Going straight to the point: intra-BM injection of hematopoietic progenitors

Human Wharton's jelly-derived mesenchymal stromal cells promote bone formation in immunodeficient mice when administered into a bone microenvironment

BACKGROUND

Wharton's Jelly (WJ) Mesenchymal Stromal Cells (MSC) have emerged as an attractive allogeneic therapy for a number of indications, except for bone-related conditions requiring new tissue formation. This may be explained by the apparent recalcitrance of MSC,WJ to differentiate into the osteogenic lineage in vitro, as opposed to permissive bone marrow (BM)-derived MSCs (MSC,BM) that readily commit to bone cells. Consequently, the actual osteogenic in vivo capacity of MSC,WJ is under discussion.

METHODS

We investigated how physiological bone environments affect the osteogenic commitment of recalcitrant MSCs in vitro and in vivo. To this end, MSC of BM and WJ origin were co-cultured and induced for synchronous osteogenic differentiation in vitro using transwells. For in vivo experiments, immunodeficient mice were injected intratibially with a single dose of human MSC and bone formation was evaluated after six weeks.

RESULTS

Co-culture of MSC,BM and MSC,WJ resulted in efficient osteogenesis in both cell types after three weeks. However, MSC,WJ failed to commit to bone cells in the absence of MSC,BM's osteogenic stimuli. In vivo studies showed successful bone formation within the medullar cavity of tibias in 62.5% of mice treated with MSC, WJ. By contrast, new formed trabeculae were only observed in 25% of MSC,BM-treated mice. Immunohistochemical staining of human COXIV revealed the persistence of the infused cells at the site of injection. Additionally, cells of human origin were also identified in the brain, heart, spleen, kidney and gonads in some animals treated with engineered MSC,WJ (eMSC,WJ). Importantly, no macroscopic histopathological alterations, ectopic bone formation or any other adverse events were detected in MSC-treated mice.

CONCLUSIONS

Our findings demonstrate that in physiological bone microenvironment, osteogenic commitment of MSC,WJ is comparable to that of MSC,BM, and support the use of off-the-shelf allogeneic MSC,WJ products in bone repair and bone regeneration applications.

Spleen route accelerates engraftment of human hematopoietic stem cells

Intravenous injections of human hematopoietic stem cells (hHSCs) is routinely used in clinic and for modeling hematopoiesis in mice. However, unspecific dilution in vascular system and non-hematopoietic organs challenges engraftment efficiency. Although spleen is capable of extra medullar hematopoiesis, its ability to support human HSC transplantation has never been evaluated. We demonstrate that intra-splenic injection results in high and sustained engraftment of hHSCs into immune-deficient mice, with higher chimerisms than with intravenous or intra-femoral injections. Our results support that spleen microenvironment provides a niche for HSCs amplification and offers a new route for efficient HSC transplantation.

Cell therapies in the clinic

Cell therapies have emerged as a promising therapeutic modality with the potential to treat and even cure a diverse array of diseases. Cell therapies offer unique clinical and therapeutic advantages over conventional small molecules and the growing number of biologics. Particularly, living cells can simultaneously and dynamically perform complex biological functions in ways that conventional drugs cannot; cell therapies have expanded the spectrum of available therapeutic options to include key cellular functions and processes. As such, cell therapies are currently one of the most investigated therapeutic modalities in both preclinical and clinical settings, with many products having been approved and many more under active clinical investigation. Here, we highlight the diversity and key advantages of cell therapies and discuss their current clinical advances. In particular, we review 28 globally approved cell therapy products and their clinical use. We also analyze >1700 current active clinical trials of cell therapies, with an emphasis on discussing their therapeutic applications. Finally, we critically discuss the major biological, manufacturing, and regulatory challenges associated with the clinical translation of cell therapies.

Bone Marrow Cell Trafficking Analyzed by 89Zr-oxine Positron Emission Tomography in a Murine Transplantation Model

Purpose: The success of hematopoietic stem cell transplantation (HSCT) depends on donor cell homing to the bone marrow. However, there is no reliable method of noninvasively monitoring the kinetics and distribution of transferred cells. Using zirconium-89 (89Zr)-oxine cell labeling combined with PET imaging, we sought to visualize and quantify donor cell homing in a mouse bone marrow transplantation model.Experimental Design: The effect of 89Zr-oxine labeling on bone marrow cell viability and differentiation was evaluated in vitro89Zr-labeled bone marrow cells (2 × 107 cells, 16.6 kBq/106 cells) were transferred intravenously, and serial microPET images were obtained (n = 5). The effect of a CXCR4 inhibitor, plerixafor (5 mg/kg) and G-CSF (2.5 μg) on bone marrow homing and mobilization were examined (n = 4). Engraftment of the transferred 89Zr-labeled cells was evaluated (n = 3).Results:89Zr-oxine-labeled bone marrow cells showed delayed proliferation, but differentiated normally. Transferred bone marrow cells rapidly migrated to the bone marrow, spleen, and liver (n = 5). Approximately 36% of donor cells homed to the bone marrow within 4 hours, irrespective of prior bone marrow ablation. Inhibition of CXCR4 by plerixafor alone or with G-CSF significantly blocked the bone marrow homing (P < 0.0001, vs. nontreated, at 2 hours), confirming a crucial role of the CXCR4-CXCL12 system. Mobilization of approximately 0.64% of pretransplanted bone marrow cells induced a 3.8-fold increase of circulating bone marrow cells. 89Zr-labeled donor cells engrafted as well as nonlabeled cells.Conclusions:89Zr-oxine PET imaging reveals rapid bone marrow homing of transferred bone marrow cells without impairment of their stem cell functions, and thus, could provide useful information for optimizing HSCT. Clin Cancer Res; 23(11); 2759-68. ©2016 AACR.

Intra-Bone Marrow Transplantation Confers Superior Multilineage Engraftment of Murine Aorta-Gonad Mesonephros Cells Over Intravenous Transplantation

Hematopoietic stem cell (HSC) engraftment has been achieved using single-cell transplantation of prospectively highly purified adult HSC populations. However, bulk transplants are still performed when assessing the HSC potential of early embryonic hematopoietic tissues such as the aorta-gonad mesonephros (AGM) due to very low HSC activity content early in development. Intra-bone marrow transplantation (IBMT) has emerged as a superior administration route over intravenous (IV) transplantation for assessing the reconstituting ability of human HSCs in the xenotransplant setting since it bypasses the requirement for homing to the BM. In this study, we compared the ability of IBMT and IV administration of embryonic day 11.5 AGM-derived cells to reconstitute the hematopoietic system of myeloablated recipients. IBMT resulted in higher levels of AGM HSC long-term multilineage engraftment in the peripheral blood, BM, spleen, and thymus of primary and secondary recipients, and in limiting dilution experiments. The administration route did not skew the multilineage contribution pattern, but IBMT conferred higher Lineage(-)Sca-1(+)c-kit(+) long-term engraftment, in line with the superior IBMT reconstitution. Therefore, IBMT represents a superior administration route to detect HSC activity from developmentally early sources with limited HSC activity content, such as the AGM.

Intrabone marrow injection enhances placental mesenchymal stem cellmediated support of hematopoiesis in mice

BACKGROUND/AIM

In order to determine the synergistic effects of human placental mesenchymal stem cells (PMSCs) on hematopoiesis in vivo, we compared the intrabone marrow injection (IBMI) with the conventional intravenous injection (IVI).

MATERIALS AND METHODS

C57BL/6 recipient mice conditioned with lethal doses of irradiation were transplanted with bone marrow mononuclear cells (MNCs) and bone marrow-derived mesenchymal stem cells (BMSCs) from BALB/c mice by IBMI or IVI. NOD/SCID recipient mice conditioned with sublethal doses of irradiation were transplanted with human umbilical cord blood MNCs (UCB-MNCs) and PMSCs by IBMI or IVI.

RESULTS

The number of hematopoietic cells was significantly higher in mice transplanted with BMSCs by IBMI than in those transplanted by IVI in a murine transplantation model (BALB/c→C57BL/6). Moreover, the percentage of human hematopoietic cells in the tibiae of the NOD/SCID mice that were transplanted with PMSCs plus UCB-MNCs was higher than that in mice transplanted with UCB-MNCs alone. In addition, in mice that were transplanted with PMSCs, PMSCs injected by IBMI were more efficient than those injected by IVI.

CONCLUSION

Our results not only elucidated the role of PMSCs in promoting hematopoiesis, but also revealed the therapeutic potential of the combination of PMSCs and IBMI in transplantation.

Superselective intra-arterial umbilical cord blood administration to BM in experimental animals

Umbilical cord blood (UCB) as a source of hematopoietic stem cells for transplantation is limited by the low number of cells and delayed engraftment. UCB cells are infused i.v. for transplantation, although only a proportion of the cells reach the BM. We investigated whether UCB could be administered safely using superselective intra-arterial (i.a.) injection. We injected human UCB (5 × 10⁶) into the aorta in rats, into the iliac artery in mice and into the femoral nutrient artery (FNA) in rabbits. We used angiography, immunohistochemistry, intravital microscopy and qPCR to assess safety end points and the distribution of injected cells. All animals showed normal behavior. No evidence of organ infarction was noted. UCB injected into the FNA of rabbits did not change the flow rates, measured by angiography. By qPCR, we found significantly higher fold-change values in the injected BM compared with i.v. injection (P=0.0087). Using intravital microscopy we visualized the mouse capillary bed during i.a. injection without cellular congestion. In summary, we show that i.a. infusion of UCB is safe and reaches an eightfold increase in engraftment in the BM compared with i.v. infusion. These studies lay the foundation for clinical trials.

Effects of MSC Coadministration and Route of Delivery on Cord Blood Hematopoietic Stem Cell Engraftment

Hematopoietic stem cell transplantation (HSCT) using umbilical cord blood (UCB) progenitors is increasingly being used. One of the problems that may arise after UCB transplantation is an impaired engraftment. Either intrabone (IB) injection of hematopoietic progenitors or mesenchymal stem cell (MSC) coadministration has been proposed among the strategies to improve engraftment. In the current study, we have assessed the effects of both approaches. Thus, NOD/SCID recipients were transplanted with human UCB CD34+ cells administered either intravenously (IV) or IB, receiving or not bone marrow (BM)-derived MSCs also IV or IB (in the right femur). Human HSC engraftment was measured 3 and 6 weeks after transplantation. Injected MSCs were tracked weekly by bioluminescence. Also, lodgment within the BM niche was assessed at the latter time point by immunofluorescence. Our study shows regarding HSC engraftment that the number of BM human CD45+ cells detected 3 weeks after transplantation was significantly higher in mice cotransplanted with human MSCs. Moreover, these mice had a higher myeloid (CD13+) engraftment and a faster B-cell (CD19+) chimerism. At the late time point evaluated (6 weeks), human engraftment was higher in the group in which both strategies were employed (IB injection of HSC and MSC coadministration). When assessing human MSC administration route, we were able to track MSCs only in the injected femurs, whereas they lost their signal in the contralateral bones. These human MSCs were mainly located around blood vessels in the subendosteal region. In summary, our study shows that MSC coadministration can enhance HSC engraftment in our xenogenic transplantation model, as well as IB administration of the CD34+ cells does. The combination of both strategies seems to be synergistic. Interestingly, MSCs were detected only where they were IB injected contributing to the vascular niche.

Irradiated allogeneic cells enhance umbilical cord blood stem cell engraftment in immunodeficient mice

Umbilical cord blood (UCB) is a readily available source of hematopoietic stem cells for transplantation. UCB hematopoietic SCT for average- and large-sized patients is often limited by the number of cells available in a single unit. To address this limitation, we performed experiments to determine if adjunctive therapy with third-party human allogeneic cells enhances the engraftment of human UCB in immunodeficient mice. UCB cells with or without sequential infusion of irradiated third-party allogeneic cells were used in transplantation studies of NOD/SCID and NOD/SCID-IL2Rγ null mice. We studied the impact of irradiated allogeneic cells on colony formation in vitro using long-term culture assays also. Our studies demonstrate that short- and long-term UCB engraftment of immunodeficient mice is enhanced by irradiated allogeneic cells. Secondary transplants demonstrate the durability of engraftment. These preclinical studies support the further development of irradiated allogeneic cells as an adjunct to single UCB transplantation when limiting numbers of cells are available.

Bone marrow mesenchymal stem cells for improving hematopoietic function: an in vitro and in vivo model. Part 2: Effect on bone marrow microenvironment

The aim of the present study was to determine how mesenchymal stem cells (MSC) could improve bone marrow (BM) stroma function after damage, both in vitro and in vivo. Human MSC from 20 healthy donors were isolated and expanded. Mobilized selected CD34⁺ progenitor cells were obtained from 20 HSCT donors. For in vitro study, long-term bone marrow cultures (LTBMC) were performed using a etoposide damaged stromal model to test MSC effect in stromal confluence, capability of MSC to lodge in stromal layer as well as some molecules (SDF1, osteopontin,) involved in hematopoietic niche maintenance were analyzed. For the in vivo model, 64 NOD/SCID recipients were transplanted with CD34+ cells administered either by intravenous (IV) or intrabone (IB) route, with or without BM derived MSC. MSC lodgement within the BM niche was assessed by FISH analysis and the expression of SDF1 and osteopontin by immunohistochemistry. In vivo study showed that when the stromal damage was severe, TP-MSC could lodge in the etoposide-treated BM stroma, as shown by FISH analysis. Osteopontin and SDF1 were differently expressed in damaged stroma and their expression restored after TP-MSC addition. Human in vivo MSC lodgement was observed within BM niche by FISH, but MSC only were detected and not in the contralateral femurs. Human MSC were located around blood vessels in the subendoestal region of femurs and expressed SDF1 and osteopontin. In summary, our data show that MSC can restore BM stromal function and also engraft when a higher stromal damage was done. Interestingly, MSC were detected locally where they were administered but not in the contralateral femur.

Intrabone marrow transplantation of unwashed cord blood using reduced-intensity conditioning treatment: a phase I study

The outcome of cord blood transplantation following reduced-intensity conditioning is suboptimal because of fatal infection triggered by prolonged neutropenia and graft-versus-host disease (GVHD) in addition to graft rejection. Intrabone marrow injection (IBMI) may improve the outcome by providing better hematopoietic engraftment and less GVHD. We therefore evaluated IBMI safety in reduced-intensity stem cell transplantation. Furthermore, we used unwashed cord blood to avoid stem cell loss. Ten patients (median age = 61 years old) were enrolled. Cord blood cells were thawed at the bedside and injected into 4 iliac bone sites (2 at each hemipelvis). The procedure was well tolerated with no injection-related complications. Nine patients achieved donor engraftment. The median time to neutrophil recovery (>0.5 × 10(9)/L) was 17 days, and platelet recovery was achieved in 8 patients. Early full donor chimerism was achieved (median of 15 and 20 days in T cells and myeloid cells, respectively). Three of 9 evaluable patients developed grade II to III GVHD, and 5 of 10 patients died of treatment-related toxicities. The probability of survival at 1 year was 46.7%. IBMI of unwashed cord blood following reduced-intensity conditioning is safe, well tolerated, and may lead to an increased donor engraftment rate.