Platelet microvesicles promote the recovery of neurological function in mouse model of cerebral infarction by inducing angiogenesis

Nanomaterial-Based Drug Delivery Systems for Ischemic Stroke

Ischemic stroke is a leading cause of death and disability in the world. At present, reperfusion therapy and neuroprotective therapy, as guidelines for identifying effective and adjuvant treatment methods, are limited by treatment time windows, drug bioavailability, and side effects. Nanomaterial-based drug delivery systems have the characteristics of extending half-life, increasing bioavailability, targeting drug delivery, controllable drug release, and low toxicity, thus being used in the treatment of ischemic stroke to increase the therapeutic effects of drugs. Therefore, this review provides a comprehensive overview of nanomaterial-based drug delivery systems from nanocarriers, targeting ligands and stimulus factors of drug release, aiming to find the best combination of nanomaterial-based drug delivery systems for ischemic stroke. Finally, future research areas on nanomaterial-based drug delivery systems in ischemic stroke and the implications of the current knowledge for the development of novel treatment for ischemic stroke were identified.

Platelets and (Lymph)angiogenesis

The formation of new blood and lymphatic vessels is essential for both the development of multicellular organisms and (patho)physiological processes like wound repair and tumor growth. In the 1990s, circulating blood platelets were first postulated to regulate tumor angiogenesis by interacting with the endothelium and releasing angiogenic regulators from specialized α granules. Since then, many studies have validated the contributions of platelets to tumor angiogenesis, while uncovering novel roles for platelets in other angiogenic processes like wound resolution and retinal vascular disease. Although the majority of (lymph)angiogenesis occurs during development, platelets appear necessary for lymphatic but not vascular growth, implying their particular importance in pathological cases of adult angiogenesis. Future work is required to determine whether drugs targeting platelet production or function offer a clinically relevant tool to limit detrimental angiogenesis.

Neuronal injuries in cerebral infarction and ischemic stroke: From mechanisms to treatment (Review)

Stroke is the leading cause of disabilities and cognitive deficits, accounting for 5.2% of all mortalities worldwide. Transient or permanent occlusion of cerebral vessels leads to ischemic strokes, which constitutes the majority of strokes. Ischemic strokes induce brain infarcts, along with cerebral tissue death and focal neuronal damage. The infarct size and neurological severity after ischemic stroke episodes depends on the time period since occurrence, the severity of ischemia, systemic blood pressure, vein systems and location of infarcts, amongst others. Ischemic stroke is a complex disease, and neuronal injuries after ischemic strokes have been the focus of current studies. The present review will provide a basic pathological background of ischemic stroke and cerebral infarcts. Moreover, the major mechanisms underlying ischemic stroke and neuronal injuries are summarized. This review will also briefly summarize some representative clinical trials and up-to-date treatments that have been applied to stroke and brain infarcts.

Hypoxia-inducible Factor 2α Exerts Neuroprotective Effects by Promoting Angiogenesis via the VEGF/Notch Pathway after Intracerebral Hemorrhage Injury in Rats

Angiogenesis after intracerebral hemorrhage (ICH) injury can effectively alleviate brain damage and improve neurological function. Hypoxia-inducible factor 2α (HIF-2α) is an important angiogenic regulator and exhibits protective effects in several neurological diseases; however, its role in ICH has not yet been reported. Hence, in the present study, we explored whether HIF-2α reduces ICH injury by promoting angiogenesis. In addition, we explored the role of the vascular endothelial growth factor (VEGF)/Notch pathway in HIF-2α-mediated angiogenesis. We injected 50 μL of autologous blood taken from the femoral artery into the right striatum of healthy male adult Sprague-Dawley rats to create an autologous-blood-induced rat model of ICH. Lentiviral vectors were injected to both overexpress and knock down HIF-2α expression. VEGF receptor 2 (VEGFR2) and Notch-specific inhibitors were injected intraperitoneally to block VEGFR2- and Notch-mediated signaling after lentiviral injections. Our data showed that HIF-2α overexpression reduced neurological-damage scores and brain-water content, suggesting it had a protective effect on ICH injury. In addition, overexpression of HIF-2α promoted angiogenesis, increased focal cerebral blood flow (CBF), and reduced neuronal damage, whereas HIF-2α knockdown resulted in the opposite effects. Furthermore, we found that HIF-2α-mediated angiogenesis was blocked by a Notch-specific inhibitor. Likewise, the HIF-2α-mediated increase in phospho-VEGFR-2, cleaved-Notch1 and Notch1 expression was reversed via a VEGFR2-specific inhibitor. Taken together, our results indicate that HIF-2α promotes angiogenesis via the VEGF/Notch pathway to attenuate ICH injury. Moreover, our findings may contribute to the development of a novel strategy for alleviating ICH injury via HIF-2α-mediated upregulation of angiogenesis.

Tissue plasminogen activator disrupts the blood-brain barrier through increasing the inflammatory response mediated by pericytes after cerebral ischemia

Pericytes, important elements of the blood-brain barrier (BBB), play critical roles in maintaining BBB integrity and modulating hemostasis, angiogenesis, inflammation and phagocytic function. We investigated whether pericytes are involved in the recombinant tissue plasminogen activator (rt-PA)-induced inflammatory response, which disrupts the BBB, and investigated the potential mechanisms. Middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation (OGD) were employed to mimic hypoxic-ischemic conditions. Rt-PA was intravenously injected into mice 1 h after 1 h MCAO, and Rt-PA was added to the culture medium after 4 h OGD. Rt-PA treatment aggravated the disruption of the BBB compared with hypoxia treatment, and etanercept (TNF-α inhibitor) combined with rt-PA alleviated the rt-PA-induced BBB disruption in vivo and in vitro. Rt-PA treatment increased the TNF-α and MCP-1 levels and decreased the TGF-β, p-Smad2/3 and PDGFR-β levels compared with hypoxia treatment in vivo and vitro. TGF-β combined with rt-PA decreased TNF-α and MCP-1 secretion and alleviated BBB disruption compared with rt-PA; these changes were abrogated by TPO427736 HCL (a TGF-β/p-Smad2/3 pathway inhibitor) cotreatment in vitro. Rt-PA did not decrease TGF-β and p-Smad2/3 expression in PDGFR-β-overexpressing pericytes after OGD. These findings identify PDGFR-β/TGF-β/p-Smad2/3 signaling in pericytes as a new therapeutic target for the treatment of rt-PA-induced BBB damage.

A Potential Role for the Existence of Pericytes in the Neurovascular Unit of the Sexually Dimorphic Nucleus of the Rat Preoptic Area to Control Blood-Brain Barrier Function

BACKGROUND

The present study aimed at determining pericytes, a missing component in the previously proposed living neurovascular unit (NVU) of the sexually dimorphic nucleus of the preoptic area (SDN-POA) in rats.

MATERIALS AND METHODS

Calbindin D28K-immunoreactivities (CB28-irs) were used to delineate the SDN-POA in which CD13-immunoreactivities (CD13-irs) or alpha-smooth muscle actinimmunoreactivities (αSMA-irs), two pericyte biomarkers serving the indexes of pericytes, were tagged using two adjacent brain sections (90-micron intervals). In addition, the nestinimmunoreactive (nestin-ir) cells in the SDN-POA were counted as pericytes referring to additional standards: location and nucleic and cellular morphology. Male SDN-POA volume (5.0±0.3x10-3 mm3) was significantly larger than the female (1.7±0.3x10-3 mm3). Within the SDN-POA, the CD13-irs were characterized as dots, densely packed and net-like in distribution, while the αSMAirs, excluding pipe-like or circular structures, appeared as short rod-like structures that were sparsely distributed.

RESULTS

The immunoreactive counts of alpha-smooth muscle actin were 353±57/mm2 in males and 124±46/mm2 in females (p<0.05). On the other hand, densities of the dot-like CD13-irs were similar between males (4009±301/mm2) and females (4018±414/ mm2). There was no difference between the male and the female in the nestin-ir pericyte count in the SDN-POA.

CONCLUSION

In conclusion, the present study adds new information concerning pericytes to the living NVU of the SDN-POA. There is a difference of sex in the count of the αSMA-irs in the living NVU of the SDN-POA. However, why such a difference exists warrants further investigations.