CLCF1 Exercise-induced Myokine Protocol for Investigating RANKL/OPG Bone Protection Mechanisms in Postmenopausal Osteoporosis

Summary

This article presents a comprehensive protocol for investigating cardiotrophin-like cytokine factor 1 (CLCF1) as an exercise-induced mediator of bone protection through RANKL/OPG axis modulation in postmenopausal osteoporosis.

Abstract

Recent studies have identified cardiotrophin-like cytokine factor 1 (CLCF1) as an exercise-induced "youth molecule" that mediates musculoskeletal benefits, but declines with age. This protocol describes a systematic approach to investigate CLCF1's regulatory role in exercise-mediated bone protection via immune-bone crosstalk mechanisms. The methodology encompasses clinical sample analysis, molecular characterization techniques, and functional assays to elucidate CLCF1's influence on the receptor activator of the nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) signaling axis. Through quantitative polymerase chain reaction (qPCR), western blotting, CRISPR/Cas9 gene editing, and co-culture systems, this protocol demonstrates CLCF1's dual bone-protective actions via STAT1-mediated osteoclast inhibition and STAT3-mediated osteoblast promotion. The described methods enable the comprehensive assessment of CLCF1 expression patterns, correlation analyses with bone mineral density parameters, and mechanistic evaluation of potential exercise-mimetic treatment interventions. Unlike traditional antiresorptive therapies that primarily target osteoclasts, CLCF1-based interventions may offer the unique advantage of simultaneously promoting bone formation while inhibiting resorption. This protocol provides researchers with standardized procedures to investigate exercise-induced cytokine-mediated regulation of bone metabolism and facilitates the development of targeted therapeutic interventions for age-related bone disorders.

Introduction

Postmenopausal osteoporosis (PMOP) represents a paradigmatic example of age-related musculoskeletal decline in which immune system dysregulation precipitates pathological bone loss^1,2,3. Although exercise is widely recognized as the most effective non-pharmacological intervention for preventing age-related bone deterioration, the precise molecular mechanisms underlying exercise-induced bone protection have remained elusive until recently⁴. The contemporary understanding of bone metabolism has evolved beyond traditional endocrinological frameworks to encompass complex osteoimmune interactions and exercise-induced myokines that govern skeletal homeostasis⁵.

The recent identification of cardiotrophin-like cytokine factor 1 (CLCF1) as an exercise-induced factor that combats age-related musculoskeletal decline represents a paradigm shift in understanding bone-muscle crosstalk⁶. This groundbreaking discovery explains the well-established bone-protective effects of exercise through a previously unknown molecular mechanism, positioning CLCF1 as the key mediator of exercise-induced osteoanabolism⁷. Transgenic mice overexpressing CLCF1 demonstrated enhanced bone formation, improved glucose tolerance, and superior physical performance compared to wild-type controls⁶, suggesting that CLCF1 supplementation could potentially mimic exercise benefits in sedentary or mobility-impaired populations.

Exercise-mimetic treatment is defined as pharmacological interventions that replicate exercise-induced CLCF1 kinetics, providing therapeutic benefits similar to physical activity through molecular pathways⁸. Cardiotrophin-like cytokine factor 1 (CLCF1), alternatively designated as neurotrophin-1 (NNT-1) or B-cell stimulatory factor-3 (BSF-3), belongs to the interleukin-6 (IL-6) cytokine superfamily and exhibits pleiotropic biological functions⁸. Originally characterized for its neurotrophic properties in spinal motor neuron survival and development, CLCF1's role as an exercise-induced myokine has emerged as a significant area of investigation. Recent clinical studies have validated CLCF1 as a biomarker for bone health status, demonstrating that CLCF1 protein levels in peripheral blood mononuclear cells are significantly decreased in postmenopausal women with osteoporosis compared with healthy controls⁹. These studies showed positive correlations between CLCF1 expression and bone mineral density at multiple skeletal sites, providing clinical validation that strengthens the translational potential of CLCF1-targeted therapeutic interventions.

The cytokines operate through heteromeric receptor complexes, including soluble ciliary neurotrophic factor receptors (sCNTFR) and cytokine receptor-like factor-1 (CRLF-1), to orchestrate diverse cellular responses^10,11. Recent mechanistic studies have elucidated the dual signaling paradigm whereby CLCF1 simultaneously inhibits bone resorption and promotes bone formation^2,6,7,9. This dual action occurs through differential signal transducer and activator of transcription (STAT) pathway activation: STAT1 phosphorylation mediates osteoclast suppression by interfering with receptor activator of the nuclear factor-κB ligand (RANKL)-induced nuclear factor-κB (NF-κB) signaling, whereas STAT3 activation in osteoblasts promotes the expression of bone formation markers, including alkaline phosphatase and osteocalcin.

Understanding how acute exercise responses translate to chronic bone adaptations remains critical for therapeutic development¹³. While acute CLCF1 elevation following single exercise bouts provides mechanistic insights, repeated acute responses over weeks to months may lead to sustained bone-protective effects through cumulative signaling and cellular adaptations¹⁴.

The rationale for investigating CLCF1 in osteoimmune pathophysiology stems from its established role in B-lymphocyte regulation and recognition that B cells constitute significant producers of both RANKL and osteoprotegerin (OPG)^12,13. The receptor activator of the nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) axis serves as the central regulatory mechanism for osteoclast differentiation and bone resorption^14,15. Unlike other IL-6 family members that have demonstrated regulatory control over skeletal homeostasis through bone remodeling modulation, CLCF1's unique dual bone-protective mechanism offers superior therapeutic potential^16,17,18.

The advantages of this protocol over existing methodologies include its comprehensive approach to exercise osteoimmune investigation, incorporating both clinical correlation analysis and mechanistic cellular studies to provide translational insights into CLCF1-mediated bone metabolism regulation. The clinical relevance of this protocol is further enhanced by emerging evidence that CLCF1 levels can be modulated through lifestyle interventions, positioning it as an actionable therapeutic target for age-related bone disorders.

Protocol

This protocol has been approved by the institutional research ethics committee (Protocol #2024-CHSD-0156) and adheres to the Declaration of Helsinki principles. All animal procedures complied with the institutional animal care and use committee guidelines (Protocol #2024-037). All the participants provided written informed consent.

1. Clinical sample collection and exercise intervention assessment

1. Participant recruitment and exercise history evaluation
   1. Recruit postmenopausal women aged 55-75 years with a minimum 1-year postmenopausal duration.
   2. Assess detailed exercise history, including frequency, intensity, type, and duration of physical activity over the past 6 months using standardized physical activity questionnaires.
   3. Categorize participants into sedentary (< 150 min/week), moderately active (150-300 min/week), and highly active (> 300 min/week) groups based on WHO exercise guidelines.
   4. Perform comprehensive medical history assessment and physical examination, including medication review and comorbidity screening.
   5. Obtain dual-energy X-ray absorptiometry (DXA) measurements using Hologic Discovery A densitometer with APEX software v4.5. Perform daily calibration with the spine phantom. Position the patient supine with legs elevated on a positioning block per International Society for Clinical Densitometry (ISCD) guidelines.
   6. Classify participants according to World Health Organization osteoporosis criteria (T-score ≤ -2.5 SD).
   7. Apply exclusion criteria: Prior anti-osteoporotic therapy within 12 months, immunosuppressive treatments, metabolic bone diseases, secondary osteoporosis, or contraindications to exercise testing.
2. Exercise-induced CLCF1 response assessment
   1. Collect baseline blood samples between 8:00-10:00 AM following 12 h overnight fasting in EDTA tubes.
   2. Implement standardized acute exercise protocol: 45 min moderate-intensity walking at 65-70 % maximum heart rate. Calculate maximum heart rate using the Karvonen formula (220 age)¹⁹. Perform exercise on a motorized treadmill with continuous heart rate monitoring via a chest strap monitor. Maintain walking speed at 3.5-4.5 km/h with grade adjustment to achieve the target heart rate.
   3. Collect post-exercise blood samples at 1 h, 4 h, and 24 h time points to assess CLCF1 kinetics, maintaining consistent collection conditions.
   4. Store serum aliquots at -80 °C for subsequent CLCF1 quantification. Use Human CLCF1 ELISA Kit with a detection range of 31.2-2000 pg/mL. Dilute samples 1:2 in assay diluent. Prepare a 7-point standard curve using 2-fold serial dilutions. Run samples in duplicate. Read plates at 450 nm with 540 nm wavelength correction. Accept coefficient of variation (CV) < 20 % between duplicates.
3. Longitudinal exercise intervention protocol
   1. Design a 12-week progressive exercise program with three sessions per week.
   2. Collect blood samples at baseline, 4, 8, and 12 weeks for CLCF1 trajectory analysis.
   3. Assess fitness improvements using VO2 max testing at baseline and endpoint.
   4. Correlate CLCF1 changes with BMD improvements measured by DXA at 12 weeks.
   5. Document training adaptations, including exercise tolerance and recovery patterns.

2. Enhanced peripheral blood mononuclear cell (PBMC) isolation and processing

1. Optimized PBMC isolation for CLCF1 analysis
   1. Collect 20 mL of venous blood samples in EDTA-containing tubes (5 mL EDTA per tube) under sterile conditions.
   2. Process samples within 2 h of collection for optimal cell viability and CLCF1 expression preservation.
      1. Dilute blood samples 1:1 with phosphate-buffered saline (PBS) at room temperature. Mix 20 mL of blood with 20 mL of PBS.
      2. Layer diluted blood over density gradient medium in 50 mL conical tubes. Use 15 mL density gradient medium per 20 mL diluted blood (1:1.33 ratio).
   3. Centrifuge at 400 × g for 30 min at room temperature without brake.
   4. Carefully aspirate the PBMC layer at the plasma-Ficoll interface using a sterile Pasteur pipette.
   5. Wash the cells twice with PBS containing 2% fetal bovine serum (FBS) by centrifugation at 300 × g for 10 min.
2. Cell viability assessment and CLCF1 baseline measurement
   1. Determine cell viability using the trypan blue exclusion method (target > 95% viability)²⁰.
   2. Assess baseline intracellular CLCF1 expression immediately after isolation.
   3. Adjust cell concentration to 1 × 10⁶ cells/mL in appropriate medium.
   4. Allocate cells for downstream applications or store in liquid nitrogen. Freeze PBMCs in freezing medium containing 90% FBS + 10% DMSO. Use a controlled-rate freezing container at -1 °C/min to -80 °C. Store 1 mL aliquots (5 × 10⁶ cells/vial) in cryovials.

3. Comprehensive quantitative gene expression analysis

1. RNA Extraction and purification with CLCF1-specific considerations
   1. Lyse 1 × 10⁶ PBMCs in 1 mL of RNA lysis reagent within 1 h of isolation.
   2. Add 200 µL of chloroform, vortex vigorously, and incubate for 3 min at room temperature.
   3. Centrifuge at 12,000 × g for 15 min at 4 °C to achieve phase separation.
   4. Transfer aqueous phase to a fresh tube, add an equal volume of isopropanol.
   5. Precipitate RNA by centrifugation at 12,000 × g for 10 min at 4 °C.
   6. Wash RNA pellet with 75% ethanol, air-dry, and dissolve in nuclease-free water.
   7. Assess RNA integrity using agarose gel electrophoresis or bioanalyzer (target RIN >7.0).
2. Reverse transcription and quantitative PCR with updated primer sets
   1. Quantify RNA concentration using spectrophotometric analysis (target A260/A280 ratio 1.8-2.2).
   2. Perform reverse transcription using 1 µg of total RNA with the reverse transcription reagent kit.
   3. Prepare qPCR reactions: Prepare 20 µL reactions containing 10 µL of Master Mix, 0.8 µL of each primer (10 µM stock, final 400 nM), 2 µL of cDNA template (50 ng), 6.4 µL of nuclease-free water. Run triplicates. Use a real-time PCR system.
   4. Use validated primer sequences:
      1. CLCF1 forward: 5'-CCTCCTGCTTCTTGCCTACC-3',
         reverse: 5'-TGCCACCATGTTTGTTTCCT-3'
      2. CRLF1 forward: 5'-TGAAGCTCATCCTGCAGTTC-3',
         reverse: 5'-CAGCATCTCCTCCTTGATGC-3'
      3. STAT1 forward: 5'-CAGCTTCAGCAGCTTGACTC-3',
         reverse: 5'-AAGGTCAGCGATGTCTTCAG-3'
      4. STAT3 forward: 5'-CAGCAGCTTGACACACGGTA-3',
         reverse: 5'-AAACACCAAAGTGGCATGTGA-3'
   5. Execute qPCR protocol: 95 °C for 10 min, followed by 40 cycles of 95 °C for 15 s and 60 °C for 1 min.
   6. Analyze results using 2^(-ΔΔCt) method with β-actin normalization²¹.
3. Exercise-response gene panel analysis
   1. Include exercise-responsive genes: IL-6, TNF-α, IL-1β, BDNF, IGF-1, and myostatin.
   2. Use validated primer sequences:
      1. IL-6 forward: 5'-AGCCACTCACCTCTTCAGAAC-3',
         reverse: 5'-GCCTCTTTGCTGCTTTCACAC-3';
      2. TNF-α forward: 5'-CCCAGGGACCTCTCTCTAATC-3',
         reverse: 5'-ATGGGCTACAGGCTTGTCACT-3';
      3. IL-1β forward: 5'-ACAGATGAAGTGCTCCTTCCA-3',
         reverse: 5'-GTCGGAGATTCGTAGCTGGAT-3';
      4. BDNF forward: 5'-TAACATGGCTGCGCGTGTGT-3',
         reverse: 5'-CGAGTGGGTCACAGCGGCAG-3';
      5. IGF-1 forward: 5'-GCTCTTCAGTTCGTGTGTGGA-3',
         reverse: 5'-GCCTCCTTAGATCACAGCTCC-3';
      6. Myostatin forward: 5'-AGTGACGGGCTCTTTGGAAGA-3',
         reverse: 5'-GTTTCAGAGGCCGGTCAAGT-3'.
   3. Correlate exercise-induced changes in CLCF1 with other myokine expression patterns.
   4. Assess CLCF1/CRLF1 co-expression ratios as indicators of functional cytokine complex formation.

4. Enhanced protein expression analysis with STAT pathway focus

1. Protein extraction and quantification for STAT analysis
   1. Lyse PBMCs in lysis buffer (150 mM NaCl, 1% NP-40, 0.5% sodium deoxycholate, 0.1% SDS, 50 mM Tris-HCl pH 8.0) supplemented with protease and phosphatase inhibitor cocktails.
   2. Add some specific phosphatase inhibitors: sodium orthovanadate (1 mM) and sodium fluoride (50 mM) immediately before use.
   3. Incubate lysates on ice for 30 min with periodic vortexing at medium speed every 10 min.
   4. Centrifuge at 12,000 × g for 15 min at 4 °C to remove cellular debris.
   5. Quantify protein concentration using Bradford assay or BCA method²².
   6. Adjust protein concentrations to 2 µg/µL in a sample buffer and store at -80 °C until further analysis for western blotting applications.
2. Comprehensive western blot analysis with STAT signaling focus
   1. Prepare 10 mL of 10% SDS-PAGE gels using standard acrylamide/bisacrylamide solutions.
   2. Load 20 µg of protein per lane alongside pre-stained molecular weight markers and resolve at 120 V for 90 min.
   3. Transfer proteins to PVDF membranes at 100 V for 2 h at 4 °C using transfer buffer (25 mM Tris, 192 mM glycine, 20% methanol).
   4. Block membranes with 50 mL of 5% non-fat dry milk in Tris-buffered saline with 0.1% Tween-20 (TBST).
   5. Incubate with primary antibodies overnight at 4 °C: Anti-CLCF1 (1:1,000); Anti-CRLF1 (1:1,000); Anti-OPG (1:1,000); Anti-RANKL (1:1,000); Anti-JAK2 (1:1,000); Anti-phospho-JAK2 (Tyr1007/1008, 1:1,000); Anti-STAT1 (1:1,000); Anti-phospho-STAT1 (Tyr701, 1:1,000); Anti-STAT3 (1:1,000); Anti-phospho-STAT3 (Tyr705, 1:1,000); Anti-β-actin (1:1,000)
   6. Wash membranes 3 times for 10 min each with 15 mL of TBST. Incubate with appropriate secondary antibodies for 1 h at room temperature.
   7. Detect protein bands using enhanced chemiluminescence substrate. Image using chemiluminescence imaging system with automatic exposure optimization. Quantify using densitometric analysis with ImageJ v1.53 gel analysis tool.
3. STAT1/STAT3 dual pathway analysis
   1. Calculate phospho-STAT1/total STAT1 and phospho-STAT3/total STAT3 ratios using ImageJ/Fiji software version 1.54f.
   2. Assess STAT1/STAT3 activation balance as indicator of CLCF1 functional activity.
   3. Correlate STAT activation patterns with RANKL/OPG expression ratios.
   4. Assess STAT1/STAT3 phosphorylation via Western blot at 0, 15, 30, 60, 120, and 240 min post-CLCF1 treatment. Normalize phospho-protein to total protein levels using densitometry.

5. Advanced CRISPR/Cas9-mediated gene knockout with validation

1. Enhanced lentiviral vector construction
   1. Design single-guide RNA (sgRNA) targeting CLCF1 gene sequence:
      TTGAAGTCTGGCTCGTTGAA-3'.
   2. Include additional sgRNA sequences for improved knockout efficiency:
      GCTTGAACGAGCCAGACTTC-3'.
   3. Clone sgRNAs into lentiviral vector using standard molecular cloning techniques.
   4. Verify construct integrity through DNA sequencing analysis.
   5. Assess sgRNA cutting efficiency using the T7 endonuclease I assay²³.
   6. Include pathway specificity validation using inhibitors: AG490 (JAK2, 50 µM), fludarabine (STAT1, 10 µM), and Stattic (STAT3, 5 µM).
   7. Perform rescue experiments using constitutively active STAT constructs to validate pathway necessity.
2. Optimized lentiviral transduction protocol
   1. Culture Raji cells in RPMI-1640 medium (500 mL) supplemented with 10% FBS. Maintain all cell cultures at 37 °C in a humidified incubator with 5% CO₂. Pre-equilibrate culture media for at least 30 min before use.
   2. Pre-treat cells with polybrene (8 µg/mL) to enhance transduction efficiency.
   3. Produce lentivirus using HEK293T cells with packaging and envelope plasmids via calcium phosphate transfection. Determine titer by p24 ELISA (> 10⁸ TU/mL required). Follow BSL-2 containment procedures²³.
   4. Transduce cells with lentivirus at a multiplicity of infection (MOI) of 100. Change media 24 h post-transduction. Select transduced cells using puromycin (4 µg/mL) for 7 days, then amplify a 500 bp region spanning the target site using the following PCR conditions: initial denaturation at 95 °C for 3 min, followed by 35 cycles of denaturation at 95 °C for 30 s, annealing at 60 °C for 30 s, and extension at 72 °C for 30 s, with a final extension at 72 °C for 5 min. For the T7 endonuclease assay, denature and reanneal the PCR products, digest with T7E1 endonuclease for 30 min at 37 °C, then analyze the products on a 2% agarose gel.
   5. Validate the gene knockout efficiency through western blotting and Sanger sequencing^24,25.
   6. Perform off-target analysis using GUIDE-seq or similar methodology²⁶.
      NOTE: Recent evidence demonstrates that CLCF1 secretion efficiency requires co-expression with CRLF1 chaperone protein. Consider dual knockout approaches for complete functional ablation²⁷.

6. Comprehensive co-culture system with exercise mimetics

NOTE: For translational validation, adapt to ovariectomized mouse models by administering rhCLCF1 at 10 µg/kg i.p. daily for 4 weeks, assessing BMD via micro-CT.

1. Advanced Raji-MG-63 co-culture setup
   1. Seed MG-63 osteoblast-like cells in 24-well plate lower chambers at a density of 2 × 10⁴ cells/well in a humidified incubator at 37 °C with 5% CO₂ and 95% humidity. Pre-equilibrate media in the incubator for 30 min before use. For enhanced translation, substitute with primary human osteoblasts (density 1 × 10⁴/well) from commercial sources.
   2. Place 0.4 µm pore size membrane inserts in wells containing MG-63 cells.
   3. Seed Raji cells (wild-type, CLCF1-knockout, or CLCF1-overexpressing) in upper chambers at density of 1 × 10⁵ cells/well.
   4. Maintain co-cultures in complete RPMI-1640 medium (2 mL in lower chamber, 1.5 mL in upper chamber) for specified experimental periods (7, 14, 21 days) at 37 °C with 5% CO₂.
   5. Include recombinant CLCF1 (5-10 ng/mL) treatment groups to assess dose-response relationships.
2. Exercise-mimetic CLCF1 treatment protocol
   1. Treat co-culture systems with physiological concentrations of recombinant CLCF1 (5-10 ng/mL) based on exercise-induced levels.
   2. Apply pulsatile CLCF1 treatment regimen: Apply CLCF1 for 2 h pulses at 0, 8, and 16 h on day 1, followed by continuous exposure for 24 h, then repeat cycle. Total treatment duration: 7 days with 9 total pulses.
   3. Assess time-dependent effects at 1 h, 4 h, 24 h, and 7 days post-treatment.
   4. Monitor STAT1/STAT3 phosphorylation kinetics in both cell populations via Western blot at 0, 15, 30, 60 min. Lyse cells in buffer (500 µL) with inhibitors, normalize to total STAT1/3 and β-actin.
3. Enhanced osteogenic differentiation assessment
   1. Induce osteogenic differentiation using standard osteogenic medium containing ascorbic acid (50 µg/mL), β-glycerophosphate (10 mM), and dexamethasone (10 nM). Change osteogenic medium every 3 days (2 mL lower chamber, 1.5 mL upper chamber). Prepare fresh ascorbic acid solution for each change; β-glycerophosphate and dexamethasone remain stable.
   2. Assess alkaline phosphatase (ALP) activity using colorimetric enzyme assay at days 7, 14, and 21²⁸. Use 500 µL of extraction volume. Read at 405 nm. Normalize to total protein content. Expected color range: light yellow (low) to dark yellow (high).
   3. Evaluate calcium deposition through Alizarin Red S staining and quantification at day 21. Extract with 500 µL of cetylpyridinium chloride, read at 540 nm, expected color range: light pink (low mineralization) to dark red (high mineralization).
   4. Quantify mineralization by measuring absorbance at 540 nm after cetylpyridinium chloride extraction.
   5. Analyze osteogenic gene expression: RUNX2, ALP, COL1A1, OCN, and OPGusing qPCR protocols described in step 3.2.
   6. Assess osteoclast-related markers: TRAP, cathepsin K, and RANKL in MG-63 cells.

7. Advanced statistical analysis and data interpretation

1. Comprehensive statistical methodology
   1. Perform normality testing using Shapiro-Wilk test for all continuous variables²⁹. Use non-parametric tests when normality assumptions are violated (p < 0.05).
   2. Apply Mann-Whitney U test for non-parametric comparisons between groups³⁰.
   3. Conduct Spearman correlation analysis for association studies between CLCF1 levels and clinical parameters³¹.
   4. Perform multiple regression analysis to assess independent predictors of BMD.
   5. Use repeated measures ANOVA for exercise intervention time-course analysis³².
   6. Apply Bonferroni correction for multiple comparisons³³.
   7. Set statistical significance threshold at p < 0.05 for all analyses.
2. Enhanced data presentation and analysis
   1. Present continuous data as mean ± standard deviation or median with interquartile range.
   2. Create correlation plots for CLCF1 expression versus BMD, lymphocyte counts, and exercise parameters using GraphPad Prism v9 for stats, ImageJ v1.53 for densitometry. No custom scripts are needed. Generate ROC via Prism's built-in tool; correlations via Spearman in Prism.
   3. Generate time-course plots for exercise-induced CLCF1 response kinetics.
   4. Develop receiver operating characteristic (ROC) curves for CLCF1 as an osteoporosis biomarker.
      NOTE: Representative western blot images were created using quantitative densitometric analysis.

Results

Implementation of this protocol successfully demonstrates CLCF1's regulatory role in immune-mediated bone metabolism using multiple experimental approaches. The clinical validation studies show significant downregulation of CLCF1 expression in PMOP patients compared to healthy controls, as demonstrated in Figure 1A, quantitative PCR analysis of peripheral blood mononuclear cells demonstrated that relative CLCF1 mRNA levels were markedly reduced in the PMOP gr...

Discussion

The protocol described herein provides a comprehensive methodological framework for investigating CLCF1's role as an exercise-induced mediator of bone protection through a systematic analysis of the RANKL/OPG axis. Recent breakthrough research has identified CLCF1 as an exercise-induced factor that combats age-related musculoskeletal decline, positioning it as a central mediator of exercise-induced bone protection^34,35,36. T...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Cell Culture Media & Reagents
Dimethyl Sulfoxide (DMSO)	Sigma-Aldrich	D2650	Purpose_Application:  Cryopreservation medium component Specifications_Comments: Molecular biology grade, sterile filtered
DMEM medium	Thermo Fisher Scientific	11965092	Purpose_Application:  MG-63 osteoblast culture medium Specifications_Comments: High glucose formulation with L-glutamine
Fetal Bovine Serum (FBS)	Thermo Fisher Scientific	16000044	Purpose_Application:  Cell culture supplement (heat-inactivated) Specifications_Comments: Heat-inactivated at 56°C for 30 min
Penicillin-Streptomycin	Thermo Fisher Scientific	15140122	Purpose_Application:  Antibiotic supplement for sterile culture Specifications_Comments: 100X stock, final concentration 1%
Polybrene (Hexadimethrine bromide)	Santa Cruz Biotechnology	sc-134220	Purpose_Application:  Lentiviral transduction enhancer Specifications_Comments: 8 μg/mL working concentration
Puromycin dihydrochloride	InvivoGen	ant-pr-1	Purpose_Application:  Selection antibiotic for transduced cells Specifications_Comments: 4 μg/mL selection concentration for 7 days
RPMI-1640 medium	Thermo Fisher Scientific	11875093	Purpose_Application:  Raji B-lymphocyte culture medium Specifications_Comments: With L-glutamine, without phenol red preferred
Trypan Blue Solution	Thermo Fisher Scientific	15250061	Purpose_Application:  Cell viability assessment Specifications_Comments: 0.4% solution for exclusion assay
Controlled-rate Freezing Container	Thermo Fisher Scientific	5100-0001	Purpose_Application:  Controlled-rate cell freezing (-1°C/min) Specifications_Comments: Mr. Frosty or equivalent for -1°C/min cooling
EDTA Blood Collection Tubes	BD Biosciences	366643	Purpose_Application:  Venous blood collection with anticoagulant Specifications_Comments: 10-20 mL capacity, purple top tubes
Ficoll-Paque PLUS Density Gradient	Cytiva (GE Healthcare)	17144003	Purpose_Application:  PBMC isolation via density centrifugation Specifications_Comments: Sterile, endotoxin-tested for cell separation
Phosphate Buffered Saline (PBS)	Thermo Fisher Scientific	14190144	Purpose_Application:  Cell washing and dilution buffer Specifications_Comments: Sterile, cell culture grade
RNA Extraction & qPCR
Chloroform (ACS Grade)	Sigma-Aldrich	C2432	Purpose_Application:  Phase separation in RNA extraction Specifications_Comments: ACS reagent grade, ≥99% purity
Ethanol (75%, Molecular Grade)	Sigma-Aldrich	E7023	Purpose_Application:  RNA pellet washing Specifications_Comments: Molecular biology grade, prepare fresh
Isopropanol (Molecular Grade)	Sigma-Aldrich	I9516	Purpose_Application:  RNA precipitation Specifications_Comments: Molecular biology grade, ≥99.5% purity
Nuclease-free Water	Thermo Fisher Scientific	AM9930	Purpose_Application:  PCR reaction preparation Specifications_Comments: DNase/RNase-free, tested for PCR applications
Optical Adhesive Film	Thermo Fisher Scientific	4311971	Purpose_Application:  Optical sealing for qPCR plates Specifications_Comments: Optical quality for qPCR applications
PCR Plates (96-well)	Thermo Fisher Scientific	N8010560	Purpose_Application:  96-well format for high-throughput qPCR Specifications_Comments: White, clear bottom for optical detection
PCR Tube Strips	Thermo Fisher Scientific	AB0451	Purpose_Application:  Small volume PCR reactions Specifications_Comments: 8-tube strips with individual caps
PrimeScript RT Reagent Kit	Takara Bio	RR037A	Purpose_Application:  Reverse transcription of RNA to cDNA Specifications_Comments: With gDNA Eraser for genomic DNA removal
SYBR Green Master Mix	Applied Biosystems	4309155	Purpose_Application:  Real-time PCR amplification and detection Specifications_Comments: With ROX reference dye for normalization
TRIzol Reagent (RNA Lysis)	Thermo Fisher Scientific	15596026	Purpose_Application:  Cell lysis and RNA extraction Specifications_Comments: Store at 4°C, use within 6 months
Protein Analysis - Western Blot
Acrylamide/Bis-acrylamide (29:1)	Bio-Rad	1610146	Purpose_Application:  SDS-PAGE gel polymerization Specifications_Comments: 30% acrylamide stock solution
BCA Protein Assay Kit	Thermo Fisher Scientific	23225	Purpose_Application:  Protein concentration quantification Specifications_Comments: Reduce-compatible for accurate quantification
Enhanced Chemiluminescence (ECL) Substrate	Thermo Fisher Scientific	32106	Purpose_Application:  Chemiluminescent protein detection Specifications_Comments: Femtogram sensitivity detection
Non-fat Dry Milk	Lab Scientific	170-6404	Purpose_Application:  Western blot blocking agent Specifications_Comments: Blocking grade, low background
Phosphatase Inhibitor Cocktail	Roche Applied Science	4906845001	Purpose_Application:  Prevent protein dephosphorylation Specifications_Comments: Includes okadaic acid and calyculin A
Prestained Protein Ladder	Bio-Rad	1610394	Purpose_Application:  Molecular weight reference standards Specifications_Comments: 10-250 kDa range with 11 bands
Protease Inhibitor Cocktail	Roche Applied Science	11697498001	Purpose_Application:  Prevent protein degradation during lysis Specifications_Comments: EDTA-free for metal-dependent phosphatases
PVDF Membranes (0.45 μm)	Millipore Sigma	IPVH00010	Purpose_Application:  Protein transfer membrane (0.45 μm pore) Specifications_Comments: Low fluorescence background
RIPA Lysis Buffer	Cell Signaling Technology	9806S	Purpose_Application:  Whole cell protein extraction Specifications_Comments: Ready-to-use lysis buffer with detergents
Sample Loading Buffer (4X)	Bio-Rad	1610747	Purpose_Application:  Protein sample preparation for SDS-PAGE Specifications_Comments: Loading dye with β-mercaptoethanol
SDS-PAGE Running Buffer	Bio-Rad	1610732	Purpose_Application:  Protein electrophoresis Specifications_Comments: Tris-glycine-SDS buffer system
Sodium Fluoride	Sigma-Aldrich	201154	Purpose_Application:  Additional phosphatase inhibition Specifications_Comments: 50 mM working concentration
Sodium Orthovanadate	Sigma-Aldrich	S6508	Purpose_Application:  JAK2/STAT phosphorylation preservation Specifications_Comments: 1 mM working concentration, prepare fresh
Transfer Buffer Concentrate	Bio-Rad	1704156	Purpose_Application:  Semi-dry protein transfer Specifications_Comments: 10X concentrate, dilute before use
Tris-Buffered Saline with Tween-20 (TBST)	Cell Signaling Technology	9997S	Purpose_Application:  Membrane washing and antibody dilution Specifications_Comments: 0.1% Tween-20, pH 7.6
CRISPR/Gene Editing
Calcium Phosphate Transfection Kit	Promega	E1200	Purpose_Application:  DNA transfection into packaging cells Specifications_Comments: High transfection efficiency for lentivirus production
DNA Gel Extraction Kit	Qiagen	28706	Purpose_Application:  PCR product purification for sequencing Specifications_Comments: Column-based purification system
GV371 Lentiviral Vector	GeneChem Co., Ltd	GV371	Purpose_Application:  CRISPR/Cas9 expression for gene knockout Specifications_Comments: Ready-to-use CRISPR/Cas9 lentiviral system
HEK293T Cell Line	ATCC	CRL-3216	Purpose_Application:  Lentiviral packaging cell line Specifications_Comments: Highly transfectable packaging cell line
Sanger Sequencing Service	Macrogen Inc.	Custom	Purpose_Application:  Knockout validation and off-target analysis Specifications_Comments: Standard sequencing with custom primers
T7 Endonuclease I	New England Biolabs	M0302S	Purpose_Application:  CRISPR cutting efficiency validation Specifications_Comments: Mismatch-specific endonuclease for CRISPR validation
ELISA & Immunoassays
ELISA Plates (96-well, flat bottom)	Corning	3590	Purpose_Application:  ELISA substrate reaction Specifications_Comments: High-binding, flat-bottom for ELISA
Human CLCF1 DuoSet ELISA	R&D Systems	DY1234	Purpose_Application:  CLCF1 protein quantification (31.2-2000 pg/mL) Specifications_Comments: Detection range: 31.2-2000 pg/mL, CV & 10%
p24 ELISA Kit (Lentiviral titer)	ZeptoMetrix Corporation	801111	Purpose_Application:  Lentiviral titer determination Specifications_Comments: For lentiviral titer determination (>10⸠TU/mL)
Functional Assays
Alizarin Red S Staining Kit	Sigma-Aldrich	A5533	Purpose_Application:  Calcium deposition visualization Specifications_Comments: 2% solution in distilled water, pH 4.1-4.3
Alkaline Phosphatase Activity Kit	Abcam	ab83369	Purpose_Application:  ALP enzymatic activity measurement Specifications_Comments: Colorimetric assay, read at 405 nm
Ascorbic Acid (L-Ascorbic acid)	Sigma-Aldrich	A4544	Purpose_Application:  Osteogenic medium component Specifications_Comments: 50 μg/mL final concentration
Cetylpyridinium Chloride	Sigma-Aldrich	C9002	Purpose_Application:  Alizarin Red S extraction for quantification Specifications_Comments: 10% solution for dye extraction
Dexamethasone	Sigma-Aldrich	D4902	Purpose_Application:  Osteogenic medium component Specifications_Comments: 10 nM final concentration
β-Glycerophosphate	Sigma-Aldrich	G9422	Purpose_Application:  Osteogenic medium component Specifications_Comments: 10 mM final concentration
Osteogenic Differentiation Medium	PromoCell	C-28010	Purpose_Application:  Osteoblast differentiation induction Specifications_Comments: Ready-to-use complete osteogenic medium
Transwell Cell Culture Inserts (0.4 μm)	Corning	3470	Purpose_Application:  Co-culture system with 0.4 μm separation Specifications_Comments: Polyethylene terephthalate membrane, sterile
Equipment - Major Instruments
Centrifuge (High-speed, Refrigerated)	Eppendorf	5430R	Purpose_Application:  Sample processing and cell separation Specifications_Comments: Refrigerated, max 30,000 x g
Chemiluminescence Imaging System	Bio-Rad Laboratories	12003154	Purpose_Application:  Western blot imaging and quantification Specifications_Comments: Gel documentation and Western blot imaging
CO2 Incubator (Humidified)	Thermo Fisher Scientific	51030287	Purpose_Application:  Cell culture maintenance (37°C, 5% CO2) Specifications_Comments: Triple gas (CO2/O2/N2), humidity control
Heart Rate Monitor (Chest Strap)	Polar Electro	H10	Purpose_Application:  Continuous heart rate monitoring Specifications_Comments: Bluetooth connectivity, ±1 bpm accuracy
Hologic Discovery A DXA Scanner	Hologic Inc.	Discovery A	Purpose_Application:  Bone mineral density measurement Specifications_Comments: With APEX software v4.5, daily QC required
Microplate Reader (Multi-mode)	BioTek Instruments	Synergy H1	Purpose_Application:  ELISA plate reading and absorbance measurement Specifications_Comments: UV-Vis, fluorescence, luminescence detection
Motorized Treadmill	Life Fitness	95Ti	Purpose_Application:  Standardized exercise intervention Specifications_Comments: Variable speed 0-16 km/h, 0-15% grade
Real-time PCR System (CFX96 or equivalent)	Bio-Rad Laboratories	1855195	Purpose_Application:  Real-time PCR amplification and detection Specifications_Comments: 96-well block, gradient capable
Software & Analysis Tools
APEX Software v4.5 (DXA Analysis)	Hologic Inc.	v4.5	Purpose_Application:  DXA scan analysis and BMD calculation Specifications_Comments: BMD analysis with reference database
Bio-Rad CFX Maestro	Bio-Rad Laboratories	CFX Maestro	Purpose_Application:  qPCR data analysis and Ct determination Specifications_Comments: Real-time PCR analysis and data export
GraphPad Prism v9.0	GraphPad Software	v9.0	Purpose_Application:  Statistical analysis and graph generation Specifications_Comments: Statistical software with graph generation
ImageJ/Fiji v1.53	National Institutes of Health	v1.53	Purpose_Application:  Western blot densitometry and image analysis Specifications_Comments: Image analysis with measurement tools
Microsoft Excel 365	Microsoft Corporation	365	Purpose_Application:  Data organization and basic calculations Specifications_Comments: Data organization and basic statistical functions
Consumables & Plasticware
1.5 mL Microcentrifuge Tubes	Eppendorf	22363204	Purpose_Application:  Small volume sample storage and processing Specifications_Comments: DNase/RNase-free, low-binding
15 mL Conical Tubes	Corning	430766	Purpose_Application:  Medium volume sample processing Specifications_Comments: Polypropylene, graduated, with caps
24-well Cell Culture Plates	Corning	3524	Purpose_Application:  Co-culture and functional assay setup Specifications_Comments: Tissue culture treated, flat bottom
50 mL Conical Tubes	Corning	430829	Purpose_Application:  Large volume sample collection and processing Specifications_Comments: Polypropylene, graduated, with caps
Cryovials (1 mL)	Thermo Fisher Scientific	375418	Purpose_Application:  Long-term cell and sample storage at -80°C Specifications_Comments: External thread, O-ring seal, -196°C rated
Pasteur Pipettes (Sterile)	Fisher Scientific	13-678-20A	Purpose_Application:  Sterile sample collection and transfer Specifications_Comments: Individually wrapped, sterile