In Vitro Biofabrication of Tissues and Organs

Enhanced chondrogenic differentiation of iPS cell-derived mesenchymal stem/stromal cells via neural crest cell induction for hyaline cartilage repair

Background: To date, there is no effective long-lasting treatment for cartilage tissue repair. Primary chondrocytes and mesenchymal stem/stromal cells are the most commonly used cell sources in regenerative medicine. However, both cell types have limitations, such as dedifferentiation, donor morbidity, and limited expansion. Here, we report a stepwise differentiation method to generate matrix-rich cartilage spheroids from induced pluripotent stem cell-derived mesenchymal stem/stromal cells (iMSCs) via the induction of neural crest cells under xeno-free conditions. Methods: The genes and signaling pathways regulating the chondrogenic susceptibility of iMSCs generated under different conditions were studied. Enhanced chondrogenic differentiation was achieved using a combination of growth factors and small-molecule inducers. Results: We demonstrated that the use of a thienoindazole derivative, TD-198946, synergistically improves chondrogenesis in iMSCs. The proposed strategy produced controlled-size spheroids and increased cartilage extracellular matrix production with no signs of dedifferentiation, fibrotic cartilage formation, or hypertrophy in vivo. Conclusion: These findings provide a novel cell source for stem cell-based cartilage repair. Furthermore, since chondrogenic spheroids have the potential to fuse within a few days, they can be used as building blocks for biofabrication of larger cartilage tissues using technologies such as the Kenzan Bioprinting method.

Implication of Mesenchymal Stem Cells and Their Derivates for Osteochondral Regeneration

Healing of articular cartilage defects presents a challenging issue, due to its regenerative shortcomings. Lacking vascularity and innervation of cartilage and low proliferative potential of chondrocytes are the main reasons for the limited healing potential of articular cartilage. Traditional reparative approaches are limited in their efficiency, hence there is a demand for novel reparative treatments. Mesenchymal stromal cells, preferred for clinical uses, can be readily derived from various sources and have been proven to have a therapeutic effect on cartilage and subchondral bone. Therefore, mesenchymal stromal cells, their derivates, and scaffolds have been utilized in research targeting osteochondral regeneration. The present review aims to comprehensively outline and discuss literature considering this topic published within last 5 years.

Tackling Current Biomedical Challenges With Frontier Biofabrication and Organ-On-A-Chip Technologies

In the last decades, biomedical research has significantly boomed in the academia and industrial sectors, and it is expected to continue to grow at a rapid pace in the future. An in-depth analysis of such growth is not trivial, given the intrinsic multidisciplinary nature of biomedical research. Nevertheless, technological advances are among the main factors which have enabled such progress. In this review, we discuss the contribution of two state-of-the-art technologies-namely biofabrication and organ-on-a-chip-in a selection of biomedical research areas. We start by providing an overview of these technologies and their capacities in fabricating advanced in vitro tissue/organ models. We then analyze their impact on addressing a range of current biomedical challenges. Ultimately, we speculate about their future developments by integrating these technologies with other cutting-edge research fields such as artificial intelligence and big data analysis.

Scaffold-Free Bio-3D Printing Using Spheroids as "Bio-Inks" for Tissue (Re-)Construction and Drug Response Tests

In recent years, scaffold-free bio-3D printing using cell aggregates (spheroids) as "bio-inks" has attracted increasing attention as a method for 3D cell construction. Bio-3D printing uses a technique called the Kenzan method, wherein spheroids are placed one-by-one in a microneedle array (the "Kenzan") using a bio-3D printer. The bio-3D printer is a machine that was developed to perform bio-3D printing automatically. Recently, it has been reported that cell constructs can be produced by a bio-3D printer using spheroids composed of many types of cells and that this can contribute to tissue (re-)construction. This progress report summarizes the production and effectiveness of various cell constructs prepared using bio-3D printers. It also considers the future issues and prospects of various cell constructs obtained by using this method for further development of scaffold-free 3D cell constructions.

Cardiac regeneration using human-induced pluripotent stem cell-derived biomaterial-free 3D-bioprinted cardiac patch in vivo

One of the leading causes of death worldwide is heart failure. Despite advances in the treatment and prevention of heart failure, the number of affected patients continues to increase. We have recently developed 3D-bioprinted biomaterial-free cardiac tissue that has the potential to improve cardiac function. This study aims to evaluate the in vivo regenerative potential of these 3D-bioprinted cardiac patches. The cardiac patches were generated using 3D-bioprinting technology in conjunction with cellular spheroids created from a coculture of human-induced pluripotent stem cell-derived cardiomyocytes, fibroblasts, and endothelial cells. Once printed and cultured, the cardiac patches were implanted into a rat myocardial infarction model (n = 6). A control group (n = 6) without the implantation of cardiac tissue patches was used for comparison. The potential for regeneration was measured 4 weeks after the surgery with histology and echocardiography. 4 weeks after surgery, the survival rates were 100% and 83% in the experimental and the control group, respectively. In the cardiac patch group, the average vessel counts within the infarcted area were higher than those within the control group. The scar area in the cardiac patch group was significantly smaller than that in the control group. (Figure S1) Echocardiography showed a trend of improvement of cardiac function for the experimental group, and this trend correlated with increased patch production of extracellular vesicles. 3D-bioprinted cardiac patches have the potential to improve the regeneration of cardiac tissue and promote angiogenesis in the infarcted tissues and reduce the scar tissue formation.

Development of an immunodeficient pig model allowing long-term accommodation of artificial human vascular tubes

Before they are used in the clinical setting, the effectiveness of artificially produced human-derived tissue-engineered medical products should be verified in an immunodeficient animal model, such as severe combined immunodeficient mice. However, small animal models are not sufficient to evaluate large-sized products for human use. Thus, an immunodeficient large animal model is necessary in order to properly evaluate the clinical efficacy of human-derived tissue-engineered products, such as artificial grafts. Here we report the development of an immunodeficient pig model, the operational immunodeficient pig (OIDP), by surgically removing the thymus and spleen, and creating a controlled immunosuppressive protocol using a combination of drugs commonly used in the clinical setting. We find that this model allows the long-term accommodation of artificial human vascular grafts. The development of the OIDP is an essential step towards a comprehensive and clinically relevant evaluation of human cell regeneration strategies at the preclinical stage.

The development of tissue-engineered vascular grafts heavily relies on the availability of large animal models that allow long-term assessment of graft patency. Here Itoh et al. propose a novel model of immunodeficient pigs that allows long-term accommodation of human cell-derived three-dimensional bioprinted vascular tubes.

Replacement of Rat Tracheas by Layered, Trachea-Like, Scaffold-Free Structures of Human Cells Using a Bio-3D Printing System

Current scaffold-based tissue engineering approaches are subject to several limitations, such as design inflexibility, poor cytocompatibility, toxicity, and post-transplant degradation. Thus, scaffold-free tissue-engineered structures can be a promising solution to overcome the issues associated with classical scaffold-based materials in clinical transplantation. The present study seeks to optimize the culture conditions and cell combinations used to generate scaffold-free structures using a Bio-3D printing system. Human cartilage cells, human fibroblasts, human umbilical vein endothelial cells, and human mesenchymal stem cells from bone marrow are aggregated into spheroids and placed into a Bio-3D printing system with dedicated needles positioned according to 3D configuration data, to develop scaffold-free trachea-like tubes. Culturing the Bio-3D-printed structures with proper flow of specific medium in a bioreactor facilitates the rearrangement and self-organization of cells, improving physical strength and tissue function. The Bio-3D-printed tissue forms small-diameter trachea-like tubes that are implanted into rats with the support of catheters. It is confirmed that the tubes are viable in vivo and that the tracheal epithelium and capillaries proliferate. This tissue-engineered, scaffold-free, tubular structure can represent a significant step toward clinical application of bioengineered organs.

Scaffold-Free Tubular Tissues Created by a Bio-3D Printer Undergo Remodeling and Endothelialization when Implanted in Rat Aortae

BACKGROUND

Small caliber vascular prostheses are not clinically available because synthetic vascular prostheses lack endothelial cells which modulate platelet activation, leukocyte adhesion, thrombosis, and the regulation of vasomotor tone by the production of vasoactive substances. We developed a novel method to create scaffold-free tubular tissue from multicellular spheroids (MCS) using a "Bio-3D printer"-based system. This system enables the creation of pre-designed three-dimensional structures using a computer controlled robotics system. With this system, we created a tubular structure and studied its biological features.

METHODS AND RESULTS

Using a "Bio-3D printer," we made scaffold-free tubular tissues (inner diameter of 1.5 mm) from a total of 500 MCSs (2.5× 104 cells per one MCS) composed of human umbilical vein endothelial cells (40%), human aortic smooth muscle cells (10%), and normal human dermal fibroblasts (50%). The tubular tissues were cultured in a perfusion system and implanted into the abdominal aortas of F344 nude rats. We assessed the flow by ultrasonography and performed histological examinations on the second (n = 5) and fifth (n = 5) day after implantation. All grafts were patent and remodeling of the tubular tissues (enlargement of the lumen area and thinning of the wall) was observed. A layer of endothelial cells was confirmed five days after implantation.

CONCLUSIONS

The scaffold-free tubular tissues made of MCS using a Bio-3D printer underwent remodeling and endothelialization. Further studies are warranted to elucidate the underlying mechanism of endothelialization and its function, as well as the long-term results.

A preliminary study of osteochondral regeneration using a scaffold-free three-dimensional construct of porcine adipose tissue-derived mesenchymal stem cells

BACKGROUND

Osteoarthritis (OA) is a major joint disease in humans and many other animals. Consequently, medical countermeasures for OA have been investigated diligently. This study was designed to examine the regeneration of articular cartilage and subchondral bone using three-dimensional (3D) constructs of adipose tissue-derived mesenchymal stem cells (AT-MSCs).

METHODS

AT-MSCs were isolated and expanded until required for genetical and immunological analysis and construct creation. A construct consisting of about 760 spheroids that each contained 5.0 × 10(4) autologous AT-MSCs was implanted into an osteochondral defect (diameter: 4 mm; depth: 6 mm) created in the femoral trochlear groove of two adult microminipigs. After implantation, the defects were monitored by computed tomography every month for 6 months in animal no. 1 and 12 months in animal no. 2.

RESULTS

AT-MSCs were confirmed to express the premature genes and to be positive for CD90 and CD105 and negative for CD34 and CD45. Under specific nutrient conditions, the AT-MSCs differentiated into osteogenic, chondrogenic, and adipogenic lineages, as evidenced by the expressions of related marker genes and the production of appropriate matrix molecules. A radiopaque area emerged from the boundary between the bone and the implant and increased more steadily upward and inward for the implants in both animal no. 1 and animal no. 2. The histopathology of the implants after 6 months revealed active endochondral ossification underneath the plump fibrocartilage in animal no. 1. The histopathology after 12 months in animal no. 2 showed not only that the diminishing fibrocartilage was as thick as the surrounding normal cartilage but also that massive subchondral bone was present.

CONCLUSIONS

The present results suggest that implantation of a scaffold-free 3D construct of AT-MSCs into an osteochondral defect may induce regeneration of the original structure of the cartilage and subchondral bone over the course of 1 year, although more experimental cases are needed.