Stem cells of the respiratory epithelium and their in vitro cultivation

Abstract

Parenchymal (epithelial or mesenchyma) stem cells are rapidly drawing both scientific and clinical attention in solid organs like the liver, skin, intestine and abdominal mesothelium, just as has been the case in the hematopoietic system. For the stem cells of these organs various definitions, markers for identification, methods of isolation and in vitro cultivation, and lineage mechanisms have been proposed and some of them are now proven to be valid and useful. In this article attempts will be made to explore whether there are stem cells in the lower respiratory system (from the trachea to the lung periphery) and what they look like. Because of its anatomical and functional complexity the stem cell concept for the respiratory system has been developing rather slowly. Nevertheless, the data available seem to indicate that in analogy to the above mentioned organs there is only one type of epithelial stem cells throughout all sections of the lower respiratory system during fetal through adult stages. They are multipotent for cell differentiation and able to yield lineage progenitors for ciliated, goblet, basal. Clara neuroendocrine, alveolar type 1 and alveolar type 2 cells.

Mammary epithelial stem cells

“…New data about organ-specific stem cells is rapidly accumulating in diverse organ systems, e.g., liver (Michalopoulos and DeFrances, 1997), brain (Levison and Goldman, 1997;McKay, 1997;Morrison et al, 1997), skin (Jones, 1997), lung (Emura, 1997), and muscle (Ferrari et al, 1998). Research on stem cells in blood (Boll, 1980), intestine (Cosentino et al, 1996), cerebellum (Snyder et al, 1992), and retina (Turner and Cepko, 1987;Turner et al, 1990) support the conclusion that more than one type of multipotent cell may be present in an organ system (Morrison et al, 1997).…”

Engraftment of Adult Human Lung Tissue in Nonobese Diabetic/Severe Combined Immunodeficient Mice: A Novel Lung Epithelial Regeneration Model

“…The bronchioloalveolar epithelium shows a classical regenerative response that involves proliferation and differentiation from a few multipotent stem cells or progenitor cells [1][2][3]. Identification of the cellular and molecular signals that direct lung epithelial healing during regeneration would allow the development of novel therapeutic strategies, but data are lacking so far.…”

“…Regeneration of the bronchioloalveolar epithelium is dependent on the survival of a few undifferentiated multipotent progenitor or stem cells at the site of injury [1][2][3]. However, little is known about the kinetics of cell proliferation in the human lung, especially with regard to the localization and timing of proliferation after injury.…”

Growth of putative progenitors of type II pneumocytes in culture of human cystic fibrosis alveoli

“…Being in contact with the external environment, they are frequently injured and a continuous renewal of the alveolar epithelium is necessary to maintain cellular homeostasis. In normal adult tissue, type II pneumocytes are considered to be either progenitor or stem cells of the alveolar epithelium (Uhal, 1997;Emura, 1997). They may divide to generate type II pneumocytes or differentiate into type I pneumocytes.…”