Review Papers Claim by Claim

1) What the paper claims (tight mapping to evidence in text)

• Barrier formation (structural + functional): Vero E6 monolayers on transwell inserts develop continuous coverage and express tight/adherens junction markers ZO-1 and β-catenin by ~DIV6 ZO-1 and β-catenin localization by DIV6.
• Functional electrical barrier readout: TEER peaks around ~30 Ω·cm² in serum-containing medium and ~45 Ω·cm² in “virus production medium” TEER peak values in CM vs VPM.
• Paracellular transport restriction: 4 kDa FITC-dextran shows low permeability, with Papp ≈ 3.7×10⁻⁶ cm/s Papp for 4 kDa FITC-dextran.
• Calcium sensitivity + reversibility: EGTA chelation produces dose-dependent TEER decrease (2–10 mM) and increased permeability, and the barrier recovers after Ca²⁺ reintroduction EGTA dose response and recovery.

2) Skeptical interpretation: what these results do NOT prove

• “Barrier” is operational: TEER + tracer flux + junction localization support a functional barrier state, but they don’t uniquely identify barrier mechanisms (e.g., pore-forming vs claudin-density vs cytoskeletal effects). The paper is strongest at phenomenology, weaker at mechanism beyond Ca²⁺-dependence Mechanistic limits and translation caveats.
• Species/tissue generalization is uncertain: Vero E6 is described as a permissive virology line derived from African green monkey kidney; the paper itself acknowledges this may limit replication of human tissue responses Vero E6 non-human origin; translation caution.
• Live-virus integration is not demonstrated in the excerpted report: the paper positions future coupling of live infection to TEER/permeability rather than presenting infection-driven barrier disruption within this report text Live-virus barrier disruption deferred to future work.
• Quantitative comparators: The comparison “comparable to endothelial models” is argued, but without full distributions (in this provided text) across multiple established barrier systems, the strength of that comparative framing is limited. The paper cites general TEER/permeability literature for context TEER methods considerations Permeability assay methods Tight junction modulation and transport context.

3.1 Peak TEER by culture medium (reported maxima)

3.2 Paracellular permeability of 4 kDa FITC-dextran (reported Papp)

4.1 TEER measurement workflow

• Describes blank subtraction and area normalization, plus baseline drift correction using interpolated blank-insert resistance values TEER blank subtraction + drift handling.
• Uses a dedicated scanning TEER system with specified electrodes and temperature control during measurements (important for reproducibility of resistive readouts) TEER instrumentation + temperature control.

4.2 Transport assay handling and artifact correction

• Implements automated sampling and states that sequential samples can deviate due to adsorption/desorption and droplet retention, then applies a linear recursive correction model parameterized from cell-free calibration experiments Sampling artifact correction using calibration Artifact correction model reference.
• This is a significant credibility point: paracellular transport readouts are highly sensitive to sampling bias, and the paper acknowledges and corrects it, rather than relying on raw concentration-time data Cross-sample contamination and correction.

• EGTA confounds: EGTA is treated as a Ca²⁺ chelator that disrupts tight junctions, but ionic strength / conductivity effects can also alter TEER independent of junctional sealing. The paper explicitly reports that 1 mM EGTA caused a slight TEER increase likely due to reduced medium conductivity, which is an important confound acknowledgement 1 mM EGTA conductivity confound.
• Transport mechanism ambiguity: Using a single 4 kDa tracer doesn’t fully disentangle paracellular pathways vs potential secondary effects (e.g., membrane damage) even though the tracer is described as not crossing intact tight junctions or entering cells. A mechanistic claim beyond “paracellular permeability changed” is therefore limited by tracer choice Tracer interpretation limits.
• Substrate/labeling differences: The paper notes immunofluorescence is sharper on glass than on polycarbonate membranes. That matters because junction localization quality can affect confidence in “mature” junction assembly Immunostaining substrate differences.
• Non-human model risk: Vero E6’s interferon deficiency is often cited as a reason for permissiveness; however, that same biology might change barrier regulation (e.g., inflammatory signaling pathways) relative to human epithelia. The excerpt acknowledges the line’s non-human origin and cautions against full tissue replication Vero interferon production defect Limitations on tissue replication.