Morphological and functional impairment in the gut in a partial body irradiation minipig model of GI-ARS

Abstract

Purpose: Göttingen minipig (G-MP) displays classic gastrointestinal acute radiation syndrome (GI-ARS) following total body irradiation (TBI) at GI doses which are lethal by 10–14 days. In collaboration with BARDA, we are developing a hemi-body/partial body irradiation (PBI) model by exposing only the abdomen and lower extremities to study GI structure/function impairment, natural history of injury and recovery, as well as correlative biomarkers out to 30 days.

Materials and methods: Twenty-four G-MP were exposed to either 12 or 16 Gy (LINAC Elekta); head, forelimbs, and thorax were outside the irradiation field, sparing ∼50% of the bone marrow. Animals were followed for 30 days with euthanasia scheduled at pre-set intervals to study the time course of GI injury and recovery. Hematological profiles, clinical symptoms, gross- and histo-pathology including markers of proliferation and apoptosis in the small intestines, gut function parameters (food tolerance, digestion, absorption, citrulline production), and levels of two biomarkers, CRP and IGF-1, were evaluated.

Results: PBI at 16 Gy yielded higher lethality than 12 Gy. Unlike TBI, PBI did not cause severe pancytopenia or external hemorrhage, as expected, and allowed to focus the injury on GI organs while sparing the radiation sensitive heart and lung. Compromised animals showed inactivity, anorexia, vomiting, diarrhea, and weight loss. Histology revealed that in 12 Gy irradiated animals, lesions recovered overtime. In 16 Gy irradiated animals, lesions were more pronounced and persistent. BrdU and Ki67 labelling demonstrated dose-dependent loss of crypts and subsequent mucosal ulceration which recovered over time. Minimal apoptosis was observed at both doses. Reductions in food tolerance, digestion, absorption, and citrulline production were time and dose-dependent. Loss of citrulline reached a nadir between 6-12 days and then recovered partially. CRP and IGF-1 were upregulated following PBI at GI doses.

Conclusions: This lower hemi-body irradiation model allowed for extended survival at GI-specific ARS doses and development of a well-controlled GI syndrome with minimal hematopoietic injury or confounding mortality from cardiopulmonary damage. A dose-dependent impairment in the intestinal structure resulted in overall decreased gut functionality followed by a partial recovery. However, while the structure appeared to be recovered, not all functionality was attained. PBI induced systemic inflammation and altered the IGF-1 hormone indicating that these can be used as biomarkers in the minipig even under partial body conditions. This PBI model aligns with other minipig models under BARDA’s large animal consortium to test medical countermeasure efficacy against a less complex GI-specific ARS injury.

Keywords:

• Acute radiation syndrome
• gastrointestinal
• Göttingen minipig
• partial body irradiation
• digestive system functions

Acknowledgements

We are thankful to Catherine Booth, Gregory Tudor, and Julie Tudor at Epistem Ltd, Manchester, UK and Dr. Jerrold Ward at Histoserv Inc, Germantown, MD for their invaluable contribution in terms of histological data. Special thanks are due to AFRRI’s health physics department, veterinary science department, and animal care staff for their dedication to the project and superb animal care.

Disclosure statement

The authors report no conflicts of interest.

Disclaimer

The views expressed in this manuscript are those of the author(s) and do not reflect the official policy or position of AFRRI, the Uniformed Services University of Health Sciences, BARDA, the Department of Health and Human Services or the Department of Defense.

Additional information

Funding

This project has been funded in whole or in part with Federal funds from the Biomedical Advanced Research and Development Authority, Office of the Secretary for Preparedness and Response, Department of Health and Human Services, under interagency agreement #750114PR970036.

Notes on contributors

Amandeep Kaur

Amandeep Kaur is a clinical veterinarian at Armed Forces Radiobiology Research Institute (AFRRI) with the Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD. She completed her PhD from Purdue University and has published works in the field of radiation biology, gut microbiota, and dietary fiber.

Gabriëlla A.M. ten Have

Gabriëlla ten Have is a research assistant professor within the Center for Translational Research in Aging & Longevity (CTRAL) at Texas A&M University. She has over 25 years of expertise in nutrition, metabolism, and pathophysiological studies involving the use of stable isotope approaches and methodologies in small and large animals.

Bernadette Hritzo

Bernadette Hritzo is a laboratory technician for the Henry M. Jackson Foundation for the Advancement of Military Medicine working in the Moroni Laboratory at AFRRI in Bethesda, MD. Her current research interest is radiation biology.

Nicolaas E.P. Deutz

Nicolaas Deutz is an endowed professor and the director and founder of CTRAL at Texas A&M University. He has more 30 years of experience in the field of clinical nutrition and metabolism with over 300 publications and several patents. He is the Editor-in-Chief of the main journal “Clinical Nutrition”.

Cara Olsen

Cara Olsen is an Associate Professor in the Biostatistics Consulting Center at the Uniformed Services University of the Health Sciences. In addition to statistical consulting, she teaches statistics to medical students and graduate students and directs the department's doctoral programs.

Maria Moroni

Maria Moroni is a research biologist for the Radiation Countermeasure Program at AFRRI since 2008. She has funding from several agencies including the NIH and BARDA. She is the author of multiple journal articles and book chapters in the field of radiation biology and animal model development for countermeasure testing.