Background: The selection of assays suitable for testing the potency of clinical grade multipotent mesenchymal stromal cell (MSC)-based products and its interpretation is a challenge for both developers and regulators. Here, we present a bioprocess design for the production of Wharton’s jelly (WJ)-derived MSCs and a validated immunopotency assay approved by the competent regulatory authority for batch release together with the study of failure modes in the bioprocess with potential impact on critical quality attributes (CQA) of the final product. Methods: The lymphocyte proliferation assay was used for determining the immunopotency of WJ-MSCs and validated under good manufacturing practices (GMP). Moreover, failure mode effects analysis (FMEA) was used to identify and quantify the potential impact of different unexpected situations on the CQA. Results: A production process based on a two-tiered cell banking strategy resulted in batches with sufficient numbers of cells for clinical use in compliance with approved specifications including MSC identity (expressing CD73, CD90, CD105, but not CD31, CD45, or HLA-DR). Remarkably, all batches showed high capacity to inhibit the proliferation of activated lymphocytes. Moreover, implementation of risk management tools led to an in-depth understanding of the manufacturing process as well as the identification of weak points to be reinforced. Conclusions: The bioprocess design showed here together with detailed risk management and the use of a robust method for immunomodulation potency testing allowed for the robust production of clinical-grade WJ-MSCs under pharmaceutical standards.

Donor human milk (DHM) can harbor microbial contaminants that cause serious infections in premature infants. Bacillus cereus is a pathogen frequently found in DHM, capable of forming spores that can resist Holder pasteurization (62.5 °C, 30 min). Since no microbial growth is acceptable in post-pasteurized DHM, microbiological testing of pre-pasteurized DHM provides information about its contamination level to determine if it should be accepted for pasteurization. Culture is the gold standard in microbiological control but it requires 24–48 h to provide results. In this study we developed and validated a non-commercial real-time PCR assay for the detection of Bacillus cereus (BC test) in DHM specimens on a fully automated high-throughput platform, the cobas^® 6800 system. The BC test showed excellent sensitivity and specificity, repeatability and linearity over an 8-log range and a low limit of detection in milk specimens, as well as good agreement with selective culture methods. BC test was then used to systematically control all milk donations (3439) over a 24-month period. Bacillus cereus was detected in 14.2% of DHM, with monthly rates ranging from 6 to 29% and a significantly higher incidence in warmer months. Incorporating this assay into our laboratory workflow improved efficiency and reduced turnaround time.

Fungal contamination of donor corneas, although rare, constitutes a serious infection risk to recipients. Therefore, microbiological quality control with methods optimized for fungal detection is crucial in eye banks to detect and discard contaminated corneas. This study aimed to compare the performance of different BACT/ALERT^® bottles (iFA Plus and iLYM) incubated at different temperatures (32 °C and 37 °C) when corneal preservation media, with or without amphotericin B, were cultured. A total of 6 culture conditions were compared by inoculation of fewer than 100 colony-forming units of 18 fungi (10 yeasts and 8 filamentous fungi). iFA Plus bottles incubated at 32 °C reliably detected 94.4% of fungi, regardless of amphotericin B presence, while iLYM bottles detected 77.8% in the absence of amphotericin B and 72.2% in its presence. At 37 °C, iFA Plus fungal detection decreased to 61.1%. iFA Plus bottles incubated at 32 °C provided the highest detection rates, effectively neutralizing the effect of amphotericin B and enabling recovery of both yeasts and filamentous fungi, except for Cladosporium. Our findings support that the optimal strategy for cornea sterility testing is incubating iFA Plus bottles at 32 °C for optimal fungal recovery, while maintaining iFN Plus at 37 °C to allow timely detection of anaerobic bacteria.