Expansion of Cord Blood CD34+ Cells in Presence of zVADfmk and zLLYfmk Improved Their In Vitro Functionality and In Vivo Engraftment in NOD/SCID Mouse

BACKGROUND: Cord blood (CB) is a promising source for hematopoietic stem cell transplantations. The limitation of cell dose associated with this source has prompted the ex vivo expansion of hematopoietic stem and progenitor cells (HSPCs). However, the expansion procedure is known to exhaust the stem cell pool causing cellular defects that promote apoptosis and disrupt homing to the bone marrow. The role of apoptotic machinery in the regulation of stem cell compartment has been speculated in mouse hematopoietic and embryonic systems. We have consistently observed an increase in apoptosis in the cord blood derived CD34(+) cells cultured with cytokines compared to their freshly isolated counterpart. The present study was undertaken to assess whether pharmacological inhibition of apoptosis could improve the outcome of expansion. METHODOLOGY/PRINCIPAL FINDINGS: CB CD34(+) cells were expanded with cytokines in the presence or absence of cell permeable inhibitors of caspases and calpains; zVADfmk and zLLYfmk respectively. A novel role of apoptotic protease inhibitors was observed in increasing the CD34(+) cell content of the graft during ex vivo expansion. This was further reflected in improved in vitro functional aspects of the HSPCs; a higher clonogenicity and long term culture initiating potential. These cells sustained superior long term engraftment and an efficient regeneration of major lympho-myeloid lineages in the bone marrow of NOD/SCID mouse compared to the cells expanded with growth factors alone. CONCLUSION/SIGNIFICANCE: Our data show that, use of either zVADfmk or zLLYfmk in the culture medium improves expansion of CD34(+) cells. The strategy protects stem cell pool and committed progenitors, and improves their in vitro functionality and in vivo engraftment. This observation may complement the existing protocols used in the manipulation of hematopoietic cells for therapeutic purposes. These findings may have an impact in the CB transplant procedures involving a combined infusion of unmanipulated and expanded grafts

Contribution of human hematopoietic stem cells to liver repair

Immune-deficient mouse models of liver damage allow examination of human stem cell migration to sites of damage and subsequent contribution to repair and survival. In our studies, in the absence of a selective advantage, transplanted human stem cells from adult sources did not robustly become hepatocytes, although some level of fusion or hepatic differentiation was documented. However, injected stem cells did home to the injured liver tissue and release paracrine factors that hastened endogenous repair and enhanced survival. There were significantly higher levels of survival in mice with a toxic liver insult that had been transplanted with human stem cells but not in those transplanted with committed progenitors. Transplantation of autologous adult stem cells without conditioning is a relatively safe therapy. Adult stem cells are known to secrete bioactive factors that suppress the local immune system, inhibit fibrosis (scar formation) and apoptosis, enhance angiogenesis, and stimulate recruitment, retention, mitosis, and differentiation of tissue-residing stem cells. These paracrine effects are distinct from the direct differentiation of stem cells to repair tissue. In patients at high risk while waiting for a liver transplant, autologous stem cell therapy could be considered, as it could delay the decline in liver function

In vitro trans-differentiation of human umbilical cord derived hematopoietic stem cells into hepatocyte like cells using combination of growth factors for cell based therapy

The aim of the study was to develop a new strategy for the differentiation of hematopoietic stem cell (HSC) derived from UCB into hepatocyte like cells and also to estimate the effects of combination of fibroblast growth factor 4 (FGF 4) and hepatocyte growth factor (HGF) on hematopoietic stem cell differentiation. HSCs were isolated and purified by magnetic activated cell sorting. HSCs were induced to hepatocyte like cells under a 2-step protocol with combination of growth factors. Reverse transcription polymerase chain reaction was performed to detect multiple genes related to hepatocyte like cells development and function. Hepatocyte like morphology was illustrated by inverted repeat microscope and the secretion of albumin and α- fetoprotein by these cells was confirmed by enzyme linked immunosorbent assay. Hepatocyte like cells was observed at the end of the protocol (days 14). These differentiated cells were observed to show high expression of genes related to hepatocytes (tryptophan 2, 3-dioxygenase [TO], glucose 6-phosphate [G6P], cytokeratin 18 [CK 18], albumin and α- fetoprotein [AFP]). The quantities of albumin and AFP at day 0 were low and upon differentiation the cells were able to produce albumin and AFP at high levels. Our results show a new strategy for differentiation in a short duration, using a combination of growth factors for the differentiation of umbilical cord blood derived HSC into hepatocyte like cells under certain in vitro conditions. After further studies this approach has the potency, for widespread cell replacement therapy for liver diseases