Modulation of mesenchymal stromal cell characteristics by microcarrier culture in bioreactors

Mesenchymal stromal cells (MSCs) are promising candidates for cell therapy. Their therapeutic use requires extensive expansion to obtain a sufficiently high number of cells for clinical applications. State-of-the-art expansion systems, that is, primarily culture flask-based systems, are limited regarding scale-up, automation, and reproducibility. To overcome this bottleneck, microcarrier (MC)-based expansion processes have been developed. For the first time, MSCs from the perinatal sources umbilical cord (UC) and amniotic membrane (AM) were expanded on MCs. This study focuses on the comparison of flask- and Cytodex 1 MC-expanded MSCs by evaluating the influence of the expansion process on biological MSC characteristics. Furthermore, we tested the hypothesis to obtain more homogeneous MSC preparations by expanding cells on MCs in controlled large-scale bioreactors. MSCs were extensively characterized determining morphology, cell growth, surface marker expression, and functional properties such as differentiation capacity, secretion of paracrine factors, and gene expression. Based on their gene expression profile MSCs from different donors and sources clearly clustered in distinct groups solely depending on the expansion process-MC or flask culture. MC- and flask-expanded MSCs significantly differed from each other regarding surface markers and both paracrine factors and gene expression profiles. Furthermore, based on gene expression analysis, MC cultivation of MSCs in controlled bioreactor systems resulted in less heterogeneity between cells from different donors. In conclusion, MC-based MSC expansion in controlled bioreactors has the potential to reliably produce MSCs with altered characteristics and functions as compared to flask-expanded MSCs. These findings may be useful for the generation of MSCs with tailored properties for clinical applications.

Mesenchymal stromal cell characteristics vary depending on their origin

Mesenchymal stromal cells (MSCs) are rare progenitor cells that can be isolated from various tissues. They exhibit multilineage differentiation potential, support regenerative processes, and interact with various immune cells. Therefore, MSCs represent a promising tool for regenerative medicine. However, source-dependent and donor-dependent differences of MSC properties, including implications on their clinical application are still largely unknown. We evaluated MSCs derived from perinatal tissues umbilical cord (UC) and amniotic membrane (AM) in comparison to adult MSCs from bone marrow (BM), which were used as gold standard. We found genetic background-independent differences between MSCs from UC and AM. While AM- and UC-MSCs were closer to each other than to BM-MSCs, they also exhibited differences between each other. AM-MSCs from different donors but not UC-MSCs displayed high interdonor variability. In addition, we show that although all MSCs expressed similar surface markers, MSC populations from UC and AM showed differential profiles of gene expression and paracrine factor secretion to BM-derived MSCs. Notably, pathway analysis of gene expression data revealed intriguing differences between MSCs suggesting that MSCs from UC and AM possess in general a higher potential of immunomodulatory capacity, whereas BM-MSCs showed a higher potential of supporting regenerative processes as exemplified by neuronal differentiation and development. These differences between perinatal and BM-derived MSCs may be relevant for clinical applications.

Monocyte migration through the alveolar epithelial barrier: adhesion molecule mechanisms and impact of chemokines

Alveolar monocyte influx requires adherence and transmigration through the vascular endothelium, extracellular matrix, and alveolar epithelium. For investigating the monocyte migratory process across the epithelial barrier, we employed both the A549 cell line and isolated human alveolar epithelial cells. Under baseline conditions, spontaneous bidirectional transepithelial monocyte migration was noted, which was dose-dependently increased in the presence of the monocyte chemoattractant protein-1. TNF-alpha stimulation of the alveolar epithelium provoked the polarized apical secretion of monocyte chemoattractant protein-1 and RANTES and up-regulation of ICAM-1 and VCAM-1 expression, accompanied by markedly enhanced transepithelial monocyte traffic in the basal-to-apical direction. Multiple adhesive interactions were noted to contribute to the enhanced monocyte traffic across the TNF-alpha-stimulated alveolar epithelium: these included the beta 2 integrins CD11a, CD11b, CD11c/CD18, the beta 1 integrins very late Ag (VLA)-4, -5, and -6, and the integrin-associated protein CD47 on monocytes, as well as ICAM-1, VCAM-1, CD47, and matrix components on the epithelial side. In contrast, spontaneous monocyte migration through unstimulated epithelium depended predominantly on CD11b/CD18 and CD47, with some additional contribution of VLA-4, -5, and -6. In summary, unlike transendothelial monocyte traffic, for which beta 1 and beta 2 integrins are alternative mechanisms, monocyte migration across the alveolar epithelium largely depends on CD11b/CD18 and CD47 but required the additional engagement of the beta 1 integrins for optimal migration. In response to inflammatory challenge, the alveolar epithelium orchestrates enhanced monocyte traffic to the apical side by polarized chemokine secretion and up-regulation of ICAM-1 and VCAM-1.

Patch test reactions at D4, D5 and D6

In this retrospective study, patch test reactions in 3 groups of patients were analysed, in order to obtain information on the best day for the 2nd patch-test reading after day 2 (D2), on the usefulness of additional readings after D3, and on the dependence of patch-test reactions at D4, D5, or D6 on allergen and/or patient characteristics. In the years 1990 to 1995, patch tests were routinely read at D3 and D4 in 1096 patients, at D3 and D5 in 1243 patients, and at D3 and D6 in 1136 patients. In all of the 3 groups, significantly more positive reactions diminished than appeared de novo from D3 to the later reading. Virtually identical results were observed in subgroups of patients formed by sex, age or atopy. However, men might possibly react more slowly than women on patch testing, showing more increasing than diminishing reactions in the D3/D4- and the D3/D5-comparison. Reactions to individual allergens showed wide differences in this connection. Neomycin sulfate, cobalt salts, and p-phenylenediamine can be characterized as slow allergens, with more reactions increasing than diminishing from D3 to the later readings. With fragrance mix and balsam of Peru, the opposite pattern occurred. In all subgroups of patients, and with most allergens, the gain in positive reactions was biggest when an additional reading was performed at D5. We conclude that for a single 2nd patch test reading after D2, D3 is the best day, and especially better than D4. If a 3rd reading is performed, it should be done at D5 to get the maximum information out of patch testing. However, this extends the test procedure to at least 1 day of the weekend.