Background: We previously reported that keloid nodules had such specific structures that higher expression of autophagy proteins and glycolytic markers was observed in the central zone fibroblasts than in marginal zone fibroblasts. The purpose of this study is to investigate how keloid nodules play a role in metabolic activity for continuous expansion. Methods: A total of 57 nodules were randomly chosen from seven keloid samples and divided into four groups of disease duration (2, 4, 6, and 17 years). Immunohistochemical and immunofluorescent analyses were performed. Results: Immunohistochemical analysis with anti-CD-31 confirmed that the nodules had a structure with a greater number of vessels in the marginal zone than in the central zone. The density of fibroblasts in nodules (190.29 ± 64.45) was significantly higher than that of surrounding connective tissue (140.18 ± 63.94) (P < 0.05). The area of each nodule increased for 2 to 4 years, then decreased, graphically represented by an approximately horizontal line, to 17 years. The ratio of total nodule area/dermis area increased as disease duration lengthened. The maximum ratio was the 17-year group at 48.01%. The nodule number/dermis area ratio rose approximately with advancing disease duration. Conclusions: Instead of increasing the size of the nodules, their number and total area increased within the keloid lesions. We believe that the keloid nodules must play an important role in energy metabolic activity for continuous growth by increasing in number and total area.

Background: A keloid is composed of several nodules, which are divided into two zones: the central zone (CZ; a hypoxic region) and the marginal zone (MZ; a normoxic region). Keloid nodules play a key role in energy metabolic activity for continuous growth by increasing in number and total area. In this study, we aimed to investigate the roles of the zones in the execution of the Warburg effect and identify which microRNAs regulate this phenomenon in keloid tissue. Methods: Eleven keloids from patients were used. Using immunohistochemical analysis, 179 nodules were randomly chosen from these keloids to identify glycolytic enzymes, autophagic markers, pyruvate kinase M (PKM) 1/2, and polypyrimidine tract binding protein 1 (PTBP1). Western blot and qRT-PCR tests were also performed for PKM, PTBP1, and microRNAs (miR-133b and miR-200b, c). Results: Immunohistochemical analysis showed that the expression of the autophagic (LC3, p62) and glycolytic (GLUT1, HK2) were significantly higher in the CZ than in the MZ. PKM2 expression was significantly higher than PKM1 expression in keloid nodules. Furthermore, PKM2 expression was higher in the CZ than in the MZ. However, PKM1 and PTBP1 expression levels were higher in the MZ than in the CZ. The qRT-PCR analysis showed that miR-133b-3p was moderately downregulated in the keloids compared with its expression in the normal skin tissue. Conclusions: The Warburg effect occurred individually in nodules. The MZ presented PKM2-positive fibroblasts produced by activated PTBP1. In the CZ, PKM2-positive fibroblasts produced lactate. MiR-133b-3p was predicted to control the Warburg effect in keloids.