Gastroenterology

Gastroenterology

Volume 119, Issue 5, November 2000, Pages 1286-1296
Gastroenterology

Alimentary Tract
Recombinant soluble transforming growth factor β type II receptor ameliorates radiation enteropathy in mice,☆☆

https://doi.org/10.1053/gast.2000.19282Get rights and content

Abstract

Background & Aims: Transforming growth factor (TGF)-β has been implicated in many fibrotic conditions. However, its mechanistic role in radiation toxicity is equivocal despite compelling correlative evidence. This study assessed whether in vivo administration of a soluble TGF-β type II receptor (TβR-II) protein ameliorates intestinal radiation injury (radiation enteropathy). Methods: A recombinant fusion protein, consisting of the extracellular portion of mouse TβR-II and the Fc portion of mouse immunoglobulin (Ig) G, was produced. A 5-cm segment of mouse ileum was exposed to 19 Gy x-radiation. TβR-II:Fc fusion protein (1 mg/kg every other day) or mouse IgG was administered from 2 days before to 6 weeks after irradiation. Radiation injury was assessed at 6 weeks using quantitative histology, morphometry, and immunohistochemistry. Collagen was measured colorimetrically, and TGF-β1 messenger RNA was assessed with fluorogenic probe reverse-transcription polymerase chain reaction. Results: Compared with IgG controls, TβR-II:Fc–treated mice exhibited less structural injury, preservation of mucosal surface area, and less intestinal wall fibrosis. Intestinal TGF-β1 messenger RNA increased in TβR-II:Fc–treated mice, whereas TGF-β immunoreactivity decreased. TβR-II:Fc treatment increased crypt cell proliferation but otherwise did not affect unirradiated intestine. Conclusions: Long-term modulation of TGF-β with a TβR-II:Fc fusion protein is feasible and ameliorates radiation enteropathy. These data confirm the putative role of TGF-β in intestinal radiation fibrosis.

GASTROENTEROLOGY 2000;119:1286-1296

Section snippets

Production of soluble TβR-II:Fc fusion protein

The extracellular domain of the murine TβR-II was amplified from a murine lung complementary DNA library (Clontech, Palo Alto, CA) by polymerase chain reaction (PCR), and engineered to contain a 5' Not1 and a 3' Sal1 restriction site. The Fc region of murine immunoglobulin (Ig) G2a was amplified by PCR from a murine hybridoma and engineered to contain a 5' Sal1 restriction site and a 3' Not1 restriction site. The receptor and Fc fragments were purified, digested with the appropriate restriction

Results

Acute radiation-induced complications were similar in TβR-II:Fc–treated mice and IgG-treated controls. As expected, approximately 50% of the mice (11 in the TβR-II:Fc group, 14 in the IgG group) developed symptoms of severe toxicity and were killed before the scheduled observation time of 42 days. Animals that survived until the scheduled 6-week observation time point (10 TβR-II:Fc–treated and 8 IgG-treated) appeared normal and in no distress. Only sections from these animals were used to

Discussion

The risk of normal tissue injury limits the radiation dose that can be safely delivered to a tumor, and thereby its curability. Whereas acute normal tissue toxicity is generally a result of death of rapidly proliferating cells, delayed toxicity in many organs is characterized by progressive fibrosis and vascular sclerosis. Chronic intestinal radiation injury is a debilitating disorder, affects the quality of life in a large cohort of cancer survivors, and is an important obstacle to

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    Address requests for reprints to: Martin Hauer-Jensen, M.D., Ph.D., Arkansas Cancer Research Center, 4301 West Markham, Slot 725, Little Rock, Arkansas 72205. e-mail: [email protected]; fax: (501) 686-7861.

    ☆☆

    Supported by grant CA71382 from the National Institutes of Health.

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