In Vitro Induction of Pluripotency from Equine Fibroblasts in 20% or 5% Oxygen

Footprint-free induced pluripotent stem cells can be successfully differentiated into mesenchymal stromal cells in the feline model

BACKGROUND

Induced pluripotent stem cells (iPSCs) can propagate indefinitely and give rise to every other cell type, rendering them invaluable for disease modelling, drug development research, and usage in regenerative medicine. While feline iPSCs have been described, there are currently no reports on generating genome integration (footprint)-free iPSCs from domestic cats. Therefore, the objective of this study was to generate feline iPSCs from fetal fibroblasts using non-integrative Sendai virus (SeV) vectors carrying human transcription factors. Moreover, these iPSCs were differentiated into mesenchymal stromal cells (MSCs), which can be used as an alternative to tissue-derived MSCs.

METHODS

Feline fetal fibroblasts were transduced with CytoTune-iPS 2.0 Sendai Reprogramming vectors at recommended multiplicity of infections (MOI) and cultured for about 6 days. At 7 days post transduction cells were dissociated, replated on inactivated feeder cells and maintained in iPSC medium for 28 days with daily medium change. Emerging iPSC colonies were mechanically passaged and transferred to fresh feeder cells and further passaged every 6-8 days. Four feline iPSC lines were generated, with two selected for further in-depth characterization. Feline iPSCs were then differentiated into MSCs using a serial plating strategy and an inhibitor of the transforming growth factor-β (TGF-β) type I receptor.

RESULTS

Feline iPSCs exhibited characteristic colony morphology, high nuclear-to-cytoplasmic ratio, positive alkaline phosphatase activity, and expressed feline OCT4, SOX2, and Nanog homeobox (NANOG) stem cell markers. Expression of SeV-derived transgenes decreased during passaging to be eventually lost from the host cells and feline iPSCs could be stably maintained for over 35 passages. Feline iPSCs differentiated into embryoid bodies in vitro and did not form fully differentiated teratomas; instead, they generated in vivo masses containing mesodermal tissue derivatives when injected into immunodeficient mice. Feline iPSC-derived MSCs were plastic adherent, displayed MSC-like morphology, expressed MSC-specific surface markers, and differentiated into cells from the mesodermal lineage in vitro. RNA deep sequencing identified 1,189 differentially expressed genes in feline iPSC-derived MSCs compared to feline iPSCs.

CONCLUSION

We demonstrated the generation of footprint-free iPSCs from domestic cats and their directed differentiation potential towards MSCs. These SeV-derived feline iPSCs and iPSC-derived MSCs will provide valuable models to study feline diseases and explore novel therapeutic strategies and can serve as translational models for human health, leading to increased knowledge on disease pathogenesis and improved therapeutic interventions.

Induced pluripotent stem cells in companion animals: how can we move the field forward?

Following a one medicine approach, the development of regenerative therapies for human patients leads to innovative treatments for animals, while pre-clinical studies on animals provide knowledge to advance human medicine. Among many different biological products under investigation, stem cells are among the most prominent. Mesenchymal stromal cells (MSCs) are extensively investigated, but they present challenges such as senescence and limited differentiation ability. Embryonic stem cells (ESCs) are pluripotent cells with a virtually unlimited capacity for self-renewal and differentiation, but the use of embryos carries ethical concerns. Induced pluripotent stem cells (iPSCs) can overcome all of these limitations, as they closely resemble ESCs but are derived from adult cells by reprogramming in the laboratory using pluripotency-associated transcription factors. iPSCs hold great potential for applications in therapy, disease modeling, drug screening, and even species preservation strategies. However, iPSC technology is less developed in veterinary species compared to human. This review attempts to address the specific challenges associated with generating and applying iPSCs from companion animals. Firstly, we discuss strategies for the preparation of iPSCs in veterinary species and secondly, we address the potential for different applications of iPSCs in companion animals. Our aim is to provide an overview on the state of the art of iPSCs in companion animals, focusing on equine, canine, and feline species, as well as to identify which aspects need further optimization and, where possible, to provide guidance on future advancements. Following a "step-by-step" approach, we cover the generation of iPSCs in companion animals from the selection of somatic cells and the reprogramming strategies, to the expansion and characterization of iPSCs. Subsequently, we revise the current applications of iPSCs in companion animals, identify the main hurdles, and propose future paths to move the field forward. Transferring the knowledge gained from human iPSCs can increase our understanding in the biology of pluripotent cells in animals, but it is critical to further investigate the differences among species to develop specific approaches for animal iPSCs. This is key for significantly advancing iPSC application in veterinary medicine, which at the same time will also allow gaining pre-clinical knowledge transferable to human medicine.

Influence of Cell Type in In Vitro Induced Reprogramming in Cattle

Induced pluripotent stem cells (iPSCs) have been considered an essential tool in stem cell research due to their potential to develop new therapies and technologies and answer essential questions about mammalian early development. An important step in generating iPSCs is selecting their precursor cell type, influencing the reprogramming efficiency and maintenance in culture. In this study, we aim to characterize bovine mesenchymal cells from adipose tissue (bAdMSCs) and fetal fibroblasts (bFFs) and to compare the reprogramming efficiency of these cells when induced to pluripotency. The cells were characterized by immunostaining (CD90, SSEA1, SSEA3, and SSEA4), induced differentiation in vitro, proliferation rates, and were subjected to cell reprogramming using the murine OSKM transcription factors. The bFFs presented morphological changes resembling pluripotent cells after reprogramming and culture with different supplementation, and putative iPSCs were characterized by immunostaining (OCT4, SOX2, NANOG, and AP). In the present study, we demonstrated that cell line origin and cellular proliferation rate are determining factors for reprogramming cells into pluripotency. The generation of biPSCs is a valuable tool to improve both translational medicine and animal production and to study the different supplements required to maintain the pluripotency of bovine cells in vitro.

In vitro induced pluripotency from urine-derived cells in porcine

BACKGROUND

The generation of induced pluripotent stem cells (iPSC) has been a game-changer in translational and regenerative medicine; however, their large-scale applicability is still hampered by the scarcity of accessible, safe, and reproducible protocols. The porcine model is a large biomedical model that enables translational applications, including gene editing, long term in vivo and offspring analysis; therefore, suitable for both medicine and animal production.

AIM

To reprogramme in vitro into pluripotency, and herein urine-derived cells (UDCs) were isolated from porcine urine.

METHODS

The UDCs were reprogrammed in vitro using human or murine octamer-binding transcription factor 4 (OCT4), SRY-box2 (SOX2), Kruppel-like factor 4 (KLF4), and C-MYC, and cultured with basic fibroblast growth factor (bFGF) supplementation. To characterize the putative porcine iPSCs three clonal lineages were submitted to immunocytochemistry for alkaline phosphatase (AP), OCT4, SOX2, NANOG, TRA1 81 and SSEA 1 detection. Endogenous transcripts related to the pluripotency (OCT4, SOX2 and NANOG) were analyzed via reverse transcription quantitative real-time polymerase chain reaction in different time points during the culture, and all three lineages formed embryoid bodies (EBs) when cultured in suspension without bFGF supplementation.

RESULTS

The UDCs were isolated from swine urine samples and when at passage 2 submitted to in vitro reprogramming. Colonies of putative iPSCs were obtained only from UDCs transduced with the murine factors (mOSKM), but not from human factors (hOSKM). Three clonal lineages were isolated and further cultured for at least 28 passages, all the lineages were positive for AP detection, the OCT4, SOX2, NANOG markers, albeit the immunocytochemical analysis also revealed heterogeneous phenotypic profiles among lineages and passages for NANOG and SSEA1, similar results were observed in the abundance of the endogenous transcripts related to pluripotent state. All the clonal lineages when cultured in suspension without bFGF were able to form EBs expressing ectoderm and mesoderm layers transcripts.

CONCLUSION

For the first time UDCs were isolated in the swine model and reprogrammed into a pluripotent-like state, enabling new numerous applications in both human or veterinary regenerative medicine.

Cattle In Vitro Induced Pluripotent Stem Cells Generated and Maintained in 5 or 20% Oxygen and Different Supplementation

The event of cellular reprogramming into pluripotency is influenced by several factors, such as in vitro culture conditions (e.g., culture medium and oxygen concentration). Herein, bovine iPSCs (biPSCs) were generated in different levels of oxygen tension (5% or 20% of oxygen) and supplementation (bFGF or bFGF + LIF + 2i-bFL2i) to evaluate the efficiency of pluripotency induction and maintenance in vitro. Initial reprogramming was observed in all groups and bFL2i supplementation initially resulted in a superior number of colonies. However, bFL2i supplementation in low oxygen led to a loss of self-renewal and pluripotency maintenance. All clonal lines were positive for alkaline phosphatase; they expressed endogenous pluripotency-related genes SOX2, OCT4 and STELLA. However, expression was decreased throughout the passages without the influence of oxygen tension. GLUT1 and GLUT3 were upregulated by low oxygen. The biPSCs were immunofluorescence-positive stained for OCT4 and SOX2 and they formed embryoid bodies which differentiated in ectoderm and mesoderm (all groups), as well as endoderm (one line from bFL2i in high oxygen). Our study is the first to compare high and low oxygen environments during and after induced reprogramming in cattle. In our conditions, a low oxygen environment did not favor the pluripotency maintenance of biPSCs.