title: Targeted stimulation of retinoic acid receptor-γ mitigates the formation of heterotopic ossification in an established blast-related traumatic injury model.
abstract: Heterotopic ossification (HO) involves formation of endochondral bone at non-skeletal sites, is prevalent in severely wounded service members, and causes significant complications and delayed rehabilitation. As common prophylactic treatments such as anti-inflammatory drugs and irradiation cannot be used after multi-system combat trauma, there is an urgent need for new remedies. Previously, we showed that the retinoic acid receptor γ agonist Palovarotene inhibited subcutaneous and intramuscular HO in mice, but those models do not mimic complex combat injury. Thus, we tested Palovarotene in our validated rat trauma-induced HO model that involves blast-related limb injury, femoral fracture, quadriceps crush injury, amputation and infection with methicillin-resistant Staphylococcus aureus from combat wound infections. Palovarotene was given orally for 14days at 1mg/kg/day starting on post-operative day (POD) 1 or POD-5, and HO amount, wound dehiscence and related processes were monitored for up to 84days post injury. Compared to vehicle-control animals, Palovarotene significantly decreased HO by 50 to 60% regardless of when the treatment started and if infection was present. Histological analyses showed that Palovarotene reduced ectopic chondrogenesis, osteogenesis and angiogenesis forming at the injury site over time, while fibrotic tissue was often present in place of ectopic bone. Custom gene array data verified that while expression of key chondrogenic and osteogenic genes was decreased within soft tissues of residual limb in Palovarotene-treated rats, expression of cartilage catabolic genes was increased, including matrix metalloproteinase-9. Importantly, Palovarotene seemed to exert moderate inhibitory effects on wound healing, raising potential safety concerns related to dosing and timing. Our data show for the first time that Palovarotene significantly inhibits HO triggered by blast injury and associated complications, strongly indicating that it may prevent HO in patients at high risk such as those sustaining combat injuries and other forms of blast trauma.
authors.affiliation: Regenerative Medicine Department, Naval Medical Research Center, Silver Spring, MD, United States; USU-Walter Reed Surgery, Walter Reed National Military Medical Center, Bethesda, MD, United States.
authors.forename: Gabriel J
authors.initials: GJ
authors.lastname: Pavey
authors.affiliation: Regenerative Medicine Department, Naval Medical Research Center, Silver Spring, MD, United States.
authors.forename: Ammar T
authors.initials: AT
authors.lastname: Qureshi
authors.affiliation: Regenerative Medicine Department, Naval Medical Research Center, Silver Spring, MD, United States.
authors.forename: Allison M
authors.initials: AM
authors.lastname: Tomasino
authors.affiliation: Department of Pathology, Naval Medical Research Center, Silver Spring, MD, United States.
authors.forename: Cary L
authors.initials: CL
authors.lastname: Honnold
authors.affiliation: Department of Wound Infections, Naval Medical Research Center, Silver Spring, MD, United States.
authors.forename: Danett K
authors.initials: DK
authors.lastname: Bishop
authors.affiliation: Department of Surgery, University of Michigan Health System, Ann Arbor, MI, United States.
authors.forename: Shailesh
authors.initials: S
authors.lastname: Agarwal
authors.affiliation: Department of Surgery, University of Michigan Health System, Ann Arbor, MI, United States.
authors.forename: Shawn
authors.initials: S
authors.lastname: Loder
authors.affiliation: Department of Surgery, University of Michigan Health System, Ann Arbor, MI, United States.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Levi
authors.affiliation: Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, PA, United States.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Pacifici
authors.affiliation: Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, PA, United States.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iwamoto
authors.affiliation: Regenerative Medicine Department, Naval Medical Research Center, Silver Spring, MD, United States; USU-Walter Reed Surgery, Walter Reed National Military Medical Center, Bethesda, MD, United States.
authors.forename: Benjamin K
authors.initials: BK
authors.lastname: Potter
authors.affiliation: Regenerative Medicine Department, Naval Medical Research Center, Silver Spring, MD, United States; USU-Walter Reed Surgery, Walter Reed National Military Medical Center, Bethesda, MD, United States. Electronic address: thomas.a.davis196.ctr@mail.mil.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Davis
authors.affiliation: Regenerative Medicine Department, Naval Medical Research Center, Silver Spring, MD, United States; USU-Walter Reed Surgery, Walter Reed National Military Medical Center, Bethesda, MD, United States.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Forsberg
mesh_terms: D000818:Animals; D001753:Blast Injuries / Q000150:complications / Q000188:drug therapy* / Q000473:pathology; D020219:Chondrogenesis / Q000187:drug effects / Q000235:genetics; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D009999:Ossification, Heterotopic / Q000188:drug therapy* / Q000473:pathology; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D011720:Pyrazoles / Q000494:pharmacology / Q000627:therapeutic use; D017207:Rats, Sprague-Dawley; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D013267:Stilbenes / Q000494:pharmacology / Q000627:therapeutic use; D014945:Wound Healing / Q000187:drug effects; D014947:Wounds and Injuries / Q000150:complications / Q000188:drug therapy* / Q000473:pathology; D000097768:Retinoic Acid Receptor gamma
chemical_list: D011720:Pyrazoles; D018168:Receptors, Retinoic Acid; D013267:Stilbenes; D000097768:Retinoic Acid Receptor gamma; C546535:Palovarotene
keywords: Animal model; Bioburden; Blast overpressure exposure; Endochondral ossification; Heterotopic ossification; Prophylaxis; Retinoic acid receptor-γ agonist; Traumatic extremity injury