Adventitial injection of HA/SA hydrogel loaded with PLGA rapamycin nanoparticle inhibits neointimal hyperplasia in a rat aortic wire injury model

Advances in medical polyesters for vascular tissue engineering

Blood vessels are highly dynamic and complex structures with a variety of physiological functions, including the transport of oxygen, nutrients, and metabolic wastes. Their normal functioning involves the close and coordinated cooperation of a variety of cells. However, adverse internal and external environmental factors can lead to vascular damage and the induction of various vascular diseases, including atherosclerosis and thrombosis. This can have serious consequences for patients, and there is an urgent need for innovative techniques to repair damaged blood vessels. Polyesters have been extensively researched and used in the treatment of vascular disease and repair of blood vessels due to their excellent mechanical properties, adjustable biodegradation time, and excellent biocompatibility. Given the high complexity of vascular tissues, it is still challenging to optimize the utilization of polyesters for repairing damaged blood vessels. Nevertheless, they have considerable potential for vascular tissue engineering in a range of applications. This summary reviews the physicochemical properties of polyhydroxyalkanoate (PHA), polycaprolactone (PCL), poly-lactic acid (PLA), and poly(lactide-co-glycolide) (PLGA), focusing on their unique applications in vascular tissue engineering. Polyesters can be prepared not only as 3D scaffolds to repair damage as an alternative to vascular grafts, but also in various forms such as microspheres, fibrous membranes, and nanoparticles to deliver drugs or bioactive ingredients to damaged vessels. Finally, it is anticipated that further developments in polyesters will occur in the near future, with the potential to facilitate the wider application of these materials in vascular tissue engineering.

Targeted Delivery of Nanoparticles to Blood Vessels for the Treatment of Atherosclerosis

Atherosclerosis is a common form of cardiovascular disease, which is one of the most prevalent causes of death worldwide, particularly among older individuals. Surgery is the mainstay of treatment for severe stenotic lesions, though the rate of restenosis remains relatively high. Current medication therapy for atherosclerosis has limited efficacy in reversing the formation of atherosclerotic plaques. The search for new drug treatment options is imminent. Some potent medications have shown surprising therapeutic benefits in inhibiting inflammation and endothelial proliferation in plaques. Unfortunately, their use is restricted due to notable dose-dependent systemic side effects or degradation. Nevertheless, with advances in nanotechnology, an increasing number of nano-related medical applications are emerging, such as nano-drug delivery, nano-imaging, nanorobots, and so forth, which allow for restrictions on the use of novel atherosclerotic drugs to be lifted. This paper reviews new perspectives on the targeted delivery of nanoparticles to blood vessels for the treatment of atherosclerosis in both systemic and local drug delivery. In systemic drug delivery, nanoparticles inhibit drug degradation and reduce systemic toxicity through passive and active pathways. To further enhance the precise release of drugs, the localized delivery of nanoparticles can also be accomplished through blood vessel wall injection or using endovascular interventional devices coated with nanoparticles. Overall, nanotechnology holds boundless potential for the diagnosis and treatment of atherosclerotic diseases in the future.

Disturbed flow in the juxta-anastomotic area of an arteriovenous fistula correlates with endothelial loss, acute thrombus formation, and neointimal hyperplasia

Clinical failure of arteriovenous neointimal hyperplasia (NIH) fistulae (AVF) is frequently due to juxta-anastomotic NIH (JANIH). Although the mouse AVF model recapitulates human AVF maturation, previous studies focused on the outflow vein distal to the anastomosis. We hypothesized that the juxta-anastomotic area (JAA) has increased NIH compared with the outflow vein. AVF was created in C57BL/6 mice without or with chronic kidney disease (CKD). Temporal and spatial changes of the JAA were examined using histology and immunofluorescence. Computational techniques were used to model the AVF. RNA-seq and bioinformatic analyses were performed to compare the JAA with the outflow vein. The jugular vein to carotid artery AVF model was created in Wistar rats. The neointima in the JAA shows increased volume compared with the outflow vein. Computational modeling shows an increased volume of disturbed flow at the JAA compared with the outflow vein. Endothelial cells are immediately lost from the wall contralateral to the fistula exit, followed by thrombus formation and JANIH. Gene Ontology (GO) enrichment analysis of the 1,862 differentially expressed genes (DEG) between the JANIH and the outflow vein identified 525 overexpressed genes. The rat jugular vein to carotid artery AVF showed changes similar to the mouse AVF. Disturbed flow through the JAA correlates with rapid endothelial cell loss, thrombus formation, and JANIH; late endothelialization of the JAA channel correlates with late AVF patency. Early thrombus formation in the JAA may influence the later development of JANIH.NEW & NOTEWORTHY Disturbed flow and focal endothelial cell loss in the juxta-anastomotic area of the mouse AVF colocalizes with acute thrombus formation followed by late neointimal hyperplasia. Differential flow patterns between the juxta-anastomotic area and the outflow vein correlate with differential expression of genes regulating coagulation, proliferation, collagen metabolism, and the immune response. The rat jugular vein to carotid artery AVF model shows changes similar to the mouse AVF model.

Adventitial delivery of miR-145 to treat intimal hyperplasia post vascular injuries through injectable and in-situ self-assembling peptide hydrogels

Intimal hyperplasia is a common lesion that can be observed in diverse vascular diseases. Drug-eluting stents and drug-coated balloons, which can release anti-proliferative agents to inhibit smooth muscle cell (SMC) proliferation, are developed to prevent intimal hyperplasia. However, these intervention devices still cannot achieve satisfactory clinical outcomes. In contrast to endovascular drug delivery, vascular adventitial drug delivery is a new strategy. To develop a vascular adventitial drug delivery system to treat intimal hyperplasia post vascular injuries, we loaded miR-145-5p-agomir (miR-145) into an injectable and in-situ self-assembling RAD peptide hydrogel. In vitro data showed that the miR-145 could be well incorporated into the RAD peptide hydrogels and released in a slow and controlled manner. The released miR-145 could transfect SMCs successfully, and the transfected SMCs exhibited a reduced migration capacity and higher expressions of SMC contractile biomarkers as compared to the non-transfected SMCs. In vivo data showed that the retention of the miR-145 was greatly elongated by the RAD peptide hydrogels. In addition, the application of the miR-145-loaded RAD peptide hydrogels surrounding injured arteries decreased the proliferative SMCs, promoted the regeneration of endothelium, reduced the macrophage infiltration, inhibited the neointimal formation and prevented adverse ECM remodeling via downregulation of KLF4 expression. The RAD peptide hydrogels loaded with miR-145 can successfully inhibit intimal hyperplasia after vascular injuries and thus hold great potential as an innovative extravascular drug delivery approach to treat vascular diseases. STATEMENT OF SIGNIFICANCE: Intimal hyperplasia is a common lesion that can be observed in diverse vascular diseases. Drug-eluting stents and drug-coated balloons, which can release anti-proliferative agents to inhibit smooth muscle cell (SMC) proliferation, are developed to prevent intimal hyperplasia. However, these intervention devices still cannot achieve satisfactory clinical outcomes. In contrast to endovascular drug delivery, vascular adventitial drug delivery is a new strategy. Our work here demonstrates that the RAD peptide hydrogels loaded with miR-145-5p-agomir (miR-145) can successfully reverse intimal hyperplasia after vascular injuries and thus hold great potential as an innovative vascular adventitial drug delivery approach to treat vascular diseases. Our work proposes a possible paradigm shift from endovascular drug delivery to extravascular drug delivery for vascular disorder treatment.

FoxO1 is a negative regulator of neointimal hyperplasia in a rat model of patch angioplasty

Neointimal hyperplasia persists as a barrier following vascular interventions. Forkhead Box O1 (FoxO1) is a transcription factor that possesses a distinctive fork head domain and indirectly contributes to various physiological processes. FoxO1 expression and signaling also impact the energy metabolism of vascular smooth muscle cells, potentially influencing neointimal hyperplasia. Our hypothesis is that FoxO1 inhibits neointimal hyperplasia in a rat patch angioplasty model. Four groups were compared in a rat aorta patch angioplasty model: the control group without treatment, patches coated with AS184286 (a FoxO1 inhibitor) in a PLGA matrix, patches coated with FoxO1 in a PLGA matrix, and patches coated with MLN0905 (a PLK1 inhibitor) in a PLGA matrix. The patches were harvested on Day 14 and subjected to analysis. FoxO1-positive and p-FoxO1 cells were observed after patch angioplasty. The addition of FoxO1 through patches coated with exogenous FoxO1 protein in a PLGA matrix significantly inhibited neointimal thickness (p = 0.0012). The treated groups exhibited significantly lower numbers of CD3 (p = 0.0003), CD45 (p < 0.0001), and PCNA (p < 0.0001)-positive cells. PLK1 is an upstream transcriptional regulator of FoxO1, governing the expression and function of FoxO1. MLN0905 PLGA-coated patches exhibited comparable reductions in neointimal thickness and inflammatory cell accumulation. FoxO1 represents a promising therapeutic strategy for inhibiting neointimal hyperplasia.

Decellularized fish swim bladder patch loaded with mesenchymal stem cells inhibits neointimal hyperplasia

We previously showed decellularized fish swim bladder can be used as vascular patch and tube graft in rats, mesenchymal stem cells (MSCs) have showed the capability to inhibit neointimal hyperplasia in different animal models. We hypothesized that decellularized fish swim bladder patch loaded with MSCs (bioinspired patch) can inhibit neointimal hyperplasia in a rat aortic patch angioplasty model. Rat MSCs were grown in vitro and flow cytometry was used to confirm their quality. 3.6 × 10⁵ MSCs were mixed into 100 μl of sodium alginate (SA)/hyaluronic acid (HA) hydrogel, two layers of fish swim bladders (5 mm × 5 mm) were sutured together, bioinspired patch was created by injection of hydrogel with MSCs into the space between two layers of fish swim bladder patches. Decellularized rat thoracic aorta patch was used as control. Patches were harvested at days 1 and 14 after implantation. Samples were examined by histology, immunohistochemistry, and immunofluorescence. The decellularized rat thoracic aorta patch and the fish swim bladder patch had a similar healing process after implantation. The bioinspired patch had a similar structure like native aorta. Bioinspired patch showed a decreased neointimal thickness (p = .0053), fewer macrophages infiltration (p = .0090), and lower proliferation rate (p = .0291) compared to the double layers fish swim bladder patch group. Decellularized fish swim bladder patch loaded with MSCs can inhibit neointimal hyperplasia effectively. Although this is a preliminary animal study, it may have a potential application in large animals or clinical research.

The Autotaxin-LPA Axis Emerges as a Novel Regulator of Smooth Muscle Cell Phenotypic Modulation during Intimal Hyperplasia

Neointimal hyperplasia is characterized by a loss of the contractile phenotype of vascular smooth muscle cells (VSMCs). Our group has recently shown that VSMC proliferation and migration are mediated by lysophosphatidic acid (LPA) during restenosis, but the role of autotaxin (ATX; lysophospholipase D), which produces LPA, remains unclear. Endothelial denudation of the mouse carotid artery was performed to induce neointimal hyperplasia, and the extent of damage caused by the ATX-LPA axis was assessed in VSMCs. We observed the upregulation of ATX activity (p < 0.0002) in the injured carotid artery using an AR2 probe fluorescence assay. Further, the tissue carotid LPA levels were elevated 2.7-fold in carotid vessels, augmenting neointimal hyperplasia. We used an electrical cell-substrate impedance sensor (ECIS) to measure VSMC proliferation and migration. Treatment with an ATX inhibitor (PF8380) or LPA receptor inhibitor (Ki16425) attenuated VSMC proliferation (extracellular signal-regulated kinases) activity and migration in response to recombinant ATX. Indeed, PF8380 treatment rescued the aggravated post-wire injury neointima formation of carotid arteries. The upregulation of ATX following vessel injury leads to LPA production in VSMCs, favoring restenosis. Our observations suggest that inhibition of the ATX-LPA axis could be therapeutically targeted in restenosis to minimize VSMC phenotypic modulation and inflammation after vascular injury.

Reprogramming of Rat Fibroblasts into Induced Neurons by Small-Molecule Compounds In Vitro and In Vivo

Cell replacement is a promising approach for neurodegenerative disease treatment. Somatic cells such as fibroblasts can be induced to differentiate into neurons by specific transcription factors; however, the potential of viral vectors used for reprogramming to integrate into the genome raises concerns about the potential clinical applications of this approach. Here, we directly reprogrammed rat embryonic skin fibroblasts into induced neurons (iNs) via six small-molecule compounds (SMs) (VPA, CHIR99021, forskolin, Y-27632, Repsox, and P7C3-A20). iNs exhibit typical neuronal morphology, and immunofluorescence showed that more than 96% of the iNs expressed the early neuronal marker class III beta-tubulin (TUJ1) and that more than 91% of iNs expressed the mature neuronal marker neuron-specific enolase (NSE) after 10 days of reprogramming. Quantitative real-time polymerase chain reaction also showed that most iNs expressed the dopaminergic neuron marker tyrosine hydroxylase, the neural marker Nur correlation factor 1, the (γ-aminobutyric acid, GABA) GABAergic neuronal marker GABA, and the cholinergic neuron marker choline acetyltransferase. In addition, we found that cell proliferation decreased during reprogramming and that protein synthesis increased initially and then decreased. SMs were mixed with hydrogels, and the hydrogels were implanted subcutaneously into the backs of rats. After 7 days, the TUJ1 and NSE proteins were expressed in surrounding tissues, indicating that SMs caused reprogramming in vivo. In summary, rat skin fibroblasts can be efficiently reprogrammed into iNs by SMs in vitro and in vivo.