Type I and type IV collagen promote adherence and spreading of human type II pneumocytes in vitro.
Human lung tissue was enzymatically digested with dispase and type II pneumocytes were subsequently separated on a discontinuous metrizamide gradient. In primary adherence assays with freshly isolated cells, mean adherence values of 21.7, 19.6, 13.4, 6.8 and 7.0% were obtained after 48 hours on type I collagen (CI), type IV collagen (CIV), fibronectin (FN), laminin (LM) and tissue culture plastic, respectively. Secondly, readherence and spreading assays were performed with type II pneumocytes, previously cultured on CI, FN, matrix of murine EHS cells, and culture plastic. After a culture period of 48 to 72 hours, the cells were replated and tested on CI, CIV, FN, LM, CI + FN, CI + LM, CIV + FN and CIV + LM substrata in order to find out whether preculture substrata can modulate the adherence response of these cells. Readherence values, 1 hour after replating, were 3.3- to 8.6-fold higher than primary adherence values after 48 hours. The highest readherence values were always obtained on collagen-containing substrata after preculture on fibronectin. Spreading values after replating ranged between 35.4 and 6.6% on collagen-containing substrata, the highest values were again obtained after preculture on FN. Less than 6.9% and 0.5% of the cells spread on pure FN and pure LM, respectively. The data of the present investigation indicate that human type II pneumocytes adhere and spread preferentially on collagenous substrata rather than on other components of the extracellular matrix. This might be important in helping us to understand the functional in vivo activity of these cells, especially as regards re-epithelialization of the injured pulmonary alveolus.