Some factors in plasma or thrombi are thought to be related to the progress of the pulmonary fibrosis following the diffuse pulmonary microthromboembolism. Among such factors which promote the proliferation of fibroblasts in vitro, thrombin, factor XIII, PDGF, MDGF and EDGF are included.
The roles of factor XIII or PDGF were investigated in the recovery stage after the diffuse pulmonary microthromboembolism induced by the intravenous injections of tissue thromboplastin (T. Tbp).
In the lungs of rabbits autopsied 4 or 8 weeks after the repeated injections of T. Tbp and PDGF for 3 days, focal interstitial infiltrations of nuclear cells (mainly neutrophils) were seen and alveolar septa were thickened. Foci of such lesions were increased 8 weeks after the same injections for 6 days.
Above results suggest that the interstitial changes may progress to the proliferation of fibroblasts and the increase of collagen fibers.
