A case of lymphoma mimicking infected internal iliac artery aneurysm

Abstract Background Malignant lymphoma rarely mimics an infected arterial aneurysm and a ruptured arterial aneurysm because of similar imaging findings, leading to misdiagnosis. The hematomas of ruptured aneurysms are radiologically difficult to distinguish from those of malignant lymphoma in emergency settings. Hence, a definitive diagnosis is crucial to avoid unnecessary surgery. Case presentation A man in his 80s with hematuria and shock vital had right internal iliac artery aneurysm (IIAA) and perianeurysmal fluid retention, which appeared to be a ruptured or an infected aneurysm. Treatment was initiated for infected IIAA instead of for ruptured IIAA. Systemic inflammatory response syndrome developed, and the infectious sources were assessed. Pacemaker lead and urinary tract infections were identified and treated; however, blood pressure was unstable. The aneurysm was treated with endovascular aortic aneurysm repair following antibiotic therapy; however, fluid retention increased, and inflammatory status and hematuria deteriorated. Open surgical conversion was performed to manage the infected lesions. Although an iliopsoas abscess was detected during surgery and nephrectomy and ureterectomy were performed to control the hematuria, analysis of the removed tissues led to the pathological diagnosis of diffuse large B-cell lymphoma (DLBCL). Conclusions We encountered a case of DLBCL with imaging findings mimicking an infected internal iliac artery aneurysm, and definitive diagnosis was made more than 2 months after the initial examination. Definitively diagnosing malignant lymphoma around an iliac artery aneurysm based merely on symptoms and imaging findings is extremely difficult. Thus, histological examination should be actively performed in atypical infected aneurysms

NG2-positive pericytes regulate homeostatic maintenance of slow-type skeletal muscle with rapid myonuclear turnover

Abstract Background Skeletal muscle comprises almost 40% of the human body and is essential for movement, structural support and metabolic homeostasis. Size of multinuclear skeletal muscle is stably maintained under steady conditions with the sporadic fusion of newly produced myocytes to compensate for the muscular turnover caused by daily wear and tear. It is becoming clear that microvascular pericytes (PCs) exhibit myogenic activity. However, whether PCs act as myogenic stem cells for the homeostatic maintenance of skeletal muscles during adulthood remains uncertain. Methods We utilized PC-fused myofibers using PC-specific lineage tracing mouse (NG2-CreERT/Rosa-tdTomato) to observe whether muscle resident PCs have myogenic potential during daily life. Genetic PC deletion mouse model (NG2-CreERT/DTA) was used to test whether PC differentiates to myofibers for maintenance of muscle structure and function under homeostatic condition. Results Under steady breeding conditions, tdTomato-expressing PCs were infused into myofibers, and subsequently, PC-derived nuclei were incorporated into myofibers. Especially in type-I slow-type myofibers such as the soleus, tdTomato+ myofibers were already observed 3 days after PC labeling; their ratio reached a peak (approximately 80%) within 1 month and was maintained for more than 1 year. Consistently, the NG2+ PC-specific deletion induced muscular atrophy in a slow-type myofiber-specific manner under steady breeding conditions. The number of myonucleus per volume of each myofiber was constant during observation period. Conclusions These findings demonstrate that the turnover of myonuclei in slow-type myofibers is relatively fast, with PCs acting as myogenic stem cells—the suppliers of new myonuclei under steady conditions—and play a vital role in the homeostatic maintenance of slow-type muscles

Additional file 1 of NG2-positive pericytes regulate homeostatic maintenance of slow-type skeletal muscle with rapid myonuclear turnover

Additional file 1: Fig. S1. Localization of NG2+ cells in adult skeletal muscle tissues. Circulating vessels in NG2-DsRed mice were visualized by intravenous injection of FITC-conjugated lectin. The lower limb skeletal muscles (gastrocnemius and soleus) were fixed and transparentized with RapiClear reagent. Microvessels, lectin-labeled endothelium tubes (lectin; green), and NG2+ cells (DsRed; red) within transparent muscles were visualized in a 3D view using confocal fluorescent microscopy. The nuclei were counterstained with DAPI. Scale bar = 50 µm. Fig. S2. NG2+ cell lineage tracing within the skeletal muscle. The tdTomato expression driven by the universal Rosa26 promoter was specifically induced in NG2+ cells using NG2-CreERT/Rosa-tdTomato mice. After five days of constitutive treatment with Tam, NG2+ cells were expressed. B. On day 1 of the observation period, tdTomato+ cells were observed only at perivascular sites, such as PCs. On day 21, tdTomato-expressing myofibers were observed in most muscle tissues. The ratio of tdTomato+ myofibers to total myofibers varied by muscle site, i.e., over 80% of tdTomato+ myofibers in the soleus and diaphragm and 20–30% in the gastrocnemius and rectus abdominal muscles. Scale bar = 200 µm. Fig. S3. Schematic diagram for the in vitro muscular differentiation assay. Myofibers were isolated from the soleus of NG2-CreERT/Rosa-tdTomato mice by using a collagenase-containing medium. Isolated myofibers were incubated in DMEM-containing 10% FBS and Tam (2 µM) for three days to label NG2+ PCs. The medium was then changed to a differentiation medium containing 2% horse serum. After six days of induction, the myogenesis of NG2+ PCs was observed. Fig. S4. In vitro myogenic potency of NG2+ PCs from soleus muscles. A. Myofibers isolated from the soleus of NG2-CreERT/Rosa-tdTomato mice, which were incubated in DMEM-containing hydroxy tamoxifen (Tam) for three days to label NG2+ PCs. After six days of differentiation induction, myogenesis was determined by immunostaining with myosin heavy chain (MyHC) and myosin heavy chain (MYH) isoform 2 and 7. Isolated soleus myofibers were used for control for immunostaining. Scale bars = 100 µm. Fig. S5. Tam treatment induces deletion of NG2+ cells. A. In vitro effects of 4-hydroxytamoxifen (4-HT) on NG2+ cells isolated from subcutaneous adipose tissues of NG2-CreERT/Rosa26-DTA mice. Cells at confluent were incubated in medium containing hydroxy-Tam for 5 days, and the number of cells were counted. B. Gene expression of NG2 in NG2+ cells with Tam was esteemed by qPCR. Fig. S6. Microarray enrichment analysis in response to PC deletion. After induction of NG2+ PC deletion for one month, microarray analysis of the soleus of PC-deletion and control mice was performed. The top 20 upregulated and downregulated pathway-related gene sets are listed