LINC00599 expression analysis in hypoxic PH models

PRIMARY OUTCOME

LINC00599 expression levels

EXPECTED OUTCOMES

- 1. Chronic hypoxic mice develop pulmonary hypertension with RVSP >35 mmHg (vs <25 mmHg in controls) and Fulton index >0.35 (vs <0.25 in controls) - 2. LINC00599 expression increases 3-5 fold in hypoxic lung tissues compared to normoxic controls, with statistical significance p<0.01 - 3. Cultured PASMCs show 2-4 fold upregulation of LINC00599 after 24-48 hours of hypoxic treatment (1% O2) compared to normoxic conditions - 4. In situ hybridization reveals predominant LINC00599 expression in the medial layer of remodeled pulmonary arteries with minimal signal in normoxic vessels - 5. Strong correlation (r>0.6) between LINC00599 expression levels and hemodynamic parameters of pulmonary hypertension severity - 6. Time-dependent increase in LINC00599 expression in hypoxic PASMCs, with peak expression at 48 hours post-hypoxic exposure - 7. Specificity of upregulation to pulmonary vascular smooth muscle cells, with minimal changes in other lung cell types or systemic vessels

SUCCESS CRITERIA

- • Hypoxic model validation: RVSP >30 mmHg and Fulton index >0.3 in >80% of hypoxic mice with significant difference from controls (p<0.001, unpaired t-test) - • LINC00599 upregulation: >2-fold increase in hypoxic conditions vs controls in both in vivo and in vitro models (p<0.01, Mann-Whitney test) - • Technical quality: RNA RIN scores >7.0 for all samples, qRT-PCR efficiency 90-110% with standard curve R²>0.99, Ct values <35 for target gene - • Reproducibility: Consistent results across minimum 3 independent hypoxic exposures with similar fold-changes (CV <30%) - • Localization specificity: Clear ISH signal in pulmonary arterial media with >3-fold higher intensity than background in hypoxic samples - • Dose-response relationship: Significant correlation between hypoxic exposure duration and LINC00599 expression levels (r>0.5, p<0.05) - • Statistical power: Achieved power >0.8 for detecting 2-fold expression changes with planned sample sizes (n=12 per group)

PROTOCOL

**Phase 1: Hypoxic Mouse Model Establishment** -- Days 1-21 Establish chronic hypoxic pulmonary hypertension model using 8-10 week old C57BL/6J mice (n=12 per group). House mice in normobaric hypoxic chambers maintained at 10% O2 for 21 days with continuous monitoring of O2 levels. Include normoxic controls maintained at room air (21% O2). Monitor body weight and general health twice daily. Measure right ventricular systolic pressure (RVSP) using closed-chest catheterization technique with 1.4F pressure catheter (Millar Instruments) under isoflurane anesthesia on day 21. Calculate Fulton index (RV/LV+S weight ratio) after sacrifice. **Phase 2: Tissue Collection and Processing** -- Days 22-23 Sacrifice mice by CO2 asphyxiation followed by cervical dislocation. Rapidly harvest lung tissues and snap-freeze in liquid nitrogen for RNA extraction. Collect separate lung lobes for histological analysis (fix in 4% paraformaldehyde for 24 hours, then paraffin embedding). Dissect pulmonary arteries when possible for vessel-specific analysis. Store all samples at appropriate temperatures (-80°C for RNA, room temperature for paraffin blocks) until processing. **Phase 3: Primary PASMC Culture and Hypoxic Treatment** -- Days 24-35 Isolate primary pulmonary arterial smooth muscle cells (PASMCs) from normoxic mouse lungs using enzymatic digestion method. Digest minced lung tissue with collagenase I (1 mg/mL) and elastase (0.5 mg/mL) for 45 minutes at 37°C. Culture cells in DMEM with 10% FBS and characterize by smooth muscle α-actin staining. Use PASMCs between passages 3-6 for experiments. Treat confluent cells with either normoxia (21% O2) or hypoxia (1% O2) for 24 and 48 hours using hypoxic incubator (n=6 wells per condition per timepoint). **Phase 4: RNA Extraction and Quality Control** -- Days 36-38 Extract total RNA from frozen lung tissues using TRIzol reagent (Invitrogen) following manufacturer's protocol. Homogenize tissues using TissueLyser II (Qiagen) with stainless steel beads. For cultured PASMCs, extract RNA directly from culture wells. Assess RNA quality using Agilent 2100 Bioanalyzer, requiring RIN scores >7.0 for downstream analysis. Quantify RNA concentration using NanoDrop spectrophotometer. Prepare RNA samples at 100 ng/μL for qRT-PCR analysis. **Phase 5: LINC00599 Expression Quantification** -- Days 39-42 Perform quantitative RT-PCR using TaqMan assays specific for mouse LINC00599 (design custom probe if commercial unavailable). Use 18S rRNA and GAPDH as housekeeping genes for normalization. Prepare cDNA from 1 μg total RNA using High-Capacity cDNA Reverse Transcription Kit (Applied Biosystems). Run qRT-PCR in triplicate on QuantStudio 7 Flex system with the following cycling conditions: 50°C for 2 min, 95°C for 10 min, then 40 cycles of 95°C for 15 sec and 60°C for 1 min. Calculate relative expression using ΔΔCt method. **Phase 6: Histological Localization and Validation** -- Days 43-49 Perform in situ hybridization (ISH) on paraffin-embedded lung sections to localize LINC00599 expression. Design and synthesize DIG-labeled antisense and sense (control) RNA probes targeting LINC00599. Use standard ISH protocol with proteinase K treatment, hybridization at 65°C overnight, and anti-DIG antibody detection. Counterstain with hematoxylin. Image sections using brightfield microscopy and quantify signal intensity in pulmonary arterial medial layers using ImageJ software. Perform immunofluorescence co-staining with smooth muscle α-actin to confirm cell-type specificity.

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