The epigenome as a putative target for skin repair: the HDAC inhibitor Trichostatin A modulates myeloid progenitor plasticity and behavior and improves wound healing

Abstract

Background The molecular pathways that drive bone marrow myeloid progenitors (BMMP) development are very well understood and include a tight controlled multi-stage gene hierarch. Monocytes are versatile cells that display remarkable plasticity and may give rise to specific subsets of macrophages to proper promote tissue homesostasis upon an injury. However, the epigenetic mechanisms that underlie monocyte differentiation into the pro-inflammatory Ly6C high or the repairing Ly6C low subsets are yet to be elucidated. We have previously shown that Epigenetic mechanisms Histone Deacetylase (HDAC) dependent are crucial for monocyte behavior and plasticity and in this work, we propose that this same mechanism underlies BMMP plasticity upon an inflammatory challenge in vivo. Methods BMMP were culture in the presence of GM-CSF alone or in combination with HDAC inhibitor (iHDAC) and phenotyped by flow cytometry, immune staining or western blot. iHDAC was topically added to skin wounds for 7 consecutive days and wound healing was monitored by flow cytometry and histopathological analysis. Results When BMMP were cultured in the presence of iHDAC, we showed that the CD11b low /Ly6C low subset was the specific target of iHDAC that underwent chromatin hyperacetylation in vitro. Upon 13 days in the presence of iHDAC, BMMP gave rise to very elongated macrophages, that in turn, displayed a remarkable plasticity in a HDAC activity dependent fashion. HDAC-dependent cell shape was tight related to macrophage behavior and phenotype through the control of iNOS protein levels, showing that chromatin remodeling is a key component of macrophage plasticity and function. We then hypothesized that iHDAC would modulate the inflammatory response and favor tissue repair in vivo. To test this hypothesis, we topically added iHDAC to skin wounds during 7 consecutive days and followed tissue repair dynamics. In fact, iHDAC treated skin wounds presented an increase in wound closure at day 5 that was correlated to an enrichment in the CD11b low /Ly6C low subset and in very elongated F4/80 positives macrophages in vivo, fully recapitulating the behavior previously observed in vitro. Conclusion Our work provides the biological basis that connects chromatin remodeling to phenotypic plasticity, which in turn, may become a tractable therapeutic strategy in further translational studies. Electronic supplementary material The online version of this article (10.1186/s12967-019-1998-9) contains supplementary material, which is available to authorized users.

Epigenetic immune-modulation by Histone Deacetylase Activity (HDAC) of tissue and organ regeneration inXenopus laevis

“…We showed that in the absence of HDAC activity the number of LURP-GFP + cells in the regenerative bud was increased without a consistent increase in the levels of endogenous mRNA levels of LURP. Interpreting this result, we found a stinking similar pattern observed in mice upon iHDAC treatment of myeloid precursors at 24 hpa (Cabanel et al, 2015; Cabanel et al, 2019). While control group displayed a lower number of LURP-GFP+ cells, these cells might express high levels of this protein being classified as LURP-GFP high sub-set (pro-inflammatory monocytes).…”

“…In this work we showed that the treatment of regenerating swimming tadpoles, starting at stage 40, with HDAC inhibitors (iHDACs) impairs regeneration and leads to a lack of regenerative ability. In addition, we have recently shown that iHDAC treatment of mammalian myeloid cells both in vitro and in vivo disrupts myeloid differentiation favoring cell cycling in detriment of cell differentiation (Cabanel et al, 2015; Cabanel, da Costa, El-Cheikh, & Carneiro, 2019). As a consequence, myeloid progenitors display a high plastic phenotype favoring an anti-inflammatory functional profile.…”

Epigenetic regulation of cellular functions in wound healing

“…Upon differentiation, HDACs further promote the M1 phenotype, while class I-IIa HDAC inhibitor trichostatin A promotes elongated shape and potential to transition into a M2 phenotype through chromatin changes specifically involving H4K16. 127,128 Trichostatin A topically added to murine wounds mirrored the behaviour observed in vitro resulting in enhanced wound closure. 128 Class I HDACs downregulate myeloid plasticity and favour differentiation into "pro-inflammatory" M1 macrophages, while inhibition renews macrophage plasticity.…”

“…128 Class I HDACs downregulate myeloid plasticity and favour differentiation into "pro-inflammatory" M1 macrophages, while inhibition renews macrophage plasticity. 128 But HDACs do not all have the same function, even within the same class, as gene profiling of peripheral blood monocytes (PBMCs) in patients with type 2 DM and DFUs demonstrated differential regulation of HDACs in the context of increased pro-inflammatory mediators. 129,130 Among DFU patients, significant upregulation of class I HDACs 1,…”

A review of epigenetic regulation in wound healing: Implications for the future of wound care

“…This differential regulation may be useful if specific HDACs and downstream pathways can be targeted during healing. For example, TSA, which is HDAC class I‐IIa specific accelerates skin closure and enhances monocyte and macrophage populations in the wound bed, 95 while Sirtinol (class III HDAC inhibitor) slows healing 96 . Thus, specific blockade of HDAC III accelerates keratinocyte proliferation and enhances growth factor transcription, including IGF‐1, FGF, and EGF 96 …”