Transplanted human bone marrow progenitor subtypes stimulate endogenous islet regeneration and revascularization.

Transplanted murine bone marrow (BM) progenitor cells recruit to the injured pancreas and induce endogenous beta cell proliferation to improve islet function. To enrich for analogous human progenitor cell types that stimulate islet regeneration, we purified human BM based on high-aldehyde dehydrogenase activity (ALDH(hi)), an enzymatic function conserved in hematopoietic, endothelial, and mesenchymal progenitor lineages. We investigated the contributions of ALDH(hi) mixed progenitor cells or culture-expanded, ALDH-purified multipotent stromal cell (MSC) subsets to activate endogenous programs for islet regeneration after transplantation into streptozotocin-treated NOD/SCID mice. Intravenous injection of uncultured BM ALDH(hi) cells improved systemic hyperglycemia and augmented insulin secretion by increasing islet size and vascularization, without increasing total islet number. Augmented proliferation within regenerated endogenous islets and associated vascular endothelium indicated the induction of islet-specific proliferative and pro-angiogenic programs. Although cultured MSC from independent human BM samples showed variable capacity to improve islet function, and prolonged expansion diminished hyperglycemic recovery, transplantation of ALDH-purified regenerative MSC reduced hyperglycemia and augmented total beta cell mass by stimulating the formation of small beta cell clusters associated with the ductal epithelium, without evidence of increased islet vascularization or Ngn3(+) endocrine precursor activation. Thus, endogenous islet recovery after progenitor cell transplantation can occur via distinct regenerative mechanisms modulated by subtypes of progenitor cells administered. Further, understanding of how these islet regenerative and pro-angiogenic programs are activated by specific progenitor subsets may provide new approaches for combination cellular therapies to combat diabetes.

Revascularization of ischemic limbs after transplantation of human bone marrow cells with high aldehyde dehydrogenase activity.

The development of cell therapies to treat peripheral vascular disease has proven difficult because of the contribution of multiple cell types that coordinate revascularization. We characterized the vascular regenerative potential of transplanted human bone marrow (BM) cells purified by high aldehyde dehydrogenase (ALDH(hi)) activity, a progenitor cell function conserved between several lineages. BM ALDH(hi) cells were enriched for myelo-erythroid progenitors that produced multipotent hematopoietic reconstitution after transplantation and contained nonhematopoietic precursors that established colonies in mesenchymal-stromal and endothelial culture conditions. The regenerative capacity of human ALDH(hi) cells was assessed by intravenous transplantation into immune-deficient mice with limb ischemia induced by femoral artery ligation/transection. Compared with recipients injected with unpurified nucleated cells containing the equivalent of 2- to 4-fold more ALDH(hi) cells, mice transplanted with purified ALDH(hi) cells showed augmented recovery of perfusion and increased blood vessel density in ischemic limbs. ALDH(hi) cells transiently recruited to ischemic regions but did not significantly integrate into ischemic tissue, suggesting that transient ALDH(hi) cell engraftment stimulated endogenous revascularization. Thus, human BM ALDH(hi) cells represent a progenitor-enriched population of several cell lineages that improves perfusion in ischemic limbs after transplantation. These clinically relevant cells may prove useful in the treatment of critical ischemia in humans.

Functional analysis of human hematopoietic repopulating cells mobilized with granulocyte colony-stimulating factor alone versus granulocyte colony-stimulating factor in combination with stem cell factor.

Using in vitro progenitor assays, serum-free in vitro cultures, and the nonobese diabetic/severe combined immune-deficient (NOD/SCID) ecotropic murine virus knockout xenotransplantation model to detect human SCID repopulating cells (SRCs) with multilineage reconstituting function, we have characterized and compared purified subpopulations harvested from the peripheral blood (PB) of patients receiving granulocyte colony-stimulating factor (G-CSF) alone or in combination with stem cell factor (SCF). Mobilized G-CSF plus SCF PB showed a 2-fold increase in total mononuclear cell content and a 5-fold increase in CD34-expressing cells depleted for lineage-marker expression (CD34(+)Lin(-)) as compared with patients treated with G-CSF alone. Functionally, G-CSF plus SCF-mobilized CD34(+)CD38(-)Lin(-) cells contained a 2-fold enhancement in progenitor frequency as compared with G-CSF-mobilized subsets. Despite enhanced cellularity and progenitor capacity, G-CSF plus SCF mobilization did not increase the frequency of SRCs as determined by limiting dilution analysis by means of unfractionated PB cells. Purification of SRCs from these sources demonstrated that as few as 1000 CD34(+)CD38(-)Lin(-) cells from G-CSF-mobilized PB contained SRC capacity while G-CSF plus SCF-mobilized CD34(+)CD38(-)Lin(-) cells failed to repopulate at doses up to 500 000 cells. In addition, primitive CD34(-)CD38(-)AC133(+)Lin(-) cells derived from G-CSF plus SCF-mobilized PB were capable of differentiation into CD34-expressing cells, while the identical subfractions from G-CSF PB were unable to produce CD34(+) cells in serum-free cultures. Our study defines qualitative and quantitative distinctions among subsets of primitive cells mobilized by means of G-CSF plus SCF versus G-CSF alone, and therefore has implications for the utility of purified repopulating cells from these sources.