成人的血液幹細胞貯存在骨髓的壁龕區(niche) 內，組成壁龕的支持細胞不但提供血液幹細胞滯留的特殊環境，並且提供外在訊息以維持幹細胞自我新生，大量增生且分化成各種血球細胞的能力。當臨床上施予化學藥物治療或發生發炎反應時，血液幹細胞所貯存的環境會發生改變，而導致血液幹細胞增生、分化成成熟血球細胞且引起部分幹細胞離開壁龕，穿過血管壁而進入血液循環。參與這個血液幹細胞調動(hematopoietic stem cell mobilization) 者包括：幹細胞、壁龕支持細胞、細胞激素、趨化因子、粘滯分子及分解蛋白之間的相互作用，是一個多步驟且必須經由複雜而嚴密調控的過程，近年來對血液幹細胞的調動及壁龕特性的研究有很快速的進展，這篇文章首先介紹血液幹細胞在骨髓內的壁龕，接著再介紹一下目前對血液幹細胞調動機轉的研究。透過對幹細胞調動機轉的瞭解，有助於設計更好的移植方式，增進幹細胞在醫療上的用途。

Human adult hematopoietic stem cells are stored in specific siteswithinbonemarrowtermedstem cell niches. Hematopoietic stem cell niches are formed by supporting cells that provide amicroenvironment for retaining stem cells as well as the signals for stem cells to undergo selfrenewaland produce large numbers of progeny. Once treatments with chemotherapy orinflammatory responses trigger an alarm situation leading to the destruction of the nichemicroenvironment, initiation of hematopoietic stem cell proliferation and differentiation intoimmature and mature blood cells occurs. Some of the hematopoietic stem cells leave the niches,move to the center of the bone cavity, penetrate blood vessels, and enter the blood circulation. Thismobilization is thought to be a coordinated, multiple-step process, which is regulated by theinterplay between chemokines, cytokines, proteolytic enzymes, adhesion molecules, stromal cells,and hematopoietic stem cells. This review is focused on studies which have characterizedhematopoietic stem cell niches and on mechanisms regulating mobilization of hematopoietic stemcells. A better understanding of the mechanisms regulating stem cell mobilization will lead to thedesign of better approaches for stem cells transplantation and the development of new strategiesdirected at regenerative medicine and cancer therapeutics.