title: Correlation of a simple direct measurement of muscle pO(2) to a clinical ischemia index and histology in a rat model of chronic severe hindlimb ischemia.
abstract: OBJECTIVE
  The lack of suitable experimental models of chronic severe limb ischemia and deficiencies in the available methods that allow for direct intermittent measurement of regional limb perfusion are obstacles to the evaluation of recently developed molecular strategies to reverse severe limb ischemia. Our aim was to develop a model of clinically relevant severe limb ischemia and correlate a simple direct measurement of muscle pO(2) to a clinical ischemia index, muscle mass, and capillary density.
  
  
  METHODS
  Severe hindlimb ischemia was induced in 44 adult rats with ligation of the left common iliac artery, the femoral artery, and their branches. The effect of ischemia on muscle pO(2) was measured in the left gastrocnemius with room air and with 100% oxygen at 3, 10, 24, and 40 days after ischemia was induced. Clinical ischemia index, muscle mass, cellular proliferation, and capillary density also were assessed.
  
  
  RESULTS
  The clinical ischemia index of the left limb was most severe at day 10, with evidence of pressure sores, a pale and dusky limb, and abnormal gait. With the rats breathing room air, muscle pO(2) was significantly lower in the left limbs than in the right limbs at days 3, 10, 24, and 40. After an oxygen challenge (100% O(2)), muscle pO(2) was significantly lower at 3, 10, and 40 days. At 3 days, the fraction of muscle mass per total body weight of the left tibialis anterior (TA) was significantly greater than the right TA as a result of edema and inflammation. By days 10, 24, and 40, the left gastrocnemius and TA masses were significantly less than the right as a result of muscle atrophy. Histopathology showed severe necrosis in the left gastrocnemius and TA on day 3. Inflammation was greatest by day 10. Necrotic muscle regenerated but remained atrophic at 40 days. The TA was slower to recover than the gastrocnemius. Capillary densities and capillary-to-muscle fiber ratios were greater in the ischemic limb than in the normal limb at day 24. Cellular proliferation as determined with bromodeoxyuridine labeling reagent staining was maximal in the ischemic limb at day 3.
  
  
  CONCLUSIONS
  We have developed a rat model of chronic severe hindlimb ischemia with persistent ischemia as shown with a simple direct measurement of muscle pO(2) for up to 40 days. This model of severe hindlimb ischemia may be applicable for future studies of molecular strategies to treat severe limb ischemia in humans.
authors.affiliation: Division of Vascular Surgery, Department of Surgery, University of California-San Francisco, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Paek
authors.forename: David S
authors.initials: DS
authors.lastname: Chang
authors.forename: Lucy S
authors.initials: LS
authors.lastname: Brevetti
authors.forename: Mark D
authors.initials: MD
authors.lastname: Rollins
authors.forename: Sandra
authors.initials: S
authors.lastname: Brady
authors.forename: Philip C
authors.initials: PC
authors.lastname: Ursell
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Hunt
authors.forename: Rajabrata
authors.initials: R
authors.lastname: Sarkar
authors.forename: Louis M
authors.initials: LM
authors.lastname: Messina
mesh_terms: D000818:Animals; D002196:Capillaries / Q000503:physiopathology; D002908:Chronic Disease; D004195:Disease Models, Animal; D005121:Extremities / Q000098:blood supply; D006614:Hindlimb / Q000098:blood supply*; D007511:Ischemia / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D010100:Oxygen / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012720:Severity of Illness Index; D013223:Statistics as Topic
chemical_list: D010100:Oxygen