Biology subjects

Cober, N. D.

Publications and source records attributed to Cober, N. D..

4 recordsLinked to original sources

bioRxiv2023

Emergence of disease specific endothelial and stromal cell populations involved in arterial remodeling during development of pulmonary arterial hypertension

AbstractPulmonary arterial hypertension (PAH) is a severe and lethal pulmonary vascular disease characterized by arteriolar pruning and occlusive vascular remodeling leading to increased pulmonary vascular resistance and eventually right heart failure. While endothelial cell (EC) injury and apoptosis are known triggers for this disease, the mechanisms by which they lead to complex arterial remodeling remain obscure. We employed multiplexed single-cell RNA sequencing (scRNA-seq) at multiple timepoints during the onset and progression of disease in a model of severe PAH to identify mechanisms involved in the development of occlusive arterial lesions. There was significant loss of arterial volume as early as 1-week by microCT, preceding any evidence of occlusive arteriopathy, consistent with early arteriolar dropout. Maximal arterial pruning was seen by 5 to 8 weeks, with signs of progressive occlusive remodeling. Analysis of the scRNA-seq data resolved 44 lung cell populations, with widespread early transcriptomic changes at 1 week affecting endothelial, stromal and immune cell populations. Notably, this included emergence of a relatively dedifferentiated (dD) EC population that was enriched for Cd74 expression compared to general capillary (gCap) ECs which were primed to undergo endothelial-mesenchymal transition, as evidenced by RNA velocity analysis. However, at late timepoints (5 and 8 weeks), activated arterial ECs (aAECs) were the only cell population exhibiting persistent differential gene expression. This was characterized by a growth regulated state, including high expression of Tm4sf1, a gene implicated in cancer cell growth, which was also expressed by a smooth muscle (SM)-like pericyte cluster. Both these populations were localized to regions of arterial remodeling in the rat model and PAH patients, with aAECs contributing to intimal occlusive lesions and SM-like pericytes forming bands of medial muscularization. Together these findings implicate disease-specific vascular cells in PAH progression and suggest that TM4SF1 may be a novel therapeutic target for arterial remodeling.

molecular biology↗

bioRxiv2022

Single-cell microencapsulation improves lung retention of endothelial colony forming cells after intravascular delivery and unmasks therapeutic benefit in severe pulmonary arterial hypertension

BackgroundPulmonary arterial hypertension (PAH) is triggered by pulmonary vascular endothelial cell apoptosis and microvascular loss; therefore, therapies that can regenerate lost vasculature may offer therapeutic benefit. Endothelial colony forming cells (ECFCs) can directly repair damaged blood vessels and may have therapeutic potential for the treatment of PAH. However, poor retention of ECFCs in the lungs following intravenous delivery greatly limits their therapeutic application. Therefore, we studied whether cellular microencapsulation could enhance ECFCs viability and retention in the lung after systemic delivery and improve therapeutic efficacy of ECFCs in a rat monocrotaline (MCT) PAH model. MethodsECFCs were encapsulated by vortex-emulsion using various concentrations of agarose, and capsule size and initial cell viability were assessed. Encapsulated and free ECFCs were transduced with luciferase and administered to Sprague-Dawley rats three days after injection of MCT. ECFCs were tracked in vivo by bioluminescence imaging (BLI) to assess cell persistence and bio-distribution. At end-study, right ventricular systolic pressure (RVSP) and right ventricular hypertrophy were assessed for therapeutic efficacy. ResultsMicrogel encapsulation using 3.5% agarose improved cells survival and supported cell migration from capsules. At 15 minutes after delivery, BLI radiance were similar for free and microencapsulated ECFCs; however, only encapsulated cells could be detected by BLI at 4 and 24 hours. Transplantation of microencapsulated ECFCs led to significant improvement in RVSP three weeks after delivery compared to non-encapsulated ECFCs. ConclusionTogether, microencapsulation increased retention of ECFCs within the lungs. Furthermore, even a modest increase in ECFCs persistence over 24 hours can provide an important therapeutic benefit in the rat MCT model of PAH.

bioengineering↗

bioRxiv2022

Targeting extracellular vesicle delivery to the lungs by microgel encapsulation

Extracellular vesicles (EVs) secreted by stem and progenitor cells have significant potential as cell-free cellular therapeutics. Yet, small EVs (<200 nm) are rapidly cleared after systemic administration, mainly by the liver, presenting challenges targeting EVs to a specific organ or tissue. Microencapsulation using natural nano-porous hydrogels (microgels) has been shown to enhance engraftment and increase the survival of transplanted cells. We sought to encapsulate EVs within microgels to target their delivery to the lung by virtue of their size-based retention within the pulmonary microcirculation. Mesenchymal stromal cell (MSC) derived EVs were labelled with the lipophilic dye (DiR) and encapsulated within agarose-gelatin microgels. Endothelial cells and bone marrow derived macrophages were able to take up EVs encapsulated in microgels in vitro, but less efficiently than the uptake of free EVs. Following intrajugular administration, microgel encapsulated EVs were selectively retained within the lungs for 72 hours, while free EVs were rapidly cleared by the liver. Furthermore, microgel loaded EVs demonstrated greater uptake by lung cells, in particular CD45+ immune cells, as assessed by flow cytometry compared to free EVs. Microencapsulation of EVs may be a novel tool for enhancing targeted delivery of EVs for future therapeutic applications.

bioengineering↗

bioRxiv2021

Newly Emergent Apelin Expressing Endothelial Stem-like Cells Orchestrate Lung Microvascular Repair

QuestionWe sought to define the mechanism underlying lung microvascular regeneration in a severe acute lung injury (ALI) model induced by selective lung endothelial cell ablation. MethodsChanges in lung cell populations and gene expression profiles were determined in transgenic mice expressing human diphtheria toxin (DT) receptor targeted to ECs using single-cell RNA sequencing at baseline (day 0) and days 3, 5 and 7 after lung EC ablation. ResultsEight distinct endothelial clusters were resolved, including alveolar aerocytes (aCap) ECs expressing apelin at baseline, and general capillary (gCap) ECs expressing the apelin receptor. Intratracheal instillation of DT resulted in ablation of >70% of lung ECs, producing severe ALI with near complete resolution by 7 days. At 3 days post injury, a novel gCap population emerged characterized by de novo expression of apelin, together with the stem cell marker, protein C receptor. These stem-like cells transitioned to proliferative ECs, expressing apelin receptor together with the pro-proliferative transcription factor, FoxM1. This progenitor-like cell population was responsible for the rapid replenishment of all depleted EC populations by 7 days post injury, including aerocytes which play a critical role in re-establishment of the air-blood barrier. Treatment with an apelin receptor antagonist prevented recovery and resulted in excessive mortality, consistent with a central role for apelin signaling in EC regeneration and microvascular repair. ConclusionThe lung has a remarkable capacity for microvasculature EC regeneration which is orchestrated by signaling between newly emergent apelin-expressing gCap endothelial stem-like cells and highly proliferative, apelin receptor positive endothelial progenitors. Take-Home messageUsing sublethal lung endothelial cell (EC) ablation, we show for the first that EC regeneration and resolution of acute lung injury is orchestrated by novel apelin-expressing, gCap endothelial stem-like cells by a mechanism requiring apelin signaling. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY A schematic representation of EC populations contributing to microvascular repair. At baseline (Day 0), there are two main alveolar groups of capillary ECs: larger apelin positive aCap ECs, termed aerocytes, that play a key structural role in forming the air-blood barrier; and smaller apelin receptor (Aplnr) expressing gCap ECs, which are found in the thicker regions at the corners of the alveoli. After DT-induced EC ablation, there is a marked depletion of both EC populations and the appearance of novel transitional and transient populations. At Day 3, there is the appearance of stem-like gCap ECs that paradoxically express apelin, but not its receptor, and are characterized by various stem and progenitor cell markers but show no evidence of proliferation. By Day 5, these transition to ECs expressing Aplnr which have a strong proliferative phenotype, as evidenced by FoxM1 and Ki67 expression, and then rapidly replenish depleted EC pools, including aCap ECs, by Day 7. This transition is orchestrated by the interaction of apelin with its receptor as a critical mechanism in lung microvascular regeneration after EC injury. AT1 = alveolar type -1 epithelial cell; AT2 = alveolar type-2 epithelial cell; APLNR = apelin receptor; ANGPT2 = angiopoietin 2; EPCR = Endothelial protein C receptor.

cell biology↗