Telocytes (TCs) have recently emerged as a peculiar type of stromal cells located in both perivascular and interstitial compartments of multiple anatomical sites in humans, other mammals and vertebrates. Pioneer electron microscopy studies have ultrastructurally defined TCs as "stromal cells with telopodes" (i.e. very long and thin cell processes with a moniliform morphology conferred by the irregular alternation of slender segments and small, bead-like, dilated portions), whereupon it has become apparent that TCs largely correspond to the CD34+ stromal/interstitial cells detectable by immunohistochemical assays. Besides CD34, TCs are also characterized by the expression of platelet-derived growth factor receptor (PDGFR)α. Interestingly, recent works recommended that lymphatic endothelial cell (LEC) markers should be routinely assessed to discriminate with certainty TCs from LECs, because these two cell types may exhibit similar morphological traits, especially when initial lymphatics are sectioned longitudinally and appear as vascular profiles with no obvious lumen. Furthermore, it has been argued that lymphatic microvessels immunostained for the small mucin-type transmembrane glycoprotein podoplanin (PDPN), which is widely used as lymphatic endothelial marker, can be easily misidentified as TCs. Nevertheless, surprisingly these assumptions were not based on double tissue immunostaining for TC and LEC markers. Therefore, the present morphological study was undertaken to precisely investigate the mutual spatial organization and putative relationships of TCs and lymphatic vessels in tissues from different human organs. For this purpose, we carried out a series of double immunofluorescence analyses simultaneously detecting the CD34 or PDGFRα antigen and a marker of LECs, either PDPN or lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1). In the connective tissue compartment of different organs, TCs were CD34+/PDGFRα+/PDPN-/LYVE-1- while LECs were CD34-/PDGFRα-/PDPN+/LYVE-1+, thus representing two definitely distinct, though spatially close, cell entities. The arrangement of telopodes to intimately surround the abluminal side of LECs suggests a possible role of TCs in the regulation of lymphatic capillary functionality, which is worth investigating further.

中文翻译：

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卵母细胞和淋巴管内皮细胞：两个免疫表型不同且在空间上紧密的细胞实体。

最近，在人类，其他哺乳动物和脊椎动物的多个解剖学部位的血管周围和间质隔室中，端粒细胞（TCs）作为一种特殊类型的基质细胞出现了。先锋电子显微镜研究已将TC定义为“具有端状细胞的间质细胞”（即细长的节段和小的，类似珠子的扩张部分的不规则交替所赋予的长而薄的细胞过程，呈moniliform形态），因此它已成为显然，TC在很大程度上对应于可通过免疫组织化学测定法检测到的CD34 +基质/间质细胞。除CD34外，TCs还以血小板衍生的生长因子受体（PDGFR）α的表达为特征。有趣的是 最近的工作建议应常规评估淋巴管内皮细胞（LEC）标记物，以区别于LEC的确定性TC，因为这两种细胞类型可能表现出相似的形态特征，尤其是当初始淋巴管被纵切且呈血管轮廓且无明显管腔时。此外，有人认为，对广泛用作淋巴管内皮标记物的小粘蛋白型跨膜糖蛋白podoplanin（PDPN）进行免疫染色的淋巴微血管很容易被误认为是TC。然而，令人惊讶的是，这些假设并非基于针对TC和LEC标记的双重组织免疫染色。因此，本形态学研究旨在精确研究不同人体器官组织中TC和淋巴管的相互空间组织和推定关系。为此，我们进行了一系列双重免疫荧光分析，同时检测了CD34或PDGFRα抗原以及LEC的标志物，PDPN或淋巴管内皮透明质酸受体1（LYVE-1）。在不同器官的结缔组织区室中，TCs为CD34 + /PDGFRα+ / PDPN- / LYVE-1-，而LECs为CD34- /PDGFRα-/ PDPN + / LYVE-1 +，因此代表了两个绝对不同但空间紧密的细胞实体。端粒紧密包围LEC的管腔侧面的排列表明TC在调节淋巴管毛细血管功能中可能发挥的作用，值得进一步研究。