Department of Morphological Sciences and Teratology, Adelson School of Medicine, Ariel University and Hebrew University Hadassah Medical School, Jerusalem, Israel.
School of Medicine and Dentistry, Departments of Obstetrics/Gynecology, of Pediatrics, of Pathology and of Environmental Medicine, University of Rochester, Rochester, New York, 14642, USA.
Birth Defects Res. 2023 Aug 15;115(14):1243-1254. doi: 10.1002/bdr2.2172. Epub 2023 Mar 22.
During the early phases of embryonic development, the yolk sac serves as an initial placenta in many animal species. While in some, this role subsides around the end of active organogenesis, it continues to have important functions in rodents, alongside the chorio-allantoic placenta. The yolk sac is the initial site of hematopoiesis in many animal species including primates. Cells of epiblastic origin form blood islands that are the forerunners of hematopoietic cells and of the primitive endothelial cells that form the vitelline circulation. The yolk sac is also a major route of embryonic and fetal nutrition apparently as long as it functions. In mammals and especially rodents, macro and micronutrients are absorbed by active pinocytosis into the visceral yolk sac, degraded and the degradation products (i.e., amino acids) are then transferred to the embryo. Interference with the yolk sac function may directly reflect on embryonic growth and development, inducing congenital malformations or in extreme damage, causing embryonic and fetal death. In rodents, many agents were found to damage the yolk sac (i.e., anti-yolk sac antibodies or toxic substances interfering with yolk sac pinocytosis) subsequently affecting the embryo/fetus. Often, the damage to the yolk sac is transient while embryonic damage persists. In humans, decreased yolk sac diameter was associated with diabetic pregnancies and increased diameter was associated with pregnancy loss. In addition, culture of rat yolk sacs in serum obtained from pregnant diabetic women or from women with autoimmune diseases induced severe damage to the visceral yolk sac epithelium and embryonic malformations. It can be concluded that as a result of the crucial role of the yolk sac in the well-being of the early embryo, any damage to its normal function may severely and irreversibly affect further development of the embryo/fetus.
在胚胎发育的早期阶段，卵黄囊在许多动物物种中充当最初的胎盘。虽然在某些动物中，这种作用在活跃的器官发生结束时消失，但它在啮齿动物中继续与绒毛尿囊胎盘一起发挥重要作用。卵黄囊是许多动物物种包括灵长类动物造血的初始部位。外胚层起源的细胞形成血岛，是造血细胞和形成卵黄循环的原始内皮细胞的前身。卵黄囊也是胚胎和胎儿营养的主要途径，显然只要它起作用。在哺乳动物中，特别是在啮齿动物中，宏量和微量营养素通过主动胞饮作用被吸收到内脏卵黄囊中，降解，降解产物（即氨基酸）然后被转移到胚胎中。卵黄囊功能的干扰可能直接影响胚胎的生长和发育，导致先天性畸形，或者在极端损害的情况下，导致胚胎和胎儿死亡。在啮齿动物中，发现许多药物会损害卵黄囊（例如抗卵黄囊抗体或干扰卵黄囊胞饮作用的有毒物质），随后影响胚胎/胎儿。通常，卵黄囊的损伤是短暂的，而胚胎的损伤持续存在。在人类中，卵黄囊直径减小与糖尿病妊娠有关，直径增大与妊娠丢失有关。此外，将大鼠卵黄囊在来自糖尿病孕妇或自身免疫性疾病患者的血清中培养会导致内脏卵黄囊上皮严重损伤和胚胎畸形。可以得出结论，由于卵黄囊对早期胚胎健康的至关重要的作用，任何对其正常功能的损害都可能严重且不可逆转地影响胚胎/胎儿的进一步发育。
