Characterization of primary cilia in human airway smooth muscle cells.
BACKGROUND
Considerable evidence indicates a key role for primary cilia of mammalian cells in mechanochemical sensing. Dysfunctions of primary cilia have been linked to the pathogenesis of several human diseases. However, cilia-related research has been limited to a few cell and tissue types; to our knowledge, no literature exists on primary cilia in airway smooth muscle (ASM). The aim of this study was to characterize primary cilia in human ASM.


METHODS
Primary cilia of human bronchial smooth muscle cells (HBSMCs) were examined using immunofluorescence confocal microscopy, and scanning and transmission electron microscopy. HBSMC migration and injury repair were examined by scratch-wound and epidermal growth factor (EGF)-induced migration assays.


RESULTS
Cross-sectional images of normal human bronchi revealed that primary cilia of HBSMCs within each ASM bundle aggregated at the same horizontal level, forming a "cilium layer." Individual cilia of HBSMCs projected into extracellular matrix and exhibited varying degrees of deflection. Mechanochemical sensing molecules, polycystins, and alpha2-, alpha5-, and beta1-integrins were enriched in cilia, as was EGF receptor, known to activate jointly with integrins during cell migration. Migration assays demonstrated a ciliary contribution to HBSMC migration and wound repair.


CONCLUSIONS
The primary cilia of ASM cells exert a role in sensing and transducing extracellular mechanochemical signals and in ASM injury repair. Defects in ASM ciliary function could potentially affect airway wall maintenance and/or remodeling, possibly relating to the genesis of bronchiectasis in autosomal dominant polycystic kidney disease, a disease of ciliopathy.
Wu
Jun
J
Kidney Institute of the China People's Liberation Army, Changzheng Hospital, Second Military Medical University, Shanghai, People's Republic of China.
Du
Hui
H
Division of Nephrology and Hypertension, Mayo Clinic College of Medicine, Rochester, MN.
Wang
Xiangling
X
Division of Nephrology and Hypertension, Mayo Clinic College of Medicine, Rochester, MN.
Mei
Changlin
C
Kidney Institute of the China People's Liberation Army, Changzheng Hospital, Second Military Medical University, Shanghai, People's Republic of China.
Sieck
Gary C
GC
Department of Medicine, and the Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN.
Qian
Qi
Q
Division of Nephrology and Hypertension, Mayo Clinic College of Medicine, Rochester, MN; Department of Medicine, and the Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN. Electronic address: qian.qi@mayo.edu.