Tracking the elusive fibrocyte: identification and characterization of collagen-producing hematopoietic lineage cells during murine wound healing.
Fibrocytes are a unique population of circulating cells reported to exhibit characteristics of both hematopoietic and mesenchymal cells, and play an important role in wound healing. However, putative fibrocytes have been found to lose expression of hematopoietic surface markers such as CD45 during differentiation, making it difficult to track these cells in vivo with conventional methodologies. In this study, to distinguish hematopoietic and nonhematopoietic cells without surface markers, we took advantage of the gene vav 1, which is expressed solely on hematopoietic cells but not on other cell types, and established a novel transgenic mouse, in which hematopoietic cells are irreversibly labeled with green fluorescent protein and nonhematopoietic cells with red fluorescent protein. Use of single-cell transcriptional analysis in this mouse model revealed two discrete types of collagen I (Col I) expressing cells of hematopoietic lineage recruited into excisional skin wounds. We confirmed this finding on a protein level, with one subset of these Col I synthesizing cells being CD45+ and CD11b+, consistent with the traditional definition of a fibrocyte, while another was CD45- and Cd11b-, representing a previously unidentified population. Both cell types were found to initially peak, then reduce posthealing, consistent with a disappearance from the wound site and not a loss of identifying surface marker expression. Taken together, we have unambiguously identified two cells of hematopoietic origin that are recruited to the wound site and deposit collagen, definitively confirming the existence and natural time course of fibrocytes in cutaneous healing.
Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University, Stanford, California, USA.
Hirotaka
H
Suga
Robert C
RC
Rennert
Melanie
M
Rodrigues
Michael
M
Sorkin
Jason P
JP
Glotzbach
Michael
M
Januszyk
Toshihiro
T
Fujiwara
Michael T
MT
Longaker
Geoffrey C
GC
Gurtner
D000818:Animals; D039481:CD11b Antigen / Q000378:metabolism; D058948:Cell Tracking / Q000379:methods; D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism / Q000637:transplantation; D015870:Gene Expression / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018380:Hematopoietic Stem Cell Transplantation / Q000379:methods*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D011401:Promoter Regions, Genetic / Q000235:genetics; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D059010:Single-Cell Analysis / Q000379:methods; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D014945:Wound Healing; D014947:Wounds and Injuries / Q000628:therapy; D000097573:Red Fluorescent Protein
D039481:CD11b Antigen; D024042:Collagen Type I; D049452:Green Fluorescent Proteins; D017493:Leukocyte Common Antigens; D008164:Luminescent Proteins; D051567:Proto-Oncogene Proteins c-vav; D053773:Transforming Growth Factor beta1; D000097573:Red Fluorescent Protein; C496619:Vav1 protein, mouse
Collagen; Fibrocytes; Hematopoietic cells; Surface markers; Wound healing