CRISPR/Cas gene editing in the human germline.

The ease and efficacy of CRISPR/Cas9 germline gene editing in animal models paved the way to human germline gene editing (HGGE), by which permanent changes can be introduced into the embryo. Distinct genes can be knocked out to examine their function during embryonic development. Alternatively, specific sequences can be introduced which can be applied to correct disease-causing mutations. To date, it has been shown that the success of HGGE is dependent on various experimental parameters and that various hurdles (i.e. loss-of-heterozygosity and mosaicism) need to be overcome before clinical applications should be considered. Due to the shortage of human germline material and the ethical constraints concerning HGGE, alternative models such as stem cells have been evaluated as well, in terms of their predictive value on the genetic outcome for HGGE approaches. This review will give an overview of the state of the art of HGGE in oocytes and embryos, and its accompanying challenges.

Development and feasibility of a telemedicine tool for patients with recurrent urinary tract infection: myRUTIcoach.

INTRODUCTION AND HYPOTHESIS: Patients with recurrent urinary tract infection (rUTI) have limited knowledge of preventive strategies to lower the risk of UTI. We aimed to develop and test the feasibility of an eHealth system for women with rUTI, named myRUTIcoach, and explored the facilitators and barriers related to its adoption. METHODS: We developed myRUTIcoach in a structured iterative process and tested its feasibility among 25 women with rUTI over 2 months. Subsequent questionnaires covered satisfaction, accessibility, and experiences with myRUTIcoach. A random selection of participants and relevant stakeholders took part in semi-structured interviews to explore adoption. Data were analyzed and elaborated using inductive and deductive approaches using the Non-adoption, Abandonment, Spread, Scale-up, and Sustainability (NASSS) framework. RESULTS: MyRUTIcoach was not only widely accepted but also facilitated communication with health care professionals (HCPs) and contributed to greater knowledge of rUTI. Women graded the system a mean of 8.0 (±0.6) out of 10, with 89% stating that they would recommend it to others. Patients indicated that self-management skills were the major facilitators and barriers related to adoption, whereas HCPs stated that the disconnect between myRUTIcoach and electronic health care records (EHRs) was the major barrier. CONCLUSIONS: This research describes the development and testing of myRUTIcoach for women with rUTI. Patients and HCPs reported high satisfaction and compliance with myRUTIcoach. However, adoption by the intended users is complex and influenced by all examined domains of the NASSS framework. We have already improved linkage to EHRs, but further optimization to meet patient needs may improve the effectiveness of this self-management tool for rUTI.

GENType: all-in-one preimplantation genetic testing by pedigree haplotyping and copy number profiling suitable for third-party reproduction.

STUDY QUESTION: Is it possible to develop a comprehensive pipeline for all-in-one preimplantation genetic testing (PGT), also suitable for parents-only haplotyping and, for the first time, third-party reproduction? SUMMARY ANSWER: Optimized reduced representation sequencing (RRS) by GENType, along with a novel analysis platform (Hopla), enables cheap, accurate and comprehensive PGT of blastocysts, even without the inclusion of additional family members or both biological parents for genome-wide embryo haplotyping. WHAT IS KNOWN ALREADY: Several haplotyping strategies have proven to be effective for comprehensive PGT. However, these methods often rely on microarray technology, whole-genome sequencing (WGS) or a combination of strategies, hindering sample throughput and cost-efficiency. Moreover, existing tools (including other RRS-based strategies) require both prospective biological parents for embryo haplotyping, impeding application in a third-party reproduction setting. STUDY DESIGN, SIZE, DURATION: This study included a total of 257 samples. Preliminary technical validation was performed on 81 samples handpicked from commercially available cell lines. Subsequently, a clinical validation was performed on a total of 72 trophectoderm biopsies from 24 blastocysts, tested for a monogenic disorder (PGT-M) (n = 15) and/or (sub)chromosomal aneuploidy (PGT-SR/PGT-A) (n = 9). Once validated, our pipeline was implemented in a diagnostic setting on 104 blastocysts for comprehensive PGT. PARTICIPANTS/MATERIALS, SETTING, METHODS: Samples were whole-genome amplified (WGA) and processed by GENType. Quality metrics, genome-wide haplotypes, b-allele frequencies (BAFs) and copy number profiles were generated by Hopla. PGT-M results were deduced from relative haplotypes, while PGT-SR/PGT-A results were inferred from read-count analysis and BAF profiles. Parents-only haplotyping was assessed by excluding additional family members from analysis and using an independently diagnosed embryo as phasing reference. Suitability for third-party reproduction through single-parent haplotyping was evaluated by excluding one biological parent from analysis. Results were validated against reference PGT methods. MAIN RESULTS AND THE ROLE OF CHANCE: Genome-wide haplotypes of single cells were highly accurate (mean > 99%) compared to bulk DNA. Unbalanced chromosomal abnormalities (>5 Mb) were detected by GENType. For both PGT-M as well as PGT-SR/PGT-A, our technology demonstrated 100% concordance with reference PGT methods for diverse WGA methods. Equally, for parents-only haplotyping and single-parent haplotyping (of autosomal dominant disorders and X-linked disorders), PGT-M results were fully concordant. Furthermore, the origin of trisomies in PGT-M embryos was correctly deciphered by Hopla. LIMITATIONS, REASONS FOR CAUTION: Intrinsic to linkage-analysis strategies, de novo single-nucleotide variants remain elusive. Moreover, parents-only haplotyping is not a stand-alone approach and requires prior diagnosis of at least one reference embryo by an independent technology (i.e. direct mutation analysis) for haplotype phasing. Using a haplotyping approach, the presence of a homologous recombination site across the chromosome is biologically required to distinguish meiotic II errors from mitotic errors during trisomy origin investigation. WIDER IMPLICATIONS OF THE FINDINGS: We offer a generic, fully automatable and accurate pipeline for PGT-M, PGT-A and PGT-SR as well as trisomy origin investigation without the need for personalized assays, microarray technology or WGS. The unique ability to perform single-parent assisted haplotyping of embryos paves the way for cost-effective PGT in a third-party reproduction setting. STUDY FUNDING/COMPETING INTEREST(S): L.D.W. is supported by the Research Foundation Flanders (FWO; 1S74619N). L.R. and B.M. are funded by Ghent University and M.B., S.S., K.T., F.V.M. and A.D. are supported by Ghent University Hospital. Research in the N.C. lab was funded by Ghent University, VIB and Kom op Tegen Kanker. A.D.K and N.C. are co-inventors of patent WO2017162754A1. The other authors have no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

[The translation of genetic risk variants to molecular disease mechanisms]. / De vertaling van genetische risicovarianten naar moleculaire ziektemechanismen.

BACKGROUND: Genetic studies have found large numbers of genetic risk variants that increase the risk to develop neuropsychiatric disorders. AIM: We aim to explain how to investigate the effects of these genetic risk variants on the expression of genes and whether this plays a potential role in neuropsychiatric disorders. METHOD: We describe the main findings of a study that we recently performed to study the association between genetic risk factors for neuropsychiatric disorders and gene expression in microglia, the immune cells of the brain. RESULTS: Part of the risk variants for neuropsychiatric disorders could be related to gene expression in microglia. These
associations were particularly strong for neurodegenerative disorders. CONCLUSION: Our study provided more insight into how genetic risk to neuropsychiatric disorders is related to gene expression in microglia. These findings show suggestions for potential new treatment options.

High seroprevalence of COVID-19 infection in a large slum in South India; what does it tell us about managing a pandemic and beyond?

People living in urban slums or informal settlements are among the most vulnerable communities, highly susceptible to coronavirus disease 2019 (COVID-19) infection and vulnerable to the consequences of the measures taken to control the spread of the virus. Fear and stigma related to infection, mistrust between officials and the population, the often-asymptomatic nature of the disease is likely to lead to under-reporting. We conducted a cross-sectional study to determine the seroprevalence of COVID-19 infection in a large slum in South India 3 months after the index case and recruited 499 adults (age >18 years). The majority (74.3%) were females and about one-third of the population reported comorbidities. The overall seroprevalence of IgG antibody for COVID-19 was 57.9% (95% CI 53.4-62.3). Age, education, occupation and the presence of reported comorbidities were not associated with seroprevalence (P-value >0.05). Case-to-undetected-infections ratio was 1:195 and infection fatality rate was calculated as 2.94 per 10 000 infections. We estimated seroprevalence of COVID-19 was very high in our study population. The focus in this slum should shift from infection prevention to managing the indirect consequences of the pandemic. We recommend seroprevalence studies in such settings before vaccination to identify the vulnerability of COVID-19 infection to optimise the use of insufficient resources. It is a wake-up call to societies and nations, to dedicate paramount attention to slums into recovery and beyond - to build, restore and maintain health equity for the 'Health and wellbeing of all'.

Vitamin D concentration and psychotic disorder: associations with disease status, clinical variables and urbanicity.

BACKGROUND: The association between schizophrenia and decreased vitamin D levels is well documented. Low maternal and postnatal vitamin D levels suggest a possible etiological mechanism. Alternatively, vitamin D deficiency in patients with schizophrenia is presumably (also) the result of disease-related factors or demographic risk factors such as urbanicity. METHODS: In a study population of 347 patients with psychotic disorder and 282 controls, group differences in vitamin D concentration were examined. Within the patient group, associations between vitamin D, symptom levels and clinical variables were analyzed. Group × urbanicity interactions in the model of vitamin D concentration were examined. Both current urbanicity and urbanicity at birth were assessed. RESULTS: Vitamin D concentrations were significantly lower in patients (B = -8.05; 95% confidence interval (CI) -13.68 to -2.42; p = 0.005). In patients, higher vitamin D concentration was associated with lower positive (B = -0.02; 95% CI -0.04 to 0.00; p = 0.049) and negative symptom levels (B = -0.03; 95% CI -0.05 to -0.01; p = 0.008). Group differences were moderated by urbanicity at birth (χ2 = 6.76 and p = 0.001), but not by current urbanicity (χ2 = 1.50 and p = 0.224). Urbanicity at birth was negatively associated with vitamin D concentration in patients (B = -5.11; 95% CI -9.41 to -0.81; p = 0.020), but not in controls (B = 0.72; 95% CI -4.02 to 5.46; p = 0.765). CONCLUSIONS: Lower vitamin D levels in patients with psychotic disorder may in part reflect the effect of psychosis risk mediated by early environmental adversity. The data also suggest that lower vitamin D and psychopathology may be related through direct or indirect mechanisms.

Assessment and treatment of recurrent urinary tract infections in women: development of a questionnaire based on a qualitative study of patient expectations in secondary care.

BACKGROUND: To develop a questionnaire to facilitate the inventorying of women's expectations for the assessment and treatment of recurrent urinary tract infection (UTI) in secondary care. METHODS: Semi-structured interviews were conducted among women with recurrent UTI referred to our urology department. The interviews were conducted by one interviewer, recorded, transcribed verbatim, and analyzed thematically by two researchers. We first developed 35 questions to identify potential themes, and we then tested them among women with and without recurrent UTI. Changes were made according to the feedback received. RESULTS: Six interviews were conducted before saturation was reached. Thematic analysis identified three themes: patient pathway, personal knowledge, and social implications. All respondents had received multiple antibiotic courses but no prophylactic antibiotic therapy, and although all were aware of some preventive measures, they wanted more information about their disease. However, some women were afraid to access information for fear of what they might learn. Recurrent UTI also significantly affected the daily lives all respondents. Some women expressed fears over frequent antibiotic use, and others felt that there must be something wrong with their body to have so many UTIs. Women expected the urologist to provide an explanation and to start adequate therapy for their recurrent UTI. We created a 32-item questionnaire based on these themes CONCLUSION: This study not only developed a questionnaire for use when assessing patient expectations of recurrent UTI management in secondary care but also provided novel insights into the thoughts, opinions, and expectations of women who are referred.

[Is psychiatry ready to let patients review their own files? Inventory of initial experiences]. / Is de psychiatrie klaar voor de meelezende patiënt? Inventarisatie van eerste ervaringen.

BACKGROUND: Dutch patients will be granted the right to digitally access their own medical records, an option already available to the patients at the University Medical Center Utrecht since 2015. AIM: To start a conversation about the development of readily accessible online patient records. METHODS Describe the experiences of a University department of psychiatry with an online patient portal, obtained through discussions and questionnaires. RESULTS: During the next few years three legal developments will enable patients to acquire direct, remote, digital access to their medical files. Immediate online review of medical records improves accessibility and empowers the patient. Some therapists experienced a change in patient interaction. Furthermore, during documentation psychiatrists took into account that patients could review the contents at a later point. CONCLUSION: Patients' accessibility of online records will influence the patient-therapist dynamic. More research on the patient perspective and a discussion among professionals are necessary to further streamline broad implementation of online patient portals.

Characterizing primary human microglia: A comparative study with myeloid subsets and culture models.

The biology of microglia has become subject to intense study, as they are widely recognized as crucial determinants of normal and pathologic brain functioning. While they are well studied in animal models, it is still strongly debated what specifies most accurately the phenotype and functioning of microglia in the human brain. In this study, we therefore isolated microglia from postmortem human brain tissue of corpus callosum (CC) and frontal cortex (CTX). The cells were phenotyped for a panel of typical microglia markers and genes involved in myeloid cell biology. Furthermore, their response to pro- and anti-inflammatory stimuli was assessed. The microglia were compared to key human myeloid cell subsets, including monocytes, monocyte-derived macrophages and monocyte-derived dendritic cells, and several commonly used microglial cell models. Protein and mRNA expression profiles partly differed between microglia isolated from CC and frontal cortex and were clearly distinct from other myeloid subsets. Microglia responded to both pro- (LPS or poly I:C) and anti-inflammatory (IL-4 or dexamethasone) stimuli. Interestingly, pro-inflammatory responses differed between microglia and monocyte-derived macrophages, as the former responded more strongly to poly I:C and the latter more strongly to LPS. Furthermore, we defined a large phenotypic discrepancy between primary human microglia and currently used microglial cell models and cell lines. In conclusion, we further delineated the unique and specific features that discriminate human microglia from other myeloid subsets, and we show that currently used cellular models only partly reflect the phenotype of primary human microglia. GLIA 2016;64:1857-1868.

[Cushing's syndrome in a manic patient with a long-standing bipolar disorder: cause or coincidence?]. / Het syndroom van Cushing bij een manische patiënte met een lang bestaande bipolaire stoornis: oorzaak of bijvangst?

Hypercortisolism is associated with mood disorders such as depression and bipolar disorder. A 75-year-old female patient who had been diagnosed with bipolar disorder forty years ago was admitted to our hospital with a severe, therapy-resistant mania. Careful diagnostic considerations, resulted in the patient being diagnosed with Cushing's syndrome. Treatment with metyrapone led to a swift improvement of the patient's symptoms. Could Cushing's syndrome underlie this patient's psychiatric history? Or are two co-existing, intertwining causes responsible for the psychiatric symptoms? The case illustrates that even if a patient has a long history of psychiatric problems that have been plausibly diagnosed over time, clinicians and psychiatrists should always consider the possibility that there may be an underlying somatic cause for the patient's psychiatric symptoms.

[Auto-immune encephalitis in psychiatric practice]. / Auto-immune encefalitis in de psychiatrische praktijk.

BACKGROUND: Our knowledge about auto-immune limbic encephalitis is increasing rapidly and it is now evident that patients with this disease can present with psychiatric symptoms. AIM: To propose practical guidelines for the recognition and diagnosis of an underlying auto-immune limbic encephalitis in patients with acute psychiatric symptoms. METHOD: We studied recent reviews on the topic and had discussions with psychiatrists, a neurologist and a neuroimmunologist in order to reach consensus. RESULTS: Auto-immune limbic encephalitis is a rather rare but important diagnostic consideration in patients with acute psychiatric symptoms. We describe the different steps in the diagnostic work-up and mention features that can point to an underlying auto-immune encephalitis. These include atypical psychiatric symptoms, seizures, movement disorders and autonomic instability. CONCLUSION: Since patients with autoimmune limbic encephalitis often present with psychiatric symptoms, curative treatment is often available and the prognosis depends on the delay from presentation to treatment, psychiatrists should be aware of the signs of an underlying autoimmune encephalitis which have been described in this article.

[Auto-immune disorders as a possible cause of neuropsychiatric syndromes]. / Auto-immuunaandoeningen als mogelijke oorzaak van neuropsychiatrische syndromen.

BACKGROUND: Changes that occur in the behaviour of voltage-gated ion channels and ligand-gated receptor channels due to gene mutations or auto-immune attack are the cause of channelopathies in the central and peripheral nervous system. Although the relation between molecular channel defects and clinical symptoms has been explained in the case of many neuromuscular channelopathies, the pathophysiology of auto-immunity in neuropsychiatric syndromes is still unclear. AIM: To review recent findings regarding neuronal auto-immune reactions in severe neuropsychiatric syndromes. METHOD: Using PubMed, we consulted the literature published between 1990 and August 2014 relating to the occurrence of auto-immune antibodies in severe and persistent neuropsychiatric syndromes. RESULTS: Auto-antibodies have only limited access to the central nervous system, but if they do enter the system they can, in some cases, cause disease. We discuss recent findings regarding the occurrence of auto-antibodies against ligand-activated receptor channels and potassium channels in neuropsychiatric and neurological syndromes, including schizophrenia and limbic encephalitis. CONCLUSION: Although the occurrence of several auto-antibodies in schizophrenia has been confirmed, there is still no proof of a causal relationship in the syndrome. We still have no evidence of the prevalence of auto-immunity in neuropsychiatric syndromes. The discovery that an antibody against an ion channel is associated with some neuropsychiatric disorders may mean that in future it will be possible to treat patients by means of immunosuppression, which could lead to an improvement in a patient's cognitive abilities.

Complement component 4A protein levels are negatively related to frontal volumes in patients with schizophrenia spectrum disorders.

BACKGROUND: Excessive C4A-gene expression may result in increased microglia-mediated synaptic pruning. As C4A overexpression is observed in schizophrenia spectrum disorders (SSD), this mechanism may account for the altered brain morphology (i.e. reduced volume and cortical thickness) and cognitive symptoms that characterize SSD. Therefore, this study investigates the association of C4A serum protein levels with brain morphology and cognition, and in particular whether this association differs between recent-onset SSD (n = 69) and HC (n = 40). METHODS: Serum C4A protein levels were compared between groups. Main outcomes included total gray matter volume, mean cortical thickness and cognitive performance. Regression analysis on these outcomes included C4A level, group (SSD vs. HC), and C4A*Group interactions. All statistical tests were corrected for age, sex, BMI, and antipsychotic medication dose. Follow-up analyses were performed on separate brain regions and scores on cognitive sub-tasks. RESULTS: The group difference in C4A levels was not statistically significant (p = 0.86). The main outcomes did not show a significant interaction effect (p > 0.13) or a C4A main effect (p > 0.27). Follow-up analyses revealed significant interaction effects for the left medial orbitofrontal and left frontal pole volumes (p < 0.001): C4A was negatively related to these volumes in SSD, but positively in HC. CONCLUSION: This study demonstrated that C4A was negatively related to - specifically - frontal brain volumes in SSD, but this relation was inverse for HC. The results support the hypothesis of complement-mediated brain volume reduction in SSD. The results also suggest that C4A has a differential association with brain morphology in SSD compared to HC.

The Patient Pathway for Men with Chronic Urinary Retention: Treatments, Complications, and Consequences.

OBJECTIVE: To explore the treatment options for chronic urinary retention (CUR) in men, including treatment-related complications and consequences. METHODS: This retrospective cohort study included male patients diagnosed with a non-neurogenic, symptomatic and/or high-risk, CUR >150 mL in a large Dutch non-academic teaching hospital. Data for treatments, complications, and consequences (eg, diagnostics, additional treatments, and hospital contact) were recorded and incidence rate ratios (IRRs) were calculated. RESULTS: We enrolled 177 patients (median age, 77 years; range, 44-94) with a median follow-up of 68 months (range, 1-319) during which they had a median of 8 events (range, 1-51). Most patients initially received a urethral catheter (74%) and some form of catheterization as their final treatment (87%). Compared with non-surgical cases, catheterization was more likely to be stopped after de-obstructive prostate surgery (IRR, 4.18; P < 0.001). Urinary tract infection (IRR, 3.68; P < 0.001) and macroscopic hematuria (IRR, 5.35; P < 0.001) were more common with catheterization, but post-renal problems were more likely in patients with no catheterization (IRR, 25.36; P < 0.001). The lowest chance of complication was with clean intermittent catheterization, and complications were usually managed in outpatient (77%) or emergency (6%) departments, rather than by admission (17%). CONCLUSION: Most patients require catheterization for CUR, with clean intermittent catheterization preferred due to its comparatively lower complication risk. De-obstructive prostate surgery increases the chance of stopping catheterization and may be considered in suitable cases.

Impaired recruitment of bone-marrow-derived endothelial and hematopoietic precursor cells blocks tumor angiogenesis and growth.

The role of bone marrow (BM)-derived precursor cells in tumor angiogenesis is not known. We demonstrate here that tumor angiogenesis is associated with recruitment of hematopoietic and circulating endothelial precursor cells (CEPs). We used the angiogenic defective, tumor resistant Id-mutant mice to show that transplantation of wild-type BM or vascular endothelial growth factor (VEGF)-mobilized stem cells restore tumor angiogenesis and growth. We detected donor-derived CEPs throughout the neovessels of tumors and Matrigel-plugs in an Id1+/-Id3-/- host, which were associated with VEGF-receptor-1-positive (VEGFR1+) myeloid cells. The angiogenic defect in Id-mutant mice was due to impaired VEGF-driven mobilization of VEGFR2+ CEPs and impaired proliferation and incorporation of VEGFR1+ cells. Although targeting of either VEGFR1 or VEGFR2 alone partially blocks the growth of tumors, inhibition of both VEGFR1 and VEGFR2 was necessary to completely ablate tumor growth. These data demonstrate that recruitment of VEGF-responsive BM-derived precursors is necessary and sufficient for tumor angiogenesis and suggest new clinical strategies to block tumor growth.

[The psychometric properties of three self-report screening instruments for identifying frail older people in the community]. / Psychometrische eigenschappen van drie screeningsinstrumenten voor kwetsbaarheid bij thuiswonende ouderen.

BACKGROUND: Frailty can lead towards serious adverse consequences, such as disability. With regard to prevention valid screening instruments are needed to identify frail older people. The aim was to evaluate and compare the psychometric properties of three screening instruments: the Groningen Frailty Indicator (GFI), the Tilburg Frailty Indicator (TFI) and the Sherbrooke Postal Questionnaire (SPQ). For validation purposes the Groningen Activity Restriction Scale (GARS) was added. METHODS: A questionnaire was sent to 687 older people (> or = 70 years). (1) Agreement between instruments, (2) internal consistency, (3) cumulative scalability according to Mokken scale analysis and (4) construct validity were evaluated. RESULTS: The response rate was 77%. Prevalence estimates of frailty ranged from 40% to 59%. The highest agreement was found between the GFI and TFI (Cohen's kappa = 0.74). Cronbach's alpha for the GFI, TFI and SPQ was 0.73, 0.79 and 0.26, respectively. The scalability of the three instruments was inadequate (Loevinger's H: 0.28, 0.30 and 0.09 for GFI, TFI and SPQ, respectively). Frailty scores correlated significantly with each other and with the GARS scores. CONCLUSION: Especially the GFI and TFI seem to be useful to identify frail older people. Further research regarding their predictive validity is still needed.

Emerging technologies and their potential for generating new assistive technologies.

Limited access to assistive technology (AT) is a well-recognized global challenge. Emerging technologies have potential to develop new assistive products and bridge some of the gaps in access to AT. However, limited analyses exist on the potential of these technologies in the AT field. This paper describes a study that aimed to provide an overview of emerging technological developments and their potential for the AT field. It involved conducting a gray literature review and patent analysis to create an overview of the emerging enabling technologies that may foster the development of new AT products and services and identify emerging AT applications. The analysis identified seven enabling technologies that are relevant to the AT field. These are artificial intelligence, emerging human-computer interfaces, sensor technology, robotics, advances in connectivity and computing, additive manufacturing and new materials. Whilst there are over 3.7 million patents related to these enabling technologies, only a fraction of them - 11,000 patents were identified in the analysis specifically related to AT (0.3%). The paper presents some of the promising examples. Overall, the results indicate that there is an enormous potential for new AT solutions that capitalize on emerging technological advances.

Inhibition of lymphocyte proliferation stimulated by lectins and allogeneic cells by normal plasma lipoproteins.

Lipoproteins, isolated by sequential flotation at densities 1.006, 1.019, 1.063, and 1.21, were examined for their ability to inhibit human lymphocytes stimulated by allogeneic cells and by lectins (phytohemagglutinin-P and concanavalin A). All the classes of normal plasma lipoproteins inhibited lymphoproliferation when peripheral blood lymphocytes were cultured in autologous, heterologous, or lipoprotein-deficient plasma (d greater than 1.21). The rank order of inhibitory potency was intermediate density lipoprotein (IDL) greater than very low density lipoproteins (VLDL) greater than low density lipoproteins (LDL) greater than high density lipoproteins (HDL), regardless of the mode of stimulation. The concentrations of IDL, VLDL, and LDL required for complete inhibition of stimulated lymphoproliferation were considerably below the levels of each of these lipoproteins normally found in human plasma. In addition, the concentration of HDL required for 50-90% inhibition was in the range of HDL levels normally found in human plasma. Moreover, at relatively higher concentrations, lipoproteins suppressed the incorporation of [3H]thymidine into DNA below the levels seen with reseting, unstimulated lymphocytes. The results suggest that circulating lymphocytes may normally be highly suppressed by the combined effects of all the endogenous lipoproteins and that the lipoproteins may play important roles in vivo in modulating lymphocyte functions and responses.

Vascular endothelial growth factor and angiopoietin-1 stimulate postnatal hematopoiesis by recruitment of vasculogenic and hematopoietic stem cells.

Tyrosine kinase receptors for angiogenic factors vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) are expressed not only by endothelial cells but also by subsets of hematopoietic stem cells (HSCs). To further define their role in the regulation of postnatal hematopoiesis and vasculogenesis, VEGF and Ang-1 plasma levels were elevated by injecting recombinant protein or adenoviral vectors expressing soluble VEGF(165), matrix-bound VEGF(189), or Ang-1 into mice. VEGF(165), but not VEGF(189), induced a rapid mobilization of HSCs and VEGF receptor (VEGFR)2(+) circulating endothelial precursor cells (CEPs). In contrast, Ang-1 induced delayed mobilization of CEPs and HSCs. Combined sustained elevation of Ang-1 and VEGF(165) was associated with an induction of hematopoiesis and increased marrow cellularity followed by proliferation of capillaries and expansion of sinusoidal space. Concomitant to this vascular remodeling, there was a transient depletion of hematopoietic activity in the marrow, which was compensated by an increase in mobilization and recruitment of HSCs and CEPs to the spleen resulting in splenomegaly. Neutralizing monoclonal antibody to VEGFR2 completely inhibited VEGF(165), but not Ang-1-induced mobilization and splenomegaly. These data suggest that temporal and regional activation of VEGF/VEGFR2 and Ang-1/Tie-2 signaling pathways are critical for mobilization and recruitment of HSCs and CEPs and may play a role in the physiology of postnatal angiogenesis and hematopoiesis.