title: Bone loss in a new rodent model combining spinal cord injury and cast immobilization.
abstract: OBJECTIVE
  Characterize bone loss in our newly developed severe contusion spinal cord injury (SCI) plus hindlimb immobilization (IMM) model and determine the influence of muscle contractility on skeletal integrity after SCI.
  
  
  METHODS
  Female Sprague-Dawley rats were randomized to: (a) intact controls, (b) severe contusion SCI euthanized at Day 7 (SCI-7) or (c) Day 21 (SCI-21), (d) 14 days IMM-alone, (e) SCI+IMM, or (f) SCI+IMM plus 14 days body weight supported treadmill exercise (SCI+IMM+TM).
  
  
  RESULTS
  SCI-7 and SCI-21 exhibited a >20% reduction in cancellous volumetric bone mineral density (vBMD) in the hindlimbs (p⋜0.01), characterized by reductions in cancellous bone volume (cBV/TV%), trabecular number (Tb.N), and trabecular thickness. IMM-alone induced no observable bone loss. SCI+IMM exacerbated cancellous vBMD deficits with values being >45% below Controls (p⋜0.01) resulting from reduced cBV/TV% and Tb.N. SCI+IMM also produced the greatest cortical bone loss with distal femoral cortical area and cortical thickness being 14-28% below Controls (p⋜0.01) and bone strength being 37% below Controls (p⋜0.01). SCI+IMM+TM partially alleviated bone deficits, but values remained below Controls.
  
  
  CONCLUSIONS
  Residual and/or facilitated muscle contractility ameliorate bone decrements after severe SCI. Our novel SCI+IMM model represents a clinically-relevant means of assessing strategies to prevent SCI-induced skeletal deficits.
authors.affiliation: Research Service, Department of Veterans Affairs Medical Center, North Florida/South Georgia Veterans Health System, Gainesville, FL, United States, 32608.
authors.forename: J F
authors.initials: JF
authors.lastname: Yarrow
authors.forename: F
authors.initials: F
authors.lastname: Ye
authors.forename: A
authors.initials: A
authors.lastname: Balaez
authors.forename: J M
authors.initials: JM
authors.lastname: Mantione
authors.forename: D M
authors.initials: DM
authors.lastname: Otzel
authors.forename: C
authors.initials: C
authors.lastname: Chen
authors.forename: L A
authors.initials: LA
authors.lastname: Beggs
authors.forename: C
authors.initials: C
authors.lastname: Baligand
authors.forename: J E
authors.initials: JE
authors.lastname: Keener
authors.forename: W
authors.initials: W
authors.lastname: Lim
authors.forename: R S
authors.initials: RS
authors.lastname: Vohra
authors.forename: A
authors.initials: A
authors.lastname: Batra
authors.forename: S E
authors.initials: SE
authors.lastname: Borst
authors.forename: P K
authors.initials: PK
authors.lastname: Bose
authors.forename: F J
authors.initials: FJ
authors.lastname: Thompson
authors.forename: K
authors.initials: K
authors.lastname: Vandenborne
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D001862:Bone Resorption / Q000473:pathology*; D001842:Bone and Bones / Q000033:anatomy & histology; D002370:Casts, Surgical; D004195:Disease Models, Animal; D005260:Female; D019417:Hindlimb Suspension / Q000009:adverse effects*; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000473:pathology*