Nichol Jason W, Khan Azeem R, Birbach Mariusz, Gaynor J William, Gooch Keith J
Department of Bioengineering, Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Tissue Eng Part A. 2009 Jun;15(6):1281-90. doi: 10.1089/ten.tea.2008.0034.
We previously demonstrated the ability to create engineered arteries by carefully controlling the mechanical environment of intact arteries perfused ex vivo, yielding engineered arteries with native appearance and vasoactive response. Increased axial strain was sufficient to increase length up to 20% in 9 days through a growth and remodeling response. The amount of the achievable length increase, however, was highly dependent on the hemodynamic conditions acting through unknown mechanisms. Because matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) activity is increased, and often required, in mechanically induced remodeling in vivo, MMP-2 and MMP-9 expression was investigated to elucidate the hemodynamic mediation of artery length. Carotid arteries from 30 kg pigs were perfused for 9 days ex vivo at either in situ axial strain or with a gradual 50% increase in axial strain, under either arterial or reduced hemodynamics ( approximately 10% of arterial hemodynamics). MMP-2 protein expression increased roughly twofold, while MMP-9 expression increased threefold under either reduced hemodynamics or increased axial strain (p < 0.05). The combination of reduced hemodynamics with increased axial strain demonstrated an additive increase in MMP-9 protein (p < 0.05) with no further change in MMP-2 expression. To investigate the mechanism by which axial strain and hemodynamics could additively increase MMP-9 expression, the expression of nuclear factor kappa B (NF-kappaB) subunits p50 and p65 was evaluated. Axial strain stimulated p65 expression and localization, while hemodynamics increased p50 expression, with both molecules being expressed only when both mechanical stimuli were applied. These data suggest that MMP-9 expression can be simultaneously stimulated by separate mechanical stimuli mediated by p50 and p65 expression, and that by using conditions that maximize MMP-9 expression, we can create an optimal remodeling environment to better direct the growth of engineered arteries and other tissues.
我们之前展示了通过仔细控制离体灌注的完整动脉的机械环境来构建工程动脉的能力，从而产生具有天然外观和血管活性反应的工程动脉。通过生长和重塑反应，增加的轴向应变足以在9天内使长度增加高达20%。然而，可实现的长度增加量高度依赖于通过未知机制起作用的血流动力学条件。因为在体内机械诱导的重塑中基质金属蛋白酶-2（MMP-2）和基质金属蛋白酶-9（MMP-9）的活性会增加且通常是必需的，所以研究了MMP-2和MMP-9的表达以阐明动脉长度的血流动力学调节作用。对30千克猪的颈动脉在原位轴向应变或轴向应变逐渐增加50%的条件下进行9天的离体灌注，灌注条件为动脉血流动力学或降低的血流动力学（约为动脉血流动力学的10%）。在降低的血流动力学或增加的轴向应变条件下，MMP-2蛋白表达大致增加两倍，而MMP-9表达增加三倍（p<0.05）。降低的血流动力学与增加的轴向应变相结合，显示MMP-9蛋白有累加性增加（p<0.05），而MMP-2表达没有进一步变化。为了研究轴向应变和血流动力学可累加增加MMP-9表达的机制，评估了核因子κB（NF-κB）亚基p50和p65的表达。轴向应变刺激p65的表达和定位，而血流动力学增加p50的表达，这两种分子仅在同时施加两种机械刺激时才表达。这些数据表明，MMP-9的表达可由p50和p65表达介导的单独机械刺激同时刺激，并且通过使用使MMP-9表达最大化的条件，我们可以创建一个最佳的重塑环境，以更好地指导工程动脉和其他组织的生长。
