Hypoxia improves hair inductivity of dermal papilla cells via nuclearNADPHoxidase 4‐mediated reactive oxygen species generation'

Abstract

Summary Background Dermal papilla cells (DPCs) play a key role in hair regeneration and morphogenesis. Therefore, tremendous efforts have been made to promote DPC hair inductivity. Objectives The aim of this study was to investigate the mitogenic and hair inductive effects of hypoxia on DPCs and examine the underlying mechanism of hypoxia‐induced stimulation of DPCs. Methods DPCs' hair inductivity was examined under normoxia (20% O2) and hypoxia (2% O2). Results Hypoxia significantly increased the proliferation and delayed senescence of DPCs via Akt phosphorylation and downstream pathways. Hypoxia upregulated growth factor secretion of DPCs through the mitogen‐activated protein kinase pathway. Hypoxia‐preconditioned DPCs induced the telogen‐to‐anagen transition in C3H mice, and also enhanced hair neogenesis in a hair reconstitution assay. Injected green fluorescent protein‐labelled DPCs migrated to the outer root sheath of the hair follicle, and hypoxia‐preconditioning increased survival and migration of DPCs in vivo. Conditioned medium obtained from hypoxia increased the hair length of mouse vibrissa follicles via upregulation of alkaline phosphatase, vascular endothelial growth factor, and glial cell line‐derived neurotrophic factor. We examined the mechanism of this hypoxia‐induced stimulation, and found that reactive oxygen species (ROS) play a key role. For example, inhibition of ROS generation by N‐acetylcysteine or diphenyleneiodonium treatment attenuated DPCs' hypoxia‐induced stimulation, but treatment with ROS donors induced mitogenic effects and anagen transition. NADPH oxidase 4 is highly expressed in the DPC nuclear region, and NOX4 knockout by CRISPR‐Cas9 attenuated the hypoxia‐induced stimulation of DPCs. Conclusions Our results suggest that DPC culture under hypoxia has great advantages over normoxia, and is a novel solution for producing DPCs for cell therapy. Whatʼs already known about this topic? Dermal papilla cells (DPCs) play a key role in hair regeneration and morphogenesis, but they are difficult to isolate and expand for use in cell therapy. Tremendous efforts have been made to increase proliferation of DPCs and promote their hair formation ability. What does this study add? Hypoxia (2% O2) culture of DPCs increases proliferation, delays senescence and enhances hair inductivity of DPCs. Reactive oxygen species play a key role in hypoxia‐induced stimulation of DPC. What is the translational message? Preconditioning DPCs under hypoxia improves their hair regenerative potential, and is a novel solution for producing DPCs for cell therapy to treat hair loss.

Macrophage-Derived Extracellular Vesicle Promotes Hair Growth

“…This result is in line with a study showing the activated fibroblast-derived EVs could induce cell proliferation signaling in DP cells [43]. This could be very useful for large-scale production of DP cells in vitro for research studies and DP cells therapies [47,48], as cultured DP cells lose their ability of inducing and maintaining the HF. This also could maintain the ability of proliferation of DP cells in vivo.…”

“…A study compared the cultured DP cells from balding and non-balding scalp and found that balding DP cells showed characteristics of senescence, including loss of proliferation [46]. Cultured DP cells lose their ability of inducing hair follicle after sub-culturing in vitro [47], showing that DP cell proliferation is essential for the morphogenesis and growth of the HF [2]. In the current study, MAC-EVs were shown to have the capacity to induce proliferation of DP cells, which was further confirmed by upregulated PCNA expression.…”

Epiregulin promotes hair growth via EGFR‐medicated epidermal and ErbB4‐mediated dermal stimulation

“…The ROS generating system was further examined, and EREG increased cellular ROS level, but did not lead to ROS generation in the mitochondria of DPC (Figure ). The expression of Nox4 was high in the nucleus of DPCs, 14 and Nox4 silencing attenuated the ROS level, NOX4 expression and DPC stimulation by EREG, suggesting that EREG increased ROS generation through nuclear NOX4 expression in DPCs. It was reported that amphiregulin (AREG) and HB‐EGF have the same effect at increasing NOX1 expression in smooth muscle cells 25 .…”

Dermal Papilla Cells and Melanocytes Response to Physiological Oxygen Levels Depends on Their Interactions 

“…While this seems to contradict the expected relation between the available oxygen and the ROS formation, it is also known that spheroids represent a hypoxic environment [49,50]. Thus, the oxygen levels in the highly compact DP-hMel aggregates are also likely to be below 5%O 2 and lead to the formation of ROS by an alternative mechanism [19], as it was previously demonstrated to play a key role in the stimulation of DP cells inductivity [22]. Moreover, ROS increase in the 3D-cellular aggregates may also be a consequence of the improved tyrosinase activity which is, by itself, a ROS-generating oxidative step [51,52].…”

“…Previous studies demonstrated that in cultures performed under 21%O 2 (normoxia) both HF mesenchymal (DP and dermal sheath cells) [20] and epithelial [21] populations proliferate at lower rates than when respectively cultured at 6%O 2 or 4%O 2 . Moreover, under hypoxic conditions (2%O 2 ), DP cells viability, phenotype and inductivity are improved [18,22]. Further, hMel proliferation and melanin production are also higher at 1-5%O 2 than above normoxia [23].…”