Real-time in vivo imaging reveals specific nanoparticle target binding in a syngeneic glioma mouse model

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Nanomaterial-based drug delivery is a promising strategy for glioma treatment. However, the detailed dynamics of nanoparticles in solid glioma are still a mystery, including their intratumoral infiltration depth, penetration, retention time, and distribution.
Revealing these processes in detail requires repeated intravital imaging of the corresponding brain tumor regions over time during glioma growth.
Hereby, we established a syngeneic orthotopic cerebral glioma mouse model by combining the chronic cranial window and two-photon microscopy.
Thus, we were able to investigate the dynamics of the nanoparticles during long-term glioma growth.
Three hours after the intravenous (i.v.) injection of integrin αVβ3 binding conjugated silicon nanoparticles (SNPs-PEG-RGD-FITC), green nanoparticles had already infiltrated the brain glioma, and then more nanoparticles penetrated into the solid brain tumor and were retained for at least 8 days.
However, the amount of control SNPs-PEG-FITC that infiltrated into the solid brain tumor was very low.
Moreover, we found that SNPs-PEG-RGD-FITC were not only located in the tumor border but could also infiltrate into the core region of the solid tumor.
 In vitro assay also confirmed the high binding affinity between GL-261-Tdtomato cells and SNPs-PEG-RGD-FITC.
Our results indicate that SNPs-PEG-RGD-FITC has high penetration and retention in a solid glioma and our model provides novel ideas for the investigation of nanoparticle dynamics in brain tumors.

Role of Skin Stretch on Local Vascular Permeability in Murine and Cell Culture Models

Excessive mechanical forces, particularly skin stretch, have been implicated in pathological cutaneous scarring.
We hypothesize that this reflects, in part, stretch-induced vessel leakage that provokes prolonged wound/scar inflammation. However, this has never been observed directly.
Here, a mouse model was used to examine the effect of skin flap stretching on vascular permeability.
An in vitro model with pseudocapillaries grown in a stretchable chamber was also used to determine the effect of stretching on endothelial cell morphology and ion channel activity.
Methods: Murine skin flaps were stretched with a biaxial stretching device, after which FITC–conjugated-dextran was injected and imaged with fluorescence stereomicroscopy.
Endothelial cells were induced to form pseudocapillary networks in an elastic chamber. The chamber was stretched and differential interference contrast microscopy was used to assess cell morphology.
In other experiments, markers for Ca2+ influx and K+ efflux were added before a single stretch was conducted.
Histamine served as a positive-control in all experiments.
Results: Cyclic stretching (20%) increased the vascular permeability of skin flaps almost as strongly as histamine.
Both stimuli also partially disrupted the pseudocapillary networks, induced cell contraction, and created gaps between the cells.
Both stimuli caused sustained K+ efflux; stretching had a milder effect on Ca2+ influx.
Conclusions: Excessive cyclical stretching strongly increased the vascular permeability of skin vessels and in vitro pseudocapillaries.
This effect associated with increased K+ efflux and some Ca2+ influx. Inhibiting such early stretch-induced signaling events may be an effective strategy for treating and preventing hypertrophic scars and keloids.

AGEs/RAGE Promote Osteogenic Differentiation in Rat Bone Marrow-Derived Endothelial Progenitor Cells via MAPK Signaling

Systemic vascular impairment is the most common complication of diabetes. Advanced glycation end products (AGEs) can exacerbate diabetes-related vascular damage by affecting the intima and media through a variety of mechanisms.
In the study, we demonstrated that AGEs and their membrane receptor RAGE could induce the differentiation of EPCs into osteoblasts under certain circumstances, thereby promoting accelerated atherosclerosis.
Differentiation into osteoblasts was confirmed by positive staining for DiI-acetylated fluorescently labeled low-density lipoprotein and FITC–conjugated Ulex europaeus agglutinin.
During differentiation, expression of receptor for AGE (RAGE) was significantly upregulated.
This upregulation was attenuated by transfection with RAGE-targeting small interfering (si)RNA. siRNA-mediated knockdown of RAGE expression significantly inhibited the upregulation of AGE-induced calcification-related proteins, such as runt-related transcription factor 2 (RUNX2) and osteoprotegerin (OPG).
Additional experiments showed that AGE induction of EPCs significantly induced ERK, p38MAPK, and JNK activation.
The AGE-induced upregulation of osteoblast proteins (RUNX2 and OPG) was suppressed by treatment with a p38MAPK inhibitor (SB203580) or JNK inhibitor (SP600125), but not by treatment with an ERK inhibitor (PD98059), which indicated that AGE-induced osteoblast differentiation from EPCs may be mediated by p38MAPK and JNK signaling, but not by ERK signaling.
These data suggested that AGEs may bind to RAGE on the EPC membrane to trigger differentiation into osteoblasts.
The underlying mechanism appears to involve the p38MAPK and JNK1/2 pathways, but not the ERK1/2 pathway.

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