USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX, USA.
Food Science and Nutrition Department, National Research Centre, Dokki, Giza, Egypt.
Physiol Rep. 2020 Nov;8(21):e14565. doi: 10.14814/phy2.14565.
Age-dependent changes in the intestinal gene expression of enzymes involved in the metabolism of citrulline and arginine are well characterized. Enteroids, a novel ex-vivo model that recreates the three-dimensional structure of the intestinal crypt-villus unit, have shown to replicate molecular and physiological profiles of the intestinal segment from where they originated ("location memory").
The present study tested the hypothesis that enteroids recapitulate the developmental changes observed in vivo regarding citrulline production in pigs ("developmental memory").
Preterm (10- and 5-d preterm) and term pigs at birth, together with 7- and 35-d-old pigs were studied. Gene expression was measured in jejunal samples and in enteroids derived from this segment. Whole body citrulline production was measured by isotope dilution and enteroid citrulline production by accumulation in the media.
With the exception of arginase I and inducible nitric oxide synthase, all the genes investigated expressed in jejunum were expressed by enteroids. In the jejunum, established markers of development (lactase and sucrase-isomaltase), as well as genes that code for enzymes involved in the production and utilization of citrulline and arginine, underwent the ontogenic changes described in the literature. However, enteroid expression of these genes, as well as citrulline production, failed to recapitulate the changes observed in vivo.
Under culture conditions used in our study, enteroids derived from jejunal crypts of pigs at different ages failed to replicate the gene expression observed in whole tissue and whole body citrulline production. Additional extracellular cues may be needed to reproduce the age-dependent phenotype.
参与瓜氨酸和精氨酸代谢的肠道基因表达随年龄的变化特征已有充分研究。肠类器官是一种新型的体外模型，可重现肠道隐窝-绒毛单位的三维结构，已证明其可复制其起源部位的肠道段的分子和生理特征（“位置记忆”）。
本研究检验了肠类器官是否可重现猪体内观察到的瓜氨酸产生的发育变化（“发育记忆”）的假设。
研究了 10-5 日龄早产和足月出生以及 7-35 日龄的猪。在空肠样本和来源于该段的肠类器官中测量基因表达。通过同位素稀释测量全身瓜氨酸的产生，通过在培养基中积累测量肠类器官的瓜氨酸产生。
除了精氨酸酶 I 和诱导型一氧化氮合酶外，空肠中表达的所有研究基因均在肠类器官中表达。在空肠中，已确立的发育标志物（乳糖酶和蔗糖酶-异麦芽糖酶）以及编码参与瓜氨酸和精氨酸产生和利用的酶的基因经历了文献中描述的个体发生变化。然而，这些基因的肠类器官表达以及瓜氨酸的产生未能重现体内观察到的变化。
在我们研究中使用的培养条件下，源自不同年龄猪空肠隐窝的肠类器官未能复制整个组织和全身瓜氨酸产生中观察到的基因表达。可能需要额外的细胞外线索来重现年龄相关的表型。
