During tissue repair, myofibroblasts produce extracellular matrix (ECM) molecules for tissue resilience and strength. Altered ECM deposition can lead to tissue dysfunction and disease. Identification of distinct myofibroblast subsets is necessary to develop treatments for these disorders. Here, using extensive analysis of pro-fibrotic cells during mouse skin wound healing, fibrosis and aging; we identify distinct subpopulations of myofibroblasts, including cells identified as adipocyte precursors (APs). Multiple mouse models and transplantation assays demonstrate that AP proliferation, and not other myofibroblasts, is activated by CD301b-expressing macrophages through IGF1 and PDGFC. With age, wound bed APs and differential gene expression between myofibroblast subsets are reduced. Our findings identify multiple fibrotic cell populations and suggest the environment dictates functional myofibroblast heterogeneity, which is driven by fibroblast-immune interactions after wounding.

Highlights d Inhibiting dermal adipocyte lipolysis reduces inflammatory wound bed macrophages d Wound edge adipocytes dedifferentiate within hours after injury d Adipocyte lipolysis is needed for dedifferentiated adipocytes to populate wound beds d Dedifferentiated adipocytes generate wound bed myofibroblasts after injury

Summary Tissue growth and maintenance requires stem cell populations that self-renew, proliferate and differentiate. Maintenance of white adipose tissue (WAT) requires the proliferation and differentiation of adipocyte stem cells (ASCs) to form postmitotic, lipid-filled mature adipocytes. Here, we use the dynamic adipogenic program that occurs during hair growth to uncover an unrecognized regulator of ASC self-renewal and proliferation, Pdgfa, which activates Akt signaling to drive and maintain the adipogenic program in the skin. Pdgfa expression is reduced in aged ASCs and is required for ASC proliferation and maintenance in the dermis but not in other WATs. Our molecular and genetic studies uncover PI3K/Akt2 as a direct Pdgfa target, activated in ASCs during WAT hyperplasia and functionally required for dermal ASC proliferation. Our data therefore reveal active mechanisms that regulate ASC self-renewal in the skin and show that distinct regulatory mechanisms operate in different WAT depots.

Adipocytes are intimately associated with the dermal compartment of the skin, existing in a specialized dermal depot and displaying dynamic changes in size during tissue homeostasis. However, the roles of adipocytes in cutaneous biology and disease are not well understood. Traditionally, adipocytes within tissues were thought to act as reservoirs of energy, as thermal, or as structural support. In this review, we discuss recent studies revealing the cellular basis of the dynamic development and regenerative capacity of dermal adipocytes associated with the hair cycle and following injury. We discuss and speculate on potential roles of dermal adipocytes in cutaneous biology with an emphasis on communication during hair follicle growth and wound healing. Finally, we explore how alterations in the dermal adipose tissue may support clinical manifestations of cutaneous diseases such as lipodystrophy, obesity, and alopecia. ADIPOCYTE DEVELOPMENT AND HOMEOSTASIS IN THE SKIN

High-throughput single-cell assays increasingly require special consideration in experimental design, sample multiplexing, batch effect removal, and data interpretation. Here, we describe a lentiviral barcode-based multiplexing approach, CellTag Indexing, which uses predefined genetic barcodes that are heritable, enabling cell populations to be tagged, pooled, and tracked over time in the same experimental replicate. We demonstrate the utility of CellTag Indexing by sequencing transcriptomes using a variety of cell types, including long-term tracking of cell engraftment and differentiation in vivo. Together, this presents CellTag Indexing as a broadly applicable genetic multiplexing tool that is complementary with existing single-cell technologies. Electronic supplementary material The online version of this article (10.1186/s13059-019-1699-y) contains supplementary material, which is available to authorized users.