Forsten K E, Courant N A, Nugent M A
Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118, USA.
J Cell Physiol. 1997 Aug;172(2):209-20. doi: 10.1002/(SICI)1097-4652(199708)172:2<209::AID-JCP8>3.0.CO;2-S.
Basic fibroblast growth factor (bFGF) is a known mitogen for vascular smooth muscle cells and has been implicated as having a role in a number of proliferative vascular disorders. Binding of bFGF to heparin or heparan sulfate has been demonstrated to both stimulate and inhibit growth factor activity. The activity, towards bFGF, of heparan sulfate proteoglycans present within the vascular system is likely related to the chemical characteristics of the glycosaminoglycan as well as the structure and pericellular location of the intact proteoglycans. We have previously shown that endothelial conditioned medium inhibits both bFGF binding to vascular smooth muscle cells and bFGF stimulated cell proliferation in vitro. In the present study, we have isolated proteoglycans from endothelial cell conditioned medium and demonstrated that they are responsible for the bFGF inhibitory activity. We further separated endothelial secreted proteoglycans into two fractions, PG-A and PG-B. The large sized fraction (PG-A) had greater inhibitory activity than did PG-B for both bFGF binding and bFGF stimulation of vascular smooth muscle cell proliferation. The increased relative activity of PG-A was attributed, in part, to larger heparan sulfate chains which were more potent inhibitors of bFGF binding than the smaller heparan sulfate chains on PG-B. Both proteoglycan fractions contained perlecan-like core proteins; however, PG-A contained an additional core protein (approximately 190 kDa) that was not observed in PG-B. Both proteoglycan fractions bound bFGF directly, and PG-A bound a significantly greater relative amount of bFGF than did PG-B. Thus the ability of endothelial heparan sulfate proteoglycans to bind bFGF and prevent its association with vascular smooth muscle cells appears essential for inhibition of bFGF-induced mitogenesis. The production of potent bFGF inhibitory heparan sulfate proteoglycans by endothelial cells might contribute to the maintenance of vascular homeostasis.
碱性成纤维细胞生长因子（bFGF）是一种已知的血管平滑肌细胞促有丝分裂原，并被认为在多种增殖性血管疾病中起作用。已证明bFGF与肝素或硫酸乙酰肝素结合既能刺激又能抑制生长因子活性。血管系统中存在的硫酸乙酰肝素蛋白聚糖对bFGF的活性可能与糖胺聚糖的化学特性以及完整蛋白聚糖的结构和细胞周围位置有关。我们之前已经表明，内皮细胞条件培养基在体外既能抑制bFGF与血管平滑肌细胞的结合，又能抑制bFGF刺激的细胞增殖。在本研究中，我们从内皮细胞条件培养基中分离出蛋白聚糖，并证明它们负责bFGF抑制活性。我们进一步将内皮细胞分泌的蛋白聚糖分为两个部分，PG-A和PG-B。对于bFGF与血管平滑肌细胞的结合以及bFGF刺激的增殖，大尺寸部分（PG-A）比PG-B具有更强的抑制活性。PG-A相对活性的增加部分归因于更大的硫酸乙酰肝素链，其比PG-B上较小的硫酸乙酰肝素链更有效地抑制bFGF结合。两个蛋白聚糖部分都含有类基底膜聚糖核心蛋白；然而，PG-A含有一种在PG-B中未观察到的额外核心蛋白（约190 kDa）。两个蛋白聚糖部分都直接结合bFGF，并且PG-A结合的bFGF相对量明显大于PG-B。因此，内皮硫酸乙酰肝素蛋白聚糖结合bFGF并阻止其与血管平滑肌细胞结合的能力似乎是抑制bFGF诱导的有丝分裂所必需的。内皮细胞产生有效的bFGF抑制性硫酸乙酰肝素蛋白聚糖可能有助于维持血管稳态。
