Osteomacs promote maintenance of murine hematopoiesis through megakaryocyte-induced upregulation of Embigin and CD166

Maintenance of hematopoietic stem cell (HSC) function in the niche is an orchestrated event. Osteomacs (OM) are key cellular components of the niche. Previously, we documented that osteoblasts, OM, and megakaryocytes interact to promote hematopoiesis. Here, we further characterize OM and identify megakaryocyte-induced mediators that augment the role of OM in the niche. Single-cell mRNA-seq, mass spectrometry, and CyTOF examination of megakaryocyte-stimulated OM suggested that upregulation of CD166 and Embigin on OM augment their hematopoiesis maintenance function. CD166 knockout OM or shRNA-Embigin knockdown OM confirmed that the loss of these molecules significantly reduced the ability of OM to augment the osteoblast-mediated hematopoietic-enhancing activity. Recombinant CD166 and Embigin partially substituted for OM function, characterizing both proteins as critical mediators of OM hematopoietic function. Our data identify Embigin and CD166 as OM-regulated critical components of HSC function in the niche and potential participants in various in vitro manipulations of stem cells.

mG-FAST, a single pre-hospital stroke screen for evaluating large vessel and non-large vessel strokes

Background

Several 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.

Methods

This 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.

Results

33/150 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.

Conclusions

Utilizing 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.

Outcomes of Endovascular Stenting in Symptomatic Vertebral Artery Ostial Stenosis

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.

Case of Cocaine Induced Coronary and Carotid Artery Dissection

Cocaine use has been individually linked to both carotid and coronary artery dissections. However, their simultaneous occurrence has not been previously reported. A 30-year-old man who suffered an acute ischemic stroke and myocardial infarction secondary to acute carotid and coronary artery dissections, respectively, 16 hours after snorting cocaine. To our knowledge, this is the first reported case describing the simultaneous occurrence of carotid and coronary artery dissections resulting from cocaine use.

Cellular components of the hematopoietic niche and their regulation of hematopoietic stem cell function

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.