STEM-CELLS OF THE RESPIRATORY EPITHELIUM AND THEIR IN-VITRO CULTIVATION

Parenchymal (epithelial or mesenchymal) 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 vario us definitions, markers for identification, methods of isolation and i n vitro cultivation, and lineage mechanisms have been proposed and som e of them are now proven to be valid and useful. In this article attem pts will be made to explore whether there are stem cells in the lower respirator system (from the trachea to the lung periphery) and what th ey look like. Because of its anatomical and functional complexity the stem cell concept for the respirator system has been developing rather slowly. Nevertheless, the data available seem to indicate that in ana logy to the above mentioned organs there is only one type of epithelia l stem cells throughout all sections of the lower respiratory system d uring fetal through adult stages. They are multipotent for cell differ entiation and able to yield lineage progenitors for ciliated, goblet, basal, Clara, neuroendocrine, alveolar type 1 and alveolar type 2 cell s.