A Preliminary Study Of Connective Tissue Growth Factor In Pulmonary Fibrosis

Pulmonary fibrosis is a result of many lung diseases. Its characteristic pathologic manifestation is alveolitis, presenting with proliferation of pulmonary fibroblast and accumulation of extracellular matrix (ECM), leading to lung structure deformation and dysfunction. Since the lesion is often located in pulmonary interstitium, pulmonary fibrosis is classified as lung interstitial disease.Present studies indicate that alveolitis is the initiatory stage of pulmonary fibrosis. In this stage, inflammatory cells are recruit and activated, and then many cytokines are released, triggering a cascade that leading to pulmonary fibroblasts proliferating and ECM accumulating. As a result, pulmonary fibrosis is formed. Connective Tissue Growth Factor (CTGF) is a cysteine-rich peptide that belongs to immediate early gene. CTGF plays an impotent role in development of hepatic and renal fibrosis. However, CTGF's role in pulmonary fibrosis is still unclear.Pulmonary fibrosis is difficult to cure and has a bad prognosis. It's commonly treated with glucocorticoid (GC), which is not satisfying and has many ill effects in long-treated cases. In Chinese medicine theory, pulmonary fibrosis results from stagnation of gas and blood. Coincidently, Panax Notoginseny has a function of keeping gas and blood fluent. Total Saponins of Panax Notoginseny (PNS) is the main active component of Panax Notoginseny. Present studies show that PNS has effect in inhibiting hepatic fibroblasts proliferation and promoting renal fibroblasts apoptosis in vitro. What's more, PNS has therapeutic effect on hepatic and renal fibrosis in animal models. However, it's unknown whether PNS has effect on pulmonary fibrosis at present. In this study, Kuming mice were intra-tracheally injected with bleomycin to induce pulmonary fibrosis. Alveolitis and fibrosis were qualitatively investigated by HE staining. TypeⅠand Ⅲ collagen was investigated by Sirius Red staining, and lung homogeneity hydroxyproline(HYP) content was assayed by acid hydrolysis. CTGF and TGF-β1 protein, as well as CTGF mRNA expression were continuously investigated by Immunohistochemistry and RT-PCR methods respectively. After all, the mechanism ofCTGF's role in pulmonary fibrosis and PNS' therapeutic effect on pulmonary fibrosis were discussed. Data indicated that:1. The murine pulmonary fibrosis model induced by one-off injection of bleomycin (BLM) was stable and manageable, indicating BLM induced pulmonary fibrosis model is still a classic way.2. CTGF was scarcely expressed in normal murine lung. While it was significantly increased in the progress of fibrosis, and had close relationship with fibrosis degree. Pulmonary fibroblast was not only the functional cell of CTGF, but also the original cell of it, indicating CTGF plays an important role in pulmonary fibrosis.3. Both TGF-β1 and CTGF had close relationship with pulmonary fibrosis. However, relationship analysis showed that, part of TGF-β1's function was mediated by CTGF. Thus, CTGF has a more direct effect in fibrosis forming. Since TGF-β1 is a necessary factor, while CTGF is little in normal body, it's reasonable to targeting CTGF but not TGF-β1 in fibrosis therapy.4. All lesion marks in PNS treated group (both early treated and late treated group) were ameliorated, indicating PNS has some therapeutic effect on pulmonary fibrosis. What's more, data showed CTGF and TGF-β1 protein and mRNA were significantly lower in PNS treated group, compared with untreated group, indicating that inhibiting CTGF and TGF-β1 expression may be a mechanism of PNS curing pulmonary fibrosis.5. This study showed that, using abundant DXM early could significantly inhibit initiating and developing of pulmonary fibrosis. Contrast to PNS, using DXM in late stage was in vain. It is probably because DXM can not down-regulate CTGF directly though it can inhibit TGF-β1 expression moderately.