Mesenchymal stem/stromal cell quality control: validation of mixed lymphocyte reaction assay using flow cytometry according to ICH Q2(R1)

Background

Mesenchymal stem/stromal cells (MSC) have immunomodulatory properties, studied in a wide range of diseases. Validated quality controls must confirm this activity in the context of clinical trials. This study presents a method’s validation, assessing MSC’s ability to inhibit lymphocyte proliferation, according to the ICH Q2 standard.

Methods

MSC were co-cultured with CellTrace™ Violet-labeled Peripheral blood mononuclear cells (PBMC) coming from a bank of ten donors, at seven different ratios for 7 days. Cell trace violet PBMC bank was validated in parallel. Flow cytometry analysis was used to obtain the division percentage of T cells. The percentage of inhibition of lymphocyte proliferation by MSC, for each ratio X, was calculated using the formula: Ratio × percentage of inhibition = (control percentage of division—ratio × percentage of division)/control percentage of division. The inhibition percentage of lymphocyte proliferation function of co-culture ratios was represented in a line graph. The corresponding area under the curve was calculated, representing MSC’s ability to inhibit lymphocyte proliferation.

Results

Two cell trace violet PBMC banks were compared for bank validation. When compared using four different MSC samples coming each from a different donor, their area under the curve did not show any statistical differences and were correlated. Moreover, the stability of one cell trace violet PBMC bank was confirmed up to 509 days of storage.

Analytical parameters were investigated for method validation. Analysis of repeatability and reproducibility respectively showed a standard deviation of 6.1% and 4.6%. The assay was robust regarding PBMC, as no statistical differences were found between inhibitory activities when testing three adjacent concentrations of PBMC. Still, attention is needed on MSC quantity as it can influence results. Linearity was evaluated: the percentage of inhibition of lymphocyte proliferation function of co-culture ratios was linear on the exploited range. Finally, the assay measurement range allowed to differentiate MSC presenting different inhibition activities.

Conclusion

This quantification method displayed low analytical variability and no inter-bank variability of PBMC. However, MSC quantification should be checked before co-culture to reduce variability. Therefore, it could be used for the qualification of MSC batches’ immunomodulatory activity.

Early Proteinuria Is a Strong Indicator of Donor Renal Lesions, Ischemia-Reperfusion Injury and Immunological Aggression

BACKGROUND

Early proteinuria is associated with reduced long-term graft survival. However, the determinants and mechanisms of proteinuria early after transplantation have not been identified.

METHODS

Parameters associated with proteinuria within the first 3 months following transplantation were retrospectively assessed among 484 renal transplant recipients.

RESULTS

Proteinuria was more abundant in patients with a history of two or more rejection episodes (0.42 +/- 0.68 vs 0.18 +/- 0.39 g/d; P = .02). Proteinuria was greater when donor age was 60 or more (OR: 4.43; P = .003), when recipient death was due to cardiovascular causes (OR: 1.98; P = .002), or when cold (OR: 1.77; P = .006) or warm (1.21; P = .09) ischemia times were prolonged.

CONCLUSIONS

Proteinuria early after transplantation was related to pretransplant renal lesions, ischemia-reperfusion, and immunologic injuries.