Mesenchymal stem cells and endothelial progenitor cells accelerate intra-aneurysmal tissue organization after treatment with SDF-1α-coated coils

Potential role of endothelial progenitor cells in the pathogenesis and treatment of cerebral aneurysm

Cerebral aneurysm (CA) is a significant health concern that results from pathological dilations of blood vessels in the brain and can lead to severe and potentially life-threatening conditions. While the pathogenesis of CA is complex, emerging studies suggest that endothelial progenitor cells (EPCs) play a crucial role. In this paper, we conducted a comprehensive literature review to investigate the potential role of EPCs in the pathogenesis and treatment of CA. Current research indicates that a decreased count and dysfunction of EPCs disrupt the balance between endothelial dysfunction and repair, thus increasing the risk of CA formation. Reversing these EPCs abnormalities may reduce the progression of vascular degeneration after aneurysm induction, indicating EPCs as a promising target for developing new therapeutic strategies to facilitate CA repair. This has motivated researchers to develop novel treatment options, including drug applications, endovascular-combined and tissue engineering therapies. Although preclinical studies have shown promising results, there is still a considerable way to go before clinical translation and eventual benefits for patients. Nonetheless, these findings offer hope for improving the treatment and management of this condition.

Endothelial Progenitor Cells: A Review of Molecular Mechanisms in the Pathogenesis and Endovascular Treatment of Intracranial Aneurysms

This comprehensive review explores the multifaceted role of endothelial progenitor cells (EPCs) in vascular diseases, focusing on their involvement in the pathogenesis and their contributions to enhancing the efficacy of endovascular treatments for intracranial aneurysms (IAs). Initially discovered as CD34+ bone marrow-derived cells implicated in angiogenesis, EPCs have been linked to vascular repair, vasculogenesis, and angiogenic microenvironments. The origin and differentiation of EPCs have been subject to debate, challenging the conventional notion of bone marrow origin. Quantification methods, including CD34+ , CD133+ , and various assays, reveal the influence of factors, like age, gender, and comorbidities on EPC levels. Cellular mechanisms highlight the interplay between bone marrow and angiogenic microenvironments, involving growth factors, matrix metalloproteinases, and signaling pathways, such as phosphatidylinositol-3-kinase (PI3K) and mitogen-activated protein kinase (MAPK). In the context of the pathogenesis of IAs, EPCs play a role in maintaining vascular integrity by replacing injured and dysfunctional endothelial cells. Recent research has also suggested the therapeutic potential of EPCs after coil embolization and flow diversion, and this has led the development of device surface modifications aimed to enhance endothelialization. The comprehensive insights underscore the importance of further research on EPCs as both therapeutic targets and biomarkers in IAs.

Comparison of Gelatin/Polylysine- and Silk Fibroin/SDF-1α-Coated Mesenchymal Stem Cell-Seeded Intracranial Stents

Endothelialization of the aneurysmal neck is essential for aneurysm healing after endovascular treatment. Mesenchymal stem cell (MSC)-seeded stents can promote aneurysm repair. The biological effects of coated and uncoated nitinol intracranial stents seeded with MSCs on vascular cells and macrophage proliferation and inflammation are investigated. Two stent coatings that exert pro-aggregation effects on MSCs via different mechanisms are examined: gelatin/polylysine (G/PLL), which enhances cell adhesion, and silk fibroin/SDF-1α (SF/SDF-1α), which enhances chemotaxis. The aim is to explore the feasibility of MSC-seeded coated stents in the treatment of intracranial aneurysms. The G/PLL coating provides the highest cytocompatibility and blood compatibility substrate for MSCs and vascular cells and promotes cell adhesion and proliferation. Moreover, it enhances MSC secretion and regulation of vascular cell and macrophage proliferation and chemotaxis. Although the SF/SDF-1α coating promotes MSC secretion and vascular cell chemotaxis, it induces a greater degree of macrophage proliferation, chemotaxis, and secretion of pro-inflammatory factors. MSC-seeded stents coated with G/PLL may benefit stent surface endothelialization and reduce the inflammatory response after endovascular treatment of intracranial aneurysm. These effects may improve aneurysm healing and increase the cure rate.

Engineered Cytokines for Cancer and Autoimmune Disease Immunotherapy

Cytokine signaling is critical to a range of biological processes including cell development, tissue repair, aging, and immunity. In addition to acting as key signal mediators of the immune system, cytokines can also serve as potent immunotherapies with more than 20 recombinant products currently Food and Drug Administration (FDA)-approved to treat conditions including hepatitis, multiple sclerosis, arthritis, and various cancers. Yet despite their biological importance and clinical utility, cytokine immunotherapies suffer from intrinsic challenges that limit their therapeutic potential including poor circulation, systemic toxicity, and low tissue- or cell-specificity. In the past decade in particular, methods have been devised to engineer cytokines in order to overcome such challenges and here, the myriad strategies are reviewed that may be employed in order to improve the therapeutic potential of cytokine and chemokine immunotherapies with applications in cancer and autoimmune disease therapy, as well as tissue engineering and regenerative medicine. For clarity, these strategies are collected and presented as they vary across size scales, ranging from single amino acid substitutions, to larger protein-polymer conjugates, nano/micrometer-scale particles, and macroscale implants. Together, this work aims to provide readers with a timely view of the field of cytokine engineering with an emphasis on early-stage therapeutic approaches.

Bioactive refinement for endosaccular treatment of intracranial aneurysms

Endovascular treatment is the first-line therapy for most intracranial aneurysms; however, recanalisation remains a major limitation. Developments in bioengineering and material science have led to a novel generation of coil technologies for aneurysm embolisation that address clinical challenges of aneurysm recurrence. This review presents an overview of modified surface coil technologies and summarises the state of the art regarding their efficacy and limitations based on experimental and clinical results. We also present potential perspectives to develop biologically optimised devices.

MFGE8 mitigates brain injury in a rat model of SAH by maintaining vascular endothelial integrity via TIGβ5/PI3K/CXCL12 signaling

Leaked blood components, injured endothelial cells, local inflammatory response and vasospasm may converge to promote microthrombosis following subarachnoid hemorrhage (SAH). Previously, we showed that the milk fat globule-epidermal growth factor 8 (MFGE8) can mitigate SAH-induced microthrombosis. This present study was aimed to explore the molecular pathway participated in MFGE8-dependent protection on vascular endothelium. Immunofluorescence, immunoblot and behavioral tests were used to determine the molecular partner and signaling pathway mediating the effect of MFGE8 in vascular endothelium in rats with experimental SAH and controls, together with the applications of RNA silencing and pharmacological intervention methods. Relative to control, recombinant human MFGE8 (rhMFGE8) treatment increased 5-bromo-2'-deoxyuridine (BrdU) labeled new endothelial cells, reduced TUNUL-positive endothelial cells and elevated the expression of phosphatidylinositol 3-kinase (PI3K) and chemokine (C-X-C motif) ligand 12 (CXCL12), in the brains of SAH rats. These effects were reversed by MFGE8 RNA silencing, as well as following cilengitide and wortmannin intervention. These results suggest that MFGE8 promotes endothelial regeneration and mitigates endothelial DNA damage through the activation of the TIGβ5/PI3K/CXCL12 signaling pathway.

Neurovascular devices for the treatment of intracranial aneurysms: emerging and future technologies

Introduction: Despite numerous advances in the endovascular treatment of intracranial aneurysms (IAs), treatment in cases of wide-neck, complex configurations or branching locations remains challenging. Apart from the paradigm shift introduced by flow diverters, several other devices have seen the light or are under development in order to address these challenges.Areas covered: We performed a review of the novel implantable endovascular devices which have been introduced for the treatment of IAs, from 1 January 2014 to 1 September 2019, excluding classic flow diverter and intracranial stent designs.Expert opinion: Alternative designs have been proposed for the treatment of IAs at branching positions, which do not jail the side branches, with or without flow diversion effect, most of which with good initial outcomes. Endosaccular devices have also been proposed, some of which with lower initial total occlusion rates. Alternative materials such as biopolymers have also been proposed and are under bench research. Despite the challenges in the exploitation of some of the new devices, most of them seem to provide solutions to some current technical shortcomings. The exploitation of the biological phenomena and the physical properties of the devices will allow us to expand the therapeutic armamentarium for more complex IA cases.

An Injectable Nanocomposite Hydrogel for Potential Application of Vascularization and Tissue Repair

In this contribution, an injectable hydrogel was developed with chitosan, gelatin, β-glycerphosphate and Arg-Gly-Asp (RGD) peptide: this hydrogel is liquid in room temperature and rapidly gels at 37 °C; RGD peptide promises better growth microenvironment for various cells, especially endothelial cells (EC), smooth muscle cells (SMC) and mesenchymal stem cells (MSC). Both stromal cell-derived factor-1 (SDF-1) nanoparticle and vascular endothelial growth factor (VEGF) nanoparticles were loaded in the injectable hydrogel to simulate the natural nanoparticles in the extracellular matrix (ECM) to promote angiogenesis. In vitro EC/SMC and MSC/SMC co-culture experiment indicated that the nanocomposite hydrogel accelerated constructing embryonic form of blood vessels, and chick embryo chorioallantoic membrane model demonstrated its ability of improving cells migration and blood vessel regeneration. We injected this nanocomposite hydrogel into rat myocardial infarction (MI) model and the results indicated that the rats heart function recovered better compared control group. We hope this injectable nanocomposite hydrogel may possess wider application in tissue engineering.

Pleiotrophin: Analysis of the endothelialisation potential

PURPOSE

Endothelialisation of vascular substitutes, in fact, remains one of the most unsolved problems in cardiovascular diseases treatment. Stromal Derived Factor 1 (SDF-1) has been largely investigated as an endothelialisation promoter and Pleiotrophin is a promising alternative. Although it has been known to exert beneficial effects on different cell types, its potential as an inducer of proliferation and migration of endothelial cells was not investigated. Therefore, this work is aimed to compare the effects of Pleiotrophin on proliferation and migration of endothelial cells with respect to SDF-1.

MATERIALS/METHODS

Endothelial cell line EA.hy926 was treated with Pleiotrophin (50 ng/ml) or SDF-1 (50 ng/ml). Cell viability was evaluated by MTT assay and migration assays were performed in Transwell chambers. Wound healing potential was evaluated by scratch wound assay. CXCR4, RPTP β/ζ, PCNA and Rac1 expression was detected by Western Blot.

RESULTS

Interestingly, Pleiotrophin significantly increased the viability of the treated endothelial cells with respects to SDF-1. The migratory ability of the endothelial cells was also improved in the presence of Pleiotrophin with reference to the SDF-1 treatment. Moreover, Western Blot analysis showed how the treatment with Pleiotrophin can induce an increase in the expression of RPTP β/ζ, PCNA and Rac1 compared to SDF-1.

CONCLUSION

Due to the significant effects exerted on viability, migration and repair ability of endothelial cells compared to SDF-1, Pleiotrophin can be considered as an interesting molecule to promote re-endothelialisation.

Temporal cascade of inflammatory cytokines and cell-type populations in monocyte chemotactic protein-1 (MCP-1)-mediated aneurysm healing

BACKGROUND

We have previously shown that monocyte chemotactic protein-1 (MCP-1) promotes aneurysm healing.

OBJECTIVE

To determine the temporal cascade and durability of aneurysm healing.

METHODS

Murine carotid aneurysms were treated with MCP-1-releasing or poly(lactic-co-glycolic) acid (PLGA)-only coils. Aneurysm healing was assessed by quantitative measurements of intraluminal tissue ingrowth on 5 μm sections by blinded observers.

RESULTS

Aneurysm healing occurred in stages characteristic of normal wound healing. The 1st stage (day 3) was characterized by a spike in neutrophils and T cells. The 2nd stage (week 1) was characterized by an influx of macrophages and CD45+ cells significantly greater with MCP-1 than with PLGA (p<0.05). The third stage (week 2-3) was characterized by proliferation of smooth muscle cells and fibroblasts (greater with MCP-1 than with PLGA, p<0.05). The fourth stage (3-6 months) was characterized by leveling off of smooth muscle cells and fibroblasts. M1 macrophages were greater at week 1, whereas M2 macrophages were greater at weeks 2 and 3 with MCP-1 than with PLGA. Interleukin 6 was present early and increased through week 2 (p<0.05 compared with PLGA) then decreased and leveled off through 6 months. Tumour necrosis factor α was present early and remained constant through 6 months. MCP-1 and PLGA treatment had similar rates of tissue ingrowth at early time points, but MCP-1 had a significantly greater tissue ingrowth at week 3 (p<0.05), which persisted for 6 months.

CONCLUSIONS

The sequential cascade is consistent with an inflammatory model of injury, repair, and remodeling.

Autologous adipose-derived mesenchymal stem cells improve healing of coiled experimental saccular aneurysms: an angiographic and histopathological study

PURPOSE

Long-term occlusion of coiled aneurysms frequently fails, probably because of poor intrasaccular healing and inadequate endothelialization across the aneurysm neck. The purpose of this study was to determine if attachment of autologous mesenchymal stem cells (MSCs) to platinum coils would improve the healing response in an elastase-induced aneurysm model in rabbits.

MATERIALS AND METHODS

With approval from the institutional animal care and use committee, aneurysms were created in rabbits and embolized with control platinum coils (Axium; Medtronic) (n=6) or coils seeded ex vivo with autologous adipose-tissue MSCs (n=7). Aneurysmal occlusion after embolization was evaluated at 1 month with angiography. Histological samples were analyzed by gross imaging and graded on the basis of neck and dome healing on H&E staining. Fibrosis was evaluated using a ratio of the total area presenting collagen. Endothelialization of the neck was quantitatively analyzed using CD31 immunohistochemistry. χ² and Student's t-test were used to compare groups.

RESULTS

Healing score (11.5 vs 8.0, p=0.019), fibrosis ratio (10.3 vs 0.13, p=0.006) and endothelialization (902 262 μm² vs 31 810 μm², p=0.041) were significantly greater in the MSC group. The MSC group showed marked cellular proliferation and thrombus organization, with a continuous membrane bridging the neck of the aneurysm. Angiographic stable or progressive occlusion rate was significantly lower in the MSC group (0.00, 95% CI 0.00 to 0.41) compared with controls (0.67, 95% CI 0.22 to 0.96) (p=0.02).

CONCLUSIONS

Autologous MSCs attached to platinum coils significantly improve histological healing, as they result in improved neck endothelialization and collagen matrix formation within the aneurysm sac.