上世纪 90年代以来，干细胞移植技术得到飞速发展。研究人员利用干细胞形成特定组织器官用于移植。胚胎干细胞能够形成各种各样的身体组织。很多研究人员相信利用这种细胞使组织再生，从而能够起到治疗多种疾病的作用。用胚胎干细胞修复动物组织器官的成功实例也时有报道。
Memorial Sloan-kettering癌症中心的研究人员，Diego Fraidenraich和同事，在10月8日的Science上，公布了他们的一项新研究的结果，胚胎干细胞还能够分泌出治愈性的分子，这些分泌物足以逆转小鼠的致死性的先天缺陷。这个新研究则揭示出胚胎干细胞的另外的一个功能。
在这项新的研究中，研究人员把胚胎干细胞注射到有致命心脏缺陷的小鼠胚胎（这些胚胎必定会出现严重的心脏缺陷，并且使得小鼠可能会在子宫中死亡）中后，但出乎意料的是，干细胞分泌的信号分子使小鼠心脏的缺陷没有发展，有一半的新生小鼠有一个健康的心脏。同时，将干细胞注射给没有妊娠的母鼠，部分地改正了它们后代的遗传性心脏缺陷，避免了胚胎的死亡。尽管很少有干细胞真的长成了健康的心脏组织，但研究人员发现干细胞能够分泌出特殊的分子，长程信号分子IGF1和短程信号分子WNT5a，这些分子在改正这些缺陷和挽救小鼠胚胎上起了作用。研究的领导者Fraidenraich将这些分泌物叫做“拯救因子”。当科学家把干细胞注射到成熟的母鼠身上时，来自干细胞的IGF1 似乎能穿过胎盘到达小鼠胚胎，但是WNT5a不能。当把干细胞直接注射给早期的小鼠胚胎时，两种信号分子都到达了有缺陷的心脏组织。
这个新发现拓宽了胚胎干细胞治疗疾病的方式。许多干细胞研究专家对这个发现也给予了高度的评价。胚胎干细胞分泌的因子也许有朝一日能用来治疗成年人的心脏病。
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Rescue of cardiac malformations in mutant mouse embryos by ES cells. (A) Embryos lacking the Id1, Id2, and Id3 genes display multiple cardiac abnormalities and die around embryonic day 13.5. The complex cardiac phenotype includes ventricular septal defects (VSD), thinning of the myocardial wall, outflow tract atresia, and endocardial cushion defects. Additionally, these hearts display reduced cell proliferation by disorganized sheets of myocytes and a discontinuous endocardial lining. (B) Injection of a small number of wild-type (wt) ES cells carrying a lacZ marker into Id mutant blastocysts resulted in about 20% chimerism of heart tissue and complete rescue of the Id mutant phenotype. Intraperitoneal injection of wild-type ES cells into female mice (Id1-/-, Id3+/-) prior to conception that were mated with males (Id1-/-, Id3+/-) partially rescued the cardiac phenotype of Id mutant embryos without incorporation of ES cells into the fetal heart tissue. Short- and long-range signals emanating from the ES cells reversed the myocardial defect in a non-cell autonomous manner. Two signaling molecules secreted by ES cells--Wnt5a, a locally secreted factor, and IGF-1, a bloodstream factor that promotes myocyte proliferation--were identified as potential candidates involved in the rescue process.
Fig. 1. Cardiac defects in Id KO embryos are rescued by injection of 15 ES cells. [(A) to (O)] A WT (A, D, G, J, and M), Id1–/–Id3–/– (B, E, H, K, and N), or Id1–/–Id3–/–:R26 (C, F, I, L, and O) E11.5 embryo was X-Gal stained [(A) to (C)] or transversely sectioned at the ventricle [(D) to (L)] or OT level [(M) to (O)]. (D) to (F) are magnified by 50x and (M) to (O) are magnified by 80x, desmin immunodetection. (G) to (I) show CD31 immunodetection at 200x. (J) to (L) show BrdU immunodetection at 100x. The inset in (L) shows the percentage of BrdU from (J) to (L). [(P) and (Q)] A WT (P), ROSA+/– [(P), inset], or Id1–/–Id3–/–:R26 (Q) E17.5 embryo was X-Gal and eosin stained (magnified by 50x). [(R) to (Z2)] A WT (R and S), WT:R26 (V and W), Id1–/– Id2+/– Id3–/–:R26 (T and U), or Id1–/–Id3–/–:R26 (X and Y) P7 [(R) to (U)] or P120 [(V) to (Z2)] heart was sectioned (dashed lines), X-Gal and eosin stained [(S) and (U), 25x; (W) and (Y), 15x) or CD31 immunostained [(Z1) and (Z2), 50x). He, heart; FB, forebrain; VS, ventricular septum; Tr, trabeculae; End, endocardium; Myo, myocardium; Th, thymus; LV, left ventricle; RV, right ventricle; blue arrow, outflow tract EC; KO, Id KO; red bar in (J) to (L), myocardial wall thickness; red bar in (M) to (O), luminal thickness; black arrowhead in (Z1) and (Z2), CD31+ cells. Scale bar, 500 µm [(A) to (C)]; 2 mm [(R), (T), (V), and (X)].
Fig. 2. R26 cells rescue Id1–/–Id3–/– cells non–cell autonomously. (A to C and I to K) A WT [(A) and (I)], Id1–/–Id3–/– [(B) and (J)], or Id1–/–Id3–/–:R26 [(C) and (K)] E11.5 embryo was subjected to ISH for Stra13 (100x). (D) Adjacent section of (C), X-Gal stained. (L) An Id1–/–Id3–/–:R26 E14.5 embryo was X-Gal and CD31 immunostained (100x). [(E) to (G)] A WT (E), Id1–/–Id3+/– (F), or Id1–/–Id2+/–Id3–/–:R26 (G) P7 heart was subjected to ISH for skMLC (50x). (H) Adjacent section of (G), X-Gal stained. [(E), inset] Northern blot from a WT or Id1–/–Id3+/– E13.5 heart probed for skMLC. Insets in (I) to (K) show bright field. V, ventricle; At, atrium; GE, ganglionic eminence; black arrowhead in (J) inset, hemorrhage; white arrowheads (L), CD31+ cells.
Fig. 3. Conditioned medium from Id KO:R26 epicardial cells (epiCM) corrects myocardial proliferation defects in Id KO hearts. (A to C) A WT, Id1–/–Id3+/–, or Id1–/–Id3+/–:R26 E17.5 embryo was sectioned at heart level and Ki67 immunostained. (D) Percentage of Ki67+ cells of (A) to (C). Error bars show mean + SD. (E to G and I to K) An Id1–/–Id3+/– E17.5 [(E) to (G)] or Id1–/–Id3–/– E12.5 [(I) to (K)] heart was cultured with BrdU and WT [(E) and (I)], Id1–/–Id3+/– [(F) and (J)], or Id1–/–Id3+/–:R26 [(G) and (K)] epiCM, sectioned, and Ki67 [(E) to (G)] or BrdU [(E) to (G), insets] immunostained or subjected to ISH for skMLC [(I) to (K)]. (H) Percentage of Ki67+ cells of (E) to (G) and control with no epiCM. Error bars show mean + SD. (L) RT-PCR [cardiac actin (ca), epicardin (epi), and pecam (pec)] of Id1–/–Id3+/–:R26 epicardial-derived cells (lane 1) or E13.5 heart (lane 2). [(L), inset] Id1–/–Id3+/–:R26 epicardial-derived cells were X-Gal stained. KO, Id1–/–Id3+/–. Magnification: 630x in (A) to (C) and (E) to (G); 400x in (I) to (K). CZ, myocardial compact zone; M, markers.
Fig. 4. Id1/Id3 double KO pups are born from mice intraperitoneally injected with ES cells or IGF-1. (A to C) An Id1–/–Id3–/– E11.5 embryo from an ES-injected female was sectioned at heart [(A) to (C)] or brain [(B), inset] level and Desmin [(A), 50x], CD31 [(B), 200x and (B), inset, 100x] or BrdU [(C), 100x] immunostained. [(D) to (L)] A WT (D to F), an Id1–/–Id3–/– from an ES-injected female (G to I), or an Id1–/–Id3–/– from an IGF-1–injected female (J to L) P1 heart was transversely sectioned and stained with X-Gal and eosin [(D), (G), and (J), 25x], CD31 [(E), (H), and (K), 200x], or Ki67 [(F), (I), and (L), 50x]. [(F) and (I), insets] A WT [(F), inset, 400x] or an Id1–/–Id3+/– E18.5 heart from a noninjected or from an R26 injected female [(I), insets, 400x] was sectioned and Ki67 immunostained. KO(R26), Id KO embryos (pups) from R26-injected females; KO (IGF-1), Id KO pups from IGF-1–injected females; End, endocardium; Myo, myocardium; RV, right ventricle; LV, left ventricle; VS, ventricular septum; GE, ganglionic eminence; arrowhead (A), VS defect; red bar (C), thickness of compact myocardium; white arrowhead (G), VS defect; black arrowheads (E), CD31+ endocardial cells; white arrowheads (E), CD31+ endothelial cells; white arrowheads [(H) and (K)], disorganized
Fig. 5. IGF-1 is down-regulated in Id1/Id3 KO embryos. [(A) to (F)] A WT (A, C, and E) or an Id1–/–Id3–/– (B, D, and F) E11.5 heart was sagittally sectioned and desmin immunostained [(A) and (B)] or IGF-1 in situ stained [(C) to (F)]. [(E) and (F), insets] Desmin immunostaining of (E) and (F). (A) to (D), 100x; (E) and (F), 200x. (G) RNA from a WT or an Id1–/–Id3–/– E11.5 liver was hybridized with IGF-1, IGFBP4, or glyceraldehyde-3-phosphate dehydrogenase (GAPDH). At, atrium; Ve, ventricle; end, endocardium; epi, epicardium. White arrowheads [(C) and (D)], EC+ cells; gray arrowheads [(C) and (D)], endocardial+ cells; gray arrowheads [(E) and (F)], end+ cells; blue arrowheads [(E) and (F)], epi+ cells.
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http://intl.sciencemag.org/cgi/content/full/306/5694/239
http://www.eurekalert.org/pub_releases/2004-10/mscc-esc100404.php
