Moioli Eduardo K, Clark Paul A, Chen Mo, Dennis James E, Erickson Helaman P, Gerson Stanton L, Mao Jeremy J
Columbia University Medical Center, Tissue Engineering and Regenerative Medicine Laboratory, College of Dental Medicine, New York, New York, United States of America.
PLoS One. 2008;3(12):e3922. doi: 10.1371/journal.pone.0003922. Epub 2008 Dec 15.
Poor angiogenesis is a major road block for tissue repair. The regeneration of virtually all tissues is limited by angiogenesis, given the diffusion of nutrients, oxygen, and waste products is limited to a few hundred micrometers. We postulated that co-transplantation of hematopoietic and mesenchymal stem/progenitor cells improves angiogenesis of tissue repair and hence the outcome of regeneration. In this study, we tested this hypothesis by using bone as a model whose regeneration is impaired unless it is vascularized. Hematopoietic stem/progenitor cells (HSCs) and mesenchymal stem/progenitor cells (MSCs) were isolated from each of three healthy human bone marrow samples and reconstituted in a porous scaffold. MSCs were seeded in micropores of 3D calcium phosphate (CP) scaffolds, followed by infusion of gel-suspended CD34(+) hematopoietic cells. Co-transplantation of CD34(+) HSCs and CD34(-) MSCs in microporous CP scaffolds subcutaneously in the dorsum of immunocompromised mice yielded vascularized tissue. The average vascular number of co-transplanted CD34(+) and MSC scaffolds was substantially greater than MSC transplantation alone. Human osteocalcin was expressed in the micropores of CP scaffolds and was significantly increased upon co-transplantation of MSCs and CD34(+) cells. Human nuclear staining revealed the engraftment of transplanted human cells in vascular endothelium upon co-transplantation of MSCs and CD34(+) cells. Based on additional in vitro results of endothelial differentiation of CD34(+) cells by vascular endothelial growth factor (VEGF), we adsorbed VEGF with co-transplanted CD34(+) and MSCs in the microporous CP scaffolds in vivo, and discovered that vascular number and diameter further increased, likely owing to the promotion of endothelial differentiation of CD34(+) cells by VEGF. Together, co-transplantation of hematopoietic and mesenchymal stem/progenitor cells may improve the regeneration of vascular dependent tissues such as bone, adipose, muscle and dermal grafts, and may have implications in the regeneration of internal organs.
血管生成不足是组织修复的主要障碍。由于营养物质、氧气和代谢废物的扩散仅限于几百微米，几乎所有组织的再生都受到血管生成的限制。我们推测，造血干细胞和间充质干/祖细胞的共移植可改善组织修复的血管生成，从而提高再生效果。在本研究中，我们以骨骼为模型来验证这一假设，因为骨骼的再生若不形成血管则会受损。从三个健康人骨髓样本中分别分离出造血干/祖细胞（HSCs）和间充质干/祖细胞（MSCs），并将它们重构成多孔支架。将MSCs接种到三维磷酸钙（CP）支架的微孔中，随后注入凝胶悬浮的CD34(+)造血细胞。在免疫缺陷小鼠背部皮下将CD34(+) HSCs和CD34(-) MSCs共移植到微孔CP支架中，形成了血管化组织。共移植CD34(+)和MSC支架的平均血管数量明显多于单独移植MSC。人骨钙素在CP支架的微孔中表达，在MSCs和CD34(+)细胞共移植后显著增加。人细胞核染色显示，在MSCs和CD34(+)细胞共移植后，移植的人细胞在血管内皮中植入。基于血管内皮生长因子（VEGF）对CD34(+)细胞内皮分化的体外实验结果，我们在体内将VEGF与共移植的CD34(+)和MSCs吸附到微孔CP支架中，发现血管数量和直径进一步增加，这可能是由于VEGF促进了CD34(+)细胞的内皮分化。总之，造血干细胞和间充质干/祖细胞的共移植可能会改善血管依赖性组织（如骨骼、脂肪、肌肉和皮肤移植物）的再生，并可能对内脏器官的再生具有重要意义。
