Histological Profiling of the Human Umbilical Cord: A Potential Alternative Cell Source in Tissue Engineering

Abstract

The embryonic development of the human umbilical cord (hUC) is complex, and different regions can be identified in this structure. The aim of this work is to characterize the hUC at in situ and ex vivo levels to stablish their potential use in vascular regeneration. Human umbilical cords were obtained and histologically prepared for in the situ analysis of four hUC regions (intervascular—IV, perivascular—PV, subaminoblastic—SAM, and Wharton’s jelly—WH), and primary cell cultures of mesenchymal stem cells (hUC-MSC) isolated from each region were obtained. The results confirmed the heterogeneity of the hUC, with the IV and PV zones tending to show the higher in situ expression of several components of the extracellular matrix (collagens, proteoglycans, and glycosaminoglycans), vimentin, and MSC markers (especially CD73), although isolation and ex vivo culture resulted in a homogeneous cell profile. Three vascular markers were positive in situ, especially vWF, followed by CD34 and CD31, and isolation and culture revealed that the region associated with the highest expression of vascular markers was IV, followed by PV. These results confirm the heterogeneity of the hUC and the need for selecting cells from specific regions of the hUC for particular applications in tissue engineering.

Histological characterization of the human scapholunate ligament

“…The results of our histological analysis revealed that the SLIL was heterogeneous, and each subregion had specific histological characteristics. First, our histological analysis using HE (Figure 2) staining confirmed that the dorsal region of the SLIL consisted of a dense ECM with dispersed elongated cells that partially resembles a human ligament, as other authors already demonstrated (Berger, 1996;Berger et al, 1991;Berger & Blair, 1984;Sokolow & Saffar, 2001). However, the threedimensional disposition of the fibers and the cell distribution were different in both subregions of this area (D1 and D2), which supports the idea that the dorsal area consisted of two distinct zones.…”

“…were more similar to hyaline chondrocytes than to fibrochondrocytes, supporting again the possibility that both subregions could be histologically different. Finally, our characterization of the palmar region revealed a structure containing abundant fibers and scattered spindleshaped cells, as previously described (Berger, 1996;Berger et al, 1991;Berger & Blair, 1984). Again, differences in fiber orientation and cell content were detected between P1 and P2, suggesting again that this region could be heterogeneous.…”

“…Then, the analysis of the membranous region revealed the presence of a dense tissue containing cells resembling human chondrocytes that were surrounded by a well-defined pericellular matrix and a capsule, as it is the case of the human cartilage. Although the similitude of the membranous region with human fibrocartilage was previously preconized (Berger, 1996;Berger et al, 1991;Berger & Blair, 1984), we found that the ECM was more dense in M2 than in M1, and both the cells and the ECM in M1…”

“…In addition, Safranin O staining (SO) was used to identify cartilage components. All these methods were performed following previously published standard histochemical methods (Blanco‐Elices et al, 2022; Carriel et al, 2011; García‐García et al, 2021; Sánchez‐Porras et al, 2023). In brief, VHF was performed by incubating deparaffinized tissues in Verhoeff staining solution for 10 min and further differentiation in 2% ferric chloride for 15 sec.…”

Histological characterization of the human scapholunate ligament

“…Non-fibrillar ECM components were evaluated using alcian blue staining (AB) at pH 2.5 for proteoglycans, and periodic acid-Schiff staining (PAS) for glycoproteins. All these methods were performed following previously published standard histochemical methods (Blanco-Elices et al, 2022;V. S. Carriel et al, 2011;García-García et al, 2021;Sánchez-Porras et al, 2023).…”