Republic of China; 6NHC Key Laboratory of Intelligent Orthopaedic Equipment, Shijiazhuang, Hebei, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Zhiyong Hou, Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China. No. 139 Road Ziqiang, Shijiazhuang, Hebei, People’s Republic of China, Email drzyhou@gmail.com

Purpose: Necrotizing fasciitis (NF) is a scarce but potentially life-threatening infection. However, no research has reported the cellular heterogeneity in patients with NF. We aim to investigate the change of cells from deep fascia in response to NF by single-cell RNA-seq.
Methods: Fascia samples from NF patients (NF group, NG, n = 3) and volunteer (control group, CG, n = 4) were obtained and we utilized scRNA-seq to observe the variation of cells and differentially expressed genes. Then, multiplex staining and multispectral imaging and immunohistochemistry were used to be further verified.
Results: Our findings showed that three fibroblast subclusters (antigen-presenting Fib, mesenchymal Fib, and myoFib) and three macrophage subclusters (SPP1+ Mac0, IL1B+ Mac1, and SPP1+M2) were found to have increased proportions with distinct roles in NF patients. The balance of M1/M2 polarization may be the key therapeutic target to determine the outcome of NF. Furthermore, the levels of SAA1, PTX3, S100 family, MARCO, and STAB1 were up-regulated in different subclusters with anti-infection roles against NF, which were proven by immunohistochemistry. These proteins may act as a biomarker or even as a candidate therapy for NF.
Conclusion: Our findings revealed the potential anti-infection role of deep fascia during the procession of NF, helping us understand the immunologic function of fascia and provide novel insights for its therapeutic strategies for NF.

Keywords: necrotizing fasciitis, deep fascia, single-cell RNA-seq, M1/M2 polarization, fibroblast