Modulation of metallothionein isoforms is associated with collagen deposition in proliferating keloid fibroblasts in vitro

Abstract

The keloid fibroblast (KF) is known to have higher proliferative capacity than normal dermal fibroblast (NF). Metallothionein (MT), a metal-binding protein, has been reported to promote cell proliferation. In this study, we evaluated the expression of MT isoforms at the mRNA level in fetal bovine serum (FBS)-stimulated proliferating KF. Although the morphological appearance of NF and KF was similar when viewed under light, confocal and transmission electron microscopy, there was surprisingly a generally lower expression of MT isoforms in KF when compared with NF and also reduced MT staining in dermal fibroblasts of keloids as opposed to normal skin. Primary cultures of KF grown in 5% FBS or 10% FBS compared to without FBS demonstrated significantly higher proliferative activity and more abundant deposition of collagen. Contrary to expectation, MT-1A, -1F, -1G, -1X and -2A isoforms were significantly down-regulated in proliferating KF. Moreover, stimulating KF with TGF β1, which is known to promote collagen synthesis and keloid formation, increased expression of Collagen 1A and 3A genes accompanied by reduction in MT-2A gene expression. Furthermore, down-regulation of the MT-2A gene in proliferating KF by siRNA-mediated silencing enhanced cell proliferation with concomitant up-regulation of the NF-κB gene and 10 of 13 other NF-κB pathway-related genes analysed but no alteration of the Collagen 1 and Collagen 3 gene expression. It would appear that down-regulation of MT isoforms in proliferating KF, in particular MT-2A, enhances keloidogenesis with the possible involvement of the NF-κB signalling pathway.

Exosomes from mesenchymal stromal cells reduce murine colonic inflammation via a macrophage-dependent mechanism

“…Takano and colleagues demonstrated that transgenic mice with metallothionein overexpression were more resistant to neutrophilic lung inflammation and lung edema induced by intratracheal challenge with LPS (52). Metallothionein-2 has also been found to be a critical regulator of NF-κB signaling because its upregulation attenuates NF-κB activity in tumor cells, keloid fibroblastic cells, as well as cardiomyocyte cells (53)(54)(55)(56). In line with these studies, our results demonstrated the antiinflammatory effects of metallothionein-2 on both macrophages and mouse colitis models.…”

Dynamic biological changes in fibroblasts during hypertrophic scar formation and regression

“…Severe hypoxia and malnutrition act as a damaging stimulus, greatly increasing p53 expression and inducing cell cycle arrest and apoptosis . Fu et al (2011) cultured stem cells in vitro under 2% O 2 and serum‐deprived conditions to mimic ischaemic in vivo cartilage conditions . The results demonstrated that these ischaemic, malnourished conditions promoted stem cell apoptosis, and the extent of apoptosis was greater in serum deprivation alone than hypoxia alone .…”

Metallothioneins and zinc in cancer diagnosis and therapy

“…Cells entering the cell cycle require higher amounts of Zn, whereas most transcription factors required for the transcription of enzymes necessary to initiate DNA synthesis need zinc to form their zinc fingers (Kuppens and De Ley, 2006). Modulation of MT isoforms was also associated with collagen deposition in proliferating keloid fibroblasts in vitro (Toh et al, 2010). It can be concluded that a role of MTs is connected with redox processes (Wlostowski, 1993) and with protection of DNA from oxidative damage (Chubatsu and Meneghini, 1993) in cell proliferation.…”