Photothermally Heated Asymmetric Thin Nanopores Suggest the Influence of Temperature on the Intermediate Conformational State of Cytochrome c in an Electric Field.

Nanopore sensing is a label-free single-molecule technique that enables the study of the dynamical structural properties of proteins. Here, we detect the translocation of cytochrome c (Cyt c) through an asymmetric thin nanopore with photothermal heating to evaluate the influence of temperature on Cyt c conformation during its translocation in an electric field. Before Cyt c translocates through an asymmetric thin SiNx nanopore, ∼1 ms trapping events occur due to electric field-induced denaturation. These trapping events were corroborated by a control analysis with a transmission electron microscopy-drilled pore and denaturant buffer. Cyt c translocation events exhibited markedly greater broad current blockade when the pores were photothermally heated. Collectively, our molecular dynamics simulation predicted that an increased temperature facilitates denaturation of the α-helical structure of Cyt c, resulting in greater blockade current during Cyt c trapping. Our photothermal heating method can be used to study the influence of temperature on protein conformation at the single-molecule level in a label-free manner.

Significance of absolute neutrophil count before allogeneic hematopoietic stem cell transplantation in adult patients with aplastic anemia.

The impact of absolute neutrophil count (ANC) before allogenic hematopoietic stem cell transplantation (HSCT) on the outcomes for patients with aplastic anemia (AA) remains unclear. We retrospectively evaluated the relationship between ANC before transplantation and patient outcomes, involving 883 adult Japanese patients with AA who underwent allogeneic HSCT as their first transplantation between 2008 and 2020. Patients were divided into three groups based on ANC: 0/µL (n = 116); 1-199 (n = 210); and ≥ 200 (n = 557). In the low ANC groups (ANC < 200), patient age was higher, previous anti-thymocyte globulin (ATG) treatments were infrequent, duration from diagnosis to transplantation was shorter, hematopoietic cell transplantation-comorbidity index (HCT-CI) was higher, ATG-based conditioning was used infrequently, and peripheral blood stem cell from related donor and cord blood were used frequently. In multivariate analysis, patient age, previous ATG treatment, HCT-CI, stem cell source, and ANC before transplantation were significantly associated with 5-year overall survival (OS) ("ANC ≥ 200": 80.3% vs. "ANC 1-199": 71.7% vs. "ANC 0": 64.4%). The cumulative incidence of bacterial infection, invasive fungal disease, and early death before engraftment were significantly higher in the low ANC groups. Among patients with ANC of zero before transplantation, younger patient age, shorter duration from diagnosis to transplantation, HCT-CI of 0, and bone marrow from related donor as stem cell source were significantly associated with better OS. Consequently, ANC before allogeneic HSCT was found to be a significant prognostic factor in adult patients with AA. Physicians should pay attention to ANC before transplantation.

Electrical unfolding of cytochrome c during translocation through a nanopore constriction.

Many small proteins move across cellular compartments through narrow pores. In order to thread a protein through a constriction, free energy must be overcome to either deform or completely unfold the protein. In principle, the diameter of the pore, along with the effective driving force for unfolding the protein, as well as its barrier to translocation, should be critical factors that govern whether the process proceeds via squeezing, unfolding/threading, or both. To probe this for a well-established protein system, we studied the electric-field-driven translocation behavior of cytochrome c (cyt c) through ultrathin silicon nitride (SiNx) solid-state nanopores of diameters ranging from 1.5 to 5.5 nm. For a 2.5-nm-diameter pore, we find that, in a threshold electric-field regime of ∼30 to 100 MV/m, cyt c is able to squeeze through the pore. As electric fields inside the pore are increased, the unfolded state of cyt c is thermodynamically stabilized, facilitating its translocation. In contrast, for 1.5- and 2.0-nm-diameter pores, translocation occurs only by threading of the fully unfolded protein after it transitions through a higher energy unfolding intermediate state at the mouth of the pore. The relative energies between the metastable, intermediate, and unfolded protein states are extracted using a simple thermodynamic model that is dictated by the relatively slow (∼ms) protein translocation times for passing through the nanopore. These experiments map the various modes of protein translocation through a constriction, which opens avenues for exploring protein folding structures, internal contacts, and electric-field-induced deformability.

[Reference guide for the treatment of aplastic anemia: key points of the 2022 revision].

The "Reference Guide for the Treatment of Aplastic Anemia" has been revised for the first time in 3 years, and clinical questions have been formulated for the first time. As research demonstrated a benefit to combining antithymocyte globulin (ATG) and cyclosporine with eltrombopag (EPAG), the revised guide recommends that EPAG be started as soon as possible after ATG administration. In addition, it states that starting with immunosuppressive therapy and performing allogeneic bone marrow transplantation in the event of inadequate response or relapse is an option even for young adult patients with severe aplastic anemia who have HLA-matched allogeneic bone marrow donor candidates. The guide also discusses aggressive treatment of non-severe cases, ATG dosage and the maximum age for ATG administration, infection prevention, and G-CSF administration. It is necessary to continue collecting evidence and promoting clinical trials to build evidence in Japan.

Total body irradiation-containing conditioning regimens without antithymocyte globulin in adults with aplastic anemia undergoing umbilical cord blood transplantation.

Thus far, there have been no large cohort studies on total body irradiation (TBI)-containing conditioning regimens without antithymocyte globulin (ATG) in adults with aplastic anemia (AA) undergoing umbilical cord blood (UCB) transplantation (UCBT). We retrospectively analyzed 115 adults with idiopathic AA undergoing UCBT using TBI-containing reduced-intensity conditioning (RIC) regimens without ATG between 2000 and 2018 on behalf of the Adult Aplastic Anemia Working Group of the Japanese Society for Hematopoietic Cell Transplantation. We then compared transplantation outcomes between a fludarabine (Flu)- and melphalan (Mel)-based regimen (FM) and a Flu- and cyclophosphamide (Cy)-based regimen (FC). The median patient age at UCBT was 41 years. The median total nucleated cell and total CD34+ cell doses in a UCB unit at cryopreservation were 2.5 × 107/kg and 0.7 × 105/kg, respectively. The median follow-up period for survivors was 47 months. The cumulative incidence rate of neutrophil engraftment was 76.5%, and the 4-year overall survival (OS) rate was 64.3%. In multivariate analysis, the covariates that were significantly associated with a higher neutrophil engraftment were total CD34+ cell dose in an UCB unit (≥ 0.7 × 105/kg; hazard ratio, 0.57, P = 0.01) and total dose of TBI (4 Gy of TBI; hazard ratio, 0.32, P = 0.01). There was no significant difference in the cumulative incidence of neutrophil engraftment and the 4-year OS between the FM and FC groups. In conclusion, TBI-containing RIC regimens without ATG are suitable for adults with AA undergoing UCBT. There were no significant differences in transplantation outcomes between the FM and FC groups.

The effectiveness of immunosuppressive therapy in patients with aplastic anaemia secondary to chemoradiotherapy for cancers.

The outcome of immunosuppressive therapy (IST) and prognosis in patients with aplastic anaemia (AA) secondary to chemotherapy or radiotherapy for cancers remains unknown. A total of 43 of 2559 patients with AA referred to our hospital had previously received chemoradiotherapy for various types of solid tumours (n = 25) or haematological malignancies (n = 18). Their cancer status was complete remission (CR) in 27, non-CR in 13, and unknown in three. Small populations of glycosylphosphatidylinositol-anchored protein-deficient [GPI(-)] granulocytes were detected in 16 patients (37·2%). Of 18 patients who were treated with IST, 50% improved regardless of the presence of GPI(-) cells. The overall survival (OS) rate was significantly higher in patients with a history of solid tumours patients than in those of haematological malignancies (median OS, 87 vs. 11 months, P = 0·0003), and in patients treated with IST than in those of untreated patients (median OS, 115 vs. 20 months, P = 0·028). Cancer aggravation occurred in two of four patients who were treated with IST while in non-CR of their original cancers. Progression to myelodysplastic syndromes was observed in two patients not possessing GPI(-) cells. IST should thus be considered for patients with AA secondary to chemoradiotherapy for cancers, particularly when their original solid tumours are in CR.

Cyclosporine/methotrexate versus tacrolimus/methotrexate with or without anti-thymocyte globulin as GVHD prophylaxis in adult patients with aplastic anemia.

The impact of calcineurin inhibitor types and anti-thymocyte globulin (ATG) in conditioning on overall survival (OS) and GVHD-free, relapse-free survival (GRFS) has not yet been analyzed in detail for aplastic anemia. We herein examined 517 adult patients with aplastic anemia who underwent BMT from HLA-matched sibling donors (MSD, n = 255) and unrelated donors (UD, n = 262) and were treated with cyclosporine A (CSA) + methotrexate (MTX) (n = 258) and tacrolimus (TAC) + MTX (n = 259). In total, 330 patients received ATG in conditioning. CSA + MTX versus TAC + MTX did not have a significant impact on acute and chronic GVHD, OS, or GRFS in each donor type. The use of ATG in conditioning reduced the risk of grade II-IV acute GVHD in the MSD and UD cohorts (HR 0.42, P = 0.014, and HR 0.3, P < 0.001, respectively); however, a differential impact on GRFS was identified, namely, better GRFS in MSD recipients (HR 0.56, P = 0.016), but not in UD recipients (HR 1.1, P = 0.657). In conclusion, CSA + MTX and TAC + MTX were similar as GVHD prophylaxis regardless of the donor type, and ATG in conditioning increased GRFS in MSD transplants, but not in UD transplants.

Relationship between plasma rabbit anti-thymocyte globulin concentration and immunosuppressive therapy response in patients with severe aplastic anemia.

OBJECTIVES: Patients with acquired aplastic anemia (AA) without HLA-matched sibling donors or aged >40 years receive immunosuppressive therapy (IST) with anti-thymocyte globulin (ATG). We investigated the relationship between plasma rabbit ATG (r-ATG) concentration and IST response. METHODS: From May 2012 to October 2017, 81 patients with severe AA who required initial IST were included. A 1:1 block randomization was employed for 2.5 and 3.5 mg/kg doses of r-ATG. RESULTS: No significant difference in response rates was observed between the 2.5 and 3.5 mg/kg groups (63% vs. 58%, P = .894). Median r-ATG concentrations on days 14 and 28 after IST were 15.2 (0.0-97.7) and 1.8 (0.0-74.9 µg/mL), respectively. According to r-ATG concentration, response rates were significantly higher in the group with higher r-ATG concentration than in those with lower r-ATG concentration (day 14, 88% vs. 52%; P = .006 and day 28, 79% vs. 46%; P = .005). In multivariate analysis, higher r-ATG concentrations at day 28 were independent predictors of favorable response to IST at 6 months (odds ratio, 0.29; 95% confidence interval, 0.09-0.93; P = .037). CONCLUSIONS: The present data indicate that higher r-ATG concentration at day 28 resulted in improved IST response.

Rosette Nanotube Porins as Ion Selective Transporters and Single-Molecule Sensors.

Rosette nanotubes (RNTs) are a class of materials formed by molecular self-assembly of a fused guanine-cytosine base (G∧C base). An important feature of these self-assembled nanotubes is their precise atomic structure, intriguing for rational design and optimization as synthetic transmembrane porins. Here, we present experimental observations of ion transport across 1.1 nm inner diameter RNT porins (RNTPs) of various lengths in the range 5-200 nm. In a typical experiment, custom lipophilic RNTPs were first inserted into lipid vesicles; the vesicles then spontaneously fused with a planar lipid bilayer, which produced stepwise increases of ion current across the bilayer. Our measurements in 1 M KCl solution indicate ion transport rates of ∼50 ions s-1 V-1 m, which for short channels amounts to conductance values of ∼1 nS, commensurate with naturally occurring toxin channels such as α-hemolysin. Measurements of interaction times of α-cyclodextrin with RNTPs reveal two distinct unbinding time scales, which suggest that interactions of either face of α-cyclodextrin with the RNTP face are differentiable, backed with all-atom molecular dynamics simulations. Our results highlight the potential of RNTPs as self-assembled nonproteinaceous single-molecule sensors and selective nanofilters with tunable functionality through chemistry.

Mixed Chimerism and Secondary Graft Failure in Allogeneic Hematopoietic Stem Cell Transplantation for Aplastic Anemia.

Mixed chimerism (MC) and/or secondary graft failure (SGF) with recipient- or donor-type chimerism is a major obstacle in allogeneic transplantation for aplastic anemia (AA). From a registry database in Japan, patients with AA age >15 years who underwent a first allogeneic bone marrow or peripheral blood stem cell transplantation between 2000 and 2014 and achieved engraftment were included in this study. MC that did not require either granulocyte-colony stimulating factor (G-CSF) or transfusion support (group 1), MC (not SGF) that required G-CSF and/or transfusion support (group 2), SGF with MC or complete recipient-type chimerism (group 3), and SGF with complete donor-type chimerism (group 4) developed in 26, 16, 19, and 17 patients, respectively. The overall median duration of follow-up for survivors was 1727 days. The overall survival (OS) was 90.4% at 1 year and 83.5% at 5 years in patients without MC or SGF (n = 340), which was not different from the OS in groups 1 and 2. However, inferior OS was observed in group 3 (1 year, 52.1%; 5 years, 52.1%) and group 4 (1 year, 82.4%; 5 years, 56.3%). In multivariate analyses, the use of fludarabine (Flu) and the absence of irradiation in conditioning were associated with the development of SGF with MC or complete recipient-type chimerism, and the use of Flu in conditioning was associated with SGF with complete donor-type chimerism. In conclusion, the use of Flu may affect the occurrence of SGF with both recipient-type and donor-type chimerism.

Plasmonic Nanopores for Single-Molecule Detection and Manipulation: Toward Sequencing Applications.

Solid-state nanopore-based sensors are promising platforms for next-generation sequencing technologies, featuring label-free single-molecule sensitivity, rapid detection, and low-cost manufacturing. In recent years, solid-state nanopores have been explored due to their miscellaneous fabrication methods and their use in a wide range of sensing applications. Here, we highlight a novel family of solid-state nanopores which have recently appeared, namely plasmonic nanopores. The use of plasmonic nanopores to engineer electromagnetic fields around a nanopore sensor allows for enhanced optical spectroscopies, local control over temperature, thermophoresis of molecules and ions to/from the sensor, and trapping of entities. This Mini Review offers a comprehensive understanding of the current state-of-the-art plasmonic nanopores for single-molecule detection and biomolecular sequencing applications and discusses the latest advances and future perspectives on plasmonic nanopore-based technologies.

Prospective randomized trial comparing two doses of rabbit anti-thymocyte globulin in patients with severe aplastic anaemia.

The treatment of choice for patients with severe aplastic anaemia (SAA) includes immunosuppressive therapy (IST) with anti-thymocyte globulin (ATG) and ciclosporin A. However, the optimal dose for rabbit ATG has yet to be established. We herein report the first prospective, randomized, multicentre study comparing two doses of rabbit ATG in patients with SAA. Patients with SAA who required initial IST in Japan (n = 89), China (n = 85) and Korea (n = 48) were enrolled between May 2012 and October 2017. A 1:1 block randomization was employed for two doses of rabbit ATG. In total, 222 patients were randomized, with 112 patients receiving 2·5 mg/kg and 110 receiving 3·5 mg/kg of rabbit ATG for 5 days. The primary endpoint was the haematological response at day 180. After 6 months, no significant difference in response rates was observed between the 2·5 and 3·5 mg/kg groups (49% vs. 48%, P = 0·894). Overall survival at 3 years was similar between the two groups [85% (95% confidence interval [CI], 76%-91%) vs. 91% (95% CI, 82%-96%); P = 0·107]. The current study revealed no significant differences in the efficacy and safety between the 2·5 and 3·5 mg/kg doses of rabbit ATG in patients with SAA. Trial registration: UMIN000011134.

Electro-osmotic trapping and compression of single DNA molecules while passing through a nanopore.

Complicated DNA molecular behaviors exist during translocation into a nanopore because their large and coiled structure needs to unwind. In this work, we investigated DNA translocation dynamics through a 200 nm pore using a fast photon counting system (FPCS). We found that the dwell time of the DNA molecules depends on the inverse of voltage (τ∝V-1.02) with a large constant term (∼1 ms). In other words, spherical fluorescence bead translocation involves electrophoresis as well as other additional factors. Our theoretical calculation suggested that one additional factor is electro-osmotic trapping associated with the instantaneous Brownian motion before and after translocation. Furthermore, compressed DNA molecular conformation was seen as a result of the increase of peak photon counts and the decrease of electrophoretic mobility with voltage. Our experiments showed that the polymers at the vicinity of a nanopore can be trapped and compressed, which is necessary to understand how to control the polymer translocation into a nanopore.

Label-Free Single-Molecule Thermoscopy Using a Laser-Heated Nanopore.

When light is used to excite electronic transitions in a material, nonradiative energy during relaxation is often released in the form of heat. In this work, we show that photoexcitation of a silicon nitride nanopore using a focused visible laser results in efficient localized photothermal heating, which reduces the nearby electrolyte viscosity and increases the ionic conductance. In addition, a strong localized thermal gradient in the pore vicinity is produced, evidenced by finite-element simulations and experimental observation of both ion and DNA thermophoresis. After correcting for thermophoresis, the nanopore current can be used as a nanoscale thermometer, enabling rapid force thermoscopy. We utilize this to probe thermal melting transitions in synthetic and native biomolecules that are heated at the nanopore. Our results on single molecules are validated by correspondence to bulk measurements, which paves the way to various biophysical experiments that require rapid temperature and force control on individual molecules.

[Acquired aplastic anemia: recent advances in pathophysiology and treatment].

Acquired aplastic anemia (AA) is an autoimmune disease caused by T cells specific to hematopoietic stem cells (HSCs). The presence of HLA allele-lacking leukocytes due to uniparental disomy of the short arm of chromosome 6 (6pUPD) or allelic mutations strongly indicates the involvement of such cytotoxic T cells in the pathogenesis of AA. Attempts to improve treatment outcomes by intensification of immunosuppressive therapy (IST) have been unsuccessful. Eltrombopag (EPAG), a thrombopoietin receptor agonist, has recently emerged as a novel therapeutic agent for AA. EPAG directly acts on HSCs and stimulates proliferation, thereby achieving remission in approximately 40% AA patients refractory to IST. However, some cases develop chromosomal aberrations during treatment. Because somatic mutations are common in patients with AA, verifying whether EPAG induces clonal proliferation or evolution of mutant HSCs is critical.

[Treatment strategy for acquired aplastic anemia].

"The guidelines for the diagnosis and treatment of aplastic anemia (AA) in Japan" have recently been revised. Former stage 2 has been divided into stage 2a, which does not require red blood cell (RBC) transfusions, and stage 2b, which requires <2 units of RBC transfusions per month. In addition, the guidelines recommend treating stage 2b similar to stages 3 or higher severity. The standard immunosuppressive therapy for transfusion-dependent AA has been changed from ATG plus cyclosporine (CsA) to ATG+CsA+eltrombopag. For patients with stage 1 and stage 2b AA, initiating CsA as early as possible after the diagnosis is recommended. Notably, high-dose (200 mg/kg) cyclophosphamide (CY), which has been used as the standard conditioning regimen for allogeneic stem cell transplantation (SCT), is less frequently used than a reduced-dose CY regimen that contains fludarabine for avoiding cardiotoxicity. Among transplant regimens from alternative donors, HLA-haploidentical SCT from related donors using post-transplant CY is presently garnering recognition because of its low transplant-related mortality and the low incidence of chronic GVHD.

Outcome of Second Transplantation Using Umbilical Cord Blood for Graft Failure after Allogeneic Hematopoietic Stem Cell Transplantation for Aplastic Anemia.

Graft failure (GF) is the most critical life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT) for aplastic anemia, for which a second transplantation is the only effective treatment. Optimal procedures have not been established for the second transplantation in this setting, however. Here we retrospectively analyzed the outcomes of 22 patients with aplastic anemia, age ≥16 years, who underwent umbilical cord blood transplantation for GF after the first HSCT using the registry database of the Japan Society for Hematopoietic Cell Transplantation. The median age of patients was 36 years (range, 16 to 72 years), and the median time from the first to the second transplant was 77 days (range, 29 to 1061 days). The cumulative incidence of neutrophil engraftment at day 60 post-transplantation was 45.5% (95% confidence interval [CI], 23.6% to 65.0%). With a median follow-up of 50 months, the 4-year overall survival (OS) was 38.5% (95% CI, 18.4% to 58.5%). Mycofenolate mofetil-based graft-versus-host disease prophylaxis demonstrated greater neutrophil recovery than prophylaxis with calcineurin inhibitor alone or methotrexate-based prophylaxis (66.7% versus 37.5%; P = .04). The use of such conditioning regimens as fludarabine + melphalan or cyclophosphamide + low-dose total body irradiation was associated with better engraftment (58.3% versus 30%; P = .05) and better 4-year OS (55.6% versus 20%; P = .05) than other regimens. Although further investigation is needed, umbilical cord blood could be an effective and promising option for stem cell source for urgent second transplantation in patients with aplastic anemia who develop GF after the first HSCT.

Acute myeloid leukemia developing secondary immune thrombocytopenia after umbilical cord blood transplantation.

A 64-year-old man was diagnosed with acute myeloid leukemia M2 (FLT3-ITD-positive). After induction chemotherapy and four courses of consolidation therapy, he underwent umbilical cord blood transplantation (CBT) in his first remission. He developed acute graft-versus-host disease (skin stage 2) after successful engraftment. On post-transplantation day 147, he was admitted to the hospital suffering from pneumonia. During the treatment, drastic thrombocytopenia was observed on day 251. Both platelet-associated immunoglobulin G and platelet antibody producing B cells were detected, and he was diagnosed with immune thrombocytopenia (ITP). Treatment with prednisolone (1 mg/kg/day), eltrombopag (25 mg/day), and intravenous immunoglobulin (400 mg/kg) was commenced, but there was no improvement in his platelet count. After switching from eltrombopag to romiplostim (350 µg/week), and addition of cyclosporine, the platelet count rapidly elevated to 150,000/µl. ITP after allogenic stem cell transplantation is a rare complication, and it is often refractory to the 1st-line treatment such as steroids. Herein, we report successful treatment using a combination of romiplostim and an immunosuppressive agent in the case of treatment failure in ITP that developed after CBT.

A Comparison of Outcomes for Cord Blood Transplantation and Unrelated Bone Marrow Transplantation in Adult Aplastic Anemia.

Earlier reports suggested that umbilical cord blood transplantation (UCBT) for aplastic anemia (AA) was feasible in alternative transplantation. To identify differences in outcomes of UCBT and HLA-matched or mismatched unrelated bone marrow transplantation (UBMT) in adults with AA, we analyzed registry data of the Japan Society for Hematopoietic Cell Transplantation and compared results of UCBT (n = 69) to 8/8-matched (n = 101), 7/8-matched (n = 65), or 6/8-matched (n = 37) UBMT. The transplantation period was from 2002 to 2012, and patients 16 years or older with AA were eligible. Median ages were 49, 35, 28, and 30 years for UCBT, 8/8-matched, 7/8-matched, and 6/8-matched UBMT, respectively. In multivariate analysis, risk of mortality was lower for 8/8-matched UBMT compared with that of UCBT (hazard ratio [HR], .55; 95% confidence interval [CI], .32 to .94; P = .029), adjusted for age and graft-versus-host disease (GVHD) prophylaxis, which were other associated factors. Mortality risks of 7/8-matched UBMT (HR, .55; 95% CI, .29 to 1.02) or 6/8-matched UBMT (HR, .67; 95% CI, .32 to 1.39) were not significantly different from those of UCBT. Risks of grade 3 or 4 acute and chronic GVHD were not different among the 4 groups. The most prevalent cause of death was graft failure in UCBT and 6/8-matched UBMT and infection in 8/8-matched and 7/8-matched UBMT. Under 40 years old,survival of UCBT was similar to that of UBMT (76%, 79%, 83%, and 83% for UCBT and 8/8-matched, 7/8-matched, and 6/8-matched UBMT, respectively, at 3 years), adjusted for transplantation period, which was another associated factor; however, for ages over 40 years, that of UCBT tended to be lower (47%, 64%, 64%, and 75% for UCBT, 8/8-matched, 7/8-matched, and 6/8-matched UBMT, respectively, at 3 years). To conclude, these data suggest that UCBT could be an alternative treatment option for younger adults when matched sibling or adequate UBMT donors are not available.