Mucociliary clearance: pathophysiological aspects

Abstract

SummaryMucociliary clearance has long been known to be a significant innate defence mechanism against inhaled microbes and irritants. Important knowledge has been gathered regarding the anatomy and physiology of this system, and in recent years, extensive studies of the pathophysiology related to lung diseases characterized by defective mucus clearance have resulted in a variety of therapies, which might be able to enhance clearance from the lungs. In addition, ways to study in vivo mucociliary clearance in humans have been developed. This can be used as a means to assess the effect of different pharmacological interventions on clearance rate, to study the importance of defective mucus clearance in different lung diseases or as a diagnostic tool in the work‐up of patients with recurrent airway diseases. The aim of this review is to provide an overview of the anatomy, physiology, pathophysiology, and clinical aspects of mucociliary clearance and to present a clinically applicable test that can be used for in vivo assessment of mucociliary clearance in patients. In addition, the reader will be presented with a protocol for this test, which has been validated and used as a diagnostic routine tool in the work‐up of patients suspected for primary ciliary dyskinesia at Rigshospitalet, Denmark for over a decade.

Inflammatory, anti-inflammatory and regulatory cytokines in relatively healthy lung tissue as an essential part of the local immune system

“…Pro-inflammatory cytokines (IL-1, IL-6) and chemokines produced by epithelial cells recruit and activate immune cells in the submucosa 5 . Importantly, specifically IL-1α even boosts the epithelial cell participation in the immune response through the autocrine stimulation 8 . However, to suppress the immune responses caused by the release of IL-1, the epithelium might release anti-inflammatory cytokine IL-10 3 .…”

“…Interestingly, epithelial tissue is among the structures that possess immunogenicity 6,7 . The airway epithelium works as a physical barrier in lungs to maintain effective mucociliary clearance 8,9 . Mucus covers the upper surface of the epithelium and actively serves as an environment capable of preventing airways from possible inhaled harm 8,10 .…”

“…The airway epithelium works as a physical barrier in lungs to maintain effective mucociliary clearance 8,9 . Mucus covers the upper surface of the epithelium and actively serves as an environment capable of preventing airways from possible inhaled harm 8,10 . Macrophages resident in non-immune tissue participate in tissue-specific homeostasis.…”

Nasal mucociliary clearance in chronic renal failure: comparision of pre-dialysis and dialysis stages

“…Effective MCC requires appropriate mucus production, coordinated ciliary activity, and the mucus-cilia interaction. Cilia line the nasopharynx, middle ear, paranasal sinuses, and tracheobronchial airways; therefore, any disturbance in MCC leads to the stagnation of secretions and recurrent middle ear, sinonasal, and lower respiratory tract infections (5,(9)(10)(11) . There are two main causes of MCC impairment: impaired ciliary function or mucus structure and movement (12,13) .…”

“…CRF is an irreversible condition with multiple aetiologies that may lead to many physiological, haematological, metabolic, endocrine, cardiovascular, and respiratory system problems (3,4) . Mucociliary clearance (MCC) is the primary defence mechanism in the respiratory system against noxious inhaled materials (5) . MCC occurs via the synchronised movement of cilia in the respiratory tract in a manner that propels mucus and other substances trapped within the mucus towards the pharynx to be swallowed (6) .…”