Targeting mitochondrial quality control in osteoarthritis with GrpE-like 1-loaded synovial mesenchymal stromal/stem cell small extracellular vesicles

Table 1 Minimum reporting set for intra-articular extracellular vesicle studies (bench and early clinical)

Domain	Required elements (minimum)	How to report (units/assays)	Harmonized time-points	Quality/acceptance notes
EV identity & purity	Particle size/number; protein; ≥ 1 positive and ≥ 1 negative protein marker	NTA (particles/mL); BCA or Simoa (μg/mL); western/flow for tetraspanins; negative marker (e.g., calnexin)	N/A	Follow MISEV2023 identity/purity panels; disclose isolation workflow and co-isolates
Dose normalization	Report both particle number and protein mass	Per-joint dose: Total particles and μg; lot-to-lot CVs	N/A	Dual metrics enable cross-study comparison and QC trending
Exposure/retention (biodistribution)	Joint residence and/or tissue association	Fluorescent or radiolabel tracking; cargo-based tracers (qPCR/protein)	1 hour, 24 hours, 7 days (shared anchors)	Predefine quench/correction; report synovial fluid/tissue ROIs and decay characteristics
Potency/MoA-linked readout	Mechanism-aligned assay + viability/toxicity	Cell-based PD (e.g., PINK1/PRKN index), live/dead, cytokines	N/A	Specify acceptance ranges; link potency to dose and exposure
Transparency & rigor	Protocol registration; method completeness	EV-TRACK/EV-METRIC ID; checklist link	N/A	Improves reproducibility and peer auditability
Safety	Local/systemic AEs; labs	Joint flare, effusions, vitals; CRP; imaging if indicated	Visit-aligned (e.g., baseline, week 2, week 12)	IND oversight where applicable; note no FDA-approved EV products

EV: Extracellular vesicle; NTA: Nanoparticle tracking analysis; BCA: Bicinchoninic acid assay; N/A: Not applicable; MISEV2023: Minimal Information for Studies of Extracellular Vesicles (2023 update); CV: Coefficient(s) of variation; sEV(s): Small extracellular vesicle(s); QC: Quality control; qPCR: Quantitative polymerase chain reaction; ROI: Region of interest; MoA: Mechanism of action; PD: Pharmacodynamics; PINK1: PTEN-induced kinase 1; PRKN: Parkin E3 ubiquitin ligase; CMC: Chemistry, manufacturing, and controls; Simoa: Single molecule array; PK: Pharmacokinetics; EV-TRACK: Transparent Reporting and Centralizing Knowledge in Extracellular Vesicle Research; EV-METRIC: Transparent Reporting and Centralizing Knowledge in Extracellular Vesicle Research Reporting Completeness Score; AEs: Adverse events; CRP: C-reactive protein; IND: Investigational New Drug; FDA: Food and Drug Administration.

Table 2 Phase II signal-finding endpoint framework mapped to Outcome Measures in Rheumatology-Osteoarthritis Research Society International

OMERACT-OARSI domain	Endpoint (suggested measure)	Time-points	Role in trial	Rationale
Pain	WOMAC pain (or KOOS pain)	Baseline, week 12, week 24	Primary	Core domain; sensitive to change
Function	KOOS-ADL (or WOMAC function)	Baseline, week 12, week 24	Key secondary	Functional relevance; limits multiplicity
Patient global	Patient global assessment	Baseline, week 12, week 24	Secondary	Complements pain/function per core set
Structural progression	MRI cartilage thickness (pre-specified compartment/ROI)	Baseline, 12-24 months (exploratory in phase II)	Exploratory (or key secondary if powered)	Supported by FNIH analyses; pre-register analysis
Safety	Local/systemic AEs; labs	Visit-aligned	Required	IND-appropriate safety set

OMERACT: Outcome Measures in Rheumatology; OARSI: Osteoarthritis Research Society International; WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index; KOOS: Knee injury and Osteoarthritis Outcome Score; ADL: Activities of daily living; MRI: Magnetic resonance imaging; ROI: Region of interest; FNIH: Foundation for the National Institutes of Health; AEs: Adverse events; IND: Investigational New Drug.