COVID-19 disease in children and adolescents following allogeneic hematopoietic stem cell transplantation: A report from the Turkish pediatric bone marrow transplantation study group

BACKGROUND

Data on the risk factors and outcomes for pediatric patients with SARS-CoV-2 infection (COVID-19) following hematopoietic stem cell transplantation (HSCT) are limited.

OBJECTIVES

The study aimed to analyze the clinical signs, risk factors, and outcomes for ICU admission and mortality in a large pediatric cohort who underwent allogeneic HSCT prior to COVID-19 infection.

METHOD

In this nationwide study, we retrospectively reviewed the data of 184 pediatric HSCT recipients who had COVID-19 between March 2020 and August 2022.

RESULTS

The median time from HSCT to COVID-19 infection was 209.0 days (IQR, 111.7-340.8; range, 0-3845 days). The most common clinical manifestation was fever (58.7%). While most patients (78.8%) had asymptomatic/mild disease, the disease severity was moderate in 9.2% and severe and critical in 4.4% and 7.6%, respectively. The overall mortality was 10.9% (n: 20). Deaths were attributable to COVID-19 in nine (4.9%) patients. Multivariate analysis revealed that lower respiratory tract disease (LRTD) (OR, 23.20, p: .001) and lymphopenia at diagnosis (OR, 5.21, p: .006) were risk factors for ICU admission and that HSCT from a mismatched donor (OR, 54.04, p: .028), multisystem inflammatory syndrome in children (MIS-C) (OR, 31.07, p: .003), and LRTD (OR, 10.11, p: .035) were associated with a higher risk for COVID-19-related mortality.

CONCLUSION

While COVID-19 is mostly asymptomatic or mild in pediatric transplant recipients, it can cause ICU admission in those with LRTD or lymphopenia at diagnosis and may be more fatal in those who are transplanted from a mismatched donor and those who develop MIS-C or LRTD.

MO1015EARLY URINARY SYSTEM COMPLICATIONS IN CHILDREN WITH HEMATOPOETIC STEM CELL TRANSPLANTATION

Background and Aims

Urinary system complications after hematopoietic stem cell transplantation (HSCT) cause severe morbidity and mortality. The aim of the study is to investigate the incidence and risk factors of urinary system complications in patients who had HSCT during their childhood.

Method

Patients who had HSCT between January 2010-2019 with a minimum follow-up period of 6 months were included in the study. Data regarding urinary system complications were collected from the medical records of the patients. pRIFLE and KDIGO classification systems were used for the definition of acute kidney injury (AKI).

Results

167 patients (108 males and 59 females) with allogeneic (n=165) and autologous (n=2) HSCT were investigated for renal complications. In cohort, HSCT was performed in 41 patients (%24.6) secondary to malignant diseases and in 126 patients secondary to non-malignant diseases. Hemorrhagic cystitis (HC) developed in 28 patients (16.8%) after HSCT. The mean age of the patients with and without HC was 14.6±5.6 years and 10.5±6 years, respectively (p=0.044). Among patients with HC, 17 had concomitant viral infection. Presence of viral infection, gender, disease group, history conditioning regime, total body irradiation, acute graft-versus-host disease and veno-occlusive disease (VOD) did not have any effect on the development of HC in logistic regression analysis. In cohort, 126 patients (75.4%) developed AKI according to KDIGO classification (stage 1; 55 patients, stage 2; 36 patients, stage 3; 35 patients). The mean period of development of AKI after HSCT was 34±22 days. The risk of AKI (according to KDIGO) was higher in patients who had HSCT secondary to malignant diseases and/or who developed viral infections after HSCT (p=0.034 and p=0.013, respectively). Among patients, 71 patients (%42.5) developed AKI according to pRIFLE classification. The risk of AKI (according to pRIFLE) was higher in patients who had HSCT secondary to malignant diseases, who developed viral infections and/or who developed VOD during follow-up (p=0.043, p=0.001 and p=0.006, respectively). One patient developed thrombotic microangiopathy after HSCT. None of the patients had nephrotic syndrome during follow-up period.

Conclusion

Patients who had HSCT secondary to malignant disease, viral infections and/or VOD had higher risk of AKI and should be closely monitored.

Stem Cell Applications in Lysosomal Storage Disorders: Progress and Ongoing Challenges

Lysosomal storage disorders (LSDs) are rare inborn errors of metabolism caused by defects in lysosomal function. These diseases are characterized by accumulation of completely or partially degraded substrates in the lysosomes leading to cellular dysfunction of the affected cells. Currently, enzyme replacement therapies (ERTs), treatments directed at substrate reduction (SRT), and hematopoietic stem cell (HSC) transplantation are the only treatment options for LSDs, and the effects of these treatments depend strongly on the type of LSD and the time of initiation of treatment. However, some of the LSDs still lack a durable and curative treatment. Therefore, a variety of novel treatments for LSD patients has been developed in the past few years. However, despite significant progress, the efficacy of some of these treatments remains limited because these therapies are often initiated after irreversible organ damage has occurred.Here, we provide an overview of the known effects of LSDs on stem cell function, as well as a synopsis of available stem cell-based cell and gene therapies that have been/are being developed for the treatment of LSDs. We discuss the advantages and disadvantages of use of hematopoietic stem cell (HSC), mesenchymal stem cell (MSC), and induced pluripotent stem cell (iPSC)-related (gene) therapies. An overview of current research data indicates that when stem cell and/or gene therapy applications are used in combination with existing therapies such as ERT, SRT, and chaperone therapies, promising results can be achieved, showing that these treatments may result in alleviation of existing symptoms and/or prevention of progression of the disease. All together, these studies offer some insight in LSD stem cell biology and provide a hopeful perspective for the use of stem cells. Further development and improvement of these stem cell (gene) combination therapies may greatly improve the current treatment options and outcomes of patients with a LSD.

Characterization of human bone marrow niches with metabolome and transcriptome profiling

Bone marrow (BM) niches are special microenvironments that work in harmony with each other for the regulation and maintenance of hematopoiesis. Niche investigations have thus far been limited to various model organisms and animal studies; therefore, little is known about different niches in healthy humans. In this study, a special harvesting method for the collection of BM from two different anatomical regions in the iliac crest of humans was used to investigate the presence of different niches in BM. Additionally, metabolomic and transcriptomic profiles were compiled using comparative 'omics' technologies, and the main cellular pathways and corresponding transcripts and metabolites were identified. As a result, we found that the energy metabolism between the regions was different. This study provides basic broad data for regenerative medicine in terms of the design of the appropriate microenvironment for in vitro hematopoietic niche modeling, and identifies the normal reference values that can be compared in hematological disease.

Articular Cartilage Regeneration Utilizing Decellularized Human Placental Scaffold, Mesenchymal Stem Cells and Platelet Rich Plasma

BACKGROUND

Articular cartilage repair has been a challenge in orthopedic practice due to the limited self-regenerative capability. Optimal treatment method for cartilage defects has not been defined. We investigated the effect of decellularized human placental (DHP) scaffold, mesenchymal stem cells (MSC) and platelet-rich plasma (PRP) on hyaline cartilage regeneration in a rat model.

METHODS

An osteochondral defect was created in trochlea region of the femur in all groups, bilaterally. No additional procedure was performed in control group (n = 14). Only the DHP scaffold was applied to the P group (n = 14). The DHP scaffold and 1 × 10⁶ MSCs were applied to the PS group (n = 14). The DHP scaffold and PRP were applied to the PP group (n = 14). The DHP scaffold, 1 × 10⁶ MSCs and PRP were applied to the PSP group (n = 14). Outcome measures at 12 weeks included Pineda histology score and qualitative histology.

RESULTS

The mean Pineda scores of P, PS, PP, and PSP groups were significantly better than the control group (p = 0.031, p = 0.002, p < 0.001, p < 0001, respectively). There was no statistically difference in mean Pineda scores of P, PS, PP, and PSP groups (p > 0.05).

CONCLUSION

In conclusion, the DHP scaffold appears to be a promising scaffold on hyaline cartilage regeneration. The augmentation of DHP scaffold with MSCs and PRP combinations did not enhance its efficacy on articular cartilage regeneration.

P1809EARLY URINARY SYSTEM COMPLICATIONS IN CHILDREN WITH HEMATOPOIETIC STEM CELL TRANSPLANTATION

Background and Aims

Urinary system complications after hematopoietic stem cell transplantation (HSCT) cause severe morbidity and mortality. The aim of the study is to investigate the incidence and risk factors of urinary system complications in patients who had HSCT during their childhood.

Method

Patients who had HSCT between January 2010-2019 with a minimum follow-up period of 6 months were included in the study. Data regarding urinary system complications were collected from the medical records of the patients. pRIFLE and KDIGO classification systems were used for the definition of acute kidney injury (AKI).

Results

167 patients (108 males and 59 females) with allogeneic (n=165) and autologous (n=2) HSCT were investigated for renal complications. In cohort, HSCT was performed in 41 patients (%24.6) secondary to malignant diseases and in 126 patients secondary to non-malignant diseases. Hemorrhagic cystitis (HC) developed in 28 patients (16.8%) after HSCT. The mean age of the patients with and without HC was 14.6±5.6 years and 10.5±6 years, respectively (p=0.044). Among patients with HC, 17 had concomitant viral infection. Presence of viral infection, gender, disease group, history conditioning regime, total body irradiation, acute graft-versus-host disease and veno-occlusive disease (VOD) did not have any effect on the development of HC in logistic regression analysis. In cohort, 126 patients (75.4%) developed AKI according to KDIGO classification (stage 1; 55 patients, stage 2; 36 patients, stage 3; 35 patients). The mean period of development of AKI after HSCT was 34±22 days. The risk of AKI (according to KDIGO) was higher in patients who had HSCT secondary to malignant diseases and/or who developed viral infections after HSCT (p=0.034 and p=0.013, respectively). Among patients, 71 patients (%42.5) developed AKI according to pRIFLE classification. The risk of AKI (according to pRIFLE) was higher in patients who had HSCT secondary to malignant diseases, who developed viral infections and/or who developed VOD during follow-up (p=0.043, p=0.001 and p=0.006, respectively). One patient developed thrombotic microangiopathy after HSCT. None of the patients had nephrotic syndrome during follow-up period.

Conclusion

Patients who had HSCT secondary to malignant disease, history of viral infections and/or VOD had higher risk of AKI and should be closely monitored.

P1825ANALYSIS OF LATE RENAL COMPLICATIONS AND RISK FACTORS IN CHILDREN WITH HEMATOPOIETIC STEM CELL TRANSPLANTATION

Background and Aims

The aim of the study is to investigate the incidence and risk factors of hypertension (HT) and chronic kidney disease (CKD) in patients who had hematopoietic stem cell transplantation (HSCT) during their childhood.

Method

Patients who had HSCT between January 2010-2019 with a minimum follow-up period of 6 months were included in the study. Data regarding renal complications were collected from the medical records of the patients. Guidelines of European Society of Hypertension (ESH) and American Academy of Pediatrics (APA) were used for the evaluation of hypertension. 24-hr ambulatory blood pressure monitoring (ABPM) was performed in children older than 5 years of age (68 patients). Ambulatory hypertension is diagnosed when systolic and/or diastolic blood pressure (BP) load is higher than 25%. Ambulatory prehypertension is diagnosed when mean systolic and/or diastolic BP is less than 95th percentile with systolic and/or diastolic BP load higher than 25%.

Results

A total of 72 patients (41 males and 31 females) were included in the study. The mean age of the patients at last visit was 10.8±4 years. ABPM revealed ambulatory HT in 6 patients (8.8%) and ambulatory prehypertension in 12 patients (17.6%). Office BP revealed HT in 3 patients (4.2%) and increased BP in four patients (5.6%) according to APA guideline (2017). In cohort, 12 patients with normal office BP (according to APA guideline) had ambulatory prehypertension or hypertension with ABPM. Office BP revealed HT in 1 patient (1.4%) and high-normal BP in 3 patients (4.2%) according to ESH guideline. In cohort, 15 patients with normal office BP (according to ESH guideline) had ambulatory prehypertension or hypertension with ABPM (Table 1). After a mean follow-up period of 4.4±2.5 years, CKD developed in 8 patients (11.1%). Patients with chronic graft-versus-host disease, with HLA-mismatched HSCT and/or transplantation of peripheric or cord blood hematopoietic stem cells had increased risk of CKD (p=0.041, p=0.033 and p=0.002, respectively).

Conclusion

Patients with HSCT should be regularly followed for the development of HT and ABPM should be used on regular basis. Patients with risk factors should be closely monitored for the development of CKD.

Characterization of mesenchymal stem cells in mucolipidosis type II (I-cell disease)

Mucolipidosis type II (ML-II, I-cell disease) is a fatal inherited lysosomal storage disease caused by a deficiency of the enzyme N-acetylglucosamine-1-phosphotransferase. A characteristic skeletal phenotype is one of the many clinical manifestations of ML-II. Since the mechanisms underlying these skeletal defects in ML-II are not completely understood, we hypothesized that a defect in osteogenic differentiation of ML-II bone marrow mesenchymal stem cells (BM-MSCs) might be responsible for this skeletal phenotype. Here, we assessed and characterized the cellular phenotype of BM-MSCs from a ML-II patient before (BBMT) and after BM transplantation (ABMT), and we compared the results with BM-MSCs from a carrier and a healthy donor. Morphologically, we did not observe differences in ML-II BBMT and ABMT or carrier MSCs in terms of size or granularity. Osteogenic differentiation was not markedly affected by disease or carrier status. Adipogenic differentiation was increased in BBMT ML-II MSCs, but chondrogenic differentiation was decreased in both BBMT and ABMT ML-II MSCs. Immunophenotypically no significant differences were observed between the samples. Interestingly, the proliferative capacity of BBMT and ABMT ML-II MSCs was increased in comparison to MSCs from age-matched healthy donors. These data suggest that MSCs are not likely to cause the skeletal phenotype observed in ML-II, but they may contribute to the pathogenesis of ML-II as a result of lysosomal storage-induced pathology.

Osteopetrotic induced pluripotent stem cells derived from patients with different disease-associated mutations by non-integrating reprogramming methods

BACKGROUND

Autosomal recessive osteopetrosis is a genetically and phenotypically heterogeneous disease, caused by defects in osteoclast formation and function. The only available treatment is allogeneic stem cell transplantation that has still high morbidity and mortality. The goal of the present study was to generate iPSCs from bone marrow-derived MSCs of osteopetrosis patients with three most common mutations by using two different integration-free gene transfer methods and compare their efficiencies. The secondary objective was to select the most appropriate integration-free production method for our institutional iPSC bank using this rare disease as a prototype.

METHODS

Two different integration-free gene transfer methods (episomal and Sendai viral vectors) were tested and compared on the same set of patient samples exhibiting three different mutations associated with osteopetrosis. Generated iPSCs were characterized by standard assays, including immunophenotyping, immunocytochemistry, RT-PCR, embryoid body, and teratoma assays. Karyotype analyses were performed to evaluate genetic stability.

RESULTS

iPSC lines exhibiting typical ESC-like colony morphology were shown to express pluripotency markers by immunofluorescence staining. Over 90% of the cells were found positive for SSEA-4 and OCT3/4 and negative/weak positive for CD29 by flow cytometry. Immunohistochemical staining of teratoma and spontaneously differentiated embryoid body sections confirmed their trilineage differentiation potential. All iPSC lines expressed pluripotency-related genes. Karyotype analyses were found normal. Direct sequencing of PCR-amplified DNA showed that disease-related mutations were retained in the patient-specific iPSCs.

CONCLUSION

Generation of iPSC using SeV and episomal DNA vectors have several advantages over other methods like the ease of production, reliability, high efficiency, and safety, which is required for translational research. Furthermore, owing to the pluripotency and self-renewal capacity, patient-specific iPSCs seem to be ideal cell source for the modeling of a rare genetic bone disease like osteopetrosis to identify osteoclast defects, leading to clinical heterogeneity in osteopetrosis patients, especially among those with different mutations in the same gene.

Additive effect of mesenchymal stem cells and defibrotide in an arterial rat thrombosis model

BACKGROUND/AIM

In this study, we aimed to investigate the additive effect of mesenchymal stem cells (MSC) and defibrotide (DFT) in a rat model of femoral arterial thrombosis.

METHODS

Thirty Sprague Dawley rats were included. An arterial thrombosis model by ferric chloride (FeCl3) was developed in the left femoral artery. The rats were equally assigned to 5 groups: Group 1-Sham-operated (without arterial injury); Group 2-Phosphate buffered saline (PBS) injected; Group 3-MSC; Group 4-DFT; Group 5-MSC + DFT. All had two intraperitoneal injections of 0.5 ml: the 1st injection was 4 h after the procedure and the 2nd one 48 h after the 1st injection. The rats were sacrificed 7 days after the 2nd injection.

RESULTS

Although the use of human bone marrow-derived (hBM) hBM-MSC or DFT alone enabled partial resolution of the thrombus, combining them resulted in near-complete resolution. Neovascularization was two-fold better in hBM-MSC + DFT treated rats (11.6 ± 2.4 channels) compared with the hBM-MSC (3.8 ± 2.7 channels) and DFT groups (5.5 ± 1.8 channels) (P < 0.0001 and P= 0.002, respectively).

CONCLUSION

The combined use of hBM-MSC and DFT in a rat model of arterial thrombosis showed additive effect resulting in near-complete resolution of the thrombus.

Successful Outcome With Fludarabine-Based Conditioning Regimen for Hematopoietic Stem Cell Transplantation From Related Donor in Fanconi Anemia: A Single Center Experience From Turkey

BACKGROUND

Fanconi anemia (FA) is a heterogeneous autosomal recessive (and rarely X linked) disorder, which is characterized by congenital malformations, progressive bone marrow failure, and predisposition to malignancies. Hematopoietic stem cell transplantation (HSCT) is the only definitive treatment for the hematological manifestations in FA.

PROCEDURE

Twenty-seven patients with FA underwent HSCT using fludarabine (Flu) based regimen at our center between April 2004 and May 2014. One patient who developed acute leukemia before HSCT was excluded from the study. The remaining 26 patients were included. The median age of the patients at the time of transplantation was 9.6 years (range 5.6-17.0 years) and male/female ratio was 19/7. Donors were Human leukocyte antigen (HLA)-identical sibling in 18 patients, HLA-identical other relatives in six patients, and HLA 1-antigen mismatched sibling in two patients. Conditioning regimen consisted of Flu, cyclophosphamide, and antithymocyte globulin.

RESULTS

All patients engrafted but one developed poor graft function and underwent second HSCT. Acute graft versus host disease (GVHD) (≥grade 2) occurred in two patients (7.6%) and chronic GVHD in one patient (3.9%). Three patients developed venoocclusive disease (11.5%). Survival rate was 96.2% (25/26) at a median follow-up of 54 months (10-131 months) and all patients who survived were in good clinical condition. None of the patients developed secondary malignancy during the follow-up period.

CONCLUSIONS

The present study from Turkey, a middle-income country, shows successful transplant outcome with low toxicity using Flu-based conditioning in patients with FA who underwent HSCT from HLA-related donors.

Oxidative protein damage with carbonyl levels and nitrotyrosine expression after chemotherapy in bone marrow transplantation patients

Protein oxidation is defined as the covalent modification ofa protein, induced either directly by reactive oxygen species/reactive nitrogen species or indirectly by reaction with secondary by-products of oxidative stress. Protein carbonyls are the most commonly measured products of protein oxidation. Additionally, nitrotyrosine is a product of tyrosine nitration mediated by reactive nitrogen species such as peroxynitrite anion and nitrogen dioxide. Samples were collected before the preparative regimen (10 days before transplantation; day –10), on transplantation day (day 0), and after transplantation (days 7, 14, and 28) from 16 pediatric allogeneic hematopoietic stem cell transplantation (HSCT) patients.The erythrocyte 3-nitrotyrosine expression was shown to be significantly increased after chemotherapy. In accordance, the mean plasma carbonyl levels on days 14 and 28 were significantly higher than on the other days. High dose chemotherapy applied in the preparative regimen of HSCT may be responsible for this long-term oxidation of plasma proteins. These results show that high-dose chemotherapy resulted in protein oxidation both in plasma and in erythrocytes in HSCT patients.

Early detection of pulmonary fungal infection by CT scan in pediatric ALL patients under chemotherapy or in post-transplantation period with primary complaint of chest pain

We describe herein four children with acute lymphoblastic leukemia who were diagnosed as pulmonary fungal infection after presenting with chest pain. The plain radiologic evaluations failed to reveal any positive findings, whereas computerized tomography (CT) scanning showed nodular opacification with or without cavitation. This experience suggests that chest pain may be an initial symptom of an invasive fungal infection in patients with leukemia, and CT scan of the lungs should be performed urgently for the early diagnosis and treatment, despite normal plain X-rays.