The Essential Need for a Validated Potency Assay for Cell-Based Therapies in Cardiac Regenerative and Reparative Medicine. A Practical Approach to Test Development

Abstract

Biological treatments are one of the medical breakthroughs in the twenty-first century. The initial enthusiasm pushed the field towards indiscriminatory use of cell therapy regardless of the pathophysiological particularities of underlying conditions. In the reparative and regenerative cardiovascular field, the results of the over two decades of research in cell-based therapies, although promising still could not be translated into clinical scenario. Now, when we identified possible deficiencies and try to rebuild its foundations rigorously on scientific evidence, development of potency assays for the potential therapeutic product is one of the steps which will bring our goal of clinical translation closer. Although, highly challenging, the potency tests for cell products are considered as a priority by the regulatory agencies. In this paper we describe the main characteristics and challenges for a cell therapy potency test focusing on the cardiovascular field. Moreover, we discuss different steps and types of assays that should be taken into consideration for an eventual potency test development by tying together two fundamental concepts: target disease and expected mechanism of action. Graphical Abstract Development of potency assays for cell-based products consists in understanding the pathophysiology of the disease, identifying potential mechanisms of action (MoA) to counteract it and finding the most suitable cell-based product that exhibits these MoA. When applied, the potency assay needs to correlate bioactivity of the product, via a measurement related to the MoA, with treatment efficacy. However, in the cardiovascular field, the process faces several challenges and high requirements.

Effect of Shenfu Injection on Differentiation of Bone Marrow Mesenchymal Stem Cells into Pacemaker-Like Cells and Improvement of Pacing Function of Sinoatrial Node

“…However, the implantation of an electronic pacemaker in patients is accompanied by several complications, such as infection, electrode dysfunction, battery exhaustion, and bleeding [ 2 ]. Recently, for the purpose of circumventing the limitations and negative impacts of electronic pacemakers, stem cell-based biological pacemakers have been widely investigated so as to initiate the spontaneous activity of formerly quiescent cardiomyocytes [ 3 – 5 ]. Recent investigations have mainly focused on the induction of pacemaker-like cells through genetic reprogramming of stem cells [ 6 ].…”

Extracellular vesicles secreted by human cardiosphere-derived cells attenuate electrophysiological remodelling in an in vitro model of atrial fibrillation

“…When moving stem cells as products from preclinical studies to the cardiac clinical scenario, hasty translation [283] led to underestimation of how cell heterogeneity and complexity could impact potency. Cell (and its derived products) potency has shown to depend on many other factors apart from cell identity, such as on the intended purpose and the expected MoA, the environment, the cell source, the age of the cells, the age of the donor and the intrinsic physiologically state of the tissue of origin [268,276,291,333,334]. Finding economic, feasible and efficient potency assays based on evidence of MoA for cell and cell-derived EVs still remains a challenge [110,279,291], and crucial for successful translation.…”

“…Despite most clinical trials used confirmation of cell identity as the single requirement right before product administration [291], the gold standard for cell potency assessment in cardiac applications is structural and functional recovery in a rodent model of myocardial infarction (MI) [268,335]. However, this model is costly, time-consuming and of doubtful translation, hindering its use for routine testing [306].…”

“…Therefore, it is affected by chronological age [342] and by the number of passages [333,360]. Despite senescence being recommended as a cell quality marker for cell production [361], it is still not used on routinary analysis before cell product release [291]. Some studies have shown that senescence negatively impacts on cell reparative potency [87,277] but it has been poorly explored as a marker of cellderived EV potency.…”

“…attenuating cardiomyocyte (CM) apoptosis and hypertrophy, reducing regional fibrosis [137,138] and acting as immunomodulators [137,139]. However, cell and cell-derived products present an inherent complexity that translates into a variable potency hard to predict [268,276,291,333,334].…”