A novel recovery system for cultured cells using plasma-treated polystyrene dishes grafted with poly(N-isopropylacrylamide)

Effect of Solvent Properties on the Critical Solution Temperature of Thermoresponsive Polymers

The ability of thermoresponsive polymers to respond to temperature with a reversible conformational change makes them promising 'smart' materials for solutions in medical and biotechnological applications. In this work, two such polymers and structural isomers were studied: poly(N-isopropyl acrylamide) (PNiPAm) and poly(2-isopropyl-2-oxazoline) (PiPOx). We compare the critical solution temperatures (CST) of these polymers in D2O and H2O in the presence of Hofmeister series salts, as results obtained under these different solvent conditions are often compared. D2O has a higher dipole moment and electronegativity than H2O, which could significantly alter the CST transition. We used two complementary methods to measure the CST, dynamic light scattering (DLS) and differential scanning calorimetry (DSC) and found that the CST decreased significantly in D2O compared to H2O. In the presence of highly concentrated kosmotropes, the CST of both polymers decreased in both solvents. The influence of the kosmotropic anions was smaller than the water isotope effect at low ionic strengths but considerably higher at physiological ionic strengths. However, the Hofmeister anion effect was quantitatively different in H2O than in D2O, with the largest relative differences observed for Cl-, where the CSTs in D2O decreased more than in H2O measured by DLS but less by DSC. PiPOx was more sensitive than PNiPAm to the presence of chaotropes. It exhibited much higher transition enthalpies and multistep transitions, especially in aqueous solutions. Our results highlight that measurements of thermoresponsive polymer properties in D2O cannot be compared directly or quantitatively to application conditions or even measurements performed in H2O.

Current Status of Cardiac Regenerative Therapy Using Induced Pluripotent Stem Cells

Heart failure (HF) is a life-threatening disorder and is treated by drug therapies and surgical interventions such as heart transplantation and left ventricular assist device (LVAD). However, these treatments can lack effectiveness in the long term and are associated with issues such as donor shortage in heart transplantation, and infection, stroke, or gastrointestinal bleeding in LVADs. Therefore, alternative therapeutic strategies are still needed. In this respect, stem cell therapy has been introduced for the treatment of HF and numerous preclinical and clinical studies are employing a range of stem cell varieties. These stem cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), have been shown to improve cardiac function and attenuate left ventricular remodeling. IPSCs, which have a capacity for unlimited proliferation and differentiation into cardiomyocytes, are a promising cell source for myocardial regeneration therapy. In this review, we discuss the following topics: (1) what are iPSCs; (2) the limitations and solutions for the translation of iPSC-CMs practically; and (3) the current therapeutic clinical trials.

The potential of graphene coatings as neural interfaces

Recent advances in nanotechnology design and fabrication have shaped the landscape for the development of ideal cell interfaces based on biomaterials. A holistic evaluation of the requirements for a cell interface is a highly complex task. Biocompatibility is a crucial requirement which is affected by the interface's properties, including elemental composition, morphology, and surface chemistry. This review explores the current state-of-the-art on graphene coatings produced by chemical vapor deposition (CVD) and applied as neural interfaces, detailing the key properties required to design an interface capable of physiologically interacting with neural cells. The interfaces are classified into substrates and scaffolds to differentiate the planar and three-dimensional environments where the cells can adhere and proliferate. The role of specific features such as mechanical properties, porosity and wettability are investigated. We further report on the specific brain-interface applications where CVD graphene paved the way to revolutionary advances in biomedicine. Future studies on the long-term effects of graphene-based materials in vivo will unlock even more potentially disruptive neuro-applications.

A Self-Homing and Traceable Cardiac Patch Leveraging Ferumoxytol for Spatiotemporal Therapeutic Delivery

Mesenchymal stem cell (MSC)-based cardiac patches are envisioned to be a promising treatment option for patients with myocardial infarction. However, their therapeutic efficacy and duration are hampered due to their limited retention on the epicardium. We engineered a scaffold-free MSC sheet with an inherent ability to migrate into the infarcted myocardium, a strategy enabled by actively establishing a sustained intracellular hypoxic environment through the endocytosis of our FDA-approved ferumoxytol. This iron oxide nanoparticle stabilized hypoxia-induced factor-1α, triggering upregulation of the CXC chemokine receptor and subsequent MSC chemotaxis. Thus, MSCs integrated into 2/3 depth of the left ventricular anterior wall in a rat model of acute myocardial infarction and persisted for at least 28 days. This led to spatiotemporal delivery of paracrine factors by MSCs, enhancing cardiac regeneration and function. Ferumoxytol also facilitated the noninvasive MRI tracking of implanted MSCs. Our approach introduces a strategy for mobilizing MSC migration, holding promise for rapid clinical translation in myocardial infarction treatment.

Production of alginate macrocapsule device for long-term normoglycaemia in the treatment of type 1 diabetes mellitus with pancreatic cell sheet engineering

Type 1 diabetes-mellitus (T1DM) is characterized by damage of beta cells in pancreatic islets. Cell-sheet engineering, one of the newest therapeutic approaches, has also been used to create functional islet systems by creating islet/beta cell-sheets and transferring these systems to areas that require minimally invasive intervention, such as extrahepatic areas. Since islets, beta cells, and pancreas transplants are allogeneic, immune problems such as tissue rejection occur after treatment, and patients become insulin dependent again. In this study, we aimed to design the most suitable cell-sheet treatment method and macrocapsule-device that could provide long-term normoglycemia in rats. Firstly, mesenchymal stem cells (MSCs) and beta cells were co-cultured in a temperature-responsive culture dish to obtain a cell-sheet and then the cell-sheets macroencapsulated using different concentrations of alginate. The mechanical properties and pore sizes of the macrocapsule-device were characterized. The viability and activity of cell-sheets in the macrocapsule were evaluatedin vitroandin vivo. Fasting blood glucose levels, body weight, and serum insulin & C-peptide levels were evaluated after transplantation in diabetic-rats. After the transplantation, the blood glucose level at 225 mg dl-1on the 10th day dropped to 168 mg dl-1on the 15th day, and remained at the normoglycemic level for 210 days. In this study, an alginate macrocapsule-device was successfully developed to protect cell-sheets from immune attacks after transplantation. The results of our study provide the basis for future animal and human studies in which this method can be used to provide long-term cellular therapy in T1DM patients.

Applications of Scaffolds in Tissue Engineering: Current Utilization and Future Prospective

Current regenerative medicine tactics focus on regenerating tissue structures pathologically modified by cell transplantation in combination with supporting scaffolds and biomolecules. Natural and synthetic polymers, bioresorbable inorganic and hybrid materials, and tissue decellularized were deemed biomaterials scaffolding because of their improved structural, mechanical, and biological abilities.Various biomaterials, existing treatment methodologies and emerging technologies in the field of Three-dimensional (3D) and hydrogel processing, and the unique fabric concerns for tissue engineering. A scaffold that acts as a transient matrix for cell proliferation and extracellular matrix deposition, with subsequent expansion, is needed to restore or regenerate the tissue. Diverse technologies are combined to produce porous tissue regenerative and tailored release of bioactive substances in applications of tissue engineering. Tissue engineering scaffolds are crucial ingredients. This paper discusses an overview of the various scaffold kinds and their material features and applications. Tabulation of the manufacturing technologies for fabric engineering and equipment, encompassing the latest fundamental and standard procedures.

Cell Therapy Approaches for Articular Cartilage Regeneration

Articular cartilage is a common cartilage type found in a multitude of joints throughout the human body. However, cartilage is limited in its regenerative capacity. A range of methods have been employed to aid adults under the age of 45 with cartilage defects, but other cartilage pathologies such as osteoarthritis are limited to non-steroidal anti-inflammatory drugs and total joint arthroplasty. Cell therapies and synthetic biology can be utilized to assist not only cartilage defects but have the potential as a therapeutic approach for osteoarthritis as well. In this review, we will cover current cell therapy approaches for cartilage defect regeneration with a focus on autologous chondrocyte implantation and matrix autologous chondrocyte implantation. We will then discuss the potential of stem cells for cartilage repair in osteoarthritis and the use of synthetic biology to genetically engineer cells to promote cartilage regeneration and potentially reverse osteoarthritis.

Covalent Immobilization of Collagen Type I to a Polydimethylsiloxane Surface for Preventing Cell Detachment by Retaining Collagen Molecules under Uniaxial Cyclic Mechanical Stretching Stress

Surface modification of polydimethylsiloxane (PDMS) with an extracellular matrix (ECM) is useful for enhancing stable cell attachment. However, few studies have investigated the correlation between the stability of deposited ECM and cell behavior on the PDMS surfaces in external stretched cell culture systems. Herein, covalent collagen type I (Col)-immobilized PDMS surfaces were fabricated using 3-aminopropyl-trimethoxysilane, glutaraldehyde, and Col molecules. The immobilized collagen molecules on the PDMS surface were more stable and uniform than the physisorbed collagen. The cells stably adhered to the Col-immobilized surface and proliferated even under uniaxial cyclic mechanical stretching stress (UnCyMSt), whereas the cells gradually detached from the Col-physisorbed PDMS surface, accompanied by a decrease in the number of deposited collagen molecules. Moreover, the immobilization of collagen molecules enhanced cell alignment under the UnCyMSt. This study reveals that cell adhesion, proliferation, and alignment under the UnCyMSt can be attributed to the retention of collagen molecules on the PDMS surface.

Translational biomaterials of four-dimensional bioprinting for tissue regeneration

Bioprinting is an additive manufacturing technique that combines living cells, biomaterials, and biological molecules to develop biologically functional constructs. Three-dimensional (3D) bioprinting is commonly used as anin vitromodeling system and is a more accurate representation ofin vivoconditions in comparison to two-dimensional cell culture. Although 3D bioprinting has been utilized in various tissue engineering and clinical applications, it only takes into consideration the initial state of the printed scaffold or object. Four-dimensional (4D) bioprinting has emerged in recent years to incorporate the additional dimension of time within the printed 3D scaffolds. During the 4D bioprinting process, an external stimulus is exposed to the printed construct, which ultimately changes its shape or functionality. By studying how the structures and the embedded cells respond to various stimuli, researchers can gain a deeper understanding of the functionality of native tissues. This review paper will focus on the biomaterial breakthroughs in the newly advancing field of 4D bioprinting and their applications in tissue engineering and regeneration. In addition, the use of smart biomaterials and 4D printing mechanisms for tissue engineering applications is discussed to demonstrate potential insights for novel 4D bioprinting applications. To address the current challenges with this technology, we will conclude with future perspectives involving the incorporation of biological scaffolds and self-assembling nanomaterials in bioprinted tissue constructs.

The bioengineering of perfusable endocrine tissue with anastomosable blood vessels

Organ transplantation is a definitive treatment for endocrine disorders, but donor shortages limit the use of this technique. The development of regenerative therapies would revolutionize the treatment of endocrine disorders. As is the case for harvested organs, the ideal bioengineered graft would comprise vascularized endocrine tissue, contain blood vessels that could be anastomosed to host vessels, have stable blood flow, and be suitable for transplantation into various sites. Here, we describe a transplantable endocrine tissue graft that was fabricated byex vivoperfusion of tricultured cell sheets (isletβ-cells, vascular endothelial cells (vECs), and mesenchymal stem cells (MSCs)) on a vascularized tissue flap ofin vivoorigin. The present study has three key findings. First, mild hypothermic conditions enhanced the success ofex vivoperfusion culture. Specifically, graft construction failed at 37 °C but succeeded at 32 °C (mild hypothermia), and endocrine tissue fabricated under mild hypothermia contained aggregations of isletβ-cells surrounded by dense vascular networks. Second, the construction of transplantable endocrine tissue byex vivoperfusion culture was better achieved using a vascular flap (VF) than a muscle flap. Third, the endocrine tissue construct generated using a VF could be transplanted into the rat by anastomosis of the graft artery and vein to host blood vessels, and the graft secreted insulin into the host's circulatory system for at least two weeks after transplantation. Endocrine tissues bioengineered using these techniques potentially could be used as novel endocrine therapies.

Efficacy of Autologous Skeletal Myoblast Cell Sheet Transplantation for Liver Regeneration in Liver Failure

BACKGROUND

No effective therapies have yet been established for liver regeneration in liver failure. Autologous skeletal myoblast cell sheet transplantation has been proven to improve cardiac function in patients with heart failure, and one of the mechanisms has been reported to be a paracrine effect by various growth factors associated with liver regeneration. Therefore, the present study focused on the effect of myoblast cells on liver regeneration in vitro and in vivo.

METHODS

We assessed the effect of myoblast cells on the cells comprising the liver in vitro in association with liver regeneration. In addition, we examined in vivo effect of skeletal myoblast cell sheet transplantation in C57/BL/6 mouse models of liver failure, such as liver fibrosis induced by thioacetamide and hepatectomy.

RESULTS

In vitro, the myoblast cells exhibited a capacity to promote the proliferation of hepatic epithelial cells and the angiogenesis of liver sinusoidal endothelial cells, and suppress the activation of hepatic stellate cells. In vivo, sheet transplantation significantly suppressed liver fibrosis in the induced liver fibrosis model and accelerated liver regeneration in the hepatectomy model.

CONCLUSIONS

Autologous skeletal myoblast cell sheet transplantation significantly improved the liver failure in the in vitro and in vivo models. Sheet transplantation is expected to have the potential to be a clinically therapeutic option for liver regeneration in liver failure.

Research Progress on the Osteogenesis-Related Regulatory Mechanisms of Human Umbilical Cord Mesenchymal Stem Cells

In recent years, research on human umbilical cord mesenchymal stem cells (hUCMSCs) derived from human umbilical cord tissue has accelerated and entered clinical application research. Compared with mesenchymal stem cells (MSCs) from other sources, hUCMSCs can be extracted from different parts of umbilical cord or from the whole umbilical cord. It has the characteristics of less ethical controversy, high differentiation potential, strong proliferation ability, efficient expansion in vitro, avoiding immune rejection and immune privilege, and avoids the limitations of lack of embryonic stem cells, heterogeneity, ethical and moral constraints. hUCMSCs avoid the need for embryonic stem cell sources, heterogeneity, and ethical and moral constraints. Bone defects are very common in clinical practice, but completely effective bone tissue regeneration treatment is challenging. Currently, autologous bone transplantation and allogeneic bone transplantation are main treatment approaches in clinical work, but each has different shortcomings, such as limited sources, invasiveness, immune rejection and insufficient osteogenic ability. Therefore, to solve the bottleneck of bone tissue regeneration and repair, a great amount of research has been carried out to explore the clinical advantages of hUCMSCs as seed cells to promote osteogenesis.However, the regulation of osteogenic differentiation of hUCMSCs is an extremely complex process. Although a large number of studies have demonstrated that the role of hUCMSCs in enhancing local bone regeneration and repair through osteogenic differentiation and transplantation into the body involves multiple signaling pathways, there is no relevant article that summarize the findings. This article discusses the osteogenesis-related regulatory mechanisms of hUCMSCs, summarizes the currently known related mechanisms, and speculates on the possible signals.

Periostin plays a key role in maintaining the osteogenic abilities of dental follicle stem cells in the inflammatory microenvironment

OBJECTIVE

This study aimed to explore the effect of periostin in the osteogenic abilities of dental follicle stem cells (DFSCs) and DFSC sheets in the inflammatory microenvironment.

DESIGN

DFSCs were isolated from dental follicles and identified. A lentiviral vector was used to knock down periostin in DFSCs. 250 ng/ml lipopolysaccharide from Porphyromonas gingivalis (P.g-LPS) was used to construct the inflammatory microenvironment. Osteogenic differentiation was evaluated by alizarin red staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot. The formation of extracellular matrix was assessed by qRT-PCR and immunofluorescence. The expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) were measured by western blot.

RESULTS

Knockdown of periostin inhibited osteogenic differentiation and promoted adipogenic differentiation of DFSCs. In an inflammatory microenvironment, knockdown of periostin attenuated the proliferation and osteogenic differentiation of DFSCs. Knockdown of periostin inhibited the formation of extracellular matrix collagen I (COL-I), fibronectin, and laminin in DFSC sheets, but did not affect the expression of osteogenesis-related markers alkaline phosphatase (ALP) and osteocalcin (OCN). In the inflammatory microenvironment, knocking down periostin inhibited the expression of OCN and OPG in DFSC sheets, and promoted the expression of RANKL.

CONCLUSION

Periostin played a key role in maintaining the osteogenic abilities of DFSCs and DFSC sheets in the inflammatory microenvironment and might be an important molecule in the process of DFSCs coping with inflammatory microenvironment and promoting periodontal tissues regeneration.

A novel chondrocyte sheet fabrication using human-induced pluripotent stem cell-derived expandable limb-bud mesenchymal cells

BACKGROUND

Cell sheet fabrication for articular cartilage regenerative medicine necessitates a large number of chondrocytes of consistent quality as a cell source. Previously, we have developed human-induced pluripotent stem cell (iPSC)-derived expandable PRRX1⁺ limb-bud mesenchymal cells (ExpLBM) with stable expansion and high chondrogenic capacity, while in this study; our ExpLBM technology was combined with cell sheet engineering to assess its potential as a stable cell source for articular cartilage regeneration.

METHODS

ExpLBM cells derived from human-induced pluripotent stem cells (hiPSCs), including 414C2 and Ff-KVs09 (HLA homozygous), were seeded onto a culture plate and two-dimensional chondrogenic induction (2-DCI) was initiated. After 2-DCI, ExpLBM-derived chondrocytes were stripped and transferred to temperature-responsive culture inserts and the chondrocyte sheets were histologically examined or transplanted into osteochondral knee defects of immunodeficient rats.

RESULTS

Immunohistochemistry revealed that ExpLBM-derived cell sheets were positive for Safranin O, COL2, and ACAN but that they were negative for COL1 and RUNX2. Furthermore, the engrafted tissues in osteochondral knee defects in immunodeficient rats were stained with SafO, human VIMENTIN, ACAN, and COL2.

CONCLUSIONS

The present study is the first to report the chondrocyte sheet fabrication with hiPSC-derived cell source. hiPSC-derived ExpLBM would be a promising cell source for cell sheet technology in articular cartilage regenerative medicine.

Fibrinogen-based cell and spheroid sheets manipulating and delivery for mouse hindlimb ischemia

In this research, we introduced a novel strategy for fabricating cell sheets (CSs) prepared by simply adding a fibrinogen solution to growth medium without using any synthetic polymers or chemical agents. We confirmed that the fibrinogen-based CS could be modified for target tissue regardless of size, shape, and cell types. Also, fibrinogen-based CSs were versatile and could be used to form three-dimensional (3D) CSs such as multi-layered CSs and those mimicking native blood vessels. We also prepared fibrinogen-based spheroid sheets for the treatment of ischemic disease. The fibrinogen-based spheroid sheets had much higherin vitrotubule formation and released more angiogenic factors compared to other types of platform in this research. We transplanted fibrinogen-based spheroid sheets into a mouse hindlimb ischemia model and found that fibrinogen-based spheroid sheets showed significantly improved physiological function and blood perfusion rates compared to the other types of platform in this research.

Tricultured Cell Sheets Develop into Functional Pancreatic Islet Tissue with a Vascular Network

Methods to induce islet β-cells from induced pluripotent stem cells or embryonic stem cells have been established. However, islet β-cells are susceptible to apoptosis under hypoxic conditions, so the technique used to transplant β-cells must maintain the viability of cells in vivo. This study describes the development of a tricultured cell sheet, which was made by coculturing islet β-cells, vascular endothelial cells, and mesenchymal stem cells for 1 day. The islet β-cells in the tricultured cell sheet self-organized into islet-like structures surrounded by a dense vascular network in vitro. Triple-layered tricultured cell sheets engrafted well after transplantation in vivo and developed into insulin-secreting tissue with abundant blood vessels and a high density of islet β-cells. We anticipate that the tricultured cell sheet could be used as an in vitro pseudo-islet model for pharmaceutical testing and may have potential for development into transplantable grafts for use in regenerative medicine.

Transplantation of hybrid adipose-derived stem cell sheet with autologous peritoneum: An in vivo feasibility study

Introduction

In regenerative medicine, cell sheet engineering has various advantages, including the retention of cells at the transplantation site for a longer period and the local delivery of growth factors and cytokines. Adipose-derived stem cell (ASC) is widely used owing to their various functions such as wound healing, immunomodulation, and nerve regeneration, in addition to their ability to differentiate into adipocytes, chondrocytes, and osteoblasts. ASC sheet generated using cell sheet engineering is considered effective in preventing anastomotic leakage, a serious postoperative complication in gastrointestinal surgery. However, the ASC sheet is too soft, thin, and brittle to handle with laparoscopic forceps during the operation. Therefore, we considered using the peritoneum, which is stiff and easy to collect while operating, as an alternative support. In this study, we explored the feasibility of using the peritoneum as a support for the precise transplantation of ASC sheets during surgery.

Methods

ASCs were isolated from the subcutaneous fat of the inguinal region of Sprague-Dawley (SD) transgenic rats expressing green fluorescent protein. ASCs were cultured until passage 3, seeded in temperature-responsive culture dishes, and the resulting ASC sheet was harvested at more than 80% confluency. Non-transgenic SD rats were used for transplant experiments. The wall peritoneum was harvested from SD rats following laparotomy, and hybrid adipose-derived stem cell (HASC) sheet was prepared by laminating the peritoneum with ASC sheet. The cell sheets were transplanted on the backs of SD rats following the incision. On post-transplantation days 3 and 7, the specimens were extracted. ASC and HASC sheets were then compared macroscopically and histopathologically.

Results

HASC sheet transplantation was macroscopically and histopathologically more effective than ASC sheet transplantation. The peritoneum provided sufficient stiffness as a support for precise transplantation.

Conclusion

The newly developed HASC sheet, which combine the advantages of ASC sheet with those of the peritoneum, could be more useful for clinical application than the ASC sheet alone.

Potential of Mesenchymal Stem Cell Sheets on Periodontal Regeneration: A Systematic Review of Pre-Clinical Studies

BACKGROUND

Cell sheet technique using mesenchymal stem cells is a high-level strategy in periodontal regenerative medicine. Although recent studies have shown the role of MSCSs in increased dental supporting tissues and bone, there is no systematic review focused specifically on assessing periodontal regeneration in orthotopic animal models.

OBJECTIVE

To evaluate the potential of mesenchymal stem cell sheets (MSCSs) on periodontal regeneration, compared to control, in experimental animal models Methods: Pre-clinical studies in periodontal defects of animal models were considered eligible. The electronic search included the MEDLINE, Web of Science, EMBASE and LILACS databases. The review was conducted according to the Preferred Reporting Item for Systematic Reviews and Meta-Analyses statement guidelines.

RESULTS

A total of 17 of the 3989 studies obtained from the electronic database search were included. MSCSs included dental follicle (DF) MSCSs, periodontal ligament (PL) MSCSs, dental pulp (DP) MSCSs, bone marrow (BM) MSCSs, alveolar periosteal (AP) MSCSs and gingival (G) MSCSs. Regarding cell sheet inducing protocol, most of the studies used ascorbic acid (52.94%). Others used culture dishes grafted with a temperature-responsive polymer (47.06%). Adverse effects were not identified in the majority of studies. Meta-analysis was not considered because of methodological heterogeneities. PDL-MSCSs were superior for periodontal regeneration enhancement compared to the control, but in an induced inflammatory microenvironment, DF-MSCSs were better. Moreover, DF-MSCSs, DP-MSCSs, and BM-MSCSs showed improved results compared to the control.

CONCLUSION

MSCSs can improve periodontal regeneration in animal periodontal defect models.

In vitro vascularization of hydrogel-based tissue constructs via a combined approach of cell sheet engineering and dynamic perfusion cell culture

The bioengineering of artificial tissue constructs requires special attention to their fast vascularization to provide cells with sufficient nutrients and oxygen. We addressed the challenge of in vitro vascularization by employing a combined approach of cell sheet engineering, 3D printing, and cellular self-organization in dynamic maturation culture. A confluent cell sheet of human umbilical vein endothelial cells (HUVECs) was detached from a thermoresponsive cell culture substrate and transferred onto a 3D-printed, perfusable tubular scaffold using a custom-made cell sheet rolling device. Under indirect co-culture conditions with human dermal fibroblasts (HDFs), the cell sheet-covered vessel mimic embedded in a collagen gel together with additional singularized HUVECs started sprouting into the surrounding gel, while the suspended cells around the tube self-organized and formed a dense lumen-containing 3D vascular network throughout the gel. The HDFs cultured below the HUVEC-containing cell culture insert provided angiogenic support to the HUVECs via molecular crosstalk without competing for space with the HUVECs or inducing rapid collagen matrix remodeling. The resulting vascular network remained viable under these conditions throughout the 3 week cell culture period. This static indirect co-culture setup was further transferred to dynamic flow conditions, where the medium perfusion was enabled via two independently addressable perfusion circuits equipped with two different cell culture chambers, one hosting the HDFs and the other hosting the HUVEC-laden collagen gel. Using this system, we successfully connected the collagen-embedded HUVEC culture to a dynamic medium flow, and within 1 week of the dynamic cell culture, we detected angiogenic sprouting and dense microvascular network formation via HUVEC self-organization in the hydrogel. Our approach of combining a 3D-printed and cell sheet-covered vascular precursor that retained its sprouting capacity together with the self-assembling HUVECs in a dynamic perfusion culture resulted in a vascular-like 3D network, which is a critical step toward the long-term vascularization of bioengineered in vitro tissue constructs.

Transfer-Tattoo-Like Cell-Sheet Delivery Induced by Interfacial Cell Migration

A direct transfer of a cell sheet from a culture surface to a target tissue is introduced. Commercially available, flexible parylene is used as the culture surface, and it is proposed that the UV-treated parylene offers adequate and intermediate levels of cell adhesiveness for both the stable cell attachment during culture and for the efficient cell transfer to a target surface. The versatility of this cell-transfer process is demonstrated with various cell types, including MRC-5, HDFn, HULEC-5a, MC3T3-E1, A549, C2C12 cells, and MDCK-II cells. The novel cell-sheet engineering is based on a mechanism of interfacial cell migration between two surfaces with different adhesion preferences. Monitoring of cytoskeletal dynamics and drug treatments during the cell-transfer process reveals that the interfacial cell migration occurs by utilizing the existing transmembrane proteins on the cell surface to bind to the targeted surface. The re-establishment and reversal of cell polarity after the transfer process are also identified. Its unique capabilities of 3D multilayer stacking, freeform design, and curved surface application are demonstrated. Finally, the therapeutic potential of the cell-sheet delivery system is demonstrated by applying it to cutaneous wound healing and skin-tissue regeneration in mice models.

Polydactyly-derived allogeneic chondrocyte cell-sheet transplantation with high tibial osteotomy as regenerative therapy for knee osteoarthritis

Allogeneic cell therapies are not fully effective in treating osteoarthritis of the knee (OAK). We recently reported that transplantation of autologous chondrocyte cell-sheets along with open-wedge high tibial osteotomy promoted hyaline cartilage repair in humans. Here we describe our regenerative therapy for OAK using polydactyly-derived allogeneic chondrocyte cell-sheets (PD sheets) and temperature-responsive culture inserts. Ten patients with OAK and cartilage defects categorized arthroscopically as Outerbridge grade III or IV received the therapy. Cartilage viscoelasticity and thickness were assessed before and after transplantation. Arthroscopic biopsies obtained 12 months after transplantation were analyzed histologically. Gene expression was analyzed to evaluate the PD sheets. In this small initial longitudinal series, PD sheet transplantation was effective in treating OAK, as indicated by changes in cartilage properties. Gene marker sets in PD sheets may predict outcomes after therapy and provide markers for the selection of donor cells. This combined surgery may be an ideal regenerative therapy with disease-modifying effects in OAK patients.

Organoids and Their Research Progress in Plastic and Reconstructive Surgery

Organoids are 3D structures generated from stem cells. Their functions and physiological characteristics are similar to those of normal organs. They are used in disease mechanism research, new drug development, organ transplantation and other fields. In recent years, the application of 3D materials in plastic surgery for repairing injuries, filling, tissue reconstruction and regeneration has also been investigated. The PubMed/MEDLINE database was queried to search for animal and human studies published through July of 2022 with search terms related to Organoids, Plastic Surgery, Pluripotent Stem Cells, Bioscaffold, Skin Reconstruction, Bone and Cartilage Regeneration. This review presents stem cells, scaffold materials and methods for the construction of organoids for plastic surgery, and it summarizes their research progress in plastic surgery in recent years.Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Challenges of Periodontal Tissue Engineering: Increasing Biomimicry through 3D Printing and Controlled Dynamic Environment

In recent years, tissue engineering studies have proposed several approaches to regenerate periodontium based on the use of three-dimensional (3D) tissue scaffolds alone or in association with periodontal ligament stem cells (PDLSCs). The rapid evolution of bioprinting has sped up classic regenerative medicine, making the fabrication of multilayered scaffolds-which are essential in targeting the periodontal ligament (PDL)-conceivable. Physiological mechanical loading is fundamental to generate this complex anatomical structure ex vivo. Indeed, loading induces the correct orientation of the fibers forming the PDL and maintains tissue homeostasis, whereas overloading or a failure to adapt to mechanical load can be at least in part responsible for a wrong tissue regeneration using PDLSCs. This review provides a brief overview of the most recent achievements in periodontal tissue engineering, with a particular focus on the use of PDLSCs, which are the best choice for regenerating PDL as well as alveolar bone and cementum. Different scaffolds associated with various manufacturing methods and data derived from the application of different mechanical loading protocols have been analyzed, demonstrating that periodontal tissue engineering represents a proof of concept with high potential for innovative therapies in the near future.

Synthesis of Thermoresponsive PNIPAM-Grafted Cellulose Sulfates for Bioactive Multilayers via Layer-by-Layer Technique

The robust thermoresponsive and bioactive surfaces for tissue engineering by combining poly-N-isopropylacrylamide (PNIPAM) and cellulose sulfate (CS) remain highly in demand but not yet realized. Herein, PNIPAM-grafted cellulose sulfates (PCSs) with diverse degrees of substitution ascribed to sulfate groups (DS_S) are synthesized for the first time. Higher sulfated PCS2 generally forms larger aggregates than lower sulfated PCS1 at their cloud point temperatures (TCP) of around 33 °C, whereas PCS1 leads to larger aggregates at body temperature (37 °C). Via the layer-by-layer (LbL) technique, biocompatible polyelectrolyte multilayers (PEMs) composed of PCSs as polyanions in combination with poly-l-lysine (PLL) or quaternized chitosan (QCHI) as polycations were fabricated. The resulting surfaces contained a more intermingled structure of polyanions with both polycations, while higher sulfated cellulose derivatives (CS2 and PCS2) displayed greater stability. Studies on toxicity and biocompatibility of PEM using 3T3 mouse fibroblasts showed a lower cytotoxicity of PEM with PCS2 and CS2 than PCS1 and CS1. Furthermore, the PEM using PCS2 particularly in combination with QCHI demonstrated excellent biocompatibility that is promising for new bioactive, thermoresponsive coatings on biomaterials and substrata for culturing adhesion-dependent cells.

Angiogenic stem cell delivery platform to augment post-infarction neovasculature and reverse ventricular remodeling

Many cell-based therapies are challenged by the poor localization of introduced cells and the use of biomaterial scaffolds with questionable biocompatibility or bio-functionality. Endothelial progenitor cells (EPCs), a popular cell type used in cell-based therapies due to their robust angiogenic potential, are limited in their therapeutic capacity to develop into mature vasculature. Here, we demonstrate a joint delivery of human-derived endothelial progenitor cells (EPC) and smooth muscle cells (SMC) as a scaffold-free, bi-level cell sheet platform to improve ventricular remodeling and function in an athymic rat model of myocardial infarction. The transplanted bi-level cell sheet on the ischemic heart provides a biomimetic microenvironment and improved cell-cell communication, enhancing cell engraftment and angiogenesis, thereby improving ventricular remodeling. Notably, the increased density of vessel-like structures and upregulation of biological adhesion and vasculature developmental genes, such as Cxcl12 and Notch3, particularly in the ischemic border zone myocardium, were observed following cell sheet transplantation. We provide compelling evidence that this SMC-EPC bi-level cell sheet construct can be a promising therapy to repair ischemic cardiomyopathy.

Supramolecular Surface Coatings with Acetylated Polyrotaxane-Based Triblock Copolymers for Thermal Regulation of Cell Adhesion and Fabrication of Cell Sheets

Polyrotaxanes (PRXs) containing acetylated α-cyclodextrins exhibit a temperature-dependent phase transition in aqueous solutions across their lower critical solution temperature (LCST) of approximately 26.6 °C. To gain insights into the interactions of acetylated PRXs (Ac-PRXs) with biological components, thermoresponsive supramolecular surfaces were prepared by coating tissue culture polystyrene (TCPS) surfaces with Ac-PRX triblock copolymers, and their surface properties across the LCST were evaluated. The wettability and protein adsorption of Ac-PRX-coated surfaces changed significantly between 10 and 37 °C, whereas the uncoated TCPS and unmodified PRX-coated surfaces did not alter the wettability and protein adsorption at 10 and 37 °C. The adhesion, proliferation, morphology, and adhesion strength of NIH/3T3 cells on Ac-PRX-coated surfaces were found to be similar to those of the uncoated and unmodified PRX-coated surfaces. However, the adhesion strength of NIH/3T3 cells on Ac-PRX-coated surfaces decreased drastically at 10 °C. Consequently, the cells spontaneously detached from the Ac-PRX-coated surfaces without enzymatic treatment. Additionally, when incubating confluent cells at 10 °C, the cells detached from Ac-PRX-coated surfaces as cell sheets while retaining extracellular matrix proteins. The findings of this study provide new directions for the design of thermoresponsive supramolecular biointerfaces for applications in bioseparation and cell manipulation.

Mesenchymal Stem Cell Sheet Centrifuge-Assisted Layering Augments Pro-Regenerative Cytokine Production

A focal advantage of cell sheet technology has been as a scaffold-free three-dimensional (3D) cell delivery platform capable of sustained cell engraftment, survival, and reparative function. Recent evidence demonstrates that the intrinsic cell sheet 3D tissue-like microenvironment stimulates mesenchymal stem cell (MSC) paracrine factor production. In this capacity, cell sheets not only function as 3D cell delivery platforms, but also prime MSC therapeutic paracrine capacity. This study introduces a “cell sheet multilayering by centrifugation” strategy to non-invasively augment MSC paracrine factor production. Cell sheets fabricated by temperature-mediated harvest were first centrifuged as single layers using optimized conditions of rotational speed and time. Centrifugation enhanced cell physical and biochemical interactions related to intercellular communication and matrix interactions within the single cell sheet, upregulating MSC gene expression of connexin 43, integrin β1, and laminin α5. Single cell sheet centrifugation triggered MSC functional enhancement, secreting higher concentrations of pro-regenerative cytokines vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and interleukin-10 (IL-10). Subsequent cell sheet stacking, and centrifugation generated cohesive, bilayer MSC sheets within 2 h, which could not be accomplished within 24 h by conventional layering methods. Conventional layering led to H1F-1α upregulation and increased cell death, indicating a hypoxic thickness limitation to this approach. Comparing centrifuged single and bilayer cell sheets revealed that layering increased VEGF production 10-fold, attributed to intercellular interactions at the layered sheet interface. The “MSC sheet multilayering by centrifugation” strategy described herein generates a 3D MSC-delivery platform with boosted therapeutic factor production capacity.

Application of vancomycin-impregnated calcium sulfate hemihydrate/nanohydroxyapatite/carboxymethyl chitosan injectable hydrogels combined with BMSC sheets for the treatment of infected bone defects in a rabbit model

BACKGROUND

The choice of bone substitutes for the treatment of infected bone defects (IBDs) has attracted the attention of surgeons for years. However, single-stage bioabsorbable materials that are used as carriers for antibiotic release, as well as scaffolds for BMSC sheets, need further exploration. Our study was designed to investigate the effect of vancomycin-loaded calcium sulfate hemihydrate/nanohydroxyapatite/carboxymethyl chitosan (CSH/n-HA/CMCS) hydrogels combined with BMSC sheets as bone substitutes for the treatment of IBDs.

METHODS

BMSCs were harvested and cultured into cell sheets. After the successful establishment of an animal model with chronic osteomyelitis, 48 New Zealand white rabbits were randomly divided into 4 groups. Animals in Group A were treated with thorough debridement as a control. Group B was treated with BMSC sheets. CSH/n-HA/CMCS hydrogels were implanted in the treatment of Group C, and Group D was treated with CSH/n-HA/CMCS+BMSC sheets. Gross observation and micro-CT 3D reconstruction were performed to assess the osteogenic and infection elimination abilities of the treatment materials. Histological staining (haematoxylin and eosin and Van Gieson) was used to observe inflammatory cell infiltration and the formation of collagen fibres at 4, 8, and 12 weeks after implantation.

RESULTS

The bone defects of the control group were not repaired at 12 weeks, as chronic osteomyelitis was still observed. HE staining showed a large amount of inflammatory cell infiltration around the tissue, and VG staining showed no new collagen fibres formation. In the BMSC sheet group, although new bone formation was observed by gross observation and micro-CT scanning, infection was not effectively controlled due to unfilled cavities. Some neutrophils and only a small amount of collagen fibres could be observed. Both the hydrogel and hydrogel/BMSCs groups achieved satisfactory repair effects and infection control. Micro-CT 3D reconstruction at 4 weeks showed that the hydrogel/BMSC sheet group had higher reconstruction efficiency and better bone modelling with normal morphology. HE staining showed little aggregation of inflammatory cells, and VG staining showed a large number of new collagen fibres.

CONCLUSIONS

Our preliminary results suggested that compared to a single material, the novel antibiotic-impregnated hydrogels acted as superior scaffolds for BMSC sheets and excellent antibiotic vectors against infection, which provided a basis for applying tissue engineering technology to the treatment of chronic osteomyelitis.

Effect of polystyrene nanoplastics and their degraded forms on stem cell fate

Several studies have examined the effects of micro- and nanoplastics on microbes, cells, and the environment. However, only a few studies have examined their effects-especially, those of their reduced cohesiveness-on cell viability and physiology. We synthesized surfactant-free amine-functionalized polystyrene (PS) nanoparticles (NPs) and PS-NPs with decreased crosslinking density (DPS-NPs) without changing other factors, such as size, shape, and zeta potential and examined their effects on cell viability and physiology. PS- and DPS-NPs exhibited reactive oxygen species (ROS) scavenging activity by upregulating GPX3 expression and downregulating HSP70 (ROS-related gene) and XBP1 (endoplasmic reticulum stress-related gene) expression in human bone marrow-derived mesenchymal stem cells (hBM-MSCs). Additionally, they led to upregulation of MFN2 (mitochondrial fusion related gene) expression and downregulation of FIS1 (mitochondrial fission related gene) expression, indicating enhanced mitochondrial fusion in hBM-MSCs. Cell-cycle analysis revealed that PS- and DPS-NPs increased the proportion of cells in the S phase, indicating that they promoted cell proliferation and, specifically, the adipogenic differentiation of hBM-MSCs. However, the cytotoxicity of DPS-NPs against hBM-MSCs was higher than that of PS-NPs after long-term treatment under adipogenic conditions.

Mesenchymal Stem Cell Sheets for Engineering of the Tendon-Bone Interface

Failure to regenerate the gradient tendon-bone interface of the enthesis results in poor clinical outcomes for surgical repair. The goal of this study was to evaluate the potential of composite cell sheets for engineering of the tendon-bone interface to improve regeneration of the functionally graded tissue. We hypothesize that stacking cell sheets at early stages of differentiation into tenogenic and osteogenic progenitors will create a composite structure with integrated layers. Cell sheets were fabricated on methyl cellulose and poly(N-isopropylacrylamide) thermally reversible polymers with human adipose-derived stem cells and differentiated into progenitors of tendon and bone with chemical induction media. Tenogenic and osteogenic cell sheets were stacked, and the engineered tendon-bone interface (TM-OM) was characterized in vitro in comparison to stacked cell sheet controls cultured in basal growth medium (GM-GM), osteogenic medium (OM-OM), and tenogenic medium (TM-TM). Samples were characterized by histology, quantitative real-time polymerase chain reaction, and immunofluorescent staining for markers of tendon, fibrocartilage, and bone including mineralization, scleraxis, tenomodulin, COL2, COLX, RUNX2, osteonectin, and osterix. After 1 week co-culture in basal growth medium, TM-OM cell sheets formed a tissue construct with integrated layers expressing markers of tendon, mineralized fibrocartilage, and bone with a spatial gradient in RUNX2 expression. Tenogenic cell sheets had increased expression of scleraxis and tenomodulin. Osteogenic cell sheets exhibited mineralization 1 week after stacking and upregulation of osterix and osteonectin. Additionally, in the engineered interface, there was significantly increased gene expression of IHH and COLX, indicative of endochondral ossification. These results highlight the potential for composite cell sheets fabricated with adipose-derived stem cells for engineering of the tendon-bone interface. Impact statement This study presents a method for fabrication of the tendon-bone interface using stacked cell sheets of tenogenic and osteogenic progenitors differentiated from human adipose-derived mesenchymal stem cells, resulting in a composite structure expressing markers of tendon, mineralized fibrocartilage, and bone. This work is an important step toward regeneration of the biological gradient of the enthesis and demonstrates the potential for engineering complex tissue interfaces from a single autologous cell source to facilitate clinical translation.

Adhesion, proliferation and detachment of various cell types on thermoresponsive microgel coatings

Cutting-edge biomedical applications require increasingly complex and fastidious cell systems, for example, various classes of primary or stem cells. Their cultivation, however, still differs little from 30 years ago. This especially applies to the use of indiscriminative proteases for non-specific cell detachment. A far more gentle alternative changes the adhesive properties of the cell culture substrates through coatings based on thermoresponsive polymers. Such polymers mediate cell adhesion at 3 7 ∘ C, but become repulsive upon a cell-compatible temperature drop to e.g. 3 2 ∘ C. While the high functionality of this method has already been well proven, it must also be easy and reproducible to apply. Here, we emphasize the potential of standard cell culture materials coated by spraying with thermoresponsive microgels for routine cultivation and beyond. On these surfaces, we successfully cultivated and detached various cell types, including induced pluripotent stem cells (iPS-cells) and cells in serum-free culture on. In addition, we evaluated the compatibility of the microgel-sprayed surfaces with adhesion-promoting proteins, which are essential for e.g. stem cells or neuronal cells. Finally, we demonstrate that the microgel surfaces do not impair proliferation and show their long-term stability. We conclude that for cell detachment, thermoresponsive cell culture substrates can fully substitute proteases, like trypsin, by employing a comparably straightforward protocol that is compatible with many industrial processing lines. This article is protected by copyright. All rights reserved.

Strategies to Induce Blood Vessel Ingrowth into Skin Grafts and Tissue-Engineered Substitutes

Skin is a multilayer organ consisting of several tissues and appendages residing in a complex niche. Adequate and physiologically regulated vascularization is an absolute requirement for skin homeostasis, regeneration, and wound healing. The lack of vascular networks and ischemia results in delayed wound closure. In addition, vascularization is critical for the prolonged function and survival of skin grafts and tissue-engineered skin substitutes. This study highlights the clinical challenges associated with the limited vascularization in the cutaneous wounds. Then, we highlight the novel approaches for the development of vascular networks in the skin autografts, allografts, and artificial substitutes. Also, the future directions to overcome the existing vascularization complications in skin grafting and synthetic skin substitutes are presented. Statement of Significance Delayed closure of large dermal wounds, such as burn injuries, results from the lack of vascular networks and ischemia. The amount of blood supply in the skin graft is the primary factor determining the quality of the transplanted grafts. The current skin grafts and their fabrication methods lack the appropriate features that contribute to the vascularization and integration of the wound bed and graft and adherence to the skin layers. Therefore, the new generation of skin grafts should consider advanced technologies to induce vascularization and overcome current challenges.

Dental-derived mesenchymal stem cell sheets: a prospective tissue engineering for regenerative medicine

Stem cells transplantation is the main method of tissue engineering regeneration treatment, the viability and therapeutic efficiency are limited. Scaffold materials also play an important role in tissue engineering, whereas there are still many limitations, such as rejection and toxic side effects caused by scaffold materials. Cell sheet engineering is a scaffold-free tissue technology, which avoids the side effects of traditional scaffolds and maximizes the function of stem cells. It is increasingly being used in the field of tissue regenerative medicine. Dental-derived mesenchymal stem cells (DMSCs) are multipotent cells that exist in various dental tissues and can be used in stem cell-based therapy, which is impactful in regenerative medicine. Emerging evidences show that cell sheets derived from DMSCs have better effects in the field of regenerative medicine applications. Extracellular matrix (ECM) is the main component of cell sheets, which is a dynamic repository of signalling biological molecules and has a variety of biological functions and may play an important role in the application of cell sheets. In this review, we summarized the application status, mechanisms that sheets and ECM may play and future prospect of DMSC sheets on regeneration medicine.

Cell-Based Microfluidic Device Utilizing Cell Sheet Technology

The development of microelectromechanical systems has resulted in the rapid development of polydimethylpolysiloxane (PDMS) microfluidic devices for drug screening models. Various cell functions, such as the response of endothelial cells to fluids, have been elucidated using microfluidic devices. Additionally, organ-on-a-chip systems that include organs that are important for biological circulation, such as the heart, liver, pancreas, kidneys, and brain, have been developed. These organs realize the biological circulation system in a manner that cannot be reproduced by artificial organs; however, the flow channels between the organs are often artificially created by PDMS. In this study, we developed a microfluidic device consisting only of cells, by combining cell sheet technology with microtitanium wires. Microwires were placed between stacked fibroblast cell sheets, and the cell sheets adhered to each other, after which the microwires were removed leaving a luminal structure with a size approximately equal to the arteriolar size. The lumen structure was constructed using wires with diameters of 50, 100, 150, and 200 μm, which were approximations of the arteriole diameters. Furthermore, using a perfusion device, we successfully perfused the luminal structure created inside the cell sheets. The results revealed that a culture solution can be supplied to a cell sheet with a very high cell density. The biofabrication technology proposed in this study can contribute to the development of organ-on-a-chip systems.

Stem cell therapy applied for digestive anastomosis: Current state and future perspectives

BACKGROUND

Digestive tract resections are usually followed by an anastomosis. Anastomotic leakage, normally due to failed healing, is the most feared complication in digestive surgery because it is associated with high morbidity and mortality. Despite technical and technological advances and focused research, its rates have remained almost unchanged the last decades. In the last two decades, stem cells (SCs) have been shown to enhance healing in animal and human studies; hence, SCs have emerged since 2008 as an alternative to improve anastomoses outcomes.

AIM

To summarise the published knowledge of SC utilisation as a preventative tool for hollow digestive viscera anastomotic or suture leaks.

METHODS

PubMed, Science Direct, Scopus and Cochrane searches were performed using the key words “anastomosis”, “colorectal/colonic anastomoses”, “anastomotic leak”, “stem cells”, “progenitor cells”, “cellular therapy” and “cell therapy” in order to identify relevant articles published in English and Spanish during the years of 2000 to 2021. Studies employing SCs, performing digestive anastomoses in hollow viscera or digestive perforation sutures and monitoring healing were finally included. Reference lists from the selected articles were reviewed to identify additional pertinent articles.

Given the great variability in the study designs, anastomotic models, interventions (SCs, doses and vehicles) and outcome measures, performing a reliable meta-analysis was considered impossible, so we present the studies, their results and limitations.

RESULTS

Eighteen preclinical studies and three review papers were identified; no clinical studies have been published and there are no registered clinical trials. Experimental studies, mainly in rat and porcine models and occasionally in very adverse conditions such as ischaemia or colitis, have been demonstrated SCs as safe and have shown some encouraging morphological, functional and even clinical results. Mesenchymal SCs are mostly employed, and delivery routes are mainly local injections and cell sheets followed by biosutures (sutures coated by SCs) or purely topical. As potential weaknesses, animal models need to be improved to make them more comparable and equivalent to clinical practice, and the SC isolation processes need to be standardised. There is notable heterogeneity in the studies, making them difficult to compare. Further investigations are needed to establish the indications, the administration system, potential adjuvants, the final efficacy and to confirm safety and exclude definitively oncological concerns.

CONCLUSION

The future role of SC therapy to induce healing processes in digestive anastomoses/sutures still needs to be determined and seems to be currently far from clinical use.

Microfluidic Surgery in Single Cells and Multicellular Systems

Microscale surgery on single cells and small organisms has enabled major advances in fundamental biology and in engineering biological systems. Examples of applications range from wound healing and regeneration studies to the generation of hybridoma to produce monoclonal antibodies. Even today, these surgical operations are often performed manually, but they are labor intensive and lack reproducibility. Microfluidics has emerged as a powerful technology to control and manipulate cells and multicellular systems at the micro- and nanoscale with high precision. Here, we review the physical and chemical mechanisms of microscale surgery and the corresponding design principles, applications, and implementations in microfluidic systems. We consider four types of surgical operations: (1) sectioning, which splits a biological entity into multiple parts, (2) ablation, which destroys part of an entity, (3) biopsy, which extracts materials from within a living cell, and (4) fusion, which joins multiple entities into one. For each type of surgery, we summarize the motivating applications and the microfluidic devices developed. Throughout this review, we highlight existing challenges and opportunities. We hope that this review will inspire scientists and engineers to continue to explore and improve microfluidic surgical methods.

Tubular Cardiac Tissue Bioengineered from Multi-Layered Cell Sheets for Use in the Treatment of Heart Failure

This chapter describes a method for creating tubular cardiac tissue in vitro. Thick cardiac tissue in a tubular configuration is prepared by stacking cell sheets stepwise on the inner wall of a segment of small intestine, which functions as a blood vessel bed. The capillaries of the small intestinal segment are fed by an artery and drained by a vein. Therefore, perfusion culture of the cardiac tissue is achieved by continuously infusing culture medium into the arterial vessel that supplies the segment of small intestine. The aim of this technique is to fabricate tubular cardiac tissue that can function as a pump by sequentially implanting and culturing cardiac cell sheets on the inner wall of a perfused segment of small intestine.

Development of alternative gene transfer techniques for ex vivo and in vivo gene therapy in a canine model

INTRODUCTION

Gene therapy have recently attracted much attention as a curative therapeutic option for inherited single gene disorders such as hemophilia. Hemophilia is a hereditary bleeding disorder caused by the deficiency of clotting activity of factor VIII (FVIII) or factor IX (FIX), and gene therapy for hemophilia using viral vector have been vigorously investigated worldwide. Toward further advancement of gene therapy for hemophilia, we have previously developed and validated the efficacy of novel two types of gene transfer technologies using a mouse model of hemophilia A. Here we investigated the efficacy and safety of the technologies in canine model. Especially, validations of technical procedures of the gene transfers for dogs were focused.

METHODS

Green fluorescence protein (GFP) gene were transduced into normal beagle dogs by ex vivo and in vivo gene transfer techniques. For ex vivo gene transfer, blood outgrowth endothelial cells (BOECs) derived from peripheral blood of normal dogs were transduced with GFP gene using lentivirus vector, propagated, fabricated as cell sheets, then implanted onto the omentum of the same dogs. For in vivo gene transfer, normal dogs were subjected to GFP gene transduction with non-viral piggyBac vector by liver-targeted hydrodynamic injections.

RESULTS

No major adverse events were observed during the gene transfers in both gene transfer systems. As for ex vivo gene transfer, histological findings from the omental biopsy performed 4 weeks after implantation revealed the tube formation by implanted GFP-positive BOECs in the sub-adipose tissue layer without any inflammatory findings, and the detected GFP signals were maintained over 6 months. Regarding in vivo gene transfer, analyses of liver biopsy samples revealed more than 90% of liver cells were positive for GFP signals in the injected liver lobes 1 week after gene transfers, then the signals gradually declined overtime.

CONCLUSIONS

Two types of gene transfer techniques were successfully applied to a canine model, and the transduced gene expressions persisted for a long term. Toward clinical application for hemophilia patients, practical assessments of therapeutic efficacy of these techniques will need to be performed using a dog model of hemophilia and FVIII (or FIX) gene.

Cell sheet transplantation prevents inflammatory adhesions: A new treatment for adhesive otitis media

Introduction

We developed a new treatment method that combines tympanoplasty with transplantation of autologous cultured nasal mucosal epithelial cell sheets to regenerate the mucosa of patients with adhesive otitis media, which has been difficult to treat effectively. We verified whether this procedure could be performed safely and measured its therapeutic efficacy.

Methods

Autologous nasal mucosal epithelial cell sheets were manufactured at a good manufacturing practice-compliant cell processing facility using autologous nasal mucosal tissue. We performed tympanoplasty and transplanted the cell sheets into the middle ear cavity in six patients with adhesive otitis media.

Results

The manufactured autologous cultured epithelial cell sheets met the predetermined quality standards and were successfully transplanted safely in all cases. Computed tomography findings after cell sheet transplantation showed that aeration in the tympanic cavity was maintained or restored in five of the six patients (83.3%). Four of the six (66.7%) patients had postoperative air-bone gap within 20 dB, which is considered a postoperative success in tympanoplasty for chronic middle ear disease.

Conclusions

The results of this clinical study suggest that tympanoplasty with cell sheet transplantation can be used to treat adhesive otitis media by reliably preventing re-adhesion of the tympanic membrane.

Transplantation of Human Pluripotent Stem Cell-Derived Cardiomyocytes for Cardiac Regenerative Therapy

Cardiovascular disease is the leading cause of death worldwide and bears an immense economic burden. Late-stage heart failure often requires total heart transplantation; however, due to donor shortages and lifelong immunosuppression, alternative cardiac regenerative therapies are in high demand. Human pluripotent stem cells (hPSCs), including human embryonic and induced pluripotent stem cells, have emerged as a viable source of human cardiomyocytes for transplantation. Recent developments in several mammalian models of cardiac injury have provided strong evidence of the therapeutic potential of hPSC-derived cardiomyocytes (hPSC-CM), showing their ability to electromechanically integrate with host cardiac tissue and promote functional recovery. In this review, we will discuss recent developments in hPSC-CM differentiation and transplantation strategies for delivery to the heart. We will highlight the mechanisms through which hPSC-CMs contribute to heart repair, review major challenges in successful transplantation of hPSC-CMs, and present solutions that are being explored to address these limitations. We end with a discussion of the clinical use of hPSC-CMs, including hurdles to clinical translation, current clinical trials, and future perspectives on hPSC-CM transplantation.

Modulation of hydrogel stiffness by external stimuli: soft materials for mechanotransduction studies

Mechanotransduction is an important process in determining cell survival, proliferation, migration and differentiation. The extracellular matrix (ECM) is the component of natural tissue that provides structural support and biochemical signals to adhering cells. The ECM is dynamic and undergoes physical and biochemical changes in response to various stimuli and there is an interest in understanding the effect of dynamic changes in stiffness on cell behaviour and fate. Therefore, stimuli-responsive hydrogels have been developed to mimic the cells' microenvironment in a controlled fashion. Herein, we review strategies for dynamic modulation of stiffness using various stimuli, such as light, temperature and pH. Special emphasis is placed on conducting polymer (CP) hydrogels and their fabrication procedures. We believe that the redox properties of CPs and hydrogels' biological properties make CPs hydrogels a promising substrate to investigate the effect of dynamic stiffness changes and mechanical actuation on cell fate in future studies.

Engineered Bioactive Polymeric Surfaces by Radiation Induced Graft Copolymerization: Strategies and Applications

The interest in developing antimicrobial surfaces is currently surging with the rise in global infectious disease events. Radiation-induced graft copolymerization (RIGC) is a powerful technique enabling permanent tunable and desired surface modifications imparting antimicrobial properties to polymer substrates to prevent disease transmission and provide safer biomaterials and healthcare products. This review aims to provide a broader perspective of the progress taking place in strategies for designing various antimicrobial polymeric surfaces using RIGC methods and their applications in medical devices, healthcare, textile, tissue engineering and food packing. Particularly, the use of UV, plasma, electron beam (EB) and γ-rays for biocides covalent immobilization to various polymers surfaces including nonwoven fabrics, films, nanofibers, nanocomposites, catheters, sutures, wound dressing patches and contact lenses is reviewed. The different strategies to enhance the grafted antimicrobial properties are discussed with an emphasis on the emerging approach of in-situ formation of metal nanoparticles (NPs) in radiation grafted substrates. The current applications of the polymers with antimicrobial surfaces are discussed together with their future research directions. It is expected that this review would attract attention of researchers and scientists to realize the merits of RIGC in developing timely, necessary antimicrobial materials to mitigate the fast-growing microbial activities and promote hygienic lifestyles.

Radiation-Assisted Synthesis of Polymer-Based Nanomaterials

Radiation technology has long been proven as a simple, rapid, green and sustainable technology with macroscale applications in healthcare, industry and environment. Its merits, however, have not been fully utilized in today’s ever growing nanotechnology. Ionizing radiation has beneficial effects for the synthesis and modification of structure and properties of nanomaterials. This paper intends to update the application of ionizing radiation in the development of various nanomaterials under the categories: (i) carbon-based nanomaterials, (ii) metal-based nanomaterials, (iii) polymer-based nanomaterials, (iv) polymer nanocomposites and (v) nano-scale grafting for advanced membrane applications.

Oral Cavity as a Source of Mesenchymal Stem Cells Useful for Regenerative Medicine in Dentistry

The use of mesenchymal stem cells (MSCs) for regenerative purposes has become common in a large variety of diseases. In the dental and maxillofacial field, there are emerging clinical needs that could benefit from MSC-based therapeutic approaches. Even though MSCs can be isolated from different tissues, such as bone marrow, adipose tissue, etc., and are known for their multilineage differentiation, their different anatomical origin can affect the capability to differentiate into a specific tissue. For instance, MSCs isolated from the oral cavity might be more effective than adipose-derived stem cells (ASCs) for the treatment of dental defects. Indeed, in the oral cavity, there are different sources of MSCs that have been individually proposed as promising candidates for tissue engineering protocols. The therapeutic strategy based on MSCs can be direct, by using cells as components of the tissue to be regenerated, or indirect, aimed at delivering local growth factors, cytokines, and chemokines produced by the MSCs. Here, the authors outline the major sources of mesenchymal stem cells attainable from the oral cavity and discuss their possible usage in some of the most compelling therapeutic frontiers, such as periodontal disease and dental pulp regeneration.