Zagai Ulrika, Fredriksson Karin, Rennard Stephen I, Lundahl Joachim, Sköld C Magnus
Department of Medicine, Karolinska Hospital, Stockholm, Sweden.
Respir Res. 2003;4(1):13. doi: 10.1186/1465-9921-4-13. Epub 2003 Oct 17.
Platelets are thought to play a role in a variety of inflammatory conditions in the lung, some of which may lead to fibrosis. In the current study we tested the hypothesis that whole platelets and platelet lysate can mediate remodelling of extracellular matrix in vitro by affecting fibroblast-mediated contraction of a collagen gel. We also sought to determine to what extent platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) contribute to this effect.
Washed platelets, isolated from healthy blood donors, and platelet lysate (freezing and thawing), were cast together with human lung fibroblasts in three-dimensional collagen gels. The gels were then released and cultured for four days. PDGF and TGF-beta1 concentrations were measured in culture supernatants by ELISA.
Both platelets and platelet lysate augmented fibroblast-mediated gel contraction in a time and concentration dependent manner (19.9% +/- 0.1 (mean +/- SEM) of initial area vs. 48.0% +/- 0.4 at 48 hours; P < 0.001 and 41.5% +/- 0.6 vs. 60.6% +/- 0.3 at 48 hours; P < 0.001, respectively). Fixed platelets had no effect in the system. Both TGF-beta1 and PDGF-AA/AB were released in co-culture. PDGF-AA/AB had a maximum release at 24 hours whereas TGF-beta1 release increased with longer culture periods. Neutralising antibodies to these mediators partially inhibited platelet-induced gel contraction.
We conclude that platelets may promote remodelling of extracellular matrix in vitro and that PDGF and TGF-beta partially mediate this effect, also indicating a role for other mediators. The findings may be an important mechanism in regulating repair processes after injury.
血小板被认为在肺部多种炎症状态中发挥作用，其中一些炎症状态可能导致纤维化。在本研究中，我们检验了以下假设：完整血小板和血小板裂解物可通过影响成纤维细胞介导的胶原凝胶收缩在体外介导细胞外基质重塑。我们还试图确定血小板衍生生长因子（PDGF）和转化生长因子-β（TGF-β）在多大程度上促成这种效应。
从健康献血者中分离出的洗涤血小板以及血小板裂解物（冻融处理），与人类肺成纤维细胞一起置于三维胶原凝胶中。然后将凝胶释放并培养4天。通过酶联免疫吸附测定法（ELISA）测量培养上清液中的PDGF和TGF-β1浓度。
血小板和血小板裂解物均以时间和浓度依赖性方式增强了成纤维细胞介导的凝胶收缩（初始面积的%19.9±0.1（平均值±标准误）对比48小时时的48.0%±0.4；P<0.001；以及48小时时的41.5%±0.6对比60.6%±0.3；P分别<0.001）。固定化血小板在该系统中无作用。在共培养中TGF-β1和PDGF-AA/AB均有释放。PDGF-AA/AB在24小时时有最大释放量，而TGF-β1的释放随培养时间延长而增加。针对这些介质的中和抗体部分抑制了血小板诱导的凝胶收缩。
我们得出结论，血小板可能在体外促进细胞外基质重塑，并且PDGF和TGF-β部分介导了这种效应，这也表明其他介质发挥了作用。这些发现可能是损伤后调节修复过程的一个重要机制。
