Fabrication of tissue-engineered cell sheets by automated cell culture equipment

Engineering cell-derived extracellular matrix for peripheral nerve regeneration

Extracellular matrices (ECMs) play a key role in nerve repair and are recognized as the natural source of biomaterials. In parallel to extensively studied tissue-derived ECMs (ts-ECMs), cell-derived ECMs (cd-ECMs) also have the capability to partially recapitulate the complicated regenerative microenvironment of native nerve tissues. Notably, cd-ECMs can avoid the shortcomings of ts-ECMs. Cd-ECMs can be prepared by culturing various cells or even autologous cells in vitro under pathogen-free conditions. And mild decellularization can achieve efficient removal of immunogenic components in cd-ECMs. Moreover, cd-ECMs are more readily customizable to achieve the desired functional properties. These advantages have garnered significant attention for the potential of cd-ECMs in neuroregenerative medicine. As promising biomaterials, cd-ECMs bring new hope for the effective treatment of peripheral nerve injuries. Herein, this review comprehensively examines current knowledge about the functional characteristics of cd-ECMs and their mechanisms of interaction with cells in nerve regeneration, with a particular focus on the preparation, engineering optimization, and scalability of cd-ECMs. The applications of cd-ECMs from distinct cell sources reported in peripheral nerve tissue engineering are highlighted and summarized. Furthermore, current limitations that should be addressed and outlooks related to clinical translation are put forward as well.

Extracellular matrix-derived materials for tissue engineering and regenerative medicine: A journey from isolation to characterization and application

Biomaterial choice is an essential step during the development tissue engineering and regenerative medicine (TERM) applications. The selected biomaterial must present properties allowing the physiological-like recapitulation of several processes that lead to the reestablishment of homeostatic tissue or organ function. Biomaterials derived from the extracellular matrix (ECM) present many such properties and their use in the field has been steadily increasing. Considering this growing importance, it becomes imperative to provide a comprehensive overview of ECM biomaterials, encompassing their sourcing, processing, and integration into TERM applications. This review compiles the main strategies used to isolate and process ECM-derived biomaterials as well as different techniques used for its characterization, namely biochemical and chemical, physical, morphological, and biological. Lastly, some of their applications in the TERM field are explored and discussed.

SAGAS: Simulated annealing and greedy algorithm scheduler for laboratory automation

During laboratory automation of life science experiments, coordinating specialized instruments and human experimenters for various experimental procedures is important to minimize the execution time. In particular, the scheduling of life science experiments requires the consideration of time constraints by mutual boundaries (TCMB) and can be formulated as the "scheduling for laboratory automation in biology" (S-LAB) problem. However, existing scheduling methods for the S-LAB problems have difficulties in obtaining a feasible solution for large-size scheduling problems at a time sufficient for real-time use. In this study, we proposed a fast schedule-finding method for S-LAB problems, SAGAS (Simulated annealing and greedy algorithm scheduler). SAGAS combines simulated annealing and the greedy algorithm to find a scheduling solution with the shortest possible execution time. We have performed scheduling on real experimental protocols and shown that SAGAS can search for feasible or optimal solutions in practicable computation time for various S-LAB problems. Furthermore, the reduced computation time by SAGAS enables us to systematically search for laboratory automation with minimum execution time by simulating scheduling for various laboratory configurations. This study provides a convenient scheduling method for life science automation laboratories and presents a new possibility for designing laboratory configurations.

Development of cell-laden multimodular Lego-like customizable endometrial tissue assembly for successful tissue regeneration

BACKGROUND

The endometrium, the inner lining of the uterine cavity, plays essential roles in embryo implantation and its subsequent development. Although some positive results were preliminarily archived, the regeneration of damaged endometrial tissues by administrating stem cells only is very challenging due to the lack of specific microenvironments and their low attachment rates at the sites of injury. In this context, various biomaterial-based scaffolds have been used to overcome these limitations by providing simple structural support for cell attachment. However, these scaffold-based strategies also cannot properly reflect patient tissue-specific structural complexity and thus show only limited therapeutic effects.

METHOD

Therefore, in the present study, we developed a customizable Lego-like multimodular endometrial tissue architecture by assembling individually fabricated tissue blocks.

RESULTS

Each tissue block was fabricated by incorporating biodegradable biomaterials and certain endometrial constituent cells. Each small tissue block was effectively fabricated by integrating conventional mold casting and 3D printing techniques. The fabricated individual tissue blocks were properly assembled into a larger customized tissue architecture. This structure not only properly mimics the patient-specific multicellular microenvironment of the endometrial tissue but also properly responds to key reproductive hormones in a manner similar to the physiological functions.

CONCLUSION

This customizable modular tissue assembly allows easy and scalable configuration of a complex patient-specific tissue microenvironment, thus accelerating various tissue regeneration procedures.

Manufacture and Quality Control of Human Umbilical Cord-Derived Mesenchymal Stem Cell Sheets for Clinical Use

Human umbilical cord-derived mesenchymal stem cell (UC−MSC) sheets have attracted much attention in cell therapy. However, the culture media and coating matrix used for the preparation of UC−MSC sheets have not been safe enough to comply with current clinical drug standards. Moreover, the UC−MSC sheet preservation systems developed before did not comply with Good Manufacturing Practice (GMP) regulations. In this study, the culture medium and coating matrix were developed for UC−MSC sheet production to comply with clinical drug standards. Additionally, the GMP-compliant preservation solution and method for the UC−MSC sheet were developed. Then, quality standards of the UC−MSC sheet were formulated according to national and international regulations for drugs. Finally, the production process of UC−MSC sheets on a large scale was standardized, and three batches of trial production were conducted and tested to meet the established quality standards. This research provides the possibility for clinical trials of UC−MSC sheet products in the development stage of new drugs and lays the foundation for industrial large-scale production after the new drug is launched.

Point-of-use, automated fabrication of a 3D human liver model supplemented with human adipose microvessels

Advanced in vitro tissue models better reflect healthy and disease tissue conditions in the body. However, complex tissue models are often manufactured using custom solutions and can be challenging to manufacture to scale. Here, we describe the automated fabrication of a cell-dense, thick (≤ 1 cm), human vascularized liver tissue model using a robotic biomanufacturing platform and off-the-shelf components to build, culture, and sample liver tissues hands-free without compromising tissue health or function. Fabrication of the tissue involved 3D bioprinting and incorporation of primary human hepatocytes, primary human non-parenchymal cells, and isolated fragments of intact human microvessels as vascular precursors. No differences were observed in select assessments of the liver tissues fabricated by hand or via automation. Furthermore, constant media exchange, via perfusion, improved urea output and elevated tissue metabolism. Interestingly, inclusion of adipose-derived human microvessels enhanced functional gene expression, including an enhanced response to a drug challenge. Our results describe the fabrication of a thick liver tissue environment useful for a variety of applications including liver disease modeling, infectious agent studies, and cancer investigations. We expect the automated fabrication of the vascularized liver tissue, at the point of use and using off-the-shelf platforms, eases fabrication of the complex model and increases its utility.

Robotic search for optimal cell culture in regenerative medicine

Induced differentiation is one of the most experience- and skill-dependent experimental processes in regenerative medicine, and establishing optimal conditions often takes years. We developed a robotic AI system with a batch Bayesian optimization algorithm that autonomously induces the differentiation of induced pluripotent stem cell-derived retinal pigment epithelial (iPSC-RPE) cells. From 200 million possible parameter combinations, the system performed cell culture in 143 different conditions in 111 days, resulting in 88% better iPSC-RPE production than that obtained by the pre-optimized culture in terms of the pigmentation scores. Our work demonstrates that the use of autonomous robotic AI systems drastically accelerates systematic and unbiased exploration of experimental search space, suggesting immense use in medicine and research.

Optimal Scheduling for Laboratory Automation of Life Science Experiments with Time Constraints

In automated laboratories consisting of multiple different types of instruments, scheduling algorithms are useful for determining the optimal allocations of instruments to minimize the time required to complete experimental procedures. However, previous studies on scheduling algorithms for laboratory automation have not emphasized the time constraints by mutual boundaries (TCMBs) among operations, which is important in procedures involving live cells or unstable biomolecules. Here, we define the "scheduling for laboratory automation in biology" (S-LAB) problem as a scheduling problem for automated laboratories in which operations with TCMBs are performed by multiple different instruments. We formulate an S-LAB problem as a mixed-integer programming (MIP) problem and propose a scheduling method using the branch-and-bound algorithm. Simulations show that our method can find the optimal schedules of S-LAB problems that minimize overall execution time while satisfying the TCMBs. Furthermore, we propose the use of our scheduling method for the simulation-based design of job definitions and laboratory configurations.

Fabrication and Characterization of Graphene Oxide-Coated Plate for Efficient Culture of Stem Cells

BACKGROUND

For stem cell applications in regenerative medicine, it is very important to produce high-quality stem cells in large quantities in a short time period. Recently, many studies have shown big potential of graphene oxide as a biocompatible substance to enhance cell growth. We investigated if graphene oxide-coated culture plate can promote production efficiency of stem cells.

METHODS

Three types of graphene oxide were used for this study. They are highly concentrated graphene oxide solution, single-layer graphene oxide solution, and ultra-highly concentrated single-layer graphene oxide solution with different single-layer ratios, and coated on cell culture plates using a spray coating method. Physiochemical and biological properties of graphene oxide-coated surface were analyzed by atomic force microscope (AFM), scanning electron microscope (SEM), cell counting kit, a live/dead assay kit, and confocal imaging.

RESULTS

Graphene oxide was evenly coated on cell culture plates with a roughness of 6.4 ~ 38.2 nm, as measured by SEM and AFM. Young's Modulus value was up to 115.1 GPa, confirming that graphene oxide was strongly glued to the surface. The ex vivo stem cell expansion efficiency was enhanced as bone marrow-derived stem cell doubling time on the graphene oxide decreased compared to the control (no graphene oxide coating), from 64 to 58 h, and the growth rate increased up to 145%. We also observed faster attachment and higher affinity of stem cells to the graphene oxide compared to control by confocal microscope.

CONCLUSION

This study demonstrated that graphene oxide dramatically enhanced the ex vivo expansion efficiency of stem cells. Spray coating enabled an ultra-thin coating of graphene oxide on cell culture plates. The results supported that utilization of graphene oxide on culture plates can be a promising mean for mass production of stem cells for commercial applications.

Analysis of extracellular vesicles as a potential index for monitoring differentiation of neural lineage cells from induced pluripotent stem cells

To improve cell production efficacy, it is important to evaluate cell conditions during culture. Extracellular vesicles (EVs) secreted from various cells are involved in stem cell differentiation. As EVs carry information about their source cells, we hypothesized that they may serve as a noninvasive index of cell conditions. We evaluated changes in EV morphology, concentration, and microRNA (miRNA) and protein expression in culture supernatants during the differentiation of induced pluripotent stem cells (iPSCs) into neural lineage cells, for application in regenerative medicine for Parkinson's disease. We observed EVs (50-150 nm) in culture supernatants of iPSCs and differentiated cells. The EVs expressed the exosome markers CD63, CD81, and CD9. Throughout differentiation, the EV concentration in the supernatants decreased, and EV miRNA and protein expression changed substantially. Especially, miR-106b, involved in neural stem cell differentiation and normal brain development, was considerably downregulated. CD63 expression correlated with the CORIN-positive cell rate, which is an index of differentiation. Thus, EV concentration and miRNA and protein expression may reflect the differentiation status of iPSCs. These findings pave the way for the development of novel and sensitive cell culture monitoring methods.

Comparison of cultured cell attachment on a temperature-responsive polymer, poly-L-lysine, and collagen using modeling curves and a thermal-controlled quartz crystal microbalance

The characteristics of cultured cell attachment onto poly-L-lysine (PLL), collagen, and the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM) were studied using a quartz crystal microbalance (QCM). A QCM with microscope cameras enclosed in a Peltier chamber was developed to enable QCM measurements and microphotographic imaging to be conducted in a temperature-controlled CO₂ incubator. Human hepatoma cell line HepG2 cells were cultured on the quartz crystals coated with PLL, collagen, and PNIPAM. Response curves of the resonant frequency of the quartz crystals during the cell attachment process were analyzed on the basis of the parameters of modeling curves fit to the experimentally obtained curves. Analysis of the fitting curves showed that the time constants of the first-lag response were 11 h for PLL, 16 h for collagen, and 38 h for PNIPAM and that the frequency change for the PNIPAM films was six times smaller than those for the PLL and collagen films. These findings were supported by photographic images showing wider cell spread on PLL and collagen than on PNIPAM. The response of cells on PNIPAM was measured during a thermal cycle from 37 to 20 °C to 37 °C. In the resonance frequency-resonance resistance (F-R) diagram, the slopes of ΔR/ΔF corresponding to the cell attachment process and those corresponding to the thermal cycling process differed; the positions in the F-R diagram also shifted to higher resonant frequencies after the thermal cycle. These results suggested that the mass effect decreased as a result of the weakening of the cell attachment strength by the thermal cycle because the molecular brushes of PNIPAM were disarranged.

Scaffold-free cell-based tissue engineering therapies: advances, shortfalls and forecast

Cell-based scaffold-free therapies seek to develop in vitro organotypic three-dimensional (3D) tissue-like surrogates, capitalising upon the inherent capacity of cells to create tissues with efficiency and sophistication that is still unparalleled by human-made devices. Although automation systems have been realised and (some) success stories have been witnessed over the years in clinical and commercial arenas, in vitro organogenesis is far from becoming a standard way of care. This limited technology transfer is largely attributed to scalability-associated costs, considering that the development of a borderline 3D implantable device requires very high number of functional cells and prolonged ex vivo culture periods. Herein, we critically discuss advancements and shortfalls of scaffold-free cell-based tissue engineering strategies, along with pioneering concepts that have the potential to transform regenerative and reparative medicine.

A Variable Scheduling Maintenance Culture Platform for Mammalian Cells

Cell culturing is a basic experimental technique in cell biology and medical science. However, culturing high-quality cells with a high degree of reproducibility relies heavily on expert skills and tacit knowledge, and it is not straightforward to scale the production process due to the education bottleneck. Although many automated culture systems have been developed and a few have succeeded in mass production environments, very few robots are permissive of frequent protocol changes, which are often required in basic research environments. LabDroid is a general-purpose humanoid robot with two arms that performs experiments using the same tools as humans. Combining our newly developed AI software with LabDroid, we developed a variable scheduling system that continuously produces subcultures of cell lines without human intervention. The system periodically observes the cells on plates with a microscope, predicts the cell growth curve by processing cell images, and decides the best times for passage. We have succeeded in developing a system that maintains the cultures of two HEK293A cell plates with no human intervention for 192 h.

Regenerative medicine for the upper gastrointestinal tract

The main surgical strategy for gastrointestinal tract malignancy is en bloc resection, which consists of not only resection of the involved organs but also simultaneous resection of the surrounding or adjacent mesenteries that contain lymph vessels and nodes. After resection of the diseased organs, the defect of the gastrointestinal conduit is replaced with organs located downstream, such as the stomach and jejunum. However, esophageal and gastric reconstruction using these natural substitutes is associated with a diminished quality of life due to the loss of the reserve function, damage to the antireflux barrier, and dumping syndrome. Thus, replacement of the deficit after resection with the patient's own regenerated tissue to compensate for the lost function and tissue using regenerative medicine will be an ideal treatment. Many researchers have been trying to construct artificial organs through tissue engineering techniques; however, none have yet succeeded in growing a whole organ because of the complicated functions these organs perform, such as the processing and absorption of nutrients. While exciting results have been reported with regard to tissue engineering techniques concerning the upper gastrointestinal tract, such as the esophagus and stomach, most of these achievements have been observed in animal models, and few successful approaches in the clinical setting have been reported for the replacement of mucosal defects. We review the recent progress in regenerative medicine in relation to the upper gastrointestinal tract, such as the esophagus and stomach. We also focus on the functional capacity of regenerated tissue and its role as a culture system to recapitulate the mechanisms underlying infectious disease. With the emergence of technology such as the fabrication of decellularized constructs, organoids and cell sheet medicine, collaboration between gastrointestinal surgery and regenerative medicine is expected to help establish novel therapeutic modalities in the future.

Thermoresponsive surfaces designed for the proliferation and differentiation of human pluripotent stem cells

Thermoresponsive surfaces enable the detachment of cells or cell sheets by decreasing the temperature of the surface when harvesting the cells. However, human pluripotent stem cells (hPSCs), such as embryonic stem cells and induced pluripotent stem cells, cannot be directly cultured on a thermoresponsive surface; hPSCs need a specific extracellular matrix to bind to the integrin receptors on their surfaces. We prepared a thermoresponsive surface by using poly(N-isopropylacrylamide-co-butylacrylate) and recombinant vitronectin to provide an optimal coating concentration for the hPSC culture. hPSCs can be cultured on the same thermoresponsive surface for 5 passages by partial detachment of the cells from the surface by decreasing the temperature for 30 min; then, the remaining hPSCs were subsequently cultured on the same dishes following the addition of new cultivation media. The detached cells, even after continual culture for five passages, showed high pluripotency, the ability to differentiate into cells derived from the 3 germ layers and the ability to undergo cardiac differentiation.

Fabrication of tissue-engineered cell sheets by automated cell culture equipment

Most cells for regenerative medicine are currently cultured manually. In order to promote the widespread use of regenerative medicine, it will be necessary to develop automated culture techniques so that cells can be produced in greater quantities at lower cost and with more stable quality. In the field of regenerative medicine technology, cell sheet therapy is an effective tissue engineering technique whereby cells can be grafted by attaching them to a target site. We have developed automated cell culture equipment to promote the use of this cell sheet regenerative treatment. This equipment features a fully closed culture vessel and circuit system that avoids contamination with bacteria and the like from the external environment, and it was designed to allow 10 cell sheets to be simultaneously cultured in parallel. We used this equipment to fabricate 50 sheets of human oral mucosal epithelial cells in five automated culture tests in this trial. By analyzing these sheets, we confirmed that 49 of the 50 sheets satisfied the quality standards of clinical research. To compare the characteristics of automatically fabricated cell sheets with those of manually fabricated cell sheets, we performed histological analyses using immunostaining and transmission electron microscopy. The results confirmed that cell sheets fabricated with the automated cell culture are differentiated in the same way as cultures fabricated manually.