Abnormal Balance between Proliferation and Apoptotic Cell Death in Fibroblasts Derived from Keloid Lesions

Abstract

A new culture model was developed to study the role of proliferation and apoptosis in the etiology of keloids. Fibroblasts were isolated from the superficial, central, and basal regions of six different keloid lesions by using Dulbecco's Modified Eagle Medium containing 10% fetal calf serum as a culture medium. The growth behavior of each fibroblast fraction was examined in short-term and long-term cultures, and the percentage of apoptotic cells was assessed by in situ end labeling of fragmented DNA. The fibroblasts obtained from the superficial and basal regions of keloid tissue showed population doubling times and saturation densities that were similar to those of age-matched normal fibroblasts. In contrast, the fibroblasts from the center of the keloid lesions showed significantly reduced doubling times (25.9 +/- 6.3 hours versus 43.5 +/- 6.3 hours for normal fibroblasts) and reached higher cell densities. In long-term culture, central keloid fibroblasts formed a stratified three-dimensional structure, contracted the self-produced extracellular matrix, and gave rise to nodular cell aggregates, mimicking the formation of keloid tissue. Apoptotic cells were detected in both normal and keloid-derived fibroblasts, but their numbers were twofold higher in normal cells compared with all keloid fibroblasts. To examine whether apoptosis mediates the therapeutic effect of ionizing radiation on keloids, the cells were exposed to gamma rays at a dose of 8 Gy. Under these conditions, a twofold increase in the population of apoptotic cells was detected. These results indicate that the balance between proliferation and apoptosis is impaired in keloid fibroblasts, which could be responsible for the formation of keloid tumors. The results also suggest that keloids contain at least two different fibroblast fractions that vary in growth behavior and extracellular matrix metabolism.

RETRACTED: Upregulation of microRNA-205 suppresses vascular endothelial growth factor expression-mediated PI3K/Akt signaling transduction in human keloid fibroblasts

“…Whereas the pathophysiological mechanism finally leading to keloid formation remains partially revealed, 8 it is commonly recognized that keloid is a result of the unbalanced cellular dynamics caused by overabundant fibroblast proliferation and insufficient fibroblast apoptosis. 9 In this regard, several studies infer that factors related to tumor formation and cytokine function may play crucial roles in the formation of keloids and influence their development. 10,11 MicroRNAs (miRs) belong to an endogenous class of small non-coding RNAs which function through inhibition of translation levels or fracture of targeted mRNAs.…”

Premature Collagen Fibril Formation, Fibroblast-Mast Cell Interactions and Mast Cell-Mediated Phagocytosis of Collagen in Keloids

“…In this study cell-to-cell contact between fibroblasts and mast cells was also (2014) has shown that genetic ablation of connective tissue type mast cells fails to prevent bleomycin induced lung fibrosis [45]. Keloid fibroblasts have been isolated from keloid tissue and grown in cell culture; compared to normal cells keloid fibroblasts have shown differences in growth properties and gene expression [46,47]. Furthermore epigenetic changes have been implicated in the development of fibrosis in keloids [48].…”

Keloids: Current concepts of pathogenesis (Review)

“…The two oncogenes ribosomal protein 18 and Stat-3, both important proteins for cell proliferation, may be linked to keloid pathogenesis (55,56). Another important factor related to keloid formation may be a dysregulation of apoptosis (57,58). If keloid fibroblasts fail to undergo physiologically programmed cell death and, thus, continue to produce and secrete connective tissue beyond the period expected in normal scar formation, the hypertrophic and progressive nature of keloids may result (59).…”