title: Airway smooth muscle hypertrophy and hyperplasia in asthma.
abstract: BACKGROUND
  Increased thickness of the airway smooth muscle (ASM) layer in asthma may result from hyperplasia or hypertrophy of muscle cells or increased extracellular matrix (ECM).
  
  
  OBJECTIVE
  To relate ASM hypertrophy, ASM hyperplasia, and deposition of ECM to the severity and duration of asthma.
  
  
  METHODS
  Airways from control subjects (n = 51) and from cases of nonfatal (n = 49) and fatal (n = 55) asthma were examined postmortem. Mean ASM cell volume (V(C)), the number of ASM cells per length of airway (N(L)), and the volume fraction of extracellular matrix (f(ECM)) within the ASM layer were estimated. Comparisons between subject groups were made on the basis of general linear regression models.
  
  
  RESULTS
  Mean V(C) was increased in the large airways of cases of nonfatal asthma (P = 0.015) and fatal asthma (P < 0.001) compared with control subjects. N(L) was similar in nonfatal cases and control subjects but increased in large (P < 0.001), medium (P < 0.001), and small (P = 0.034) airways of cases of fatal asthma compared with control subjects and with nonfatal cases (large and medium airways, P ≤ 0.003). The f(ECM) was similar in cases of asthma and control subjects. Duration of asthma was associated with a small increase in N(L).
  
  
  CONCLUSIONS
  Hypertrophy of ASM cells occurs in the large airways in both nonfatal and fatal cases of asthma, but hyperplasia of ASM cells is present in the large and small airways in fatal asthma cases only. Both are associated with an absolute increase in ECM. Duration of asthma has little or no effect on ASM hypertrophy or hyperplasia or f(ECM).
authors.affiliation: Department of Pulmonary Physiology and Sleep Medicine/West Australian Sleep Disorders Research Institute, Level 5, G Block, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands, Western Australia 6009, Australia. Alan.James.SCGH@health.wa.gov.au
authors.forename: Alan L
authors.initials: AL
authors.lastname: James
authors.forename: John G
authors.initials: JG
authors.lastname: Elliot
authors.forename: Robyn L
authors.initials: RL
authors.lastname: Jones
authors.forename: Mark L
authors.initials: ML
authors.lastname: Carroll
authors.forename: Thais
authors.initials: T
authors.lastname: Mauad
authors.forename: Tony R
authors.initials: TR
authors.lastname: Bai
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Abramson
authors.forename: Karen O
authors.initials: KO
authors.lastname: McKay
authors.forename: Francis H
authors.initials: FH
authors.lastname: Green
mesh_terms: D000293:Adolescent; D000328:Adult; D056151:Airway Remodeling; D001249:Asthma / Q000401:mortality / Q000473:pathology*; D001980:Bronchi / Q000473:pathology*; D016022:Case-Control Studies; D005109:Extracellular Matrix / Q000473:pathology*; D005260:Female; D006801:Humans; D006965:Hyperplasia; D006984:Hypertrophy; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000473:pathology*; D012720:Severity of Illness Index; D055815:Young Adult