Abstract
Airway smooth muscle (ASM) is the major effector of excessive airway narrowing in asthma. Changes in some of the mechanical properties of ASM could contribute to excessive narrowing and have not been systematically studied in human ASM from nonasthmatic and asthmatic subjects.
Human ASM strips (eight asthmatic and six nonasthmatic) were studied at in situ length and force was normalised to maximal force induced by electric field stimulation (EFS). Measurements included: passive and active force versus length before and after length adaptation, the force–velocity relationship, maximal shortening and force recovery after length oscillation. Force was converted to stress by dividing by cross-sectional area of muscle.
The only functional differences were that the asthmatic tissue was stiffer at longer lengths (p<0.05) and oscillatory strain reduced isometric force in response to EFS by 19% as opposed to 36% in nonasthmatics (p<0.01).
The mechanical properties of human ASM from asthmatic and nonasthmatic subjects are comparable except for increased passive stiffness and attenuated decline in force generation after an oscillatory perturbation. These data may relate to reduced bronchodilation induced by a deep inspiration in asthmatic subjects.
- Airway hyperresponsiveness
- airway mechanics
- asthma
- force–velocity relationships
- length–tension relationships
- smooth muscle
Footnotes
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Support Statement
This work was supported by operating grants from Canadian Institutes of Health Research (CIHR) (MOP-13271, MOP-4725). L.Y.M. Chin is supported by an Alexander Graham Bell Graduate Scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC). Y. Bossé is supported by a fellowship from Fonds de la Recherche en Santé Québec (FRSQ) and a CIHR Strategic Training Initiative in Health Research-IMPACT fellowship. T.L. Hackett is supported by a Canadian Lung Association/CIHR/GSK, CIHR Strategic Training Initiative in Health Research-IMPACT and Michael Smith Foundation for Health Research Fellowships.
Statement of Interest
Statements of interest for T. L. Hackett and P.D. Paré can be found at www.erj.ersjournals.com/site/misc/statements.xhtml
- Received April 15, 2011.
- Accepted November 10, 2011.
- ©ERS 2012