TY  - JOUR
A1  - Wagner, Nicole
A1  - Mott, Kristina
A1  - Upcin, Berin
A1  - Stegner, David
A1  - Schulze, Harald
A1  - Ergün, Süleyman
T1  - CXCL12-abundant reticular (CAR) cells direct megakaryocyte protrusions across the bone marrow sinusoid wall
JF  - Cells
N2  - Megakaryocytes (MKs) release platelets into the lumen of bone marrow (BM) sinusoids while remaining to reside within the BM. The morphogenetic events of this complex process are still not fully understood. We combined confocal laser scanning microscopy with transmission and serial block-face scanning electron microscopy followed by 3D-reconstruction on mouse BM tissue sections. These analyses revealed that MKs in close vicinity to BM sinusoid (BMS) wall first induce the lateral retraction of CXCL12-abundant reticular (CAR) cells (CAR), followed by basal lamina (BL) degradation enabling direct MK-sinusoidal endothelial cells (SECs) interaction. Subsequently, an endothelial engulfment starts that contains a large MK protrusion. Then, MK protrusions penetrate the SEC, transmigrate into the BMS lumen and form proplatelets that are in direct contact to the SEC surface. Furthermore, such processes are induced on several sites, as observed by 3D reconstructions. Our data demonstrate that MKs in interaction with CAR-cells actively induce BMS wall alterations, including CAR-cell retraction, BL degradation, and SEC engulfment containing a large MK protrusion. This results in SEC penetration enabling the migration of MK protrusion into the BMS lumen where proplatelets that are adherent to the luminal SEC surface are formed and contribute to platelet release into the blood circulation.
KW  - megakaryocytes
KW  - microvasculature
KW  - CXCL12-abundant reticular (CAR)-cells
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234180
SN  - 2073-4409
VL  - 10
IS  - 4
ER  - 
TY  - JOUR
A1  - Kwok, Chee Keong
A1  - Ueda, Yuichiro
A1  - Kadari, Asifiqbal
A1  - Günther, Katharina
A1  - Ergün, Süleyman
A1  - Heron, Antoine
A1  - Schnitzler, Aletta C.
A1  - Rook, Martha
A1  - Edenhofer, Frank
T1  - Scalable stirred suspension culture for the generation of billions of human induced pluripotent stem cells using single-use bioreactors
JF  - Journal of Tissue Engineering and Regenerative Medicine
N2  - The production of human induced pluripotent stem cells (hiPSCs) in quantities that are relevant for cell-based therapies and cell-loaded implants through standard adherent culture is hardly achievable and lacks process scalability. A promising approach to overcoming these hurdles is the culture of hiPSCs in suspension. In this study, stirred suspension culture vessels were investigated for their suitability in the expansion of two hiPSC lines inoculated as a single cell suspension, with a free scalability between volumes of 50 and 2400 ml. The simple and robust two-step process reported here first generates hiPSC aggregates of 324 ± 71 μm diameter in 7 days in 125 ml spinner flasks (100 ml volume). These are subsequently dissociated into a single cell suspension for inoculation in 3000 ml bioreactors (1000 ml volume), finally yielding hiPSC aggregates of 198 ± 58 μm after 7 additional days. In both spinner flasks and bioreactors, hiPSCs can be cultured as aggregates for more than 40 days in suspension, maintain an undifferentiated state as confirmed by the expression of pluripotency markers TRA-1-60, TRA-1-81, SSEA-4, OCT4, and SOX2, can differentiate into cells of all three germ layers, and can be directed to differentiate into specific lineages such as cardiomyocytes. Up to a 16-fold increase in hiPSC quantity at the 100 ml volume was achieved, corresponding to a fold increase per day of 2.28; at the 1000 ml scale, an additional 10-fold increase was achieved. Taken together, 16 × 106 hiPSCs were expanded into 2 × 109 hiPSCs in 14 days for a fold increase per day of 8.93. This quantity of hiPSCs readily meets the requirements of cell-based therapies and brings their clinical potential closer to fruition.
KW  - bioprocessing
KW  - human pluripotent stem cells
KW  - process optimization
KW  - single-use bioreactors
KW  - stirred suspension culture
KW  - scalable culture system
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234545
VL  - 12
ER  -