Respiratory epithelium

Abstract: The previous articles of this series provided presumptive evidence that the four main differentiated cell types in the epithelium of the mouse small intestine: villus columnar, mucous, entero-endocrine, and Paneth cells, originate from the same precursor, the crypt-base columnar cell. In the present work, direct evidence was obtained in support of this view. It was first found that crypt-base columnar cells phagocytose non-viable cells in their vicinity, with the result that a large phagosome appears in the cytoplasm. Such phagosomes were then used as markers to follow the evolution of crypt-base columnar cells. In normal control animals, a rare crypt-base columnar cell includes a large phagosome containing Paneth cell remnants. By six hours after injection of two μCi 3H-thymidine per g body weight, a fair number of crypt-base columnar cells include a different type of phagosome containing labeled nucleus and granulefree cytoplasm, which is attributed to phagocytosis of a labeled crypt-base columnar cell killed by beta-radiation from the incorporated 3H-thymidine. By 12 hours after 3H-thymidine injection, phagosomes have appeared in partly differentiated mid-crypt columnar cells and oligomucous cells; by 18–24 hours, in fully differentiated columnar cells and in Paneth cells; and by 30 hours, in an entero-endocrine cell. Since phagosomes are first found in crypt-base columnar cells and only later in the four differentiated cell types, it is concluded that crypt-base columnar cells transform into cells of these four types and, therefore, behave as the stem cells of the epithelium. The finding of rare epithelial cells containing two different types of secretory material (either mucous globules and entero-endocrine granules, or mucous globules and Paneth cell granules) confirms that the stem cells are multipotential. These findings support the Unitarian Theory of epithelial cell formation in the small intestine.

Abstract: We measured bronchial reactivity to inhaled histamine and prepared electron micrographs from bronchial biopsies from 8 asthmatic patients who never smoked (2 females, 6 males, 18 to 62 yr of age). Judging from their clinical histories and the need for medication and long-term follow-up of PEF values, 2 of them had mild asthma, 3 moderately severe, and 3 severe asthma. They had not experienced respiratory infections for at least 2 months prior to the study. The result, obtained from the cumulative dose-response curve, was expressed as the provocative dose (PD20) of histamine producing a 20% fall in forced expiratory volume in one second (FEV1). In 5 patients, the PD20 varied from 0.049 mg to 2.234 mg. In the sixth patient, only PD15 could be measured (5.187 mg). In 2 patients, the low initial FEV1 values, because of severe, partly irreversible obstruction, prevented the measurement of bronchial reactivity. Bronchial biopsies were taken with rigid tube bronchoscopy from 3 levels: (1) at the carina of the right upper lobe, (2) at the opening of the right middle or lower lobe, and (3) inside the right lower lobe. The specimens were prepared for both light and electron microscopy. Fresh biopsies showed that asthma patients can have epithelial destruction at all levels of the airways. The ciliated cells appeared to be the most destroyed cell type in the epithelium. Intraepithelial nerves and mast cells were seen. Epithelial destruction in the respiratory tract of the asthma patients with mild to severe bronchial hyperresponsiveness was prominent enough to expose the epithelial nerves for specific or nonspecific stimuli.

Abstract: Direct transfer of the normal cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene to airway epithelium was evaluated using a replication-deficient recombinant adenovirus (Ad) vector containing normal human CFTR cDNA (Ad-CFTR). In vitro Ad-CFTR-infected CFPAC-1 CF epithelial cells expressed human CFTR mRNA and protein and demonstrated correction of defective cAMP-mediated Cl − permeability. Two days after in vivo intratracheal introduction of Ad-CFTR in cotton rats, in situ analysis demonstrated human CFTR gene expression in lung epithelium. PCR amplification of reverse transcribed lung RNA demonstrated human CFTR transcripts derived from Ad-CFTR, and Northern analysis of lung RNA revealed human CFTR transcripts for up to 6 weeks. Human CFTR protein was detected in epithelial cells using anti-human CFTR antibody 11–14 days after infection. While the safety and effectiveness remain to be demonstrated, these observations suggest the feasibility of in vivo CFTR gene transfer as therapy for the pulmonary manifestations of CF.

Abstract: The respiratory epithelium is a potential site for somatic gene therapy for the common hereditary disorders alpha 1-antitrypsin (alpha 1AT) deficiency and cystic fibrosis. A replication-deficient adenoviral vector (Ad-alpha 1AT) containing an adenovirus major late promoter and a recombinant human alpha 1AT gene was used to infect epithelial cells of the cotton rat respiratory tract in vitro and in vivo. Freshly isolated tracheobronchial epithelial cells infected with Ad-alpha 1AT contained human alpha 1AT messenger RNA transcripts and synthesized and secreted human alpha 1AT. After in vivo intratracheal administration of Ad-alpha 1AT to these rats, human alpha 1AT messenger RNA was observed in the respiratory epithelium, human alpha 1AT was synthesized and secreted by lung tissue, and human alpha 1AT was detected in the epithelial lining fluid for at least 1 week.