利用動物模式探討水解磷酸脂受器3(Lpar3)調控紅血球及血小板分化之研究

Abstract

造血生成主要是由血球幹胞接受複雜的訊息傳遞誘導進而分化各式各樣的血球以支持個體存活。水解磷酸脂 (LPA) 是一個細胞外脂質類之調控者，主要透過活化G蛋白偶聯受體調控許多生物體內的訊息傳導，其中包括循環系統的分化。先前文獻中發現在幹細胞內的LPA會透過活化水解磷酸脂受器3 (Lpar3) 促使紅血球的生成。因此我們想利用藥物治療進一步探討Lpar3對於活體造血的影響。 在我們的研究中發現將斑馬魚浸泡在 Lpar1/3 抑制劑 Ki16425 中確實會抑制血紅素的表現量。接著進一步利用 morpholino 單一抑制斑馬魚內生性Lpar3的表現以及浸泡 Lpar3 促進劑 OMPT ，藉由時間點的實驗證明 Lpar3 主要是調控由幹細胞分支出來的造血生成而非早期支持胚胎快速生長的血液生成。另一方面我們將OMPT注入小鼠中，結果發現 OMPT 不但會使血液中的血球數增加，骨髓內的血紅素表現量也會上升。 此外由於紅血球和凝血細胞來自同一個前驅細胞，我們藉由凝血細胞表面上的 CD41 分子表現觀察到當Lpar3受到抑制時，凝血細胞表現上升，另一方面促使Lpar3 活化的 OMPT 則會抑制凝血細胞生成。因此我們認為Lpar3對於紅血球和凝血細胞的生成扮演很重要的角色。

Hematopoiesis is a dynamic process in which hematopoietic stem cells differentiate into specific mature blood cell lineages. Lysophosphatidic acid (LPA), a lipid growth factor with multiple biological functions, has been suggested to be an important regulator in the differentiation and development of the circulatory system. Our previous study demonstrated that LPA stimulates human hematopoietic stem cells (hHSC) to differentiate into erythrocytes by activating Lpa receptor 3 (Lpar3) in vitro. Thus, we aimed to further confirm the roles of Lpar3 in the hematopoietic determination by pharmacological treatment in vivo. Using zebrafish as a model, we found that morpholino (MO)-mediated knockdown of zLpar3 inhibited the production of hemoglobin. In addition, the results of pharmacological experiments showed that activation of Lpar3 can enhance erythropoiesis during definitive hematopoiesis. Furthermore, the effect of Lpar3 on the regulation of hematopoiesis was confirmed in mammalian systems. Daily injection of the Lpar3 agonist OMPT was applied in BALB/C mice and blood samples were collected and analyzed. The results show that the number of blood cells collected from the heart ventricle and the expression of hemoglobin in bone marrow were increased after OMPT treatment. Since erythrocytes and thrombocytes are derived from common progenitors, we also investigated whether Lpar3 regulates thrombocyte development. Interestingly, the data showed the expression levels of CD41 (αIIb, glycoprotein IIb [GPIIb]), a marker for thrombocyte, could be inhibited by activating Lpar3. In summary, we demonstrated that Lpar3 is an important regulator for the erythropoiesis and thrombocytopoiesis processes of HSC.