Kawao Naoyuki, Tamura Yukinori, Okumoto Katsumi, Yano Masato, Okada Kiyotaka, Matsuo Osamu, Kaji Hiroshi
Department of Physiology and Regenerative Medicine, Kinki University Faculty of Medicine, Osakasayama, Osaka, Japan; and.
Life Science Research Institute, Kinki University, Osakasayama, Osaka, Japan.
Am J Physiol Endocrinol Metab. 2014 Aug 1;307(3):E278-88. doi: 10.1152/ajpendo.00129.2014. Epub 2014 Jun 10.
Further development in research of bone regeneration is necessary to meet the clinical demand for bone reconstruction. Recently, we reported that plasminogen is crucial for bone repair through enhancement of vessel formation. However, the details of the role of tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) in the bone repair process still remain unknown. Herein, we examined the effects of plasminogen activators on bone repair after a femoral bone defect using tPA-deficient (tPA(-/-)) and uPA-deficient (uPA(-/-)) mice. Bone repair of the femur was delayed in tPA(-/-) mice, unlike that in wild-type (tPA(+/+)) mice. Conversely, the bone repair was comparable between wild-type (uPA(+/+)) and uPA(-/-) mice. The number of proliferative osteoblasts was decreased at the site of bone damage in tPA(-/-) mice. Moreover, the proliferation of primary calvarial osteoblasts was reduced in tPA(-/-) mice. Recombinant tPA facilitated the proliferation of mouse osteoblastic MC3T3-E1 cells. The proliferation enhanced by tPA was antagonized by the inhibition of endogenous annexin 2 by siRNA and by the inhibition of extracellular signal-regulated kinase (ERK)1/2 phosphorylation in MC3T3-E1 cells. Vessel formation as well as the levels of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) were decreased at the damaged site in tPA(-/-) mice. Our results provide novel evidence that tPA is crucial for bone repair through the facilitation of osteoblast proliferation related to annexin 2 and ERK1/2 as well as enhancement of vessel formation related to VEGF and HIF-1α at the site of bone damage.
为满足骨重建的临床需求，骨再生研究有必要进一步发展。最近，我们报道纤溶酶原通过增强血管形成对骨修复至关重要。然而，组织型纤溶酶原激活剂（tPA）和尿激酶型纤溶酶原激活剂（uPA）在骨修复过程中的具体作用细节仍不清楚。在此，我们使用tPA基因缺陷（tPA(-/-)）和uPA基因缺陷（uPA(-/-)）小鼠，研究了纤溶酶原激活剂对股骨缺损后骨修复的影响。与野生型（tPA(+/+)）小鼠不同，tPA(-/-)小鼠股骨的骨修复延迟。相反，野生型（uPA(+/+)）和uPA(-/-)小鼠之间的骨修复情况相当。tPA(-/-)小鼠骨损伤部位增殖性成骨细胞数量减少。此外，tPA(-/-)小鼠原代颅骨成骨细胞的增殖也减少。重组tPA促进小鼠成骨细胞MC3T3-E1细胞的增殖。tPA增强的增殖被siRNA抑制内源性膜联蛋白2以及抑制MC3T3-E1细胞中细胞外信号调节激酶（ERK）1/2磷酸化所拮抗。tPA(-/-)小鼠损伤部位的血管形成以及血管内皮生长因子（VEGF）和缺氧诱导因子-1α（HIF-1α）水平均降低。我们的结果提供了新的证据，表明tPA通过促进与膜联蛋白2和ERK1/2相关的成骨细胞增殖以及增强与VEGF和HIF-1α相关的骨损伤部位血管形成，对骨修复至关重要。
