Background: Congenital heart disease (CHD) continues to be among the most common birth defects, affecting an estimated 40 000 births annually in the United States. The most common complication of CHD is heart failure. With improved medical management and surgical outcomes, survival for complex congenital heart defects has dramatically improved, but consequentially there are more adults with CHD than children with CHD. Due to longer-term sequelae of CHD, surgical and medical treatment previously thought to be curative is now realized at best to be palliative, and there is a considerable burden of CHD-related heart failure. Stem cell therapy as an adjunct to current surgical and medical strategies is being explored in an effort to ameliorate CHD-related heart failure. This review aims to explore the current literature with regard to stem cell therapy for CHD as well as ongoing trials. Methods: A MEDLINE (Ovid), MEDLINE (Pubmed), and clinicaltrials.gov search were performed using the medical subject headings congenital heart defects combined with hematopoietic stem cells, stem cell transplantation, mesenchymal stem cells (MSC), cell-or tissue-based therapy, or MSC transplantation. Articles must have been published after 2010.Results: Twenty three articles and 9 ongoing trials met all inclusion criteria.Conclusions: Areas of interest include myocardiocyte regeneration, tissue graft development to minimize reoperations, and methods of stem cell delivery. While several small trials are showing promise, it is too soon to make definitive statements about the future of stem cell therapies in this field.

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is a widely available curative option for patients with sickle cell disease (SCD). Our original non-myeloablative haplo-HSCT trial employing post-transplant (PT) cyclophosphamide had a low incidence of GVHD but had high rejection rates. Here, we aimed to evaluate immune reconstitution following haplo-HSCT and identify cytokines and cells associated with graft rejection/engraftment. 50 cytokines and 10 immune cell subsets were screened using multiplex-ELISA and flow cytometry, respectively, at baseline and PT-Days 30, 60, 100, and 180. We observed the most significant differences in cytokine levels between the engrafted and rejected groups at PT-Day 60, corresponding with clinical findings of secondary graft rejection. Of the 44 cytokines evaluated, plasma concentrations of 19 cytokines were different between the two groups at PT-Day 60. Factor analysis suggested two independent factors. The first factor (IL-17A, IL-10, IL-7, G-CSF, IL-2, MIP-1a, VEGF, and TGFb1 contributed significantly) was strongly associated with engraftment with OR = 2.7 (95%CI of 1.4 to 5.4), whereas the second factor (GROa and IL-18 contributed significantly) was not significantly associated with engraftment. Sufficient donor myeloid chimerism (DMC) is critical for the success of HSCT; here, we evaluated immune cells among high (H) DMC (DMC≥20%) and low (L) DMC (DMC<20%) groups along with engrafted and rejected groups. We found that early myeloid-derived suppressor cell (eMDSC) frequencies were elevated in engrafted patients and patients with HDMC at PT-Day 30 (P< 0.04 & P< 0.003, respectively). 9 of 20 patients were evaluated for the source of eMDSCs. The HDMC group had high mixed chimeric eMDSCs as compared to the LDMC group (P< 0.00001). We found a positive correlation between the frequencies of eMDSCs and Tregs at PT-Day 100 (r=0.72, P <0.0007); eMDSCs at BSL and Tregs at PT-Day 100 (r=0.63, P <0.004). Of 10 immune regulatory cells and 50 cytokines, we observed mixed chimeric eMDSCs and IL-17A, IL-10, IL-7, G-CSF, IL-2, MIP-1a, VEGF, TGFb1 as potential hits which could serve as prognostic markers in predicting allograft outcome towards engraftment following haploidentical HSCT employing post-transplant cyclophosphamide. The current findings need to be replicated and further explored in a larger cohort.

Sickle cell disease (SCD) is an inherited blood disorder in which red blood cells are sickle-shaped as a result of an amino acid alteration from glutamate to valine at the sixth position of the β-globin chain. Hematopoietic stem cell transplant (HSCT) is a curative option for SCD, with both HLA-matched and haploidentical transplant being viable approaches. Stable mixed chimerism and tolerance induction are sufficient to reverse the sickle phenotype. Graft rejection and graft versus host disease may occur following nonmyeloablative haploidentical peripheral blood stem cell transplantation (PBSCT). Various regulatory cytokines have been identified as biomarkers of engraftment in graft transplantation. Previously, we observed that TGF-β, interleukin (IL)-7, and IL-10 cytokines were elevated in engrafted SCD patients as compared to those who rejected their grafts following haploidentical PBSCT. Now, we aim to identify the immune cell populations responsible for producing the above cytokines in both engrafted and rejected patients. The plasma samples of 21 SCD patients who underwent nonmyeloablative haploidentical PBSCT at the National Institutes of Health between March 2010 and September 2015 were evaluated previously by multiplexed magnetic bead enzyme linked immune sorbent assay. Here, we analyzed various immune cells which produce the above regulatory cytokines through multi-color flow cytometry in 8 out of the 21 patients (four engrafted and four rejected). We evaluated the cytokine producing capabilities via intracellular cytokine detection among T regulatory (Treg, CD3+CD4+CD25+Foxp3+) cells, Type 1 regulatory (Tr1, CD3+CD4+Foxp3-CD45RA-CD49+LAG3+) T cells, T helper 1 (Th1, CD3+CD4+Foxp3-CD45RO+CXCR3+) cells, T helper 17 (Th17, CD3+CD4+Foxp3-CD45RO+CCR6+) cells, natural killer (NK, CD3-CD56+NKG2D+) cells, B regulatory (Breg, CD3-CD56-CD19+CD24hiCD38hi)cells, polymorphonuclear-myeloid derived suppressor cells (PMN-MDSCs, CD45+CD14-CD15+CD11b+), monocytic-MDSCs (CD45+CD14+CD15-HLADRlow), early-MDSCs (CD45+Lin-HLADR-CD11b+CD33+), myeloid dendritic cells (mDCs, CD45+CD3-CD56-HLADR+CD11c+CD123-), and plasmacytoid dendritic cells (pDCs, CD45+CD3-CD56-HLADR+CD11c-CD123+). Cytokine producing cell frequencies were measured at five timepoints: baseline (day 0) and days 30, 60, 100, and 180 post-transplant (PT). Percentages of intracellular cytokine and cell population frequencies were assessed through flow cytometry analysis and statistical significance was determined by Student's t-test. We noted IL-10-producing Tregs were significantly elevated in engrafted patients at PT day 100 (p< 0.01, see Figure 1). Further, IL-10-producing Th1 cells were significantly higher in engrafted patients on PT day 30 (p< 0.01) and day 100 (p< 0.01). However, rejected patients had significantly higher amounts of IL-10-producing PMN-MDSCs (p< 0.01), and myeloid DCs (p< 0.01, see Figure 2), but their levels were lower than IL10-producing Tregs and Th1 cells of engrafted patients. There were no significantly different alterations of IL-10-producing cell frequencies among other cell populations (Tr1, Th17, NK, Breg, early-MDSCs, monocytic-MDSCs, and pDCs). In addition, there were no significant variations in TGF-β- and IL-7-producing cell frequencies in any of the immune cell populations tested. Overall, the engrafted patients showed higher IL-10-producing Tregs and Th1 cells at PT day 30 and/or day 100, which suggest that the immunosuppressive cytokine IL-10 may play an important role in engraftment. Further analyses with a larger sample size are indicated to evaluate whether IL-10 producing immune regulatory cells may serve as a biomarker to predict transplant outcome. Taken together, continuous regulatory cytokine analysis at serial time points pre- and post-transplant may aid in establishing mechanisms of successful engraftment and tolerance induction. Disclosures No relevant conflicts of interest to declare.