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Objective: As an aberrant response to cutaneous wound healing, keloid scarring is a challenge to cure, and its clinical management remains unsatisfactory. The purpose of this study was to investigate whether mitochondrial function and morphology were impaired in keloid pathology. Approach: Keloid fibroblasts (KFs) and normal skin fibroblasts (NFs) were isolated and cultured from excised samples. A real-time extracellular flux analyzer was used to monitor the oxygen consumption rate for evaluating the mitochondrial respiratory function. Real-time PCR or Western blot was performed to detect the levels of mRNAs or proteins, respectively, including those associated with the tricarboxylic acid cycle, mitochondrial fission and fusion, and mitochondrial biogenesis. The reactive oxygen species (ROS) level and the mitochondrial mass were measured by flow cytometry. Mitochondrial ultrastructure was observed by transmission electron microscopy. Results: Compared with NFs, KFs showed reduced basal oxidative respiration (p

Keloids exhibit metabolic reprogramming including enhanced glycolysis and attenuated oxidative phosphorylation. Hypoxia induces a series of protective responses in mammalian cells. However, the metabolic phenotype of keloid fibroblasts under hypoxic conditions remains to be elucidated. The present study aimed to investigate glycolytic activity, mitochondrial function and morphology, and the HIF1α and PI3K/AKT signaling pathways in keloid fibroblasts (KFB) under hypoxic conditions. Our results showed that hypoxia promoted proliferation, migration invasion and collagen synthesis and inhibited apoptosis in KFB. The mRNA levels, protein expressions and enzyme activities of glycolytic enzymes in KFB were higher than those in normal skin fibroblasts (NFB) under normoxia. Moreover, hypoxia remarkedly upregulated glycolysis in KFB. Decreased activities of mitochondrial complexes and abnormal mitochondria were detected in KFB under normoxic conditions and the damage was aggravated by hypoxia. An intracellular metabolic profile assay suggested hypoxia increased glycolytic parameters except glycolytic reserve but inhibited the key parameters of mitochondrial function apart from H+ leak. Protein levels of HIF1α and phosphorylation levels of the PI3K/AKT signaling pathway were upregulated in the context of 3% oxygen. Enhanced total reactive oxygen species (ROS), mitochondrial ROS (mitoROS) and antioxidant activities of KFB were observed in response to hypoxia. Additionally, autophagy was induced by hypoxia. Our data collectively demonstrated potentiated glycolysis and attenuated mitochondrial function under hypoxia, indicating that altered glucose metabolism regulated by hypoxia could be a therapeutic target for keloids.

Periostin, a secreted extracellular matrix protein, is highly expressed in wound healing and in various types of human cancer and is involved in angiogenesis. Keloids, considered dermal benign tumors, are granulomatous lesions characterized by capillary proliferation. However, the underlying regulatory mechanism of angiogenesis in keloids remains to be elucidated. The present study aimed to examine the effect of periostin on angiogenesis in keloids. The expression of periostin was upregulated and the vessel density was higher in human keloids compared with normal tissue, observed following staining with CD31 and CD105. Periostin demonstrated a markedly positive correlation with blood vessel density, which was assessed using CD31 staining (r=0.711; P

To observe the effects of conditioned medium from keloid fibroblasts under hypoxia on angiogenesis, and to investigate the role of hypoxic microenvironment in invasive growth of keloid.Primary keloid fibroblasts and human umbilical endothelial cells (HUVEC) were cultured as conventional method. Keloid fibroblasts were cultured either in a hypoxic incubator (2% O2) for 48 h or in a normoxic incubator (20% O2) as control. Then those cell culture mediums were collected and mixed with endothelial cell medium by the proportion of 1:1 as conditioned medium. The mRNA and secreted protein of pro-angiogenic factors such as vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and periostin of keloid fibroblasts under hypoxia were detected by real time PCR and ELISA. The proliferation, migration and invasion, tube formation of HUVEC cultured with conditioned medium were evaluated by CCK-8 assay, Transwell assay and matrigel tube formation assay, respectively.Hypoxia increased the expression of VEGF, Ang-1 and periostin in both mRNA (increased by 75%, 43% and 118% respectively, P0.05) and secreted protein (increased by 30.2%, 14.2% and 19.5% respectively, P0.05) levels; the proliferations of HUVEC in hypoxic conditioned medium in 1, 2 and 3 d were 0.67 +/- 0.07, 0.84 +/- 0.09 and 1.08 +/- 0.10 respectively, which were higher compared to those in control group (0.52 +/- 0.08, 0.72 +/- 0.10 and 0.91 + 0.14, P0.05); the numbers of migration, invasion and tube formation of HUVEC were (73.2 +/- 8.9), (56.3 +/- 12.5), (9.66 +/- 1.96) cells/HP, which were higher compared to those in control group [(59.0 +/- 8.0), 35.5 +/- 8.5), (6.5 +/- 1.87) cells/HP, P0.05].Hypoxia increases the expression of pro-angiogenic factors of keloid fibroblasts, and its conditioned medium under hypoxia could promote angiogenesis. The results suggest hypoxic microenvironment may play a significant role in the invasive growth of keloid by inducing angiogenesis.

Periostin, a secreted extracellular matrix protein, is involved in the wound healing and pathological process of various human cancers. Keloid scars are fibroproliferative tumor-like lesions and develop under local hypoxia. Using suppression subtractive hybridization, in a previous study, we found that periostin is overexpressed in keloids compared with hypertrophic scars. However, little is known about the regulation and function of periostin in keloids. In this study, we examined the effects of periostin on the bioactivity of keloid fibroblasts (KFs) in order to determine whether periostin is involved in hypoxia-stimulated keloid pathogenesis by measuring the expression levels of periostin in KFs cultured under hypoxic conditions. We also investigated the association between periostin and hypoxia-inducible factor-1α (HIF-1α). The mRNA, intracellular protein and secreted protein level of periostin was examined by RT-PCR (and quantitative PCR), western blot analysis and enzyme-linked immunosorbent assay (ELISA), respectively. We also used shRNA targeting periostin to knockdown its expression in the KFs. We report that hypoxia (2% O(2)) upregulates both HIF-1α and periostin expression in KFs. In addition, hypoxia-upregulated periostin expression was regulated by HIF-1α. The inhibition of periostin by short hairpin RNA decreased the hypoxia-stimulated proliferation, collagen synthesis, migration and invasion of KFs and altered the cell cycle, but did not affect apoptosis; treatment with recombinant human periostin protein reversed these effects. Periostin also activated the αvβ3 integrin-PI3K/Akt pathway in the KFs. These findings suggest that hypoxia initiates hyperplasia of KFs and increases periostin expression under hypoxic conditions; periostin is involved in the pathogenesis of keloids, which indicates that periostin may be a novel therapeutic target for keloids and other fibroproliferative disorders.

Objective The aim of this study was to examine the gene expression signatures of 2 types of excessive scarring, keloid and hypertrophic scar (HS), through the integrated bioinformatics analysis of multiple published gene expression profile datasets. Methods A literature search of microarray data published in focusing on keloid and HS was performed. The microarray data were reanalyzed to identify the common significantly dysregulated (CSD) genes. The experimental and statistical parameters of the studies were systematically evaluated to reveal any influences on the consensus findings among the studies. Overrepresentation analysis of gene ontology (GO) categories and pathways was used to explore the significantly dysregulated genes functionally associated with the pathogenesis of excessive scarring. Results Seven published microarray studies on keloid and 4 studies on HS were identified. A total of 64 CSD genes were identified in keloid; 9 upregulated CSD genes were identified in HS. The 48 consistently dysregulated genes that overlapped in least 1 keloid study and 1 HS study were defined as the CSD genes in excessive scarring. The differences in the variables associated with the study protocols and data management were systematically documented and evaluated. Activated GO categories and pathways related to skeletal development, binding, extracellular matrix-receptor interaction, and adhesion were found to have significance in excessive scarring, implying a common pathological basis for keloid and HS formation. Notably, the GO categories related to cancer and the TGF-beta signaling pathway were significantly enriched in keloids. Conclusions As gene signatures and molecular markers of excessive scarring, the identified CSD genes may be particularly relevant to disease pathogenesis and serve as new therapeutic targets.