**1. Increasing cell dose** Improved collection and processing of cord blood Infusion of two cord blood units (double cord blood transplantation) in adults Ex vivo expansion of cord blood HSC/HPC Infusion of cord blood with third-party donor cells (haploidentical graft) **2. Improving delivery and homing/retention of HSC** Direct intrabone infusion of cord blood Increased stromal-derived factor-1 (SDF-1) (CXCL12)/CXCR4 interaction (e.g., inhibition of CD26 peptidase; treatment of UCB HSC with dmPGE2) Ex vivo fucosylation of HSC/HPC **3. Improving selection of cord blood units** Enhanced HLA-matching in some clinical settings Detection of donor-specific anti-HLA antibodies **4. Modifying UCB transplant regimens** Using reduced-intensity conditioning Using T-replete protocols Using CD45-toxin conjugates for autologous UCB HSCT **5. Expanding specific cell populations (ex vivo or in vivo)** Natural killer (NK) cells T cells/pathogen-specific T cells (CMV, EBV, adenovirus) Regulatory T cells (Tregs) Neutrophils **6. Coinfusing cord blood with accessory cells** Mesenchymal stem cells (MSC) **7. Improving thymopoiesis** Interleukin-7 (IL-7), interleukin-2 (IL-2), and interleukin-15 (IL-15) Reducing sex steroid hormones (androgen, estrogen) Growth hormone (GH), insulin-like growth factor 1 (IGF-1) Keratinocyte growth factor (KGF)

Tyrosine kinase inhibition (sunitinib) FMS-like tyrosine kinase receptor III ligand (Flt3L) Stem cell factor (SCF) Inhibition of p53 (pifithrin-β (PFT-β))

initial studies have used fibroblasts [61–63], UCB may be reprogrammed to induced pluripotent stem (iPS) cells [64], which can then be differentiated into different cell lineages, e.g., to generate red blood cells and platelets. As these end cells lack nuclei, they may allay certain safety concerns with respect to iPS cells and tumorigenicity (provided that enucleated cells can survive transplantation). Currently, however, these strategies do not replicate the production of over 3 × 1011 blood cells that are generated in adults per day. Other cell types may be isolated, used, expanded, or manipulated from UCB or the umbilical cord (UC) to enhance engraftment, to eradicate malignancies, to prevent GvHD, or prevent infections. The strategies to improve UCB engraftment and immune reconstitution are listed in **Table 3**. This is updated

Increased stromal-derived factor-1 (SDF-1) (CXCL12)/CXCR4 interaction (e.g., inhibition of CD26 peptidase; treatment

from data presented in [65].

Improved collection and processing of cord blood

**2. Improving delivery and homing/retention of HSC**

Using CD45-toxin conjugates for autologous UCB HSCT **5. Expanding specific cell populations (ex vivo or in vivo)**

T cells/pathogen-specific T cells (CMV, EBV, adenovirus)

Interleukin-7 (IL-7), interleukin-2 (IL-2), and interleukin-15 (IL-15)

**6. Coinfusing cord blood with accessory cells**

Reducing sex steroid hormones (androgen, estrogen) Growth hormone (GH), insulin-like growth factor 1 (IGF-1)

Ex vivo expansion of cord blood HSC/HPC

Direct intrabone infusion of cord blood

**3. Improving selection of cord blood units** Enhanced HLA-matching in some clinical settings Detection of donor-specific anti-HLA antibodies **4. Modifying UCB transplant regimens** Using reduced-intensity conditioning

of UCB HSC with dmPGE2) Ex vivo fucosylation of HSC/HPC

Using T-replete protocols

Natural killer (NK) cells

Regulatory T cells (Tregs)

Mesenchymal stem cells (MSC) **7. Improving thymopoiesis**

Keratinocyte growth factor (KGF)

Neutrophils

Infusion of two cord blood units (double cord blood transplantation) in adults

144 Umbilical Cord Blood Banking for Clinical Application and Regenerative Medicine

Infusion of cord blood with third-party donor cells (haploidentical graft)

**1. Increasing cell dose**

Key: HSC, hematopoietic stem cells; HPC, hematopoietic progenitor cells; UCB, umbilical cord blood; HLA, human leukocyte antigen. Based on and updated from Danby and Rocha [65].

**Table 3.** Potential methods to improve engraftment and immune reconstitution in UCB transplantation.
