Barrier mechanisms in the developing brain

Bilirubin isomer distribution in jaundiced neonates during phototherapy with LED light centered at 497 nm (turquoise) vs. 459 nm (blue)

BACKGROUND

Phototherapy using blue light is the treatment of choice worldwide for neonatal hyperbilirubinemia. However, treatment with turquoise light may be a desirable alternative. Therefore, the aim of this randomized, controlled study was to compare the bilirubin isomer distribution in serum of jaundiced neonates after 24 h of therapy with narrow-band (LED) light centered at 497 nm (turquoise) vs. 459 nm (blue), of essentially equal irradiance.

MATERIALS

Eighty-three neonates (≥33 wk gestational age) with uncomplicated hyperbilirubinemia were included in the study. Forty neonates were exposed to light centered at 497 nm and 43 infants with light centered at 459 nm. Irradiances were 5.2 × 10(15) and 5.1 × 10(15) photons/cm(2)/s, respectively.

RESULTS

After 24 h of treatment no significant differences in serum concentrations of total bilirubin isomers and Z,Z-bilirubin were observed between the 2 groups. Interestingly, concentrations of Z,E-bilirubin, and thus also total bilirubin isomers formed during therapy, were highest for infants receiving light centered at 459 nm, while the concentration of E,Z-bilirubin was highest for those receiving light centered at 497 nm. No significant difference was found between concentrations of E,Z-lumirubin.

CONCLUSION

Therapy with LED light centered at 497 nm vs. 459 nm, applied with equal irradiance on the infants, resulted in a different distribution of bilirubin isomers in serum.

Active diffusion of nanoparticles of maternal origin within the embryonic brain

Aim: To investigate porous silicon (PSi) nanoparticles (NPs) behavior in the embryonic brain. Materials & methods: Fluorescently labeled PSi NPs were injected into the embryonic brains intraventricularly and to the mother intravenously (iv.). Brain histology from different time points up to 3 days was analyzed and live brains imaged with two-photon microscopy. Results: PSi NPs were able to penetrate 80% of the embryonic cortical depth. Particle motility was confirmed in real-time in vivo. PSi NPs were able to penetrate the embryonic cortex after either iv. maternal or intraventricular injection. No developmental of macromorphological changes or increased cell apoptosis was observed. Conclusion: PSi NPs penetrate deep in the brain tissues of embryos after intraventricular injection and after iv. injection to the mother.

Blood-brain barrier disruption during spontaneous canine visceral leishmaniasis

Visceral leishmaniasis is a complex disease caused by Leishmania infantum, and in dogs, besides the classical symptoms, there are descriptions of inflammatory alterations in the brain. Brain inflammation is a strictly controlled process, and as the brain counts on the efficiency of the blood-brain barrier (BBB), we aimed to assess BBB integrity in dogs with spontaneous visceral leishmaniasis. Therefore, we evaluated markers in the cerebrospinal fluid (CSF) and in brain tissue related to BBB disruption and brain inflammation. Elevated albumin quota revealed BBB breakdown, corroborated by increased concentrations of anti-Leishmania antibodies in the CSF. In the brain, albumin and IgG staining formed halos around blood vessels, a classical indicator of BBB leakage. Soluble IgG was also detected in the choroid plexus and ependyma, and in these structures, IgG stained random resident cells. IgG(+) cells and Fcγ-RI(+) cells were identified in the choroid plexus, ependyma and perivascular in the brain parenchyma. The data support the occurrence of BBB disruption in dogs with spontaneous visceral leishmaniasis, and IgG as a key molecule that is capable of initiating and/or maintaining the inflammatory stimuli in the nervous milieu and the CSF as an important disseminator of inflammatory stimuli within the CNS.

Maternal antibodies and developing blood-brain barrier

We briefly review the protective role of maternal antibodies during fetal development and at early postnatal stages. We describe antibody delivery to fetuses, particularly in the context of the developing blood-brain barrier (BBB), and present the essential concepts regarding the adult BBB, together with existing information on the prenatal developing BBB. We focus on maternal antibody transfer to the developing brain and the consequences of the presence of pathogenic antibodies at early stages of brain development on subsequent brain dysfunction.

Vitamin A Supplementation Increases the Uptake of Chylomicron Retinyl Esters into the Brain of Neonatal Rats Raised under Vitamin A-Marginal Conditions

BACKGROUND

The most rapid phase of brain development occurs during the neonatal period. Vitamin A (VA; retinol) is critical for many aspects of this process, including neurogenesis, synaptic plasticity, learning, and memory formation. However, the metabolism of retinol in the neonatal brain has not been extensively explored.

OBJECTIVE

We examined the uptake of VA into the brain in neonatal rats raised under VA-marginal conditions (control group) and assessed the effect of VA supplementation on the uptake of VA into the brain.

METHODS

Sprague-Dawley neonatal rats (n = 104) nursed by mothers fed a VA-marginal diet were randomly assigned and treated on postnatal day 4 with an oral dose of either VA (6 μg retinyl palmitate/g body weight) or canola oil as the control, both of which contained 1.8 μCi [(3)H]retinol. Pups (n = 4/group at a time) were killed at 13 sampling times from 30 min to 24 d after dosing. The uptake of total retinol, chylomicron-associated retinyl esters (REs), and retinol bound to retinol-binding protein (RBP) was estimated with the use of WinSAAM version 3.0.8.

RESULTS

Total retinol mass in the brain was closely dependent on its mass in plasma over time (r = 0.91; P < 0.001). The uptake of retinol into the brain involved both postprandial chylomicrons and RBP, with RBP delivering most of the retinol in the control group [0.27 nmol/d (RBP) compared with 0.01 nmol/d (chylomicrons)]. VA supplementation increased the fractional uptake of chylomicron REs from 0.3% to 1.2% of plasma pool/d, decreased that of RBP retinol from 0.5% to 0.2% of plasma pool/d, and increased the transfer rate of chylomicron REs from nearly zero to 0.7 nmol/d, causing a day-long elevation in the brain mass of total retinol.

CONCLUSION

Postprandial chylomicrons may be a primary mechanism for delivering a recently ingested large dose of VA to the brain of neonatal rats raised under VA-marginal conditions.

Neuroteratogenic Viruses and Lessons for Zika Virus Models

The Centers for Disease Control and Prevention has confirmed that Zika virus (ZIKV) causes congenital microcephaly. ZIKV now joins five other neuroteratogenic (NT) viruses in humans and ZIKV research is in its infancy. In addition, there is only one other NT human arbovirus (Venezuelan equine encephalitis virus), which is also poorly understood. But further insight into ZIKV can be found by evaluating arboviruses in domestic animals, of which there are at least seven NT viruses, three of which have been well studied. Here we review two key anatomical structures involved in modeling transplacental NT virus transmission: the placenta and the fetal blood-brain barrier. We then survey major research findings regarding transmission of NT viruses for guidance in establishing a mouse model of Zika disease that is crucial for a better understanding of ZIKV transmission and pathogenesis.

Finding effective biomarkers for pediatric traumatic brain injury

As traumatic brain injury (TBI) continues to affect children and young adults worldwide, research on reliable biomarkers grows as a possible aid in determining the severity of injury. However, many studies have revealed that diverse biomarkers such as S100B and myelin basic protein (MBP) have many limitations, such as their elevated normative concentrations in young children. Therefore, the results of these studies have yet to be translated to clinical applications. However, despite the setbacks of research into S100B and MBP, investigators continue to research viable biomarkers, notably glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase L1 (UCH-L1), as possible aids in medical decision making. Studies have revealed that GFAP and UCH-L1 actually are better predictors of injury progression than the before-mentioned biomarkers S100B and MBP. In addition, UCH-L1 has demonstrated an ability to detect injury while CT is negative, suggesting an ability to detect acute intracranial lesions. Here, we evaluate research testing levels of GFAP and UCH-L1 on children diagnosed with TBI and compare our results to those of other tested biomarkers. In a recent study done by Hayes et al., GFAP and UCH-L1 demonstrated the potential to recognize children with the possibility of poor outcome, allowing for more specialized treatments with clinical and laboratory applications. Although studies on GFAP and UCH-L1 have for the most part warranted positive results, further studies will be needed to confirm their role as reliable markers for pediatric TBI.

Serum Concentrations of Ubiquitin C-Terminal Hydrolase-L1 and Glial Fibrillary Acidic Protein after Pediatric Traumatic Brain Injury

Objective reliable markers to assess traumatic brain injury (TBI) and predict outcome soon after injury are a highly needed tool for optimizing management of pediatric TBI. We assessed serum concentrations of Glial Fibrillary Acidic Protein (GFAP) and Ubiquitin C-Terminal Hydrolase-L1 (UCH-L1) in a cohort of 45 children with clinical diagnosis of TBI (Glasgow Coma Scale [GCS] 3–15) and 40 healthy subjects, evaluated their associations with clinical characteristics and outcomes, and compared their performance to previously published data on two well-studied blood biomarkers, S100B and MBP. We observed higher serum levels of GFAP and UCH-L1 in brain-injured children compared with controls and also demonstrated a step-wise increase of biomarker concentrations over the continuum of severity from mild to severe TBI. Furthermore, while we found that only the neuronal biomarker UCH-L1 holds potential to detect acute intracranial lesions as assessed by computed tomography (CT), both markers were substantially increased in TBI patients even with a normal CT suggesting the presence of undetected microstructural injuries. Serum UCH-L1 and GFAP concentrations also strongly predicted poor outcome and performed better than S100B and MBP. Our results point to a role of GFAP and UCH-L1 as candidate biomarkers for pediatric TBI. Further studies are warranted.

A monoclonal antibody to ameliorate central nervous system infection and improve survival in a murine model of human Enterovirus-A71 encephalomyelitis

BACKGROUND

Enterovirus A71 (EV-A71) encephalomyelitis is an often fatal disease for which there is no specific treatment available. Passive immunization with a specific monoclonal antibody to EV-A71 was used on a murine model of EV-A71 encephalomyelitis to evaluate its therapeutic effectiveness before and after established central nervous system (CNS) infection.

METHODS

Mice were intraperitoneally-infected with a mouse-adapted EV-A71 strain and treated with a dose of monoclonal antibody (MAb) daily for 3 days on day 1, 2 and 3 post-infection or for 3 days on 3, 4 and 5 post-infection. Treatment effectiveness was evaluated by signs of infection and survival rate. Histopathology and qPCR analyses were performed on mice sacrificed a day after completing treatment.

RESULTS

In mock-treated mice, CNS infection was established from day 3 post-infection. All mice treated before established CNS infection, survived and recovered completely without CNS infection. All mice treated after established CNS infection survived with mild paralysis, and viral load and antigens/RNA at day 6 post-infection were significantly reduced.

CONCLUSIONS

Passive immunization with our MAb could prevent CNS infection in mice if given early before the establishment of CNS infection. It could also ameliorate established CNS infection if optimal and repeated doses were given.

Current Evidence for Developmental, Structural, and Functional Brain Defects following Prenatal Radiation Exposure

Ionizing radiation is omnipresent. We are continuously exposed to natural (e.g., radon and cosmic) and man-made radiation sources, including those from industry but especially from the medical sector. The increasing use of medical radiation modalities, in particular those employing low-dose radiation such as CT scans, raises concerns regarding the effects of cumulative exposure doses and the inappropriate utilization of these imaging techniques. One of the major goals in the radioprotection field is to better understand the potential health risk posed to the unborn child after radiation exposure to the pregnant mother, of which the first convincing evidence came from epidemiological studies on in utero exposed atomic bomb survivors. In the following years, animal models have proven to be an essential tool to further characterize brain developmental defects and consequent functional deficits. However, the identification of a possible dose threshold is far from complete and a sound link between early defects and persistent anomalies has not yet been established. This review provides an overview of the current knowledge on brain developmental and persistent defects resulting from in utero radiation exposure and addresses the many questions that still remain to be answered.

Atazanavir exposure in utero and neurodevelopment in infants: a comparative safety study

OBJECTIVE

To evaluate the safety of in-utero exposure to atazanavir and neurodevelopment in perinatally HIV-exposed but uninfected (PHEU) infants.

DESIGN

Prospective cohort study of mother-PHEU infant pairs in the Surveillance Monitoring for ART Toxicities protocol of the Pediatric HIV/AIDS Cohort Study.

METHODS

Pregnant women living with HIV who initiated an antiretroviral regimen during pregnancy were followed from the date of antiretroviral initiation. Women were classified according to whether the antiretroviral regimen contained atazanavir and the trimester of antiretroviral initiation. Neurodevelopment at 9-15 months was evaluated using the Bayley Scales of Infant and Toddler Development-Third Edition (Bayley-III). We estimated mean differences for the five Bayley-III domains for atazanavir-containing regimens versus all other regimens. Models included baseline covariates and adjustment for failure to complete the Bayley-III using inverse probability weighting.

RESULTS

PHEU infants were exposed in utero to atazanavir-containing (n = 167) and nonatazanavir-containing (n = 750) antiretroviral regimens. The adjusted mean differences (95% confidence interval) in Bayley-III domain scores for initiating an atazanavir-containing regimen in the first trimester were: cognitive, -1.5 (-6.2, 3.2); language, -3.3 (-7.6, 1.0); motor, -2.9 (-7.7, 1.9); social-emotional, 0.1 (-6.2, 6.4); and adaptive behavior, -0.1 (-4.3, 4.0). The mean differences for the second or third trimester were: cognitive, 0.4 (-3.2, 4.0); language, -3.4 (-6.2, -0.5); motor, 0.3 (-2.9, 3.4); social-emotional, -5.9 (-9.4, -2.3); and adaptive behavior, -2.5 (-5.9, 0.8).

CONCLUSION

In-utero exposure to atazanavir-containing regimens compared with non-atazanavir-containing regimens may adversely affect language and social-emotional development in PHEU infants during the first year of life, but the absolute difference is small.

The biological significance of brain barrier mechanisms: help or hindrance in drug delivery to the central nervous system?

Barrier mechanisms in the brain are important for its normal functioning and development. Stability of the brain's internal environment, particularly with respect to its ionic composition, is a prerequisite for the fundamental basis of its function, namely transmission of nerve impulses. In addition, the appropriate and controlled supply of a wide range of nutrients such as glucose, amino acids, monocarboxylates, and vitamins is also essential for normal development and function. These are all cellular functions across the interfaces that separate the brain from the rest of the internal environment of the body. An essential morphological component of all but one of the barriers is the presence of specialized intercellular tight junctions between the cells comprising the interface: endothelial cells in the blood-brain barrier itself, cells of the arachnoid membrane, choroid plexus epithelial cells, and tanycytes (specialized glial cells) in the circumventricular organs. In the ependyma lining the cerebral ventricles in the adult brain, the cells are joined by gap junctions, which are not restrictive for intercellular movement of molecules. But in the developing brain, the forerunners of these cells form the neuroepithelium, which restricts exchange of all but the smallest molecules between cerebrospinal fluid and brain interstitial fluid because of the presence of strap junctions between the cells. The intercellular junctions in all these interfaces are the physical basis for their barrier properties. In the blood-brain barrier proper, this is combined with a paucity of vesicular transport that is a characteristic of other vascular beds. Without such a diffusional restrain, the cellular transport mechanisms in the barrier interfaces would be ineffective. Superimposed on these physical structures are physiological mechanisms as the cells of the interfaces contain various metabolic transporters and efflux pumps, often ATP-binding cassette (ABC) transporters, that provide an important component of the barrier functions by either preventing entry of or expelling numerous molecules including toxins, drugs, and other xenobiotics. In this review, we summarize these influx and efflux mechanisms in normal developing and adult brain, as well as indicating their likely involvement in a wide range of neuropathologies. There have been extensive attempts to overcome the barrier mechanisms that prevent the entry of many drugs of therapeutic potential into the brain. We outline those that have been tried and discuss why they may so far have been largely unsuccessful. Currently, a promising approach appears to be focal, reversible disruption of the blood-brain barrier using focused ultrasound, but more work is required to evaluate the method before it can be tried in patients. Overall, our view is that much more fundamental knowledge of barrier mechanisms and development of new experimental methods will be required before drug targeting to the brain is likely to be a successful endeavor. In addition, such studies, if applied to brain pathologies such as stroke, trauma, or multiple sclerosis, will aid in defining the contribution of brain barrier pathology to these conditions, either causative or secondary.

Pharmacokinetics, pharmacodynamics, and efficacy of a small-molecule SMN2 splicing modifier in mouse models of spinal muscular atrophy

Spinal muscular atrophy (SMA) is caused by the loss or mutation of both copies of the survival motor neuron 1 (SMN1) gene. The related SMN2 gene is retained, but due to alternative splicing of exon 7, produces insufficient levels of the SMN protein. Here, we systematically characterize the pharmacokinetic and pharmacodynamics properties of the SMN splicing modifier SMN-C1. SMN-C1 is a low-molecular weight compound that promotes the inclusion of exon 7 and increases production of SMN protein in human cells and in two transgenic mouse models of SMA. Furthermore, increases in SMN protein levels in peripheral blood mononuclear cells and skin correlate with those in the central nervous system (CNS), indicating that a change of these levels in blood or skin can be used as a non-invasive surrogate to monitor increases of SMN protein levels in the CNS. Consistent with restored SMN function, SMN-C1 treatment increases the levels of spliceosomal and U7 small-nuclear RNAs and corrects RNA processing defects induced by SMN deficiency in the spinal cord of SMNΔ7 SMA mice. A 100% or greater increase in SMN protein in the CNS of SMNΔ7 SMA mice robustly improves the phenotype. Importantly, a ∼50% increase in SMN leads to long-term survival, but the SMA phenotype is only partially corrected, indicating that certain SMA disease manifestations may respond to treatment at lower doses. Overall, we provide important insights for the translation of pre-clinical data to the clinic and further therapeutic development of this series of molecules for SMA treatment.

Ontogeny of ABC and SLC transporters in the microvessels of developing rat brain

The blood-brain barrier (BBB) is responsible for the control of solutes' concentration in the brain. Tight junctions and multiple ATP-binding cassette (ABC) and SoLute Carrier (SLC) efflux transporters protect brain cells from xenobiotics, therefore reducing brain exposure to intentionally administered drugs. In epilepsy, polymorphisms and overexpression of efflux transporters genes could be associated with pharmacoresistance. The ontogeny of these efflux transporters should also be addressed because their expression during development may be related to different brain exposure to antiepileptic drugs in the immature brain. We detected statistically significant higher expression of Abcb1b and Slc16a1 genes, and lower expression of Abcb1a and Abcg2 genes between the post-natal day 14 (P14) and the adult rat microvessels. P-gP efflux activity was also shown to be lower in P14 rats when compared with the adults. The P-gP proteins coded by rodent genes Abcb1a and Abcb1b are known to have different substrate affinities. The role of the Abcg2 gene is less clear in pharmacoresistance in epilepsy, nonetheless the coded protein Bcrp is frequently associated with drug resistance. Finally, we observed a higher expression of the Mct1 transporter gene in the P14 rat brain microvessels. Accordingly to our results, we suppose that age may be another factor influencing brain exposure to antiepileptics as a consequence of different expression patterns of efflux transporters between the adult and immature BBB.

Mechanisms of restriction of viral neuroinvasion at the blood-brain barrier

The blood-brain barrier (BBB) consists of highly specialized cells including brain microvascular endothelial cells, astrocytes, microglia, pericytes, and neurons, which act in concert to restrict the entry of pathogens, immune cells, and soluble molecules into the central nervous system (CNS). If pathogens manage to cross the BBB and establish infection within the CNS, the BBB can open in a regulated manner to allow leukocyte transmigration into the CNS so that microbes, infected cells, and debris can be cleared. This review highlights how different inflammatory cytokines or signaling pathways disrupt or enhance BBB integrity in a way that regulates entry of neurotropic viruses into the CNS.

A Review of the Mechanisms of Blood-Brain Barrier Permeability by Tissue-Type Plasminogen Activator Treatment for Cerebral Ischemia

Cerebrovascular homeostasis is maintained by the blood-brain barrier (BBB), which forms a mechanical and functional barrier between systemic circulation and the central nervous system (CNS). In patients with ischemic stroke, the recombinant tissue-type plasminogen activator (rt-PA) is used to accelerate recanalization of the occluded vessels. However, rt-PA is associated with a risk of increasing intracranial bleeding (ICB). This effect is thought to be caused by the increase in cerebrovascular permeability though various factors such as ischemic reperfusion injury and the activation of matrix metalloproteinases (MMPs), but the detailed mechanisms are unknown. It was recently found that rt-PA treatment enhances BBB permeability not by disrupting the BBB, but by activating the vascular endothelial growth factor (VEGF) system. The VEGF regulates both the dissociation of endothelial cell (EC) junctions and endothelial endocytosis, and causes a subsequent increase in vessel permeability through the VEGF receptor-2 (VEGFR-2) activation in ECs. Here, we review the possibility that rt-PA increases the penetration of toxic molecules derived from the bloodstream including rt-PA itself, without disrupting the BBB, and contributes to these detrimental processes in the cerebral parenchyma.

CNS uptake of bortezomib is enhanced by P-glycoprotein inhibition: implications for spinal muscular atrophy

The development of therapeutics for neurological disorders is constrained by limited access to the central nervous system (CNS). ATP-binding cassette (ABC) transporters, particularly P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), are expressed on the luminal surface of capillaries in the CNS and transport drugs out of the endothelium back into the blood against the concentration gradient. Survival motor neuron (SMN) protein, which is deficient in spinal muscular atrophy (SMA), is a target of the ubiquitin proteasome system. Inhibiting the proteasome in a rodent model of SMA with bortezomib increases SMN protein levels in peripheral tissues but not the CNS, because bortezomib has poor CNS penetrance. We sought to determine if we could inhibit SMN degradation in the CNS of SMA mice with a combination of bortezomib and the ABC transporter inhibitor tariquidar. In cultured cells we show that bortezomib is a substrate of P-gp. Mass spectrometry analysis demonstrated that intraperitoneal co-administration of tariquidar increased the CNS penetrance of bortezomib, and reduced proteasome activity in the brain and spinal cord. This correlated with increased SMN protein levels and improved survival and motor function of SMA mice. These findings show that CNS penetrance of treatment for this neurological disorder can be improved by inhibiting drug efflux at the blood-brain barrier.

Tight junction modulation of the blood brain barrier: CNS delivery of small molecules

The blood brain barrier (BBB) represents a major obstacle for targeted drug delivery to the brain for the treatment of central nervous system (CNS) disorders. Significant advances in barrier research over the past decade has led to the discovery of an increasing number of structural and regulatory proteins in tight junctions (TJ) and adherens junctions (AJ). These discoveries are providing the framework for the development of novel TJ modulators which can act specifically and temporarily to alter BBB function and regulate paracellular uptake of molecules. TJ modulators that have shown therapeutic potential in preclinical models include claudin-5 and occludin siRNAs, peptides derived from zonula occludens toxin as well as synthetic peptides targeting the extracellular loops of TJs. Adding to the array of modulating agents are novel mechanisms of BBB regulation such as focused ultrasound (FUS). This review will give a succinct overview of BBB biology and TJ modulation in general. Novel insights into BBB regulation in health and disease will also be summarized.

Fever after intraventricular neuroendoscopic procedures in children

PURPOSE

The purpose of this paper was to study the incidence and clinical significance of fever after intraventricular neuroendoscopic procedures in children.

METHODS

We retrospectively assessed all children subjected to an intraventricular neuroendoscopic procedure between 2004 and 2015. Body temperature 6 days postoperatively, symptoms and signs, and eventual cerebrospinal fluid analysis were evaluated. Fever was defined as temperature above 38 °C.

RESULTS

Fifty-five children (mean age 4.8 years) had 67 procedures. Forty-three children (47 procedures, 70 %) developed fever, mostly the day of surgery (n = 17; 25 %) or the next day (n = 33; 49 %). All children who were clinically ill (n = 9, including 7 with fever) suffered serious illness, as opposed to none of the children with fever without being clinically ill (n = 36). Fever was unrelated to gender, indication for, and type of procedure and did not influence ETV success rate at 3 months. Children under 1 year less frequently developed fever (p = 0.032).

CONCLUSIONS

Fever frequently develops after intraventricular neuroendoscopic procedures in children and follows a rather predictable course, peaking the day of surgery and/or the next day, and rapidly subsiding thereafter. Fever is not a cardinal symptom except when combined with other symptoms in children who are clinically ill (which most of them are not). Close observation avoiding invasive diagnostic tests may suffice for those who are not clinically ill, while extra attention should be paid to those whose temperature rises after day 2 especially when clinically ill, as they likely suffer serious illness. We recommend to closely observe children after any intraventricular neuroendoscopic procedure for at least 5 days.

Air pollution, a rising environmental risk factor for cognition, neuroinflammation and neurodegeneration: The clinical impact on children and beyond

Air pollution (indoors and outdoors) is a major issue in public health as epidemiological studies have highlighted its numerous detrimental health consequences (notably, respiratory and cardiovascular pathological conditions). Over the past 15 years, air pollution has also been considered a potent environmental risk factor for neurological diseases and neuropathology. This review examines the impact of air pollution on children's brain development and the clinical, cognitive, brain structural and metabolic consequences. Long-term potential consequences for adults' brains and the effects on multiple sclerosis (MS) are also discussed. One challenge is to assess the effects of lifetime exposures to outdoor and indoor environmental pollutants, including occupational exposures: how much, for how long and what type. Diffuse neuroinflammation, damage to the neurovascular unit, and the production of autoantibodies to neural and tight-junction proteins are worrisome findings in children chronically exposed to concentrations above the current standards for ozone and fine particulate matter (PM2.5), and may constitute significant risk factors for the development of Alzheimer's disease later in life. Finally, data supporting the role of air pollution as a risk factor for MS are reviewed, focusing on the effects of PM10 and nitrogen oxides.

A Novel Dynamic Neonatal Blood-Brain Barrier on a Chip

Studies of neonatal neural pathologies and development of appropriate therapeutics are hampered by a lack of relevant in vitro models of neonatal blood-brain barrier (BBB). To establish such a model, we have developed a novel blood-brain barrier on a chip (B³C) that comprises a tissue compartment and vascular channels placed side-by-side mimicking the three-dimensional morphology, size and flow characteristics of microvessels in vivo. Rat brain endothelial cells (RBEC) isolated from neonatal rats were seeded in the vascular channels of B³C and maintained under shear flow conditions, while neonatal rat astrocytes were cultured under static conditions in the tissue compartment of the B³C. RBEC formed continuous endothelial lining with a central lumen along the length of the vascular channels of B³C and exhibited tight junction formation, as measured by the expression of zonula occludens-1 (ZO-1). ZO-1 expression significantly increased with shear flow in the vascular channels and with the presence of astrocyte conditioned medium (ACM) or astrocytes cultured in the tissue compartment. Consistent with in vivo BBB, B³C allowed endfeet-like astrocyte-endothelial cell interactions through a porous interface that separates the tissue compartment containing cultured astrocytes from the cultured RBEC in the vascular channels. The permeability of fluorescent 40 kDa dextran from vascular channel to the tissue compartment significantly decreased when RBEC were cultured in the presence of astrocytes or ACM (from 41.0±0.9 x 10⁻⁶ cm/s to 2.9±1.0 x 10⁻⁶ cm/s or 1.1±0.4 x 10⁻⁶ cm/s, respectively). Measurement of electrical resistance in B³C further supports that the addition of ACM significantly improves the barrier function in neonatal RBEC. Moreover, B³C exhibits significantly improved barrier characteristics compared to the transwell model and B³C permeability was not significantly different from the in vivo BBB permeability in neonatal rats. In summary, we developed a first dynamic in vitro neonatal BBB on a chip (B³C) that closely mimics the in vivo microenvironment, offers the flexibility of real time analysis, and is suitable for studies of BBB function as well as screening of novel therapeutics.

Therapeutic implications of the choroid plexus-cerebrospinal fluid interface in neuropsychiatric disorders

The choroid plexus (CP) comprises an epithelial monolayer that forms an important physical, enzymatic and immunologic barrier, called the blood-cerebrospinal fluid barrier (BCSFB). It is a highly vascularized organ located in the brain ventricles that is key in maintaining brain homeostasis as it produces cerebrospinal fluid (CSF) and has other important secretory functions. Furthermore, the CP-CSF interface plays a putative role in neurogenesis and has been implicated in neuropsychiatric diseases such as the neurodevelopmental disorders schizophrenia and autism. A role for this CNS border was also implicated in sleep disturbances and chronic and/or severe stress, which are risk factors for the development of neuropsychiatric conditions. Understanding the mechanisms by which disturbance of the homeostasis at the CP-CSF interface is involved in these different chronic low-grade inflammatory diseases can give new insights into therapeutic strategies. Hence, this review discusses the different roles that have been suggested so far for the CP in these neuropsychiatric disorders, with special attention to potential therapeutic applications.

Penetration of Treosulfan and its Active Monoepoxide Transformation Product into Central Nervous System of Juvenile and Young Adult Rats

Treosulfan (TREO) is currently investigated as an alternative treatment of busulfan in conditioning before hematopoietic stem cell transplantation. The knowledge of the blood-brain barrier penetration of the drug is still scarce. In this paper, penetration of TREO and its active monoepoxide (S,S-EBDM) and diepoxide (S,S-DEB) into the CNS was studied in juvenile (JR) and young adult rats (YAR) for the first time. CD rats of both sexes (n = 96) received an intravenous dose of TREO 500 mg/kg b.wt. Concentrations of TREO, S,S-EBDM, and S,S-DEB in rat plasma, brain, and cerebrospinal fluid (CSF, in YAR only) were determined by validated bioanalytical methods. Pharmacokinetic calculations were performed in WinNonlin using a noncompartmental analysis and statistical evaluation was done in Statistica software. In male JR, female JR, male YAR, and female YAR, the brain/plasma area under the curve (AUC) ratio for unbound TREO was 0.14, 0.17, 0.10, and 0.07 and for unbound S,S-EBDM, it was 0.52, 0.48, 0.28, and 0.22, respectively. The CSF/plasma AUC ratio in male and female YAR was 0.12 and 0.11 for TREO and 0.66 and 0.64 for S,S-EBDM, respectively. Elimination rate constants of TREO and S,S-EBDM in all the matrices were sex-independent with a tendency to be lower in the JR. No quantifiable levels of S,S-DEB were found in the studied samples. TREO and S,S-EBDM demonstrated poor and sex-independent penetration into CNS. However, the brain exposure was greater in juvenile rats, so very young children might potentially be more susceptible to high-dose TREO-related CNS exposure than young adults.

Systemic dendrimer-drug treatment of ischemia-induced neonatal white matter injury

Extreme prematurity is a major risk factor for perinatal and neonatal brain injury, and can lead to white matter injury that is a precursor for a number of neurological diseases, including cerebral palsy (CP) and autism. Neuroinflammation, mediated by activated microglia and astrocytes, is implicated in the pathogenesis of neonatal brain injury. Therefore, targeted drug delivery to attenuate neuroinflammation may greatly improve therapeutic outcomes in models of perinatal white matter injury. In this work, we use a mouse model of ischemia-induced neonatal white matter injury to study the biodistribution of generation 4, hydroxyl-functionalized polyamidoamine dendrimers. Following systemic administration of the Cy5-labeled dendrimer (D-Cy5), we demonstrate dendrimer uptake in cells involved in ischemic injury, and in ongoing inflammation, leading to secondary injury. The sub-acute response to injury is driven by astrocytes. Within five days of injury, microglial proliferation and migration occurs, along with limited differentiation of oligodendrocytes and oligodendrocyte death. From one day to five days after injury, a shift in dendrimer co-localization occurred. Initially, dendrimer predominantly co-localized with astrocytes, with a subsequent shift towards microglia. Co-localization with oligodendrocytes reduced over the same time period, demonstrating a region-specific uptake based on the progression of the injury. We further show that systemic administration of a single dose of dendrimer-N-acetyl cysteine conjugate (D-NAC) at either sub-acute or delayed time points after injury results in sustained attenuation of the 'detrimental' pro-inflammatory response up to 9days after injury, while not impacting the 'favorable' anti-inflammatory response. The D-NAC therapy also led to improvement in myelination, suggesting reduced white matter injury. Demonstration of treatment efficacy at later time points in the postnatal period provides a greater understanding of how microglial activation and chronic inflammation can be targeted to treat neonatal brain injury. Importantly, it may also provide a longer therapeutic window.

Cerebrospinal fluid and plasma oxytocin concentrations are positively correlated and negatively predict anxiety in children

The neuropeptide oxytocin (OXT) exerts anxiolytic and prosocial effects in the central nervous system of rodents. A number of recent studies have attempted to translate these findings by investigating the relationships between peripheral (e.g., blood, urinary and salivary) OXT concentrations and behavioral functioning in humans. Although peripheral samples are easy to obtain in humans, whether peripheral OXT measures are functionally related to central OXT activity remains unclear. To investigate a possible relationship, we quantified OXT concentrations in concomitantly collected cerebrospinal fluid (CSF) and blood samples from child and adult patients undergoing clinically indicated lumbar punctures or other CSF-related procedures. Anxiety scores were obtained in a subset of child participants whose parents completed psychometric assessments. Findings from this study indicate that plasma OXT concentrations significantly and positively predict CSF OXT concentrations (r=0.56, P=0.0064, N=27). Moreover, both plasma (r=-0.92, P=0.0262, N=10) and CSF (r=-0.91, P=0.0335, N=10) OXT concentrations significantly and negatively predicted trait anxiety scores, consistent with the preclinical literature. Importantly, plasma OXT concentrations significantly and positively (r=0.96, P=0.0115, N=10) predicted CSF OXT concentrations in the subset of child participants who provided behavioral data. This study provides the first empirical support for the use of blood measures of OXT as a surrogate for central OXT activity, validated in the context of behavioral functioning. These preliminary findings also suggest that impaired OXT signaling may be a biomarker of anxiety in humans, and a potential target for therapeutic development in individuals with anxiety disorders.

5p deletions: Current knowledge and future directions

Disorders resulting from 5p deletions (5p-) were first recognized by Lejeune et al. in 1963 [Lejeune et al. (1963); C R Hebd Seances Acad Sci 257:3098-3102]. 5p- is caused by partial or total deletion of the short arm of chromosome 5. The most recognizable phenotype is characterized by a high-pitched cry, dysmorphic features, poor growth, and developmental delay. This report reviews 5p- disorders and their molecular basis. Hemizygosity for genes located within this region have been implicated in contributing to the phenotype. A review of the genes on 5p which may be dosage sensitive is summarized. Because of the growing knowledge of these specific genes, future directions to explore potential targeted therapies for individuals with 5p- are discussed. © 2015 Wiley Periodicals, Inc.

Neuronal and vascular interactions

The brain, which represents 2% of body mass but consumes 20% of body energy at rest, has a limited capacity to store energy and is therefore highly dependent on oxygen and glucose supply from the blood stream. Normal functioning of neural circuits thus relies on adequate matching between metabolic needs and blood supply. Moreover, not only does the brain need to be densely vascularized, it also requires a tightly controlled environment free of toxins and pathogens to provide the proper chemical composition for synaptic transmission and neuronal function. In this review, we focus on three major factors that ensure optimal brain perfusion and function: the patterning of vascular networks to efficiently deliver blood and nutrients, the function of the blood-brain barrier to maintain brain homeostasis, and the regulation of cerebral blood flow to adequately couple energy supply to neural function.

Influx mechanisms in the embryonic and adult rat choroid plexus: a transcriptome study

The transcriptome of embryonic and adult rat lateral ventricular choroid plexus, using a combination of RNA-Sequencing and microarray data, was analyzed by functional groups of influx transporters, particularly solute carrier (SLC) transporters. RNA-Seq was performed at embryonic day (E) 15 and adult with additional data obtained at intermediate ages from microarray analysis. The largest represented functional group in the embryo was amino acid transporters (twelve) with expression levels 2–98 times greater than in the adult. In contrast, in the adult only six amino acid transporters were up-regulated compared to the embryo and at more modest enrichment levels (<5-fold enrichment above E15). In E15 plexus five glucose transporters, in particular Glut-1, and only one monocarboxylate transporter were enriched compared to the adult, whereas only two glucose transporters but six monocarboxylate transporters in the adult plexus were expressed at higher levels than in embryos. These results are compared with earlier published physiological studies of amino acid and monocarboxylate transport in developing rodents. This comparison shows correlation of high expression of some transporters in the developing brain with higher amino acid transport activity reported previously. Data for divalent metal transporters are also considered. Immunohistochemistry of several transporters (e.g., Slc16a10, a thyroid hormone transporter) gene products was carried out to confirm translational activity and to define cellular distribution of the proteins. Overall the results show that there is substantial expression of numerous influx transporters in the embryonic choroid plexus, many at higher levels than in the adult. This, together with immunohistochemical evidence and data from published physiological transport studies suggests that the choroid plexus in embryonic brain plays a major role in supplying the developing brain with essential nutrients.

It takes a village: constructing the neurogenic niche

Although many features of neurogenesis during development and in the adult are intrinsic to the neurogenic cells themselves, the role of the microenvironment is irrefutable. The neurogenic niche is a melting pot of cells and factors that influence CNS development. How do the diverse elements assemble and when? How does the niche change structurally and functionally during embryogenesis and in adulthood? In this review, we focus on the impact of non-neural cells that participate in the neurogenic niche, highlighting how cells of different embryonic origins influence this critical germinal space.

Outer brain barriers in rat and human development

Complex barriers at the brain's surface, particularly in development, are poorly defined. In the adult, arachnoid blood-cerebrospinal fluid (CSF) barrier separates the fenestrated dural vessels from the CSF by means of a cell layer joined by tight junctions. Outer CSF-brain barrier provides diffusion restriction between brain and subarachnoid CSF through an initial radial glial end feet layer covered with a pial surface layer. To further characterize these interfaces we examined embryonic rat brains from E10 to P0 and forebrains from human embryos and fetuses (6–21st weeks post-conception) and adults using immunohistochemistry and confocal microscopy. Antibodies against claudin-11, BLBP, collagen 1, SSEA-4, MAP2, YKL-40, and its receptor IL-13Rα2 and EAAT1 were used to describe morphological characteristics and functional aspects of the outer brain barriers. Claudin-11 was a reliable marker of the arachnoid blood-CSF barrier. Collagen 1 delineated the subarachnoid space and stained pial surface layer. BLBP defined radial glial end feet layer and SSEA-4 and YKL-40 were present in both leptomeningeal cells and end feet layer, which transformed into glial limitans. IL-13Rα2 and EAAT1 were present in the end feet layer illustrating transporter/receptor presence in the outer CSF-brain barrier. MAP2 immunostaining in adult brain outlined the lower border of glia limitans; remnants of end feet were YKL-40 positive in some areas. We propose that outer brain barriers are composed of at least 3 interfaces: blood-CSF barrier across arachnoid barrier cell layer, blood-CSF barrier across pial microvessels, and outer CSF-brain barrier comprising glial end feet layer/pial surface layer.

Blood-brain barrier dysfunction in disorders of the developing brain

Disorders of the developing brain represent a major health problem. The neurological manifestations of brain lesions can range from severe clinical deficits to more subtle neurological signs or behavioral problems and learning disabilities, which often become evident many years after the initial damage. These long-term sequelae are due at least in part to central nervous system immaturity at the time of the insult. The blood-brain barrier (BBB) protects the brain and maintains homeostasis. BBB alterations are observed during both acute and chronic brain insults. After an insult, excitatory amino acid neurotransmitters are released, causing reactive oxygen species (ROS)-dependent changes in BBB permeability that allow immune cells to enter and stimulate an inflammatory response. The cytokines, chemokines and other molecules released as well as peripheral and local immune cells can activate an inflammatory cascade in the brain, leading to secondary neurodegeneration that can continue for months or even years and finally contribute to post-insult neuronal deficits. The role of the BBB in perinatal disorders is poorly understood. The inflammatory response, which can be either acute (e.g., perinatal stroke, traumatic brain injury) or chronic (e.g., perinatal infectious diseases) actively modulates the pathophysiological processes underlying brain injury. We present an overview of current knowledge about BBB dysfunction in the developing brain during acute and chronic insults, along with clinical and experimental data.

A rat model of nerve agent exposure applicable to the pediatric population: The anticonvulsant efficacies of atropine and GluK1 antagonists

Inhibition of acetylcholinesterase (AChE) after nerve agent exposure induces status epilepticus (SE), which causes brain damage or death. The development of countermeasures appropriate for the pediatric population requires testing of anticonvulsant treatments in immature animals. In the present study, exposure of 21-day-old (P21) rats to different doses of soman, followed by probit analysis, produced an LD50 of 62μg/kg. The onset of behaviorally-observed SE was accompanied by a dramatic decrease in brain AChE activity; rats who did not develop SE had significantly less reduction of AChE activity in the basolateral amygdala than rats who developed SE. Atropine sulfate (ATS) at 2mg/kg, administered 20 min after soman exposure (1.2×LD50), terminated seizures. ATS at 0.5mg/kg, given along with an oxime within 1 min after exposure, allowed testing of anticonvulsants at delayed time-points. The AMPA/GluK1 receptor antagonist LY293558, or the specific GluK1 antagonist UBP302, administered 1h post-exposure, terminated SE. There were no degenerating neurons in soman-exposed P21 rats, but both the amygdala and the hippocampus were smaller than in control rats at 30 and 90days post-exposure; this pathology was not present in rats treated with LY293558. Behavioral deficits present at 30 days post-exposure, were also prevented by LY293558 treatment. Thus, in immature animals, a single injection of atropine is sufficient to halt nerve agent-induced seizures, if administered timely. Testing anticonvulsants at delayed time-points requires early administration of ATS at a low dose, sufficient to counteract only peripheral toxicity. LY293558 administered 1h post-exposure, prevents brain pathology and behavioral deficits.

The inner CSF-brain barrier: developmentally controlled access to the brain via intercellular junctions

In the adult the interface between the cerebrospinal fluid and the brain is lined by the ependymal cells, which are joined by gap junctions. These intercellular connections do not provide a diffusional restrain between the two compartments. However, during development this interface, initially consisting of neuroepithelial cells and later radial glial cells, is characterized by “strap” junctions, which limit the exchange of different sized molecules between cerebrospinal fluid and the brain parenchyma. Here we provide a systematic study of permeability properties of this inner cerebrospinal fluid-brain barrier during mouse development from embryonic day, E17 until adult. Results show that at fetal stages exchange across this barrier is restricted to the smallest molecules (286Da) and the diffusional restraint is progressively removed as the brain develops. By postnatal day P20, molecules the size of plasma proteins (70 kDa) diffuse freely. Transcriptomic analysis of junctional proteins present in the cerebrospinal fluid-brain interface showed expression of adherens junctional proteins, actins, cadherins and catenins changing in a development manner consistent with the observed changes in the permeability studies. Gap junction proteins were only identified in the adult as was claudin-11. Immunohistochemistry was used to localize at the cellular level some of the adherens junctional proteins of genes identified from transcriptomic analysis. N-cadherin, β - and α-catenin immunoreactivity was detected outlining the inner CSF-brain interface from E16; most of these markers were not present in the adult ependyma. Claudin-5 was present in the apical-most part of radial glial cells and in endothelial cells in embryos, but only in endothelial cells including plexus endothelial cells in adults. Claudin-11 was only immunopositive in the adult, consistent with results obtained from transcriptomic analysis. These results provide information about physiological, molecular and morphological-related permeability changes occurring at the inner cerebrospinal fluid-brain barrier during brain development.

ECG in neonate mice with spinal muscular atrophy allows assessment of drug efficacy

Molecular technologies have produced diverse arrays of animal models for studying genetic diseases and potential therapeutics. Many have neonatal phenotypes. Spinal muscular atrophy (SMA) is a neuromuscular disorder primarily affecting children, and is of great interest in translational medicine. The most widely used SMA mouse models require all phenotyping to be performed in neonates since they do not survive much past weaning. Pre-clinical studies in neonate mice can be hindered by toxicity and a lack of quality phenotyping assays, since many assays are invalid in pups or require subjective scoring with poor inter-rater variability. We find, however, that passive electrocardiography (ECG) recording in conscious 11-day old SMA mice provides sensitive outcome measures, detecting large differences in heart rate, cardiac conduction, and autonomic control resulting from disease. We find significant drug benefits upon treatment with G418, an aminoglycoside targeting the underlying protein deficiency, even in the absence of overt effects on growth and survival. These findings provide several quantitative physiological biomarkers for SMA preclinical studies, and will be of utility to diverse disease models featuring neonatal cardiac arrhythmias.

The molecular, cellular, and morphological components of blood-brain barrier development during embryogenesis

The blood brain barrier (BBB) is a hallmark of blood vessels in the brain and functions to protect the brain from unwanted blood born materials, support the unique metabolic needs of the brain, and define a stable environment crucial for brain homeostasis. The temporal profile of BBB development was long debated until recent studies produced convincing evidence demonstrating that the BBB is established and functional during embryogenesis. Here we review research focused on the molecular, cellular and morphological characteristics of BBB development. Our review discusses the precise temporal profile of BBB formation, the development of endothelial cell ultrastructure and the molecular components that provide sealing and transporting properties, the molecular pathways involved in the induction of BBB specific endothelial cell differentiation, the signaling pathways driving developmental angiogenesis versus barrier-genesis, and finally the contribution of other cell types to BBB formation. We examine aspects of BBB development that are still unresolved while highlighting research tools that could provide new insight to answer these open questions.

The rights and wrongs of blood-brain barrier permeability studies: a walk through 100 years of history

Careful examination of relevant literature shows that many of the most cherished concepts of the blood-brain barrier are incorrect. These include an almost mythological belief in its immaturity that is unfortunately often equated with absence or at least leakiness in the embryo and fetus. The original concept of a blood-brain barrier is often attributed to Ehrlich; however, he did not accept that permeability of cerebral vessels was different from other organs. Goldmann is often credited with the first experiments showing dye (trypan blue) exclusion from the brain when injected systemically, but not when injected directly into it. Rarely cited are earlier experiments of Bouffard and of Franke who showed methylene blue and trypan red stained all tissues except the brain. The term “blood-brain barrier” “Blut-Hirnschranke” is often attributed to Lewandowsky, but it does not appear in his papers. The first person to use this term seems to be Stern in the early 1920s. Studies in embryos by Stern and colleagues, Weed and Wislocki showed results similar to those in adult animals. These were well-conducted experiments made a century ago, thus the persistence of a belief in barrier immaturity is puzzling. As discussed in this review, evidence for this belief, is of poor experimental quality, often misinterpreted and often not properly cited. The functional state of blood-brain barrier mechanisms in the fetus is an important biological phenomenon with implications for normal brain development. It is also important for clinicians to have proper evidence on which to advise pregnant women who may need to take medications for serious medical conditions. Beliefs in immaturity of the blood-brain barrier have held the field back for decades. Their history illustrates the importance of taking account of all the evidence and assessing its quality, rather than selecting papers that supports a preconceived notion or intuitive belief. This review attempts to right the wrongs. Based on careful translation of original papers, some published a century ago, as well as providing discussion of studies claiming to show barrier immaturity, we hope that readers will have evidence on which to base their own conclusions.

Plasma vasopressin concentrations positively predict cerebrospinal fluid vasopressin concentrations in human neonates

Central arginine vasopressin (AVP) plays a critical role in mammalian social behavior and has been hypothesized to be a biomarker of certain human neurodevelopmental disorders, including autism. However, opportunities to collect post-mortem brain tissue or cerebrospinal fluid (CSF) from children are extremely limited, and the use of less invasive peripheral assessments (e.g., blood, urine, or saliva) of AVP as a proxy for more invasive central measures has not been well validated. Further, almost nothing is known about AVP biology in very young infants. Therefore in the present study we concomitantly collected basal CSF and plasma samples from N = 20 neonates undergoing clinical sepsis evaluation (all were sepsis negative) and quantified AVP concentrations via well-validated enzyme-immunoassay methodology. Plasma AVP concentrations significantly and positively predicted CSF AVP concentrations (r = 0.73, p = 0.0021), and this relationship persisted when variance attributed to sex, gestational age, and sample collection time was controlled for in the statistical model (r = 0.75, p = 0.0047). These findings provide preliminary support for the use of basal plasma AVP measurement as a proxy for basal brain AVP activity in pediatric populations. Future studies are now required to determine the relationship between behavioral measures and AVP concentrations in both central and peripheral compartments in young infants and older children.

Is oxytocin a maternal-foetal signalling molecule at birth? Implications for development

The neuropeptide oxytocin was first noted for its capacity to promote uterine contractions and facilitate delivery in mammals. The study of oxytocin has grown to include awareness that this peptide is a neuromodulator with broad effects throughout the body. Accumulating evidence suggests that oxytocin is a powerful signal to the foetus, helping to prepare the offspring for the extrauterine environment. Concurrently, the use of exogenous oxytocin or other drugs to manipulate labour has become common practice. The use of oxytocin to expedite labour and minimise blood loss improves both infant and maternal survival under some conditions. However, further investigations are needed to assess the developmental consequences of changes in oxytocin, such as those associated with pre-eclampsia or obstetric manipulations associated with birth. This review focuses on the role of endogenous and exogenous oxytocin as a neurochemical signal to the foetal nervous system. We also examine the possible developmental consequences, including those associated with autism spectrum disorder, that arise from exogenous oxytocin supplementation during labour.

Cellular specificity of the blood-CSF barrier for albumin transfer across the choroid plexus epithelium

To maintain the precise internal milieu of the mammalian central nervous system, well-controlled transfer of molecules from periphery into brain is required. Recently the soluble and cell-surface albumin-binding glycoprotein SPARC (secreted protein acidic and rich in cysteine) has been implicated in albumin transport into developing brain, however the exact mechanism remains unknown. We postulate that SPARC is a docking site for albumin, mediating its uptake and transfer by choroid plexus epithelial cells from blood into cerebrospinal fluid (CSF). We used in vivo physiological measurements of transfer of endogenous (mouse) and exogenous (human) albumins, in situ Proximity Ligation Assay (in situ PLA), and qRT-PCR experiments to examine the cellular mechanism mediating protein transfer across the blood–CSF interface. We report that at all developmental stages mouse albumin and SPARC gave positive signals with in situ PLAs in plasma, CSF and within individual plexus cells suggesting a possible molecular interaction. In contrast, in situ PLA experiments in brain sections from mice injected with human albumin showed positive signals for human albumin in the vascular compartment that were only rarely identifiable within choroid plexus cells and only at older ages. Concentrations of both endogenous mouse albumin and exogenous (intraperitoneally injected) human albumin were estimated in plasma and CSF and expressed as CSF/plasma concentration ratios. Human albumin was not transferred through the mouse blood–CSF barrier to the same extent as endogenous mouse albumin, confirming results from in situ PLA. During postnatal development Sparc gene expression was higher in early postnatal ages than in the adult and changed in response to altered levels of albumin in blood plasma in a differential and developmentally regulated manner. Here we propose a possible cellular route and mechanism by which albumin is transferred from blood into CSF across a sub-population of specialised choroid plexus epithelial cells.