[Study on the ex vivo expansion characteristics of umbilical cord blood CD34+ cells and mononuclear cells].

OBJECTIVE: To explore the ex vivo expansion characteristics of selected CD(34)(+) cells and mononuclear cells (MNC). METHODS: CD(34)(+) cells were isolated from umbilical cord blood MNC by MiniMACS system, expanded under the same conditions as that for MNC. The effects of re-isolation and the MNC supernatant (MNC-SN) on the selected CD(34)(+) cells were investigated. And the CD(34)(-) cells of MNC were cultured ex vivo. RESULTS: In the culture of selected CD(34)(+) cells, both the colony density and the proportion of the CD(34)(+) cells declined continuously with the culturing, although they presented a high proliferation potential. However, in the culture of the MNC, from day 0 to day 7, the colony density and the proportion of CD(34)(+) cells were increased from 412 +/- 167/10(5) cells and (1.12 +/- 0.42)% to 1 162 +/- 566/10(5) cells and (4.17 +/- 1.44)%, respectively. It was found that both the total cells and the CD(34)(+) cells restored expansion potential by re-isolating. CD(34)(-) cells of MNC had the ability to form colony and could transform to CD(34)(+) cells. MNC-SN can promote colony forming ability and lead to CD(34)(+) cells differentiation at the same time. CONCLUSIONS: In ex vivo culture, selected CD(34)(+) cells presented a high proliferation and differentiation potentials, and the CD(34)(-) cells produced during the cultivation had inhibition effect on CD(34)(+) cells expansion. CD(34)(-) cell population from cord blood MNC contained hematopoietic stem/progenitor cells and the cytokines secreted by CD(34)(-) cells could induce CD(34)(+) cells to more mature colony-forming cells.

[Effects of different cooling rates on cryopreservation of hematopoietic stem cells from cord blood].

Clinical evidence of hematopoietic restoration with umbilical cord blood (UCB) grafts indicates the UCB can be a useful source of hematopoietic stem cells for routine bone marrow reconstitution. Considering (10 +/- 5) x 10(8) nucleared cells per cord blood unit, there is a potential limitation for the use of cord blood in adults, which, however, can be overcome by ex vivo expansion of cells. A prerequisite for expansion is the significantly higher recovery of MNC, CD34+ cells and colony-forming cells (CFC) by thawing cryopreserved MNC. Cooling rate always acts as a critical factor that can affect the recovery of cells. Although the rate of - 1 degrees C/min is adopted in most of the cryopreservations, no data has been reported about the detailed effects of different cooling rates. The aim of the study was to reveal the different effects of cooling rates on cryopreservation of hematopoietic stem cells from cord blood. UCB samples were collected, and cryopreserved as mononuclear cells (MNC) with different cooling rates of - 0.5 degrees C/min, - 1 degrees C/min, - 5 degrees C/min, and the recovery and viability of MNC and CD34+ cells, the clonogenic capacity and the ex vivo expansion potential of UCB progenitor cells were evaluated after thawing. With - 1 degrees C/min cooling rate, the recovery of MNC reached 93.3% +/- 1.8% , viability 95.0% +/- 3.9% , recovery of CD34+ cells 80.0% +/- 17.9% , and clonogenic recovery were 87.1% +/- 5.5%, 88.5% +/- 8.9%, 86.2% +/- 7.4% for BFU-E CFU-GM CFU-MK, respectively. After 14 days of liquid culture, no significant difference was detected in CFC expansion between fresh and cryopreserved MNC cells with - 1 degrees C/min cooling rate, but this was not the case with - 0.5 degreesC/min and - 5 degrees C/min. In conclusion, it was demonstrated that controlling the rate at - 1 degrees C/min is more suitable for cryopreservation of hematopoietic stem cells than - 0.5 degrees C/min and - 5 degrees C/min.

[In vitro suspension and bioreactor culture of hematopoietic cells].

Stirred culture offers a number of advantages over static systems as it maintains a stable, homogeneous culture environment and is easy to scale-up. This paper focused on the development and application of stirred tank bioreactor to culture hematopoietic cells. Preliminary study of stirred culture of hematopoietic cells was carried out in cord blood mononuclear cells culture in spinner flask. The results showed that the amplification rates of total cell, CFU-GM and BFU-E, with the exception of CFU-Mk, were greater in spinner flask than T-flask. The number of total cells increased 20 fold after 14 days incubation in spinner flask. The amplification rates of CFU-GM, CFU-Mk and BFU-E reached maximum at 10th day, 10th day and 7th day respectively, and the maximal amplification rates were 9.2-fold, 5.5-fold and 2.4-fold respectively, whereas the rate of CD34+ cells in spinner flask was (6.7 +/- 4.0)-fold at day 10. These results indicated that the stirred culture system is better than the static culture systems for hematopoietic cell proliferation. The biocompatibility of cord blood MNC to different types of materials used in bioreactors was also tested. The results showed that glass, stainless steel 316L and polytetraflouroethylene (PTFE) supported the growth of hematopoietic cells well. A higher cell density was reached in stirred bioreactors with controlled pH and DO than static culture. These findings suggested that the controlled large-scale culture could be used to overcome the clinical shortage of hematopoietic cells.

[In vitro culture of umbilical cord blood MNC and CD34+ selected cells].

For in vitro studies, both CD34+ selected cell and mononuclear cell (MNC) can be used to expand hematopoietic stem/progenitor cells. To investigate the expansion characteristics of mononuclear cells (MNC) and CD34+ selected cells the two cell fractions were cultured in the medium containing cytokine cocktails of SCF + IL-3 + IL-6 + FL + Tpo. It was found that the CD34+ selected cells had presented a high proliferation potential. The expansion of CD34+ selected cells could be maintained for 8 weeks while that of MNCs declined after 4 weeks. During the culture period, the maximum expansion of total cells in CD34+ selected cell culture achieved 31,270.9 +/- 8640.5 times, while that of MNC reached 50.9 +/- 8.2 times only. In the culture of MNCs, the colony density and the proportion of CD34+ cells increased from day 0 to day 7. However, in the culture of CD34+ selected cells, both the colony density and the proportion of CD34+ cells declined continuously during the whole culture period. During the ex vivo culture of CD34+ selected cells, the maximum expansion of CFU-GM and CD34+ cells achieved 185.7 +/- 14.1 fold and 191.7 +/- 188.8 fold, respectively. They are much higher than that of MNC, which were 12.4 +/- 3.2 fold and 50.6 +/- 33.2 fold only. While the BFU-E of both cell fractions only expanded by few times, which were 7.2 +/- 5.2 and 10.1 +/- 3.4 times, respectively. The results showed that the CD34+ selected cells culture could obtain more CFU-GM cells and CD34+ cells during the whole culture period.