Fibrin formation by wounded bronchial epithelial cell layers in vitro is essential for normal epithelial repair and independent of plasma proteins.
BACKGROUND
The bronchial epithelium is in contact with, and continually damaged by, the environment. Animal models have indicated that normal epithelial repair is rapid and supported by the formation of a provisional fibrin matrix that is exclusively plasma-derived.


OBJECTIVE
Our objectives were to demonstrate the ability of normal human bronchial epithelial (NHBE) cells to produce coagulation cascade proteins and form fibrin in response to damage, independently of plasma proteins, and to show that formation of a cross-linked fibrin matrix is essential for normal epithelial repair in vitro.


METHODS
Primary NHBE cells and cells of the 16HBE 14o- bronchial epithelial cell line were grown and maintained in vitro prior to mechanical wounding of confluent monolayers in serum-free media. Tissue factor (TF) and factor XIII (FXIII) were visualized on 16HBE 14o- monolayers using immunohistochemistry. The time-dependent expression of TF, factor VII (FVII), factor X (FX), fibrinogen, soluble fibrin, FXIII subunit A (FXIIIA) and D-dimers following wounding of confluent 16HBE 14o- monolayers was investigated using immunoassays. TF and FVII expression at the mRNA level was investigated by RT-PCR. The role of coagulation cascade proteins in the repair response of NHBE and 16HBE 14o- monolayers was investigated using neutralizing antibodies.


RESULTS
Active TF was constitutively expressed in 16HBE 14o- cells. Levels of FVII, FX, fibrinogen, soluble fibrin, FXIIIA and D-dimers in culture supernatants increased rapidly and were maximal 20 min after wounding the monolayers. Expression of TF and FVII mRNA was significantly increased 10 and 4 h, respectively, after wounding. Neutralizing antibodies to TF, fibrinogen and FXIIIA significantly inhibited repair of NHBE and 16HBE 14o- cell layers.


CONCLUSIONS
The bronchial epithelium has the potential to respond rapidly to mechanical damage by forming a cross-linked fibrin matrix that is essential for normal epithelial repair, independently of plasma proteins.
Perrio
M J
MJ
Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK.
Ewen
D
D
Trevethick
M A
MA
Salmon
G P
GP
Shute
J K
JK
D000906:Antibodies / Q000494:pharmacology; D001798:Blood Proteins / Q000378:metabolism*; D001980:Bronchi / Q000166:cytology; D002460:Cell Line; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000378:metabolism*; D005167:Factor VII / Q000235:genetics / Q000378:metabolism; D005170:Factor X / Q000378:metabolism; D005176:Factor XIII / Q000276:immunology / Q000378:metabolism; D005337:Fibrin / Q000378:metabolism*; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism; D005340:Fibrinogen / Q000276:immunology / Q000378:metabolism; D015870:Gene Expression / Q000235:genetics; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D016685:Mitomycin / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013925:Thromboplastin / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D014945:Wound Healing / Q000187:drug effects
D000906:Antibodies; D001798:Blood Proteins; D016895:Culture Media, Serum-Free; D005338:Fibrin Fibrinogen Degradation Products; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D053773:Transforming Growth Factor beta1; C036309:fibrin fragment D; D016685:Mitomycin; D005167:Factor VII; D005170:Factor X; D005337:Fibrin; D005340:Fibrinogen; D005176:Factor XIII; D013925:Thromboplastin