Human Cord Blood CD34+ Cells

Morphology and Fold Changes of CD34+ Cells Expanded with Hwjscs and HWJSC-CM

Human umbilical cord blood (UCB) CD34+ cells are effective in treating hematological disorders, but their clinical application is limited by low cell numbers. Mesenchymal stem cells (MSCs) in bone marrow act as a scaffold for CD34+ cell proliferation. Lin's team aims to evaluate the use of allogeneic MSCs from human UC Wharton's jelly (hWJSCs) as a stromal support to expand CD34+ cells ex vivo.

The human cord blood CD34+ cells expanded in the presence of hWJSCs had an elongated morphology and pseudopodia-like outgrowths, and migrated towards and loosely attached to the hWJSCs. They showed similar morphologic changes when they were cultured with hWJSC-CM. This behavior was not observed in the controls as the CD34+ cells continued to show their usual circular morphologies (Fig. 1A (a-f)). There were significantly greater viable CD34+ cell numbers after 7 days of culture with hWJSC-CM. The viable cell counts using trypan blue staining were hWJSCs, 0.74 ± 0.10 × 10⁶; hWJSC-CM, 0.84 ± 0.02 × 10⁶; and controls, 0.63 ± 0.04 × 10⁶ (Fig. 1B). The fold change increases were also significant greater with hWJSCs and hWJSC-CM compared to controls. The fold changes normalized to initial starting number of cells were hWJSCs, 27 ± 4; hWJSC-CM, 24 ± 1; and controls, 15 ± 1 (Fig. 1C).

HIF-MSC do not Alter the Viability and Proliferative Capacity of CD34+ Cells

Poor graft function or graft failure after allogeneic stem cell transplantation remains a significant challenge. Mesenchymal stromal cells (MSC) represent a potential treatment strategy due to their angiogenic and immunomodulatory functions. Preciado et al. aim to assess whether co-infusion of human cord blood CD34+ cells with MSC overexpressing hypoxia-inducible factor-1α (HIF-MSCs) may promote hematopoietic stem cell engraftment and function in vitro and in vivo.

They set an in vitro co-culture experiment to evaluate the effect of HIF-MSC in CD34+ cells. Cell viability assays of CD34+ cells were performed after 72 h of co-culture with MSC (n = 10). 78.74% [60.64%-81.66%] of CD34+ cells were viable when co-cultured with MSC WT, with no significant differences with the co-culture with HIF-MSC (75.78% [62.61-77.75%]) (Annexin V-/7-AAD-). There were also no significant differences in the percentage of early apoptotic cells (Annexin V+/7-AAD-), late apoptotic cells (Annexin V+/7-AAD+) and dead cells (Annexin V-/7-AAD+) between both groups (Fig. 2A). Regarding cell cycle, both CD34+ cells co-cultured with MSC WT or HIF-MSC show similar profiles. They did not find significant differences in the percentage of cells in Phase G0/G1 (93.42% [92.11-94.63%] vs 93.97% [92.41-95.72%]), Phase G2/M (0.43% [0.17-0.51%] vs 0.37% [0.22-0.58%]) and S Phase (6.15% [5.30-7.27%] vs 5.44% [40.6-7.22%]) between MSC WT and HIF-MSC, respectively (n = 7) (Fig. 2B).