Mechanism of pancreatic beta cell expansion by bone marrow transplantation

骨髓移植可增加β细胞质量，但其内在机制尚不清楚。本研究对其作用机制进行了初步探讨。几种条件下的骨髓移植实验表明，全身照射不注射骨髓细胞可以增加β细胞质量。另一方面，仅对骨髓或仅对胰腺进行照射并不能增加β细胞质量。此外，利用β细胞特异性的血管内皮生长因子-A基因敲除小鼠，我们发现β细胞中的血管内皮生长因子-A的表达对于骨髓移植后的β细胞质量的增加是必不可少的。因此，全身照射对于骨髓移植来说是必要和充分的，诱导的β细胞质量增加和β细胞中的血管内皮生长因子-A也是造成这种现象的必要因素。

Bone marrow transplantation increases beta cell mass, however its underlying mechanism has not been elucidated yet. In this study, we investigated its mechanism. Bone marrow transplantation experiments under several conditions revealed that systemic irradiation without injection of bone marrow cells can increase beta cell mass. On the other hand, irradiation only to bone marrow or only to pancreas cannot increase beta cell mass. In addition, using beta cell specific VEGF-A knock out mice, we found that VEGF-A expression in beta cells are essential for the increase in beta cell mass by bone marrow transplantation. Accordingly, systemic irradiation is essential and sufficient for bone marrow transplantation induced increase in beta cell mass and VEGF-A in beta cells are also essential for this phenomenon.