Mesenchymal stromal cells expanded in human allogenic cord blood serum display higher self-renewal and enhanced osteogenic potential.

Recent clinical trials using ex vivo expanded mesenchymal stromal cells (MSCs) have raised interest in the safety and function of cultured MSCs. Here, to assess the feasibility of using allogenic human umbilical cord blood serum (CBS) for humanized clinical-grade expansion of MSCs, we characterized MSCs expanded in CBS and compared them to MSCs expanded in fetal bovine serum (FBS). MSCs in CBS exhibited a higher preservation of colony-forming cells and an accelerated expansion over serial passages with increased Oct-4 expression compared to those cultured in FBS. Notably, CBS-expanded MSCs exhibited a unique differentiation potential characterized by a shift from adipogenic to osteogenic differentiation. The differentiation shift was associated with enhanced basal and Runx2-mediated transcriptional activation of the osteocalcin promoter, as well as increased accumulation of beta-catenin and the yes-associated protein (YAP) which was independent of changes in TAZ (transcriptional co-activator with PDZ-binding motif) levels. Interestingly, the phenotypes were reversed when the FBS and CBS media were switched, suggesting the unique stimulatory effects of CBS rather than the selection of heterogeneous MSC subpopulations. The distinct regulatory effects of CBS on MSC included selective activation of platelet-derived growth factor and epidermal growth factor signals in MSCs, but not in FBS. Taken together, these results provide insight into the dynamic regulation of MSCs during ex vivo culture and show that the ex vivo culture of MSCs in allogenic human CBS provides a novel tool for the accelerated expansion of a population of MSCs that exhibit a higher self-renewal and an enhanced osteogenic potential.

Efficient bone marrow transduction by gene transfer with allogeneic umbilical cord blood serum and plasma: an implication for clinical trials.

Low in vivo transduction efficiency and safety concerns have been hurdles for effective hematopoietic stem cell (HSC) gene therapy. Here, we investigate whether the safety and efficiency of retroviral gene transfer into HSCs can be improved by using human allogeneic umbilical cord blood (UCB)-derived supplements instead of fetal bovine serum (FBS). When CD34(+) cells were cultured ex vivo in UCB-derived serum (CBS) or plasma (CBP), comparable or higher maintenance of HSCs was observed than in FBS and serum-free substitution medium (SFM) as assessed by the frequency of positive engraftment and the level of engraftment in NOD/SCID mice after transplantation of cultured cells. CBS and CBP also exhibited higher level stabilization of retroviral particles than SFM during in vitro culture of retrovirus pseudotyped with gibbon ape leukemia virus or vesicular stomatitis virus glycoprotein. Retroviral gene transfer into CD34(+) cells performed with CBS or CBP resulted in increased gene transfer into CD34(+) cells and increased transduction of reconstituted bone marrow cells compared to transfers with SFM or FBS. The increased transduction of bone marrow cells was associated with a larger number of transduced progenitors in the recipient mice. Significant oligoclonality in the transduced progenitors, as determined by ligation-mediated polymerase chain reaction, suggested efficient retroviral targeting of multiple HSCs in the CBS- or CBP-supplemented media. Combined, our results show that allogeneic UCB-derived serum or plasma is a safe and easily accessible serum supplement that can support efficient retroviral gene transfer into HSCs for the clinical-grade manipulation of HSCs.