To address the roles of several factors such as cellular components, cytokines and signal transduction molecules in proliferation and differentiation of lung epithelial stem cells.

The extracellular matrix substitute Matrigel three-dimensional culture system in vitro and immunohistochemical analysis were used to observe the effects of several common factors that played an important role in the proliferation and differentiation of stem cells on the number, size of colony and differentiation potential of lung epithelial stem cells in vitro.

Lung epithelial stem cells required co-culture with fibroblasts to yield three morphologically distinct colonies including A type, B type and C type and their differentiation profile also varied.Fibroblasts played its role by direct cell-cell contact.Liver or lung endothelial cells were also able to support proliferation of lung epithelial stem cells.The number and size of all types of colonies increased significantly with fibroblast growth factor (FGF) treated.Under the action of FGF, the basal cell markers of different colonies disappeared, while the expressions of alveolar epithelial cell markers increased.When combined fibroblast growth factor receptor inhibitor with FGF, the effect induced by the latter was inhibited except FGF-9.The number and size of spheres significantly increased with leukemia inhibitory factor (LIF), activin receptor-like kinase-5 inhibitor (ALK5-I) or Rho-associated protein kinase inhibitor (ROCK-I) treated.Interestingly, each of these factors brought variable effects on colony types and differentiation spectrum.

Lung epithelial stem cells need co-culture with fibroblasts for their proliferation and differentiation while they present limited proliferation potential with endothelial cells.Proliferation and differentiation of lung epithelial stem cells can be promoted with treatment of FGF, LIF, ALK5-I or ROCK-I in different modes.This results laid a foundation for the further study of lung epithelial stem cells and shed light on their clinical research and application of lung regenerative medicine in the future.

Lung epithelium; Stem cells; Proliferation; Differentiation