CALR-mutated patients with low allele burden represent a specific subtype of essential thrombocythemia: A study on behalf of FIM and GBMHM

A low allele burden (i.e., <20%) of the CALR driver mutation is found in 10.8% of CALR-mutated MPNs, mostly in essential thrombocythemia, and correlates with a milder phenotype and a more indolent evolution compared to patients with an allele burden ≥20%.

Efficacy of ruxolitinib in the treatment of relapsed/refractory large granular lymphocytic leukaemia

Large granular lymphocytic (LGL) leukaemia is a rare chronic lymphoproliferative disorder characterized by an expansion of cytotoxic T or NK cells. Despite a usually indolent evolution, most patients will require a treatment over the course of the disease because of cytopenia or symptomatic associated autoimmune disorders. First-line treatment is based on immunosuppressive agents, namely cyclophosphamide, methotrexate and ciclosporin. However, relapses are frequent, and there is no consensus on the management of relapsed/refractory patients. The implication of the JAK/STAT pathway in the pathogenesis of this disease has prompted our group to propose treatment with ruxolitinib. A series of 21 patients who received this regimen is reported here. Ten patients (47.6%) were refractory to the three main immunosuppressive drugs at the time of ruxolitinib initiation. Ruxolitinib yielded an overall response rate of 86% (n = 18/21), including 3 complete responses and 15 partial responses. With a median follow-up of 9 months, the median response duration was 4 months. One-year event-free survival and 1-year overall survival were 57% and 83% respectively. Mild side effects were observed. Biological parameters, notably neutropenia and anaemia, improved significantly, and complete molecular responses were evidenced. This study supports ruxolitinib as a valid option for the treatment of relapsed/refractory LGL leukaemia.

Clinical and histological features of histiocytoid Sweet syndrome associated with VEXAS syndrome

BACKGROUND

"Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic" (VEXAS) syndrome is caused by acquired somatic mutations in the ubiquitin-activating enzyme 1 (UBA1) gene. Sweet-syndrome-like skin disorders (and especially histiocytoid Sweet syndrome (HSS)) may be associated with VEXAS syndrome.

OBJECTIVE

To characterize the clinical and histopathological features of HSS in patients with VEXAS syndrome.

METHODS

The skin biopsies with a histological diagnosis of HSS had been collected at Rennes University Medical Center (Rennes, France) between October 2011 and January 2022. Sanger sequencing and digital PCR were used to screen skin, blood, and bone marrow samples for UBA1 variants, and thus classify patients as having VEXAS syndrome or not. We evaluated the clinical, histological, and molecular (UBA1) characteristics of patients with or without VEXAS syndrome.

RESULTS

We compared 15 skin biopsies from seven patients found to have VEXAS syndrome and 19 skin biopsies from 15 patients without VEXAS syndrome. Persistent inflammatory syndrome, macrocytosis, anemia, and hematological malignancies were more prevalent in patients with VEXAS syndrome (86%, 86%, 100%, and 86%, respectively) than in patients without (36%, 40%, 53%, and 53%, respectively). These features sometimes appeared after the first skin manifestations, and a UBA1 mutation was found in the skin of five patients with VEXAS syndrome. Dermal infiltration by myeloperoxidase-positive, CD163-positive, reniform histiocytoid cells and a periadnexal distribution were more frequently observed in VEXAS syndrome biopsies (100% and 20% respectively, vs. 58% and 0% in non-VEXAS syndrome biopsies, respectively).

CONCLUSION

Our findings might help the pathologist to consider a diagnosis of VEXAS syndrome and to initiate early genetic testing.

Hepatosplenic T-cell lymphoma displays an original oyster-shell cytological pattern and a distinct genomic profile from that of gamma-delta T-cell large granular lymphocytic leukemia

Not available.

Genetic alterations and MRD refine risk assessment for KMT2A-rearranged B-cell precursor ALL in adults: a GRAALL study

KMT2A-rearranged (KMT2A-r) B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is widely recognized as a high-risk leukemia in both children and adults. However, there is a paucity of data on adults treated in recent protocols, and the optimal treatment strategy for these patients is still a matter of debate. In this study, we set out to refine the prognosis of adult KMT2A-r BCP-ALL treated with modern chemotherapy regimen and investigate the prognostic impact of comutations and minimal residual disease (MRD). Of 1091 adult patients with Philadelphia-negative BCP-ALL enrolled in 3 consecutive trials from the Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL), 141 (12.9%) had KMT2A-r, with 5-year cumulative incidence of relapse (CIR) and overall survival (OS) rates of 40.7% and 53.3%, respectively. Molecular profiling highlighted a low mutational burden in this subtype, reminiscent of infant BCP-ALL. However, the presence of TP53 and/or IKZF1 alterations defined a subset of patients with significantly poorer CIR (69.3% vs 36.2%; P = .001) and OS (28.1% vs 60.7%; P = .006) rates. Next, we analyzed the prognostic implication of MRD measured after induction and first consolidation, using both immunoglobulin (IG) or T-cell receptor (TR) gene rearrangements and KMT2A genomic fusion as markers. In approximately one-third of patients, IG/TR rearrangements were absent or displayed clonal evolution during the disease course, compromising MRD monitoring. In contrast, KMT2A-based MRD was highly reliable and strongly associated with outcome, with early good responders having an excellent outcome (3-year CIR, 7.1%; OS, 92.9%). Altogether, our study reveals striking heterogeneity in outcomes within adults with KMT2A-r BCP-ALL and provides new biomarkers to guide risk-based therapeutic stratification.

Five new F10 variants in hereditary factor x deficiency detected by high-throughput sequencing

INTRODUCTION

Factor X deficiency is a rare inherited bleeding disorder. To date, 181 variants are reported in the recently updated F10-gene variant database.

AIM

This study aimed to describe new F10 variants.

METHOD

The F10 gene was analysed in 16 consecutive families with FX deficiency by a targeted high-throughput sequencing approach, including F10, F9, F8 genes, and 78 genes dedicated to haematological malignancies.

RESULTS

We identified 19 variants (17 missense, one nonsense and one frameshift) and two copy number variations. Two patients presenting a combined FVII-FX deficiency showed a loss of one F10 gene copy (del13q34) associated with a missense variant on the remaining allele, leading to a FX:C significantly lower than the FVII:C level and explaining their unusual bleeding history. We reported five novel variants. Three missense variants (p.Glu22Val affecting the signal peptide cleavage site, p.Cys342Tyr removing the disulphide bond between the FX heavy and light chains, and p.Val385Met located in FX peptidase S1 domain) were detected at compound heterozygosis status in three patients with severe bleeding symptoms and FX:C level below 10 IU/dL. Two truncating variants p.Tyr279* and p.Thr434Aspfs*13 leading to an altered FX protein were found at heterozygous state in two patients with mild bleeding history.

CONCLUSION

This study showed the feasibility and the interest of high-throughput sequencing approach for rare bleeding disorders, enabling the report of F10 gene screening in a 3-weeks delay, suitable for clinical use. The description of five new variants may contribute to a better understanding of the phenotype-genotype correlation in FX deficiency.

Targeted High-throughput Sequencing for Hematological Malignancies: A GBMHM Survey of Practice and Cost Evaluation in France

The objective of this study was to assess the clinical impact and financial costs of next-generation sequencing (NGS) in 5 categories of pediatric and adult hematological cancers. NGS prescriptions were prospectively collected from 26 laboratories, with varied technical and reporting practice (all or only significant targets). Impact was defined by the identification of (1) an actionable mutation, (2) a mutation with prognostic and/or theranostic value, and/or (3) a mutation allowing nosological refinement, reported by local investigators. A microcosting study was undertaken in 4 laboratories, identifying the types and volumes of resources required for each procedural step. Individual index prescriptions for 3961 patients were available for impact analysis on the management of myeloid disorders (two thirds) and, mainly mature B, lymphoid disorders (one third). NGS results were considered to impact the management for 73.4% of prescriptions: useful for evaluation of prognostic risk in 34.9% and necessary for treatment adaptation (actionable) in 19.6%, but having no immediate individual therapeutic impact in 18.9%. The average overall cost per sample was 191 € for the restricted mature lymphoid amplicon panel. Capture panel costs varied from 369 € to 513 €. Unit costs varied from 0.5 € to 5.7 € per kb sequenced, from 3.6 € to 11.3 € per target gene/hot-spot sequenced and from 4.3 € to 73.8 € per target gene/hot-spot reported. Comparable costs for the Amplicon panels were 5-8 € per kb and 10.5-14.7 € per target gene/hot-spot sequenced and reported, demonstrating comparable costs with greater informativity/flexibility for capture strategies. Sustainable funding of precision medicine requires a transparent discussion of its impact on care pathways and its financial aspects.

Large granular lymphocyte leukemia: An indolent clonal proliferative disease associated with an array of various immunologic disorders

Large granular lymphocyte leukemia (LGLL) is a chronic lymphoproliferative disorder characterized by the proliferation of T or NK cytotoxic cells in the peripheral blood, the spleen and the bone marrow. Neutropenia leading to recurrent infections represents the main manifestation of LGLL. One specificity of LGLL is its frequent association with auto-immune disorders, among them first and foremost rheumatoid arthritis, and other hematologic diseases, including pure red cell aplasia and bone marrow failure. The large spectrum of manifestations and the classical indolent course contribute to the diagnosis difficulties and the frequency of underdiagnosed cases. Of importance, the dysimmune manifestations disappear with the treatment of LGLL as the blood cell counts normalize, giving a strong argument for a pathological link between the two entities. The therapeutic challenge results from the high rate of relapses following the first line of immunosuppressive drugs. New targeted agents, some of which are currently approved in autoimmune diseases, appear to be relevant therapeutic strategies to treat LGLL, by targeting key activated pathways involved in the pathogenesis of the disease, including JAK-STAT signaling.

Tγδ LGLL identifies a subset with more symptomatic disease: analysis of an international cohort of 137 patients

Tγδ large granular lymphocyte leukemia (LGLL) is a rare variant of T-cell LGLL (T-LGLL) that has been less investigated as compared with the more frequent Tαβ LGLL, particularly in terms of frequency of STAT3 and STAT5b mutations. In this study, we characterized the clinical and biological features of 137 patients affected by Tγδ LGLL; data were retrospectively collected from 1997 to 2020 at 8 referral centers. Neutropenia and anemia were the most relevant clinical features, being present in 54.2% and 49.6% of cases, respectively, including severe neutropenia and anemia in ∼20% of cases each. Among the various treatments, cyclosporine A was shown to provide the best response rates. DNA samples of 97 and 94 cases were available for STAT3 and STAT5b mutation analysis, with 38.1% and 4.2% of cases being mutated, respectively. Clinical and biological features of our series of Tγδ cases were also compared with a recently published Tαβ cohort including 129 cases. Though no differences in STAT3 and STAT5b mutational frequency were found, Tγδ cases more frequently presented with neutropenia (P = .0161), anemia (P < .0001), severe anemia (P = .0065), and thrombocytopenia (P = .0187). Moreover, Vδ2- cases displayed higher frequency of symptomatic disease. Overall, Tγδ cases displayed reduced survival with respect to Tαβ cases (P = .0017). Although there was no difference in STAT3 mutation frequency, our results showed that Tγδ LGLL represents a subset of T-LGLL characterized by more frequent symptoms and reduced survival as compared with Tαβ LGLL.

Adult Low-Hypodiploid Acute Lymphoblastic Leukemia Emerges from Preleukemic TP53-Mutant Clonal Hematopoiesis

Low hypodiploidy defines a rare subtype of B-cell acute lymphoblastic leukemia (B-ALL) with a dismal outcome. To investigate the genomic basis of low-hypodiploid ALL (LH-ALL) in adults, we analyzed copy-number aberrations, loss of heterozygosity, mutations, and cytogenetics data in a prospective cohort of Philadelphia (Ph)-negative B-ALL patients (n = 591, ages 18-84 years), allowing us to identify 80 LH-ALL cases (14%). Genomic analysis was critical for evidencing low hypodiploidy in many cases missed by cytogenetics. The proportion of LH-ALL within Ph-negative B-ALL dramatically increased with age, from 3% in the youngest patients (under 40 years old) to 32% in the oldest (over 55 years old). Somatic TP53 biallelic inactivation was the hallmark of adult LH-ALL, present in virtually all cases (98%). Strikingly, we detected TP53 mutations in posttreatment remission samples in 34% of patients. Single-cell proteogenomics of diagnosis and remission bone marrow samples evidenced a preleukemic, multilineage, TP53-mutant clone, reminiscent of age-related clonal hematopoiesis.

SIGNIFICANCE

We show that low-hypodiploid ALL is a frequent entity within B-ALL in older adults, relying on somatic TP53 biallelic alteration. Our study unveils a link between aging and low-hypodiploid ALL, with TP53-mutant clonal hematopoiesis representing a preleukemic reservoir that can give rise to aneuploidy and B-ALL. See related commentary by Saiki and Ogawa, p. 102. This article is highlighted in the In This Issue feature, p. 101.

Abstract 5791: Microfluidics-based library preparation strategies for targeted high-throughput sequencing and RNA sequencing in hematological malignancies in clinical samples

Introduction We developed a unique panel of 54 target genes dedicated to hematological malignancies (HematoPanel) and screened 1,108 clinical samples. We also performed transcriptomic analysis and evaluated its relevance for patients with acute lymphoblastic leukemia (ALL).

Methods DNA and RNA were extracted from cell pellets with the Maxwell® RSC (Promega®). Libraries for targeted high-throughput DNA sequencing (HTS) were generated in duplicate from 100 ng with the Advanta™ NGS Library Prep Assay kit using the LP 48.48 IFC (integrated fluidic circuit) on a Juno™ and sequenced on the NextSeq™ 550 (Illumina®) to a median depth of coverage of approximately 1,200X per sample. Transcriptomic libraries were generated from 50 ng RNA with the Advanta RNA-Seq XT NGS Library Prep Kit using the LP 48.Atlas™ IFC on Juno and sequenced on the NextSeq 550. A bioinformatics pipeline was developed for fusion transcript detection. Differential gene expression was analyzed with the DESeq2 package after STAR alignment.

Results In 2020 we sequenced 1,108 consecutive samples in routine practice with HematoPanel. The main indications were the suspicion of myeloproliferative neoplasms (32%), the evaluation of chronic lymphocytic leukemia (23%), and the diagnostic workup of cytopenias (15%). We detected 1,306 mutations in 654 patients (59%) (1 to 8 mutations per sample). Eight genes (TET2, SF3B1, TP53, DNMT3A, ASXL1, JAK2, SRSF2 and MYD88) were reported as mutated for more than 50 patients. We sequenced 22 samples including the MOLT-4 cell line, healthy donor samples, and 16 ALL samples for transcriptomic evaluation. From ALL samples, we detected 5 fusion transcripts previously identified by specific PCR (1 BCR-ABL, 2 ETV6-RUNX1, 1 KMT2A-AFF1, 1 TCF3-PBX1). Moreover, we detected 4 other fusion transcripts for 3 patients (EBF1-PDGFRB, FGFR1-MYO18A, P2RY8-CRLF2, and PAX5-NOL4L). Interestingly, these patients clustered with the BCR-ABL positive sample based on their expression profile. It confirms the diagnosis of Phi-like ALL and thus offers a therapeutic target for these patients.

Conclusion Microfluidics-based library prep using Juno offers a cost-effective strategy and straightforward workflows for both targeted HTS and RNA sequencing. We validated its use for hematological malignancy evaluation in routine practice.

Citation Format: Cédric Pastoret, Amyra Aliouat, Marie-Laure Boulland, Florent Denoual, Anne Desmares, Marie De Tayrac, Thierry Fest, Celeste Letellier. Microfluidics-based library preparation strategies for targeted high-throughput sequencing and RNA sequencing in hematological malignancies in clinical samples [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5791.

Toward a Better Classification System for NK-LGL Disorders

Large granular lymphocytic leukemia is a rare lymphoproliferative disorder characterized by a clonal expansion of T-lineage lymphocyte or natural killer (NK) cells in 85 and 15% of cases respectively. T and NK large granular leukemia share common pathophysiology, clinical and biological presentation. The disease is characterized by cytopenia and a frequent association with autoimmune manifestations. Despite an indolent course allowing a watch and wait attitude in the majority of patients at diagnosis, two third of the patient will eventually need a treatment during the course of the disease. Unlike T lymphocyte, NK cells do not express T cell receptor making the proof of clonality difficult. Indeed, the distinction between clonal and reactive NK-cell expansion observed in several situations such as autoimmune diseases and viral infections is challenging. Advances in our understanding of the pathogenesis with the recent identification of recurrent mutations provide new tools to prove the clonality. In this review, we will discuss the pathophysiology of NK large granular leukemia, the recent advances in the diagnosis and therapeutic strategies.

A reduced panel of eight genes (ATM, SF3B1, NOTCH1, BIRC3, XPO1, MYD88, TNFAIP3, and TP53) as an estimator of the tumor mutational burden in chronic lymphocytic leukemia

INTRODUCTION

Mutational complexity or tumor mutational burden (TMB) influences the course of chronic lymphocytic leukemia (CLL). However, this information is not routinely used because TMB is usually obtained from whole genome or exome, or from large gene panel high-throughput sequencing.

METHODS

Here, we used the C-Harrel concordance index to determine the minimum panel of genes for which mutations predict treatment-free survival (TFS) as well as large resequencing panels.

RESULTS

An eight gene estimator was defined encompassing ATM, SF3B1, NOTCH1, BIRC3, XPO1, MYD88, TNFAIP3, and TP53. TMB estimated from either a large panel of genes or the eight gene estimator was increased in treated patients or in those with a short TFS (<2 years), unmutated IGHV gene or with an unfavorable karyotype. Being an independent prognostic parameter, any mutation in the eight gene estimator predicted a shorter TFS better than Binet stage and IGHV mutational status among patients with an apparently non-progressive disease (TFS >6 months). Strikingly, the eight gene estimator was also highly informative for patients with Binet stage A CLL or with a good prognosis karyotype.

CONCLUSION

These results suggest that the eight gene estimator, that is easily achievable by high-throughput resequencing, brings robust and valuable information that predicts evolution of untreated patients at diagnosis better than any other parameter.

[A microcytic sideroblastic anemia successfully treated with B6 vitamin]

INTRODUCTION

Sideroblastic anemia is a rare cause of microcytic anemia, which is characterized by ring sideroblasts on bone marrow aspirate. This anemia can be congenital or acquired.

CASE REPORT

We report the case of an alcoholic 49-year-old man who presented with a severe microcytic sideroblastic anemia related to pyridoxine (B6 vitamin) deficiency. Acid folic deficiency was associated. The blood count normalized within one month after vitamin supplementation.

CONCLUSION

Pyridoxine deficiency must be sought in sideroblastic anemia in patients at risk.

IL-2 imprints human naive B cell fate towards plasma cell through ERK/ELK1-mediated BACH2 repression

Plasma cell differentiation is a tightly regulated process that requires appropriate T cell helps to reach the induction threshold. To further understand mechanisms by which T cell inputs regulate B cell fate decision, we investigate the minimal IL-2 stimulation for triggering human plasma cell differentiation in vitro. Here we show that the timed repression of BACH2 through IL-2-mediated ERK/ELK1 signalling pathway directs plasma cell lineage commitment. Enforced BACH2 repression in activated B cells unlocks the plasma cell transcriptional program and induces their differentiation into immunoglobulin M-secreting cells. RNA-seq and ChIP-seq results further identify BACH2 target genes involved in this process. An active regulatory region within the BACH2 super-enhancer, under ELK1 control and differentially regulated upon B-cell activation and cellular divisions, helps integrate IL-2 signal. Our study thus provides insights into the temporal regulation of BACH2 and its targets for controlling the differentiation of human naive B cells.

T cells help B cells to differentiate into antibody-producing plasma cells. Here the authors show that T cells produce interleukin-2 to activate ERK/ELK1 and suppress BACH2 expression by modulating the BACH2 super-enhancer, thereby altering BACH2 downstream transcription programs for plasma cell differentiation.

STAT3 mutation impacts biological and clinical features of T-LGL leukemia

STAT3 mutations have been described in 30-40% of T-large granular lymphocyte (T-LGL) leukemia patients, leading to STAT3 pathway activation. Considering the heterogeneity of the disease and the several immunophenotypes that LGL clone may express, the aim of this work was to evaluate whether STAT3 mutations might be associated with a distinctive LGL immunophenotype and/or might be indicative for specific clinical features. Our series of cases included a pilot cohort of 101 T-LGL leukemia patients (68 CD8+/CD4- and 33 CD4+/CD8±) from Padua Hematology Unit (Italy) and a validation cohort of additional 20 patients from Rennes Hematology Unit (France). Our results indicate that i) CD8+ T-LGL leukemia patients with CD16+/CD56- immunophenotype identify a subset of patients characterized by the presence of STAT3 mutations and neutropenia, ii) CD4+/CD8± T-LGL leukemia are devoid of STAT3 mutations but characterized by STAT5b mutations, and iii) a correlation exists between STAT3 activation and presence of Fas ligand, this molecule resulting highly expressed in CD8+/CD16+/CD56- patients. Experiments with stimulation and inhibition of STAT3 phosphorylation confirmed this relationship. In conclusion, our data show that T-LGL leukemia with specific molecular and phenotypic patterns is associated with discrete clinical features contributing to get insights into molecular bases accounting for the development of Fas ligand-mediated neutropenia.

T-cell-dependent fibrosis in the mdx dystrophic mouse

In Duchenne muscular dystrophy patients, the pathological hallmark of the disease, namely, the chronic accumulation of sclerotic scar tissue in the interstitial space of skeletal muscle is attributed to manifestation of secondary pathological processes. Such anomalous generation of matrix protein is thought to be driven by the continuous degeneration and regeneration of muscle both in Duchenne Muscular Dystrophy and in the mdx mouse homolog. We examined mdx and the control strain C57bl/10 mice over a range of ages with respect to the amounts of collagen present in muscles and other organs, finding that the mdx have significantly higher collagen content at later time points in their kidney and lung as well as their muscles. Surprisingly, when we bred the mdx mice on the nu/nu background, the time course of fibrogenesis was modified depending on the tissue and the collagen content was significantly different in age-matched mice. Transplantation of normal thymic tissue into the mdx-nu/nu mice replenished their T-cells and concomitantly altered the collagen content in their tissues to levels comparable with those in immunocompetent mdx mice. This suggests that T-cells play a role in the onset of the fibrotic events that undermines the ability of dystrophic muscle to regenerate.

Computerised dystrophic muscle simulator: prospecting potential therapeutic strategies for muscle dystrophies using a virtual experimental model

Inherited muscle diseases are often characterised by widespread muscle damage in the body, limiting the clinical relevance of cell or gene therapy based upon direct injections into muscles. Recent studies have shown, however, that cells originating from the bone marrow are able to target necrosis-regeneration sites as they occur and, in addition, may also participate in the muscle regeneration after undergoing myogenic differentiation. Here, we present a computerised dystrophic muscle simulator that allows the prospecting of different scenarios of both disease evolution and appropriate employment of blood-borne cells as therapeutic shuttles. It provides the option of examining their use either to transfer a healthy gene into the tissue or to impart substances designed to boost its regeneration. One of the major advantages of this tool is that it offers the opportunity of visualising and composing therapeutic strategies in virtual paradigms in which severe clinical situations, not necessarily available in animal models, can be created. The dystrophic muscle simulator is freely accessible via the Genethon web site (www.genethon.fr), and in the online version via http:@www.wiley.co.uk/genmed.

Morphological and functional study of extensor digitorum longus muscle regeneration after iterative crush lesions in mdx mouse

The regenerative capacity of mdx Extensor Digitorum Longus (EDL) muscle after iterative muscle crush injuries was examined and compared with that of age-matched control C57BL/10 mice. Muscle crush injuries were performed at 8 weeks and repeated at 12 and 16 weeks. Contralateral non-crushed EDLs from mdx and C57BL/10 mice were used as internal controls for histopathology, histoenzymology, morphometry and for the study of the contractile properties. Morphological examinations were performed at 12, 16 and 20 weeks, respectively one month after a single, a second or a third crush. Contractile properties were studied at 12 to 20 weeks. By 20 weeks, no difference in the number of fibres with internal nuclei could be observed between crushed EDL from both strains, and non-crushed mdx EDL; the area and the diameter of crushed EDL from mdx mice were, respectively, 1.5- and 1.2-fold higher than the ones from crushed EDL from C57BL/10 strain. By 20 weeks, diameter distribution of crushed EDL muscles from C57BL/10 mice were shifted towards smaller fibre diameter, whereas in mdx mice, diameter distribution of crushed EDL muscles paralleled that of non-crushed EDL muscles. By 20 weeks, crushed mdx and C57BL/10 EDL muscles produced 77 and 47% of normalized tetanus tension respectively of non-crushed mdx and C57BL/10 EDL muscles. Following crush injury, both 12- and 20-week mdx and C57BL/10 EDL exhibited a slowed time to peak (TTP) and half-relaxation time (H1/2R) of twitch. There was no difference in posttetanic potentiation between the different groups. Crushed EDL of both strains showed an increased resistance to fatigue, compared to the non-crushed controls. The present study provides morphological and functional evidence for the greater recovery of mdx muscle compared to C57BL/10 muscle following iterative crush injury; however, the recovery does not completely prevent the appearance of necrosis/regeneration features.

Age-related differences in regeneration of dystrophic (mdx) and normal muscle in the mouse

The mdx mouse, a genetic homologue of human Duchenne muscular dystrophy (DMD), has been attributed with a greater regenerative capacity of its skeletal muscles. Here, we have tested the hypothesis that muscles of mdx mice regenerate better than those of nondystrophic animals. We studied muscle regeneration resulting from a denervation-devascularization injury (DD) of extensor digitorum longus muscle (EDL) at 3 weeks and 2 months in mdx and wild-type (C57BL/10) mice. Histological and morphometrical studies of muscle regeneration were made from 3 to 180 days later. When DD was performed in 3-week-old C57BL/10 mice, the percentages of nonperipheral nuclei in regenerated fibers decreased progressively over 3 months. This decrease did not occur in animals where DDs were performed at 2 months, suggesting that two different populations of muscle precursor cells are mobilized in muscle regeneration in mice at these two ages. Moreover, mdx EDL muscle regenerated similarly to the controls for up to 60 postoperative days, as shown by distribution of mean diameters and percentage of nonperipheral nuclei of muscle fibers. After 60 postoperative days, necrosis/regeneration characteristics of mdx muscles recurred, suggesting that mdx-regenerated muscle fibers remain susceptible to degeneration.

Characterization of antibodies directed against platelet cryptantigens detected during the immunological study of 356 consecutive patients with presumed autoimmune thrombocytopenia (AITP)

Cryptic antigens are detected by antibodies present in a wide spectrum of patients with or without thrombocytopenia, and even in healthy individuals. They are produced for unknown reasons and do not react with antigens of native platelets, but only with altered platelets. Cryptantigen antibodies may not only result in spuriously low platelet counts, but also in 'falsely' positive tests for platelet antibodies. We report our experience in the characterization of the different types of antibodies directed against cryptantigens of platelets: EDTA-dependent antibodies, PFA-dependent antibodies, EDTA-PFA-dependent antibodies and cold agglutinins. These antibodies were detected in the course of the serological study of 37 patients from a group of 356 (10%) whose blood was sent to our laboratory for platelet antibody testing. Pseudothrombocytopenia was diagnosed in 24 cases. Twenty-one of these showed EDTA-dependent or EDTA-PFA-dependent platelet agglutination and three were due to the presence of cold agglutinins. In 13 patients the thrombocytopenia was genuine. Eleven of these presented EDTA-dependent or EDTA-PFA-dependent antibodies in their serum and in the two remaining cases PFA-dependent antibodies were found. Cryptantigen antibodies were also detected in 9 out of 228 (4%) blood donors who were used as healthy controls in the platelet immunofluorescence test. In the light of the results obtained we put forward some guidelines to detect the presence of these antibodies and establish an accurate serological and clinical diagnosis of the autoimmune thrombocytopenias.

Phenotype of dystrophinopathy in old mdx mice

BACKGROUND

Mdx mutant mice, like patients with Duchenne Muscular Dystrophy (DMD), lack dystrophin, a subsarcolemmal protein, that results in myofiber necrosis. However young mdx mice, in contrast to DMD children, exhibit a successful muscle regeneration and not an extensive fibrosis.

METHODS

Old mdx mice were monitored clinically up to their spontaneous death, and most of their organs were studied histologically to look for differences with those of the wild C57BL/10 mice strain.

RESULTS

In old mdx mice (at least 20 months of age), we report clinical and pathological features of muscular dystrophy, i.e., progressive motor weakness and loss of myofibers replaced by extensive connective tissue, similar to the phenotype of dystrophinopathy observed in DMD patients. Various degrees of dystrophic involvement were observed in cardiac, respiratory, postural, and hindlimb skeletal mdx muscles and also in smooth muscles of the digestive and urinary tracts. No gross histological abnormalities were found in other tissue than muscular tissue.

CONCLUSIONS

Late in life, mdx mice develop a muscular dystrophy close to DMD dystrophinopathy. We suggest that the study of the effects of ageing in mdx mice would give clues to better understand the pathophysiology of DMD.

mdx mice show progressive weakness and muscle deterioration with age

The time-course of degeneration/regeneration was investigated in leg muscles throughout the life of the mdx mutant mouse, which is a biochemical homologue of Duchenne muscular dystrophy (DMD). In young and adult mice (up to 52 weeks old), muscle fibre necrosis was compensated by a vigorous regeneration, but in old mdx mice (65-104 weeks) this regeneration slightly declined, while the necrotic process persisted. Body and muscles weights declined strikingly after 52 weeks. Life span of mdx mutants was reduced in comparison with the control C57BL/10 animals. Immunostaining of old mdx muscles showed clusters of dystrophin-positive fibres. Muscle fibres in old mdx mice showed great variation in size, many being atrophied or split. Endomysial fibrosis became increasingly conspicuous, and there was some accumulation of adipose tissue. These progressive degenerative changes of old mdx mice resemble those found in DMD and imply that basic pathological similarities between the murine and human diseases previously observed in diaphragm of mdx mice may be extended to other skeletal muscles.

Expression of NCAM and its polysialylated isoforms during mdx mouse muscle regeneration and in vitro myogenesis

In order to understand the mechanism of the muscular regenerative process which occurs in mdx mice, the expression of neural cell adhesion molecule (NCAM) isoforms and their polysialylated (PSA) derivatives were studied during the postnatal development of normal and mdx mice in relation to the stage of the regeneration of muscle fibres, in the quadriceps. NCAM expression was also examined during in vitro differentiation of satellite cells isolated from both mdx and normal muscles. The immunohistochemical and biochemical analyses were done using antibodies for the different isoforms. The data presented here suggest that before the onset of necrosis and regeneration, the expression of NCAM isoforms in the quadriceps of mdx mice was similar to normal mice. Later, NCAM and PSA-NCAM expression in mdx mice increased and was related to the muscular regenerative process, and the overall level of NCAM expression can be considered as a good index of muscle regeneration. Young regenerative fibres expressed NCAM and PSA-NCAM, while mature regenerative fibres, in which myonuclei remained centrally located, did not express either NCAM or the PSA isoforms. Therefore, in terms of NCAM expression, the fibres in mdx muscle with centrally located nuclei appeared similar to mature fibres found in normal adult muscle. A major form of 145 kDa and a minor form of 115 kDa were detected in mdx regenerative muscle. The 145 kDa NCAM was sialylated, as demonstrated by its sensibility to exoneuraminidase which generates a desialoform of 125 kDa, but not polysialylated since it was not recognized by the anti-MenB antibody, specific for PSA-NCAM. In contrast, the molecular forms of NCAM migrating as a broad band from 160 kDa to 220 kDa were identified as PSA-NCAM. The comparison of in vitro differentiation of normal and mdx satellite cells showed that the expression of NCAM isoforms by mdx cells was similar to that expressed by normal cells. Both our in vivo and in vitro data concerning NCAM expression show that regeneration in mdx mice does not differ from that observed in other necrotic diseases. In other words, NCAM is unlikely to be a dystrophin-associated molecule since lack of dystrophin does not affect its expression.

Fibres of intermediate type 1C and 2C are found continuously in mdx soleus muscle up to 52 weeks

The mdx mutant is a murine homologous model of Duchenne muscular dystrophy (DMD). Fibre types determined by the myosin-ATPase technique in soleus muscles were compared in C57BL/10 control and mdx mice from 3 to 52 weeks of age. The control strain continuously presented 70% of type 2 fibres whereas the mdx strain showed an increase to 80% at 6 weeks and a subsequent decline. In mdx muscles, necrosis which begins at 3 weeks of age did not affect specifically one type of fibre. Type grouping was never observed when muscle regeneration occurred. Fibres of intermediate type (1C and 2C) were found continuously up to 52 weeks of age in the mdx mutant. The foci of small immature regenerating fibres were of type 2C but never 1C. A few mature fibres were either of type 2C or 1C. We suggest that the presence of intermediate type fibres could result from the co-expression of type 1 and 2 myosin heavy chains, indicating a transition from type 2 to type 1 in regenerating fibres.

Transplantation of adult-derived myoblasts in mice following gene transfer

We have explored the use of myoblasts obtained from adult animals as a target for somatic gene therapy. Myoblasts from an adult beta-glucuronidase deficient (MPS VII) mouse were isolated and infected with a retroviral vector carrying the human beta-glucuronidase cDNA. Beta-glucuronidase was used as a reporter gene to follow the fate of genetically-modified myoblasts after transplantation into the tibialis anterior of MPS VII recipients. When experimental necrosis had been induced in the recipient muscle prior to cell injection, histological analysis demonstrated efficient engraftment of adult derived myoblasts following gene transfer. The reconstituted myofibres expressed the transgene for at least 10 weeks following transplantation.

Further aspects of muscular dystrophy in mdx mice

The histopathological aspects of leg muscles in young, adult and old mdx mice were compared. Before 1 yr of age, the mutant showed a vigorous regeneration, following the fibre necrosis, which led to hypertrophic muscles. Hypertrophy resulted from a mixture of hypertrophic and small fibres but not from fibrosis. From the age of 15 months, the muscles progressively atrophied and the fibres were atrophic or split. An important degree of fibrosis occurred particularly in soleus and plantaris muscles. These aspects in old mdx mice are similar to those described in other dystrophinopathies in animals and humans.

[Frequency of platelet alloantigens in the Spanish population]

PURPOSE

The aim of this study is to investigate the distribution and incidence of platelet alloantigens in Spain and to compare this frequency with that found in other populations.

MATERIAL AND METHODS

Five hundred blood donors were phenotyped for the HPA-1a (Zwa), HPA-3a (Bak(a)), HPA-4a (Yukb/Pen(a)) y HPA-4b (Yuk(a)). One hundred of these donors were also phenotyped for the HPA-5a (Br(a)) antigen. Furthermore, we also phenotyped a group of 50 black individuals from a community of west African immigrants who live in the province of Barcelona. The typing of all the antigens except those of the HPA-5 system was carried out using the technique of Indirect Immunofluorescence. To type the antigens of the HPA-5 system the MAIPA technique was employed.

RESULTS AND CONCLUSIONS

The incidence of the different platelet specific antigens in the Spanish population is, in general, the same as that detected in the other European countries and in the white population of the USA. In Europe and North America, the HPA-1a antigen is the most important of all owing to its involvement in alloimmune clinical disorders. In Asia, this role seems to be played by the HPA-4b antigen. Moreover, polymorphism for the HPA-1a allele does not seem to exist. The incidence of the HPA-5b (Br(a)) antigen in Spain, which is higher than that for France and Germany, suggests a high involvement of this antigen in our country in different alloimmune processes. The preliminary data obtained in a group of black west Africans suggest the absence on polymorphism for the HPA-1a allele and that the incidence of the remaining antigens is comparable to that of the Spanish population.

Time course study of the isometric contractile properties of mdx mouse striated muscles

The isometric twitch and tetanic contractions of three hindlimb muscles (soleus, plantaris, extensor digitorum longus) were recorded in situ in groups of mdx and C57BL/10 control mice at young, adult and old ages (3, 4, 6, 8, 13, 26, 39 and 52 weeks). Based on a two-way analysis of variance (age/phenotype) the mdx phenotype did not modify the absolute tension but was associated with a significant decrease in the tetanic tension normalized to muscle weight in all the muscles which became heavier. These results suggest that the contractile material in mdx is not so powerful as in controls. Moreover, significantly faster time to peak and half-relaxation time were observed in mdx soleus and plantaris. Comparison between these contraction characteristics and those of other experimental models suggests that the high percentage of regenerated fibres in mdx muscles could play a role in modifying contractile properties.

The Y chromosome effect on intermale aggression in mice depends on the maternal environment

Two parental strains of laboratory mice, NZB and CBA/H, were chosen for their differences in attack behavior. NZB have higher scores than CBA/H. An effect of the Y chromosome on attack behavior was determined for two maternal environments. Each male was tested once in a dyadic encounter with an A/J male as a standard opponent. The two reciprocal F1s and the four reciprocal backcrosses were used. In each group, the proportion of attacking males was used as the dependent variable. In the first experiment, the ovarian graft method was used to test for an effect of variation of the overall maternal environment: parental vs. F1. The results demonstrated an interaction between the Y chromosome and the maternal environment. By use of the adoption method, it was shown in the second experiment that this maternal effect was probably postnatal (and not prenatal).

[Non-hemolytic transfusion reactions of the febrile type]

The results of a hundred cases of febrile non haemolytic transfusion reactions are presented. We used the techniques that would best identify the different causes of these reactions. Most of these antibodies were anti HLA. Platelet and granulocyte-specific antibodies were seldom detected. The nature of the antibodies was specified by their different reactivity with the cells of various donors, by applying a panel of cells from typed donors and by absorption experiments. The study of the donor sera enabled us to elucidate the causes of some reactions. Nevertheless, in a significant percentage of cases it was not possible to determine the cause of the reaction, especially in the case of reactions secondary to platelet transfusions. Finally, we analyzed the reasons that could account for these phenomena.