Search

A functional network of blood vessels is essential for organ growth and homeostasis. Yet, how the vasculature matures and maintains adult homeostasis remains elusive in live mice. By longitudinally tracking the same neonatal endothelial cells (ECs) over days to weeks, we found that capillary plexus expansion is driven by network-wide vessel regression and transient angiogenesis. A fixed number of neonatal ECs rearrange their positions to evenly distribute throughout the developing plexus and become positionally stable in adulthood. Upon injury, while neonatal ECs are predisposed to die, adult ECs survive through a plasmalemmal self-repair response. Furthermore, adult neighboring ECs reactivate migration to assist vessel repair. Lastly, neonatal vessel regression and adult vascular maintenance are orchestrated by temporally restricted VEGFR2 dependent signaling. Our work sheds light on fundamental cellular mechanisms that underlie both vascular maturation and adult homeostasisin vivo.

Epidermal and interfollicular stem cell proliferation and differentiation are controlled in a circadian manner, in order to anticipate the daily environmental challenges. For this reason, examining the circadian transcriptome of interfollicular stem cells has become a central technique for functional skin studies. In this chapter, we describe a widely adopted protocol for the isolation and analysis of circadian rhythms in adult stem cells of the epidermis.

Skin aging is characterized by structural and functional changes that lead to slower wound healing and higher rate of infections, which contribute to age-associated frailty. This likely depends on synergy between alterations in the local microenvironment and stem cell–intrinsic changes, underscored by pro-inflammatory microenvironments that drive pleotropic changes. To date, little is known about the precise nature and origin of the proposed age-associated inflammatory cues, or how they affect different tissue resident cell types. Based on deep single-cell RNA-sequencing of the entire dermal compartment, we now provide a comprehensive understanding of the age-associated changes in all skin cell types. We show a previously unreported skew towards an IL-17–expressing phenotype of Th cells, γδ T cells and innate lymphoid cells in aged skin. Aberrant IL-17 signaling is common to many autoimmune (e.g., rheumatoid arthritis and psoriasis) and chronic inflammatory diseases. Importantly, in vivo blockade of IL-17–triggered signaling during the aging process reduces the pro-inflammatory state by affecting immune and non-immune skin cells of both dermis and epidermis. Strikingly, IL-17 neutralization significantly delays the appearance of age-related traits, such as decreased epidermal thickness, increased cornified layer thickness and ameliorated hair follicle stem cell activation and hair shaft regeneration. Our results indicate that the aged skin shows chronic and persistent signs of inflammation, and that age-associated increased IL-17 signaling could be targeted as a strategy to prevent age-associated skin ailments in elderly.