Preserved Th2 lymphocytes improve prognosis of diabetic patients undergoing TAVR

Introduction

Previous studies have shown that presence of diabetes (DM) worsens outcome of patients after transfemoral aortic valve (TAVR). DM has been associated with pathological T-lymphocyte (T-cell) polarization, marked by decreased anti-inflammatory Th2 cells and increased pro-inflammatory Th1 cells. However, the risk-modulatory impact of T-cell polarization in diabetic patients with severe aortic stenosis has not been shown thus far. In this study we assessed the role of T-cell subsets in diabetic patients undergoing TAVR.

Methods and results

A total of 129 patients (76% male, median age [IQR]: 83 years [79–86]) admitted for TAVR at the University Clinic Frankfurt were enrolled. The patients were evaluated using classical risk scores and the Th1/Th2 T-cell polarization was assessed using flow cytometry. The endpoint of the study was all-cause death. Kaplan-Meier survival, ROC curve analysis and Mann-Whitney-U-Test were used in statistical analysis. The differences were considered significant by error probability p<0.05. Twenty-six patients died within follow up of 274 (188–367) days. The conventional risk parameters were distributed as follows: STS score: 3.45 (2.47–4.97), LVEF: 60% (45–65), CRP: 0.33 mg/dl (0.15–0.79), hsTropT: 24.5 pg/ml (16.5–40.0), IL6: 6.7 pg/ml (4.1–12.2), Hb: 12.3 g/dl (11.00–13,75), Creatinine: 1.15 mg/dl (0.93–1.54), Th1 cells = 79.88 cells/μl (55.69–122.16), Th2 cells: 25.31 cells/μl (19.69–38.33), NT-proBNP: 2033 pg/ml (1076–5531). All these parameters were associated with mortality. Hence, only Hb (AUC=0.761), NT-proBNP (AUC=0.726), Th2 cells (AUC=0.712) and STS score (AUC=0.737) provided AUC>0.7. Diabetes was revealed to be significantly associated with mortality in patients with and without DM (15/48 (31%) vs. 11/81 (14%), respectively, P=0.019). There were no significant differences in the counts of Th-cell subsets between diabetic and non-diabetic patients (Th1 (90.95 (62.41–154.22) vs 76.36 (53.16–100.49), P=0.072); Th2 (29.18 (20.13–43.77) vs 24.74 (20.27- 35.11), p=0.245), for DM and non-DM respectively). However, the survival rate in patients with DM and Th2 cell counts higher than or equal to the calculated optimal cut-off of 24.3 cells/μl was comparable with patients without DM (25/28 (89%) vs. 36/38 (95%), p=0.453). In contrast, diabetic patients with reduced Th2 cells (<24.3 cells/μl) were much more likely to die (10/15 (67%) vs. 8/34 (24%), p=0.003, patients with DM and without, respectively).

Conclusion

Our results show for the first time a risk-modulatory impact of T-cell immunity in diabetic patients with severe degenerative aortic stenosis. Reduced Th2 cells are strongly associated with mortality in patients considered for TAVR and significantly deteriorate prognosis in patients with concomitant diabetes.

Funding Acknowledgement

Type of funding source: None

Patient-centredness in acute stroke care - a qualitative study from the perspectives of patients, relatives and staff

BACKGROUND AND PURPOSE

Although patient-centredness is considered a key component of high-quality neurological care, it is unclear to what extent it can or should be implemented during the acute phase. Using acute stroke as an example, the aim was to identify critical junctures for patient-centredness along the acute care pathway from the perspectives of patients, relatives and staff.

METHODS

A qualitative multi-method study was conducted including 27 non-participant observations and 37 semi-structured interviews with patients, relatives and staff. Junctures were defined as critical when mentioned (as problematic) in two or three information sources (i.e. observations, staff interviews, or patient and relative interviews), as potentially critical when mentioned in one, and as uncritical when not mentioned.

RESULTS

Post-procedure communication after thrombectomy, patients' stay at the stroke unit and decision-making around transfer, discharge and rehabilitation were identified as critical junctures for patient-centredness. Arrival at the emergency department and the (thrombectomy) treatment itself were identified as uncritical junctures, whilst history-taking and treatment preparation, the treatment decision and patients' stay at the intensive care unit were identified as potentially critical junctures.

CONCLUSIONS

In acute stroke care, patients, relatives and staff prioritize fast over patient-centred decision-making in the most time-critical phases, especially before and during treatment. This is reversed after the procedure, when difficulties arise implementing a patient-centred approach in clinical practice. To improve patient-centredness where it is most needed, clear guidelines and accessible resources are recommended. Future research should investigate whether insights from acute phases of stroke care are applicable to other neurological conditions as well.

Protein resonance assignment by BSH-CP-based 3D solid-state NMR experiments: A practical guide

Solid-state NMR (ssNMR) spectroscopy has evolved into a powerful method to obtain structural information and to study the dynamics of proteins at atomic resolution and under physiological conditions. The method is especially well suited to investigate insoluble and noncrystalline proteins that cannot be investigated easily by X-ray crystallography or solution NMR. To allow for detailed analysis of ssNMR data, the assignment of resonances to the protein atoms is essential. For this purpose, a set of three-dimensional (3D) spectra needs to be acquired. Band-selective homo-nuclear cross-polarization (BSH-CP) is an effective method for magnetization transfer between carbonyl carbon (CO) and alpha carbon (CA) atoms, which is an important transfer step in multidimensional ssNMR experiments. This tutorial describes the detailed procedure for the chemical shift assignment of the backbone atoms of ¹³ C-¹⁵ N-labeled proteins by BSH-CP-based ¹³ C-detected ssNMR experiments. A set of six 3D experiments is used for unambiguous assignment of the protein backbone as well as certain side-chain resonances. The tutorial especially addresses scientists with little experience in the field of ssNMR and provides all the necessary information for protein assignment in an efficient, time-saving approach.

The prognostic significance of the lymph node ratio in oral cancer differs for anatomical subsites

The aim of this study was to validate the prognostic significance of the lymph node ratio (LNR) in patients suffering from oral squamous cell carcinoma in regard to different anatomical subsites. A cohort of 430 patients was investigated to determine the rates of primary metastasis and local and regional disease recurrence. Correlation analysis of the LNR with relevant clinical and pathological parameters was performed. Receiver operating characteristic (ROC) curve analysis was conducted to evaluate the prognostic impact for different subsites. Significantly differing rates of primary metastasis and loco-regional disease recurrence were found for cancer of different anatomical subsites of the head and neck. Furthermore, ROC curve analysis suggested that LNR has prognostic relevance in subsets of cancer (tongue, P< 0.001; alveolar process, P= 0.04; maxilla, P= 0.03; buccal mucosa, P= 0.02). The LNR of cancer located in the soft palate (P= 0.6) and floor of the mouth (P= 0.11) showed little or no association with the clinical outcome. There is the need for a more sensitive consideration of the LNR as a factor in the assessment of risk and the treatment decision, as the anatomical subsite plays a crucial role in its impact on the clinical outcome.

P1850Usefulness and predictive value of the prognostic nutritional index compared to other commonly-used nutritional indexes as a prognostic nutritional marker for short- and mid-term survival after TAVR

Background

Several nutritional indexes predict clinical outcomes after trans-catheter aortic valve replacement (TAVR). The Prognostic Nutritional Index (PNI) is based on serum albumin and lymphocyte count, which makes it a highly practical tool to assess nutritional status. Prognostic value of PNI has been shown in some heart diseases and interventions. Usefulness and predictive value of PNI were investigated in patients with symptomatic aortic stenosis undergoing TAVR. PNI was compared with other commonly-used nutritional indexes that predict survival after TAVR.

Methods

A prospective observational study was carried out in a cohort of 114 patients with aortic stenosis undergoing TAVR in a high-volume centre from 09/2016 to 02/2018. Pre-procedural characteristics and laboratory parameters were measured, and a 1-year follow-up was completed.

PNI was estimated with the formula: (10 × serum albumin [g/dl]) + (0.005 × total lymphocytes [1,000/μl]). Baseline clinical features and 1-year survival were compared in patients with PNI values above vs below median.

A multivariate Cox regression analysis was used to assess the independent predictive value of PNI, for 1-year mortality after TAVR. Kaplan-Meier curves were constructed for patients with PNI above vs below median value. ROC curves were created to assess discrimination ability of PNI, and to compare its AUC values with those for other common nutritional markers, such as Geriatric Nutritional Risk Index (GNRI) and body mass index (BMI).

Results

Mean age was 82.2 years and 59.6% of patients were female. Mean PNI was 46±5. No differences were found in pre-procedural clinical characteristics between patients with PNI values above vs below median.

One-year mortality was significantly higher in patients with PNI values below median (19/23) than in patients with higher PNI values (4/23) (p<0.001). No differences were found in complications according to Valve Academic Research Consortium Criteria-2.

Lower PNI values significantly predicted a lower 1-year survival, even after adjusting for all clinical factors showing significant differences in a univariate analysis (model 1: HR 0.8, 95% CI 0.7–0.9, p<0.0001). Significance persisted also after adjusting for relevant laboratory factors (NT-proBNP, hs-Troponin, CRP, eGFR, cystatin, haemoglobin) (model 2: HR 0.8, 95% CI 0.7–0.9, p<0.05). Kaplan-Meier curves started to diverge soon after the intervention (figure). ROC curves revealed a stronger predictive value for PNI (AUC 0.80) compared to GNRI (0.77) and BMI (0.6) (figure).

Kaplan-Meier curve for PNI and ROC curve

Conclusion

PNI is a useful and practical nutritional marker predicting 1-year survival after TAVR in aortic stenosis. It appears to reflect malnutrition and inflammation prior to the intervention, and to have an impact on prognosis. PNI seems to be a better prognostic marker than BMI or GNRI after TAVR.

6091Chronic heart failure is associated with inflammatory deterioration of the bone marrow vascular niche

Introduction

Inflammation plays a crucial role in many aspects of cardiovascular disease. Particularly, acquired mutations of hematopoietic stem cells (HSC) leading to clonal expansion of inflammatory cells (CHIP) are increased with age and are associated with an enhanced risk of cardiovascular disease. The bone marrow (BM) vascular niche plays a crucial role in maintenance and regulation of HSC functions. Previous studies in mice showed the reduction of a specific Endomucin-high (H-type) endothelial cells (EC) subpopulation by aging. However, the impact of cardiovascular disease is unclear. Therefore, we aimed to investigate the effects of age and heart failure (HF) on the vascular BM cell composition in mice and humans.

Methods and results

Aging mice showed an age-dependent decrease of type H (Emcn-high) BM ECs (p=0.004), whereas the BM frequencies of type L (Emcn-low) ECs did not significantly differ (P=0.18). Importantly, we also observed a marked reduction of type H EC in chronic ischemic mice (P=0.016 vs. sham) indicating that chronic ischemic HF induces similar alterations of the vascular stem cell niche. Importantly, type H ECs were also significantly reduced in ischemic HF patients (n=16) compared with control subjects (n=8; P=0.0003). To gain insights into the mechanisms underlying the changes in the vascular niche, we performed single cells RNA sequencing of human BM ECs. These studies confirmed the decrease in Emcn-expressing ECs in ischemic HF patients, which was accompanied by significantly increased expression of inflammatory genes, including IL1b (P<0.0001 vs. control). Inflammatory EC phenotypes and IL1b expression in HF could be further confirmed at protein level using cytospin immunostainings. Finally, we comprehensively evaluated phenotype-associated differences in the bone marrow plasma proteomes of healthy individuals (n=19) and patients with chronic ischemic (n=22) and non-ischemic (n=19) HF, using proximity extension assays. Here, we identified 182 proteins significantly differentially regulated in CHF versus CTRL. Among the top upregulated proteins the BM environment of patients with CHF showed a striking enrichment of inflammatory and ECM remodeling components.

Conclusions

Our data show for the first time an impact of chronic heart failure on the bone marrow vascular niche in humans. These changes seem to be strongly associated with increased inflammatory response and bone matrix remodeling in CHF. Specifically, the induction of the inflammatory cytokine IL1b may contribute to the disturbed phenotype suggesting that inhibition of IL1b (e.g. by canakinumab) may be used as a novel strategy to prevent or reverse the deterioration of the vascular BM niche.

1438MicroRNA editing is integral for interleukin-6 trans-signalling and leukocyte trafficking to ischemic tissues

Background/Aim

Adenosine to inosine RNA editing is an essential post-transcriptional RNA modification catalysed by adenosine deaminase acting on RNA-1 and -2 (ADAR1; ADAR2). Endothelial cells (ECs) attract and guide leukocytes to sites of ischemic tissue injury. Here we studied the role of RNA editing in ischemic disease.

Methods

Primary human and murine vascular endothelial cell cultures were used to assess the EC responses to interleukin-6 (IL-6) or ischemia. For the animal studies, the effect of ADAR2 in acute and chronic ischemic disease was evaluated in cremaster muscle microcirculation by intravital microscopy, in peritoneal cavity after sterile peritonitis and in gastrocnemius muscle after hind-limb ischemia by 8-colour flow cytometry and immunohistochemistry (IHC) studies of Adar2−/−/tg as well as of i(nducible)EC-ADAR2 knockout (KO) mice. For the mechanistic studies, deep RNA sequencing, qRT-PCR, western blot, confocal microscopy, target-specific microRNA (miRNA) editing studies, RNA-immunoprecipitation, miRNA/plasmid silencing/overexpression and luciferase reporter assays were used among others. For human studies, ischemic tissues derived from patients with acute or chronic ischemic heart disease were processed.

Results

ADAR2, but not ADAR1, expression is induced by >2-fold in hypoxic ECs and in ischemic vascular ECs in mice and humans. Unbiased gene ontology analysis of the EC transcriptome indicated that ADAR2 controls inflammatory responses and predominantly the expression of interleukin-6-signal transducer (IL6ST), the co-receptor of IL-6. Subsequently, ADAR2 controls IL-6 trans-signalling in ECs as documented by the STAT3 phosphorylation and expression of the downstream leukocyte adhesion molecules, E-selectin and VCAM-1. IL-6-inflamed cremaster muscles showed that rolling and adhesion of leukocyte subsets to vascular wall were severely impaired in Adar2−/−/tg mice. Leukocyte transmigration was also diminished by >2-fold in Adar2−/−/tg and in iEC-ADAR2 KO mice in response to IL-6 or ischemia. Similar results were obtained for leukocyte rolling, adhesion and infiltration after acute (4h) and chronic (3d; 21d) ischemia from iEC-ADAR2 KO mice and human ischemic muscle tissues. Next we studied how ADAR2 controls IL6ST expression. ADAR2-deficient vascular EC miRNAome revealed the upregulation of a conserved group of miRNAs targeting the IL6ST mRNA including miR-199a-5p and miR-335-3p. At a single-nucleotide level, ADAR2-induced RNA editing of the stem loops of the primary miR-199a1/2 and miR-335 directly disrupted Drosha recruitment to both and thus inhibited their maturation process. Accordingly, rescue experiments using miRNA-inhibitors restored IL6ST levels after ADAR2 deficiency.

Conclusion

Taking together, inhibition of the microRNA maturation process by ADAR2-mediated RNA editing is integral for IL-6 trans-signalling in vascular endothelium and subsequent leukocyte trafficking to ischemic tissues in mice and humans.

P930Inflammatory leukocyte phenotypes are associated with increased mortality after transfemoral transcatheter aortic valve implantation

Background

Systemic inflammatory response syndrome (SIRS) was shown to be a strong predictor of mortality in patients undergoing transcatheter aortic valve implantation (TAVI). However, given the rather non-specific nature of the SIRS criteria and their limited applicability in the modern era of TAVI, including lower periprocedural complication rates and shorter hospitalization periods in experienced competence centers, there is a need for defining novel prognostic inflammatory signatures for improved patient risk stratification. Thus, the objective of the present study was to characterize and assess the prognostic relevance of circulating leukocyte subsets, including phenotypical heterogeneity of monocytes and effector T cells, before and at various times after transfemoral TAVI.

Methods and results

129 consecutive patients (59% male, mean age 82.3±5.6 years) with severe symptomatic aortic stenosis (Pmean 44.2±17mmHg), and high or prohibitive operative risk (mean EuroSCORE II 5.9; STS score 4.1) admitted to our clinic for TAVI were included into the study. Peripheral blood samples were obtained pre-procedurally (baseline, BL), directly after the intervention, and at 24h and 3 days after TAVI, and analyzed for inflammatory and cardiac biomarkers, including hs-CRP, IL-6, hs-TropT, and NT-proBNP. Differential myeloid and T-cell subset (Th1, Th2, Th17, Th1/Th17, Th22, Tregs) distribution and kinetics were analyzed using multiparameter flow cytometry. Neutrophil (P<0.001 vs. BL) as well as classical and intermediate monocyte counts were significantly elevated at 24h (both p<0.0001 vs. BL), whereas non-classical monocytosis developed 3 days after TAVI (P<0.0001 vs. BL). Among CD4+ T-cell subsets, the percentage of Tregs and Th17 significantly increased (both P<0.0001 at 24h vs. BL) after valve implantation. Remarkably, these changes were independent on the valve type (balloon- vs. self-expandable) and no significant effects of predilatation were observed (p>0.05 for all cell subsets). Univariate analysis showed that elevated levels of NT-proBNP (HR: 3.4, 95% CI: 1.7–6.8; P=0.0005), hsCRP (HR: 1.4, 95% CI: 1.2–1.7; P=0.0003), and IL-6 (HR: 1.0, 95% CI: 1.0–1.03; P=0.0007), lower counts of Th2 cells (HR: 0.94, 95% CI: 0.90–0.94; P=0.0045), as well as increased percentages of Th17 cells (HR: 1.2, 95% CI: 1.0–1.4; P=0.023), and of non-classical monocytes (HR=1.019, 95% CI: 1.001–1.039; P=0.049) were independently associated with 12-month all-cause mortality. When included in the regression model with STS score, these inflammatory biomarkers provided higher area under ROC curve and category-free net reclassification improvementof 59% at 1 year (P=0.0001).

ROC curves inflammation markers add STS

Conclusions

Our findings demonstrate for the first time an association of inflammatory leukocyte phenotypes with increased mortality after TAVI. Specific monocytic and T-cell signatures might therefore provide novel additive biomarkers to improve individual risk stratification in patients with severe aortic stenosis.

Phytotherapie bei entzündlichen Hauterkrankungen

In den letzten Jahren wurden einige neue pflanzliche Arzneimittel, Medizinprodukte und Hautpflegemittel für die topische Behandlung von entzündlichen Hauterkrankungen entwickelt. Besonders gut belegt ist die Wirksamkeit von Inhaltsstoffen aus dem Süßholz bei der atopischen Dermatitis und von Indigoextrakten bei der Psoriasis. Ein neuer vielversprechender Therapieansatz zur äußerlichen Behandlung einer geschädigten Hautbarriere sind Bitterstoffe, die an Bitterstoffrezeptoren der Haut binden und die Keratin- und Lipidsynthese der Keratinozyten anregen. Weitere pflanzliche Wirkstoffe für die Behandlung von Rosazea und Akne vulgaris werden ebenfalls besprochen.

Abstract P6-03-06: Androgen supplementation in patient derived xenografts in androgen receptor positive breast cancer to increase engraftment and growth rate

Background:

The European fund for regional development (EFRE) supported Precision Oncology and Personalized Therapy Prediction (POP) Project is establishing preclinical models to further the development of personalized therapy options. In the subgroup breast cancer the current goal is to increase the growth and engraftment rates of breast cancer patient derived xenografts (PDX) models.

Methods:

Breast cancer patients of the Department of Gynecology with Breast Center Charité Universitätsmedizin Berlin, Germany are recruited since May 2017. In total 29 tissue samples were collected and included so far.

Treatment naive and treatment refractory patients, tripple negative breast cancer (TNBC), hormone receptor positive (HR+) and Her2 postivie tumors, primary disease, recurrence or metastasis are sampled. Fresh tumor tissue is extracted via surgery or biopsy. The materials are then implanted into female immunodeficient NOG mice. To establish PDX models for HR+ breast cancer the mice received estrogen supplementation.

To increase engraftment and growth rates androgen receptor (AR) testing and subsequently androgen replacement was started since April 2018.

Up to date, 6 new samples have been collected. One HR+ and two TNBC samples tested also positive for AR. These samples are currently in passage 0 (p0) and are now supplied with androgens to increase engraftment and growth rate. One already established AR+ TNBC PDX is being regrown with androgen supplementation to compare growth rates.

Results:

Out of the initial 23 tissue samples ten (six HR+ and four TNBC) have been able to be engrafted into PDX mice.

The TNBC PDX models are one in p1, one in p2, one in p3 and one is being tested with systemic therapy. Engraftment time in p1 were between 19 and 97 days. Growth time to passagable size between 21 and 112 days.

The HR+ PDX models are four in p1 and two in p2. Engraftment time in p1 was between 26 and 123 days. Growth time to passagable size has been achieved in 2 HR+ PDX within 17 to 48 days.

The engraftment/growth rates and times of the androgen supplemented PDX models will be presented.

Conclusion:

Breast cancer growths in humans slowly and this is also the case in the PDX models. To achieve faster growth and higher engraftment rates androgen supplementation in AR+ breast cancer might be an additional enhancive factor.

Citation Format: Kiver VII, Wulf-Goldenberg A, Jurmeister PS, Schweiger C, Gorea O, Hoffmann J, Denkert C, Keilholz U, Liedtke C, Blohmer J-U. Androgen supplementation in patient derived xenografts in androgen receptor positive breast cancer to increase engraftment and growth rate [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-03-06.

Long-term donor site morbidity in head and neck cancer patients and its impact on quality of life: a cross-sectional study

Modern head and neck reconstructive surgery offers a multitude of different reconstructive options. In such cases, donor site morbidity is an important factor in the affected patient's decision-making. The aim of this study was to perform an objective comparison of donor site morbidity for the five most frequent microvascular donor sites in head and neck reconstructive surgery (radial forearm, anterolateral thigh, fibula, iliac crest, and scapula) using a uniform testing system. In this cross-sectional study, 117 donor sites were analyzed (106 for malignant disease and 11 for non-malignant disease): 73 radial forearm, 14 scapula, 12 anterolateral thigh, 10 fibula, and eight iliac crest. Testing consisted of range of motion, muscle strength, and sensation. The non-affected side served as the control. Quality of life was assessed using the Washington Quality of Life Questionnaire version 4 in its German translation. Range of motion was restricted in 15 cases (12.8%). Muscle strength was decreased in 58 cases (49.6%). Sensation was reduced in 70 cases (60%). Concerning quality of life, 31.2% of patients were limited in their daily activities. The scapula flap showed the highest incidence of overall donor site morbidity. However, correlation between objective and subjective donor site impairment was weak and the majority of patients experienced only minor limitations.

The impact of a cervical dysplasia diagnosis on individual cancer prevention habits over time: a bicentric case-control study

PURPOSE

Annual cervical cancer screening is recommended in Germany as a part of the statutory preventive care. Abnormal results can provoke psychological distress and anxiety, compromising women's adherence. Little is known about how a cervical dysplasia impacts adherence follow-up visits and prevention habits over time. To optimize care strategies, this study aims to identify women at risk for nonadherence to follow-up visits after a screening event.

METHODS

Between November 2015 and May 2017, participants with an abnormal Pap smear at the Heidelberg and Leipzig University Hospitals received a four-part questionnaire (sociodemographic data, PHQ-D, self-designed fear and prevention habit questions) at the first consultation (T1) and subsequently after 3 (T2) and 6 (T3) months; healthy controls completed the questionnaire at T1.

RESULTS

132 women with an abnormal Pap smear [with conization: S1 (n = 68, 51.5%), without intervention: S2 (n = 64, 48.5%)] and healthy controls (K, n = 101) generally adhered to gynecological checkups, except S1 6 months after the first diagnosis (S1/T3 - 0.47, signed rank p < 0.0005). Knowledge of primary prevention information, i.e., HPV vaccination, was significantly higher among K (K 58%, S1 29%, S2 44%, Chi-squared p = 0.01) as was vaccine uptake (K 39% versus S1/S2 7% and 17%, respectively, Chi-squared p = 0.0004). Fear of upcoming Pap smears rose significantly over time (S1/T1-S1/T2-S1/T3, Wilcoxon signed-rank test p < 0.001) and was higher among those with conization at T2 (Chi-square test, p = 0.01) and partially accompanied by panic disorders at T1 (Chi-square test p = 0.035). Realization of general preventive habits rose significantly among women without an operative procedure (S2) over the study.

CONCLUSION

This study advances the understanding of non-participation in follow-up visits after a dysplasia diagnosis, identifying post-conization women as a special risk group for decreased adherence.

Toward genome editing in X-linked RP-development of a mouse model with specific treatment relevant features

Genome editing represents a powerful tool to treat inherited disorders. Highly specific endonucleases induce a DNA double strand break near the mutant site, which is subsequently repaired by cellular DNA repair mechanisms that involve the presence of a wild type template DNA. In vivo applications of this strategy are still rare, in part due to the absence of appropriate animal models carrying human disease mutations and knowledge of the efficient targeting of endonucleases. Here we report the generation and characterization of a new mouse model for X-linked retinitis pigmentosa (XLRP) carrying a point mutation in the mutational hotspot exon ORF15 of the RPGR gene as well as a recognition site for the homing endonuclease I-SceI. Presence of the genomic modifications was verified at the RNA and protein levels. The mutant protein was observed at low levels. Optical coherence tomography studies revealed a slowly progressive retinal degeneration with photoreceptor loss starting at 9 months of age, paralleling the onset of functional deficits as seen in the electroretinogram. Early changes to the outer retinal bands can be used as biomarker during treatment applications. We further show for the first time efficient targeting using the I-SceI enzyme at the genomic locus in a proof of concept in photoreceptors following adeno-associated virus mediated gene transfer in vivo. Taken together, our studies not only provide a human-XLRP disease model but also act as a platform to design genome editing technology for retinal degenerative diseases using the currently available endonucleases.