Cell Delivery Vehicle Research Articles

Repair of the injured spinal cord by transplantation of neural stem cells in a hyaluronan-based hydrogel

Traumatic injury to the spinal cord causes cell death, demyelination, axonal degeneration, and cavitation resulting in functional motor and sensory loss. Stem cell therapy is a promising approach for spinal cord injury (SCI); however, this strategy is currently limited by the poor survival and uncontrolled differentiation of transplanted stem cells. In an attempt to achieve greater survival and integration with the host tissue, we examined the survival and efficacy of adult brain-derived neural stem/progenitor cells (NSPCs) injected within a hydrogel blend of hyaluronan and methyl cellulose (HAMC) into a subacute, clinically relevant model of rat SCI. Prior to use, HAMC was covalently modified with recombinant rat platelet-derived growth factor-A (rPDGF-A) to promote oligodendrocytic differentiation. SCI rats transplanted with NSPCs in HAMC-rPDGF-A showed improved behavioral recovery compared to rats transplanted with NSPCs in media. Rats with NSPC/HAMC-rPDGF-A transplants had a significant reduction in cavitation, improved graft survival, increased oligodendrocytic differentiation, and sparing of perilesional host oligodendrocytes and neurons. These data suggest that HAMC-rPDGF-A is a promising vehicle for cell delivery to the injured spinal cord.

Functionalized self-assembling peptide nanofiber hydrogels mimic stem cell niche to control human adipose stem cell behavior in vitro

A class of designer functionalized self-assembling peptide nanofiber scaffolds developed from self-assembling peptide RADA16-I (AcN-RADARADARADARADA-CONH2) has become increasingly attractive not only for studying spatial behaviors of cells, but also for developing approaches for a wide range of medical applications including regenerative medicine, rapid hemostasis and cell therapy. In this study, we report three functionalized self-assembling peptide hydrogels that serve as a three-dimensional (3-D) artificial microenvironment to control human adipose stem cell (hASC) behavior in vitro. Short peptide motifs SKPPGTSS (bone marrow homing motif), FHRRIKA (heparin-binding motif) and PRGDSGYRGDS (two-unit RGD cell adhesion motif) were used to extend the C-terminus of RADA16-I to obtain functionalized peptides. Atomic force microscopy confirmed the formation of self-assembling nanofibers in the mixture of RADA16-I peptide and functionalized peptides. The behaviors of hASCs cultured in 3-D peptide hydrogels, including migration, proliferation and growth factor-secretion ability, were studied. Our results showed that the functionalized peptide hydrogels were suitable 3-D scaffolds for hASC growth with higher cell proliferation, migration and the secretion of angiogenic growth factors compared with tissue culture plates and pure RADA16-I scaffolds. The present study suggests that these functionalized designer peptide hydrogels not only have promising applications for diverse tissue engineering and regenerative medicine applications as stem cell delivery vehicles, but also could be a biomimetic 3-D system to study nanobiomaterial–stem cell interactions and to direct stem cell behaviors.

Enzymatically cross-linked alginic–hyaluronic acid composite hydrogels as cell delivery vehicles

An injectable composite gel was developed from alginic and hyaluronic acid. The enzymatically cross-linked injectable gels were prepared via the oxidative coupling of tyramine modified sodium algiante and sodium hyaluronate in the presence of horse radish peroxidase (HRP) and hydrogen peroxide (H2O2). The composite gels were prepared by mixing equal parts of the two tyraminated polymer solutions in 10U HRP and treating with 1.0% H2O2. The properties of the alginate gels were significantly affected by the addition of hyaluronic acid. The percentage water absorption and storage modulus of the composite gels were found to be lower than the alginate gels. The alginate and composite gels showed lower protein release compared to hyaluronate gels in the absence of hyaluronidase. Even hyaluronate gels showed only approximately 10% protein release after 14 days incubation in phosphate buffer solution. ATDC-5 cells encapsulated in the injectable gels showed high cell viability. The composite gels showed the presence of enlarged spherical cells with significantly higher metabolic activity compared to cells in hyaluronic and alginic acid gels. The results suggest the potential of the composite approach to develop covalently cross-linked hydrogels with tuneable physical, mechanical, and biological properties.

Periadventitial human stem cell treatment reduces vein graft intimal thickening in pig vein-into-artery interposition grafts

BackgroundNeointima formation and atherosclerosis compromise long-term graft patency in aortocoronary vein bypass grafts. We investigated the effect on neointima formation in porcine saphenous vein grafts of periadventitial application of immortalized human mesenchymal stem cells transduced with the gene for the peptide glucagon-like peptide-1, which have been shown to induce angiogenesis in previous studies and are protected from immune-mediated destruction by encapsulation in alginate microbeads (CellBeads). Methods and resultsPeriadventitial application of CellBeads was compared with alginate beads only or vehicle control in pig vein-into-artery interposition grafts. CellBeads significantly reduced neointimal area and total wall area compared with both control groups. This was associated with a significant increase in vein graft adventitial neoangiogenesis. CellBeads had no effect on vessel inward or outward remodeling and promoted adventitial collagen deposition. Alginate beads without stem cells reduced graft patency (6/15 grafts patent) versus CellBead-treated (6/7 grafts patent) or untreated grafts (7/8 grafts patent) (Fisher exact test, P = 0.052). There was no evidence of an inflammatory or cellular immune reaction to either the CellBeads or the alginate-only beads. ConclusionsPeriadventitial treatment of porcine vein grafts with human stem cells inhibits neointima formation in association with accelerated adventitial angiogenesis. The alginate vehicle alone appeared to promote graft failure and is therefore not the optimal vehicle for stem cell delivery to vein grafts.

Inducible regulation of GDNF expression in human neural stem cells

Glial cell derived neurotrophic factor (GDNF) holds promises for treating neurodegenerative diseases such as Parkinson's disease. Human neural stem cells (hNSCs) have proved to be a suitable cell delivery vehicle for the safe and efficient introduction of GDNF into the brain. In this study, we used hNSCs-infected with a lentivirus encoding GDNF and the hygromycin resistance gene as such vehicles. A modified tetracycline operator 7 (tetO7) was inserted into a region upstream of the EF1-α promoter to drive GDNF expression. After hygromycin selection, hNSCs were infected with a lentivirus encoding a KRAB-tetracycline repressor fusion protein (TTS). TTS bound to tetO7 and suppressed the expression of GDNF in hNSCs. Upon administration of doxycycline (Dox) the TTS-tetO7 complex separated and the expression of GDNF resumed. The hNSCs infected with GDNF expressed the neural stem cell specific markers, nestin and sox2, and exhibited no significant change in proliferation rate. However, the rate of apoptosis in hNSCs expressing GDNF was lower compared with normal NSCs in response to actinomycin treatment. Furthermore, a higher percentage of Tuj-1 positive cells were obtained from GDNF-producing NSCs under conditions that induced differentiation compared to control NSCs. The inducible expression of GDNF in hNSCs may provide a system for the controllable delivery of GDNF in patients with neurodegenerative diseases.

PLGA 다공성 지지체에 함침시킨 DBP젤의 연골재생 효과: In Vivo 실험

생체적합성 및 생분해성의 장점을 지닌 PLGA는 우수한 기계적 성질과 분해속도를 조절할 수 있는 장점을 가지고 있지만 소수성으로 인해 세포의 초기부착률이 낮고, 지지체 내부에 영양액의 공급이 원활하지 않다. 본 연구에서는 이러한 단점을 보완하고자 탈미네랄화된 골분(DBP, demineralized bone particle) 젤을 PLGA 지지체에 함침시켰다. 다양한 형태의 지지체 압축강도를 측정한 결과 PLGA/DBP 지지체가 연골과 비슷한 강도를 가지고 있었으며, 이를 바탕으로 DBP젤을 함침시킨 PLGA/DBP젤 지지체를 제작하였다. 연골세포를 파종하여 in vivo 실험을 진행하였고 조직화 정도를 확인하기 위해 H&E, Safranin-O, Alcian blue, Collagen type I 및 Collagen type II 염색을 실시하였다. 그 결과 DBP를 함침시킨 PLGA 지지체에서 GAG, Collagen type I 및 Collagen type II의 높은 발현과 조직화를 보여 연골조직으로 대체할 수 있는 가능성을 확인하였다. Poly(lactic-co-glycolic acid) (PLGA) has been most widely used due to its advantages such as good biodegradability, controllable rate of degradation and metabolizable degradation products. We manufactured composite scaffolds of PLGA scaffold penetrated DBP gel (PLGA/DBP gel) by a simple method, solvent casting/salt leaching prep of PLGA scaffolds and subsequent soaking in DBP gel. Chondrocytes were seeded on the PLGA/DBP gel. The mechanical strength of scaffold, histology (H&E, Safranin-O, Alcian-blue) and immunohistochemistry (collagen type I, collagen type II) were performed to elucidate in vitro and in vivo cartilage-specific extracellular matrices. It was better to keep the characteristic of chondrocytes in the PLGA/DBP gel scaffolds than that PLGA scaffolds. This study suggests that PLGA/DBP gel scaffold may serve as a potential cell delivery vehicle and a structural basis for in vivo tissue engineered cartilage.

Characterization of hyaluronan–methylcellulose hydrogels for cell delivery to the injured spinal cord

No effective clinical treatment currently exists for traumatic spinal cord injury. Cell replacement therapy holds promise for attaining functional repair. Cells may be delivered directly or near the injury site; however, this strategy requires a delivery vehicle to maintain cell viability. We have identified an injectable, biocompatible, and biodegradable hydrogel scaffold composed of hyaluronan (HA) and methylcellulose (MC) that may be an effective scaffold for therapeutic cell delivery. The purpose of the present study was to determine the effects of polymer concentration on HAMC mechanical strength, gelation time, and cell viability. The yield stress of HAMC, a measure of mechanical stiffness, was tunable via manipulation of MC and HA content. Measurement of the elastic and storage moduli as functions of time revealed that HAMC gels in less than 5 min at physiological temperatures. Human umbilical tissue-derived cells encapsulated in HAMC were homogenously and stably distributed over 3 days in culture and extended processes into the scaffold. Cell viability was stable over this period in all but the most concentrated HAMC formulation. Because of its strength-tunability, rapid gelation, and ability to maintain cell viability, HAMC is a promising vehicle for cell delivery and is being tested in ongoing in vivo studies.

Cardiac Tissue Engineering: Principles, Materials, and Applications

Cardiac tissue engineering aims at repairing damaged heart muscle and producing human cardiac tissues for application in drug toxicity studies. This book offers a comprehensive overview of the cardiac tissue engineering strategies, including presenting and discussing the various concepts in use, research directions and applications. Essential basic information on the major components in cardiac tissue engineering, namely cell sources and biomaterials, is firstly presented to the readers, followed by a detailed description of their implementation in different strategies, broadly divided to cellular and acellular ones. In cellular approaches, the biomaterials are used to increase cell retention after implantation or as scaffolds when bioengineering the cardiac patch, in vitro. In acellular approaches, the biomaterials are used as ECM replacement for damaged cardiac ECM after MI, or, in combination with growth factors, the biomaterials assume an additional function as a depot for prolong d factor activity for the effective recruitment of repairing cells. The book also presents technological innovations aimed to improve the quality of the cardiac patches, such as bioreactor applications, stimulation patterns and prevascularization. This book could be of interest not only from an educational perspective (i.e. for graduate students), but also for researchers and medical professionals, to offer them fresh views on novel and powerful treatment strategies. We hope that the reader will find a broad spectrum of ideas and possibilities described in this book both interesting and convincing. Table of Contents: Introduction / The Heart: Structure, Cardiovascular Diseases, and Regeneration / Cell Sources for Cardiac Tissue Engineering / Biomaterials: Polymers, Scaffolds, and Basic Design Criteria / Biomaterials as Vehicles for Stem Cell Delivery and Retention in the Infarct / Bioengineering of Cardiac Patches, In Vitro / Perfusion Bioreactors and Stimulation Patterns in Cardiac T ssue Engineering / Vascularization of Cardiac Patches / Acellular Biomaterials for Cardiac Repair / Biomaterial-based Controlled Delivery of Bioactive Molecules for Myocardial Regeneration

Protein‐Engineered Injectable Hydrogel to Improve Retention of Transplanted Adipose‐Derived Stem Cells

Improved retention of transplanted stem cells is achieved through minimally invasive delivery in MITCH, a mixing-induced two-component hydrogel that was engineered to possess shear-thinning and self-healing thixotropic properties. MITCH, an ideal injectable cell-delivery vehicle, supports 3D stem-cell culture, resulting in high cell viability and physiologically relevant cell morphology.

Abstract 344: Naturally Derived Cardiac Extracellular Matrix for Cardiac Progenitor Cell Therapy

Cardiovascular disease is the leading cause of death in the United States. Following acute myocardial infarction, there is dramatic myocyte loss, and the cells are replaced with a collagen scar. Cell therapy directed toward regenerating infarcted myocardium suffers from poor retention of cells, possibly because the conditions are not ideal to support injected cells. Many studies show the local microenvironment is a potent regulator of cell fate. Therefore, we hypothesize that culturing cardiac progenitor cells (CPCs) on a naturally derived, cardiac extracellular matrix (cECM) will increase their function. CPCs were isolated from rat cardiac tissue-homogenate with magnetic beads conjugated with c-kit antibodies. Porcine, cardiac extracellular matrix (cECM) was decellularized, digested, and lyophillized to be used as a coating material. CPCs were cultured on cECM and examined for cardiogenic lineage markers, survival, proliferation and adherence. Our results show that CPCs cultured on cECM proliferate better (2.9-fold) as compared to COL (2.3-fold; p<0.05). Additionally, CPCs demonstrate improved resistance to serum-starvation-induced apoptosis when cultured on cECM (40% ± 14%) as compared to COL (53% ± 14%; p<0.001). Furthermore, CPCs adhered more strongly to cECM than COL as measured using microfluidics. CPCs showed enhanced progression toward the cardiomyoctye lineage when cultured on cECM (nkx2.5: 2.3 ± 0.4-fold; α-myosin heavy chain: 14.6 ± 4.4-fold; troponinC: 2.4 ± 0.2-fold; p-values <0.05) as compared to COL. This was confirmed at the protein level with Gata-4 (1.8 ± 0.1-fold; p<0.001) and Nkx2.5 (1.6 ± 0.2-fold; p<0.05). A reduction in fibroblast specific protein-1 (0.5 ± 0.1-fold) was also seen on cECM as compared to COL and suggests the CPCs are less likely to contribute to scar formation. While these conditioned cells have not yet been examined in an in vivo setting, our comparison to COL mimics both the naked injection of these cells into an infarct zone, and comparison to a commonly used cell delivery vehicle. Our data suggest that CPCs delivered with cECM are more likely to survive and differentiate in the infarct zone than cells delivered by themselves or in collagen.

Effect of demineralized bone particles (DBP) on cell growth and ECM secretion in PLGA/DBP hybrid scaffold for cartilage tissue engineering

In this study, we investigated the effect of deminerized bone particles (DBP) on the regeneration of chondrocyte in poly(lactic-co-glycolic acid) (PLGA)/DBP hybrid scaffolds. PLGA/DBP hybrid scaffolds were designed by varying the DBP content with 0, 10, 20, 40, and 80 w/t% and manufactured by a solvent casting/saltleaching method. We evaluated the potential of PLGA/DBP hybrid scaffolds for cartilage regeneration. Chondrocytes of New Zealand white rabbits were seeded on PLGA/DBP hybrid scaffolds. MTT assay, glycosaminoglycan (GAG) assay, Hematoxylin-Eosin (H&E) staining, Safrainin-O staining, and reverse transcription polymerase chain reaction (RT-PCR) were performed to confirm the effect of the DBP on cell proliferation and extracellular matrix (ECM) production. As the DBP content of these scaffolds became higher, the rate of cell growth and the amount of GAG increased. The PLGA/DBP hybrid scaffolds with DBP content showed better cell proliferation, stable in vitro tissue morphology, superior cartilaginous tissue formation, and sGAG production. In conclusion, PLGA/DBP hybrid scaffolds promote the potential cell delivery vehicle and act as the structural basis for cartilage tissue engineering. Open image in new window

Induction of antigen-specific immune responses in mice by recombinant baculovirus expressing premembrane and envelope proteins of West Nile virus

BackgroundWest Nile Virus (WNV) is an emerging arthropod-born flavivirus with increasing distribution worldwide that is responsible for a large proportion of viral encephalitis in humans and horses. Given that there are no effective antiviral drugs available for treatment of the disease, efforts have been directed to develop vaccines to prevent WNV infection. Recently baculovirus has emerged as a novel and attractive gene delivery vehicle for mammalian cells.ResultsIn the present study, recombinant baculoviruses expressing WNV premembrane (prM) and envelope (E) proteins under the cytomegalovirus (CMV) promoter with or without vesicular stomatitis virus glycoprotein (VSV/G) were constructed. The recombinant baculoviruses designated Bac-G-prM/E and Bac-prM/E, efficiently express E protein in mammalian cells. Intramuscular injection of the two recombinant baculoviruses (at doses of 108 or 109 PFU/mouse) induced the production of WNV-specific antibodies, neutralizing antibodies as well as gamma interferon (IFN-γ) in a dose-dependent pattern. Interestingly, the recombinant baculovirus Bac-G-prM/E was found to be a more efficient immunogen than Bac-prM/E to elicit a robust immune response upon intramuscular injection. In addition, inoculation of baculovirus resulted in the secretion of inflammatory cytokines, such as TNF-α, IL-2 and IL-6.ConclusionsThese recombinant baculoviruses are capable of eliciting robust humoral and cellular immune responses in mice, and may be considered as novel vaccine candidates for West Nile Virus.

SOX9 gene plus heparinized TGF-β 3 coated dexamethasone loaded PLGA microspheres for inducement of chondrogenesis of hMSCs

Microparticulated types of scaffolds have been widely applied in stem cell therapy and the tissue engineering field for the regeneration of wound tissues. During application of simple genes or growth factors and cell delivery vehicles, we designed a method that employs dexamethsone loaded PLGA microspheres consisting of polyplexed SOX9 genes plus heparinized TGF-β 3 on the surface of polymeric microspheres prepared using a layer-by-layer (LbL) method. The fabrication of the polyplexed SOX9 genes plus heparinized TGF-β 3 and their subsequent coating onto dexamethsone loaded PLGA microspheres represents a method for functionalization of the polymeric matrix. The use of SOX9 gene plus heparinized TGF-β 3 coated dexamethsone loaded PLGA microspheres was evaluated to determine their potential as both gene carriers and cell delivery vehicle. By adhesion of hMSCs onto SOX9 gene plus heparinized TGF-β 3 coated dexamethsone loaded PLGA microspheres, the chondrogenesis-related specific genes of collagen type II were increased 30 times comparing to control. Also, the specific extracellular matrix of glycosaminoglycan (GAG) production of hMSCs adhered onto SOX9 gene plus heparinized TGF-β 3 coated dexamethasone loaded PLGA microspheres increased more 2.5 times than control group. Not only in vitro culture but in vivo results, the specific genes of COMP, aggrecan, collagen type II, and SOX9 showed much more gene expressions such as 20, 15, 10, 8 times.

The translational imperative: Making cell therapy simple and effective

The current practice of cell therapy, in which multipotent or terminally differentiated cells are injected into tissues or intravenously, is inefficient. Few therapeutic cells are retained at the site of administration and engraftment is low. An injectable and biologically appropriate vehicle for delivery, retention, growth and differentiation of therapeutic cells is needed to improve the efficacy of cell therapy. We focus on a hyaluronan-based semi-synthetic extracellular matrix (sECM), HyStem®, which is a manufacturable, approvable and affordable clinical product. The composition of this sECM can be customized for use with mesenchymal stem cells as well as cells derived from embryonic or induced pluripotent sources. In addition, it can support therapeutic uses of progenitor and mature cell populations obtained from skin, fat, liver, heart, muscle, bone, cartilage, nerves and other tissues. This overview presents four pre-clinical uses of HyStem® for cell therapy to repair injured vocal folds, improve post-myocardial infarct heart function, regenerate damaged liver tissue and restore brain function following ischemic stroke. Finally, we address the real-world limitations – manufacture, regulation, market acceptance and financing – surrounding cell therapy and the development of clinical combination products.

Enzymatically cross-linked injectable gelatin gel as osteoblast delivery vehicle

Injectable and degradable hydrogels are potential candidates as cell delivery vehicles for the regeneration of osseous defects. We evaluated the potential of injectable enzymatically cross-linked gelatin gel as an osteoblast delivery vehicle using murine preosteoblast MC3T3-E1 cells. Injectable hydrogels were prepared by enzymatic cross-linking of the phenol derivatives of gelatin (tyramine-modified) in the presence of hydrogen peroxide (H2O2) and horseradish peroxidase. The effect of gelatin concentration on gel morphology and in supporting the adhesion and spreading of encapsulated MC3T3-E1 cells, activation of intercellular signaling in MC3T3-E1 cells by extracellular signal-regulated kinase phosphorylation, β-catenin and Runx2 was evaluated. Both tyramine-modified and unmodified gelatins as well as gelatin gels did not activate intercellular signaling pathways in MC3T3-E1 cells. The encapsulated cells in gelatin gel showed extracellular signal-regulated kinase phosphorylation and active β-catenin expression in the presence of inductive molecules such as insulin and LiCl. The gelatin gels formed from 10 to 25 mg/mL tyramine-modified gelatin supported the adhesion, spreading, and three-dimensional growth of MC3T3-E1 cells. However, the lack of activation of intercellular signaling in the gelatin gel indicates the need to add exogenous bioactive molecules to modulate the osteogenic functions of the encapsulated cells.

Optimal poly(L-lysine) grafting density in hydrogels for promoting neural progenitor cell functions.

Recently, we have developed a photopolymerizable poly(L-lysine) (PLL) that can be covalently incorporated into poly(ethylene glycol) diacrylate (PEGDA) hydrogels to improve their bioactivity by providing positive charges. To explore the potential of these PLL-grafted PEGDA hydrogels as a cell delivery vehicle and luminal filler in nerve guidance conduits for peripheral and central nerve regeneration, we varied the number of pendent PLL chains in the hydrogels by photo-cross-linking PEGDA with weight compositions of PLL (φ(PLL)) of 0, 1, 2, 3, and 5%. We further investigated the effect of PLL grafting density on E14 mouse neural progenitor cell (NPC) behavior including cell viability, attachment, proliferation, differentiation, and gene expression. The amount of actually grafted PLL and charge densities were characterized, showing a proportional increase with the feed composition φ(PLL). NPC viability in 3D hydrogels was significantly improved in a PLL grafting density-dependent manner at days 7 and 14 postencapsulation. Similarly, NPC attachment and proliferation were promoted on the PLL-grafted hydrogels with increasing φ(PLL) up to 2%. More intriguingly, NPC lineage commitment was dramatically altered by the amount of grafted PLL chains in the hydrogels. NPC differentiation demonstrated a parabolic or nonmonotonic dependence on φ(PLL), resulting in cells mostly differentiated toward mature neurons with extensive neurite formation and astrocytes rather than oligodendrocytes on the PLL-grafted hydrogels with φ(PLL) of 2%, whereas the neutral hydrogels and PLL-grafted hydrogels with higher φ(PLL) of 5% support NPC differentiation less. Gene expression of lineage markers further illustrated this trend, indicating that PLL-grafted hydrogels with an optimal φ(PLL) of 2% could be a promising cell carrier that promoted NPC functions for treatment of nerve injuries.

Fibrin glue as the cell-delivery vehicle for mesenchymal stromal cells in regenerative medicine

The use of tissue-engineering techniques such as stem-cell therapy to renew injured tissues is a promising strategy in regenerative medicine. As a cell-delivery vehicle, fibrin glues (FG) facilitate cell attachment, growth and differentiation and, ultimately, tissue formation and organization by its three-dimensional structure. Numerous studies have provided evidence that stromal cells derived from bone marrow (bone marrow stromal cells; BMSC) and adipose tissue (adipose-derived stromal cells; ADSC) contain a population of adult multipotent mesenchymal stromal cells (MSC) and endothelial progenitor cells that can differentiate into several lineages. By combining MSC with FG, the implantation could take advantage of the mutual benefits. Researchers and physicians have pinned their hopes on stem cells for developing novel approaches in regenerative medicine. This review focuses on the therapeutic potential of MSC with FG in bone defect reconstruction, cartilage and tendon injury repair, ligament, heart and nerve regeneration, and, furthermore, wound healing.

Osteogenic differentiation of human placenta-derived mesenchymal stem cells (PMSCs) on electrospun nanofiber meshes

Numerous challenges remain in the successful clinical translation of cell-based therapeutic studies for skeletal tissue repair, including appropriate cell sources and viable cell delivery systems. Poly(ethylene glycol)-poly(ε-caprolactone) (PEG-PCL) amphiphilic block copolymers have been extensively explored in microspheres preparation. Due to the introduction of hydrophilic PEG segments into PCL backbones, these copolymers have shown much more potentials in carrying protein, lipophilic drugs or genes than commonly used poly (ε-caprolactone) (PCL) and poly (lactic acid). The aim of this study is to investigate the attachment and osteogenic differentiation of human placenta derived mesenchymal stem cells (PMSCs) on PEG-PCL triblock copolymers nanofiber scaffolds. Here we demonstrated that PMSCs proliferate robustly and can be effectively differentiated into osteogenic-like cells on nanofiber scaffolds. This study provides evidence for the use of nanofiber scaffolds as an ideal supporting material for in vitro PMSCs culture and an in vivo cell delivery vehicle for bone repair.

Non-virally Modified Human Mesenchymal Stem Cells Produce Ciliary Neurotrophic Factor in Biodegradable Fibrin-Based 3D Scaffolds

We report the adaptation of dendrimer-based nonviral expression system for ciliary neurotrophic factor (CNTF) overproduction in human mesenchymal stem cells (hMSCs) embedded into fibrin-based three-dimensional (3D) matrix. Time-restricted neurotrophin expression enables autologous adult stem cells for additional trophic support and increases their therapeutic potential in neuroregeneration applications. Polyamidoamine (PAMAM)-NH(2) dendrimers of fourth generation effectively provided virus-free delivery and expression of CNTF-internal ribosome entry site-green fluorescent protein cassette with a transfection efficiency in hMSCs over 11%. CNTF levels in transfected cultures were 10-fold higher as compared with the control cells. Dendrimer-driven CNTF expression also persisted in hMSCs embedded into fibrin-based 3D matrix, an emerging vehicle for cell delivery or bioartificial organ formation. Nonviral modification of autologous adult stem cells with use of dendrimers is a novel tool perspective in terms of biosafety and technological availability.

Injectable hydrogels for bone and cartilage repair

Injectable in situ crosslinkable gels are highly desirable clinically as they can be introduced into a body via a minimally invasive manner using endoscopic or percutaneous procedures. Several hydrophilic polymeric systems that respond to stimuli such as light, temperature, pH, ionic concentration as well as those that can undergo chemical reactions to form crosslinked matrices are currently under development. This paper discusses the applications of hydrogels as scaffolds to mimic the native extracellular matrix of bone and cartilage. A comprehensive description of various gelation methods used in hydrogel preparation and their application as injectable cell and protein delivery vehicle for bone and cartilage regeneration is also presented.