Abstract
End-stage kidney disease represents irreversible kidney failure. Dialysis and transplantation, two main treatment options currently available, present various drawbacks and complications. Innovative cell-based therapies, such as a bioartificial kidney, have not reached the clinic yet, mostly due to safety and/or functional issues. Here, we assessed the safety of conditionally immortalized proximal tubule epithelial cells (ciPTECs) for bioartificial kidney application, by using in vitro assays and athymic nude rats. We demonstrate that these cells do not possess key properties of oncogenically transformed cells, including anchorage-independent growth, lack of contact inhibition and apoptosis-resistance. In late-passage cells we did observe complex chromosomal abnormalities favoring near-tetraploidy, indicating chromosomal instability. However, time-lapse imaging of ciPTEC-OAT1, confined to a 3D extracellular matrix (ECM)-based environment, revealed that the cells were largely non-invasive. Furthermore, we determined the viral integration sites of SV40 Large T antigen (SV40T), human telomerase (hTERT) and OAT1 (SLC22A6), the transgenes used for immortalization and cell function enhancement. All integrations sites were found to be located in the intronic regions of endogenous genes. Among these genes, early endosome antigen 1 (EEA1) involved in endocytosis, and BCL2 Like 1 (BCL2L1) known for its role in regulating apoptosis, were identified. Nevertheless, both gene products appeared to be functionally intact. Finally, after subcutaneous injection in athymic nude rats we show that ciPTEC-OAT1 lack tumorigenic and oncogenic effects in vivo, confirming the in vitro findings. Taken together, this study lays an important foundation towards bioartificial kidney (BAK) development by confirming the safety of the cell line intended for incorporation.
Highlights
End-stage kidney disease (ESKD) represents irreversible kidney failure through a variety of causes
In a subconfluent state a higher proportion of cells was found in S-phase at the permissive temperature (Figure 1B; 40.5% ± 1.7%) compared to 37° C for 1 day (10.5% ± 2.0%) or 7 days (17.0% ± 3.4%), confirming that SV40 Large T antigen (SV40T) protein expression is directly related to cell proliferation
We mechanistically and functionally confirmed that conditionally immortalized proximal tubule epithelial cells (PTEC) (ciPTEC)-organic anion transporter 1 (OAT1) behave in accordance with conditional immortalization
Summary
End-stage kidney disease (ESKD) represents irreversible kidney failure through a variety of causes. With frequently occurring diabetes, atherosclerotic vascular disease, and hypertension, is predominantly responsible for an increasing prevalence of ESKD [1,2,3]. Recognition of the problems related to currently available treatments, has spurred the development of novel approaches of which cell-based systems, known as bioartificial kidney (BAK), that seek to replicate the kidney’s function through the integration of proximal tubule cells are of promise [5]. One of the crucial issues to take into consideration when developing a BAK is the sufficient availability of suitable cells. Issues related to the use of animal-derived cells in BAK are safety concerns compromising approval for clinical application and species differences in cell behaviour
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