Temporal Modulation of TGF-β1 and β-Actin Gene Expression in Pig Skin and Muscular Fibrosis after Ionizing Radiation

Abstract

Although radiation-induced fibrosis has long been characterized by excess fibroblast proliferation and extracellular matrix deposition, the origin of cell activation in these complications of radiotherapy or radiation accidents is still controversial. The present work was designed to test the hypothesis that the abnormal production of TGF-beta 1 in irradiated tissues results in continuous signals for tissue repair and long-term cell activation. We examined gene expression of this growth factor in a well-characterized pig model of radiation-induced fibrosis, using Northern-blot and slot-blot hybridizations and indirect immunofluorescence. We found that the TGF-beta 1 mRNA level was increased 19-fold in the irradiated skin during the early erythematous phase, which started 3 weeks after irradiation. During the later phases of fibrosis, from 6 to 12 months after irradiation, the TGF-beta 1 gene was highly expressed in the repaired skin and the underlying muscular fibrotic tissue, with 10- and 8-fold maximal increases, respectively. In addition, we found that the beta-actin mRNA level was increased in the fibrotic tissue. Immunostaining for TGF-beta 1 revealed the presence of the protein in endothelial cells of capillaries, in myofibroblasts, and in the collagenous matrix of the fibrotic tissue. These results suggest that TGF-beta 1 may be one of the key cytokines involved in the cascade of events that leads to radiation-induced fibrosis, at both early and late stages.

Hypoxia-generated superoxide induces the development of the adhesion phenotype

“…There is a growing body of evidences that SOD could be a potential antifibrotic drug, as proved by clinical results on radiation-induced fibrosis [54,55] and its therapeutic effect could be related to a down-regulation of TGF-β1 expression and activity [27,56]. Superoxide dismutases exhibit potent anti-inflammatory properties [57], and all isoforms (SOD1, SOD2, and SOD3) induced 70% regression of a well-established fibrotic tissue and its replacement by regenerated normal tissue [54].…”

Therapeutic Potential of Umbilical Cord Mesenchymal Stem Cells for Inhibiting Myofibroblastic Differentiation of Irradiated Human Lung Fibroblasts

“…Radiation can stimulate lung fibroblasts to secrete cytokines, undergo hyperplasia, and differentiate into myofibroblasts (Martin et al 1993(Martin et al , 2000Rodemann and Bamberg 1995). Myofibroblasts, which show up-regulated expression of α-smooth muscle actin (α-SMA), promote the synthesis of additional collagens; this leads to excessive deposition and abnormal remodeling of the extracellular matrix, a hallmark of RILI (Rodemann and Bamberg 1995;Martin et al 2000;Hu et al 2006).…”

Current concepts in radiation enteritis and implications for future clinical trials

“…This early increase in TGF-␤1 mRNA also was observed after pig skin radiation, TGF-␤1 elevation was sustained for 6 -12 months postradiation. 51 Immunostaining showed the presence of TGF-␤1 in myofibroblasts, mononuclear inflammatory cells, and endothelial cells in the later phase. Biopsy samples from irradiated human skin performed 6 months to 20 years after radiation showed an increased level of mRNA for TGF-␤1, collagen Type I and Type III.…”

“…78 In another study with the same dose and frequency of IFN-␥, there also was a stabilization of visceral involvement. 79 A higher dose of IFN-␥ (150 mcg per day) induced a significant decrease in skin thickness compared with a lower dose (60 mcg per 17 Rat Intestines 0, 12 ISH Increased Wang et al 18 Rat Intestines 0, 12 CIA, IH Increased Hauer-Jensen et al 19 Rat Intestines 21 RTP, ISH Increased Zheng et al 20 Mouse Intestines 21 RTP, IH Inhibited by soluble TGF-␤ receptor Richter et al 23 Human Intestines NS IH Increased Bai et al 38 Rat Lungs 30 IH, ISH Increased Rube et al 39 Mouse Lungs 6, 12 IH, RTP Increased Rubin et al 43 Mouse Lungs 5 IH, ISH Increased Anscher et al 45 Human Lungs NS EIA Increased Randall and Coggle 50 Mouse Skin 50 PCR Increased Martin et al 51 Pig Skin 140 NBH, SBT, IF Increased Lefaix et al 55 Pig Skin 160 US, IH Inhibited by PTX and vit E Zhao et al 60 Rat Kidney 1-10 NBA Increased Robbins et al 61 Rat Kidney 10, 15, 20 IH Increased Zhao et al 62 Rat Kidney 1-10 WBA, LA Increased Datta et al 63 Rat Kidney 15 EIA Increased Seong et al 65 Rat Liver 25 IH Increased Geraci and Mariqno 66 Rat Liver 25 RH Increased Anscher et al 67 Rat Liver NS IH Increased TGF-␤: transforming growth factor beta; Gy: Gray; NS: not specified; IH: immunohistochemistry; RIS: radiation injury scoring; TBS: toluidine blue stain; ISH: in situ hybridization; CIA: computerized image analysis; RTP: reverse transcriptase polymerase; EIA: enzyme-linked immunosorbent assay; US: ultrasound; NBH: Northern blot hybridization; SBH: Southern blot hybridization; PCR: polymerase chain reaction; NBA: Northern blot analysis; WBA: Western blot analysis; LA: luciferase assay; RH: ribonucleic acid hybridization; PTX: pentoxifylline; vit E: vitamin E. day). 80 The beneficial effect of IFN-␥ on skin lesions also was reported in a randomized study: Mouth aperture and skin scores increased significantly in the treated group after 12 months of treatment with IFN-␥ (100 mcg per day).…”