Purpose of review
Development and functions of hematopoietic stem cells (HSC) are regulated by multiple cellular components of the hematopoietic niche. Here we review the recent advances in studying the role of three such components -- osteoblasts, osteomacs, and megakaryocytes and how they interact with each other in the hematopoietic niche to regulate HSC.
Recent findings
Recent advances in transgenic mice models, scRNA-seq, transcriptome profile, proteomics, and live animal imaging have revealed the location of HSC within the bone and signaling molecules required for the maintenance of the niche. Interaction between megakaryocytes, osteoblasts and osteomacs enhances hematopoietic stem and progenitor cells (HSPC) function. Studies also revealed the niche as a dynamic entity that undergoes cellular and molecular changes in response to stress. Aging, which results in reduced HSC function, is associated with a decrease in endosteal niches and osteomacs as well as reduced HSC--megakaryocyte interactions.
Summary
Novel approaches to study the cellular components of the niche and their interactions to regulate HSC development and functions provided key insights about molecules involved in the maintenance of the hematopoietic system. Furthermore, these studies began to build a more comprehensive model of cellular interactions and dynamics in the hematopoietic niche.
BackgroundSeveral stroke scales have been implemented to enhance early recognition of large vessel occlusion (LVO) in the field. These scales necessitate a tiered approach requiring emergency medical services (EMS) to utilize two scales, one for identifying stroke and another for differentiating LVO from non-LVO. Ideally, a single stroke scale should be utilized by EMS for triage.MethodsThis is a prospective analysis of 150 consecutive patients presenting with stroke symptoms from the field. The stroke scale modified Gaze-Face-Arm-Speech-Time (mG-FAST) was used to simultaneously identify stroke and detect LVO in the pre-hospital setting. Imaging was used to confirm the presence of a LVO and determine the sensitivity and specificity of mG-FAST. The receiver operating curve (ROC) was plotted to calculate the area under the curve (AUC). Youden's index was used to determine the optimal cutoff score. Inter-rater reliability was obtained by comparing the EMS and stroke provider mG-FAST scores. EMS dispatch-to-thrombectomy-capable stroke center (mothership, MS) arrival time and groin puncture time were compared before and after the implementation of mG-FAST.Results33/150 patients had a confirmed LVO by imaging. 32/33 patients had an mG-FAST score ≥3. The AUC of mG-FAST was 0.899. An mG-FAST cut-off point of ≥3 yielded a sensitivity of 0.97 and specificity of 0.55 for LVO. The accuracy of this cut-off point was 64%. The EMS dispatch-to-MS time and groin puncture time decreased by 22 and 40 min after implementation of mG-FAST, respectively. With admission to the MS, the EMS dispatch-to-MS time decreased by 174.7 min compared to admission to a drip-and-ship (DS) hospital.ConclusionsUtilizing a single stroke scale in the field improves EMS dispatch-to-MS time, EMS dispatch-to-groin puncture time, and EMS door-to-intervention time. Implementation of mG-FAST as a pre-hospital screening tool is an effective method of triaging patients to the MS or DS hospitals.
Vertebral artery ostial stenosis is implicated in one-fifth of all posterior circulation cerebrovascular accidents. However, uniform treatment guidelines and data on the different treatment modalities are still lacking. Endovascular stenting is an emerging therapy for symptomatic vertebral artery ostial stenosis when medical management fails. This manuscript will examine the safety and efficacy of endovascular revascularization with drug-eluting stents in a series of ten consecutive patients that had failed medical management. We also report the rate of complications and in-stent restenosis, as well as the rate of recurrent cerebrovascular accidents.
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