| 摘要: | 骨折癒合是一個複雜的生理作用，其中包含了多種細胞參與在其中。在骨折癒合的過程之中需要血液的灌流及血管新生，最終促進造骨細胞合成新生的骨質而促進骨癒合。在文獻的收集中我們發現超音波是一個具有低能量且可以加速骨癒合之儀器，在臨床的研究及動物實驗當中都可以觀察到超音波可以促進骨合成。而美國FDA (美國食品及藥物管理局) 也證明超音波可以加速骨折之癒合，但是美中不足的地方在於超音波經由那些機轉或訊息路徑促進骨癒合是未知的，因此了解超音波治療之下造骨細胞 (osteoblasts)產生那些反應或引發那些路徑是很重要的課題。細胞中的細胞間質可提供一個細胞平台使細胞生長，另外也參與在多種細胞功能當中，而造骨細胞在骨癒合及骨再塑之過程之中通常需要多種細胞間質來參與。細胞間質水解酵素 (Matrix metalloproteinases; MMP) 其主要的作用是清除collagen及細胞間質，當MMP將不良的細胞間質清除之後造骨細胞才可以分泌新生之細胞間質以促進骨合成及新生。 數種MMPs參與在骨合成之中，其中人類造骨細胞可表現MMP-1, -9及MMP-13，而老鼠造骨細胞只會表現MMP-9, -13但不會表現MMP-1。在之前有報告：機械性刺激可以增加造骨細胞分泌MMP-13，進而參與骨再塑作用，然而超音波刺激對於造骨細胞分泌MMP- 9的作用並不明朗。我們的結果發現超音波可以增加人類造骨細胞分泌MMP-9的表現，另外超音波也可以增加轉錄因子 c-Fos及c-Jun的表現，因此本計劃將探討超音波刺激對MMP-9表現其及上下游的訊息傳遞路徑。由我們的結果也發現超音波也可以增加細胞表面3 integrin，另外超音波可以活化ERK的磷酸化。因此，我們的結果提供了一個新的路徑為:超音波增加MMP-9的表現是經由活化細胞上3 integrin再活化下游ERK路徑而產生。這些結果將可以幫助我們了解臨床上利用超音波治療骨折時其作用機轉及相關作用，由這些分子機轉的了解將可以幫助藥物的開發及超音波治療時合併藥物的選擇，另外也可提供發展更有效治療超音波的基礎。我們的結果將可以提供醫療儀器廠商發展更有效及更具治療效果超音波的基石，以增進國民的健康
Fracture healing is a complex physiologic process that involves the coordinated participation of several types of cells. Among all the means to influence fracture healing, ultrasound (US) distinguishes itself by being non-invasive and easy to apply. Low-intensity levels US are used to accelerate fracture healing and are considered neither thermal nor destructive. It has been shown that low-intensity US accelerates fracture healing in animal model and clinical studies. In particular, US on osteoblasts in vitro has been demonstrated to increase prostaglandin release, alter collagen synthesis, stimulate collagenase activity and promote bone remodeling. The extracellular matrix (ECM) provides positional and environmental information that is essential for tissue function. The ECMs produced by osteoblasts are complex and consist of several different classes of molecules that may regulate the modeling and remodeling of bone. Although osteoblasts have been implicated only in bone formation, they may cease synthesis of collagen and start secreting neutral proteinases such as collagenase, in response to resorption stimulators. These collagenases may degrade the unmineralized osteoid layer covering bone surfaces, leading to the exposure of the mineralized matrix to osteoclasts. On the other hand, collagenases enable osteoblasts to initiate bone resorption by generating collagen fragments, which in turn activate osteoclasts and start the bone remodeling cycles. Collagenases are matrix metalloproteinases (MMPs) that can initiate the cleavage of collagen fibrils at neutral pH. Consequently, they are considered central to the process of collagen degradation and matrix breakdown. Three collagenases have been described; human osteoblasts express collagenase (MMP-1) and collagenase 3 (MMP-13), whereas rat osteoblasts secrete MMP-13, but do not express MMP-1 (Rajakumar and Quinn, 1996; Varghese et al., 1996). MMP-9 has been proposed to participate actively in situations where rapid and effective remodeling of collagenous ECM is required. In this research plan, we found that US stimulation increased MMP-9 expression. In addition, US also enhanced the expression of 3 integrin. US stimulation increased the phosphorylation of ERK but not Akt. Therefore, our study provided the results that US increased MMP-9 expression through 3 integrin and ERK signaling pathways |
