Therapeutic liver repopulation by transient acetaminophen selection of gene-modified hepatocytes

Gene therapy by integrating vectors is promising for monogenic liver diseases, especially in children where episomal vectors remain transient. However, reaching the therapeutic threshold with genome-integrating vectors is challenging. Therefore, we developed a method to expand hepatocytes bearing therapeutic transgenes. The common fever medicine acetaminophen becomes hepatotoxic via cytochrome p450 metabolism. Lentiviral vectors with transgenes linked in cis to a Cypor shRNA were administered to neonatal mice. Hepatocytes lacking the essential cofactor of Cyp enzymes, NADPH-cytochrome p450 reductase (Cypor), were selected in vivo by acetaminophen administration, replacing up to 50% of the hepatic mass. Acetaminophen treatment of the mice resulted in over 30-fold expansion of transgene-bearing hepatocytes and achieved therapeutic thresholds in hemophilia B and phenylketonuria. We conclude that therapeutically modified hepatocytes can be selected safely and efficiently in preclinical models with a transient regimen of moderately hepatotoxic acetaminophen.

Heart rate response during cardiopulmonary exercise in heart transplant recipients

Background

Denervation at heart transplant (HTx) results in attenuated heart rate (HR) control and limited exercise tolerance.

Purpose

The aim of this study was to assess longitudinal changes in the HR response to exercise in HTx recipients. We compared the results with those of healthy controls.

Methods

Seventy-four HTx recipients were enrolled in a cardiopulmonary exercise trial. The HR response to maximal exercise was tested at 11 weeks and at 1- and 3-years follow-up post HTx, and compared with the HR response in 50 age and gender matched controls. The HR was measured at rest, at 25-, 50-, 75-, and 100% of VO2peak, and 30 sec, 1, 2, and 4 min after peak exercise on a treadmill or bicycle ergometer. We also assessed the HR reserve and the chronotropic response index (CRI).

Results

Elleven weeks after HTx, the HR response to exercise was blunted, but improved significantly during follow-up. The change in HR from rest to peak exercise increased by 53% (41 bpm vs 62 bpm; p<0.001) from inclusion to 12 months follow-up, but levelled off between 12- and 36 months (62 bpm vs 65 bpm; p=0.59) (Figure 1). In comparison, the exercise-induced increase in HR in healthy controls was 117 bpm. In HTx recipients, approximately 40% of the total increase in HR occurred between rest and 25% of VO2peak at inclusion (Figure). In contrast, only 31% of the increase in HR in healthy controls occurred between rest and 25% of VO2peak (p<0.001). The fall in HR during the first 4 minutes after exercise increased over the duration of the study (p<0.001 for all comparisons between inclusion and 12 months, and 12- and 36 months at 30 sec, 1, 2, 3 and 4 min after exercise). During the first minute after the end of exercise, the HR rose 2 bpm at baseline, but fell 10 bpm at 12 months (p for difference <0.001). However, even at 36 months, the decline in HR after exercise remained less rapid than in healthy controls (p<0.001) (Figure). CRI increased between baseline and 12 months, but levelled off between the 12-month visit and 36 months (0.50±0.2 vs 0.79±0.3; p<0.001 and 0.79±0.3 vs 0.81±0.3; p=0.51). The chronotropic response was normalized (>0.85) in 44% of the HTx recipients at 1 year and in 51% at 3 year after HTx.

Conclusion

The increase and decrease in HR during exercise are considerably muted in de novo HTx recipients. The HR response improves during the first year after surgery, and thereafter levels off. In contrast the decline in HR after exercise seems to increase with time, which may be related to the effect of exercise. This suggests that partial re-innervation takes place. Whether this response continues to improve in the longer term remains to be determined.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): South-Eastern Norway Regional Health Authority

Induced Liver Regeneration Enhances CRISPR/Cas9-Mediated Gene Repair in Tyrosinemia Type 1

The efficiency of gene repair by homologous recombination in the liver is enhanced by CRISP/Cas9 incision near the mutation. In this study, we explored interventions designed to further enhance in vivo hepatocyte gene repair in a model of hereditary tyrosinemia. A two-AAV system was employed: one virus carried a Staphylococcus pyogenes Cas9 (SpCas9) expression cassette and the other harbored a U6 promoter-driven sgRNA and a fragment of fumarylacetoacetate hydrolase (Fah) genomic DNA as the homologous recombination donor. In neonatal mice, a gene correction frequency of ∼10.8% of hepatocytes was achieved. The efficiency in adult mice was significantly lower at ∼1.6%. To determine whether hepatocyte replication could enhance the targeting frequency, cell division was induced with thyroid hormone T3. This more than doubled the gene correction efficiency to 3.5% (p < 0.005). To determine whether SpCas9 delivery was rate limiting, the gene repair AAV was administered to SpCas9 transgenic mice. However, this did not significantly enhance gene repair. Finally, we tested whether the Fanconi anemia (FA) DNA repair pathway was important in hepatocyte gene repair. Gene correction frequencies were significantly lower in neonatal mice lacking the FA complementation group A (Fanca) gene. Taken together, we conclude that pharmacological induction of hepatocyte replication along with manipulation of DNA repair pathways could be a useful strategy for enhancing in vivo gene correction.

Social relations and self-rated health in a multi-ethnic social housing area undergoing demolition

Background

During the coming years, selected social housing areas in Denmark will undergo large structural changes as part of a political agenda. Previous studies on the effects of such interventions are inconclusive. Residential areas are important for the development of social relations and health. The aim of this study was to explore the associations between social relations and self-rated health (SRH) and the interaction with country of origin in an ethnically diverse social housing area undergoing demolition, and compare results with the municipality.

Methods

Data include multilingual interviewer driven surveys with residents aged 45+ years before demolition began in 2018 (N = 209) and during the demolition in 2019 (N = 132), and a health survey on municipality level (N = 1638). Information on social relations include contact frequency with and support from family, friends and neighbors. SRH was dichotomized into high/low. Descriptive and multivariate logistic regression analyses adjusted for age, sex and Western/non-Western origin are presented.

Results

In cross-sectional analyses from 2018, low contact frequency and low support increased the risk of low SRH, OR = 1.44 (0.63-3.29) and OR = 1.23 (0.62-2.48), especially when also having non-Western origin compared to having high contact frequency or support and Western origin, OR = 6.27 (1.80-21.84) and OR = 4.43 (1.68-11.69), respectively. The same association was seen in 2019 and on municipality level.

Low contact frequency in 2018 was associated with higher risk of developing or maintaining low SRH in 2019 compared to the group with high contact frequency in 2018 in longitudinal analyses, OR = 3.04 (0.91-10.91).

Conclusions

Poor social relations increased the risk of low SRH, especially when also having non-Western origin. Having poor social relations before the demolition was associated with an increased risk of developing or maintaining low SRH during the demolition in an ethnically diverse social housing area.

Key messages

Having low contact frequency before area demolition in a social housing area in Denmark increased the risk of developing or maintaining low self-rated health after demolition had begun. Having poor social relations and non-Western origin is associated with a strong increased risk of low self-rated health in a deprived ethnic diverse social housing area in Denmark.

A difference-in-difference analysis comparing a control and an intervention social housing area

Often an intervention is applied in an area (e.g. community, municipality) without it being an experiment and without a control group, this can be categorized as a natural experiment. Such a situation offers the opportunity to exploit exposure contrasts between areas regarding the specific intervention for evaluation. In the present study, we will employ the difference-in-difference approach to evaluate the natural experiment (the structural intervention) comparing measures of health and social factors retrieved from registers in the two social housing areas before and after the intervention. A 'natural experiment' study comparing individual and aggregated level differences in register-based information on health and social variables across time including the entire study period is included in the research project. The population includes all residents with an address in the study area and the control area at any point during the years 2015-2025 (∼3,000 residents in each area). All residents are linked to the Danish social and health registers by the unique personal identification number, which makes it possible to follow all permanent and former residents over time. Hereby we plan to study if the structural changes (the structural intervention, the 'natural experiment') give rise to differences in health (such as use of general practitioner, hospitalizations, use of selected medications) and social factors (e.g. divorces, income levels, unemployment) compared to the control area. The control area is representing a similar social housing area in the same municipality, which will not undergo structural changes until 2023. Findings will be evaluated drawing upon knowledge gained from the entire study from surveys and qualitative interviews as well experiences from the interventions. In this presentation, we wish to discuss how best to include the knowledge based on other methodologies in the register-based analyses.

Experiences and challenges in collecting survey data in an ethnically diverse social housing area

Socio-economically disadvantaged groups are characterised by a higher burden of disease than the background population. Paradoxically, they are often underrepresented in health research. Failing to include socio-economically disadvantaged groups in research impairs the ability to address the social mechanisms creating health disparities. The study describes how we have tried to accommodate identified challenges from the literature in conducting a questionnaire survey in a socio-economically deprived and ethnically diverse social housing area, and which new challenges we identified. The survey is planned before, during and after the structural changes take place. Through innovative approaches, we sought to accommodate identified barriers to reaching participants. The questionnaire was translated from Danish to the seven most prevalent languages in the area, based on data from the national register. A survey corps of native speaking interviewers went door-to-door to perform face-to-face interviews. To encourage participation, we used a recruitment strategy inspired by ethnographic data collection traditions, such as local presence, participation in local activities, and graphic facilitation on invitation letters. Wave 1 and 2 had a response rate of 35% (N = 209) and 22% (N = 132), respectively. 79 respondents participated in both waves. Despite our efforts to accommodate identified challenges such as language, illiteracy, and mistrust, the response rates are low. We identified new challenges in recruiting participants including participation fatigue, frustration with the restructure process, and a feeling of limited individual gain from participation. Many challenges are associated with conducting research among socio-economically disadvantaged groups. Documenting processes and learning from experiences are important steps in including groups with lower socio-economic status in health research in order to address the underlying social mechanisms creating health disparities.

P1270 Systolic blood pressure at age 40 is associated with left atrial volumes at age 64

Funding Acknowledgements

Vestre Viken Hospital Trust

Background

Left atrial (LA) enlargement is associated with elevated blood pressure (BP) and with cardiovascular morbidity and mortality. In the assessment of LA size, echocardiographic guidelines recommend the use of LA end-systolic volume (LAVmax). LA end-diastolic volume (LAVmin) and LA emptying fraction (LAEF) may add valuable information in risk assessment. The knowledge of early adulthood BP and its association to LA volumes and LAEF later in life is limited.

Purpose

To explore the association between systolic BP at age 40 and LA volumes and LAEF at age 64.

Methods

We linked data from subjects who had participated in both a nationwide cardiovascular screening survey (1990-1991) at the age of 40, and the Akershus Cardiac Examination (ACE) 1950 Study (2012-2015) at the age of 64 (n = 2,597). In the ACE 1950 Study, LAVmax and LAVmin were measured with echocardiography according to the summation of discs method. LAEF was calculated as (LAVmax-LAVmin/LAVmax)x100%. The association between systolic BP at age 40 and LA volumes and LAEF at age 64 was assessed in univariate and multivariate linear regression analyses.

Results

Systolic BP at age 40 was associated with LAVmax and LAVmin but not with LAEF at age 64. In our multivariate model, a 10 mm Hg higher systolic BP at age 40 was associated with a 0.9 ml greater LA end-systolic volume and a 0.5 ml greater LA end-diastolic volume at age 64.

Conclusion

Early adulthood systolic BP is associated with LA volumes 24 years later in life.

Table. Association of systolic blood pressure at age 40 to left atrial (LA) volumes and LAEF at age 64 Univariate Multivariate* Dependent variable B (95% CI) p-value B (95% CI) p-value LAVmax (ml) 2.4 (2.0, 2.9) &lt;0.001 0.9 (0.4, 1.4) 0.001 LAVmin (ml) 1.5 (1.1, 1.8) &lt;0.001 0.5 (0.1, 0.9) 0.015 LAEF (%) -0.01 (-0.3, 0.3) 0.938 0.2 (-0.2, 0.5) 0.294 *Adjusted for gender, body mass index, smoking, resting heart rate and antihypertensive treatment, all assessed at age 40. B (95% CI), regression coefficient for systolic blood pressure (per 10 mm Hg) with 95% confidence interval; LAVmax, LA end-systolic volume; LAVmin LA end-diastolic volume; LAEF, LA emptying fraction

103 Normal values and gender differences of left atrial volumes

Funding Acknowledgements

Vestre Viken Hospital Trust

Background

Left atrial (LA) enlargement is associated with cardiovascular morbidity and mortality. Echocardiographic guidelines recommend body surface area (BSA) indexed LA end-systolic volume (LAVimax) in the assessment of LA size with an upper normal limit of 34 ml/m² for both genders and all age groups. LA end-diastolic volume (LAVimin) and LA emptying fraction (LAEF) may add valuable information in risk assessment, but there are limited data on normal values.

Purpose

To add knowledge and explore gender differences of LA volumetric measures.

Methods

In The Akershus Cardiac Examination 1950 Study, all inhabitants of Akershus County, Norway, born in 1950 were invited. In 3,489 individuals LAVmax and LAVmin were measured with echocardiography according to the summation of discs method and indexed to BSA. LAEF was calculated. A healthy group was defined by excluding those with heart failure, atrial fibrillation, coronary artery disease, stroke, hypertension, diabetes, chronic obstructive pulmonary disease, body mass index &gt; 30kg/m², eGFR &lt; 60 ml/min/1.73 m², left ventricular ejection fraction &lt; 50%, E/e’&gt;14 and E/A &gt; 2.0. Data are presented as mean ± standard deviation (SD) and a normal range of mean ± 2SD. T-tests were used for comparisons.

Results

In 840 healthy individuals, aged 63.8 ± 0.6 years, mean LAVimax was 25.6 ± 6.3 ml/m² and the normal range was 13.0-38.2 ml/m². Men had significantly larger volumes than women.

Conclusion

We present LA volumes and LAEF in a large cohort from the general population at age 64. The upper normal limit of LAVimax in 840 healthy individuals was 38 ml/m². Men had larger LA volumes than women, contrary to most previous studies. Thus, 13% of the healthy men in our cohort would be defined with an enlarged atrium with the current cut-off value at 34 ml/m².

Table. Left atrial (LA) volumes and LAEF Total (mean ± SD) Total (2SD range) Male (mean ± SD) Female (mean ± SD) P-value (male vs. female) All participants (n = 3489) LAVimax (ml/m&sup2;) 26.8 ± 7.6 11.6-42.0 27.9 ± 8.1 25.6 ± 6.8 &lt;0.001 LAVimin (ml/m&sup2;) 14.7 ± 5.8 3.1-26.3 15.5 ± 6.5 13.9 ± 4.9 &lt;0.001 LAEF (%) 45.6 ± 9.7 26.2-65.0 45.3 ± 10.2 45.9 ± 9.2 0.07 Healthy group (n = 840) LAVimax (ml/m&sup2;) 25.6 ± 6.3 13.0-38.2 26.6 ± 6.7 24.9 ± 5.8 &lt;0.001 LAVimin (ml/m&sup2;) 13.7 ± 4.3 5.1-22.3 14.1 ± 4.6 13.3 ± 3.9 0.008 LAEF (%) 46.8 ± 8.8 29.2-64.4 47.0 ± 9.1 46.5 ± 8.4 0.37 LAVimax, LA end-systolic volume, body surface area (BSA)-indexed; LAVimin, LA end-diastolic volume, BSA-indexed; LAEF, LA emptying fraction; SD, standard deviation

AAV-Mediated CRISPR/Cas9 Gene Editing in Murine Phenylketonuria

Phenylketonuria (PKU) due to recessively inherited phenylalanine hydroxylase (PAH) deficiency results in hyperphenylalaninemia, which is toxic to the central nervous system. Restriction of dietary phenylalanine intake remains the standard of PKU care and prevents the major neurologic manifestations of the disease, yet shortcomings of dietary therapy remain, including poor adherence to a difficult and unpalatable diet, an increased incidence of neuropsychiatric illness, and imperfect neurocognitive outcomes. Gene therapy for PKU is a promising novel approach to promote lifelong neurological protection while allowing unrestricted dietary phenylalanine intake. In this study, liver-tropic recombinant AAV2/8 vectors were used to deliver CRISPR/Cas9 machinery and facilitate correction of the Pah ^enu2 allele by homologous recombination. Additionally, a non-homologous end joining (NHEJ) inhibitor, vanillin, was co-administered with the viral drug to promote homology-directed repair (HDR) with the AAV-provided repair template. This combinatorial drug administration allowed for lifelong, permanent correction of the Pah ^enu2 allele in a portion of treated hepatocytes of mice with PKU, yielding partial restoration of liver PAH activity, substantial reduction of blood phenylalanine, and prevention of maternal PKU effects during breeding. This work reveals that CRISPR/Cas9 gene editing is a promising tool for permanent PKU gene editing.

Using a barcoded AAV capsid library to select for clinically relevant gene therapy vectors

While gene transfer using recombinant adeno-associated viral (rAAV) vectors has shown success in some clinical trials, there remain many tissues that are not well transduced. Because of the recent success in reprogramming islet-derived cells into functional β cells in animal models, we constructed 2 highly complex barcoded replication competent capsid shuffled libraries and selected for high-transducing variants on primary human islets. We describe the generation of a chimeric AAV capsid (AAV-KP1) that facilitates transduction of primary human islet cells and human embryonic stem cell-derived β cells with up to 10-fold higher efficiency compared with previously studied best-in-class AAV vectors. Remarkably, this chimeric capsid also enabled transduction of both mouse and human hepatocytes at very high levels in a humanized chimeric mouse model, thus providing a versatile vector that has the potential to be used in both preclinical testing and human clinical trials for liver-based diseases and diabetes.

Bioengineered AAV Capsids with Combined High Human Liver Transduction In Vivo and Unique Humoral Seroreactivity

Existing recombinant adeno-associated virus (rAAV) serotypes for delivering in vivo gene therapy treatments for human liver diseases have not yielded combined high-level human hepatocyte transduction and favorable humoral neutralization properties in diverse patient groups. Yet, these combined properties are important for therapeutic efficacy. To bioengineer capsids that exhibit both unique seroreactivity profiles and functionally transduce human hepatocytes at therapeutically relevant levels, we performed multiplexed sequential directed evolution screens using diverse capsid libraries in both primary human hepatocytes in vivo and with pooled human sera from thousands of patients. AAV libraries were subjected to five rounds of in vivo selection in xenografted mice with human livers to isolate an enriched human-hepatotropic library that was then used as input for a sequential on-bead screen against pooled human immunoglobulins. Evolved variants were vectorized and validated against existing hepatotropic serotypes. Two of the evolved AAV serotypes, NP40 and NP59, exhibited dramatically improved functional human hepatocyte transduction in vivo in xenografted mice with human livers, along with favorable human seroreactivity profiles, compared with existing serotypes. These novel capsids represent enhanced vector delivery systems for future human liver gene therapy applications.

A universal system to select gene-modified hepatocytes in vivo

Many genetic and acquired liver disorders are amenable to gene and/or cell therapy. However, the efficiencies of cell engraftment and stable genetic modification are low and often subtherapeutic. In particular, targeted gene modifications from homologous recombination are rare events. These obstacles could be overcome if hepatocytes that have undergone genetic modification were to be selectively amplified or expanded. We describe a universally applicable system for in vivo selection and expansion of gene-modified hepatocytes in any genetic background. In this system, the therapeutic transgene is coexpressed with a short hairpin RNA (shRNA) that confers modified hepatocytes with resistance to drug-induced toxicity. An shRNA against the tyrosine catabolic enzyme 4-OH-phenylpyruvate dioxygenase protected hepatocytes from 4-[(2-carboxyethyl)-hydroxyphosphinyl]-3-oxobutyrate, a small-molecule inhibitor of fumarylacetoacetate hydrolase. To select for specific gene targeting events, the protective shRNA was embedded in a microRNA and inserted into a recombinant adeno-associated viral vector designed to integrate site-specifically into the highly active albumin locus. After selection of the gene-targeted cells, transgene expression increased 10- to 1000-fold, reaching supraphysiological levels of human factor 9 protein (50,000 ng/ml) in mice. This drug resistance system can be used to achieve therapeutically relevant transgene levels in hepatocytes in any setting.

Heterogeneous effects of bradykinin and a23187 on glioma growth, migration and invasion

To evaluate the role of receptor interaction and calcium mobilization in growth of gliomas, we examined the effects of bradykinin (BK) and the calcium ionophore A23187 on growth, migration and invasion of the continuous human glioma cell lines GaMG, D37-MG and D54-MG. BK induced a transient increase in intracellular calcium concentration only in D54-MG. A23187 but not BK inhibited glioma proliferation both during monolayer and spheroid growth. Migration of cells from glioma spheroids was slightly inhibited in GaMG both in response to BK and A23187. No effects were seen in D37-MG or D54-MG. Both BK and A23187 inhibited the glioma invasion as assessed with the glioma/brain aggregate co-culture technique in all three cell lines studied. It is concluded that an increase in the intracellular calcium concentration inhibits both growth and invasion of gliomas. The inhibitory effect of BK on glioma invasion may be mediated by a calcium-independent mechanism.