In vitro and in vivo study on angiogenesis of porcine induced pluripotent stem cell-derived endothelial cells

Vascular endothelial cells derived from transgene-free pig induced pluripotent stem cells for vascular tissue engineering

Induced pluripotent stem cells (iPSCs) hold great promise for the treatment of cardiovascular diseases through cell-based therapies, but these therapies require extensive preclinical testing that is best done in species-in-species experiments. Pigs are a good large animal model for these tests due to the similarity of their cardiovascular system to humans. However, a lack of adequate pig iPSCs (piPSCs) that are analogous to human iPSCs has greatly limited the potential usefulness of this model system. Herein, transgene-free piPSCs with true pluripotency were generated by using reprogramming factors in an optimized pig pluripotency medium. Using an effective differentiation protocol, piPSCs were used to derive endothelial cells (ECs) which displayed EC markers and functionality comparable to native pig ECs. Further, piPSC-ECs demonstrated suitability for vascular tissue engineering, producing a tissue engineered vascular conduit (TEVC) that displayed the upregulation of flow responding markers. In an in vivo functional study, these piPSC-EC-TEVCs maintained the expression of endothelial markers and prevented thrombosis as interposition inferior vena cava grafts in immunodeficient rats. The piPSCs described in this study open up the possibility of unique preclinical species-in-species large animal modeling for the furtherance of modeling of cell-based cardiovascular tissue engineering therapies. STATEMENT OF SIGNIFICANCE: While there has been significant progress in the development of cellularized cardiovascular tissue engineered therapeutics using stem cells, few of them have moved into clinical trials. This is due to the lack of a robust preclinical large animal model to address the high safety and efficacy standards for transplanted therapeutics. In this study, pig stem cells that are analagous to human's were created to address this bottleneck. They demonstrated the ability to differentiate into functional endothelial cells and were able to create a tissue engineered therapeutic that is analogous to a human therapy. With these cells, future experiments testing the safety and efficacy of tissue engineered constructs are possible, bringing these crucial therapeutics closer to the patients that need them.

From isolation to detection, advancing insights into endothelial matrix-bound vesicles

Matrix-bound vesicles (MBVs), an integral part of the extracellular matrix (ECM), are emerging as pivotal factors in ECM-driven molecular signaling. This study is the first to report the isolation of MBVs from porcine arterial endothelial cell basement membranes (A-MBVs) and thyroid cartilage (C-MBVs), the latter serving as a negative control due to its minimal vascular characteristics. Using Transmission Electron Microscopy (TEM), Nano-Tracking Analysis (NTA), Electrochemical Impedance Spectroscopy (EIS), and Atomic Force Microscopy (AFM), we orthogonally characterized the isolated MBVs. We detected the presence and preservation of vascular endothelial cadherin (CD144) in A-MBVs, its low to non-detetcted in C-MBVs, in which SOX9, a chondrocyte marker, was detected. Moreover, we developed a prototype of an immuno-functionalized screen-printed electrode designed for the immunoadsorption of CD144+ MBVs. This device facilitated the electrochemical detection of the targeted vesicles and allowed for their subsequent topological characterization using AFM, which verified the integrity and morphology of CD144+ MBVs post-immunoadsorption. These advancements enhance our comprehension of MBVs as conveyors of tissue-specific signals and pioneer new avenues for harnessing their cargo in biomedical applications. This research sets a significant precedent for future studies on the application of MBVs in regenerative medicine and ECM signaling.

Three-Dimensional Cell Culture Scaffold Supports Capillary-Like Network Formation by Endothelial Cells Derived from Porcine-Induced Pluripotent Stem Cells

INTRODUCTION

Endothelial cells (EC) can be generated from porcine-induced pluripotent stem cells (piPSC), but poor efficiency in driving EC differentiation hampers their application and efficacy. Additionally, the culture of piPSC-derived EC (piPSC-EC) on three-dimensional (3D) scaffolds has not been fully reported yet. Here, we report a method to improve the generation of EC differentiation from piPSC and to facilitate their culture on 3D scaffolds, providing a potential resource for in vitro drug testing and the generation of tissue-engineered vascular grafts.

METHODS

We initiated the differentiation of piPSC into EC by seeding them on laminin 411 and employing a three-stage protocol, which involved the use of distinct EC differentiation media supplemented with CHIR99021, BMP4, VEGF, and bFGF.

RESULTS

piPSC-EC not only expressed EC markers such as CD31, VE-cadherin, and von Willebrand factor (vWF) but also exhibited an upregulation of EC marker genes, including CD31, CD34, VEGFR2, VE-cadherin, and vWF. They exhibited functional characteristics similar to those of porcine coronary artery endothelial cells (PCAEC), such as tube formation and Dil-Ac-LDL uptake. Furthermore, when cultured on 3D scaffolds, piPSC-EC developed a 3D morphology and were capable of forming an endothelial layer and engineering capillary-like networks, though these lacked lumen structures.

CONCLUSION

Our study not only advances the generation of EC from piPSC through an inhibitor and growth factor cocktail but also provides a promising approach for constructing vascular network-like structures. Importantly, these findings open new avenues for drug discovery in vitro and tissue engineering in vivo.

The progress of induced pluripotent stem cells derived from pigs: a mini review of recent advances

Pigs (Sus scrofa) are widely acknowledged as an important large mammalian animal model due to their similarity to human physiology, genetics, and immunology. Leveraging the full potential of this model presents significant opportunities for major advancements in the fields of comparative biology, disease modeling, and regenerative medicine. Thus, the derivation of pluripotent stem cells from this species can offer new tools for disease modeling and serve as a stepping stone to test future autologous or allogeneic cell-based therapies. Over the past few decades, great progress has been made in establishing porcine pluripotent stem cells (pPSCs), including embryonic stem cells (pESCs) derived from pre- and peri-implantation embryos, and porcine induced pluripotent stem cells (piPSCs) using a variety of cellular reprogramming strategies. However, the stabilization of pPSCs was not as straightforward as directly applying the culture conditions developed and optimized for murine or primate PSCs. Therefore, it has historically been challenging to establish stable pPSC lines that could pass stringent pluripotency tests. Here, we review recent advances in the establishment of stable porcine PSCs. We focus on the evolving derivation methods that eventually led to the establishment of pESCs and transgene-free piPSCs, as well as current challenges and opportunities in this rapidly advancing field.

p53 Activation Facilitates Transdifferentiation of Human Cardiac Fibroblasts into Endothelial Cells

Vascular endothelial cells (ECs), locating at the inner side of vascular lumen, play critical roles in maintaining vascular function and participate in tissue repair and neovascularization. Although increasing studies have shown positive effects of transplantation of vascular ECs or their precursor cells on neovascularization and functional recovery of ischemic tissues, the quantity of in vivo ECs is limited and their quality is affected by age, gender, disease, and others, which hinder their clinical application and further study. Chemical transdifferentiation is a promising approach to generate patient-specific cells. In this process, somatic cells are directly converted into desired cell types without the risk of tumorigenicity by pluripotent cell transplantation and exogenous gene introduction by transgene technology. In the present study, we derived ECs from human cardiac fibroblasts (CFs) through an optimized chemical induction method. The derived ECs expressed endothelial specific markers, took up low-density lipoprotein, secreted angiogenic cytokines under hypoxic condition, and formed microvessels in vitro and in vivo. This CF-EC transition bypassed pluripotency and germ layer differentiation, but underwent a stage of endothelialization. Although p53 maintained the same level during the period of CF-EC transdifferentiation, we could modulate p53 transcriptional activity to further improve cell transition efficiency, which mainly functioned at the later stage of endothelialization. Optimization and exploring the regulatory mechanism of CF-EC transition complement each other, which not only broadens the sources of patient-specific ECs but also provides valuable references for the in vivo direct transdifferentiation study and the elucidation of endothelial development and dysfunction. Impact statement This study provides an optimized chemical induction method to derive endothelial cells (ECs) from human cardiac fibroblasts (CFs), which not only broadens the sources of patient-specific ECs but also provides a good research model of mesenchymal-endothelial transition. Studying the molecular process and regulatory mechanism of CF-EC transdifferentiation will provide valuable references for the in vivo direct transdifferentiation for clinical therapy and deepen the understanding of endothelial development and dysfunction.

Effect and mechanism of hypoxia on differentiation of porcine-induced pluripotent stem cells into vascular endothelial cells

Pigs are similar to humans in organ size and physiological function, and are considered as good models for studying cardiovascular diseases. The study of porcine-induced pluripotent stem cells (piPSC) differentiating into vascular endothelial cells (EC) is expected to open up a new way of obtaining high-quality seed cells. Given that the hypoxic environment has an important role in the differentiation process of vascular EC, this work intends to establish a hypoxia-induced differentiation system of piPSC into vascular EC. There is evidence that the hypoxia microenvironment in the initial stage could significantly improve differentiation efficiency. Further study suggests that the hypoxia culture system supports a combined effect of hypoxia inducible factors and their associated regulatory molecules, such as HIF-1α, VEGFA, FGF2, LDH-A, and PDK1, which can efficiently promote the lineage-specific differentiation of piPSC into EC. Most notably, the high level of ETV2 after 4 d of hypoxic treatment indicates that it possibly plays an important role in the promoting process of EC differentiation. The research is expected to help the establishment of new platforms for piPSC directional induction research, so as to obtain adequate seed cells with ideal phenotype and functionality.

Rapid conversion of porcine pluripotent stem cells into macrophages with chemically defined conditions

A renewable source of porcine macrophages derived from pluripotent stem cells (PSCs) would be a valuable alternative to primary porcine alveolar macrophages (PAMs) in the research of host-pathogen interaction mechanisms. We developed an efficient and rapid protocol, within 11 days, to derive macrophages from porcine PSCs (pPSCs). The pPSC-derived macrophages (pPSCdMs) exhibited molecular and functional characteristics of primary macrophages. The pPSCdMs showed macrophage-specific surface protein expression and macrophage-specific transcription factors, similar to PAMs. The pPSCdMs also exhibited the functional characteristics of macrophages, such as endocytosis, phagocytosis, porcine respiratory and reproductive syndrome virus infection and the response to lipopolysaccharide stimulation. Furthermore, we performed transcriptome sequencing of the whole differentiation process to track the fate transitions of porcine PSCs involved in the signaling pathway. The activation of transforming growth factor beta signaling was required for the formation of mesoderm and the inhibition of the transforming growth factor beta signaling pathway at the hematopoietic endothelium stage could enhance the fate transformation of hematopoiesis. In summary, we developed an efficient and rapid protocol to generate pPSCdMs that showed aspects of functional maturity comparable with PAMs. pPSCdMs could provide a broad prospect for the platforms of host-pathogen interaction mechanisms.

Chemical Transdifferentiation of Somatic Cells: Unleashing the Power of Small Molecules

Chemical transdifferentiation is a technique that utilizes small molecules to directly convert one cell type into another without passing through an intermediate stem cell state. This technique offers several advantages over other methods of cell reprogramming, such as simplicity, standardization, versatility, no ethical and safety concern and patient-specific therapies. Chemical transdifferentiation has been successfully applied to various cell types across different tissues and organs, and its potential applications are rapidly expanding as scientists continue to explore new combinations of small molecules and refine the mechanisms driving cell fate conversion. These applications have opened up new possibilities for regenerative medicine, disease modeling, drug discovery and tissue engineering. However, there are still challenges and limitations that need to be overcome before chemical transdifferentiation can be translated into clinical practice. These include low efficiency and reproducibility, incomplete understanding of the molecular mechanisms, long-term stability and functionality of the transdifferentiated cells, cell-type specificity and scalability. In this review, we compared the commonly used methods for cell transdifferentiation in recent years and discussed the current progress and future perspective of the chemical transdifferentiation of somatic cells and its potential impact on biomedicine. We believe that with ongoing research and technological advancements, the future holds tremendous promise for harnessing the power of small molecules to shape the cellular landscape and revolutionize the field of biomedicine.

Derivation and Characterization of Endothelial Cells from Porcine Induced Pluripotent Stem Cells

Although the study on the regulatory mechanism of endothelial differentiation from the perspective of development provides references for endothelial cell (EC) derivation from pluripotent stem cells, incomplete reprogramming and donor-specific epigenetic memory are still thought to be the obstacles of iPSCs for clinical application. Thus, it is necessary to establish a stable iPSC-EC induction system and investigate the regulatory mechanism of endothelial differentiation. Based on a single-layer culture system, we successfully obtained ECs from porcine iPSCs (piPSCs). In vitro, the derived piPSC-ECs formed microvessel-like structures along 3D gelatin scaffolds. Under pathological conditions, the piPSC-ECs functioned on hindlimb ischemia repair by promoting blood vessel formation. To elucidate the molecular events essential for endothelial differentiation in our model, genome-wide transcriptional profile analysis was conducted, and we found that during piPSC-EC derivation, the synthesis and secretion level of TGF-β as well as the phosphorylation level of Smad2/3 changed dynamically. TGF-β-Smad2/3 signaling activation promoted mesoderm formation and prevented endothelial differentiation. Understanding the regulatory mechanism of iPSC-EC derivation not only paves the way for further optimization, but also provides reference for establishing a cardiovascular drug screening platform and revealing the molecular mechanism of endothelial dysfunction.

Stem Cell-Mediated Angiogenesis in Skin Tissue Engineering and Wound Healing

The timely management of skin wounds has been an unmet clinical need for centuries. While there have been several attempts to accelerate wound healing and reduce the cost of hospitalisation and the healthcare burden, there remains a lack of efficient and effective wound healing approaches. In this regard, stem cell‐based therapies have garnered an outstanding position for the treatment of both acute and chronic skin wounds. Stem cells of different origins (e.g., embryo‐derived stem cells) have been utilised for managing cutaneous lesions; specifically, mesenchymal stem cells (MSCs) isolated from foetal (umbilical cord) and adult (bone marrow) tissues paved the way to more satisfactory outcomes. Since angiogenesis plays a critical role in all four stages of normal wound healing, recent therapeutic approaches have focused on utilising stem cells for inducing neovascularisation. In fact, stem cells can promote angiogenesis via either differentiation into endothelial lineages or secreting pro‐angiogenic exosomes. Furthermore, particular conditions (e.g., hypoxic environments) can be applied in order to boost the pro‐angiogenic capability of stem cells before transplantation. For tissue engineering and regenerative medicine applications, stem cells can be combined with specific types of pro‐angiogenic biocompatible materials (e.g., bioactive glasses) to enhance the neovascularisation process and subsequently accelerate wound healing. As such, this review article summarises such efforts emphasising the bright future that is conceivable when using pro‐angiogenic stem cells for treating acute and chronic skin wounds.