ObjectiveThe U6 promoter is an essential element for driving sgRNA expression in the clustered regularly interspaced short palindromic repeat sequences/CRISPR-associated protein 9（CRISPR/Cas9）gene editing system in dicotyledonous plants. Endogenous U6 promoters typically exhibit higher transcriptional activity， which can significantly improve gene editing efficiency. This study aims to identify endogenous U6 promoters in Artemisia annua to optimize its CRISPR/Cas9 gene editing system， which holds significant importance for its molecular breeding. MethodsOn the basis of the highly conserved U6 snRNA sequences in Arabidopsis thaliana， endogenous U6 promoters were screened in the A. annua genome. Expression vectors were constructed with candidate AaU6 promoter driving the firefly luciferase （LUC） reporter gene， and then transiently transformed into Nicotiana benthamiana. Transcriptional activities of the promoters were measured and compared by in vivo imaging and the Dual Luciferase Reporter assay. ResultsEight endogenous U6 promoters were successfully cloned from A. annua. Sequences alignment revealed that all these promoters contained the two conserved cis-acting elements， upstream sequence element （USE） and TATA-box， which affected their transcriptional activity. Dual-luciferase activity assays indicated that the transcriptional activities of AaU6-3， AaU6-1， and AaU6-5 were significantly higher than that of the Arabidopsis AtU6-26 promoter， with AaU6-3 exhibiting the highest activity. ConclusionThis study identified three endogenous AaU6 promoters with high transcriptional activity in A. annua， providing key functional elements for establishing an efficient gene editing system in A. annua. These findings will contribute to advancing precision molecular breeding and high-quality germplasm innovation in A. annua.

Objective:To explore the efficacy and feasibility of hypomethylating agent (HMA) as preventive therapy in children with high-risk acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT).Methods:A retrospective cohort study. Data from 173 children who underwent allo-HSCT for high-risk AML at Children′s Hospital of Soochow University between August 2019 and April 2023 were analyzed. Participants were categorized into a trial group receiving HMA and a control group. Further classification was based on HMA courses:≥4 and <4 courses. The efficacy and safety of HMA preventive treatment after allo-HSCT were evaluated. Survival analysis was performed using the Kaplan-Meier method with Log-Rank testing, the Fine-Gray model was used to assess cumulative relapse rates and Cox regression was used to identify prognostic factors. Adverse events during HMA were descriptively analyzed.Results:Among 173 patients, there were 100 males (57.8%) and 73 females (42.2%), with the age of 81 (34,127) months. The starting time of HMA was 123 (91, 191) d post-transplant, continuing 4.0 (3.0, 6.5) courses and the follow-up period was 24 (13, 32) months. The trial group (53 cases) showed better 2-year overall survival (OS) rate ((88.6±5.6)% vs. (76.6±4.3)%, χ 2=5.00, P=0.025) and relapse-free survival (RFS) rate ((89.2±4.7)% vs. (56.2±4.8)%, χ 2=15.75, P<0.001) than control group (120 cases). The 2-year OS rates and RFS rates were similar between ≥4 courses group (31 cases) and <4 courses group (22 cases)(both P>0.05). The cumulative relapse rate in the trial group was significantly lower ((10.8±0.2)% vs. (35.2±0.2)%, χ 2=10.84, P=0.001) than control group. Among children with molecular relapse, 8 cases (8/30, 26.7%) in the control group had hematological relapse compared to 1 case (1/2) in the trial group ( χ 2=0.81, P=0.369). The differences in incidence of acute and chronic graft-versus-host disease (GVHD) were not statistically significant (all P>0.05). Cox regression analysis revealed that minimal residual disease (MRD) positivity detected by flow cytometry before allo-HSCT and chronic GVHD were independent risk factors for OS (both P<0.05).The HMA preventive treatment was an independent protective factor for RFS, while age ≥10 years and MRD positivity detected by PCR before allo-HSCT were independent risk factors for RFS (all P<0.05). In trial group, 38 cases experienced grade 3 to 4 adverse events (71.7%). Conclusion:HMA is safe as preventive treatment in post-transplant children with high-risk AML, which can reduce the relapse risk and doesn't increase the risk of GVHD.

Objective:To evaluate the efficacy and safety of cord blood stem cell transplantation (CBSCT) in pediatric recipients with mucopolysaccharidosis type Ⅱ (MPS Ⅱ, Hunter syndrome).Methods:Clinical data of five male children with MPS Ⅱ who underwent CBSCT at the Department of Hematology, Children's Hospital of Soochow University between March 2018 and July 2023 were retrospectively analyzed. Post-transplantation clinical outcomes and enzymatic activity were observed. Literature was searched in the China National Knowledge Infrastructure (CNKI), Wanfang, and PubMed databases using the keywords "mucopolysaccharidosis type Ⅱ" "MPS Ⅱ" "IDS gene" and "Hunter syndrome" in both English and Chinese. Articles describing clinical manifestations, genetic diagnosis, and hematopoietic stem cell transplantation (HSCT) in MPS II were screened.Results:All five patients were male, with a median age at diagnosis of 4.3(2.5-5.5) years and a median age at transplantation of 4.6(2.8-6.5) years. At diagnosis, all exhibited coarse facial features, hepatosplenomegaly, skeletal deformities or abnormalities, abnormal head MRI findings, and Mongolian spots; four had joint stiffness, three had valvular heart disease, and two had airway obstruction, short stature, and intellectual disability. Three recipients received single-unit cord blood, and two received double-unit cord blood. Myeloablative conditioning regimens consisted of busulfan, cyclophosphamide, anti-thymocyte globulin ± fludarabine. The median neutrophil engraftment and platelet engraftment times were 19(14-21) days and 26(15-44) days, respectively. Complete donor chimerism was achieved at 1 month post-transplantation. Complications included peri-engraftment syndrome in 5 cases, acute graft-versus-host disease (GVHD) in 2 cases (1 with grade Ⅳ skin and grade Ⅱ intestinal involvement; 1 with grade Ⅱ skin involvement), limited chronic GVHD in 1 case (moderate intestinal involvement), cytomegalovirus (CMV) infection in 3 cases, Epstein-Barr virus (EBV) infection in 1 case, and capillary leak syndrome in 1 case; all were successfully managed. At the last follow-up in December 2023, all patients were alive, and enzyme activity had normalized by 3 months post-transplantation. Most clinical symptoms and signs improved; however, neurocognitive function showed no significant improvement, and some recipients exhibited progressive brain parenchymal changes on MRI. Literature review included 7 English and 5 Chinese studies, indicating that CBSCT and other HSCT modalities can improve multi-system clinical manifestations in MPS Ⅱ children, including restoration of enzyme activity, organ function improvement (such as liver and spleen shrinkage, adenoid reduction), enhanced motor function, and stabilization of neurocognitive function. Some studies suggest superior efficacy compared with enzyme replacement therapy, particularly in delaying disease progression and improving daily living abilities.Conclusion:CBSCT effectively restores enzymatic activity and improves multi-system manifestations in children with MPS Ⅱ, although its effect on neurological symptoms remains controversial. It is a safe and feasible therapeutic option for this condition.

Objective:To explore the efficacy and feasibility of hypomethylating agent (HMA) as preventive therapy in children with high-risk acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT).Methods:A retrospective cohort study. Data from 173 children who underwent allo-HSCT for high-risk AML at Children′s Hospital of Soochow University between August 2019 and April 2023 were analyzed. Participants were categorized into a trial group receiving HMA and a control group. Further classification was based on HMA courses:≥4 and <4 courses. The efficacy and safety of HMA preventive treatment after allo-HSCT were evaluated. Survival analysis was performed using the Kaplan-Meier method with Log-Rank testing, the Fine-Gray model was used to assess cumulative relapse rates and Cox regression was used to identify prognostic factors. Adverse events during HMA were descriptively analyzed.Results:Among 173 patients, there were 100 males (57.8%) and 73 females (42.2%), with the age of 81 (34,127) months. The starting time of HMA was 123 (91, 191) d post-transplant, continuing 4.0 (3.0, 6.5) courses and the follow-up period was 24 (13, 32) months. The trial group (53 cases) showed better 2-year overall survival (OS) rate ((88.6±5.6)% vs. (76.6±4.3)%, χ 2=5.00, P=0.025) and relapse-free survival (RFS) rate ((89.2±4.7)% vs. (56.2±4.8)%, χ 2=15.75, P<0.001) than control group (120 cases). The 2-year OS rates and RFS rates were similar between ≥4 courses group (31 cases) and <4 courses group (22 cases)(both P>0.05). The cumulative relapse rate in the trial group was significantly lower ((10.8±0.2)% vs. (35.2±0.2)%, χ 2=10.84, P=0.001) than control group. Among children with molecular relapse, 8 cases (8/30, 26.7%) in the control group had hematological relapse compared to 1 case (1/2) in the trial group ( χ 2=0.81, P=0.369). The differences in incidence of acute and chronic graft-versus-host disease (GVHD) were not statistically significant (all P>0.05). Cox regression analysis revealed that minimal residual disease (MRD) positivity detected by flow cytometry before allo-HSCT and chronic GVHD were independent risk factors for OS (both P<0.05).The HMA preventive treatment was an independent protective factor for RFS, while age ≥10 years and MRD positivity detected by PCR before allo-HSCT were independent risk factors for RFS (all P<0.05). In trial group, 38 cases experienced grade 3 to 4 adverse events (71.7%). Conclusion:HMA is safe as preventive treatment in post-transplant children with high-risk AML, which can reduce the relapse risk and doesn't increase the risk of GVHD.

Objective:To evaluate the efficacy and safety of cord blood stem cell transplantation (CBSCT) in pediatric recipients with mucopolysaccharidosis type Ⅱ (MPS Ⅱ, Hunter syndrome).Methods:Clinical data of five male children with MPS Ⅱ who underwent CBSCT at the Department of Hematology, Children's Hospital of Soochow University between March 2018 and July 2023 were retrospectively analyzed. Post-transplantation clinical outcomes and enzymatic activity were observed. Literature was searched in the China National Knowledge Infrastructure (CNKI), Wanfang, and PubMed databases using the keywords "mucopolysaccharidosis type Ⅱ" "MPS Ⅱ" "IDS gene" and "Hunter syndrome" in both English and Chinese. Articles describing clinical manifestations, genetic diagnosis, and hematopoietic stem cell transplantation (HSCT) in MPS II were screened.Results:All five patients were male, with a median age at diagnosis of 4.3(2.5-5.5) years and a median age at transplantation of 4.6(2.8-6.5) years. At diagnosis, all exhibited coarse facial features, hepatosplenomegaly, skeletal deformities or abnormalities, abnormal head MRI findings, and Mongolian spots; four had joint stiffness, three had valvular heart disease, and two had airway obstruction, short stature, and intellectual disability. Three recipients received single-unit cord blood, and two received double-unit cord blood. Myeloablative conditioning regimens consisted of busulfan, cyclophosphamide, anti-thymocyte globulin ± fludarabine. The median neutrophil engraftment and platelet engraftment times were 19(14-21) days and 26(15-44) days, respectively. Complete donor chimerism was achieved at 1 month post-transplantation. Complications included peri-engraftment syndrome in 5 cases, acute graft-versus-host disease (GVHD) in 2 cases (1 with grade Ⅳ skin and grade Ⅱ intestinal involvement; 1 with grade Ⅱ skin involvement), limited chronic GVHD in 1 case (moderate intestinal involvement), cytomegalovirus (CMV) infection in 3 cases, Epstein-Barr virus (EBV) infection in 1 case, and capillary leak syndrome in 1 case; all were successfully managed. At the last follow-up in December 2023, all patients were alive, and enzyme activity had normalized by 3 months post-transplantation. Most clinical symptoms and signs improved; however, neurocognitive function showed no significant improvement, and some recipients exhibited progressive brain parenchymal changes on MRI. Literature review included 7 English and 5 Chinese studies, indicating that CBSCT and other HSCT modalities can improve multi-system clinical manifestations in MPS Ⅱ children, including restoration of enzyme activity, organ function improvement (such as liver and spleen shrinkage, adenoid reduction), enhanced motor function, and stabilization of neurocognitive function. Some studies suggest superior efficacy compared with enzyme replacement therapy, particularly in delaying disease progression and improving daily living abilities.Conclusion:CBSCT effectively restores enzymatic activity and improves multi-system manifestations in children with MPS Ⅱ, although its effect on neurological symptoms remains controversial. It is a safe and feasible therapeutic option for this condition.