Differential responses to folic acid in an established keloid fibroblast cell line are mediated by JAK1/2 and STAT3

Abstract

Keloids are a type of disordered scar formation which not only show heterogeneity between individuals and within the scar itself, but also share common features of hyperproliferation, abnormal extra-cellular matrix deposition and degradation, as well as altered expression of the molecular markers of wound healing. Numerous reports have established that cells from keloid scars display Warburg metabolism—a form of JAK2/STAT3-induced metabolic adaptation typical of rapidly dividing cells in which glycolysis becomes the predominant source of ATP over oxidative phosphorylation (OxPhos). Using the JAK1/2 inhibitor ruxolitinib, along with cells from patients with STAT3 loss of function (STA3 LOF; autosomal dominant hyper IgE syndrome) we examined the role of JAK/STAT signaling in the hyperproliferation and metabolic dysregulation seen in keloid fibroblasts. Although ruxolitinib inhibited hyperactivity in the scratch assay in keloid fibroblasts, it paradoxically exacerbated the hyper-glycolytic state, possibly by further limiting OxPhos via alterations in mitochondrial phosphorylated STAT3 (pSTAT3Ser727). In healthy volunteer fibroblasts, folic acid exposure recapitulated the exaggerated closure and hyper-glycolytic state of keloid fibroblasts through JAK1/2- and STAT3-dependent pathways. Although additional studies are needed before extrapolating from a representative cell line to keloids writ large, our results provide novel insights into the metabolic consequences of STAT3 dysfunction, suggest a possible role for folate metabolism in the pathogenesis of keloid scars, and offer in vitro pre-clinical data supporting considerations of clinical trials for ruxolitinib in keloid disorder.

The JAK–STAT pathway in keloid pathogenesis: a systematic review with qualitative synthesis

“…Alterations in mitochondrial phosphorylated STAT3 found in KFs, limiting oxidative phosphorylation, was suggested as an explanation for this contradictory finding. Finally, the authors of this study suggested a possible role for folate metabolism in keloids pathogenesis mediated by JAK1/2 and STAT, 17 which has not been described in other studies.…”

“…No additional studies were retrieved with reference list checking. Thirteen studies reported experiments with JAK and/or STAT inhibitors 8,14,15,17–26 . Seven studies reported on JAK and/or STAT expression in (keloid) cells or tissues without involving drug testing 9,27–32 .…”

“…Moreover, the effect of thirteen different JAK and/or STAT inhibitors in keloid tissues and cells was investigated. These drugs and molecules include the tyrosine kinase inhibitor AG490, the plant‐derived Cucurbitacin I, the curcumin analogue ASC‐J9, the JAK1/2 inhibitor ruxolitinib, STAT3 siRNA, SODNs, STA‐21, niclosamide, S2I‐201, nintedanib, NTP, sulforaphane and green tea polyphenol epigallocatechin gallate 8,14,15,17–26 . Keloid progression was inhibited by these drugs and molecules, as demonstrated by different processes including reduced collagen production, cell proliferation and migration, increased cell cycle arrest and apoptosis, enhanced antioxidant responses, decreased (paracrine) signalling and decreased profibrotic gene expression.…”

“…Thirteen studies reported experiments with JAK and/or STAT inhibitors. 8,14,15,[17][18][19][20][21][22][23][24][25][26] Seven studies reported on JAK and/or STAT expression in (keloid) cells or tissues without involving drug testing. 9,[27][28][29][30][31][32] All included articles were preclinical studies with in vitro human keloid cells, human keloid biopsies or a combination of both.…”

An updated review of the immunological mechanisms of keloid scars

“…From a metabolic viewpoint, keloids exhibit accelerated glycolysis reminiscent of Warburg metabolism, a unique adaptive state presumably induced by JAK2/STAT3 ( 50 , 221 ). Interestingly, an in vivo study demonstrated regulation of keloid fibroblast activity at the cost of a worsened hyperglycolytic state with JAK1/2 blockade ( 222 ). Epigallocatechin-3-gallate (EGCG), a green tea extract, has been found to possess chemopreventive properties, including suppression of STAT3 signaling, potentially inhibiting keloid growth ( 219 ).…”