Enhancement of Wound Healing Efficacy by Increasing the Stability and Skin-Penetrating Property of bFGF Using 30Kc19α-Based Fusion Protein

The instability of recombinant basic fibroblast growth factor (bFGF) is a major disadvantage for its therapeutic use and means frequent applications to cells or tissues are required for sustained effects. Originating from silkworm hemolymph, 30Kc19α is a cell-penetrating protein that also has protein stabilization properties. Herein, it is investigated whether fusing 30Kc19α to bFGF can enhance the stability and skin penetration properties of bFGF, which may consequently increase its therapeutic efficacy. The fusion of 30Kc19α to bFGF protein increases protein stability, as confirmed by ELISA. 30Kc19α-bFGF also retains the biological activity of bFGF as it facilitates the migration and proliferation of fibroblasts and angiogenesis of endothelial cells. It is discovered that 30Kc19α can improve the transdermal delivery of a small molecular fluorophore through the skin of hairless mice. Importantly, it increases the accumulation of bFGF and further facilitates its translocation into the skin through follicular routes. Finally, when applied to a skin wound model in vivo, 30Kc19α-bFGF penetrates the dermis layer effectively, which promotes cell proliferation, tissue granulation, angiogenesis, and tissue remodeling. Consequently, the findings suggest that 30Kc19α improves the therapeutic functionalities of bFGF, and would be useful as a protein stabilizer and/or a delivery vehicle in therapeutic applications.

Intracellular Delivery of Recombinant RUNX2 Facilitated by Cell-Penetrating Protein for the Osteogenic Differentiation of hMSCs

Human mesenchymal stem cells (hMSCs) are a commonly used cell source for cell therapy and tissue engineering because of their easy accessibility and multipotency. Runt-related transcription factor 2 (RUNX2) is a master regulator of the osteogenic commitment of hMSCs. Either recombinant plasmid delivery or viral transduction has been utilized to activate RUNX2 gene expression for effective hMSC differentiation. In this study, recombinant RUNX2 fused with cell-penetrating 30Kc19α protein (30Kc19α-RUNX2) was delivered into hMSCs for osteogenic commitment. Fusion of recombinant RUNX2 with 30Kc19α resulted in successful delivery of the protein into cells and enhanced soluble expression of the protein. Intracellular delivery of the 30Kc19α-RUNX2 fusion protein enhanced the osteogenic differentiation of hMSCs in vitro. 30Kc19α-RUNX2 treatment resulted in increased ALP accumulation and elevated calcium deposition. Finally, implantation of hMSCs treated with 30Kc19α-RUNX2 showed osteogenesis via cell delivery into the subcutaneous tissue and bone regeneration in a cranial defect mouse model. Therefore, we suggest that 30Kc19α-RUNX2, an osteoinductive recombinant protein, is an efficient tool for bone tissue engineering.

Facilitated Transdermal Drug Delivery Using Nanocarriers-Embedded Electroconductive Hydrogel Coupled with Reverse Electrodialysis-Driven Iontophoresis

We herein developed an iontophoretic transdermal drug delivery system for the effective delivery of electrically mobile drug nanocarriers (DNs). Our system consists of a portable and disposable reverse electrodialysis (RED) battery that generates electric power for iontophoresis through the ionic exchange. In addition, in order to provide a drug reservoir to the RED-driven iontophoretic system, an electroconductive hydrogel composed of polypyrrole-incorporated poly(vinyl alcohol) (PYP) was used. The PYP hydrogel facilitated electron transfer from the RED battery and accelerated the mobility of electrically mobile DNs released from the PYP hydrogel. In this study, we showed that fluconazole- or rosiglitazone-loaded DNs could be functionalized with charge-inducing agents, and DNs with charge modification resulted in facilitated transdermal transport via repulsive RED-driven iontophoresis. In addition, topical application and RED-driven iontophoresis of rosiglitazone-loaded DNs resulted in an effective antiobese condition displaying decreased bodyweight, reduced glucose level, and increased conversion of white adipose tissues to brown adipose tissues in vivo. Consequently, we highlight that this transdermal drug delivery platform would be extensively utilized for delivering diverse therapeutic agents in a noninvasive way.

Ectopic transient overexpression of OCT-4 facilitates BMP4-induced osteogenic transdifferentiation of human umbilical vein endothelial cells

Limitation in cell sources for autologous cell therapy has been a recent focus in stem cell therapy and tissue engineering. Among various research advances, direct conversion, or transdifferentiation, is a notable and feasible strategy for the generation and acquirement of wanted cell source. So far, utilizing cell transdifferentiation technology in tissue engineering was mainly restricted at achieving single wanted cell type from diverse cell types with high efficiency. However, regeneration of a complete tissue always requires multiple cell types which poses an intrinsic complexity. In this study, enhanced osteogenic differentiation was achieved by transient ectopic expression of octamer-binding transcription factor 4 (OCT-4) gene followed by bone morphogenetic protein 4 treatment on human umbilical vein endothelial cells. OCT-4 transfection and bone morphogenetic protein 4 treatment resulted in enhanced expression of osteogenic markers such as core-binding factor alpha 1, alkaline phosphatase, and collagen 1 compared with bone morphogenetic protein 4 treatment alone. Furthermore, we employed gelatin-heparin cryogel in cranial defect model for in vivo bone formation. Micro-computed tomography and histological analysis of in vivo samples showed that OCT-4 transfection followed by bone morphogenetic protein 4 treatment resulted in efficient transdifferentiation of endothelial cells to osteogenic cells. These results suggest that the combination of OCT-4 and bone morphogenetic protein 4 on endothelial cells would be a reliable multicellular transdifferentiation model which could be applied for bone tissue engineering.

Fabrication of polyphenol-incorporated anti-inflammatory hydrogel via high-affinity enzymatic crosslinking for wet tissue adhesion

Epigallocatechin gallates (EGCGs), isolated from green tea, have intrinsic properties such as anti-oxidant, anti-inflammation, and radical scavenger effects. In this study, we report a tissue adhesive and anti-inflammatory hydrogel formed by high-affinity enzymatic crosslinking of polyphenolic EGCGs. A mixture of EGCG conjugated hyaluronic acids (HA_E) and tyramine conjugated hyaluronic acids (HA_T) was reacted with tyrosinase isolated from Streptomyces avermitillis (SA_Ty) to form that displayed fast enzyme kinetic to form a crosslinked adhesive hydrogel. A 1,2,3-trihydroxyphenyl group in EGCG displayed a high affinity to SA_Ty that allowed HA_E to be quickly oxidized and crosslinked with HA_T to form HA_T and HA_E mixed hydrogel (HA_TE). We then compared the HA_TE hydrogel with commercially available tissue adhesives, such as cyanoacrylate and fibrin glue. We report that the HA_TE exhibited the highest tissue adhesiveness both in wet and dry conditions. Furthermore, HA_TE successfully closed a skin wound and displayed insignificant host tissue responses. This demonstrates that polyphenol-incorporated anti-inflammatory hydrogel may provide a robust tissue adhesive platform for clinical applications.

CRISPR-Cpf1 Activation of Endogenous BMP4 Gene for Osteogenic Differentiation of Umbilical-Cord-Derived Mesenchymal Stem Cells

The CRISPR systems provide powerful genome-editing tools for wide applications in biological and medical research fields. However, the safety issue due to off-target effects of CRISPR has been one of the major hindrances of its application to regenerative medicine. The conventional CRISPR system has the intrinsic danger of inducing unpredictable mutations at non-targeted genomic loci via erroneous double-strand DNA breaks (DSBs). In this study, we demonstrate a safety-enhanced application of a recently discovered CRISPR-Cpf1 for targeted gene activation, without DNA double-strand break, to facilitate osteogenic differentiation of human umbilical-cord-derived mesenchymal stem cells (UC-MSCs). To this end, we developed a catalytically inactive AsCpf1 fused to tripartite transcription activator domain (dAsCpf1-VPR) that can induce upregulation of targeted gene expression in mammalian cells. We observed that the CRISPR-dAsCpf1-VPR activator can be applied to enhance the osteogenic differentiation of human UC-MSCs, via increasing the expression level of endogenous BMP4 gene. The results suggested that the CRISPR-Cpf1 activator provides versatile methods applicable for bone regeneration and regenerative medicine.

Programmable Nuclease-Based Integration into Novel Extragenic Genomic Safe Harbor Identified from Korean Population-Based CNV Analysis

Here, we found two genomic safe harbor (GSH) candidates from chromosomes 3 and 8, based on large-scale population-based cohort data from 4,694 Koreans by CNV analysis. Furthermore, estimated genotype of these CNVRs was validated by quantitative real-time PCR, and epidemiological data examined no significant genetic association between diseases or traits and two CNVRs. After screening the GSH candidates by in silico approaches, we designed TALEN pairs to integrate EGFP expression cassette into human cell lines in order to confirm the functionality of GSH candidates in an in vitro setting. As a result, transgene insertion into one of the two loci using TALEN showed robust transgene expression comparable to that with an AAVS1 site without significantly perturbing neighboring genes. Changing the promoter or cell type did not noticeably disturb this trend. Thus, we could validate two CNVRs as a site for effective and safe transgene insertion in human cells.

Cardiac-mimetic cell-culture system for direct cardiac reprogramming

Rationale: Cardiovascular diseases often cause substantial heart damage and even heart failure due to the limited regenerative capacity of adult cardiomyocytes. The direct cardiac reprogramming of fibroblasts could be a promising therapeutic option for these patients. Although exogenous transcriptional factors can induce direct cardiac reprogramming, the reprogramming efficiency is too low to be used clinically. Herein, we introduce a cardiac-mimetic cell-culture system that resembles the microenvironment in the heart and provides interactions with cardiomyocytes and electrical cues to the cultured fibroblasts for direct cardiac reprogramming. Methods: Nano-thin and nano-porous membranes and heart like electric stimulus were used in the cardiac-mimetic cell-culture system. The human neonatal dermal fibroblasts containing cardiac transcription factors were plated on the membrane and cultured with the murine cardiomyocyte in the presence of the electric stimulus. The reprogramming efficiency was evaluated by qRT-PCR and immunocytochemistry. Results: Nano-thin and nano-porous membranes in the culture system facilitated interactions between fibroblasts and cardiomyocytes in coculture. The cellular interactions and electric stimulation supplied by the culture system dramatically enhanced the cardiac reprogramming efficiency of cardiac-specific transcriptional factor-transfected fibroblasts. Conclusion: The cardiac-mimetic culture system may serve as an effective tool for producing a feasible number of reprogrammed cardiomyocytes from fibroblasts.

Dual-Channel Fluorescence Imaging of Hydrogel Degradation and Tissue Regeneration in the Brain

The ability of brain tissue to regenerate is limited; therefore, brain diseases (i.e., trauma, stroke, tumors) often lead to irreversible motor and cognitive impairments. Therapeutic interventions using various types of injectable biomaterials have been investigated to promote endogenous neural differentiation. Despite promising results in pre-clinical studies, the translation of regenerative medicine to the clinic has many challenges due to the lack of reliable imaging systems to achieve accurate evaluation of the treatment efficacy.

Methods: In this study, we developed a dual-channel fluorescence imaging technique to simultaneously monitor tissue ingrowth and scaffold disintegration. Enzymatically crosslinked gelatin-hyaluronic acid hydrogel was labeled with 800 nm fluorophore, ZW800-3a, while the regenerated tissue was highlighted with 700 nm brain-specific contrast agent, Ox1.

Results: Using the multichannel fluorescence imaging system, tissue growth and degradation of the NIR hydrogel were simultaneously imaged in the brain of mice. Images were further analyzed and reconstructed to show both visual and quantitative information of each stage of a therapeutic period.

Conclusion: Dual-channel in vivo imaging systems can provide highly accurate visual and quantitative information of the brain tissue ingrowth for the evaluation of the therapeutic effect of NIR hydrogel through a simple and fast operating procedure.

Lysosome-Targeted Bioprobes for Sequential Cell Tracking from Macroscopic to Microscopic Scales

Longitudinal tracking of living cells is crucial to understanding the mechanism of action and toxicity of cell-based therapeutics. To quantify the presence of administered cells in the host tissue without sacrifice of animals, labeling of the target cells with a nontoxic and stable contrast agent is a prerequisite. However, such long-term live cell tracking is currently limited by the lack of fluorophores with steady optical and physicochemical properties in the near-infrared (NIR) window. Herein, for the first time, the design of fixable cell-tracking NIR fluorophores (CTNFs) with high optical properties, excellent cell permeation and retention, and high stability against chemical treatments is reported. Efficient cellular labeling and tracking of CTNFs using intraoperative optical fluorescence imaging by following the fate of NIR-labeled cells from the time of injection into animals to ex vivo cellular analysis after resection of the target tissue is demonstrated. Due to the lipophilic cationicity and primary amine docking group, CTNF126 outperforms the other tested fluorophores with rapid diffusion into the cytoplasmic membrane and sequestration inside the lysosomes, which prevents cellular efflux and improves cellular retention. Thus, CTNF126 will be useful to track cells in living organisms for the mechanism of action at the single cell level.

Osteogenic Effects of VEGF-Overexpressed Human Adipose-Derived Stem Cells with Whitlockite Reinforced Cryogel for Bone Regeneration

Bone is a vascularized tissue that is comprised of collagen fibers and calcium phosphate crystals such as hydroxyapatite (HAp) and whitlockite (WH). HAp and WH are known to elicit bone regeneration by stimulating osteoblast activities and osteogenic commitment of stem cells. In addition, vascular endothelial growth factor (VEGF) is shown to promote osteogenesis and angiogenesis which is considered as an essential process in bone repair by providing nutrients. In this study, VEGF-secreting human adipose-derived stem cells (VEGF-ADSCs) are developed by transducing ADSCs with VEGF-encoded lentivirus. Additionally, WH-reinforced gelatin/heparin cryogels (WH-C) are fabricated by loading WH into gelatin/heparin cryogels. VEGF-ADSC secrete tenfold more VEGF than ADSC and show increased VEGF secretion with cell growth. Also, incorporation of WH into cryogels provides a mineralized environment with ions secreted from WH. When the VEGF-ADSCs are seeded on WH-C, sustained release of VEGF is observed due to the specific affinity of VEGF to heparin. Finally, the synergistic effect of VEGF-ADSC and WH on osteogenesis is successfully confirmed by alkaline phosphatase and real-time polymerase chain reaction analysis. In vivo bone formation is demonstrated via implantation of VEGF-ADSC seeded WH-C into mouse calvarial bone defect model, resulted in enhanced bone development with the highest bone volume/total volume.

A biofunctionalized viral delivery patch for spatially defined transfection

Gene therapy holds the significance of correcting genetic defects. However, difficulties in the in vivo delivery to the targeted tissues and systemic delivery remain the biggest challenges to be overcome. Here, a robust system of biofunctionalized polymeric layer-mediated lentiviral delivery was designed for the site-specific spatial and temporal control of viral gene delivery. Poly glycidyl methacrylate (pGMA) modification of a substrate via initiated chemical vapor deposition (iCVD) followed by polyethyleneimine (PEI) immobilization provided the adhesion site for the lentivirus. Furthermore, the polymeric patch based gene delivery system showed a high rate of gene transduction compared to bolus treatment. Furthermore, by using mask patterning, we were able to spatially pattern the lentivirus which allowed spatially defined transfection.

Magnetic Nanoparticle-Embedded Hydrogel Sheet with a Groove Pattern for Wound Healing Application

Endothelial progenitor cells (EPCs) can induce a pro-angiogenic response during tissue repair. Recently, EPC transplantations have been widely investigated in wound healing applications. To maximize the healing efficacy by EPCs, a unique scaffold design that allows cell retention and function would be desirable for in situ delivery. Herein, we fabricated an alginate/poly-l-ornithine/gelatin (alginate-PLO-gelatin) hydrogel sheet with a groove pattern for use as a cell delivery platform. In addition, we demonstrate the topographical modification of the hydrogel sheet surface with a groove pattern to modulate cell proliferation, alignment, and elongation. We report that the patterned substrate prompted morphological changes of endothelial cells, increased cell-cell interaction, and resulted in the active secretion of growth factors such as PDGF-BB. Additionally, we incorporated magnetic nanoparticles (MNPs) into the patterned hydrogel sheet for the magnetic field-induced transfer of cell-seeded hydrogel sheets. As a result, enhanced wound healing was observed via efficient transplantation of the EPCs with an MNP-embedded patterned hydrogel sheet (MPS). Finally, enhanced vascularization and dermal wound repair were observed with EPC seeded MPS.

Recent Advances in Engineered Stem Cell-Derived Cell Sheets for Tissue Regeneration

The substantial progress made in the field of stem cell-based therapy has shown its significant potential applications for the regeneration of defective tissues and organs. Although previous studies have yielded promising results, several limitations remain and should be overcome for translating stem cell-based therapies to clinics. As a possible solution to current bottlenecks, cell sheet engineering (CSE) is an efficient scaffold-free method for harvesting intact cell sheets without the use of proteolytic enzymes, and may be able to accelerate the adoption of stem cell-based treatments for damaged tissues and organs regeneration. CSE uses a temperature-responsive polymer-immobilized surface to form unique, scaffold-free cell sheets composed of one or more cell layers maintained with important intercellular junctions, cell-secreted extracellular matrices, and other important cell surface proteins, which can be achieved by changing the surrounding temperature. These three-dimensional cell sheet-based tissues can be designed for use in clinical applications to target-specific tissue regeneration. This review will highlight the principles, progress, and clinical relevance of current approaches in the cell sheet-based technology, focusing on stem cell-based therapies for bone, periodontal, skin, and vascularized muscles.

Bioactive calcium phosphate materials and applications in bone regeneration

BACKGROUND

Bone regeneration involves various complex biological processes. Many experiments have been performed using biomaterials in vivo and in vitro to promote and understand bone regeneration. Among the many biomaterials, calcium phosphates which exist in the natural bone have been conducted a number of studies because of its bone regenerative property. It can be directly contributed to bone regeneration process or assist in the use of other biomaterials. Therefore, it is widely used in many applications and has been continuously studied.

MAINBODY

Calcium phosphate has been widely used in bone regeneration applications because it shows osteoconductive and in some cases osteoinductive features. The release of calcium and phosphorus ions regulates the activation of osteoblasts and osteoclasts to facilitate bone regeneration. The control of surface properties and porosity of calcium phosphate affects cell/protein adhesion and growth and regulates bone mineral formation. Properties affecting bioactivity vary depending on the types of calcium phosphates such as HAP, TCP and can be utilized in various applications because of differences in ion release, solubility, stability, and mechanical strength. In order to make use of these properties, different calcium phosphates have been used together or mixed with other materials to complement their disadvantages and to highlight their advantages. Calcium phosphate has been utilized to improve bone regeneration in ways such as increasing osteoconductivity for bone ingrowth, enhancing osteoinductivity for bone mineralization with ion release control, and encapsulating drugs or growth factors.

CONCLUSION

Calcium phosphate has been used for bone regeneration in various forms such as coating, cement and scaffold based on its unique bioactive properties and bone regeneration effectiveness. Additionally, several studies have been actively carried out to improve the efficacy of calcium phosphate in combination with various healing agents. By summarizing the properties of calcium phosphate and its research direction, we hope that calcium phosphate can contribute to the clinical treatment approach for bone defect and disease.

Injectable angiogenic and osteogenic carrageenan nanocomposite hydrogel for bone tissue engineering

Functional biomaterials that couple angiogenesis and osteogenesis processes are vital for bone tissue engineering and bone remodeling. Herein we developed an injectable carrageenan nanocomposite hydrogel incorporated with whitlockite nanoparticles and an angiogenic drug, dimethyloxallylglycine. Synthesized whitlockite nanoparticles and nanocomposite hydrogels were characterized using SEM, TEM, EDS and FTIR. Developed hydrogels were injectable, mechanically stable, cytocompatible and has better protein adsorption. Incorporation of dimethyloxallylglycine resulted in initial burst release followed by sustained release for 7 days. Human umbilical vein endothelial cells exposed to dimethyloxallylglycine incorporated nanocomposite hydrogel showed enhanced cell migration and capillary tube-like structure formation. Osteogenic differentiation in rat adipose derived mesenchymal stem cells after 7 and 14 days revealed increased levels of alkaline phosphatase activity in vitro. Furthermore, cells exposed to nanocomposite hydrogel revealed enhanced protein expressions of RUNX2, COL and OPN. Overall, these results suggest that incorporation of whitlockite and dimethyloxallylglycine in carrageenan hydrogel promoted osteogenesis and angiogenesis in vitro.

Mild Reduction of the Cancer Cell Surface as an Anti-invasion Treatment

Cancer cell invasion is the main reason for high mortality in patients with malignant cancers. There has been little improvement in cancer prognosis because of a high rate of infiltration. Therefore, successful treatment requires inhibition of cancer cell invasion. Here, we suggest a new approach to inhibit cancer cell invasion through mild reduction of cell surface proteins to expose free thiols. Through mild reduction, the cancer cell surfaces present free active thiols at the membranes, enhancing cell adhesion to extracellular matrix and decreasing motility. Collectively, we suggest cell surface modification as a new therapeutic approach to treat invading malignant cancers.

Bioglass-Incorporated Methacrylated Gelatin Cryogel for Regeneration of Bone Defects

Cryogels have recently gained interest in the field of tissue engineering as they inherently possess an interconnected macroporous structure. Considered to be suitable for scaffold cryogel fabrication, methacrylated gelatin (GelMA) is a modified form of gelatin valued for its ability to retain cell adhesion site. Bioglass nanoparticles have also attracted attention in the field due to their osteoinductive and osteoconductive behavior. Here, we prepare methacrylated gelatin cryogel with varying concentration of bioglass nanoparticles to study its potential for bone regeneration. We demonstrate that an increase in bioglass concentration in cryogel leads to improved mechanical property and augmented osteogenic differentiation of mesenchymal cells during in vitro testing. Furthermore, in vivo testing in mice cranial defect model shows that highest concentration of bioglass nanoparticles (2.5 w/w %) incorporated in GelMA cryogel induces the most bone formation compared to the other tested groups, as studied by micro-CT and histology. The in vitro and in vivo results highlight the potential of bioglass nanoparticles incorporated in GelMA cryogel for bone regeneration.

Heparin Functionalized Injectable Cryogel with Rapid Shape-Recovery Property for Neovascularization

Cryogel based scaffolds have high porosity with interconnected macropores that may provide cell compatible microenvironment. In addition, cryogel based scaffolds can be utilized in minimally invasive surgery due to its sponge-like properties, including rapid shape recovery and injectability. Herein, we developed an injectable cryogel by conjugating heparin to gelatin as a carrier for vascular endothelial growth factor (VEGF) and fibroblasts in hindlimb ischemic disease. Our gelatin/heparin cryogel showed gelatin concentration-dependent mechanical properties, swelling ratios, interconnected porosities, and elasticities. In addition, controlled release of VEGF led to effective angiogenic responses both in vitro and in vivo. Furthermore, its sponge-like properties enabled cryogels to be applied as an injectable carrier system for in vivo cells and growth factor delivery. Our heparin functionalized injectable cryogel facilitated the angiogenic potential by facilitating neovascularization in a hindlimb ischemia model.

Tissue adhesive, rapid forming, and sprayable ECM hydrogel via recombinant tyrosinase crosslinking

We report on a tissue adhesive hydrogel based on novel recombinant tyrosinase mediated crosslinking. The adhesive hydrogels were fabricated by the site-directed coupling of tyramine-conjugated hyaluronic acid (HA_t, 1% w/v) and gelatin (3% w/v) (HG_gel) with novel tyrosinase derived from Streptomyces avermitilis (SA_Ty). The enzyme-based crosslinking by SA_Ty was fast, with less than 50 s for complete gelation, and the SA_Ty based crosslinking enhanced the physical properties and adhesive strength of the hydrogel significantly with the native tissue samples. Furthermore, by optimizing the injection conditions, we tailored the enzyme-based crosslinking hydrogels to be injectable and sprayable with a medical syringe and commercial airbrush nozzle, respectively. An in vivo analysis of the adhesive hydrogel showed a negligible immune reaction. In this study, demonstrate that the novel enzyme-based crosslinking hydrogel has a robust potential in tissue engineering and regenerative medicine.