Schwager Juan M, Di Maggio Nunzia, Grosso Andrea, Rasadurai Abeelan, Minder Nadja, Hubbell Jeffrey A, Kappos Elisabeth A, Schaefer Dirk J, Briquez Priscilla S, Banfi Andrea, Burger Maximilian G
Regenerative Angiogenesis Laboratory, Department of Biomedicine, Basel University Hospital and University of Basel, Basel, Switzerland.
Department of Plastic, Reconstructive, Aesthetic and Hand Surgery, Basel University Hospital, Basel, Switzerland.
Front Bioeng Biotechnol. 2024 Aug 21;12:1396450. doi: 10.3389/fbioe.2024.1396450. eCollection 2024.
The stromal vascular fraction (SVF) of human adipose tissue is an attractive cell source for engineering grafts with intrinsic vascularization potential, as it is rich in vasculogenic progenitors. However, in order to maintain their functional perfusion it is important to promote the stabilization of newly assembled microvascular networks. We previously found that Semaphorin 3A (Sema3A) promotes the rapid stabilization of new blood vessels induced by VEGF overexpression in skeletal muscle. Here we investigated whether Sema3A could promote the assembly, connection to circulation and persistence of human SVF-derived microvascular networks in engineered grafts.
Recombinant Sema3A was engineered with a transglutaminase substrate sequence (TG-Sema3A) to allow cross-linking into fibrin hydrogels. Grafts were prepared with freshly isolated human SVF cells in fibrin hydrogels decorated with 0, 0.1 or 100 μg/ml TG-Sema3A and implanted subcutaneously in immune-deficient mice.
After 1 week in vivo, the assembly of human-derived networks was similar in all conditions. The outer part of the grafts was populated by blood vessels of both human and mouse origin, which formed abundant hybrid structures within a common basal lamina. About 90% of human-derived blood vessels were functionally connected to the host circulation in all conditions. However, in the control samples human vessels were unstable. In fact, they significantly regressed by 6 weeks and could no longer be found by 12 weeks. In contrast, a low Sema3A dose (0.1 μg/ml) promoted further human vascular expansion by about 2-fold at 6 weeks and protected them from regression until 12 weeks. From a mechanistic point of view, the stabilization of SVF-derived vessels by 0.1 μg/ml of Sema3A correlated with the recruitment of a specific population of monocytes expressing its receptor Neuropilin-1.
In conclusion, Sema3A is a potent stimulator of long-term persistence of microvascular networks derived from human SVF. Therefore, decoration of matrices with Sema3a can be envisioned to promote the functional support of tissue engineered grafts.
人脂肪组织的基质血管成分（SVF）是一种具有吸引力的细胞来源，可用于构建具有内在血管生成潜力的移植物，因为它富含血管生成祖细胞。然而，为了维持其功能性灌注，促进新组装的微血管网络的稳定非常重要。我们之前发现，信号素3A（Sema3A）可促进骨骼肌中VEGF过表达诱导的新血管的快速稳定。在此，我们研究了Sema3A是否能促进工程化移植物中源自人SVF的微血管网络的组装、与循环的连接及持久性。
将重组Sema3A与转谷氨酰胺酶底物序列（TG-Sema3A）进行工程改造，使其能够交联到纤维蛋白水凝胶中。用新鲜分离的人SVF细胞在含有0、0.1或100μg/ml TG-Sema3A的纤维蛋白水凝胶中制备移植物，并皮下植入免疫缺陷小鼠体内。
在体内1周后，所有条件下源自人的网络组装情况相似。移植物的外部有人源和鼠源血管，它们在共同的基膜内形成丰富的混合结构。在所有条件下，约90%的人源血管在功能上与宿主循环相连。然而，在对照样本中，人源血管不稳定。事实上，它们在6周时显著消退，到12周时已无法再找到。相比之下，低剂量的Sema3A（0.1μg/ml）在6周时促进人源血管进一步扩张约2倍，并保护它们直到12周都不消退。从机制角度来看，0.1μg/ml的Sema3A使源自SVF的血管稳定，这与招募表达其受体神经纤毛蛋白-1的特定单核细胞群体相关。
总之，Sema3A是源自人SVF的微血管网络长期持久性的有效刺激因子。因此，可以设想用Sema3A修饰基质以促进组织工程移植物的功能支持。
