Engineering of Cell Derived-Nanovesicle as an Alternative to Exosome Therapy

BACKGROUND

Exosomes, nano-sized vesicles ranging between 30 and 150 nm secreted by human cells, play a pivotal role in long-range intercellular communication and have attracted significant attention in the field of regenerative medicine. Nevertheless, their limited productivity and cost-effectiveness pose challenges for clinical applications. These issues have recently been addressed by cell-derived nanovesicles (CDNs), which are physically synthesized exosome-mimetic nanovesicles from parent cells, as a promising alternative to exosomes. CDNs exhibit structural, physical, and biological properties similar to exosomes, containing intracellular protein and genetic components encapsulated by the cell plasma membrane. These characteristics allow CDNs to be used as regenerative medicine and therapeutics on their own, or as a drug delivery system.

METHODS

The paper reviews diverse methods for CDN synthesis, current analysis techniques, and presents engineering strategies to improve lesion targeting efficiency and/or therapeutic efficacy.

RESULTS

CDNs, with their properties similar to those of exosomes, offer a cost-effective and highly productive alternative due to their non-living biomaterial nature, nano-size, and readiness for use, allowing them to overcome several limitations of conventional cell therapy methods.

CONCLUSION

Ongoing research and enhancement of CDNs engineering, along with comprehensive safety assessments and stability analysis, exhibit vast potential to advance regenerative medicine by enabling the development of efficient therapeutic interventions.

Risk of complications in panfacial bone fracture according to surgeons: A meta-analysis

BACKGROUND

Panfacial bone fractures pose intricate challenges because of severe fragmentation and the loss of landmarks. Surgeons use a variety of reduction techniques, including bottom-up and top-down approaches. This single proportional meta-analysis explores sequencing differences and complications between oral and maxillofacial surgery surgeons (OMSs) and plastic and reconstructive surgeons (PRSs) in treating panfacial bone fractures.

METHODS

The PubMed and Scopus databases were searched systematically, and we compiled 14 studies published between 2007 and 2023 involving 1238 patients. A systematic review of the included studies was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, and data on the reduction techniques; total complication rates; and rates of malocclusion, enophthalmos, infection, asymmetry, and esthetic complications were collected.

RESULTS

The bottom-up technique was the most prevalent for both types of surgeons (57.1%, 8 out of 14). Malocclusion rates (I2 = 0% for OMSs and 41% for PRSs) were similar between the groups (p = 0.72), but PRSs tended to have a lower enophthalmos rate (I2 = 0% for OMSs and 32% for PRSs) than OMSs (p < 0.01). Infection rates remained consistent across all studies. However, high heterogeneity was observed for the total complication rate (I2 = 94% for OMSs and 85% for PRSs) and asymmetry and esthetic complications (I2 = 88% for OMSs and 92% for PRSs), making direct comparison between the two groups inconclusive.

CONCLUSIONS

In this study, the differences in surgical techniques and levels of interest have a greater impact on the outcomes of the panfacial bone fracture than the surgeon's specialty. However, more in-depth studies are needed to accurately pinpoint panfacial bone fracture reduction trends and differences in postoperative complications in the two expert groups.

O2 variant chip to simulate site-specific skeletogenesis from hypoxic bone marrow

The stemness of bone marrow mesenchymal stem cells (BMSCs) is maintained by hypoxia. The oxygen level increases from vessel-free cartilage to hypoxic bone marrow and, furthermore, to vascularized bone, which might direct the chondrogenesis to osteogenesis and regenerate the skeletal system. Hence, oxygen was diffused from relatively low to high levels throughout a three-dimensional chip. When we cultured BMSCs in the chip and implanted them into the rabbit defect models of low-oxygen cartilage and high-oxygen calvaria bone, (i) the low oxygen level (base) promoted stemness and chondrogenesis of BMSCs with robust antioxidative potential; (ii) the middle level (two times ≥ low) pushed BMSCs to quiescence; and (iii) the high level (four times ≥ low) promoted osteogenesis by disturbing the redox balance and stemness. Last, endochondral or intramembranous osteogenesis upon transition from low to high oxygen in vivo suggests a developmental mechanism-driven solution to promote chondrogenesis to osteogenesis in the skeletal system by regulating the oxygen environment.

Glucose as a Risk Factor for Periodontitis in Kidney Transplantation Patients

BACKGROUND

Various factors including diabetes and oxidative stress are associated with periodontal inflammation. End-stage renal disease causes various systemic abnormalities in patients, including cardiovascular disaese, metabolic abnormalities, and infection. Even after kidney transplantation (KT), these factors are known to be associated with inflammation. Our study, therefore, aimed to study risk factors associated with periodontitis in KT patients.

METHODS

Patients who visited Dongsan Hospital, Daegu, Korea since 2018 and have undergone KT were selected. As of November 2021, 923 participants, with full data including hematologic factors were studied. Periodontitis was diagnosed based on residual bone level in panoramic views. Patients were studied by the presence of periodontitis.

RESULTS

From 923 KT patients, 30 were diagnosed with periodontal disease. Fasting glucose levels were higher in patients with periodontal disease, and total bilirubin levels were lower. When divided by fasting glucose levels, high glucose level showed increase of periodontal disease with odds ratio of 1.031 (95% confidence interval 1.004-1.060). After adjusting for confounders, the results were significant with odds ratio of 1.032 (95% CI 1.004-1.061).

CONCLUSIONS

Our study showed that KT patients, of whom uremic toxin clearance has been revolted, are yet at risk of periodontitis by other factors, such as high blood glucose levels.

Sprayable nanomicelle hydrogels and inflammatory bowel disease patient cell chips for development of intestinal lesion-specific therapy

All-in-one treatments represent a paradigm shift in future medicine. For example, inflammatory bowel disease (IBD) is mainly diagnosed by endoscopy, which could be applied for not only on-site monitoring but also the intestinal lesion-targeted spray of injectable hydrogels. Furthermore, molecular conjugation to the hydrogels would program both lesion-specific adhesion and drug-free therapy. This study validated this concept of all-in-one treatment by first utilizing a well-known injectable hydrogel that underwent efficient solution-to-gel transition and nanomicelle formation as a translatable component. These properties enabled spraying of the hydrogel onto the intestinal walls during endoscopy. Next, peptide conjugation to the hydrogel guided endoscopic monitoring of IBD progress upon adhesive gelation with subsequent moisturization of inflammatory lesions, specifically by nanomicelles. The peptide was designed to mimic the major component that mediates intestinal interaction with Bacillus subtilis flagellin during IBD initiation. Hence, the peptide-guided efficient adhesion of the hydrogel nanomicelles onto Toll-like receptor 5 (TLR5) as the main target of flagellin binding and Notch-1. The peptide binding potently suppressed inflammatory signaling without drug loading, where TLR5 and Notch-1 operated collaboratively through downstream actions of tumor necrosis factor-alpha. The results were produced using a human colorectal cell line, clinical IBD patient cells, gut-on-a-chip, a mouse IBD model, and pig experiments to validate the translational utility.

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Injectable nanomicelle hydrogel for all-in-one treatment of intestinal inflammation.

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Spraying of the hydrogel onto the intestinal walls during endoscopy.

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Peptide-guided detection and moisturization of inflammatory lesions.

Quenching Epigenetic Drug Resistance Using Antihypoxic Microparticles in Glioblastoma Patient-Derived Chips

Glioblastoma (GBM) is one of the most intractable tumor types due to the progressive drug resistance upon tumor mass expansion. Incremental hypoxia inside the growing tumor mass drives epigenetic drug resistance by activating nongenetic repair of antiapoptotic DNA, which could be impaired by drug treatment. Hence, rescuing intertumor hypoxia by oxygen-generating microparticles may promote susceptibility to antitumor drugs. Moreover, a tumor-on-a-chip model enables user-specified alternation of clinic-derived samples. This study utilizes patient-derived glioblastoma tissue to generate cell spheroids with size variations in a 3D microchannel network chip (GBM chip). As the spheroid size increases, epigenetic drug resistance is promoted with inward hypoxia severance, as supported by the spheroid size-proportional expression of hypoxia-inducible factor-1a in the chip. Loading antihypoxia microparticles onto the spheroid surface significantly reduces drug resistance by silencing the expression of critical epigenetic factor, resulting in significantly decreased cell invasiveness. The results are confirmed in vitro using cell line and patient samples in the chip as well as chip implantation into a hypoxic hindlimb ischemia model in mice, which is an unprecedented approach in the field.

Cell-Membrane-Derived Nanoparticles with Notch-1 Suppressor Delivery Promote Hypoxic Cell-Cell Packing and Inhibit Angiogenesis Acting as a Two-Edged Sword

Cell-cell interactions regulate intracellular signaling via reciprocal contacts of cell membranes in tissue regeneration and cancer growth, indicating a critical need of membrane-derived tools in studying these processes. Hence, cell-membrane-derived nanoparticles (CMNPs) are produced using tonsil-derived mesenchymal stem cells (TMSCs) from children owing to their short doubling time. As target cell types, laryngeal cancer cells are compared to bone-marrow-derived MSCs (BMSCs) because of their cartilage damaging and chondrogenic characteristics, respectively. Treating spheroids of these cell types with CMNPs exacerbates interspheroid hypoxia with robust maintenance of the cell-cell interaction signature for 7 days. Both cell types prefer a hypoxic environment, as opposed to blood vessel formation that is absent in cartilage but is required for cancer growth. Hence, angiogenesis is inhibited by displaying the Notch-1 aptamer on CMNPs. Consequently, laryngeal cancer growth is suppressed efficiently in contrast to improved chondroprotection observed in a series of cell and animal experiments using a xenograft mouse model of laryngeal cancer. Altogether, CMNPs execute a two-edged sword function of inducing hypoxic cell-cell packing, followed by suppressing angiogenesis to promote laryngeal cancer death and chondrogenesis simultaneously. This study presents a previously unexplored therapeutic strategy for anti-cancer and chondroprotective treatment using CMNPs.

Dilation-Responsive Microshape Programing Prevents Vascular Graft Stenosis

Shape memory materials have been successfully applied to minimally invasive implantation of medical devices. However, organ-movement-specific shape programing at a microscale level has never been demonstrated despite significant unmet needs. As vein-to-artery grafting induces vein dilation and stenosis, a polymeric self-enclosable external support (SES) is designed to wrap the vascular out-wall. Its micropores are programmed to increase sizes and interconnections upon dilation. Vessel dilation promotes venous maturation, but overdilation induces stenosis by disturbed blood flow. Therefore, the unique elastic shape-fixity of SES provides a foundation to enable a stable microscale shape transition by maintaining the vein dilation. The shape transition of micropore architecture upon dilation induces beneficial inflammation, thereby regenerating vasa vasorum and directing smooth muscle cell migration toward adventitia with the consequent muscle reinforcement of veins. This game-changer approach prevents the stenosis of vein-to-artery grafting by rescuing ischemic disorders and promoting arterial properties of veins.

Hormone autocrination by vascularized hydrogel delivery of ovary spheroids to rescue ovarian dysfunctions

The regeneration potential of implantable organ model hydrogels is applied to treat a loss of ovarian endocrine function in women experiencing menopause and/or cancer therapy. A rat ovariectomy model is used to harvest autologous ovary cells while subsequently producing a layer-by-layer form of follicle spheroids. Implantation of a microchannel network hydrogel with cell spheroids [vascularized hydrogel with ovarian spheroids (VHOS)] into an ischemic hindlimb of ovariectomized rats significantly aids the recovery of endocrine function with hormone release, leading to full endometrium regeneration. The VHOS implantation effectively suppresses the side effects observed with synthetic hormone treatment (i.e., tissue overgrowth, hyperplasia, cancer progression, deep vein thrombosis) to the normal levels, while effectively preventing the representative aftereffects of menopause (i.e., gaining fatty weight, inducing osteoporosis). These results highlight the unprecedented therapeutic potential of an implantable VHOS against menopause and suggest that it may be used as an alternative approach to standard hormone therapy.

Polydopamine-assisted one-step modification of nanofiber surfaces with adenosine to tune the osteogenic differentiation of mesenchymal stem cells and the maturation of osteoclasts

Adenosine and its receptors have emerged as alternative targets to control cellular functions for bone healing. However, the soluble delivery of adenosine has not proven effective because of its fast degradation in vivo. We therefore designed a stable coating of adenosine for biomaterial surfaces through polydopamine chemistry to control osteogenesis and osteoclastogenesis via A2bR signaling. First, we prepared electrospun poly (ι-lactic acid) (PLLA) nanofiber sheets, which were modified through a one-step adenosine polydopamine coating process. Scanning electron microscopy (SEM) revealed deposition of particles on the adenosine polydopamine-coated PLLA (AP-PL) sheets compared to the polydopamine-only sheets. Moreover, X-ray photoelectron spectroscopy analysis confirmed an increase in nitrogen signals due to adenosine. Furthermore, adenosine loading efficiency and retention were significantly enhanced in AP-PL sheets compared to polydopamine-only sheets. Human adipose-derived stem cells (hADSCs) cultured on AP-PL expressed A2bR (1.30 ± 0.19 fold) at significantly higher levels than those cultured on polydopamine-only sheets. This in turn significantly elevated the expression of Runx2 (16.94 ± 1.68 and 51.69 ± 0.07 fold), OPN (1.63 ± 0.16 and 30.56 ± 0.25 fold), OCN (1.16 ± 0.13 and 5.23 ± 0.16 fold), and OSX (10.01 ± 0.81 and 62.48 ± 0.25 fold) in cells grown in growth media on days 14 and 21, respectively. Similarly, mineral deposition was enhanced to a greater extent in the AP-PL group than the polydopamine group, while blocking of A2bR significantly downregulated osteogenesis. Finally, osteoclast differentiation of RAW 264.7 cells was significantly inhibited by growth on AP-PL sheets. However, osteoclast differentiation was significantly stimulated after A2bR was blocked. Taken together, we propose that polydopamine-assisted one-step coating of adenosine is a viable method for surface modification of biomaterials to control osteogenic differentiation of stem cells and bone healing.

Anti-Atherogenic Effect of Stem Cell Nanovesicles Targeting Disturbed Flow Sites

Atherosclerosis development leads to irreversible cascades, highlighting the unmet need for improved methods of early diagnosis and prevention. Disturbed flow formation is one of the earliest atherogenic events, resulting in increased endothelial permeability and subsequent monocyte recruitment. Here, a mesenchymal stem cell (MSC)-derived nanovesicle (NV) that can target disturbed flow sites with the peptide GSPREYTSYMPH (PREY) (PMSC-NVs) is presented which is selected through phage display screening of a hundred million peptides. The PMSC-NVs are effectively produced from human MSCs (hMSCs) using plasmid DNA designed to functionalize the cell membrane with PREY. The potent anti-inflammatory and pro-endothelial recovery effects are confirmed, similar to those of hMSCs, employing mouse and porcine partial carotid artery ligation models as well as a microfluidic disturbed flow model with human carotid artery-derived endothelial cells. This nanoscale platform is expected to contribute to the development of new theragnostic strategies for preventing the progression of atherosclerosis.

Microchannel network hydrogel induced ischemic blood perfusion connection

Angiogenesis induction into damaged sites has long been an unresolved issue. Local treatment with pro-angiogenic molecules has been the most common approach. However, this approach has critical side effects including inflammatory coupling, tumorous vascular activation, and off-target circulation. Here, the concept that a structure can guide desirable biological function is applied to physically engineer three-dimensional channel networks in implant sites, without any therapeutic treatment. Microchannel networks are generated in a gelatin hydrogel to overcome the diffusion limit of nutrients and oxygen three-dimensionally. Hydrogel implantation in mouse and porcine models of hindlimb ischemia rescues severely damaged tissues by the ingrowth of neighboring host vessels with microchannel perfusion. This effect is guided by microchannel size-specific regenerative macrophage polarization with the consequent functional recovery of endothelial cells. Multiple-site implantation reveals hypoxia and neighboring vessels as major causative factors of the beneficial function. This technique may contribute to the development of therapeutics for hypoxia/inflammatory-related diseases.

Stem cell spheroids incorporating fibers coated with adenosine and polydopamine as a modular building blocks for bone tissue engineering

Although stem cell spheroids offer great potential as functional building blocks for bottom-up bone tissue engineering, delivery of bioactive signals remain challenging. Here, we engineered adenosine-ligand-modified fiber fragments to create a 3D cell-instructive microenvironment for bone. Briefly, the Poly(ι-lactic acid) (PLLA) nanofiber sheet was partially degraded into fragmented fibers (FFs) through aminolysis and adenosine was stably incorporated via one-step polydopamine coating. The SEM and XPS analysis demonstrated that polydopamine assisted adenosine coating efficiency was significantly increased, which led to high coating efficiency of adenosine and its significant retention. The engineered fibers were then assembled into stable spheroids with human-adipose-derived stem cells (hADSCs). The adenosine in the spheroids effectively stimulated A2bR (1.768 ± 0.08) signaling, which further significantly induced the expression of osteogenic markers such as Runx2 (3.216 ± 0.25), OPN (4.136 ± 0.14), OCN (10.16 ± 0.34), and OSX (2.27 ± 0.11) with improved mineral deposition (1.375 ± 0.05 μg per spheroid). In contrast, the adipogenic differentiation of hADSCs was significantly suppressed within the engineered spheroids. Transplantation of engineered spheroids strongly induced osteogenic differentiation of hADSCs in ectopic subcutaneous tissue. Finally, the bone regeneration was significantly enhanced by implanting AP-FF group (59.97 ± 18.33%) as compared to P-FF (27.96 ± 11.14) and defect only (7.97 ± 3.76%). We propose that stem cell spheroids impregnated with engineered fibers enabling adenosine delivery could be promising building blocks for a bottom-up approach to create large tissues for regeneration of damaged bone.

Current progress in application of polymeric nanofibers to tissue engineering

Tissue engineering uses a combination of cell biology, chemistry, and biomaterials to fabricate three dimensional (3D) tissues that mimic the architecture of extracellular matrix (ECM) comprising diverse interwoven nanofibrous structure. Among several methods for producing nanofibrous scaffolds, electrospinning has gained intense interest because it can make nanofibers with a porous structure and high specific surface area. The processing and solution parameters of electrospinning can considerably affect the assembly and structural morphology of the fabricated nanofibers. Electrospun nanofibers can be made from natural or synthetic polymers and blending them is a straightforward way to tune the functionality of the nanofibers. Furthermore, the electrospun nanofibers can be functionalized with various surface modification strategies. In this review, we highlight the latest achievements in fabricating electrospun nanofibers and describe various ways to modify the surface and structure of scaffolds to promote their functionality. We also summarize the application of advanced polymeric nanofibrous scaffolds in the regeneration of human bone, cartilage, vascular tissues, and tendons/ligaments.

Development of a Shape-Memory Tube to Prevent Vascular Stenosis

Inserting a graft into vessels with different diameters frequently causes severe damage to the host vessels. Poor flow patency is an unresolved issue in grafts, particularly those with diameters less than 6 mm, because of vessel occlusion caused by disturbed blood flow following fast clotting. Herein, successful patency in the deployment of an ≈2 mm diameter graft into a porcine vessel is reported. A new library of property-tunable shape-memory polymers that prevent vessel damage by expanding the graft diameter circumferentially upon implantation is presented. The polymers undergo seven consecutive cycles of strain energy-preserved shape programming. Moreover, the new graft tube, which features a diffuser shape, minimizes disturbed flow formation and prevents thrombosis because its surface is coated with nitric-oxide-releasing peptides. Improved patency in a porcine vessel for 18 d is demonstrated while occlusive vascular remodeling occurs. These insights will help advance vascular graft design.

Experimental Tracheal Replacement Using 3-dimensional Bioprinted Artificial Trachea with Autologous Epithelial Cells and Chondrocytes

Various treatment methods for tracheal defects have been attempted, such as artificial implants, allografts, autogenous grafts, and tissue engineering; however, no perfect method has been established. We attempted to create an effective artificial trachea via a tissue engineering method using 3D bio-printing. A multi-layered scaffold was fabricated using a 3D printer. Polycaprolactone (PCL) and hydrogel were used with nasal epithelial and auricular cartilage cells in the printing process. An artificial trachea was transplanted into 15 rabbits and a PCL scaffold without the addition of cells was transplanted into 6 rabbits (controls). All animals were followed up with radiography, CT, and endoscopy at 3, 6, and 12 months. In the control group, 3 out of 6 rabbits died from respiratory symptoms. Surviving rabbits in control group had narrowed tracheas due to the formation of granulation tissue and absence of epithelium regeneration. In the experimental group, 13 of 15 animals survived, and the histologic examination confirmed the regeneration of epithelial cells. Neonatal cartilage was also confirmed at 6 and 12 months. Our artificial trachea was effective in the regeneration of respiratory epithelium, but not in cartilage regeneration. Additional studies are needed to promote cartilage regeneration and improve implant stability.

ROS-Responsive Biomaterial Design for Medical Applications

Stimuli-responsive biomaterials undergo significant alterations in material structure and property in response to changes of local environmental factors (e.g. pH, temperature, enzyme activation, and water absorption). In particular, reactive oxygen species (ROS) is considered as a major stimulus because over-production of ROS involves most types of major pathogenesis. The application of ROS-responsive biomaterials requires suitable material designs to program user-defined changes of their structure and property in response to a sudden change in the local ROS level. This chapter summarizes the progress in designing and applying major types of ROS-responsive biomaterials within the past 10 years.

Fabrication of in vitro 3D mineralized tissue by fusion of composite spheroids incorporating biomineral-coated nanofibers and human adipose-derived stem cells

Development of a bone-like 3D microenvironment with stem cells has always been intriguing in bone tissue engineering. In this study, we fabricated composite spheroids by combining functionalized fibers and human adipose-derived stem cells (hADSCs), which were fused to form a 3D mineralized tissue construct. We prepared fragmented poly (ι-lactic acid) (PLLA) fibers approximately 100 μm long by partial aminolysis of electrospun fibrous mesh. PLLA fibers were then biomineralized with various concentrations of NaHCO₃ (0.005, 0.01, and 0.04 M) to form mineralized fragmented fibers (mFF1, mFF2, and mFF3, respectively). SEM analysis showed that the minerals in mFF2 and mFF3 completely covered the fiber surface, and surface chemistry analysis confirmed the presence of hydroxyapatite peaks. Additionally, mFFs formed composite spheroids with hADSCs, demonstrating that the cells were strongly attached to mFFs and homogeneously distributed throughout the spheroid. In vitro culture of spheroids in the media without osteogenic supplements showed significantly enhanced expression of osteogenic genes including Runx2 (20.83 ± 2.83 and 22.36 ± 2.18 fold increase), OPN (14.24 ± 1.71 and 15.076 ± 1.38 fold increase), and OCN (4.36 ± 0.41 and 5.63 ± 0.51 fold increase) in mFF2 and mFF3, respectively, compared to the no mineral fiber group. In addition, mineral contents were significantly increased at day 7. Blocking the biomineral-mediated signaling by PSB 603 significantly down regulated the expression of these genes in mFF3 at day 7. Finally, we fused composite spheroids to form a mineralized 3D tissue construct, which maintained the viability of cells and showed pervasively distributed minerals within the structure. Our composite spheroids could be used as an alternative platform for the development of in vitro bone models, in vivo cell carriers, and as building blocks for bioprinting 3D bone tissue.

STATEMENT OF SIGNIFICANCE

This manuscript described our recent work for the preparation of biomimeral-coated fibers that can be assembled with mesenchymal stem cells and provide bone-like environment for directed control over osteogenic differentiation. Biomineral coating onto synthetic, biodegradable single fibers was successfully carried out using multiple steps, combination of template protein coating inspired from mussel adhesion and charge-charge interactions between template proteins and mineral ions. The biomineral-coated single micro-scale fibers (1-2.5 μm in diameter) were then assembled with human adipose tissue derived stem cells (hADSCs). The assembled structure exhibited spheroidal architecture with few hundred micrometers. hADSCs within the spheroids were differentiated into osteogenic lineage in vitro and mineralized in the growth media. These spheroids were fused to form in vitro 3D mineralized tissue with larger size.

Tissue Engineering and Regenerative Medicine 2017: A Year in Review

In 2017, a new paradigm change caused by artificial intelligence and big data analysis resulted in innovation in each field of science and technology, and also significantly influenced progress in tissue engineering and regenerative medicine (TERM). TERM has continued to make technological advances based on interdisciplinary approaches and has contributed to the overall field of biomedical technology, including cancer biology, personalized medicine, development biology, and cell-based therapeutics. While researchers are aware that there is still a long way to go until TERM reaches the ultimate goal of patient treatment through clinical translation, the rapid progress in convergence studies led by technological improvements in TERM has been encouraging. In this review, we highlighted the significant advances made in TERM in 2017 (with an overlap of 5 months in 2016). We identified major progress in TERM in a manner similar to previous reviews published in the last few years. In addition, we carefully considered all four previous reviews during the selection process and chose main themes that minimize the duplication of the topics. Therefore, we have identified three areas that have been the focus of most journal publications in the TERM community in 2017: (i) advanced biomaterials and three-dimensional (3D) cell printing, (ii) exosomes as bioactive agents for regenerative medicine, and (iii) 3D culture in regenerative medicine.

Advanced capability of radially aligned fibrous scaffolds coated with polydopamine for guiding directional migration of human mesenchymal stem cells

In a large tissue defect, faster migration of adjacent tissue toward the defect shortens the tissue regeneration time. Little has been explored on guiding of directional migration from all fronts of the defect boundary towards the center in tissue engineering. This paper demonstrates the effect of radially aligned fibrous scaffolds (RAFSs) coated with polydopamine in order to guide directional migration of human mesenchymal stem cells (hMSCs). RAFSs were electrospun using a collector with a set of electrodes, each constructed with a metallic ring and a point. The polydopamine was then coated by dipping the scaffolds in a dopamine solution (PD-RAFS). The RAFSs exhibited radial distribution of the fibers from the peripheral region toward the center, and polydopamine was uniformly coated over the entire surface by presenting characteristics of the aromatic ring from dopamine. When hMSCs were seeded on the scaffolds, cells grew in an elongated form toward the center along the fiber direction. In particular, the polydopamine coating improved adhesion and spreading of hMSCs on the scaffolds while preserving initial cell orientation. The hMSCs migrated toward the center of the scaffolds at the border of the seeded area; it was enhanced in the order of PD-RAFS > RAFS > random fibrous scaffolds. Therefore, PD-RAFSs can be utilized as an alternate scaffold that can lead to fast and directional migration of cells for finally facilitating tissue regeneration.

Engineering an aligned endothelial monolayer on a topologically modified nanofibrous platform with a micropatterned structure produced by femtosecond laser ablation

Laser ablated nanofibers with micropattern regulated adhesion and orientation of HUVEC and also contributed to generate an aligned endothelial monolayer.

Oxygen-dependent generation of a graded polydopamine coating on nanofibrous materials for controlling stem cell functions

A nanofiber with gradient in polydopamine coating was generated by controlling oxidative polymerization of dopamine for tuning stem cell responses.

Facile Cell Sheet Harvest and Translocation Mediated by a Thermally Expandable Hydrogel with Controlled Cell Adhesion

Facile cell sheet translocation system is developed based on a thermally expandable hydrogel with modular cell adhesion favorable for both robust cell sheet formation and harvest. Efficient translocation is achieved at moderate cell-substrate interaction, which can be tuned by two-step reactions of mussel-inspired coating.

Mussel adhesive protein inspired coatings on temperature-responsive hydrogels for cell sheet engineering

A cell sheet translocation system is developed based on a temperature-responsive hydrogel with modular cell adhesion properties by a mussel-inspired polydopamine coating.

Radiofrequency ablation as an alternative to hepatic resection for single small hepatocellular carcinomas

Background

This study aimed to investigate whether radiofrequency ablation (RFA) is an alternative to surgical resection for hepatocellular carcinoma (HCC) within the context of current guidelines.

Methods

This retrospective study included patients with normal portal pressure and serum bilirubin level who initially underwent liver resection or RFA for a single HCC of maximum size 3 cm. Between-group differences in cumulative rates of survival and recurrence specific for HCC were analysed in the entire cohort and in a propensity score-matched cohort.

Results

A total of 604 patients were enrolled, 273 in the liver resection group and 331 in the RFA group. The 5- and 10-year HCC-specific survival rates for the resection and RFA groups were 87·6 versus 82·1 per cent and 59·0 versus 61·2 per cent respectively (P = 0·214), whereas overall 5- and 10-year recurrence-free survival rates for the corresponding groups were 60·6 versus 39·4 per cent and 37·5 versus 25·1 per cent respectively (P &lt; 0·001). In the propensity score-matched cohort (152 pairs), there were no differences in HCC-specific survival (hazard ratio (HR) 1·03 for RFAversus resection; P = 0·899), whereas recurrence-free survival again differed between the treatment groups (HR 1·75; P &lt; 0·001). RFA was independently associated with poorer outcomes in terms of treatment-site recurrence-free survival (adjusted HR 1·66; P = 0·026), but not non-treatment-site recurrence-free survival (adjusted HR 1·15; P = 0·354).

Conclusion

Although RFA carries a higher risk of treatment-site recurrence than hepatic resection, it provides comparable overall survival in patients with a single small HCC without portal hypertension or a raised bilirubin level.

Effect of immobilized collagen type IV on biological properties of endothelial cells for the enhanced endothelialization of synthetic vascular graft materials

Regeneration of healthy endothelium onto vascular graft materials is imperative for prevention of intimal hyperplasia and thrombogenesis. In this study, we investigated the effect of collagen type IV (COL-IV) immobilized onto electrospun nanofibers on modulation of endothelial cell (EC) function, as a potential signal to rapid endothelialization of vascular grafts. COL-IV is assembled in basement membrane underneath intimal layer and regulates morphogenesis of blood vessels. For immobilization of COL-IV, poly(l-lactic acid) (PLLA) nanofibers (PL) were prepared as a model vascular graft substrate, onto which acrylic acid (AAc) was then grafted by using gamma-ray irradiation. AAc graft was dependent on irradiation doses and AAc concentrations, which allowed us to select the condition of 5% (v/v) AAc and 10 kGy for further conjugation of COL-IV. COL-IV immobilization was proportionally controlled as a function of its concentration. Atomic force microscope (AFM) analysis qualitatively supported immobilization of COL-IV, demonstrating increase in root mean square roughness of the PL from 665.37 ± 13.20 nm to 1440.74 ± 33.24. However, the Young's modulus of nanofibers was retained as approximately 1 MPa, regardless of surface modification. The number of ECs attached on the nanofibers with immobilized COL-IV was significantly increased by 5 times (1052 ± 138 cells/mm(2)) from pristine PL (234 ± 41 cells/mm(2)). In addition, the effect of immobilized COL-IV was profound for enhancing proliferation and up-regulation of markers implicated in rapid endothelialization. Collectively, our results suggest that COL-IV immobilized onto electrospun PLLA nanofibers may serve as a promising instructive cue used in vascular graft materials.

Extracellular matrix-inspired BMP-2-delivering biodegradable fibrous particles for bone tissue engineering

A heparin conjugated fibrous particle resembling the structure of an extracellular matrix was developed. The BMP-2 loaded particles promoted osteogenic differentiation and healing of a bone defect, in vitro and in vivo.

Modulation of human mesenchymal stem cell survival on electrospun mesh with co-immobilized epithelial growth factor and gelatin

Co-immobilization of EGF and gelatin on a fibrous mesh promotes spreading and viability of hMSC, and coupled EGF involves involucrin expression and procollagen secretion, indicating trans-differentiation to keratinocyte-like cell.

Engineered ECM-like microenvironment with fibrous particles for guiding 3D-encapsulated hMSC behaviours

The incorporation of RGD-coupled fibrous particles into the alginate hydrogel promotes 3D-encapsulated cell behaviours by allowing mutual binding with the particles.

Reconstruction of vascular structure with multicellular components using cell transfer printing methods

Natural vessel has three types of concentric cell layers that perform their specific functions. Here, the fabrication of vascular structure is reported by transfer printing of three different cell layers using thermosensitive hydrogels. Tetronic-tyramine and RGD peptide are co-crosslinked to prepare cell adhesive and thermosensitive hydrogels. The hydrogel increases its diameter by 1.26 times when the temperature reduces from 37 °C to 4 °C. At optimized seeding density, three types of cells form monolayers on the hydrogel, which is then transferred to the target surface within 3 min. Three monolayers are simultaneously transferred on one substrate with controlled shape and arrangement. The same approach is applied onto nanofiber scaffolds that are cultured for more than 5 d. Every type of monolayer shows proliferation and migration on nanofiber scaffolds, and the formation of robust cell-cell contact is revealed by CD31 staining in endothelial cell layer. A vascular structure with multicellular components is fabricated by transfer of three monolayers on nanofibers that are manually rolled with the diameter and length of the tube being approximately 3 mm and 12 mm, respectively. Collectively, it is concluded that the tissue transfer printing is a useful tool for constructing a vascular structure and mimicking natural structure of different types of tissues.

Synergistic effect of dual-functionalized fibrous scaffold with BCP and RGD containing peptide for improved osteogenic differentiation

Over the last decade, bone tissue engineering scaffolds have been advanced owing to the bioceramic incorporation and biomimetic modification. In this report, a dual-functional fibrous scaffold with a bioceramic and biomolecule is developed, and a combined effect of a dual-modification is investigated. Biphasic calcium phosphate (BCP) is incorporated in electrospun poly (L-lactide) scaffolds, and Arg-Gly-Asp (RGD) peptide is then conjugated through the graft polymerization of acrylic acid by γ-ray irradiation. The scaffolds exhibit the intrinsic properties of BCP as well as RGD peptide, and only RGD peptide improves an adhesion and proliferation of the human mesenchymal stem cell. However, alkaline phosphatase activity and calcium formation are synergistically improved by the BCP and RGD peptide indicating that a favorable microenvironment is constructed for bone formation. Therefore, this combination strategy with bioceramic and biomolecule can be a useful tool for the bone tissue engineering.

Polydopamine-mediated immobilization of multiple bioactive molecules for the development of functional vascular graft materials

In this study, we introduced a simple method for polydopamine-mediated immobilization of dual bioactive factors for the preparation of functionalized vascular graft materials. Polydopamine was deposited on elastic and biodegradable poly(lactic acid-co-ɛ-caprolactone) (PLCL) films, and a cell adhesive RGD-containing peptide and basic fibroblast growth factor were subsequently immobilized by simple dipping. We used an enzyme-linked immunosorbent assay and fluorescamine assay to confirm that we had stably immobilized bioactive molecules on the polydopamine-coated PLCL film in a reaction time-dependent manner. When human umbilical vein endothelial cells (HUVEC) were cultured on the prepared substrates, the number of adherent cells and proliferation of HUVEC for up to 14 days were greatest on the film immobilized with dual factors. On the other hand, the film immobilized with RGD peptide exhibited the highest migration speed compared to the other groups. The expression of cluster of differentiation 31 and von Willebrand factor, which indicates maturation of endothelial cells, was highly stimulated in the dual factor-immobilized group, and passively adsorbed factors showed a negligible effect. The immobilization of bioactive molecules inspired by polydopamine was successful, and adhesion, migration, proliferation and differentiation of HUVEC were synergistically accelerated by the presence of multiple signaling factors. Collectively, our results have demonstrated that a simple coating with polydopamine enables the immobilization of multiple bioactive molecules for preparation of polymeric functionalized vascular graft materials.

Mussel-inspired immobilization of vascular endothelial growth factor (VEGF) for enhanced endothelialization of vascular grafts

Most polymeric vascular prosthetic materials have low patency rate for replacement of small diameter vessels (<5 mm), mainly due to failure to generate healthy endothelium. In this study, we present polydopamine-mediated immobilization of growth factors on the surface of polymeric materials as a versatile tool to modify surface characteristics of vascular grafts potentially for accelerated endothelialization. Polydopamine was deposited on the surface of biocompatible poly(L-lactide-co-ε-caprolactone) (PLCL) elastomer, on which vascular endothelial growth factor (VEGF) was subsequently immobilized by simple dipping. Surface characteristics and composition were investigated by using scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Immobilization of VEGF on the polydopamine-deposited PLCL films was effective (19.8 ± 0.4 and 197.4 ± 19.7 ng/cm(2) for DPv20 and DPv200 films, respectively), and biotin-mediated labeling of immobilized VEGF revealed that the fluorescence intensity increased as a function of the concentration of VEGF solution. The effect of VEGF on adhesion of HUVECs was marginal, which may have been masked by polydopamine layer that also enhanced cell adhesion. However, VEGF-immobilized substrate significantly enhanced proliferation of HUVECs for over 7 days of in vitro culture and also improved their migration. In addition, immobilized VEGF supported robust cell to cell interactions with strong expression of CD 31 marker. The same process was effective for immobilization of basic fibroblast growth factor, demonstrating the robustness of polydopamine layer for secondary ligation of growth factors as a simple and novel surface modification strategy for vascular graft materials.

The acute and long-term effectiveness of amisulpride in patients with schizophrenia: results of a 12-month open-label prospective follow-up study

OBJECTIVE

To compare the effectiveness of amisulpride in acute (up to 8 weeks) and maintenance (week 8 to 12 months) phases of a 12-month course of treatment in a heterogeneous group of patients with schizophrenia.

METHODS

We conducted a 12-month, open-label clinical trial with flexible doses of amisulpride among 129 Korean patients with schizophrenia. The Positive and Negative Symptom Scale (PANSS) and several other scales measuring efficacy and tolerability were analyzed during the acute and maintenance phases.

RESULTS

The completion rates were 78.3% by week 8 and 55.8% by month 12. Total PANSS scores and scores on the negative-symptom and general-symptom subscales improved significantly during both acute and maintenance periods, but scores on the positive-symptom subscale improved only during the acute phase. Improvement during both treatment phases was significant in all other scales except for the Drug Attitude Inventory. The negative-symptom and mixed-symptom groups showed significant improvement in the PANSS negative subscale, the Clinical Global Impression scale, and the Global Assessment of Functioning during the maintenance period. Hyperprolactinemia and related events were commonly reported.

CONCLUSIONS

This study demonstrated the significant effectiveness and a good safety profile of amisulpride for treating acute and 12-month phases of schizophrenia under natural conditions.

Mussel-inspired surface modification of poly(L-lactide) electrospun fibers for modulation of osteogenic differentiation of human mesenchymal stem cells

Development of biomaterials to control the fate of stem cells is important for stem cell based regeneration of bone tissue. The objective of this study is to develop functionalized electrospun fibers using a mussel-inspired surface coating to regulate adhesion, proliferation and differentiation of human mesenchymal stem cells (hMSCs). We prepared poly(L-lactide) (PLLA) fibers coated with polydopamine (PD-PLLA). The morphology, chemical composition, and surface properties of fiber were characterized by SEM, AFM, XPS, Raman spectra and water contact angle measurements. Incubation of fibers in dopamine solution for 1h resulted in formation of polydopamine with only negligible effects on the roughness and hydrophobicity of the fibers. However, PD-PLLA fibers modulated hMSC responses in several aspects. Firstly, adhesion and proliferation of hMSCs cultured on PD-PLLA were significantly enhanced relative to those on PLLA. In addition, the ALP activity of hMSCs cultured on PD-PLLA (1.74±0.14 nmole/DNA/30 min) was significantly higher than on PLLA (0.97±0.07 nmole/DNA/30 min). hMSCs cultured on PD-PLLA showed up-regulation of genes associated with osteogenic differentiation as well as angiogenesis. Furthermore, the calcium deposition from hMSCs cultured on PD-PLLA (41.60±1.74 μg) was significantly greater than that on PLLA (30.15±1.21 μg), which was double-confirmed by alizarin red S staining. Our results suggest that the bio-inspired coating synthetic degradable polymer can be used as a simple technique to render the surface of synthetic biodegradable fibers to be active for directing the specific responses of hMSCs.

Acute respiratory distress syndrome caused by miliary tuberculosis: a multicentre survey in South Korea

BACKGROUND

Miliary tuberculosis (TB) is an unusual cause of acute respiratory distress syndrome (ARDS).

OBJECTIVE

To evaluate the clinical characteristics and outcomes of patients with ARDS caused by miliary TB admitted to the intensive care unit (ICU).

DESIGN

A total of 67 patients were enrolled during the period 1999-2008.

RESULTS

The median age of the patients was 56 years (range 17-81), 19 (28.4%) were aged >71 years, and 38 (56.7%) were male. All-cause mortality in the ICU and hospital were respectively 58.2% and 61.2%. Of the total number of enrolled patients, 49 (73.1%) were prescribed anti-tuberculosis medication within 3 days of hospital admission. On the day of ARDS diagnosis (10.0 ± 3.7 vs. 7.4 ± 3.5, P = 0.005), non-survivors had a significantly higher Sequential Organ Failure Assessment (SOFA) score than survivors. Multivariate analysis showed that SOFA score on the day of ARDS diagnosis was a significant predictor of survival (OR 0.809, 95%CI 0.691-0.946, P = 0.008). It was difficult to determine the efficacy of systemic corticosteroids on patient survival.

CONCLUSION

ARDS caused by miliary TB was associated with a high in-hospital mortality rate, with SOFA score on the day of ARDS diagnosis being a valuable prognostic indicator.

Effect of splenic artery embolization for splenic artery steal syndrome in liver transplant recipients: estimation at computed tomography based on changes in caliber of related arteries

PURPOSE

To estimate the effect of splenic artery embolization (SAE) on blood flow in orthotopic liver transplantation (OLT) recipients with splenic artery steal syndrome (SASS) based on changes in caliber of related arteries upon serial computed tomography (CT) scans.

METHODS

Between 2004 and 2007, nine OLT recipients with SASS underwent SAE. They had CT scans before and after SAE: short-, mid-, and long-term, ie, approximately 1 week, 1 month, and 1 year, respectively. The diameters of the celiac axis (CA), common hepatic artery (CHA), and splenic artery (SA) were measured with arterial phase of each CT scan and the ratios of SA to CHA diameter (SA/CHA) calculated to analyze their changes during the follow-up period.

RESULTS

The diameters of celiac axis, CHA, and SA and SA/CHA changed most rapidly during the short-term period. The CHA diameter significantly increased short-term post-SAE by CT and slightly decreased thereafter. However, the mid-term and long-term post-SAE CT values were still significantly greater than those on the pre-SAE CT. The SA diameter steadily decreased throughout the follow-up. The SA/CHA decreased until the mid-term. The SA diameter and SA/CHA were significantly smaller upon mid-term and long-term post-SAE CT compared with those at pre-SAE CT.

CONCLUSIONS

The effect of SAE to improve hepatic arterial flow in OLT recipients with SASS might be expected for at least approximately one year. The effect maximally occurred during the short-term after SAE on the basis of changes in the caliber of related arteries upon CT.