Simvastatin increases circulating endothelial progenitor cells and reduces the formation and progression of diabetic retinopathy in rats

Beyond VEGF: Angiopoietin-Tie Signaling Pathway in Diabetic Retinopathy

Complications from diabetic retinopathy such as diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) constitute leading causes of preventable vision loss in working-age patients. Since vascular endothelial growth factor (VEGF) plays a major role in the pathogenesis of these complications, VEGF inhibitors have been the cornerstone of their treatment. Anti-VEGF monotherapy is an effective but burdensome treatment for DME. However, due to the intensive and burdensome treatment, most patients in routine clinical practice are undertreated, and therefore, their outcomes are compromised. Even in adequately treated patients, persistent DME is reported anywhere from 30% to 60% depending on the drug used. PDR is currently treated by anti-VEGF, panretinal photocoagulation (PRP) or a combination of both. Similarly, a number of eyes, despite these treatments, continue to progress to tractional retinal detachment and vitreous hemorrhage. Clearly there are other molecular pathways other than VEGF involved in the pathogenesis of DME and PDR. One of these pathways is the angiopoietin-Tie signaling pathway. Angiopoietin 1 (Ang1) plays a major role in maintaining vascular quiescence and stability. It acts as a molecular brake against vascular destabilization and inflammation that is usually promoted by angiopoietin 2 (Ang2). Several pathological conditions including chronic hyperglycemia lead to Ang2 upregulation. Recent regulatory approval of the bi-specific antibody, faricimab, may improve long term outcomes in DME. It targets both the Ang/Tie and VEGF pathways. The YOSEMITE and RHINE were multicenter, double-masked, randomized non-inferiority phase 3 clinical trials that compared faricimab to aflibercept in eyes with center-involved DME. At 12 months of follow-up, faricimab demonstrated non-inferior vision gains, improved anatomic outcomes and a potential for extended dosing when compared to aflibercept. The 2-year results of the YOSEMITE and RHINE trials demonstrated that the anatomic and functional results obtained at the 1 year follow-up were maintained. Short term outcomes of previously treated and treatment-naive eyes with DME that were treated with faricimab during routine clinical practice suggest a beneficial effect of faricimab over other agents. Targeting of Ang2 has been reported by several other means including VE-PTP inhibitors, integrin binding peptide and surrobodies.

Single Intraosseous Simvastatin Application Induces Endothelial Progenitor Cell Mobilization and Therapeutic Angiogenesis in a Diabetic Hindlimb Ischemia Rat Model

BACKGROUND

Endothelial progenitor cells have shown the ability to enhance neovascularization. In this study, the authors tested whether intraosseous delivery of simvastatin could mobilize endothelial progenitor cells and enhance recovery in a hindlimb ischemia model.

METHODS

There are eight groups of rats in this study: normal control; type 1 diabetes mellitus control group control without drug intervention; and type 1 diabetes mellitus rats that randomly received intraosseous simvastatin (0, 0.5, or 1 mg) or oral simvastatin administration (0, 20, or 400 mg). All type 1 diabetes mellitus rats had induced hindlimb ischemia. The number of endothelial progenitor cells in peripheral blood, and serum markers, were detected. The recovery of blood flow at 21 days after treatment was used as the main outcome.

RESULTS

The authors demonstrated that endothelial progenitor cell mobilization was increased in the simvastatin 0.5- and 1-mg groups compared with the type 1 diabetes mellitus control and simvastatin 0-mg groups at 1, 2, and 3 weeks. Serum vascular endothelial growth factor levels were significantly increased at 2 weeks in the simvastatin 0.5- and 1-mg groups, in addition to the increase of the blood flow and the gastrocnemius weight at 3 weeks. Similar increase can also been seen in simvastatin 400 mg orally but not in simvastatin 20 mg orally.

CONCLUSION

These findings demonstrate that a single intraosseous administration of simvastatin mobilized endothelial progenitor cells at a dose one-hundredth of the required daily oral dose in rats, and this potent mobilization of endothelial progenitor cells markedly improved diabetic limb ischemia by means of neovascularization.

Association between Statins and Retinal Vascular Occlusion: A Population-Based Cohort Study

Retinal vascular occlusion (RVO), including retinal arterial occlusion and retinal vein occlusion, is a common retinal vascular disease that causes visual disturbance. The exact pathogenesis of RVO remains unclear. In all types of RVO patients, hyperlipidemia is more than twofold more common than in controls. Statins have been used to control blood cholesterol levels and have been found to reduce the risk of cardiovascular morbidity and mortality. Moreover, the immunomodulatory functions of statins may play a role in treating inflammatory diseases. This study aimed to evaluate whether patients taking statins have a lower risk of developing RVO compared to patients not taking statins. Adult patients with statins usage on the index date identified from the Taiwan National Health Insurance Research Database (NHIRD) between 2000 and 2013 were included. A threefold matched group was selected using age, sex, and year of index date for comparison. During the mean follow-up period of 12.87 ± 1.88 years, the cumulative incidence of RVO was significantly lower in the statin-user group (29.96 per 105 person-years [PYs]) than in the non-statin-user group (39.35 per 105 PYs). The results showed a lower cumulative incidence rate of RVO in patients prescribed statins than in those not prescribed statins (log-rank test, p = 0.020). The adjusting hazard ratio (HR) was significantly greater for RVO in the statin-user group (adjusted HR, 0.704; 95% CI, 0.591-0.873). Statin users had a decreased risk for all types of RVO development, including central retinal artery occlusion, arterial branch occlusion, central retinal vein occlusion, and branch retinal vein occlusion. In conclusion, patients undergoing statin treatment have a lower risk of developing RVO compared to patients not taking statins.

Redox Regulation of Microvascular Permeability: IL-1β Potentiation of Bradykinin-Induced Permeability Is Prevented by Simvastatin

Antioxidant effects of statins have been implicated in the reduction in microvascular permeability and edema formation in experimental and clinical studies. Bradykinin (Bk)-induced increases in microvascular permeability are potentiated by IL-1β; however, no studies have examined the protection afforded by statins against microvascular hyperpermeability. We investigated the effects of simvastatin pretreatment on albumin–fluorescein isothiocyanate conjugate (FITC-albumin) permeability in post-capillary venules in rat cremaster muscle. Inhibition of nitric oxide synthase with L-NAME (10µM) increased basal permeability to FITC-albumin, which was abrogated by superoxide dismutase and catalase. Histamine-induced (1 µM) permeability was blocked by L-NAME but unaffected by scavenging reactive oxygen species with superoxide dismutase (SOD) and catalase. In contrast, bradykinin-induced (1–100 nM) permeability increases were unaffected by L-NAME but abrogated by SOD and catalase. Acute superfusion of the cremaster muscle with IL-1β (30 pM, 10 min) resulted in a leftward shift of the bradykinin concentration–response curve. Potentiation by IL-1β of bradykinin-induced microvascular permeability was prevented by the nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) inhibitor apocynin (1 µM). Pretreatment of rats with simvastatin (5 mg·kg⁻¹, i.p.) 24 h before permeability measurements prevented the potentiation of bradykinin permeability responses by IL-1β, which was not reversed by inhibition of heme oxygenase-1 with tin protoporphyrin IX (SnPP). This study highlights a novel mechanism by which simvastatin prevents the potentiation of bradykinin-induced permeability by IL-1β, possibly by targeting the assembly of NADPH oxidase subunits. Our findings highlight the therapeutic potential of statins in the prevention and treatment of patients predisposed to inflammatory diseases.

Retinal Physiology and Circulation: Effect of Diabetes

In this article, we present a discussion of diabetes and its complications, including the macrovascular and microvascular effects, with the latter of consequence to the retina. We will discuss the anatomy and physiology of the retina, including aspects of metabolism and mechanisms of oxygenation, with the latter accomplished via a combination of the retinal and choroidal blood circulations. Both of these vasculatures are altered in diabetes, with the retinal circulation intimately involved in the pathology of diabetic retinopathy. The later stages of diabetic retinopathy involve poorly controlled angiogenesis that is of great concern, but in our discussion, we will focus more on several alterations in the retinal circulation occurring earlier in the progression of disease, including reductions in blood flow and a possible redistribution of perfusion that may leave some areas of the retina ischemic and hypoxic. Finally, we include in this article a more recent area of investigation regarding the diabetic retinal vasculature, that is, the alterations to the endothelial surface layer that normally plays a vital role in maintaining physiological functions. © 2020 American Physiological Society. Compr Physiol 10:933-974, 2020.

Vascular Regeneration for Ischemic Retinopathies: Hope from Cell Therapies

Retinal vascular diseases, such as diabetic retinopathy, retinopathy of prematurity, retinal vein occlusion, ocular ischemic syndrome and ischemic optic neuropathy, are leading causes of vision impairment and blindness. Whilst drug, laser or surgery-based treatments for the late stage complications of many of these diseases are available, interventions that target the early vasodegenerative stages are lacking. Progressive vasculopathy and ensuing ischemia is an underpinning pathology in many of these diseases, leading to hypoperfusion, hypoxia, and ultimately pathological neovascularization and/or edema in the retina and other ocular tissues, such as the optic nerve and iris. Therefore, repairing the retinal vasculature may prevent progression of ischemic retinopathies into late stage vascular complications. Various cell types have been explored for their vascular repair potential. Endothelial progenitor cells, mesenchymal stem cells and induced pluripotent stem cells are studied for their potential to integrate with the damaged retinal vasculature and limit ischemic injury. Clinical trials for some of these cell types have confirmed safety and feasibility in the treatment of ischemic diseases, including some retinopathies. Another promising avenue is mobilization of endogenous endothelial progenitors, whereby reparative cells are moved from their niche to circulating blood to target and home into ischemic tissues. Several aspects and properties of these cell types have yet to be elucidated. Nevertheless, we foresee that cell therapy, whether through delivery of exogenous or enhancement of endogenous reparative cells, will become a valuable and beneficial treatment for ischemic retinopathies.

Exosomes derived from platelet-rich plasma mediate hyperglycemia-induced retinal endothelial injury via targeting the TLR4 signaling pathway

In this study, we aimed to investigate whether exosomes derived from platelet-rich plasma (PRP-Exos) can regulate hyperglycemia-induced retinal injury via targeting the TLR4 signaling pathway. We studied the effects of PRP-Exos on retinal endothelial injury in diabetic rats and human retinal endothelial cells (HRECs) in vitro. Isolated PRP-Exos were observed by transmission electron microscopy and flow cytometry. Samples were obtained from the retinas of rats and cultured HRECs after treatment to analyze reactive oxygen species levels. Immunofluorescence and Western blotting were conducted to assess the levels of adhesion molecules and the TLR4 signaling pathway. The content of CXCL10 in PRP-Exos was analyzed by Western blot. The plasma level of PRP-Exos was greatly increased in diabetic rats. In cultured HRECs, PRP-Exos induced the production of malonyldialdehyde(MDA) and reactive oxygen species(ROS) and inhibited the activity of superoxide dismutase(SOD). Further analysis showed that the activation of the TLR4 pathway by PRP-Exos played a pivotal role in regulating inflammation. The inhibition of the TLR4 pathway by TAK-242 had a robust protective effect on PRP-Exo-induced retinal endothelial injury in vitro and vivo. In addition, PRP-Exo-derived CXCL10 led to retinal endothelial injury, and antagonizing CXCL10 with a CXCL10-neutralizing antibody dramatically attenuated such injury. In summary, PRP-Exos mediate hyperglycemia-induced retinal endothelial injury by upregulating the TLR4 signaling pathway.

Lipid-lowering medication is associated with decreased risk of diabetic retinopathy and the need for treatment in patients with type 2 diabetes: A real-world observational analysis of a health claims database

AIMS

Fenofibrate and statins reduced the need for diabetic retinopathy (DR)-related treatment in clinical trials. We aimed to determine whether use of lipid-lowering medication reduces the risk of DR and the need for treatment in patients with type 2 diabetes using a real-world health claims database.

METHODS

This was an observational analysis using a nation-wide health claims database of the Japan Medical Data Center (JMDC). Type 2 diabetes was defined according to ICD-10 codes for use of glucose-lowering medication. Use of lipid-lowering medication for at least 1 year was confirmed by the Anatomical Therapeutic Chemical Classification System. DR and diabetic macular edema (DME) were determined by ICD-10 codes. DR-related treatments were determined by health insurance claims. A propensity score for use of lipid-lowering medication was estimated, and a doubly robust estimator, using the inverse probability weighting model with regression adjustment, was obtained to determine odds ratios (OR) with 95% confidence interval (95% CI) for cumulative incidence of DR and its treatments over 3 years.

RESULTS

There were 69 070 individuals with type 2 diabetes at baseline, among whom DR developed in 5687 over a period of 3 years. Use of lipid-lowering medication was associated with decreased risk of incidence of DR (OR, 0.772; 95% CI, 0.720-0.827; P < .001). Use of lipid-lowering medication was also associated with decreased incidence of DME, any treatments for DR, laser photocoagulation and vitrectomy in patients with DR at baseline.

CONCLUSIONS

In a population of patients with type 2 diabetes with a variety of risk profiles, use of lipid-lowering medication reduced the risk of DR and thus the risks involved in treatment with laser photocoagulation and vitrectomy.

Simvastatin attenuates the aberrant expression of angiogenic factors induced by glucose variability

AIM

Over the last few years, studies have indicated that fluctuant hyperglycemia is very likely to increase the risk of cardiovascular complications of diabetes. Statins are widely used in diabetes for the prevention of cardiovascular complications, but it is still not clear whether simvastatin could also prevent glycaemic variability - induced aberrant angiogenesis which plays a significant role in the development of atherosclerosis.

METHODS

Wistar rats were divided into four groups: (1) simvastatin-treated (20 mg/kg for 8 consecutive weeks) type 2 diabetes rat model with daily glucose excursions, (2) placebo-treated type 2 diabetes rat model with daily glucose excursions, (3) placebo-treated stable well-controlled type 2 diabetes rat model and (4) placebo-treated non-diabetic rats. Daily glucose fluctuations and several angiogenic factors: cVEGF, mRNA VEGF, VEGF-R1, VEGF-R2, TGF-beta expression, circulating endothelial and progenitor endothelial cells were measured in all groups.

RESULTS

Simvastatin decreased several factors enhanced by glucose excursions: circulating VEGF, mRNA TGF-beta expression in the myocardium and mRNA VEGFR-2 expression in the aorta. Simvastatin increased some factors attenuated by glucose fluctuations: mRNA VEGF expression and mRNA VEGFR-1 expression in the myocardium and in the aorta. In the simvastatin-treated group with glycaemic variability, the percentage of circulating endothelial cells was lower and the percentage of progenitor endothelial cells in peripheral blood was higher than in the placebo-treated rats with glucose-fluctuations.

CONCLUSIONS

Simvastatin used in the rat model of type 2 diabetes with glucose variability reduces glucose variability and limits glucose fluctuations-induced changes in the expression of angiogenic factors in the cardiovascular system.

'Statins in retinal disease'

Statins are known for their blood cholesterol-lowering effect and are widely used in patients with cardiovascular and metabolic diseases. Research over the past three decades shows that statins have diverse effects on different pathophysiological pathways involved in angiogenesis, inflammation, apoptosis, and anti-oxidation, leading to new therapeutic options. Recently, statins have attracted considerable attention for their immunomodulatory effect. Since immune reactivity has been implicated in a number of retinal diseases, such as uveitis, age-related macular degeneration (AMD) and diabetic retinopathy, there is now a growing body of evidence supporting the beneficial effects of statins in these retinopathies. This review evaluates the relationship between statins and the pathophysiological basis of these diseases, focusing on their potential role in treatment. A PubMed database search and literature review was conducted. Among AMD patients, there is inconsistent evidence regarding protection against development of early AMD or delaying disease progression; though they have been found to reduce the risk of developing choroidal neovascular membranes (CNV). In patients with retinal vein occlusion, there was no evidence to support a therapeutic benefit or a protective role with statins. In patients with diabetic retinopathy, statins demonstrate a reduction in disease progression and improved resolution of diabetic macular oedema (DMO). Among patients with uveitis, statins have a protective effect by reducing the likelihood of uveitis development.

Pathogenic roles of microvesicles in diabetic retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes and has been recognized as the leading cause of blindness in adults. Several interrelated molecular pathways are involved in the development of DR. Microvesicles (MVs) are cell membrane vesicles, which carry many biologic molecules, such as mRNAs, microRNAs, transcription factors, membrane lipids, membrane receptors, and other proteins. They may be involved in intercellular communication that can promote inflammation, angiogenesis, and coagulation. Recent studies have indicated that changes in the number and composition of MVs may reflect the pathologic conditions of DR. At present, MVs are well recognized as being involved in the pathophysiological conditions of tumors and cardio-metabolic diseases. However, the roles of MVs in DR have yet to be investigated. In this review, we provide an overview of DR-induced microvascular injury that is caused by MVs derived from endothelial and circulating cells, and discuss the possible mechanisms by which MVs can lead to endothelial dysfunction, coagulation and inflammation. In addition, the protective effects of preconditioned MVs and stem cell-derived MVs are also described . Understanding the involvement of MVs in the pathophysiological conditions of DR may provide insight into the disease mechanisms and may suggest novel therapeutic strategies for DR in the future.

The ocular toxicity and pharmacokinetics of simvastatin following intravitreal injection in mice

AIM

To investigate the retinal toxicity and pharmacokinetics of simvastatin intravitreally injected into mice.

METHODS

Forty-eight 6-8-week-old C57BL/6J mice were used in this study. Simvastatin was intravitreally injected into the right eye of each mouse; the left eye was injected with vehicle and was used as a control. Bilateral dark-adapted electroretinography (ERG) was performed 1 and 7d following injection. Histology was examined using a combination of light, fluorescence and electron microscopy. High-performance liquid chromatography (HPLC) was used to determine the decay in the retinal simvastatin concentration.

RESULTS

ERG revealed no significant changes in the simvastatin-injected eyes compared to control. Histologic studies showed normal retinal morphology in eyes injected with simvastatin up to a final vitreal concentration of 200 µmol/L. No significant changes in the number of photoreceptors, bipolar cells or ganglion cells were found. The retinal simvastatin concentration decayed exponentially, with a half-life of 1.92-2.41h.

CONCLUSION

Intravitreal injection of up to 200 µmol/L simvastatin produced no signs of adverse effects in the mouse retina. Simvastatin reaches the retina shortly after intravitreal injectionand has a short half-life.

The Effect of Atorvastatin on the Viability of Ischemic Skin Flaps in Diabetic Rats

BACKGROUND

Endothelial progenitor cells play a critical role in neovascularization. However, the mobilization, recruitment, and functional capacity of endothelial progenitor cells are significantly impaired in diabetes. Statins have been shown to augment the number and improve the function of endothelial progenitor cells. This study investigated the effects of statins on the viability of ischemic skin flaps in diabetic rats.

METHODS

Twenty normal and 40 diabetic Sprague-Dawley rats were included in this study. Atorvastatin (10 mg/kg/day) was administered orally in 20 diabetic rats at 2 weeks before flap surgery for 21 consecutive days. Other rats received equal vehicle. Two weeks after first gavage, a 3 × 10-cm skin flap was established on the backs of rats. The necrotic area of each skin flap was measured at 7 days postoperatively. Capillary density and endothelial progenitor cells recruited to the flaps were analyzed using immunofluorescence staining. Circulating endothelial progenitor cell number was determined by flow cytometry. In vitro migration and tube formation experiments were used to analyze the function of endothelial progenitor cells.

RESULTS

Atorvastatin treatment increased flap survival rate and capillary density. In addition, more endothelial progenitor cells were identified in peripheral blood and skin flaps in diabetic rats receiving atorvastatin. Atorvastatin treatment also restored the impaired function of diabetic endothelial progenitor cells in migration and tube formation.

CONCLUSION

Atorvastatin notably promoted neovascularization and enhanced the viability of ischemic skin flaps in diabetic rats, which may be mediated at least partially by augmenting the number and restoring the functional capacity of endothelial progenitor cells.

Niaspan inhibits diabetic retinopathy‑induced vascular inflammation by downregulating the tumor necrosis factor‑α pathway

Diabetic retinopathy (DR) is a serious microvascular complication of diabetes and a major cause of blindness in the developing world. Early DR is characterized by vascular neuroinflammation, cell apoptosis and breakdown of the blood‑retinal barrier (BRB). However, optimal treatment options and associated mechanisms remain unclear. Niaspan, which is widely used in the prevention and treatment of hyperlipidemia‑associated diseases, has been reported to inhibit inflammation. However, the effects of Niaspan and the mechanisms underlying the anti‑inflammatory effects of Niaspan on DR have yet to be reported. The present study aimed to investigate the anti‑inflammatory effects and mechanisms of Niaspan in a rat model of DR. Rats with DR exhibited a significant increase in BRB breakdown, retinal apoptosis, and tumor necrosis factor‑α (TNF‑α) and nuclear factor‑κB (NF‑κB) expression. In addition, the expression levels of inducible nitric oxide synthase (iNOS) and intercellular cell adhesion molecule‑1 (ICAM‑1) were increased in the retinas of DR rats compared with in the normal control group. In conclusion, treatment with Niaspan significantly improved clinical and histopathological outcomes; decreased the expression levels of TNF‑α, NF‑κB, iNOS and ICAM‑1; and decreased apoptosis and BRB breakdown, as compared with in the retinas of DR rats. The present study is the first, to the best of our knowledge, to demonstrate that Niaspan treatment ameliorates DR by inhibiting inflammation, and also suggests that the TNF‑α pathway may contribute to the beneficial effects of Niaspan treatment.

Simvastatin ameliorates graft-vs-host disease by regulating angiopoietin-1 and angiopoietin-2 in a murine model

Angiopoietins play an important role in vascular endothelial function. Endothelial damage is an important pathogenesis relating with acute graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT), protecting endothelial cells (ECs) from damage may be a potent prophylaxis and therapeutic strategy of acute GVHD (aGVHD). In this study, we explored changes in Angiopoietin-1 (Ang-1) and Ang-2 expression in a aGVHD mouse model and determined whether simvastatin prevents GVHD through regulating Ang-1 and Ang-2 expression. In vitro simvastatin administration increased Ang-1 production and release but conversely inhibited Ang-2 release from EA.hy926 ECs. Simvastatin improved the survival of aGVHD mice, attenuated the histopathological GVHD grades and plasma levels of Ang-2, and elevated the plasma levels of Ang-1 as well as the aortic endothelial levels of Ang-1 and Ang-2. In summary, simvastatin represents a novel approach to combat GVHD by increasing Ang-1 production while suppressing Ang-2 release to stabilize endothelial cells.

Tumor Necrosis Factor α Regulates Endothelial Progenitor Cell Migration via CADM1 and NF-kB

Shortly after the discovery of endothelial progenitor cells (EPCs) in 1997, many clinical trials were conducted using EPCs as a cellular based therapy with the goal of restoring damaged organ function by inducing growth of new blood vessels (angiogenesis). Results were disappointing, largely because the cellular and molecular mechanisms of EPC-induced angiogenesis were not clearly understood. Following injection, EPCs must migrate to the target tissue and engraft prior to induction of angiogenesis. In this study EPC migration was investigated in response to tumor necrosis factor α (TNFα), a pro-inflammatory cytokine, to test the hypothesis that organ damage observed in ischemic diseases induces an inflammatory signal that is important for EPC homing. In this study, EPC migration and incorporation were modeled in vitro using a coculture assay where TNFα treated EPCs were tracked while migrating toward vessel-like structures. It was found that TNFα treatment of EPCs increased migration and incorporation into vessel-like structures. Using a combination of genomic and proteomic approaches, NF-kB mediated upregulation of CADM1 was identified as a mechanism of TNFα induced migration. Inhibition of NF-kB or CADM1 significantly decreased migration of EPCs in vitro suggesting a role for TNFα signaling in EPC homing during tissue repair. Stem Cells 2016;34:1922-1933.

Use of Statins to Augment Progenitor Cell Function in Preclinical and Clinical Studies of Regenerative Therapy: a Systematic Review

BACKGROUND

Mesenchymal stromal cells (MSCs) and endothelial progenitor cells (EPCs) are used in cell-based regenerative therapy. HMG CoA reductase inhibitors (statins) appear promising in blocking apoptosis, prolonging progenitor cell survival and improving their capacity to repair organ function.

METHODS

We performed a systematic review of preclinical and clinical studies to clarify whether statins can improve cell-based repair of organ injury. MEDLINE, EMBASE, and PUBMED databases were searched (1947 to June 25, 2013). Controlled clinical and pre-clinical studies were included that evaluated statin therapy used alone or in combination with MSCs or EPCs in patients or animals with organ injury.

RESULTS

After screening 771 citations, 100 records underwent full eligibility screening of which 38 studies met eligibility and were included in the review: Studies were grouped into pre-clinical studies that involved statin treatment in combination with cell therapy (18 studies), preclinical studies of statin therapy alone (13 studies) and clinical studies of statin therapy (7 studies). Studies addressed cardiac injury (14 studies), vascular disorders (15 studies), neurologic conditions (8 studies) and bone fractures (1 study). Pre-clinical studies of statins in combination with MSC infusion (15 studies) or EPC therapy (3 studies) were described and despite marked heterogeneity in reporting outcomes of cellular analysis and organ function, all of these cell-based pre-clinical studies reported improved organ recovery with the addition of statin therapy. Moreover, 13 pre-clinical studies involved the administration of a statin drug alone to animals. An increase in EPC number and/or function (no studies of MSCs) was reported in 11 of these studies (85 %) and improved organ function in 12 studies (92 %). We also identified 7 clinical studies and none involved the administration of cells but described an increased number and/or function of EPCs (no studies of MSCs) and improved organ function with statin therapy (1.2-fold to 35-fold improvement over controls) in all 7 studies.

CONCLUSION

Our systematic review provides a foundation of encouraging results that support further study of statins in regenerative therapy to augment the number and/or function of MSCs used in cell-based repair and to augment the number and function of EPCs in vivo to repair damaged tissues. Larger studies are needed to ensure safety and confirm clinical benefits.

Improved outcome after primary vitrectomy in diabetic patients treated with statins

PURPOSE

To evaluate the effect of preoperative statin treatment on the outcome of primary vitrectomy in type 1 and 2 diabetic patients.

METHODS

In this open, observational institutional study, a total of 192 eyes of 171 type 1 and 2 adult diabetic patients admitted for primary vitrectomy for management of sight-threatening forms of diabetic retinopathy were divided according to the use of lipid-lowering therapy: those with statin treatment (79 eyes of 73 patients) and those taking no statin medication (113 eyes of 98 patients). One-month best-corrected visual acuity (BCVA) gain and cumulative 12-month revitrectomy frequency were analyzed.

RESULTS

In multivariate linear regression, diabetic patients with statin treatment had a better 1-month BCVA improvement than did those without statin treatment (absolute difference 0.26, 95% confidence interval [CI] 0.02-0.50, p = 0.028). Subgroup analysis revealed that diabetic patients on statin had better postoperative BCVA improvement when preoperative status included partial or panretinal laser photocoagulation (p = 0.042 and p = 0.049) and anti-vascular endothelial growth factor therapy (p = 0.011). Moreover, diabetic patients with preoperative macular edema (p = 0.009), vitreous hemorrhage (p&lt;0.001), proliferative retinopathy (p&lt;0.001), or tractional retinal detachment (p = 0.010) had better BCVA recovery if receiving statin. In Cox proportional hazards regression model, revitrectomies in our 12-month follow-up were less frequent in diabetic patients on statin treatment (hazard ratio 0.28, 95% CI 0.08-0.93, p = 0.037).

CONCLUSIONS

These data provide novel insight into the potential clinical benefit for patients with sight-threatening diabetic retinopathy undergoing vitrectomy treated with statin.

Simvastatin restored vascular reactivity, endothelial function and reduced string vessel pathology in a mouse model of cerebrovascular disease

Cerebrovascular dysfunction seen in Alzheimer's disease (AD) and vascular dementia (VaD) is multifaceted and not limited to the amyloid-β (Aβ) pathology. It encompasses structural alterations in the vessel wall, degenerating capillaries (string vessels), vascular fibrosis and calcification, features recapitulated in transgenic mice that overexpress transforming growth factor-β1 (TGF mice). We recently found that simvastatin rescued Aβ-mediated cerebrovascular and cognitive deficits in a transgenic mouse model of AD. However, whether simvastatin can counteract Aβ-independent deficits remains unknown. Here, we evaluated the effects of simvastatin in aged TGF mice on cerebrovascular reactivity and structure, and on cognitive performance. Simvastatin restored baseline levels of nitric oxide (NO), NO-, and KATP channel-mediated dilations and endothelin-1-induced contractions. Simvastatin significantly reduced vasculopathy with arteriogenic remodeling and string vessel pathology in TGF mice. In contrast, simvastatin did not lessen gliosis, and the cerebrovascular levels of pro-fibrotic proteins and calcification markers remained elevated after treatment. The TGF mice displayed subtle cognitive decline that was not affected by simvastatin. Our results show potent benefits of simvastatin on endothelial- and smooth muscle cell-mediated vasomotor responses, endothelial NO synthesis and in preserving capillary integrity. We conclude that simvastatin could be indicated in the treatment of cerebrovascular dysfunction associated with VaD and AD.

Low intravitreal angiopoietin-2 and VEGF levels in vitrectomized diabetic patients with simvastatin treatment

PURPOSE

To investigate the intravitreal levels of potent vasoactive, angiogenic and extracellular matrix remodelling factors in the diabetic patients with simvastatin treatment.

METHODS

This is an institutional, prospective, observational case-control study. Type-1 and type-2 diabetic patients on lipophilic simvastatin (N = 14) compared with patients without statin medication (N = 50). Vitreous samples were subjected to protein measurements of angiopoietin (Ang)-1 and Ang-2, erythropoietin (EPO), transforming growth factor (TGF)-β1, vascular endothelial growth factor (VEGF) by ELISA and matrix metalloproteinase (MMP)-2 and MMP-9 by gelatin zymography.

RESULTS

Intravitreal levels of Ang-2 (p = 0.029), VEGF (p = 0.001) and proMMP-9 (p = 0.015) were lower in simvastatin-treated than in non-statin-treated controls. In diabetics with macular oedema (DME), intravitreal Ang-2 (p = 0.006) and VEGF (p = 0.002) levels were lower in simvastatin-treated patients compared with non-statin-treated controls. In those patients with proliferative diabetic retinopathy (PDR), intravitreal Ang-2 (p = 0.002), TGF-β1 (p = 0.037), VEGF (p = 0.001) and pro- and totalMMP-9 (p = 0.004 and p = 0.007) levels were lower when receiving simvastatin medication.

CONCLUSIONS

In diabetic patients with DME or PDR, the intravitreal levels of permeability and proangiogenic factors Ang-2 and VEGF were lower in simvastatin-treated than in those without statin medication. Moreover, the levels of MMP-9 and TGF-β1, factors involved in the breakdown of basement membrane and fibroproliferation, were lower in patients with PDR having simvastatin medication. When acetylsalicylic acid was combined with simvastatin treatment, the intraocular levels of Ang-2 and VEGF were significantly lower than in diabetics treated with simvastatin alone. These data provide a novel insight into the potential protective mechanisms underlying simvastatin medication in patients with diabetic retinopathy complications.

Stem cell therapies in the management of diabetic retinopathy

Diabetic retinopathy is the leading cause of blindness in the working population. We now understand that the pathogenesis of the disease contains both a neurodegenerative and vasodegenerative component. Yet despite this, current treatment is still limited to combating the proliferative end stage component of the disease rather than addressing its underlying causes. In recent years, much basic research has focused on demonstrating the potential that several classes of stem cells have in conferring both neuro- and vasoprotection on the diabetic retina. Further, progress has been made in using stem cells to stimulate both neuro and vascular regeneration. This review will discuss the current understanding as to what mechanisms underlie diabetic retinopathy while highlighting the types of stem cells which offer hope as potential novel therapies for diabetic retinopathy, including those that are now in clinical trial.

Specific role of impaired glucose metabolism and diabetes mellitus in endothelial progenitor cell characteristics and function

The disease burden of diabetes mellitus (DM) and its associated cardiovascular complications represent a growing and major global health problem. Recent studies suggest that circulating exogenous endothelial progenitor cells (EPCs) play an important role in endothelial repair and neovascularization at sites of injury or ischemia. Both experimental and clinical studies have demonstrated that hyperglycemia related to DM can induce alterations to EPCs. The reduction and dysfunction of EPCs related to DM correlate with the occurrence and severity of microvascular and macrovascular complications, suggesting a close mechanistic link between EPC dysfunction and impaired vascular function/repair in DM. These alterations to EPCs, likely mediated by multiple pathophysiological mechanisms, including inflammation, oxidative stress, and alterations in Akt and the nitric oxide pathway, affect EPCs at multiple stages: differentiation and mobilization in the bone marrow, trafficking and survival in the circulation, and homing and neovascularization. Several different therapeutic approaches have consequently been proposed to reverse the reduction and dysfunction of EPCs in DM and may represent a novel therapeutic approach to prevent and treat DM-related cardiovascular complications.