abstract / Paediatrics and Adolescent Medicine / Doctoral / Doctor of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / abstract / Medicine / Master / Doctor of Medicine

published_or_final_version / abstract / Medicine / Master / Master of Philosophy

published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Medicine / Master / Master of Philosophy

published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy

Opportunistic infection is always a potentially life threatening complication in pediatric oncology patients and hematopoietic stem cell transplant recipients. With the advances in various disease treatment protocols, the overall and event-free survivals of this high risk population improve significantly. In this thesis, the author reported a number of original studies to discuss different strategies in prevention of this serious complication. Firstly, the author demonstrates that pediatric oncology patients are still vulnerable to various vaccine-preventable infectious diseases up to 18 months after stopping chemotherapy. For those vaccine-preventable infectious diseases, pediatric oncology patients can mount a significant and persistent immune response to common inactivated vaccine (namely diphtheria-tetanus-pertussis vaccine). For non-vaccine preventable infectious diseases, regular monitoring of plasma viral load and strategic use of antiviral agents as pre-emptive or prophylactic agent is an effective approach to prevent infection. In hematopoietic stem cell transplant setting, adoptive transfer of acquired immunity from donor to recipient and incorporation of this parameter in donor selection process can be considered. The findings of the studies can be applied to clinical setting. The future direction of our studies includes the immune responses of other common vaccines namely pneumococcal vaccine and pandemic influenza vaccine in high risk population. The role of transfer of donor's varicella zoster immunity in prevention of herpes zoster infection in transplant recipient can be further explored. With the advances in supportive care of our vulnerable patients, the survival rate is expected to be further improved in the future. / by Frankie Wai Tsoi, Cheng. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (M.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 193-208). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.

Allogeneic haematopoietic stem cell transplantation (HSCT) has been used successfully to treat children and adults with high-risk or relapsed hematopoietic malignancies, marrow failure syndromes, and hereditary immunodeficiency disorders. When initially developed, allogeneic HSCT was conceived as a method of rescuing patients from the toxic side effects of dose-intensive chemoradiotherapy. Due to transplant-related toxicities, the application of myeloablative allogeneic HSCT has been limited to younger patients without organ dysfunctions. Since the early 1990s many groups of investigators have explored strategies using less intensive preparative regimens that would allow engraftment of hematopoietic progenitor cells from either identical or non-identical donors. These reduced-intensity conditioning (RIC) regimens result in less tissue damage, less inflammatory cytokine secretion, and possibly lower rates of graft-versus-host disease (GVHD) and non-relapse mortality (NRM). Such non-myeloablative approach, or "mini-transplant", has been suggested to benefit older patients as well as in conditions in which traditional myeloablative conditioning regimens are associated with high rates of non-relapse mortality. / Allogeneic HSCT is the only curative therapy for many patients with myeloid malignancies or myelodysplastic syndrome (MDS). The development of reduced-intensity preparative regimens may allow the extension of this form of treatment to older and patients with coexisting medical illness. On the other hand, relapse after transplantation remains the most important cause of treatment failure in patients with refractory acute myeloid leukemia (AML) or MDS, and is associated with poor survival. Evaluation of prognostic factors may help to improve the results of myeloablative and RIC allogeneic HSCT in this group of patients. Furthermore, the impact of comorbidities on outcomes of RIC allogeneic HSCT in this group of patients with refractory AML or MDS needs to be defined. / The application of embryonic and adult stem cells in regenerative and reparative therapies of non-hematopoietic diseases is emerging rapidly. Human umbilical cord blood (UCB) is a rich source of hematopoietic stem cells and mesenchymal progenitor cells. Although clinical experience to date with UCB has focused on hematological application, early preclinical studies support the hypothesis that multipotential stem cells derived from UCB exhibit functional characteristics similar to that observed in adult marrow-derived stem cells in mediating vascular and organ regenerative capabilities. However, the application of these preclinical findings in clinical setting needs to be further studied. Mini-transplant of human UCB may be an effective approach to repair organ damage in patients with non-hematological diseases. / Wong Siu Ming Raymond. / Adviser: Joseph J.Y. Sung. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (M.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 187-223). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.

Indiana University-Purdue University Indianapolis (IUPUI) / Human cord blood (CB) derived circulating endothelial colony forming cells (ECFCs) display a hierarchy of clonogenic proliferative potential and possess de novo vessel forming ability upon implantation in immunodeficient mice. Since survival of ECFC post-implantation is a critical variable that limits in vivo vasculogenesis, we tested the hypothesis that activation of Notch signaling or co-implantation of ECFC with human platelet lysate (HPL) would enhance cultured ECFC vasculogenic abilities in vitro and in vivo. Co-implantation of ECFCs with Notch ligand Delta-like 1 (DL1) expressing OP9 stromal cells (OP9-DL1) decreased apoptosis of ECFC in vitro and increased vasculogenesis of ECFC in vivo. The co-culture of ECFC with HPL diminished apoptosis of ECFC by altering the expression of pro-survival molecules (pAkt, pBad and Bcl-xL) in vitro and increased vasculogenesis of human EC-derived vessels both in vitro and in vivo. Thus, activation of the Notch pathway by OP9-DL1 stromal cells or co-implantation of ECFC with HPL enhances vasculogenesis and augments blood vessel formation by diminishing apoptosis of the implanted ECFC. The results from this study will provide critical information for the development of a cell therapy for limb and organ re-vascularization that can be applied to recovery of ischemic tissues in human subjects.