Overexpression of Sema3a in myocardial infarction border zone decreases vulnerability of ventricular tachycardia post-myocardial infarction in rats

The proarrhythmogenic role of autonomics and emerging neuromodulation approaches to prevent sudden death in cardiac ion channelopathies

Ventricular arrhythmias in cardiac channelopathies are linked to autonomic triggers, which are sub-optimally targeted in current management strategies. Improved molecular understanding of cardiac channelopathies and cellular autonomic signalling could refine autonomic therapies to target the specific signalling pathways relevant to the specific aetiologies as well as the central nervous system centres involved in the cardiac autonomic regulation. This review summarizes key anatomical and physiological aspects of the cardiac autonomic nervous system and its impact on ventricular arrhythmias in primary inherited arrhythmia syndromes. Proarrhythmogenic autonomic effects and potential therapeutic targets in defined conditions including the Brugada syndrome, early repolarization syndrome, long QT syndrome, and catecholaminergic polymorphic ventricular tachycardia will be examined. Pharmacological and interventional neuromodulation options for these cardiac channelopathies are discussed. Promising new targets for cardiac neuromodulation include inhibitory and excitatory G-protein coupled receptors, neuropeptides, chemorepellents/attractants as well as the vagal and sympathetic nuclei in the central nervous system. Novel therapeutic strategies utilizing invasive and non-invasive deep brain/brain stem stimulation as well as the rapidly growing field of chemo-, opto-, or sonogenetics allowing cell-specific targeting to reduce ventricular arrhythmias are presented.

Semaphorin‑3A alleviates cardiac hypertrophy by regulating autophagy

Cardiac hypertrophy, characterized by cardiomyocyte enlargement, is an adaptive response of the heart to certain hypertrophic stimuli; however, prolonged hypertrophy results in cardiac dysfunction and can ultimately cause heart failure. The present study evaluated the role of semaphorin-3A (Sema3A), a neurochemical inhibitor, in cardiac hypertrophy, utilizing an isoproterenol (ISO) induced H9c2 cell model. Cells were stained with rhodamine-phalloidin to assess the cell surface area and reverse transcription-quantitative PCR was performed to quantify mRNA expression levels of Sema3A, brain natriuretic factor (BNF) and β-myosin heavy chain (β-MHC). The protein expression levels of the autophagy-related proteins light chain 3 (LC3), p62 and Beclin-1, and the Akt/mTOR signaling pathway associated proteins Akt, phosphorylated (p)-Akt, mTOR, p-mTOR, 4E-binding protein 1 (4EBP1) and p-4EBP1 were semi-quantified using western blotting. Rapamycin, a canonical autophagy inducer, was administered to H9c2 cells to elucidate the regulatory mechanism of Sema3A. The results indicated significantly increased cell surface area and elevated BNF and β-MHC mRNA expression levels, increased LC3II/I ratio and Beclin-1 protein expression levels and significantly decreased p62 protein expression levels after treatment of H9c2 cardiomyocytes with ISO for 24 h. Sema3A overexpression improved ISO-induced hypertrophy in H9c2 cells, indicated by decreased cell surface area and reduced BNF and β-MHC mRNA expression levels. Moreover, Sema3A overexpression inhibited ISO-induced autophagy in H9c2 cells, indicated by decreased LC3II/I ratio and Beclin-1 protein expression levels and increased p62 protein expression levels. The autophagy activator rapamycin partially inhibited the protective effect of Sema3A on ISO-induced hypertrophy. Sema3A overexpression suppressed the decrease of the protein expression levels of p-Akt, mTOR and their downstream target 4EBP1, which is induced by ISO. Collectively, these results suggested Sema3A prevented ISO-induced cardiac hypertrophy by inhibiting autophagy via the Akt/mTOR signaling pathway.

Pathophysiological functions of semaphorins in the sympathetic nervous system

Upon exposure to external stressors, the body senses them and activates the sympathetic nervous system (SNS) to maintain the homeostasis, which is known as the "fight-or-flight" response. Recent studies have revealed that the SNS also plays pivotal roles in regulating immune responses, such as hematopoiesis, leukocyte mobilization, and inflammation. Indeed, overactivation of the SNS causes many inflammatory diseases, including cardiovascular diseases, metabolic disorders, and autoimmune diseases. However, the molecular basis essential for SNS-mediated immune regulation is not completely understood. In this review, we focus on axon guidance cues, semaphorins, which play multifaceted roles in neural and immune systems. We summarize the functions of semaphorins in the crosstalk between the SNS and the immune system, exploring its pathophysiological roles.

Sema3A alleviates viral myocarditis by modulating SIRT1 to regulate cardiomyocyte mitophagy

Viral myocarditis (VMC) is a common myocardial inflammatory disease characterized by inflammatory cell infiltration and cardiomyocyte necrosis. Sema3A was reported to reduce cardiac inflammation and improve cardiac function after myocardial infarction, but its role in VMC remains to be explored. Here, a VMC mouse model was established by infection with CVB3, and Sema3A was overexpressed in vivo by intraventricular injection of an adenovirus-mediated Sema3A expression vector (Ad-Sema3A). We found that Sema3A overexpression attenuated CVB3-induced cardiac dysfunction and tissue inflammation. And Sema3A also reduced macrophage accumulation and NLRP3 inflammasome activation in the myocardium of VMC mice. In vitro, LPS was used to stimulate primary splenic macrophages to mimic the macrophage activation state in vivo. Activated macrophages were co-cultured with primary mouse cardiomyocytes to evaluate macrophage infiltration-induced cardiomyocyte damage. Ectopic expression of Sema3A in cardiomyocytes effectively protected cardiomyocytes from activated macrophage-induced inflammation, apoptosis, and ROS accumulation. Mechanistically, cardiomyocyte-expressed Sema3A mitigated macrophage infiltration-caused cardiomyocyte dysfunction by promoting cardiomyocyte mitophagy and hindering NLRP3 inflammasome activation. Furthermore, NAM (a SIRT1 inhibitor) reversed the protective effect of Sema3A against activated macrophage-induced cardiomyocyte dysfunction by suppressing cardiomyocyte mitophagy. In conclusion, Sema3A promoted cardiomyocyte mitophagy and suppressed inflammasome activation by regulating SIRT1, thereby attenuating macrophage infiltration-induced cardiomyocyte injury in VMC.

The role of semaphorins in cardiovascular diseases: Potential therapeutic targets and novel biomarkers

Semaphorins (Semas), which belongs to the axonal guidance molecules, include 8 classes and could affect axon growth in the nervous system. Recently, semaphorins were found to regulate other pathophysiological processes, such as immune response, oncogenesis, tumor angiogenesis, and bone homeostasis, through binding with their plexin and neuropilin receptors. In this review, we summarized the detailed role of semaphorins and their receptors in the pathological progression of various cardiovascular diseases (CVDs), highlighting that semaphorins may be potential therapeutic targets and novel biomarkers for CVDs.

Myocardial Infarction and AGT p.Thr174Met Polymorphism: A Meta-Analysis of 7657 Subjects

Background

It has been suggested that the angiotensinogen (AGT) gene rs4762 (p.Thr174Met) polymorphism might be associated with myocardial infarction (MI) risk, but the study results are still debatable. Objective and Methods. In order to explore the relationship between AGT p.Thr174Met polymorphism and MI risk, the current meta-analysis involving 7657 subjects from 11 individual studies was conducted.

Results

A significant association between AGT p.Thr174Met polymorphism and MI was found under recessive (OR: 2.26, 95% CI: 1.35-3.77, P = 0.002), dominant (OR: 1.131, 95% CI: 1.016-1.260, P = 0.024), codominant (OR: 2.198, 95% CI: 1.334-3.621, P = 0.002), and additive (OR: 1.363, 95% CI: 1.132-1.641, P = 0.001) genetic models. In the Asian subgroup, significantly increased MI risk was found under all genetic models (P < 0.05). No significant association between AGT p.Thr174Met polymorphism and MI was found under all genetic models in the Caucasian subgroup (P > 0.05).

Conclusions

AGT p.Thr174Met variant might increase MI risk, especially within the Asian population. The Met174 allele of AGT p.Thr174Met might confer the risk for MI.

Upregulated lncRNA Pvt1 may be important for cardiac remodeling at the infarct border zone

Myocardial infarction (MI) is a leading cause of mortality due to progression to ventricular arrhythmias (VAs) or heart failure (HF). Cardiac remodeling at the infarct border zone (IBZ) is the primary contributor for VAs or HF. Therefore, genes involved in IBZ remodeling may be potential targets for the treatment of MI, but the mechanism remains unclear. The present study aimed to explain the molecular mechanisms of IBZ remodeling based on the roles of long non-coding RNAs (lncRNAs). After downloading miRNA (GSE76592) and mRNA/lncRNA (GSE52313) datasets from the Gene Expression Omnibus database, 23 differentially expressed miRNAs (DEMs), 2,563 genes (DEGs) and 168 lncRNAs (DELs) were identified between IBZ samples of MI mice and sham controls. A total of 483 DEGs were predicted to be regulated by 23 DEMs, among which Itgam, Met and TNF belonged to hub genes after five topological parameters were calculated for genes in the protein-protein interaction network. These hub genes-associated DEMs (mmu-miR-181a, mmu-miR-762) can also interact with six DELs (Gm15832, Gas5, Gm6634, Pvt1, Gm14636 and A330023F24Rik) to constitute the competing endogenous RNA (ceRNA) axes. Furthermore, a co-expression network was constructed based on the co-expression pairs between 44 DELs and 297 DEGs, in which Pvt1 and Bst1 were overlapped with the ceRNA network. Thus, Bst1-associated ceRNA (Pvt1-mmu-miR-181a-Bst1) and co-expression (Pvt-Bst1) axes were also pivotal for MI. Accordingly, Pvt1 may be a crucial lncRNA for modification of cardiac remodeling in the IBZ after MI and may function by acting as a ceRNA for miR-181a to regulate TNF/Met/Itgam/Bst1 or by co-expressing with Bst1.

Human epicardium-derived cells reinforce cardiac sympathetic innervation

RATIONALE

After cardiac damage, excessive neurite outgrowth (sympathetic hyperinnervation) can occur, which is related to ventricular arrhythmias/sudden cardiac death. Post-damage reactivation of epicardium causes epicardium-derived cells (EPDCs) to acquire a mesenchymal character, contributing to cardiac regeneration. Whether EPDCs also contribute to cardiac re/hyperinnervation, is unknown.

AIM

To investigate whether mesenchymal EPDCs influence cardiac sympathetic innervation.

METHODS AND RESULTS

Sympathetic ganglia were co-cultured with mesenchymal EPDCs and/or myocardium, and neurite outgrowth and sprouting density were assessed. Results showed a significant increase in neurite density and directional (i.e. towards myocardium) outgrowth when ganglia were co-cultured with a combination of EPDCs and myocardium, as compared to cultures with EPDCs or myocardium alone. In absence of myocardium, this outgrowth was not directional. Neurite differentiation of PC12 cells in conditioned medium confirmed these results via a paracrine effect, in accordance with expression of neurotrophic factors in myocardial explants co-cultured with EPDCs. Of interest, EPDCs increased the expression of nerve growth factor (NGF) in cultured, but not in fresh myocardium, possibly due to an "ischemic state" of cultured myocardium, supported by TUNEL and Hif1α expression. Cardiac tissues after myocardial infarction showed robust NGF expression in the infarcted, but not remote area.

CONCLUSION

Neurite outgrowth and density increases significantly in the presence of EPDCs by a paracrine effect, indicating a new role for EPDCs in the occurrence of sympathetic re/hyperinnervation after cardiac damage.

Long non-coding RNA GAS5 reduces cardiomyocyte apoptosis induced by MI through sema3a

OBJECTIVE

To investigate the role of GAS5 on cardiomyocyte apoptosis.

METHODS

Myocardial infarction (MI) model was established by the left-anterior descending coronary artery ligation. Norepinephrine (NE) was used to induce cardiomyocyte apoptosis. GAS5 levels and mRNA expressions of Semaphorin 3a (sema3a) were measured by qRT-PCR. Protein level of sema3a was detected by Western blotting. Cardiomyocyte apoptosis was detected by flow cytometry assay. RNA pull-down and RIP assay were used to verify the combination between GAS5 and sema3a. Infarct size was measured by TTC staining.

RESULTS

GAS5 expression was increased in infarct boundary zone of MI group, while sema3a protein expression was decreased. Moreover, GAS5 expression in cardiomyocyte induced by NE was higher than control group, while sema3a protein expression was lower than control group. In addition, GAS5 could negatively regulate sema3a protein expression. pcDNA-GAS5 reversed cardiomyocyte apoptosis induced by NE, while pcDNA-sema3a countered the inhibitory effect. In animal experiment, overexpression of GAS5 decreased sema3a protein expression and reduced infarct size.

CONCLUSION

GAS5 could ameliorate cardiomyocyte apoptosis induced by MI via down-regulating sema3a.

Neuropilin 1 ameliorates electrical remodeling at infarct border zones in rats after myocardial infarction

BACKGROUND

Electrical remodeling at infarct border zone (IBZ) has been shown to contribute to the occurrence of ventricular arrhythmias after myocardial infarction (MI). Sema3A has been demonstrated to reduce the inducibility of ventricular arrhythmias. Neuropilin 1 (NRP1) is the receptor of Sema3A. In the present study, we investigated whether treatment with NRP1 can ameliorate electrical remodeling at IBZ after MI.

METHODS AND RESULTS

Wistar rats underwent sham operation (n = 20), the ligation of left coronary artery (MI group, n = 30), MI with control adenovirus (Ad group, n = 30), and MI with NRP1 adenovirus (NRP1 group, n = 30). Eight weeks after treatment, electrophysiological properties including heart rate variability (HRV), monophasic action potential duration (MAPD), effective refractory period (ERP) and the inducibility of ventricular arrhythmias and the expression of arrhythmia-related ion channel proteins including Kv4.2, Kv4.3, KChIP2 and Kir2.1 at the IBZ of the left ventricle were examined. Compared with the MI or Ad group, NRP1 significantly increased HRV and shortened MAPD and ERP (all P < 0.05). Inducibility of VT by electrophysiological study was significantly lower in the NRP1 group than in the MI or Ad group (P < 0.05). The expression levels of Kv4.2, Kv4.3, KChIP2 and Kir2.1 proteins were significantly decreased in MI group and Ad group. In contrast, the expression levels of these proteins were restored in NRP1 group, which may represent the molecular basis of the NRP1-mediated inhibition of electrical remodeling.

CONCLUSIONS

NRP1 can ameliorate electrical remodeling at IBZ after MI.

Cardiac Innervation and the Autonomic Nervous System in Sudden Cardiac Death

Neural remodeling in the autonomic nervous system contributes to sudden cardiac death. The fabric of cardiac excitability and propagation is controlled by autonomic innervation. Heart disease predisposes to malignant ventricular arrhythmias by causing neural remodeling at the level of the myocardium, the intrinsic cardiac ganglia, extracardiac intrathoracic sympathetic ganglia, extrathoracic ganglia, spinal cord, and the brainstem, as well as the higher centers and the cortex. Therapeutic strategies at each of these levels aim to restore the balance between the sympathetic and parasympathetic branches. Understanding this complex neural network will provide important therapeutic insights into the treatment of sudden cardiac death.

Sema3A promotes the resolution of cardiac inflammation after myocardial infarction

Optimal healing after myocardial infarction requires not only the induction of inflammation, but also its timely resolution. In patients, 30 days post myocardial infarction, circulating monocytes have increased expression of Semaphorin3A (Sema3A) as compared to directly after admission. This increased expression coincides with increased expression of Cx3CR1—a marker of non-classical monocytes that are important for immune resolution hence proper wound healing. In mice, the expression of Sema3A also increases in response to myocardial ischemia being expressed by infiltrating leukocytes. Comparing Sema3A heterozygote (HZ) and wild type (WT) mice post myocardial infarction, revealed increased presence of leukocytes in the cardiac tissues of HZ mice as compared to WT, with no differences in capillary density, collagen deposition, cardiomyocyte surface area, chemokine—or adhesion molecules expression. Whilst infarct sizes were similar 14 days after myocardial infarction in both genotypes, Sema3A HZ mice had thinner infarcts and reduced cardiac function as compared to their WT littermates. In vitro experiments were conducted to study the role of Sema3A in inflammation and resolution of inflammation as a potential explanation for the differences in leukocyte recruitment and cardiac function observed in our in vivo experiments. Here, recombinant Sema3A protein was able to affect the pro-inflammatory state of cultured bone marrow derived macrophages. First, the pro-inflammatory state was altered by the induced apoptosis of classical macrophages in the presence of Sema3A. Second, Sema3A promoted the polarization of classical macrophages to resolution-phase macrophages and enhanced their efferocytotic ability, findings that were reflected in the infarcted cardiac tissue of the Sema3A HZ mice. Finally, we demonstrated that besides promoting resolution of inflammation, Sema3A was also able to retard the migration of monocytes to the myocardium. Collectively our data demonstrate that Sema3A reduces cardiac inflammation and improves cardiac function after myocardial infarction by promoting the resolution of inflammation.

Class 3 semaphorins in cardiovascular development

Secreted class 3 semaphorins (Sema3), which signal through holoreceptor complexes that are formed by different subunits, such as neuropilins (Nrps), proteoglycans, and plexins, were initially characterized as fundamental regulators of axon guidance during embryogenesis. Subsequently, Sema3A, Sema3C, Sema3D, and Sema3E were discovered to play crucial roles in cardiovascular development, mainly acting through Nrp1 and Plexin D1, which funnels the signal of multiple Sema3 in vascular endothelial cells. Mechanistically, Sema3 proteins control cardiovascular patterning through the enzymatic GTPase-activating-protein activity of the cytodomain of Plexin D1, which negatively regulates the function of Rap1, a small GTPase that is well-known for its ability to drive vascular morphogenesis and to elicit the conformational activation of integrin adhesion receptors.

Semaphorin 3A attenuates cardiac autonomic disorders and reduces inducible ventricular arrhythmias in rats with experimental myocardial infarction

BACKGROUND

To investigate the effects of semaphorin 3A (sema 3A) on cardiac autonomic regulation and subsequent ventricular arrhythmias (VAs) in post-infarcted hearts.

METHOD AND RESULTS

In order to explore the functions of sema 3A in post-infarcted hearts, lentivirus-Sema 3A-shRNA and negative control vectors were delivered to the peri-infarcted myocardium rats respectively. Meanwhile, recombinant sema 3A and control (0.9% NaCl solution) were injected intravenously into infarcted rats to test the therapeutic potential of sema 3A. Results indicated that levels of sema 3A were higher in post-infarcted hearts compared with sham rats. However, sema 3A silencing leaded to sympathetic hyperinnervation, increased myocardial norepinephrine (NE) content and inducible VAs. Conversely, the intravenous administration of sema 3A to infarcted rats reduced sympathetic nerve sprouting, improved cardiac autonomic regulation, and decreased the incidence of inducible VAs. However, both infarct size and cardiac function were similar among infarcted hearts.

CONCLUSIONS

The upregulation and administration of sema 3A exerted beneficial effects on infarction-induced cardiac autonomic disorders by increasing cardiac electrical stability and reducing VAs. Sema 3A might be a potential therapeutic agent for cardiac autonomic abnormalities induced arrhythmias.

Cardiac Sympathetic Nerve Sprouting and Susceptibility to Ventricular Arrhythmias after Myocardial Infarction

Ventricular arrhythmogenesis is thought to be a common cause of sudden cardiac death following myocardial infarction (MI). Nerve remodeling as a result of MI is known to be an important genesis of life-threatening arrhythmias. It is hypothesized that neural modulation might serve as a therapeutic option of malignant arrhythmias. In fact, left stellectomy or β-blocker therapy is shown to be effective in the prevention of ventricular tachyarrhythmias (VT), ventricular fibrillation (VF), and sudden cardiac death (SCD) after MI both in patients and in animal models. Results from decades of research already evidenced a positive relationship between abnormal nerve density and ventricular arrhythmias after MI. In this review, we summarized the molecular mechanisms involved in cardiac sympathetic rejuvenation and mechanisms related to sympathetic hyperinnervation and arrhythmogenesis after MI and analyzed the potential therapeutic implications of nerve sprouting modification for ventricular arrhythmias and SCD control.

Semaphorin 3a transfection into the left stellate ganglion reduces susceptibility to ventricular arrhythmias after myocardial infarction in rats

AIMS

Myocardial infarction (MI) induces neural remodelling of the left stellate ganglion (LSG), which may contribute to ischaemia-induced arrhythmias. The neural chemorepellent Semaphorin 3a (Sema3a) has been identified as a negative regulator of sympathetic innervation in the LSG and heart. We previously reported that overexpression of Sema3a in the border zone could reduce the arrhythmogenic effects of cardiac sympathetic hyperinnervation post-MI. This study investigated whether Sema3a overexpression within the LSG confers an antiarrhythmic effect after MI through decreasing extra- and intra-cardiac neural remodelling.

METHODS AND RESULTS

Sprague-Dawley rats were subjected to MI, and randomly allocated to intra-LSG microinjection of either phosphate-buffered saline (PBS), adenovirus encoding green fluorescent protein (AdGFP), or adenovirus encoding Sema3a (AdSema3a). Sham-operated rats served as controls. Two weeks after infarction, MI-induced nerve sprouting and sympathetic hyperinnervation in the LSG and myocardium were significantly attenuated by intra-LSG injection with AdSema3a, as assessed by immunohistochemistry and western blot analysis of growth-associated protein 43 and tyrosine hydroxylase. This was also confirmed by sympathetic nerve function changes assessed by cardiac norepinephrine content. Additionally, intra-LSG injection with AdSema3a alleviated MI-induced accumulation of dephosphorylated connexin 43 in the infarct border zone. Furthermore, Sema3a overexpression in the LSG reduced the incidence of inducible ventricular tachyarrhythmia by programmed electrical stimulation post-MI, and arrhythmia scores were significantly lower in the AdSema3a group than in the PBS and AdGFP groups.

CONCLUSION

Semaphorin 3a overexpression in the LSG ameliorates the inducibility of ventricular arrhythmias after MI, mainly through attenuation of neural remodelling within the cardiac-neuraxis.

Cardiac innervation and sudden cardiac death

Afferent and efferent cardiac neurotransmission via the cardiac nerves intricately modulates nearly all physiological functions of the heart (chronotropy, dromotropy, lusitropy, and inotropy). Afferent information from the heart is transmitted to higher levels of the nervous system for processing (intrinsic cardiac nervous system, extracardiac-intrathoracic ganglia, spinal cord, brain stem, and higher centers), which ultimately results in efferent cardiomotor neural impulses (via the sympathetic and parasympathetic nerves). This system forms interacting feedback loops that provide physiological stability for maintaining normal rhythm and life-sustaining circulation. This system also ensures that there is fine-tuned regulation of sympathetic-parasympathetic balance in the heart under normal and stressed states in the short (beat to beat), intermediate (minutes to hours), and long term (days to years). This important neurovisceral/autonomic nervous system also plays a major role in the pathophysiology and progression of heart disease, including heart failure and arrhythmias leading to sudden cardiac death. Transdifferentiation of neurons in heart failure, functional denervation, cardiac and extracardiac neural remodeling has also been identified and characterized during the progression of disease. Recent advances in understanding the cellular and molecular processes governing innervation and the functional control of the myocardium in health and disease provide a rational mechanistic basis for the development of neuraxial therapies for preventing sudden cardiac death and other arrhythmias. Advances in cellular, molecular, and bioengineering realms have underscored the emergence of this area as an important avenue of scientific inquiry and therapeutic intervention.

Semaphorin signaling in cardiovascular development

Semaphorins were originally identified as neuronal guidance molecules mediating their attractive or repulsive signals by forming complexes with plexin and neuropilin receptors. Subsequent research has identified functions for semaphorin signaling in many organs and tissues outside of the nervous system. Vital roles for semaphorin signaling in vascular patterning and cardiac morphogenesis have been demonstrated, and impaired semaphorin signaling has been associated with various human cardiovascular disorders, including persistent truncus arteriosus, sinus bradycardia and anomalous pulmonary venous connections. Here, we review the functions of semaphorins and their receptors in cardiovascular development and disease and highlight important recent discoveries in the field.

Semaphorins in cardiovascular medicine

During organogenesis, patterning is primarily achieved by the combined actions of morphogens. Among these, semaphorins represent a general system for establishing the appropriate wiring architecture of biological nets. Originally discovered as evolutionarily conserved steering molecules for developing axons, subsequent studies on semaphorins expanded their functions to the cardiovascular and immune systems. Semaphorins participate in cardiac organogenesis and control physiological vasculogenesis and angiogenesis, which result from a balance between pro- and anti-angiogenic signals. These signals are altered in several diseases. In this review, we discuss the role of semaphorins in vascular biology, emphasizing the mechanisms by which these molecules control vascular patterning and lymphangiogenesis, as well as in genetically inherited and degenerative vascular diseases.