The choroid plexus: function, pathology and therapeutic potential of its transplantation

Choroid plexus vascular reactivity in moyamoya: Implications for choroid plexus regulation in ischemic stress

BACKGROUND AND PURPOSE

Choroid plexus (ChP) hyperemia has been observed in patients with intracranial vasculopathy and to reduce following successful surgical revascularization. This observation may be attributable to impaired vascular reserve of the ChP or other factors, such as the ChP responding to circulating markers of stress. We extend this work to test the hypothesis that vascular reserve of the ChP is unrelated to intracranial vasculopathy.

METHODS

We performed hypercapnic reactivity (blood oxygenation level-dependent; echo time = 35 ms; spatial resolution = 3.5 × 3.5 × 3.5 mm, repetition time = 2000 ms) and catheter angiography assessments of ChP reserve capacity and vascular patency in moyamoya patients (n = 53) with and without prior surgical revascularization. Time regression analyses quantified maximum cerebrovascular reactivity and reactivity delay time in ChP and cortical flow territories of major intracranial vessels with steno-occlusion graded as <70%, 70%-99%, and occlusion using Warfarin-Aspirin-Symptomatic-Intracranial-Disease stenosis grading criteria. Analysis of variance (significance: two-sided Bonferroni-corrected p < .05) was applied to evaluate cortical and ChP reactivity, after accounting for end-tidal carbon dioxide change, for differing vasculopathy categories.

RESULTS

In patients without prior revascularization, arterial vasculopathy was associated with reduced cortical reactivity and lengthened reactivity delay (p ≤ .01), as expected. Regardless of surgical history, the ChP reactivity metrics were not significantly related to the degree of proximal stenosis, consistent with ChP reactivity being largely preserved in this population.

CONCLUSIONS

Findings are consistent with ChP reactivity in moyamoya not being dependent on observed vasculopathy. Future work may investigate the extent to which ChP hyperemia in chronic ischemia reflects circulating markers of glial or ischemic stress.

Choroid plexus epithelium and its role in neurological diseases

Choroid plexus epithelial cells can secrete cerebrospinal fluid into the ventricles, serving as the major structural basis of the selective barrier between the neurological system and blood in the brain. In fact, choroid plexus epithelial cells release the majority of cerebrospinal fluid, which is connected with particular ion channels in choroid plexus epithelial cells. Choroid plexus epithelial cells also produce and secrete a number of essential growth factors and peptides that help the injured cerebrovascular system heal. The pathophysiology of major neurodegenerative disorders like Alzheimer's disease, Parkinson's disease, as well as minor brain damage diseases like hydrocephalus and stroke is still unknown. Few studies have previously connected choroid plexus epithelial cells to the etiology of these serious brain disorders. Therefore, in the hopes of discovering novel treatment options for linked conditions, this review extensively analyzes the association between choroid plexus epithelial cells and the etiology of neurological diseases such as Alzheimer's disease and hydrocephalus. Finally, we review CPE based immunotherapy, choroid plexus cauterization, choroid plexus transplantation, and gene therapy.

Targeting choroid plexus epithelium as a novel therapeutic strategy for hydrocephalus

The choroid plexus is a tissue located in the lateral ventricles of the brain and is composed mainly of choroid plexus epithelium cells. The main function is currently thought to be the secretion of cerebrospinal fluid and the regulation of its pH, and more functions are gradually being demonstrated. Assistance in the removal of metabolic waste and participation in the apoptotic pathway are also the functions of choroid plexus. Besides, it helps to repair the brain by regulating the secretion of neuropeptides and the delivery of drugs. It is involved in the immune response to assist in the clearance of infections in the central nervous system. It is now believed that the choroid plexus is in an inflammatory state after damage to the brain. This state, along with changes in the cilia, is thought to be an abnormal physiological state of the choroid plexus, which in turn leads to abnormal conditions in cerebrospinal fluid and triggers hydrocephalus. This review describes the pathophysiological mechanism of hydrocephalus following choroid plexus epithelium cell abnormalities based on the normal physiological functions of choroid plexus epithelium cells, and analyzes the attempts and future developments of using choroid plexus epithelium cells as a therapeutic target for hydrocephalus.

Choroid plexus perfusion in sickle cell disease and moyamoya vasculopathy: Implications for glymphatic flow

Cerebrospinal fluid (CSF) and interstitial fluid exchange have been shown to increase following pharmacologically-manipulated increases in cerebral arterial pulsatility, consistent with arterial pulsatility improving CSF circulation along perivascular glymphatic pathways. The choroid plexus (CP) complexes produce CSF, and CP activity may provide a centralized indicator of perivascular flow. We tested the primary hypothesis that elevated cortical cerebral blood volume and flow, present in sickle cell disease (SCD), is associated with fractionally-reduced CP perfusion relative to healthy adults, and the supplementary hypothesis that reduced arterial patency, present in moyamoya vasculopathy, is associated with elevated fractional CP perfusion relative to healthy adults. Participants (n = 75) provided informed consent and were scanned using a 3-Tesla arterial-spin-labeling MRI sequence for CP and cerebral gray matter (GM) perfusion quantification. ANOVA was used to calculate differences in CP-to-GM perfusion ratios between groups, and regression analyses applied to evaluate the dependence of the CP-to-GM perfusion ratio on group after co-varying for age and sex. ANOVA yielded significant (p < 0.001) group differences, with CP-to-GM perfusion ratios increasing between SCD (ratio = 0.93 ± 0.28), healthy (ratio = 1.04 ± 0.32), and moyamoya (ratio = 1.29 ± 0.32) participants, which was also consistent with regression analyses. Findings are consistent with CP perfusion being inversely associated with cortical perfusion.

Conditioned Media of Choroid Plexus Epithelium Cells Attenuates High Pi-Induced Calcification of MOVAS Cells by Inhibiting ROS-Mediated Signal Pathways

Vascular calcification was an independent risk of cardiovascular and cerebrovascular diseases (CCDs). Studies reported that conditioned media of choroid plexus epithelium cells (CPECs-CM) showed potential neuroprotective effects. However, the protective effect of CPECs-CM against vascular calcification (VC) has not been reported yet. Herein, high phosphate (HPi)-induced calcification model in mouse aortic vascular smooth muscle cells (MOVAS) was established, and the protective effects and underlying mechanism of CPECs-CM against HPi-induced calcification were explored. The results indicated that CPEC cells were successfully isolated and cultured, and CPECs-CM co-treatment significantly inhibited HPi-induced calcification of MOVAS cells through blocking alkaline phosphatase activity and expression. CPECs-CM co-treatment also suppressed reactive oxide species-mediated DNA damage in HPi-treated MOVAS cells. Moreover, dysfunction of MAPKs and PI3K/AKT pathways both contributed to HPi-induced calcification of MOVAS cells, and CPECs-CM co-treatment attenuated HPi-induced calcification by normalizing MAPKs and PI3K/AKT expression. Taken together, our findings provide evidence that CPECs-CM had the potential to inhibit vascular calcification with potent application in chemoprevention and chemotherapy of human CCD.

The Regulation of Cerebral Spinal Fluid Flow and Its Relevance to the Glymphatic System

PURPOSE OF REVIEW

The glymphatic system is a relatively new concept that has been associated with regulation of cerebrospinal fluid (CSF), as well as brain waste clearance. Novel techniques to study glymphatic dysfunction have in turn prompted a reassessment of brain physiology and underlying elements of neurological disease. This review incorporates a contemporary imaging perspective focused on understanding the regulation of CSF flow, thus expanding the putative clinical relevance of this system and the relationships between CSF flow and glymphatic function.

RECENT FINDINGS

MR imaging studies, especially those that employ intrathecal gadolinium contrast, have identified potentially new pathways regulating CSF production, absorption, and clearance. These studies, when viewed in the context of more historical anatomic descriptors of CSF production and absorption, provide a more robust description of CSF physiology and waste clearance. CSF production and resorption are under-investigated and could be related to various pathophysiologic processes in neurodegeneration. Anatomically based clinical exemplars of CSF clearance are discussed. Future studies should focus on linking glymphatic functionality with neurological disease.

Molecular abnormalities in autopsied brain tissue from the inferior horn of the lateral ventricles of nonagenarians and Alzheimer disease patients

BACKGROUND

The ventricular system plays a vital role in blood-cerebrospinal fluid (CSF) exchange and interstitial fluid-CSF drainage pathways. CSF is formed in the specialized secretory tissue called the choroid plexus, which consists of epithelial cells, fenestrated capillaries and the highly vascularized stroma. Very little is currently known about the role played by the ventricles and the choroid plexus tissue in aging and Alzheimer's disease (AD).

METHODS

In this study, we used our state-of-the-art proteomic platform, a liquid chromatography/mass spectrometry (LC-MS/MS) approach coupled with Tandem Mass Tag isobaric labeling to conduct a detailed unbiased proteomic analyses of autopsied tissue isolated from the walls of the inferior horn of the lateral ventricles in AD (77.2 ± 0.6 yrs), age-matched controls (77.0 ± 0.5 yrs), and nonagenarian cases (93.2 ± 1.1 yrs).

RESULTS

Ingenuity pathway analyses identified phagosome maturation, impaired tight-junction signaling, and glucose/mannose metabolism as top significantly regulated pathways in controls vs nonagenarians. In matched-control vs AD cases we identified alterations in mitochondrial bioenergetics, oxidative stress, remodeling of epithelia adherens junction, macrophage recruitment and phagocytosis, and cytoskeletal dynamics. Nonagenarian vs AD cases demonstrated augmentation of oxidative stress, changes in gluconeogenesis-glycolysis pathways, and cellular effects of choroidal smooth muscle cell vasodilation. Amyloid plaque score uniquely correlated with remodeling of epithelial adherens junctions, Fc γ-receptor mediated phagocytosis, and alterations in RhoA signaling. Braak staging was uniquely correlated with altered iron homeostasis, superoxide radical degradation and phagosome maturation.

CONCLUSIONS

These changes provide novel insights to explain the compromise to the physiological properties and function of the ventricles/choroid plexus system in nonagenarian aging and AD pathogenesis. The pathways identified could provide new targets for therapeutic strategies to mitigate the divergent path towards AD.

Choroid plexus perfusion and intracranial cerebrospinal fluid changes after angiogenesis

Recent studies have provided evidence that cortical brain ischemia may influence choroid plexus function, and such communication may be mediated by either traditional CSF circulation pathways and/or a possible glymphatic pathway. Here we investigated the hypothesis that improvements in arterial health following neoangiogenesis alter (i) intracranial CSF volume and (ii) choroid plexus perfusion in humans. CSF and tissue volume measurements were obtained from T₁-weighted MRI, and cortical and choroid plexus perfusion were obtained from perfusion-weighted arterial spin labeling MRI, in patients with non-atherosclerotic intracranial stenosis (e.g. Moyamoya). Measurements were repeated after indirect surgical revascularization, which elicits cortical neoangiogenesis near the revascularization site (n = 23; age = 41.8 ± 13.4 years), or in a cohort of participants at two time points without interval surgeries (n = 10; age = 41.7 ± 10.7 years). Regression analyses were used to evaluate dependence of perfusion and volume on state (time 1 vs. 2). Post-surgery, neither CSF nor tissue volumes changed significantly. In surgical patients, cortical perfusion increased and choroid plexus perfusion decreased after surgery; in participants without surgeries, cortical perfusion reduced and choroid plexus perfusion increased between time points. Findings are discussed in the context of a homeostatic mechanism, whereby arterial health, paravascular flow, and/or ischemia can affect choroid plexus perfusion.

First definition of burned choroid plexus in acidic cerebrospinal fluid-filled brain ventricles during subarachnoid hemorrhage: Experimental study

Blood and cerebrospinal fluid (CSF) acidosis is the most troubling complication in subarachnoid hemorrhage (SAH) if carotid body (CB) networks are disrupted. However, histopathological examination of the choroid plexus (CP) in acidic CSF has not been evaluated so far. In this study, we aimed to investigate the CP in acidic CSF following SAH. Twenty-eight rabbits were used. Five rabbits were used to analyze CB network (control group; n = 5); seven rabbits were injected 1 mL of saline (Sham group; n = 7); and the rest 16 rabbits were given 1 mL of autologous arterial blood inject into the cisterna magna to create SAH (SAH group; n = 16). Blood and CSF pH values were recorded before/during/after the experimental procedures. Nuclear darkening, cellular shrinkage and pyknosis suggested the presence of apoptosis of epithelial cells of CP. The densities of normal and degenerated epithelial cells of CPs were estimated using stereological methods. The relationship between the pH values and degenerated epithelial cell densities of CPs were statistically compared by Mann-Whitney U-test. The pH values of blood were estimated as 7.359 ± 0.039 in the control group, 7.318 ± 0.062 in the Sham group, 7.23 ± 0.013 in the SAH group. CSF pH values were 7.313 ± 0.028 in the control group, 7.296 ± 0.045 in the Sham group, and 7.224 ± 0.012 in the SAH group. Degenerated epithelial cell density of CP was 25 ± 7 in the control group, 226 ± 64 in the Sham group, and 2115 ± 635 in the SAH group. There was a considerable link between CSF pH values and degenerated epithelial cells of CP (P < 0.0001). This study shows that CB insult causes acidosis of CSF as well as cellular degeneration of CP during SAH. This is the first description of this in the literature.

Embryonic cerebrospinal fluid formation and regulation

The vertebrate brain is organized, from its embryonic origin and throughout adult life, around a dynamic and complex fluid, the cerebrospinal fluid (CSF). There is growing interest in the composition, dynamics and function of the CSF in brain development research. It has been demonstrated in higher vertebrates that CSF has key functions in delivering diffusible signals and nutrients to the developing brain, contributing to the proliferation, differentiation and survival of neural progenitor cells, and to the patterning of the brain. It has also been shown that the composition and the homeostasis of CSF are tightly regulated following the closure of the anterior neuropore, just before the initiation of primary neurogenesis in the neural tissue surrounding brain cavities, before the formation of functional choroid plexus. In this review we draw together existing literature about the composition and formation of embryonic cerebrospinal fluid in birds and mammals, from the closure of the anterior neuropore to the formation of functional fetal choroid plexus, including mechanisms regulating its composition and homeostasis. The significance of CSF regulation within embryonic brain is also discussed from an evolutionary perspective.

Effects of passage and cryopreservation on neurotrophic factor secretion from choroid plexus epithelial cells

The aim of the present study was to evaluate the effects of passage and cryopreservation of choroid plexus epithelial cells on their secretion of neurotrophic factors. Choroid plexus epithelial cells were cryopreserved and thawed following primary culture or passage cultured for up to two passages. The supernatant of primary, first/second passage and cryopreserved-thawed choroid plexus epithelial cells was collected when cells reached 80-90% confluence. ELISA was used to quantify brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF), nerve growth factor (NGF) and ciliary neurotrophic factor (CNTF) levels in the cell supernatant. First passage and cryopreserved-thawed cells secreted less BDNF and CNTF compared with primary cultured cells and increased levels of these two factors compared with second passage cells, and increased levels of GDNF and NGF compared with primary cultured and second passage cells (all P<0.05). Therefore, first passage culture decreased BDNF and CNTF secretion but increased NGF and GDNF compared with primary culture; second passage culture diminished neurotrophic factor secretion compared with first passage culture; and cryopreservation did not weaken the function of choroid plexus epithelial cells in secreting BDNF, GDNF, NGF and CNTF. The current study demonstrates that first passage and cryopreserved-thawed choroid plexus epithelial cells have an enhanced function to secrete neurotrophic factors including BDNF, GDNF, NGF and CNTF.

Pramlintide: The Effects of a Single Drug Injection on Blood Phosphatidylcholine Profile for Alzheimer's Disease

Studies suggest that a single injection of pramlintide, an amylin analog, induces changes in Alzheimer's disease (AD) biomarkers in the blood of AD mouse models and AD patients. The aim of this study was to examine whether a pramlintide challenge combined with a phosphatidylcholine (PC) profile diagnoses of AD and mild cognitive impairment (MCI) better than PC alone. Non-diabetic subjects with cognitive status were administered a single subcutaneous injection of 60 mcg of pramlintide under fasting condition. A total of 71 PCs, amyloid-β peptide (Aβ), and total tau (t-tau) in plasma at different time points were measured and treated as individual variables. A single injection of pramlintide altered the levels of 7 PCs in the blood, while a pramlintide injection plus food modulated the levels of 10 PCs in the blood (p < 0.05). The levels of 2 PCs in MCI and 12 PCs in AD in the pramlintide challenge were significantly lower than the ones in controls. We found that while some PCs were associated with only Aβ levels, other PCs were associated with both Aβ and t-tau levels. A receiver operating characteristic analysis of the PCs was combined with the Aβ and t-tau data to produce an area under the curve predictive value of 0.9799 between MCI subjects and controls, 0.9794 between AD subjects and controls, and 0.9490 between AD and MCI subjects. A combination of AD biomarkers and a group of PCs post a pramlintide challenge may provide a valuable diagnostic and prognostic test for AD and MCI.

Transplants of Encapsulated Rat Choroid Plexus Cells Exert Neuroprotection in a Rodent Model of Huntington's Disease

Choroid plexus (CP) epithelial cells secrete several neurotrophic factors and have been used in transplantation studies designed to impart neuroprotection against central nervous system (CNS) trauma. In the present study, CP was isolated from adult rats, encapsulated within alginate microcapsules, and transplanted unilaterally into the rat striatum. Three days later, unilateral injections of quinolinic acid (QA; 225 nmol) were made into the ipsilateral striatum to mimic the pathology observed in Huntington's disease (HD). After surgery, animals were tested for motor function using the placement test. Rats receiving CP transplants were significantly less impaired on this test. Nissl-stained sections demonstrated that CP transplants significantly reduced the volume of the striatal lesion produced by QA. Quantitative analysis of striatal neurons further demonstrated that choline acetyltransferase-immunoreactive, but not diaphorase-positive, neurons were protected by CP transplants. These data demonstrate that transplanted CP cells can be used to protect striatal neurons from excitotoxic damage and that the pattern of neuroprotection varies across specific neuronal populations.

A Role of the Choroid Plexus in Transplantation Therapy

The choroid plexuses (CPs) play pivotal roles in the most basic aspects of neural function. Some of the roles of the CP include maintaining the extracellular milieu of the brain by actively modulating chemical exchange between the CSF and brain parenchyma, surveying the chemical and immunological status of the brain, detoxifying the brain, secreting a nutritive “cocktail” of polypeptides, and participating in repair processes following trauma. This diversity of functions suggests that even modest changes in the CP can have far reaching effects. Indeed, changes in the anatomy and physiology of the CP have been linked to several CNS diseases. It is also possible that replacing diseased CP or transplanting healthy CP might be useful for treating acute and chronic brain diseases. Here we describe the wide-ranging functions of the CP, alterations of these functions in aging and neurodegeneration, and recent demonstrations of the therapeutic potential of transplanted CP for neural trauma.

In Vitro Culture Duration does Not Impact the Ability of Encapsulated Choroid Plexus Transplants to Prevent Neurological Deficits in an Excitotoxin-Lesioned Rat Model of Huntington's Disease

Delivery of neurotrophic molecules to the CNS is a potential treatment strategy for preventing the neuronal loss accompanying many neurological disorders. Choroid plexus (CP) epithelial cells secrete a cocktail of neurotrophic factors, and encapsulated CP transplants are neuroprotective in animal models of stroke and Huntington's disease (HD). Prior to clinical use, it is essential to identify and optimize parameters such as the length of time that transplant products such as encapsulated CP can be maintained. In the present study, neonatal porcine CP was encapsulated within alginate microcapsules and maintained in vitro for 1, 2, or 7 months. The encapsulated cells remained viable (>80%) at all time points and were transplanted unilaterally into the rat striatum. Seven days later, the same animals received unilateral injections of quinolinic acid (QA; 225 nmol) adjacent to the implant site. Separate groups of animals served as controls and received QA alone. After surgery, animals were periodically evaluated for weight loss and were tested for motor function 14 days post-QA. In controls, QA lesions produced a significant loss of body weight and impaired function of the contralateral forelimb. In contrast, implants of CP were potently neuroprotective as rats receiving CP transplants did not lose body weight and were not significantly impaired when tested for motor function. These benefits were independent of the length of time that the cells were held in vitro and demonstrate that the potential potency of alginate encapsulated CP cells can be retained for extremely long periods of time in vitro.

In Vitro Exposure of Cultured Porcine Choroid Plexus Epithelial Cells to Immunosuppressant, Anti-Inflammatory, and Psychoactive Drugs

Delivery of neurotrophic molecules to the CNS is a potential treatment for preventing the neuronal loss in neurological disorders such as Huntington's disease (HD). Choroid plexus (CP) epithelial cell transplants secrete several neurotrophic factors and are neuroprotective in rat and monkey animal models of HD. HD patients receiving CP transplants would likely receive a course of immunosuppressant/anti-inflammatory treatment postsurgery and would remain on psychoactive medications to treat their motor, psychiatric, and emotional symptoms. Therefore, we examined whether CP epithelial cells are impacted by incubation with cyclosporine A (CsA), dexmethasone, haloperidol, fluoxetine, and carbamezapine. In each case, DNA was quantified to determine cell number, a formazen dye-based assay was used to quantify cell metabolism, and vascular endothelial growth factor (VEGF) levels were measured as a marker of protein secretion. Except for the highest dose of fluoxetine, none of the drugs tested exerted any detrimental effect on cell number. Incubation with CsA or dexamethasone did not have any consistent significant effect on VEGF secretion or cell metabolism. Carbamazepine was without effect while only the highest dose of haloperidol tested modestly lowered cell metabolism. VEGF secretion and cell metabolism was not measurable from CP cells exposed to 100 μM fluoxetine. These data continue to support the potential use of CP transplants in HD.

An amylin analog used as a challenge test for Alzheimer's disease

INTRODUCTION

Preclinical studies demonstrate the potential of amylin in the diagnosis of Alzheimer's disease (AD). We aimed to lay the foundation for repurposing the amylin analog and a diabetes drug, pramlintide, for AD in humans.

METHODS

We administered a single subcutaneous injection of 60 μg of pramlintide to nondiabetic subjects under fasting conditions.

RESULTS

None of the participants developed hypoglycemia after the injection of pramlintide. The pramlintide challenge induced a significant surge of amyloid-β peptide and a decrease in total tau in the plasma of AD subjects but not in control participants. The pramlintide injection provoked an increase in interleukin 1 receptor antagonist and a decrease in retinol-binding protein 4, which separates AD subjects from control subjects.

DISCUSSION

Pramlintide use appeared to be safe in the absence of diabetes. The biomarker changes as a result of the pramlintide challenge, which distinguished AD from control subjects and mild cognitive impairment.

Amyotrophic lateral sclerosis: Is the spinal fluid pathway involved in seeding and spread?

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder manifested primarily by loss of upper and lower motor neurons. Current explanations for disease progression invoke regional spread attributed to the transfer of pathogenic factors among physically contiguous neurons. However, this explanation incompletely explains certain clinical and in vitro data. Considering this, we propose that the cerebrospinal fluid (CSF) pathway is likely to be a key vector for seeding local and distal disease. Subsequent disease progression would be expected to occur independently via either axonal or CSF transmission. If one accepts the hypothesis that the CSF pathway is involved in ALS progression, it follows that the choroid plexus (CP) might well be a driver of the disease process. In support of this, we briefly review the anatomical and physiological features of the CSF pathway and the choroid plexus responsible for secreting CSF. In addition, we draw attention to the interface of the CP and CSF with the immune system. We then summarize both clinical and cell culture research that supports a key role of the CSF in the establishment and inter-neuronal spread of ALS, and which suggest directions for translational research.

Anatomical, molecular and pathological consideration of the circumventricular organs

BACKGROUND AND PURPOSE

Circumventricular organs (CVOs) are a diverse group of specialised structures characterized by peculiar vascular and position around the third and fourth ventricles of the brain. In humans, these organs are present during the fetal period and some become vestigial after birth. Some, such as the pineal gland (PG), subcommissural organ (SCO) and organum vasculosum of the lamina terminalis (OVLT), which are located around the third ventricle, might be the site of origin of periventricular tumours. In contrast to humans, CVOs are present in the adult rat and can be dissected by laser capture microdissection (LCM).

METHODS

In this study, we used LCM and microarrays to analyse the transcriptomes of three CVOs, the SCO, the subfornical organ (SFO) and the PG and the third ventricle ependyma of the adult rat, in order to better characterise these organs at the molecular level. Furthermore, an immunohistochemical study of Claudin-3 (CLDN3), a membrane protein involved in forming cellular tight junctions, was performed at the level of the SCO.

RESULTS

This study highlighted some potentially new or already described specific markers of these structures as Erbb2 and Col11a1 in ependyma, Epcam and CLDN3 in the SCO, Ren1 and Slc22a3 in the SFO and Tph, Anat and Asmt in the PG. Moreover, we found that CLDN3 expression was restricted to the apical pole of ependymocytes in the SCO.

Transcriptome profiling of a multiple recurrent muscle-invasive urothelial carcinoma of the bladder by deep sequencing

Urothelial carcinoma of the bladder (UCB) is one of the commonly diagnosed cancers in the world. The UCB has the highest rate of recurrence of any malignancy. A genome-wide screening of transcriptome dysregulation between cancer and normal tissue would provide insight into the molecular basis of UCB recurrence and is a key step to discovering biomarkers for diagnosis and therapeutic targets. Compared with microarray technology, which is commonly used to identify expression level changes, the recently developed RNA-seq technique has the ability to detect other abnormal regulations in the cancer transcriptome, such as alternative splicing. In this study, we performed high-throughput transcriptome sequencing at ∼50× coverage on a recurrent muscle-invasive cisplatin-resistance UCB tissue and the adjacent non-tumor tissue. The results revealed cancer-specific differentially expressed genes between the tumor and non-tumor tissue enriched in the cell adhesion molecules, focal adhesion and ECM-receptor interaction pathway. Five dysregulated genes, including CDH1, VEGFA, PTPRF, CLDN7, and MMP2 were confirmed by Real time qPCR in the sequencing samples and the additional eleven samples. Our data revealed that more than three hundred genes showed differential splicing patterns between tumor tissue and non-tumor tissue. Among these genes, we filtered 24 cancer-associated alternative splicing genes with differential exon usage. The findings from RNA-Seq were validated by Real time qPCR for CD44, PDGFA, NUMB, and LPHN2. This study provides a comprehensive survey of the UCB transcriptome, which provides better insight into the complexity of regulatory changes during recurrence and metastasis.

Conditioned media of choroid plexus epithelial cells induces Nrf2-activated phase II antioxidant response proteins and suppresses oxidative stress-induced apoptosis in PC12 cells

Based on the critical role of the choroid plexus (CP) in detoxification processes in the central nervous system (CNS), herein we investigated the effect of choroid plexus epithelial cells conditioned media (CPECs-CM) under oxidative conditions. CPECs were isolated from rat brains, cultured, and the conditioned media were collected. Then pheochromocytoma neuron-like cells (PC12) were treated simultaneously with CPECs-CM and H2O2 as the oxidative stressor. Next, the effect of CPECs-CM on neurite outgrowth and cell differentiation in the presence of H2O2 was determined. Our results showed that CPECs-CM improved the expansion of neurites and differentiation in PC12 cells under oxidative stress conditions. Changes in apoptotic factors, nuclear factor erythroid 2-related factor 2 (Nrf2) and γ-glutamylcysteine synthetase as the highlighted pathway in the antioxidant defense system were determined by western blot. Also, the activity of antioxidant enzymes and lipid peroxidation level were determined. CPECs-CM-treated PC12 cells could survive after exposure to H2O2 by reduction of caspase-3 cleavage and Bax level and elevation of anti-apoptotic factor Bcl2. Our data also revealed that Nrf2 activation, and consequently its downstream protein levels, increased in the presence of CPECs-CM. Based on our data, we can conclude that CPECs-CM protects PC12 cells against oxidative stress and apoptosis. It seems that CPECs secrete antioxidative agents and neurotrophic factors that have a role in the health of the CNS.

Primary culture of choroid plexuses from neonate rats containing progenitor cells capable of differentiation

BACKGROUND

The choroid plexuses, which could secrete a number of neurotrophins, have recently been used in transplantation in central nervous system diseases.

AIMS

To study the mechanism of nerve regeneration in the central nervous system by grafting choroid plexus tissues.

STUDY DESIGN

Animal experimentation.

METHODS

The choroid plexuses from the lateral ventricles of neonatal rats were cultured in adherent culture, and immunocytochemical methods were used to analyse the progenitor cells on days 2, 6, and 10 after seeding.

RESULTS

Expression of both nestin and glial fibrillary acidic protein was observed in small cell aggregates on day 2 in primary culture. Most of the nestin-positive cells on day 6 were immunoreactive to glial fibrillary acidic protein antibody. No cells expressing nestin or glial fibrillary acidic protein were seen on day 10.

CONCLUSION

These experimental results indicate that the choroid plexus contains a specific cell population - progenitor cells. Under in vitro experimental conditions, the progenitor cells differentiated into choroid plexus epithelial cells but did not form neurons or astrocytes.

Riding the wave of ependymal cilia: genetic susceptibility to hydrocephalus in primary ciliary dyskinesia

Congenital hydrocephalus is a relatively common and debilitating birth defect with several known physiological causes. Dysfunction of motile cilia on the ependymal cells that line the ventricular surface of the brain can result in hydrocephalus by hindering the proper flow of cerebrospinal fluid. As a result, hydrocephalus can be associated with primary ciliary dyskinesia, a rare pediatric syndrome resulting from defects in ciliary and flagellar motility. Although the prevalence of hydrocephalus in primary ciliary dyskinesia patients is low, it is a common hallmark of the disease in mouse models, suggesting that distinct genetic mechanisms underlie the differences in the development and physiology of human and mouse brains. Mouse models of primary ciliary dyskinesia reveal strain-specific differences in the appearance and severity of hydrocephalus, indicating the presence of genetic modifiers segregating in inbred strains. These models may provide valuable insight into the genetic mechanisms that regulate susceptibility to hydrocephalus under the conditions of ependymal ciliary dysfunction.

Protective effects of isothiocyanates on blood-CSF barrier disruption induced by oxidative stress

The choroid plexuses (CPs) form the blood-cerebrospinal fluid (CSF) barrier (BCSFB) and play an important role in maintaining brain normal function and the brain response to injury. Many neurological disorders are associated with oxidative stress that can impact CP function. This study examined the effects of isothiocyanates, an abundant component in cruciferous vegetables, on H(2)O(2)-induced BCSFB disruption and CP cell death in vitro. It further examined the potential role of a transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2), in isothiocyanate-induced protection. Sulforaphane (SF) significantly reduced H(2)O(2)-induced BCSFB disruption as assessed by transepithelial electrical resistance (29 ± 7% reduction vs. 92 ± 2% decrease in controls) and [(3)H]mannitol permeability. Allyl-isothiocyanate (AITC) had a similar protective effect. H(2)O(2)-induced epithelial cell death was also reduced by these isothiocyanates. In primary CP cells, SF and AITC reduced cell death by 42 ± 3% and 53 ± 10%, respectively. Similar protection was found in a CP cell line Z310. Protection was only found with pretreatment for 12-48 h and not with acute exposure (1 h). The protective effects of SF and AITC were associated with Nrf2 nuclear translocation and upregulated expression of antioxidative systems regulated by Nrf2, including heme oxygenase-1, NAD(P)H quinine oxidoreductase, and cysteine/glutamate exchange transporter. Thus isothiocyanates, as diet or medicine, may be a method for protecting BCSFB in neurological disorders.

Pathological alteration in the choroid plexus of Alzheimer's disease: implication for new therapy approaches

Morphological alterations of choroid plexus in Alzheimer’s disease (AD) have been extensively investigated. These changes include epithelial atrophy, thickening of the basement membrane, and stroma fibrosis. As a result, synthesis, secretory, and transportation functions are significantly altered resulting in decreased cerebrospinal fluid (CSF) turnover. Recent studies discuss the potential impacts of these changes, including the possibility of reduced resistance to stress insults and slow clearance of toxic compounds from CSF with specific reference to the amyloid peptide. Here, we review new evidences for AD-related changes in the choroid plexus. The data suggest that the significantly altered functions of the choroid plexus contribute to the multiparametric pathogenesis of late-onset AD.

Combining cell-based therapies and neural prostheses to promote neural survival

Cochlear implants provide partial restoration of hearing for profoundly deaf patients by electrically stimulating spiral ganglion neurons (SGNs); however, these neurons gradually degenerate following the onset of deafness. Although the exogenous application of neurotrophins (NTs) can prevent SGN loss, current techniques to administer NTs for long periods of time have limited clinical applicability. We have used encapsulated choroid plexus cells (NTCells; Living Cell Technologies, Auckland, New Zealand) to provide NTs in a clinically viable manner that can be combined with a cochlear implant. Neonatal cats were deafened and unilaterally implanted with NTCells and a cochlear implant. Animals received chronic electrical stimulation (ES) alone, NTs alone, or combined NTs and ES (ES + NT) for a period of as much as 8 months. The opposite ear served as a deafened unimplanted control. Chronic ES alone did not result in increased survival of SGNs or their peripheral processes. NT treatment alone resulted in greater SGN survival restricted to the upper basal cochlear region and an increased density of SGN peripheral processes. Importantly, chronic ES in combination with NTs provided significant SGN survival throughout a wider extent of the cochlea, in addition to an increased peripheral process density. Re-sprouting peripheral processes were observed in the scala media and scala tympani, raising the possibility of direct contact between peripheral processes and a cochlear implant electrode array. We conclude that cell-based therapy is clinically viable and effective in promoting SGN survival for extended durations of cochlear implant use. These findings have important implications for the safe delivery of therapeutic drugs to the cochlea.

Targeting the choroid plexus-CSF-brain nexus using peptides identified by phage display

Drug delivery to the central nervous system requires the use of specific portals to enable drug entry into the brain and, as such, there is a growing need to identify processes that can enable drug transfer across both blood-brain and blood-cerebrospinal fluid barriers. Phage display is a powerful combinatorial technique that identifies specific peptides that can confer new activities to inactive particles. Identification of these peptides is directly dependent on the specific screening strategies used for their selection and retrieval. This chapter describes three selection strategies, which can be used to identify peptides that target the choroid plexus (CP) directly or for drug translocation across the CP and into cerebrospinal fluid.

Brain abnormalities and glioma-like lesions in mice overexpressing the long isoform of PDGF-A in astrocytic cells

Background

Deregulation of platelet-derived growth factor (PDGF) signaling is a hallmark of malignant glioma. Two alternatively spliced PDGF-A mRNAs have been described, corresponding to a long (L) and a short (S) isoform of PDGF-A. In contrast to PDGF-A(S), the PDGF-A(L) isoform has a lysine and arginine rich carboxy-terminal extension that acts as an extracellular matrix retention motif. However, the exact role of PDGF-A(L) and how it functionally differs from the shorter isoform is not well understood.

Methodology/Principal Findings

We overexpressed PDGF-A(L) as a transgene under control of the glial fibrillary acidic protein (GFAP) promoter in the mouse brain. This directs expression of the transgene to astrocytic cells and GFAP expressing neural stem cells throughout the developing and adult central nervous system. Transgenic mice exhibited a phenotype with enlarged skull at approximately 6-16 weeks of age and they died between 1.5 months and 2 years of age. We detected an increased number of undifferentiated cells in all areas of transgene expression, such as in the subependymal zone around the lateral ventricle and in the cerebellar medulla. The cells stained positive for Pdgfr-α, Olig2 and NG2 but this population did only partially overlap with cells positive for Gfap and the transgene reporter. Interestingly, a few mice presented with overt neoplastic glioma-like lesions composed of both Olig2 and Gfap positive cell populations and with microvascular proliferation, in a wild-type p53 background.

Conclusions

Our findings show that PDGF-A(L) can induce accumulation of immature cells in the mouse brain. The strong expression of NG2, Pdgfr-α and Olig2 in PDGF-A(L) brains suggests that a fraction of these cells are oligodendrocyte progenitors. In addition, accumulation of fluid in the subarachnoid space and skull enlargement indicate that an increased intracranial pressure contributed to the observed lethality.

Use of Encapsulated Stem Cells to Overcome the Bottleneck of Cell Availability for Cell Therapy Approaches

Nowadays cell-based therapy is rarely in clinical practice because of the limited availability of appropriate cells. To apply cells therapeutically, they must not cause any immune response wherefore mainly autologous cells have been used up to now. The amount of vital cells in patients is limited, and under certain circumstances in highly degenerated tissues no vital cells are left. Moreover, the extraction of these cells is connected with additional surgery; also the expansion in vitro is difficult. Other approaches avoid these problems by using allo-or even xenogenic cells. These cells are more stable concerning their therapeutic behavior and can be produced in stock. To prevent an immune response caused by these cells, cell encapsulation (e.g. with alginate) can be performed. Certain studies showed that encapsulated allo- and xenogenic cells achieve promising results in treatment of several diseases. For such cell therapy approaches, stem cells, particularly mesenchymal stem cells, are an interesting cell source. This review deals on the one hand with the use of encapsulated cells, especially stem cells, in cell therapy and on the other hand with bioreactor systems for the expansion and differentiation of mesenchymal stem cells in reproducible and sufficient amounts for potential clinical use.

Microencapsulated choroid plexus epithelial cell transplants for repair of the brain

The choroid plexuses (CPs) play pivotal roles in basic aspects of neural function including maintaining the extracellular milieu of the brain by actively modulating chemical exchange between the CSF and brain parenchyma, surveying the chemical and immunological status of the brain, detoxifying the brain, secreting a nutritive "cocktail" of polypeptides and participating in repair processes following trauma. Even modest changes in the CP can have far reaching effects and changes in the anatomy and physiology of the CP have been linked to several CNS diseases. It is also possible that replacing diseased or transplanting healthy CP might be useful for treating acute and chronic brain diseases. Here we describe the wide-ranging functions of the CP, alterations of these functions in aging and neurodegeneration and recent demonstrations of the therapeutic potential of transplanted microencapsulated CP for neural trauma.

Secreted Products from the Porcine Choroid Plexus Accelerate the Healing of Cutaneous Wounds

The choroid plexus (CP), located at the blood–brain interface, is partially responsible for maintaining the composition of cerebrospinal fluid. Epithelial cell clusters isolated from the CP secrete numerous biologically active molecules, and are neuroprotective when transplanted in animal models of Huntington's disease and stroke. The transcriptomic and proteomic profiles of CP may extend beyond CNS applications due to an abundance of trophic and regenerative factors, including vascular endothelial growth factor, transforming growth factor-β, and others. We used microarray to investigate the transcriptome of porcine CP epithelium, and then assessed the in vitro and in vivo regenerative capability of secreted CP products in cell monolayers and full-thickness cutaneous wounds. In vitro, CP reduced the void area of fibroblast and keratinocyte scratch cultures by 70% and 33%, respectively, compared to empty capsule controls, which reduced the area by only 35% and 6%, respectively. In vivo, after 10 days of topical application, CP conditioned medium lyophilate dispersed in antibiotic ointment produced a twofold improvement in incision tensile strength compared to ointment containing lyophilized control medium, and an increase in the regeneration of epidermal appendages from roughly 50–150 features per wound. Together, these data identify the CP as a source of secreted regenerative molecules to accelerate and improve the healing of superficial wounds and potentially other similar indications.

Encapsulated living choroid plexus cells: potential long-term treatments for central nervous system disease and trauma

In neurodegenerative disease and in acute brain injury, there is often local up-regulation of neurotrophin production close to the site of the lesion. Treatment by direct injection of neurotrophins and growth factors close to these lesion sites has repeatedly been demonstrated to improve recovery. It has therefore been proposed that transplanting viable neurotrophin-producing cells close to the trauma lesion, or site of degenerative disease, might provide a novel means for continuous delivery of these molecules directly to the site of injury or to a degenerative region. The aim of this paper is to summarize recent published information and present new experimental data that indicate that long-lasting therapeutic implants of choroid plexus (CP) neuroepithelium may be used to treat brain disease. CP produces and secretes numerous biologically active neurotrophic factors (NT). New gene microarray and proteomics data presented here indicate that many other anti-oxidant, anti-toxin and neuronal support proteins are also produced and secreted by CP cells. In the healthy brain, these circulate in the cerebrospinal fluid through the brain and spinal cord, maintaining neuronal networks and associated cells. Recent publications describe how transplanted CP cells and tissue, either free or in an immunoprotected encapsulated form, can effectively deliver therapeutic molecules when placed near the lesion or site of degenerative disease in animal models. Using simple techniques, CP neuroepithelial cell clusters in suspension culture were very durable, remaining viable for 6 months or more in vitro. The cell culture conditions had little effect on the wide range and activity of genes expressed and proteins secreted. Recently, completed experiments show that implanting CP within alginate-poly-ornithine capsules effectively protected these xenogeneic cells from the host immune system and allowed their survival for 6 months or more in the brains of rats, causing no adverse effects. Previously reported evidence demonstrated that CP cells support the survival and differentiation of neuronal cells in vitro and effectively treat acute brain injury and disease in rodents and non-human primates in vivo. The accumulated preclinical data together with the long-term survival of implanted encapsulated cells in vivo provide a sound base for the investigation of these treatments for chronic inherited and established neurodegenerative conditions.

Treatment of spinal cord injury by transplantation of cells via cerebrospinal fluid

It is very important to probe into the axonal regeneration and functional recovery of central nervous system (CNS) after implantation of cells into cerebrospinal fluid (CSF) for spinal cord injury (SCI). Transplantation of cells via CSF poses great potentials for SCI in clinic. Studies on administration of cells via CSF indicate that the method is safe and convenient. The method is more suitable to treating multiple lesions of the CNS since it does not produce open lesions. However, there are disputes over its promotion effects on axonal regeneration and functional recovery of spinal cord after injury; and some questions, such as the mechanisms of functional recovery of spinal cord, the proper time window of cell transplantation, and cell types of transplantation, still need to be handled. This review summarized the method of cell transplantation via CSF for treatment of SCI.

Potential of choroid plexus epithelial cell grafts for neuroprotection in Huntington's disease: what remains before considering clinical trials

The choroid plexuses (CPs) help maintain the extracellular milieu of the brain by modulating chemical exchange between the cerebrospinal fluid and brain parenchyma, surveying the chemical and immunological status of the brain, detoxifying the brain, secreting a nutritive "cocktail" of polypeptides, and participating in repair processes following trauma. Based on recent pre-clinical studies in animal models, a novel therapeutic approach has been suggested that involves transplanting CP for treating acute and chronic brain diseases. To date most studies have focused on rodent and primate models of Huntington's disease (HD) with demonstrations that transplants of CP can prevent the behavioral and anatomical consequences of striatal degeneration. Despite the encouraging results that lend support to the possibility of protecting vulnerable neurons in HD, critical basic science issues remain unexamined that limit the translation of the pre-clinical findings into clinical evaluations of CP transplants for HD. Here we briefly outline the logic behind using this novel cell source for transplantation, the pre-clinical data supporting this concept, and most importantly identify several critical, gating issues that remain prior to moving this approach forward in a meaningful clinical manner.

Aging reduces the neuroprotective capacity, VEGF secretion, and metabolic activity of rat choroid plexus epithelial cells

Delivery of neurotrophic molecules to the brain has potential for preventing neuronal loss in neurodegenerative disorders. Choroid plexus (CP) epithelial cells secrete numerous neurotrophic factors, and encapsulated CP transplants are neuroprotective in models of stroke and Huntington's disease (HD). To date, all studies examining the neuroprotective potential of CP transplants have used cells isolated from young donor animals. Because the aging process significantly impacts the cytoarchitecture and function of the CP the following studies determined whether age-related impairments occur in its neuroprotective capacity. CP was isolated from either young (3-4 months) or aged (24 months) rats. In vitro, young CP epithelial cells secreted more VEGF and were metabolically more active than aged CP epithelial cells. Additionally, conditioned medium from cultured aged CP was less potent than young CP at enhancing the survival of serum-deprived neurons. Finally, encapsulated CP was tested in an animal model of HD. Cell-loaded or empty alginate capsules (control group) were transplanted unilaterally into the rat striatum. Seven days later, the animals received an injection of quinolinic acid (QA; 225 nmol) adjacent to the implant site. Animals were tested for motor function 28 days later. In the control group, QA lesions severely impaired function of the contralateral forelimb. Implants of young CP were potently neuroprotective as rats receiving CP transplants were not significantly impaired when tested for motor function. In contrast, implants of CP from aged rats were only modestly effective and were much less potent than young CP transplants. These data are the first to directly link aging with diminished neuroprotective capacity of CP epithelial cells.

Vascular endothelial growth factor and nitric oxide production in response to hypoxia in the choroid plexus in neonatal brain

Damage to the choroid plexus in 1-day-old Wistar rats subjected to hypoxia was investigated. The mRNA and protein expression of hypoxia-inducible factor-1alpha (HIF-1alpha), endothelial, neuronal, inducible nitric oxide synthase (eNOS, nNOS, iNOS), and vascular endothelial growth factor (VEGF) along with nitric oxide (NO) production and VEGF concentration was up-regulated significantly in hypoxic rats. Ultrastructurally, the choroid plexus epithelial cells showed massive accumulation of glycogen. A striking feature was the extrusion of cytoplasmic fragments from the apical cell surfaces into the ventricular lumen following the hypoxic insult. Intraventricular macrophages showed increased expression of complement type 3 receptors, major histocompatibility complex class I and II antigens, and ED1 antigens. Following an intravenous injection of horseradish peroxidase (HRP), a large number of intraventricular macrophages were labeled suggesting enhanced leakage of the tracer from the blood vessels in the choroid plexus connective tissue stroma into the ventricular lumen. We suggest that increased production of NO in hypoxia is linked to the structural alteration of the choroid plexus, and along with VEGF, may lead to increased vascular permeability. Melatonin treatment reduced VEGF and NO levels as well as leakage of HRP suggesting its potential value in ameliorating damage in choroid plexus pathologies.

Windows of the brain: Towards a developmental biology of circumventricular and other neurohemal organs

We review the anatomical and functional features of circumventricular organs in vertebrates and their homologous neurohemal organs in invertebrates. Focusing on cyclostomes (lamprey) and urochordates (ascidians), we discuss the evolutionary origin of these organs as a function of their cell type specification and morphogenesis.

TheIn VitroExpression and Secretion of Vascular Endothelial Growth Factor from Free and Alginate-Polyornithine Encapsulated Choroid Plexus Epithelium

The choroid plexus (CP) is a transplantable cell source secreting tropic and trophic factors for the treatment of brain and peripheral trauma characterized by cellular loss or dysfunction. Here we characterize the expression and secretion of vascular endothelial growth factor (VEGF) from neonatal porcine CP. Light and electron microscopy revealed that enzymatic digestion of the CP produced a preparation consisting primarily of epithelial cells without notable contaminating cells. Microarray analysis, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay were used to quantify the nuclear, cytoplasmic, and secretory compartmentalization of VEGF. In vitro, the kinetics of VEGF release were orderly, with stepwise increases in secretion over time. The secretory profile of VEGF from CP grown in configurations ranging from a simple monolayer to free-floating 3-dimensional clusters to clusters encapsulated within alginate-polyornithine microcapsules was similar. VEGF output was not affected notably when the cells were maintained in 90% stress medium or in other maintenance media devoid of serum proteins. Secreted VEGF was bioactive, as confirmed by demonstrating its continued ability to proliferate co-cultured human umbilical vascular endothelial cells. The robust ability of these cells to continue to secrete VEGF (and presumably other bioactive proteins) across a variety of dimensional configurations and medium types has implications for their use in clinical indications requiring novel and imaginative use of engineered ectopic transplant sites.

Membrane transporter proteins: a challenge for CNS drug development

Drug transporters are membrane proteins present in various tissues such as the lymphocytes, intestine, liver, kidney, testis, placenta, and central nervous system. These transporters play a significant role in drug absorption and distribution to organic systems, particularly if the organs are protected by blood-organ barriers, such as the blood-brain barrier or the maternal-fetal barrier. In contrast to neurotransmitters and receptor-coupled transporters or other modes of interneuronal transmission, drug transporters are not directly involved in specific neuronal functions, but provide global protection to the central nervous system. The lack of capillary fenestration, the low pinocytic activity, and the tight junctions between brain capillary and choroid plexus endothelial cells represent further gatekeepers limiting the entrance of endogenous and exogenous compounds into the central nervous system. Drug transport is a result of the concerted action of efflux and influx pumps (transporters) located both in the basolateral and apical membranes of brain capillary and choroid plexus endothelial cells. By regulating efflux and influx of endogenous or exogenous substances, the blood-brain barrier and, to a lesser extent, the blood-cerebrospinal barrier in the ventricles, represents the main interface between the central nervous system and the blood, ie, the rest of the body. As drug distribution to organs is dependent on the affinity of a substrate for a specific transport system, membrane transporter proteins are increasingly recognized as a key determinant of drug disposition. Many drug transporters are members of the adenosine triphosphate (ATP)-binding cassette (ABC) transporter superfamily or the solute-linked carrier (SLC) class. The multidrug resistance protein MDR1 (ABCB1), also called P-glycoprotein, the multidrug resistance-associated proteins MRP1 (ABCC1) and MRP2 (ABCC2), and the breast cancer-resistance protein BCRP (ABCG2) are ATP-dependent efflux transporters expressed in the blood-brain barrier. They belong to the superfamily of ABC transporters, which export drugs from the intracellular to the extracellular milieu. Members of the SLC class of solute carriers include, for example, organic ion transporting peptides, organic cation transporters, and organic ion transporters. They are ATP-independent polypeptides principally expressed at the basolateral membrane of brain capillary and choroid plexus endothelial cells that also mediate drug transport through central nervous system barriers.

Extensive neuroprotection by choroid plexus transplants in excitotoxin lesioned monkeys

Huntington's disease (HD) results from degeneration of striatal neurons. Choroid plexus (CP) cells secrete neurotrophic factors, and CP transplants are neuroprotective in rat models of HD. To determine if similar neuroprotective effects could be obtained in primates, porcine CP was encapsulated in alginate capsules. PCR confirmed that the CP cells expressed transthyretin and immunocytochemistry demonstrated typical ZO-1 and tubulin staining. In vitro, CP conditioned media enhanced the survival and preserved neurite number and length on serum deprived neurons. Cynomolgus primates were transplanted with CP-loaded capsules into the caudate and putamen followed by quinolinic acid (QA) lesions 1 week later. Control monkeys received empty capsules plus QA. Choroid plexus transplants significantly protected striatal neurons as revealed by stereological counts of NeuN-positive neurons (8% loss vs. 43% in controls) and striatum volume (10% decrease vs. 40% in controls). These data indicate that CP transplants might be useful for preventing the degeneration of neurons in HD.

Choroid plexus transplants in the treatment of brain diseases

The choroid plexus (CP) produces and secretes numerous biologically active neurotrophic factors into the cerebrospinal fluid (CSF). These circulate throughout the brain and spinal cord, maintaining neuronal networks and associated cells. In neurodegenerative disease and in acute brain injury there is local up-regulation of neurotrophin production close to the site of the lesion. Treatment by direct injection of neurotrophins and growth factors close to these lesion sites has repeatedly been demonstrated to improve recovery. It has therefore been proposed that transplanting viable choroid plexus cells close to the lesion might provide a novel means for continuous delivery of these molecules directly to the site of injury. Recent publications describe how transplanted CP, either free or in an immunoprotected encapsulated form, deliver therapeutic molecules to the desired site. This review briefly describes the accumulated evidence that CP cells support neuronal cells in vitro and have therapeutic properties when transplanted to treat acute and chronic brain disease and injury in animal models.

Enhanced Prospects for Drug Delivery and Brain Targeting by the Choroid Plexus–CSF Route

The choroid plexus (CP), i.e., the blood-cerebrospinal fluid barrier (BCSFB) interface, is an epithelial boundary exploitable for drug delivery to brain. Agents transported from blood to lateral ventricles are convected by CSF volume transmission (bulk flow) to many periventricular targets. These include the caudate, hippocampus, specialized circumventricular organs, hypothalamus, and the downstream pia-glia and arachnoid membranes. The CSF circulatory system normally provides micronutrients, neurotrophins, hormones, neuropeptides, and growth factors extensively to neuronal networks. Therefore, drugs directed to CSF can modulate a variety of endocrine, immunologic, and behavioral phenomema; and can help to restore brain interstitial and cellular homeostasis disrupted by disease and trauma. This review integrates information from animal models that demonstrates marked physiologic effects of substances introduced into the ventricular system. It also recapitulates how pharmacologic agents administered into the CSF system prevent disease or enhance the brain's ability to recover from chemical and physical insults. In regard to drug distribution in the CNS, the BCSFB interaction with the blood-brain barrier is discussed. With a view toward translational CSF pharmacotherapy, there are several promising innovations in progress: bone marrow cell infusions, CP encapsulation and transplants, neural stem cell augmentation, phage display of peptide ligands for CP epithelium, CSF gene transfer, regulation of leukocyte and cytokine trafficking at the BCSFB, and the purification of neurotoxic CSF in degenerative states. The progressively increasing pharmacological significance of the CP-CSF nexus is analyzed in light of treating AIDS, multiple sclerosis, stroke, hydrocephalus, and Alzheimer's disease.

The choroid plexus in the rise, fall and repair of the brain

The choroid plexuses (CPs) are involved in the most-basic aspects of neural function including maintaining the extracellular milieu of the brain by actively modulating chemical exchange between the CSF and brain parenchyma, surveying the chemical and immunological status of the brain, detoxifying the brain, secreting a nutritive "cocktail" of polypeptides and participating in repair processes following trauma. This diversity of functions may mean that even modest changes in the CP can have far-reaching effects. Indeed, changes in the anatomy and physiology of the CP have been linked to aging and several CNS diseases. It is also possible that replacing diseased or transplanting healthy CP might be useful for treating acute and chronic brain diseases. This review focuses on the wide-ranging and under-appreciated functions of the CP, alterations of these functions in aging and neurodegeneration, and recent demonstrations of the therapeutic potential of transplanted CP for neural trauma.