title: Angiotensin-(1-7) Attenuates Skeletal Muscle Fibrosis and Stiffening in a Mouse Model of Extremity Sarcoma Radiation Therapy.
abstract: BACKGROUND
  Radiation-induced fibrosis (RIF) of musculoskeletal tissue is a common complication of radiation therapy for extremity soft-tissue sarcoma, with no standardized strategy for prevention and treatment. Angiotensin-(1-7) (Ang-[1-7]), a well-tolerated endogenous heptapeptide hormone with antitumor and antifibrotic properties, was tested as a radioprotectant for RIF and stiffening of irradiated muscles.
  
  
  METHODS
  Male CD-1 mice were randomized to one of three treatment groups: control, simulated sarcoma radiation therapy to the gastrocnemius and soleus muscles, or radiation therapy along with continuous Ang-(1-7) delivery initiated three days before radiation therapy. The biologically equivalent dose of radiation (∼100.3 Gy) absorbed by normal musculature during the course of radiation therapy for extremity sarcoma was delivered by means of four dose fractions of 7.3 Gy over two weeks. Fibrosis (n = 5 per group) and mechanical properties (n = 4 to 6 per group) of the muscles were measured at six weeks and four months after radiation therapy, and the intramuscular concentration of the profibrotic cytokines transforming growth factor-beta (TGF-β) and connective tissue growth factor (CTGF) (n = 8 to 10 per group) were measured at six weeks.
  
  
  RESULTS
  Interstitial (p < 0.01) and perivascular (p < 0.05) fibrosis increased significantly in the muscles treated with radiation therapy alone versus the nonirradiated controls at both six weeks (interstitial, +89%; perivascular, +112%) and four months (interstitial, +154%; perivascular, +88%). The muscles treated with radiation alone also exhibited increased tension (p < 0.01) versus nonirradiated controls at both six weeks (+779%) and four months (+1761%) when placed under 5% strain, and at four months (+1390%; p < 0.001) under 10% strain. At four months, muscle stiffness had increased in the mice treated with radiation therapy alone (+90%; p = 0.002) compared with nonirradiated controls. TGF-β production was also greater in this group at six weeks (+37%; p = 0.06) versus control. Ang-(1-7) administration prevented RIF and stiffening, with no differences observed for any other outcome between those receiving radiation therapy with Ang-(1-7) and the nonirradiated controls. Likewise, Ang-(1-7) mitigated the increase in TGF-β and CTGF concentration from radiation therapy.
  
  
  CONCLUSIONS
  Ang-(1-7) attenuated RIF, stiffening, and production of profibrotic cytokines that were elevated in mouse skeletal muscles after simulated radiation therapy for extremity sarcoma.
  
  
  CONCLUSIONS
  Ang-(1-7) may serve as a potential therapy for the prevention of RIF in patients who require radiation therapy as adjuvant treatment for soft-tissue sarcoma.
authors.affiliation: Department of Radiation Oncology, Wake Forest School of Medicine, Winston-Salem, North Carolina Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, North Carolina Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston-Salem, North Carolina Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, North Carolina jwilley@wakehealth.edu.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Willey
authors.affiliation: Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Bracey
authors.affiliation: Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston-Salem, North Carolina Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Patricia E
authors.initials: PE
authors.lastname: Gallagher
authors.affiliation: Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston-Salem, North Carolina Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: E Ann
authors.initials: EA
authors.lastname: Tallant
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Walter F
authors.initials: WF
authors.lastname: Wiggins
authors.affiliation: Tensive Controls, MU Life Sciences Business Incubator, Columbia, Missouri.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Callahan
authors.affiliation: Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Smith
authors.affiliation: Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, North Carolina Hypertension and Vascular Research Center, Wake Forest School of Medicine, Winston-Salem, North Carolina Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Emory
mesh_terms: D000704:Analysis of Variance; D000803:Angiotensin I / Q000008:administration & dosage*; D000818:Animals; D001707:Biopsy, Needle; D004195:Disease Models, Animal; D005355:Fibrosis / Q000209:etiology / Q000517:prevention & control; D006614:Hindlimb; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D019042:Muscle Neoplasms / Q000473:pathology / Q000628:therapy; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000473:pathology / Q000528:radiation effects*; D010446:Peptide Fragments / Q000008:administration & dosage*; D011897:Random Allocation; D012016:Reference Values; D012513:Sarcoma, Experimental / Q000473:pathology / Q000628:therapy*; D012680:Sensitivity and Specificity; D013035:Spasm / Q000473:pathology / Q000517:prevention & control*
chemical_list: D010446:Peptide Fragments; D000803:Angiotensin I; C118790:angiotensin I (1-7)