Ultrastructural Changes in Human Nasal Cilia Caused by the Common Cold and Recovery of Ciliated Epithelium

Abstract

Changes in the ultrastructure of human respiratory cilia caused by the common cold were studied in 12 patients. The nasal mucosa was studied three times: on the first or second day after the beginning of symptoms, and 1 week and 3 weeks after the first biopsy. The damage was most severe at 1 week. The most remarkable finding was the loss of cilia and ciliated cells. However, the ultrastructure was usually normal, without any increase in tubular anomalies, as compared with the normal material of the previous reports. Three weeks after the beginning of the disease the number of cilia and ciliated cells had increased to nearly normal. However, as a sign of regeneration, immature short cilia (0.7 to 2.5 μm in length) were often seen. The ciliary orientation was uniform, dynein arms were normal, and there was no increase in the number of tubular anomalies. The results suggest that the impaired mucociliary function during viral infections is due to the loss of cilia and ciliated cells, rather than to ultrastructural anomalies in the cilia. The development of tubular anomalies and random ciliary orientation may require more extensive exposure to factors affecting ciliary function.

The effects of coronavirus on human nasal ciliated respiratory epithelium

“…This is in keeping with other reports of electron microscopy of human nasal and bronchial epithelium during episodes of the common cold [1,3,24,25]. In contrast, there are many published reports of in vitro coronavirus-infected cells [26][27][28].…”

“…The time taken for the upper respiratory tract epithelium to return to normal following exposure to coronavirus infection is not known. In naturally-acquired colds, the epithelium returns to normal in the majority of patients by 3 weeks [1], while mucus clearance may be abnormal for several weeks following viral infection [5].…”

“…Understanding the interaction between virus and epithelium is an important step in determining the mechanisms by which symptoms are produced. Structural damage to the respiratory epithelium [1][2][3] and abnormal ciliary function [1,4,5] during viral infection may disrupt the mucociliary escalator [4,6], contributing to symptoms of nasal discharge and obstruction. Although some infected volunteers suffer nasal congestion and discharge, an equal number of infected subjects have no definite symptoms.…”

Inner dynein arm defects causing primary ciliary dyskinesia: repeat testing required

“…However, in two cases the epithelium appeared healthy. It is known that damage to the epithelium, for example following a viral upper respiratory tract infection, can affect ciliary function and the EM appearance of cilia [13,[16][17][18]. Although we do not biopsy patients who have reported a symptomatic upper respiratory tract infection within the previous 6 weeks, we know that a proportion of people with a viral infection may show significant damage to the ciliated respiratory epithelium without being aware of any symptoms [13].…”

Mucociliary clearance: pathophysiological aspects

“…In some instances, the condition can be hard to differentiate from PCD due to overlapping findings in the tests meant for diagnosing PCD (Carson et al, 1980;Reimer et al, 1980;Rautiainen et al, 1992;Calderon-Garciduenas et al, 2001;Randell & Boucher, 2006;Livraghi & Randell, 2007;Wang et al, 2012).…”