Search

Correction for 'Design, development, testing at ISO standards and in vivo feasibility study of a novel polymeric heart valve prosthesis' by Joanna R. Stasiak et al., Biomater. Sci., 2020, DOI: .

Clinically available prosthetic heart valves are life-saving, but imperfect: mechanical valves requiring anticoagulation therapy, whilst bioprosthetic valves have limited durability. Polymer valves offer the prospect of good durability without the need for anticoagulation. We report the design and development of a polymeric heart valve, its bench-testing at ISO standards, and preliminary extra-vivo and in vivo short-term feasibility. Prototypes were manufactured by injection moulding of styrenic block copolymers to achieve anisotropic mechanical properties. Design was by finite element stress-strain modelling, which has been reported previously, combined with feedback from bench and surgery-based testing using various combinations of materials, valve geometry and processing conditions. Bench testing was according to ISO 5840:2015 standards using an in vitro cardiovascular hydrodynamic testing system and an accelerated fatigue tester. Bench comparisons were made with a best-in-class bio-prosthesis. Preliminary clinical feasibility evaluations included extra-vivo and short-term (1-24 hours) in vivo testing in a sheep model. The optimised final prototype met the requirements of ISO standards with hydrodynamic performance equivalent to the best-in-class bioprosthesis. Bench durability of greater than 1.2 billion cycles (30 years equivalent) was achieved (still ongoing). Extra-vivo sequential testing (n = 8) allowed refinement of external diameter, 3D shape, a low profile, flexibility, suturability, and testing of compatibility to magnetic resonance imaging and clinical sterilisation. In vivo short-term (1-24 hours) feasibility (n = 3) confirmed good suturability, no mechanical failure, no trans-valvular regurgitation, competitive trans-valvular gradients, and good biocompatibility at histopathology. We have developed and tested at ISO standards a novel prosthetic heart valve featuring competitive bench-based hydrodynamics and durability, well beyond the ISO requirements and comparable to a best-in-class bioprosthesis. In vivo short-term feasibility testing confirmed preliminary safety, functionality and biocompatibility, supporting progression to a long-term efficacy trial.

a-GvHD may complicate allogeneic HSCT. In this retrospective single-center study, we evaluated incidence and risk factors of a-GvHD in 197 consecutive allogeneic pediatric HSCTs applying Glucksberg and NIH a-GvHD classifications. Among 179 eligible transplants, the cumulative incidence of grade 0-I a-GvHD was 48% and grade II-IV was 52%. None of the considered variables significantly influenced the incidence of grade II-IV a-GvHD. Malignancy and myeloablation were associated with an increased risk of classic a-GvHD (p < 0.01). Seventy-two percentage of children are alive, with a significant difference in OS and TRM between grade 0 and I vs. grade II and IV a-GvHD; this observation was reproduced in the non-malignant setting, while only a disparity in TRM was evidenced in children with malignancy. In our experience, the incidence of a-GvHD was similar, regardless of donor type. Myeloablation and malignant disease represented the only risk factors for classic a-GvHD. Our results highlight the need for a better prevention of this complication in the non-malignant setting., (© 2012 John Wiley & Sons A/S.)

Pulmonary infections often complicate hematopoietic stem cell transplantation (HSCT) outcome. Uncommon aetiologies, like Mycobacterium tuberculosis, should be considered when the clinical conditions do not fully improve with standard antimicrobial therapy and microbiological evaluations are repeatedly negative for bacteria and fungi. We describe an interesting pediatric case of miliary lung tuberculosis after HSCT, which was successfully treated after administering the appropriate therapy.

Acute lymphoblastic leukemia (ALL) in second complete remission is one of the most common indications for allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric patients. We compared the outcome after HCST of adolescents, aged 14 to 18 years, with that of children (ie, patients < 14 years of age). Enrolled in the study were 395 patients given the allograft between January 1990 and December 2007; both children (334) and adolescents (61) were transplanted in the same pediatric institutions. All patients received a myeloablative regimen that included total body irradiation in the majority of them. The donor was an HLA-identical sibling for 199 patients and an unrelated volunteer in the remaining 196 patients. Children and adolescents had a comparable cumulative incidence of transplantation-related mortality, disease recurrence, and of both acute and chronic graft-versus-host disease. The 10-year probability of overall survival and event-free survival for the whole cohort of patients were 57% (95% confidence interval, 52%-62%) and 54% (95% confidence interval, 49%-59%), respectively, with no difference between children and adolescents. This study documents that adolescents with ALL in second complete remission given HSCT in pediatric centers have an outcome that does not differ from that of patients younger than 14 years of age.

β-Thalassemia is a severe inherited anemia caused by insufficient production of β-globin chains. Allogeneic hematopoietic stem cell (HSC) transplantation is currently the only cure, and is limited by donor availability and regimen-related toxicity and mortality. Gene therapy is a promising therapeutic tool for all thalassemic patients lacking a compatible donor and potentially provides transfusion independence in the absence of transplant-related complications, such as graft rejection and graft-versus-host disease. The issue of HSC procurement is critical in this setting because of the specific features of thalassemic syndromes, which include bone marrow (BM) expansion, ineffective erythropoiesis, and splenomegaly. Little is known about the efficiency of CD34(+) cell yield from steady-state BM harvests from thalassemic patients. We have collected data on safety and cell yield from 20 pediatric patients with β-thalassemia who underwent autologous BM harvest before allogeneic HSC transplantation, and from 49 age-matched sibling donors who also underwent BM harvest. The procedure was safe, as no significant adverse events occurred. In terms of cell yield, no difference was found between patients and normal donors in the number of CD34(+) cells and total nucleated cells harvested. Most importantly, no difference was found in the proportion of myeloid and erythroid progenitors, suggesting a similar repopulating capacity. On the basis of these results, we conclude that steady-state BM can be used as a safe and efficient source of HSC for gene therapy of β-thalassemia.

Beta-thalassemia is a common monogenic disorder due to mutations in the beta-globin gene and gene therapy, based on autologous transplantation of genetically corrected haematopoietic stem cells (HSCs), holds the promise to treat patients lacking a compatible bone marrow (BM) donor. We recently showed correction of murine beta-thalassemia by gene transfer in HSCs with the GLOBE lentiviral vector (LV), expressing a transcriptionally regulated human beta-globin gene. Here, we report successful correction of thalassemia major in human cells, by studying a large cohort of pediatric patients of diverse ethnic origin, carriers of different mutations and all candidates to BM transplantation. Extensive characterization of BM-derived CD34(+) cells before and following gene transfer shows the achievement of high frequency of transduction, restoration of haemoglobin A synthesis, rescue from apoptosis and correction of ineffective erythropoiesis. The procedure does not significantly affect the differentiating potential and the relative proportion of haematopoietic progenitors. Analysis of vector integrations shows preferential targeting of transcriptionally active regions, without bias for cancer-related genes. Overall, these results provide a solid rationale for a future clinical translation.

Recently vancomycin-resistant and sporadically linezolid-resistant Enterococcus species have been described in adults. We report what we believe to be the first case of a child with prolonged bone marrow aplasia following haematopoietic stem cell transplantation developing a fatal sepsis caused by Enterococcus faecium resistant to glycopeptides and linezolid.

Mixed chimerism (MC) and secondary graft failure are frequent events following SCT for thalassemia. There is limited information regarding the outcome of donor lymphocyte infusion (DLI) to prevent rejection, mainly from case reports describing only successful cases. We describe a series of seven children affected by beta-thalassemia treated with escalating doses of DLI for level 2-3 MC (donor<90%) following myeloablative SCT from a matched family donor. The infusions were safe and no acute or chronic GVHD were documented; five patients experienced neutropenia and thrombocytopenia resolving spontaneously. DLI was successful in converting to full donor chimerism two patients stratified in the low-risk class (Pesaro class II). Conversely, for five high-risk patients, DLI was not effective in preventing secondary graft failure. This limited series suggests that escalating doses of DLI are safe in thalassemia patients post myeloablative therapy but efficacy may be jeopardized by rapidly growing anti-donor alloimmunity in high-risk patients. We suggest giving escalating doses of donor T cells to attempt a graft-versus-thalassemia as soon as level 2-3 MC is detected.

beta-thalassemia is a major health problem worldwide, and stem cell transplantation (SCT) is the only curative option. Oral Busulfan (Bu) based conditioning is widely used in this setting. Due to the variability of Bu systemic exposure, intravenous (i.v.) Bu has been proposed as a standard of care, with no need for drug monitoring and dose adjustment. Patients with beta-thalassemia from countries with limited resources might be at higher risk of erratic Bu metabolism because of liver dysfunction, severe iron overload, and specific ethnic/genetic features. We studied Bu pharmacokinetics in 53 children with advanced beta-thalassemia from Middle Eastern countries who underwent a total of 57 matched related donor SCTs. Forty-two percent of the children required dose adjustment because they did not achieve the therapeutic window after the first dose. With a Bu dose-adjustment policy, regimen-related toxicity was limited. At a median follow-up of 564 days, the probabilities of 2-year survival, current thalassemia-free survival, rejection, and treatment-related mortality were 96%, 88%, 21%, and 4%, respectively. Conditioning with i.v. Bu and dose adjustment is feasible and well tolerated, although recurrence of thalassemia remains an unsolved problem in children with advanced disease., (Copyright 2010 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Background: Neurotoxicity is a recognized complication of cyclosporine A (CSA) treatment. The incidence of severe CSA-related neurological complications following hematopoietic stem cell transplantation (HSCT) is 4-11%., Methods: We describe 6 cases of CSA related neurotoxicity out of 67 matched related HSCT performed in paediatric Middle East patients affected by haemoglobinopaties (5 beta thalassemia major, 1 sickle cell disease-SCD). Conditioning regimen consisted of iv busulphan, cyclophosphamide and graft-versus-host-disease (GvHD) prophylaxis with CSA, methylprednisolone, methotrexate and ATG., Results: All 6 patients presented prodromes such as arterial hypertension, headache, visual disturbances and vomiting, one to two days before overt CSA neurotoxicity. CSA neurotoxicity consisted of generalized seizures, signs of endocranial hypertension and visual disturbances at a median day of onset of 11 days after HSCT (range +1 to +40). Brain magnetic resonance imaging (MRI) performed in all subjects showed reversible leukoencephalopathy predominantly in the posterior regions of the brain (PRES) in 5/6 patients. EEG performed in 5/6 patients was always abnormal. Neurotoxicity was not explainable by high CSA blood levels, as all patients had CSA in the therapeutic range with a median of 178 ng/ml (range 69-250). CSA was promptly stopped and switched to tacrolimus with disappearance of clinical and radiological findings. All patients are symptoms-free at a median follow up of 882 days (range 60-1065)., Conclusions: Our experience suggests that paediatric patients with haemoglobinopaties have a high incidence of CSA related neurological events with no correlation between serum CSA levels and neurotoxicity. Prognosis is good following CSA removal. Specific prodromes such as arterial hypertension, headache or visual disturbances occurring in the early post-transplant period should be carefully evaluated with electrophysiological and MRI-based imaging in order to intervene promptly and avoid irreversible sequels.

Hepatic veno-occlusive disease (VOD) is a common complication of haematopoietic stem cell transplantation (HSCT), with reported incidences of 5-40% in children. Recently, defibrotide (DF) has been successfully used as prophylaxis and treatment of VOD. This study reports data on 63 human leucocyte antigen-matched HSCT performed in 57 children affected by beta thalassemia at very high risk for developing VOD (liver fibrosis, iron overload, hepatitis C virus infections, busulphan-based conditioning, methotraexate + ciclosporine). All patients received a busulphan-based conditioning regimen, either orally (four HSCT) or intravenously (59 HSCT). All patients received oral DF (40 mg/kg per day, final dose) as VOD prophylaxis from median day -9 to median day +29. In order to overcome the lack of oral paediatric formulations, a galenic formulation was administered. DF was well tolerated. Only one patient fulfilled Seattle Criteria for VOD diagnosis. This patient had discontinued DF 6 d prior to VOD onset, due to high risk of haemorrhage. We concluded that oral defibrotide prophylaxis and i.v. busulphan safely abated VOD incidence in high-risk patients who had undergone HSCT. A galenic preparation of oral DF also permits this treatment in low-weight patients. Costs of DF prophylaxis are acceptable considering the reduced incidence of VOD.

Gene transfer into hematopoietic stem cells by gamma-retroviral vectors (RVs) is an effective treatment for inherited blood disorders, although potentially limited by the risk of insertional mutagenesis. We evaluated the genomic impact of RV integration in T lymphocytes from adenosine deaminase-deficient severe combined immunodeficiency (ADA-SCID) patients 10 to 30 months after infusion of autologous, genetically corrected CD34(+) cells. Expression profiling on ex vivo T-cell bulk population revealed no difference with respect to healthy controls. To assess the effect of vector integration on gene expression at the single-cell level, primary T-cell clones were isolated from 2 patients. T-cell clones harbored either 1 (89.8%) or 2 (10.2%) vector copies per cell and displayed partial to full correction of ADA expression, purine metabolism, and T-cell receptor-driven functions. Analysis of RV integration sites indicated a high diversity in T-cell origin, consistently with the polyclonal T-cell receptor-Vbeta repertoire. Quantitative transcript analysis of 120 genes within a 200-kb window around RV integration sites showed modest (2.8- to 5.2-fold) dysregulation of 5.8% genes in 18.6% of the T-cell clones compared with controls. Nonetheless, affected clones maintained a stable phenotype and normal in vitro functions. These results confirm that RV-mediated gene transfer for ADA-SCID is safe, and provide crucial information for the development of future gene therapy protocols. The trials described herein have been registered at http://www.clinicaltrials.gov as #NCT00598481 and #NCT00599781.

Background: Thalassemia major can be cured with allogeneic hematopoietic stem cell transplantation. Persistent mixed chimerism develops in around 10% of transplanted thalassemic patients, but the biological mechanisms underlying this phenomenon are poorly understood., Design and Methods: The presence of interleukin-10-producing T cells in the peripheral blood of eight patients with persistent mixed chimerism and five with full donor chimerism was investigated. A detailed characterization was then performed, by T-cell cloning, of the effector and regulatory T-cell repertoire of one patient with persistent mixed chimerism, who developed stable split erythroid/lymphoid chimerism after a hematopoietic stem cell transplant from an HLA-matched unrelated donor., Results: Higher levels of interleukin-10 were produced by peripheral blood mononuclear cells from patients with persistent mixed chimerism than by the same cells from patients with complete donor chimerism or normal donors. T-cell clones of both host and donor origin could be isolated from the peripheral blood of one, selected patient with persistent mixed chimerism. Together with effector T-cell clones reactive against host or donor alloantigens, regulatory T-cell clones with a cytokine secretion profile typical of type 1 regulatory cells were identified at high frequencies. Type 1 regulatory cell clones, of both donor and host origin, were able to inhibit the function of effector T cells of either donor or host origin in vitro., Conclusions: Overall these results suggest that interleukin-10 and type 1 regulatory cells are associated with persistent mixed chimerism and may play an important role in sustaining long-term tolerance in vivo. These data provide new insights into the mechanisms of peripheral tolerance in chimeric patients and support the use of cellular therapy with regulatory T cells following hematopoietic stem cell transplantation.

Allogeneic BMT represents the only chance of cure for beta-thalassemia. Occasionally, two affected individuals from the same family share a matched healthy sibling. Moreover, a high incidence of transplant rejection is still observed in Pesaro class III patients, requiring a second BMT procedure. In these settings, one option is to perform a second BM harvest from the same donor. Although BM harvest is a safe procedure in children, ethical issues concerning this invasive practice still arise. Here, we describe our series of seven pediatric, healthy donors, who donated BM more than once in favor of their beta-thalassemic HLA-identical siblings between June 2005 and January 2008. Three donors donated BM twice to two affected siblings and four donors donated twice for the same sibling following graft rejection of the first BMT. All donors tolerated the procedures well and no relevant side effects occurred. There was no significant difference between the two harvests concerning cell yield and time to engraftment. Our experience shows that for pediatric donors, a second BM donation is safe and feasible and good cellularity can be obtained. We suggest that a second harvest of a pediatric donor can be performed when a strong indication for BMT exists.