Bioengineering Graduate Program, University of Notre Dame, Notre Dame, Notre Dame, IN, USA.
Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Notre Dame, IN, USA.
FASEB J. 2021 May;35(5):e21498. doi: 10.1096/fj.202002426RR.
Dysfunction of the lymphatic system is associated with a wide range of disease phenotypes. The restoration of dysfunctional lymphatic vessels has been hypothesized as an innovative method to rescue healthy phenotypes in diseased states including neurological conditions, metabolic syndromes, and cardiovascular disease. Compared to the vascular system, little is known about the molecular regulation that controls lymphatic tube morphogenesis. Using synthetic hyaluronic acid (HA) hydrogels as a chemically and mechanically tunable system to preserve lymphatic endothelial cell (LECs) phenotypes, we demonstrate that low matrix elasticity primes lymphatic cord-like structure (CLS) formation directed by a high concentration of vascular endothelial growth factor-C (VEGF-C). Decreasing the substrate stiffness results in the upregulation of key lymphatic markers, including PROX-1, lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), and VEGFR-3. Consequently, higher levels of VEGFR-3 enable stimulation of LECs with VEGF-C which is required to both activate matrix metalloproteinases (MMPs) and facilitate LEC migration. Both of these steps are critical in establishing CLS formation in vitro. With decreases in substrate elasticity, we observe increased MMP expression and increased cellular elongation, as well as formation of intracellular vacuoles, which can further merge into coalescent vacuoles. RNAi studies demonstrate that MMP-14 is required to enable CLS formation and that LECs sense matrix stiffness through YAP/TAZ mechanosensors leading to the activation of their downstream target genes. Collectively, we show that by tuning both the matrix stiffness and VEGF-C concentration, the signaling pathways of CLS formation can be regulated in a synthetic matrix, resulting in lymphatic networks which will be useful for the study of lymphatic biology and future approaches in tissue regeneration.
淋巴系统功能障碍与广泛的疾病表型有关。恢复功能失调的淋巴管被认为是一种创新的方法,可以挽救包括神经疾病、代谢综合征和心血管疾病在内的疾病状态下的健康表型。与血管系统相比,人们对控制淋巴管管腔形态发生的分子调节知之甚少。我们使用合成透明质酸(HA)水凝胶作为一种化学和机械可调系统来保留淋巴管内皮细胞(LEC)表型,证明低基质弹性通过高浓度血管内皮生长因子-C(VEGF-C)启动淋巴管索状结构(CLS)形成。降低基质刚度会导致关键淋巴管标志物的上调,包括 PROX-1、淋巴管内皮透明质酸受体 1(LYVE-1)和 VEGFR-3。因此,更高水平的 VEGFR-3 能够刺激 LEC 与 VEGF-C 相互作用,这对于激活基质金属蛋白酶(MMPs)和促进 LEC 迁移都是必需的。这两个步骤对于在体外建立 CLS 形成都是至关重要的。随着基质弹性的降低,我们观察到 MMP 表达增加和细胞伸长增加,以及细胞内空泡的形成,这些空泡可以进一步融合成融合空泡。RNAi 研究表明,MMP-14 是形成 CLS 所必需的,并且 LEC 通过 YAP/TAZ 机械感受器感知基质刚度,从而激活其下游靶基因。总的来说,我们表明,通过调节基质刚度和 VEGF-C 浓度,可以在合成基质中调节 CLS 形成的信号通路,从而形成淋巴管网络,这将有助于淋巴管生物学的研究和未来组织再生的方法。