STUDIES ON INSULIN-LIKE GROWTH-FACTOR-I AND INSULIN IN CHICK LIMB MORPHOGENESIS
STUDIES ON INSULIN-LIKE GROWTH-FACTOR-I AND INSULIN IN CHICK LIMB MORPHOGENESIS
复制标题
DOI：
10.1002/aja.1002020107
复制
发表时间：
1995-01-01
影响因子：
2.5
通讯作者：
KOSHER, RA
中科院分区：
文献类型：
--
作者：
DEALY, CN;KOSHER, RA
顶端外胚层脊(AER)促进发育中肢芽的中胚层细胞的增殖和定向生长，但抑制其分化。胰岛素样生长因子-I(IGF-I)及其受体是由鸡肢芽中胚层细胞对AER的反应而生长出来的，在其生长过程中，特定的胰岛素受体存在于肢芽中。为了研究胰岛素样生长因子-I和胰岛素在肢体发育中的可能作用，我们研究了在有或没有AER和肢体外胚层的情况下，在无血清培养条件下，IGF-I和胰岛素对第25期鸡胚胎翼芽远端末端后部和前部形态发生的影响。缺乏AER的对照后外植体的远端中胚层或全部肢体外胚层停止表达IGF-I mRNA，表现出很少或没有增殖，不能生长，并迅速分化。在缺乏AER或肢体外胚层的后部外植体中，外源IGF-I和胰岛素促进远端中胚层细胞的生长和增殖，并抑制其分化，从而至少在一定程度上模拟了AER对脊下中胚层正常情况下的突起促进和抗分化作用。此外，IGF-I和胰岛素处理的后部外植体表现出高水平的IGF-I mRNA表达，表明IGF-I和胰岛素通过亚脊中胚层维持内源性IGF-I的表达。我们还发现IGF-I和胰岛素可以影响AER的形态和活性。当翼芽顶端的后部在对照培养液中培养时，AER在第4-5天变平，不再表达AER特征的同源异型盒基因MSX2，伴随而来的是亚脊中胚层中细长的软骨成分分化。相反，在外源IGF-I或胰岛素存在的情况下，这种外植体的AER不会变平，继续表达大量的MSX2，亚脊状中胚层保持未分化和增殖。因此，外源性IGF-I和胰岛素维持AER的厚度并维持其MSX2的表达，同时维持正常情况下由增厚的功能性AER对亚脊中胚层所产生的抗分化作用。值得注意的是，我们还发现外源IGF-I和胰岛素诱导肢芽远端薄的前外胚层形成增厚的脊状结构，表达大量的MSX2，同时促进前中胚层的戏剧性生长和增殖，而前中胚层通常几乎不经历突起或增殖。这些研究支持内源性IGF-I和胰岛素可能参与促进肢体中胚层的生长和抑制肢体中胚层的分化以响应AER的假说，也可能参与调节和/或维持至少某些方面的AER活性。(C)1995年Wiley-Liss公司
The apical ectodermal ridge (AER) promotes the proliferation and directed outgrowth of the subridge mesodermal cells of the developing limb bud, while suppressing their differentiation. Insulin-like growth factor-I (IGF-I) and its receptor are expressed by the subridge mesodermal cells of the chick limb bud growing out in response to the AER, and specific insulin receptors are present in the limb bud during its outgrowth. To study the possible roles of IGF-I and insulin in limb outgrowth, we have examined their effects on the morphogenesis of posterior and anterior portions of the distal tip of stage 25 embryonic chick wing buds subjected to organ culture in serum-free medium in the presence or absence of the AER and limb ectoderm. The distal mesoderm of control posterior explants lacking an AER or all limb ectoderm ceases expressing IGF-I mRNA, exhibits little or no proliferation, fails to undergo outgrowth, and rapidly differentiates. Exogenous IGF-I and insulin promote the outgrowth and proliferation and suppress the differentiation of distal mesodermal cells in posterior explants lacking an AER or limb ectoderm, thus mimicking at least to some extent the outgrowth promoting and anti-differentiative effects normally elicited on the subridge mesoderm by the AER. Furthermore, IGF-I and insulin-treated posterior explants exhibit high IGF-I mRNA expression, indicating that IGF-I and insulin maintain the expression of endogenous IGF-I by the subridge mesoderm. We have also found IGF-I and insulin can affect the morphology and activity of the AER. When the posterior portion of the wing bud tip is cultured with the AER intact in control medium, on day 4-5 the AER flattens, ceases expressing high amounts of the AER-characteristic homeobox-containing gene Msx2, and concomitantly an elongated cartilaginous element differentiates in the subridge mesoderm. In contrast, in the presence of exogenous IGF-I or insulin the AER of such explants does not flatten, continues expressing high amounts of Msx2, and the subridge mesoderm remains undifferentiated and proliferative. Thus, exogenous IGF-I and insulin maintain the thickness of the AER and sustain its expression of Msx2, while sustaining the anti-differentiative effect normally elicited on the subridge mesoderm by a thickened functional AER. Notably, we have also found that exogenous IGF-I and insulin induce the formation of a thickened ridge-like structure that expresses high amounts of Msx2 from the normally thin distal anterior ectoderm of the limb bud, while promoting dramatic outgrowth and proliferation of the anterior mesoderm, which normally undergoes little outgrowth or proliferation. These studies provide support for the hypothesis that endogenous IGF-I and insulin may be involved in promoting the outgrowth and suppressing the differentiation of limb mesoderm in response to the AER, and also in regulating and/or maintaining at least some aspects of AER activity. (C) 1995 Wiley-Liss, Inc.