Sylvie Delanian

TGF-β1 and radiation fibrosis: a master switch and a specific therapeutic target?

Radiation fibrosis is a frequent sequel of therapeutic or accidental radiation overexposure in normal human tissues. One of the main fundamental problems yet unsolved in fibrotic tissues is the origin of the chronic activation of myofibroblasts within these tissues. It has been postulated that this chronic activation results from a continuous production of activating factors. In this context, fibrosis could be defined as a wound where continuous signals for tissue repair are emitted. Cytokines and growth factors probably play a central role in this process. Among them, transforming growth factor-beta1 (TGF-beta1) is considered as a master switch for the fibrotic program. This review discusses recent evidence on the critical role played by TGF-beta in the initiation, development, and persistence of radiation fibrosis. It summarizes the results concerning this factor after irradiation of various tissues and cells, with an emphasis on superficial fibrosis, including skin and subcutaneous tissues. Finally, recent data concerning the treatment of established fibrotic disorders of various etiology are presented, as well as the possible mechanisms involved in fibrosis regression, which show that the TGF-beta pathway may constitute a specific target for antifibrotic agents.

Kinetics of Response to Long-Term Treatment Combining Pentoxifylline and Tocopherol in Patients With Superficial Radiation-Induced Fibrosis

PURPOSE Significant regression of radiation (RT) -induced fibrosis (RIF) has been achieved after treatment combining pentoxifylline (PTX) and alpha-tocopherol (vitE). In this study, we focus on the maximum response, how long it takes to achieve response, and changes after treatment discontinuation. PATIENTS AND METHODS Measurable superficial RIF was assessed in patients treated by RT for breast cancer in a long-treatment (24 to 48 months) PTX-vitE (LPE) group of 37 patients (47 RIFs) and in a short-treatment (6 to 12 months) PTX-vitE (SPE) group of seven patients (eight RIFs). Between April 1995 and April 2000, women were treated with a daily combination of PTX (800 mg) and VitE (1,000 IU). RESULTS Combined PTX-vitE was continuously effective and resulted in exponential RIF surface area regression (-46% for LPE and -68% for SPE at 6 months, -58% for LPE and -69% for SPE at 12 months, -63% for LPE and -62% for SPE at 18 months, and -68% for LPE at 24 and 36 months). The mean estimated maximal treatment effect was 68% RIF surface area regression. The mean time to this effect was 24 months and was shorter (16 months) in more recent RIF (< 6 years since RT) than in older RIF (28 months; P = .0003). Symptom severity (Subjective Objective Medical Management and Analytic Evaluation score) was halved in both groups. After treatment discontinuation, mean RIF surface area at 1 year had increased by +40% in the SPE group (rebound) and +8.5% in the LPE group. CONCLUSION Under combined PTX-vitE treatment, RIF regression was exponential, with a two-thirds maximum response after a mean of 2 years. There was a risk of a rebound effect if treatment was too short. Long treatment (>/= 3 years) is recommended in patients with severe RIF.

Striking regression of subcutaneous fibrosis induced by high doses of gamma rays using a combination of pentoxifylline and α-tocopherol: an experimental study

PURPOSE To establish a successful treatment of subcutaneous fibrosis developing after high doses of gamma rays, suitable for use in clinical practice. METHODS AND MATERIALS We used an animal model of acute localized gamma irradiation simulating accidental overexposure in humans. Three groups of 5 Large White pigs were irradiated using a collimated 192Ir source to deliver a single dose of 160 Gy onto the skin surface (100%) of the outer side of the thigh. A well-defined block of necrosis developed within a few weeks which had healed after 26 weeks to leave a block of subcutaneous fibrosis involving skin and skeletal muscle. One experimental group of 5 pigs was dosed orally for 26 weeks starting 26 weeks after irradiation with 1600 mg/120 kg body weight of pentoxifylline (PTX) included in the reconstituted food during its fabrication, and another group of 5 was dosed orally for the same period with a daily dose of 1600 mg/120 kg body weight of PTX combined with 2000 IU/120 kg body weight of alpha-tocopherol. Five irradiated control pigs were given normal food only. Animals were assessed for changes in the density of the palpated fibrotic block and in the dimensions of the projected cutaneous surface. Depth of scar tissue was determined by ultrasound. Physical and sonographic findings were confirmed by autopsy 26 weeks after treatment started. The density, length, width, and depth of the block of fibrotic scar tissue, and the areas and volume of its projected cutaneous surface, were compared before treatment, 6 and 13 weeks thereafter, and at 26 weeks. RESULTS The experimental animals exhibited no change in behavior and no abnormal clinical or anatomic signs. No modifications were observed in the block of fibrotic scar tissue of pigs dosed with PTX alone. However, significant softening and shrinking of this block were noted in the pigs dosed with PTX + alpha-tocopherol 13 weeks after treatment started and at autopsy, when mean regression was approximately 30% for length, approximately 50% for width and depth, and approximately 70% for area and volume. Histologic examination showed completely normal muscle and subcutaneous tissue surrounding the residual scar tissue. The 50% decrease in the linear dimensions of the scar tissue, were comparable to the results obtained in our previous clinical studies, and were highly significant compared to the clinical and autopsy results for the controls. Histologic examination of the residual scar tissue revealed tissue which was more homogenous and less cellular and inflammatory than in control and PTX-dosed pigs. The tissular and cellular immunolocalization of tumor necrosis factor alpha (TNFalpha) was similar in the residual fibrotic tissues of all three groups of pigs, whereas the immunostaining of transforming growth factor beta-1(TGFbeta-1) diminished much more in the residual fibrotic scar tissue of the PTX + alpha-tocopherol-dosed pigs than in the two other groups. CONCLUSIONS The present results showed a striking regression of the subcutaneous fibrotic scar tissue that develops as a consequence of high doses of gamma rays.

MAJOR HEALING OF REFRACTORY MANDIBLE OSTEORADIONECROSIS AFTER TREATMENT COMBINING PENTOXIFYLLINE AND TOCOPHEROL: A PHASE II TRIAL

Osteoradionecrosis (ORN) is a nonhealing wound of the bone that is difficult to manage. Is a treatment combining pentoxifylline (PTX) and tocopherol (vitamin E) boosted by clodronate effective in reversing this fibronecrotic process?

Antifibrotic action of Cu/Zn SOD is mediated by TGF-β1 repression and phenotypic reversion of myofibroblasts

Skin fibrosis is characterized by the proliferation and accumulation of activated fibroblasts called myofibroblasts. They exhibit specific cytoskeletal differentiation, overexpress the fibrogenic cytokine TGF-beta1, synthesize excess extracellular matrix compounds and exhibit a depleted antioxidant metabolism. Recently, SOD was successfully used as an antifibrotic agent in vivo, thus challenging the postulate of established fibrosis irreversibility. We postulated that myofibroblasts could be a direct target for this therapeutic effect. To test this hypothesis, we used three-dimensional co-culture models of skin, in which specific phenotypes of normal fibroblasts versus myofibroblasts are retained. These 3-D models were treated with liposomal and carrier-free Cu/Zn SOD, and examined for their effects on cell number, cell death, and phenotypic differentiation. The results show that SOD did not induce myofibroblast cell death, whereas it significantly reduced TGF-beta1 expression, thus demonstrating that SOD might be proposed as a potent antagonist of this major fibrogenic growth factor. We also found that SOD significantly lowered the levels of the myofibroblast marker alpha-sm actin, of beta-actin, and of the extracellular matrix components alpha1(I) collagen and tenascin-C. In conclusion, our results suggest that SOD antifibrotic action occurred in vitro through the reversion of myofibroblasts into normal fibroblasts.

Abnormal phenotype of cultured fibroblasts in human skin with chronic radiotherapy damage

PURPOSE The pathophysiological aspects of radiation-induced fibrosis (RIF) have not been well characterized. We therefore cultured human fibroblasts from samples of skin with RIF to investigate the long-term effects of therapeutic irradiation. MATERIALS AND METHODS Biopsies of normal and RIF skin were obtained from patients previously irradiated for cancer, without recurrence. Cells were extracted from dermis samples by the outgrowth technique, seeded as monolayers and cultured at confluence. Enzyme activities and proteins were assayed, RNA was isolated and Northern blot analysis was performed on surviving cells between passages 2 and 5. RESULTS RIF cell cultures displayed heterogeneous fibroblasts populations. The initial outgrowth consisted of one-third small cells that floated rapidly, one-third spindle-shaped cells migrating far from the explant to form islets and one-third large pleiomorphic cells. In subsequent subcultures, surviving cells exhibited either myofibroblastic characteristics with a normal proliferative capacity or senescent morphology with a reduced proliferative capacity. These RIF cells had a brief finite lifespan, with dramatically reduced growth rate during their initial outgrowth and the following passages. Study of the antioxidant metabolism showed that Mn superoxide dismutase and catalase activities were significantly weaker in surviving RIF cells than healthy fibroblasts. These exhausted RIF cells exhibited no overexpression of transforming growth factor beta or tissue inhibitor of metalloproteinase. CONCLUSION Irradiation may lead to apparently contradictory effects such as fibrosis and necrosis in clinical practice. In cell culture, we observed two main cellular phenotypes which may be related to both processes, i.e. myofibroblast-like cells and fibrocyte-like cells. These two phenotypes may represent two steps in the differentiation induced as a long-term effect of therapeutic irradiation of the skin. Cell culture probably accelerates the induction of the terminal differentiation in RIF fibroblasts.

Cu/Zn superoxide dismutase modulates phenotypic changes in cultured fibroblasts from human skin with chronic radiotherapy damage.

PURPOSE As we previously observed that bovine liposomal Cu/Zn SOD (LipSOD) reduces cutaneous radiation-induced fibrosis (RIF) in human therapeutic assays the mechanisms involved were investigated here by an in vitro study of the LipSOD effects on cellular antioxidant metabolism and regulation of matrix degradation. METHODS Primary cultures of human fibroblasts harvested from normal or RIF skin were treated with various doses of LipSOD. Catalase, Cu/Zn and Mn SOD endogenous cell enzyme activities and protein amounts were assayed by polyacrylamide gel electrophoresis and western blotting. Gene expressions of tissue inhibitor of metalloproteinases (TIMP) and TGF-beta1 was investigated by northern blot analysis. RESULTS A deficiency of endogenous Mn SOD, considered to favour cell proliferation, was observed in cultured RIF cell. The present study showed that bovine Cu/Zn SOD entered the cells. Exposure to LipSOD (a) enhanced endogenous Mn SOD activity and protein level, without changes of endogenous Cu/Zn SOD and catalase, and (b) significantly reduced TIMP and TGF-beta1 gene expression, in RIF cells. No changes in these parameters were noted in treated control skin fibroblasts. CONCLUSION Modulation of RIF skin fibroblasts by LipSOD seems effective via indirect endogenous Mn SOD activation, which might explain the cell phenotype reversion observed. TIMP reduction accounts for the elimination of collagenase activity inhibition and the subsequent digestion of excess extracellular matrix deposition, as well as RIF reversibility in vivo. The reduction of TGF-beta1 expression might explain the breaking of maintaining fibrotic cell activation connected with this growth factor.

Radiation-induced enteropathy: Molecular basis of pentoxifylline–vitamin E anti-fibrotic effect involved TGF-β1 cascade inhibition

BACKGROUND Radiation-induced fibrosis is a serious late complication of radiotherapy. Pentoxifylline-vitamin E has proven effective and safe in clinical trials in the treatment of fibrosis, while the molecular mechanism of its activity is yet unexplored. METHODS Ten patients suffering from radiation-induced enteropathy were treated with pentoxifylline-vitamin E combination with SOMA score as the primary endpoint. In parallel, primary smooth muscle cells isolated from intestinal samples isolated from humans with radiation enteropathy were incubated with pentoxifylline, trolox (vit. E hydrophilic analogous) or their combination. Activation of the TGF-β1/Smad and Rho/ROCK pathways was subsequently investigated using Q-RT-PCR, gene reporter, Western-blot, ELISA and immunohistochemistry. RESULTS Pentoxifylline-vitamin E combination induces regression of symptoms (SOMA) by -41% and -80% at 6 and 18months. In vitro, pentoxifylline and trolox synergize to inhibit TGF-β1 protein and mRNA expression. This inhibitory action is mediated at the transcriptional level and leads to subsequent inhibition of TGF-β1/Smad targets (Col Iα1, FN1, PAI-1, CTGF), while it has no effect on the Rho/ROCK pathway. CONCLUSIONS The anti-fibrotic effect of combined pentoxifylline-vitamin E is at least in part mediated by inhibition of the TGF-β1 cascade. It strengthens previous clinical data showing pentoxifylline-vitamin E synergy and supports its use as a first-line treatment of radiation-induced fibrosis.

Radiation Therapy for Hypersalivation: A Prospective Study in 50 Amyotrophic Lateral Sclerosis Patients

PURPOSE This study aimed to evaluate the efficiency and the tolerance of radiation therapy (RT) on salivary glands in a large series of amyotrophic lateral sclerosis (ALS) patients with hypersalivation. METHODS AND MATERIALS Fifty ALS patients that had medically failure pretreatment were included in this prospective study. RT was delivered through a conventional linear accelerator with 6-MV photons and 2 opposed beams fields including both submandibular glands and two-thirds of both parotid glands. Total RT dose was 10 Gy in 2 fractions (n=30) or 20 Gy in 4 fractions (n=20). RT efficacy was assessed with the 9-grade Sialorrhea Scoring Scale (SSS), recently prospectively validated as the most effective and sensitive tool to measure sialorrhea in ALS patients. RESULTS At the end of RT, all patients had improved: 46 had a complete response (92% CR, SSS 1-3) and 4 had a partial response (8% PR, SSS 4-5). A significant lasting salivary reduction was observed 6 months after RT completion: there was 71% CR and 26% PR, and there was a significant SSS reduction versus baseline (P<10(-6)). There was no grade 3 to 4 toxicity, and most side effects (34%) occurred during RT. Nine patients (18%) underwent a second salivary gland RT course, with a 3-months mean delay from the first RT, resulting in a SSS decrease (-77%). Both RT dose regimens induced a significant SSS decrease with no significant toxicity. There were, however, more patients with CR/PR in the 20-Gy protocol (P=.02), and 8 of 9 patients (89%) receiving a second RT course had previously been treated within the 10-Gy protocol. CONCLUSION Radiation therapy of 20 Gy in 4 fractions is an efficient and safe treatment for ALS patients with sialorrhea. A shorter RT course (10 Gy in 2 fractions) may be proposed in patients in poor medical condition.

MiR-210: A potential therapeutic target against radiation-induced enteropathy

A previously undescribed and robust miR210 overexpression is shown in intestinal samples obtained from patients with radiation enteropathy and fibrotic cultured cells. In addition, miR-210 overexpression is repressed by antifibrotic treatment combining pentoxifylline and α-tocopherol.