Influence of shear force on ex vivo expansion of hematopoietic model cells in a stirred tank bioreactor

To evaluate shear stress influence on ex vivo expansion of hematopoietic cell lineages for clinical application, in this study, human pro-monocytic cell (namely U937 cell line) was selected as a hematopoietic stem cell (HSC) model and cultured in suspension mode at two different agitation rates (50, 100 rpm) in the stirred bioreactor. At the agitation rate of 50 rpm, the cells achieved higher expansion folds (27.4 fold) with minimal morphological changes as well as apoptotic cell death, while at 100 rpm the expansion fold decreased after 5-day of culture in suspension culture in comparison with static culture and reached 24.5 fold at the end of the culture. The results of glucose consumption and lactate production were also in agreement with the data of fold expansion and indicated the preference of culture in the stirred bioreactor when agitated at 50 rpm. This study indicated the stirred bioreactor system with an agitation rate of 50 rpm and surface aeration may be used as a potential dynamic culture system for clinical applications of hematopoietic cell lineage. The current experiments shed data related to the effect of shear stress on human U937 cells, as a hematopoietic cell model, to set a protocol for expansion of HSCs for biomedical applications.

Influence of gelatin modification on enzymatically-gellable pectin-gelatin hydrogel properties for soft tissue engineering applications

Injectable in situ-forming hydrogels appears to be a promising approach for tissue engineering applications. In this study, the effect of phenol moiety (Ph) addition to gelatin in enzymatically-gellable modified pectin hydrogel (Pec-Ph) was studied. Addition of gelatin-Ph to Pec-Ph (Pec-Ph/Gel-Ph) altered the physical properties of Pec-Ph-based hydrogels as compared to unmodified gelatin (Pec-Ph/Gel) addition. Swelling ratio and degradation rates of the Pec-Ph/Gel-Ph hydrogel decreased 35% and 50%, respectively, and the elasticity of Pec-Ph/Gel-Ph hydrogel was higher than the Pec-Ph/Gel hydrogels. Scanning electron microscopy images showed that the existence of phenolic groups in gelatin decreased the pore size of Pec-Ph/Gel-Ph hydrogels. Culture of chondrocyte cells in the Pec-Ph/Gel-Ph hydrogels showed more metabolic activity (4×) during a 14-day culture period. Hydrogels subcutaneously implanted in rats could also be identified readily without complete absorption and signs of toxicity or any untoward reactions after 1 month. The work showed the potential of Pec-Ph/Gel-Ph hydrogels as a promising in situ injectable hydrogel for soft tissue engineering applications.

Alginate-chitosan core-shell microcapsule cultures of hepatic cells in a small scale stirred bioreactor: impact of shear forces and microcapsule core composition

A small scale stirred bioreactor was designed and the effect of different agitation rates (30, 60 and 100 rpm) was investigated on HepG2 cells cultured in alginate-chitosan (AC) core-shell microcapsule in terms of the cell proliferation and liver-specific function. The microencapsulated hepatic cells could proliferate well when they were cultured for 10 days at 30 rpm while the cell-laden microcapsules showed no cell proliferation at 100 rpm in the bioreactor system. Albumin production rate, as an important liver function, increased also 1.8- and 1.5- fold under stirring rate of 30 rpm compared to the static culture and 60 rpm of agitation, respectively. Moreover, In comparison with the static culture, about 1.5-fold increment in urea production was observed at 30 rpm. Similarly, the highest expressions of albumin and P450 genes were found at 30 rpm stirring rate, which were 4.9- and 19.2-fold of the static culture. Addition of collagen to the microcapsule core composition (ACol/C) could improve the cell proliferation and functionality at 60 rpm in comparison with the cell-laden microcapsules without collagen. The study demonstrated the hepatic cell-laden ACol/C microcapsule hydrogel cultured in the small scale stirred bioreactor at low mixing rate has a great potential for mass production of the hepatic cells while maintaining liver-specific functions.