Spatially localized recruitment of anti-inflammatory monocytes by SDF-1α-releasing hydrogels enhances microvascular network remodeling.

Tissue repair processes are characterized by the biphasic recruitment of distinct subpopulations of blood monocytes, including classical ("inflammatory") monocytes (IMs, Ly6C(hi)Gr1(+)CX3CR1(lo)) and non-classical anti-inflammatory monocytes (AMs, Ly6C(lo)Gr1(-)CX3CR1(hi)). Drug-eluting biomaterial implants can be used to tune the endogenous repair process by the preferential recruitment of pro-regenerative cells. To enhance recruitment of AMs during inflammatory injury, a novel N-desulfated heparin-containing poly(ethylene glycol) diacrylate (PEG-DA) hydrogel was engineered to deliver exogenous stromal derived factor-1α (SDF-1α), utilizing the natural capacity of heparin to sequester and release growth factors. SDF-1α released from the hydrogels maintained its bioactivity and stimulated chemotaxis of bone marrow cells in vitro. Intravital microscopy and flow cytometry demonstrated that SDF-1α hydrogels implanted in a murine dorsal skinfold window chamber promoted spatially-localized recruitment of AMs relative to unloaded internal control hydrogels. SDF-1α delivery stimulated arteriolar remodeling that was correlated with AM enrichment in the injury niche. SDF-1α, but not unloaded control hydrogels, supported sustained arteriogenesis and microvascular network growth through 7 days. The recruitment of AMs correlated with parameters of vascular remodeling suggesting that tuning the innate immune response by biomaterial SDF-1α release is a promising strategy for promoting vascular remodeling in a spatially controlled manner.

Citalopram enhances neurovascular regeneration and sensorimotor functional recovery after ischemic stroke in mice.

Recent clinical trials have demonstrated that treatment with selective serotonin reuptake inhibitors after stroke enhances motor functional recovery; however, the underlying mechanisms remain to be further elucidated. We hypothesized that daily administration of the clinical drug citalopram would produce these functional benefits via enhancing neurovascular repair in the ischemic peri-infarct region. To test this hypothesis, focal ischemic stroke was induced in male C57/B6 mice by permanent ligation of distal branches of the middle cerebral artery to the barrel cortex and 7-min occlusion of the bilateral common carotid arteries. Citalopram (10mg/kg, i.p.) was injected 24h after stroke and daily thereafter. To label proliferating cells, bromo-deoxyuridine was injected daily beginning 3 days after stroke. Immunohistochemical and functional assays were performed to elucidate citalopram-mediated cellular and sensorimotor changes after stroke. Citalopram treatment had no significant effect on infarct formation or edema 3 days after stroke; however, citalopram-treated mice had better functional recovery than saline-treated controls 3 and 14 days after stroke in the adhesive removal test. Increased expression of brain-derived neurotrophic factor was detected in the peri-infarct region 7 days after stroke in citalopram-treated animals. The number of proliferating neural progenitor cells and the distance of neuroblast migration from the sub-ventricular zone toward the ischemic cortex were significantly greater in citalopram-treated mice at 7 days after stroke. Immunohistochemical staining and co-localization analysis showed that citalopram-treated animals generated more new neurons and microvessels in the peri-infarct region 21 and 28 days after stroke. Taken together, these results suggest that citalopram promotes post-stroke sensorimotor recovery likely via enhancing neurogenesis, neural cell migration and the microvessel support in the peri-infarct region of the ischemic brain.

Erythropoietin attenuates intracerebral hemorrhage by diminishing matrix metalloproteinases and maintaining blood-brain barrier integrity in mice.

The protective mechanism of recombinant human erythropoietin (rhEPO) on blood-brain barrier (BBB) after brain injury is associated with the attenuation of neuro-inflammation. We hypothesize that rhEPO treatment after intracerebral hemorrhage (ICH) modulates matrix metalloproteinase (MMP) activity, maintains BBB integrity, and reduces BBB breakdown-associated inflammation. Adult male 129S2/sv mice were subjected to autologous whole blood-induced ICH. rhEPO or saline was administered intraperitoneally immediately after surgery and for 3 more days until day of sacrifice. BBB permeability was measured by Evans blue leakage, and edema was assessed by brain water content. Immunofluorescence and Western blotting were performed to detect expression of tight junction marker occludin, type IV collagen, MMPs, tissue inhibitor of metalloproteinase (TIMP), and glial fibrillary acidic protein, rhEPO prevented Evans blue leakage, reduced brain edema, and preserved expression of occludin and collagen IV. rhEPO treatment decreased MMP-2 expression, increased TIMP-2 expression, and reduced the number of reactive astrocytes in the brain compared to saline control. We conclude that rhEPO reduces MMP activity, BBB disruption, and the glial cell inflammatory reaction 3 days after ICH. Our study provides additional evidence for the mechanism of rhEPO's neurovascular protective effects and a potential clinical application in the treatment of ICH.

Preeclampsia.

The case of a 32-year-old primigravida, 32 weeks gestation, with nausea, vomiting, thrombocytopenia, and abnormal liver function tests is presented. A diagnosis of severe preeclampsia was made and the patient underwent emergency cesarean section. Improvement of clinical symptoms and laboratory studies followed over the succeeding days. These less common manifestations of preeclampsia indicate severe disease necessitating aggressive management, even in the setting of a normal blood pressure. Thrombocytopenia, microangiopathic hemolytic anemia, or abnormal liver functions in a patient presenting in the latter half of pregnancy may be manifestations of severe preeclampsia.