Rosa Irene, Marini Mirca, Sgambati Eleonora, Ibba-Manneschi Lidia, Manetti Mirko
Department of Experimental and Clinical Medicine, Section of Anatomy and Histology, University of Florence, Largo Brambilla 3, 50134, Florence, Italy.
Department of Biosciences and Territory, University of Molise, Contrada Fonte Lappone, Pesche (Isernia), 86090, Italy.
Acta Histochem. 2020 Apr;122(3):151530. doi: 10.1016/j.acthis.2020.151530. Epub 2020 Feb 27.
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.
最近，端粒细胞（TCs）作为一种特殊类型的基质细胞出现，位于人类、其他哺乳动物和脊椎动物多个解剖部位的血管周围和间质区域。开创性的电子显微镜研究在超微结构上将端粒细胞定义为“具有端粒的基质细胞”（即非常长且细的细胞突起，具有由细长段和小的、珠状、扩张部分不规则交替赋予的念珠状形态），由此很明显，端粒细胞在很大程度上对应于通过免疫组织化学检测可检测到的CD34 + 基质/间质细胞。除了CD34，端粒细胞还以血小板衍生生长因子受体（PDGFR）α的表达为特征。有趣的是，最近的研究建议应常规评估淋巴管内皮细胞（LEC）标记物，以确定地将端粒细胞与淋巴管内皮细胞区分开来，因为这两种细胞类型可能表现出相似的形态特征，特别是当初始淋巴管纵向切片并呈现为无明显管腔的血管轮廓时。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足板蛋白（PDPN）进行免疫染色的淋巴管微血管很容易被误识别为端粒细胞。然而，令人惊讶的是，这些假设并非基于对端粒细胞和淋巴管内皮细胞标记物的双重组织免疫染色。因此，进行本形态学研究以精确研究不同人体器官组织中端粒细胞与淋巴管的相互空间组织和假定关系。为此，我们进行了一系列双重免疫荧光分析，同时检测CD34或PDGFRα抗原以及淋巴管内皮细胞标记物，即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域中，端粒细胞为CD34 + / PDGFRα + / PDPN - / LYVE - 1 - ，而淋巴管内皮细胞为CD34 - / PDGFRα - / PDPN + / LYVE - 1 + ，因此代表两个明显不同但在空间上相邻的细胞实体。端粒紧密围绕淋巴管内皮细胞腔外侧的排列表明端粒细胞在调节毛细淋巴管功能方面可能发挥作用，这值得进一步研究。
