Effect of biodegradable fibrin scaffold on survival, migration, and differentiation of transplanted bone marrow stromal cells after cortical injury in rats

Macro, Micro, and Nano-Inspired Bioactive Polymeric Biomaterials in Therapeutic, and Regenerative Orofacial Applications

Introducing dental polymers has accelerated biotechnological research, advancing tissue engineering, biomaterials development, and drug delivery. Polymers have been utilized effectively in dentistry to build dentures and orthodontic equipment and are key components in the composition of numerous restorative materials. Furthermore, dental polymers have the potential to be employed for medication administration and tissue regeneration. To analyze the influence of polymer-based investigations on practical medical trials, it is required to evaluate the research undertaken in this sector. The present review aims to gather evidence on polymer applications in dental, oral, and maxillofacial reconstruction.

Transparent PDMS Bioreactors for the Fabrication and Analysis of Multi-Layer Pre-vascularized Hydrogels Under Continuous Perfusion

Tissue engineering in combination with stem cell technology has the potential to revolutionize human healthcare. It aims at the generation of artificial tissues that can mimic the original with complex functions for medical applications. However, even the best current designs are limited in size, if the transport of nutrients and oxygen to the cells and the removal of cellular metabolites waste is mainly dependent on passive diffusion. Incorporation of functional biomimetic vasculature within tissue engineered constructs can overcome this shortcoming. Here, we developed a novel strategy using 3D printing and injection molding technology to customize multilayer hydrogel constructs with pre-vascularized structures in transparent Polydimethysiloxane (PDMS) bioreactors. These bioreactors can be directly connected to continuous perfusion systems without complicated construct assembling. Mimicking natural layer-structures of vascular walls, multilayer vessel constructs were fabricated with cell-laden fibrin and collagen gels, respectively. The multilayer design allows functional organization of multiple cell types, i.e., mesenchymal stem cells (MSCs) in outer layer, human umbilical vein endothelial cells (HUVECs) the inner layer and smooth muscle cells in between MSCs and HUVECs layers. Multiplex layers with different cell types showed clear boundaries and growth along the hydrogel layers. This work demonstrates a rapid, cost-effective, and practical method to fabricate customized 3D-multilayer vascular models. It allows precise design of parameters like length, thickness, diameter of lumens and the whole vessel constructs resembling the natural tissue in detail without the need of sophisticated skills or equipment. The ready-to-use bioreactor with hydrogel constructs could be used for biomedical applications including pre-vascularization for transplantable engineered tissue or studies of vascular biology.

Migration and Differentiation of Neural Stem Cells Diverted From the Subventricular Zone by an Injectable Self-Assembling β-Peptide Hydrogel

Neural stem cells, which are confined in localised niches are unable to repair large brain lesions because of an inability to migrate long distances and engraft. To overcome these problems, previous research has demonstrated the use of biomaterial implants to redirect increased numbers of endogenous neural stem cell populations. However, the fate of the diverted neural stem cells and their progeny remains unknown. Here we show that neural stem cells originating from the subventricular zone can migrate to the cortex with the aid of a long-lasting injectable hydrogel within a mouse brain. Specifically, large numbers of neuroblasts were diverted to the cortex through a self-assembling β-peptide hydrogel that acted as a tract from the subventricular zone to the cortex of transgenic mice (NestinCreER^T2:R26eYFP) in which neuroblasts and their progeny are permanently fluorescently labelled. Moreover, neuroblasts differentiated into neurons and astrocytes 35 days post implantation, and the neuroblast-derived neurons were Syn1 positive suggesting integration into existing neural circuitry. In addition, astrocytes co-localised with neuroblasts along the hydrogel tract, suggesting that they assisted migration and simulated pathways similar to the native rostral migratory stream. Lower levels of astrocytes were found at the boundary of hydrogels with encapsulated brain-derived neurotrophic factor, comparing with hydrogel implants alone.

Manipulation of Extracellular Matrix Remodeling and Neurite Extension by Mouse Embryonic Stem Cells Using IKVAV and LRE Peptide Tethering in Hyaluronic Acid Matrices

Cellular remodeling of the matrix has recently emerged as a key factor in promoting neural differentiation. Most strategies to manipulate matrix remodeling focus on proteolytically cleavable cross-linkers, leading to changes in tethered biochemical signaling and matrix properties. Using peptides that are not the direct target of enzymatic degradation will likely reduce changes in the matrix and improve control of biological behavior. In this study, laminin-derived peptides, IKVAV and LRE, tethered to independent sites in hyaluronic acid matrices using Michael addition and strain-promoted azide-alkyne cycloaddition are sufficient to manipulate hyaluronic acid degradation, gelatinase expression, and protease expression, while promoting neurite extension through matrix metalloprotease-dependent mechanisms in mouse embryonic stem cells encapsulated in hyaluronic acid matrices using an oxidation-reduction reaction initiated gelation. This study provides the foundation for a new strategy to stimulate matrix remodeling that is not dependent on enzymatic cleavage targets.

Engineering advanced neural tissue constructs to mitigate acute cerebral inflammation after brain transplantation in rats

Stroke, traumatic brain injuries, and other similar conditions often lead to significant loss of functional brain tissue and associated disruption of neuronal signaling. A common strategy for replacing lost neurons is the injection of dissociated neural stem cells or differentiated neurons. However, this method is unlikely to be suitable for replacing large brain cavities, and the resulting distribution of neurons may lack the necessary architecture to support appropriate brain function. Engineered neural tissues may be a viable alternative. Cell death is a prominent concern in neuronal grafting studies, a problem that could be magnified with the transplantation of engineered neural tissues. Here, we examined the effect of one contributor to cell death, acute cerebral inflammation, on neuronal survival after the transplantation of bioengineered constructs based on silk scaffolds. We found evidence of a high degree of inflammation and poor neuronal survival after introducing engineered constructs into the motor cortex of rats. Integrating a corticosteroid (methylprednisolone) into the constructs resulted in significantly improved neuron survival during the acute phase of inflammation. The improved construct survival was associated with decreased markers of inflammation and an anti-inflammatory state of the immune system due to the steroid treatment.

Human Recombinant Peptide Sponge Enables Novel, Less Invasive Cell Therapy for Ischemic Stroke

Bone marrow stromal cell (BMSC) transplantation has the therapeutic potential for ischemic stroke. However, it is unclear which delivery routes would yield both safety and maximal therapeutic benefits. We assessed whether a novel recombinant peptide (RCP) sponge, that resembles human collagen, could act as a less invasive and beneficial scaffold in cell therapy for ischemic stroke. BMSCs from green fluorescent protein-transgenic rats were cultured and Sprague–Dawley rats were subjected to permanent middle cerebral artery occlusion (MCAo). A BMSC-RCP sponge construct was transplanted onto the ipsilateral intact neocortex 7 days after MCAo. A BMSC suspension or vehicle was transplanted into the ipsilateral striatum. Rat motor function was serially evaluated and histological analysis was performed 5 weeks after transplantation. The results showed that BMSCs could proliferate well in the RCP sponge and the BMSC-RCP sponge significantly promoted functional recovery, compared with the vehicle group. Histological analysis revealed that the RCP sponge provoked few inflammatory reactions in the host brain. Moreover, some BMSCs migrated to the peri-infarct area and differentiated into neurons in the BMSC-RCP sponge group. These findings suggest that the RCP sponge may be a promising candidate for animal protein-free scaffolds in cell therapy for ischemic stroke in humans.

Polymeric Scaffolds for Pancreatic Tissue Engineering: A Review

In recent years, there has been an alarming increase in the incidence of diabetes, with one in every eleven individuals worldwide suffering from this debilitating disease. As the available treatment options fail to reduce disease progression, novel avenues such as the bioartificial pancreas are being given serious consideration. In the past decade, the research focus has shifted towards the field of tissue engineering, which helps to design biological substitutes for repair and replacement of non-functional or damaged organs. Scaffolds constitute an integral part of tissue engineering; they have been shown to mimic the native extracellular matrix, thereby supporting cell viability and proliferation. This review offers a novel compilation of the recent advances in polymeric scaffolds, which are used for pancreatic tissue engineering. Furthermore, in this article, the design strategies for bioartificial pancreatic constructs and their future applications in cell-based therapy are discussed.

Magnetic resonance imaging-three-dimensional printing technology fabricates customized scaffolds for brain tissue engineering

Conventional fabrication methods lack the ability to control both macro- and micro-structures of generated scaffolds. Three-dimensional printing is a solid free-form fabrication method that provides novel ways to create customized scaffolds with high precision and accuracy. In this study, an electrically controlled cortical impactor was used to induce randomized brain tissue defects. The overall shape of scaffolds was designed using rat-specific anatomical data obtained from magnetic resonance imaging, and the internal structure was created by computer-aided design. As the result of limitations arising from insufficient resolution of the manufacturing process, we magnified the size of the cavity model prototype five-fold to successfully fabricate customized collagen-chitosan scaffolds using three-dimensional printing. Results demonstrated that scaffolds have three-dimensional porous structures, high porosity, highly specific surface areas, pore connectivity and good internal characteristics. Neural stem cells co-cultured with scaffolds showed good viability, indicating good biocompatibility and biodegradability. This technique may be a promising new strategy for regenerating complex damaged brain tissues, and helps pave the way toward personalized medicine.

Modification of Bone Marrow Stem Cells for Homing and Survival During Cerebral Ischemia

Over the last decade, major advances have been made in stem cell-based therapy for ischemic stroke, which is one of the leading causes of death and disability worldwide. Various stem cells from bone marrow, such as mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and endothelial progenitor cells (EPCs), have shown therapeutic potential for stroke. Concomitant with these exciting findings are some fundamental bottlenecks that must be overcome in order to accelerate their clinical translation, including the low survival and engraftment caused by the harsh microenvironment after transplantation. In this chapter, strategies such as gene modification, hypoxia/growth factor preconditioning, and biomaterial-based methods to improve cell survival and homing are summarized, and the potential strategies for their future application are also discussed.

In Vivo Neural Tissue Engineering: Cylindrical Biocompatible Hydrogels That Create New Neural Tracts in the Adult Mammalian Brain

Individuals with neurodegenerative disorders or brain injury have few treatment options and it has been proposed that endogenous adult neural stem cells can be harnessed to repopulate dysfunctional nonneurogenic regions of the brain. We have accomplished this through the development of rationally designed hydrogel implants that recruit endogenous cells from the adult subventricular zone to create new relatively long tracts of neuroblasts. These implants are biocompatible and biodegradable cylindrical hydrogels consisting of fibrin and immobilized neurotrophic factors. When implanted into rat brain such that the cylinder intersected the migratory path of endogenous neural progenitors (the rostral migratory stream) and led into the nonneurogenic striatum, we observed a robust neurogenic response in the form of migrating neuroblasts with long (>100 μm) complex neurites. The location of these new neural cells in the striatum was directly coincident with the original track of the fibrin implant, which itself had completely degraded, and covered a significant area and distance (>2.5 mm). We also observed a significant number of neuroblasts in the striatal region between the implant track and the lateral ventricle. When these fibrin cylinders were implanted into hemiparkinson rats, correction of parkinsonian behavior was observed. There were no obvious behavioral, inflammatory or tumorigenic sequelae as a consequence of the implants. In conclusion, we have successfully engineered neural tissue in vivo, using neurogenic biomaterials cast into a unique cylindrical architecture. These results represent a novel approach to efficiently induce neurogenesis in a controlled and targeted manner, which may lead toward a new therapeutic modality for neurological disorders.

Translation of cell therapy into clinical practice: validation of an application procedure for bone marrow progenitor cells and platelet rich plasma

PURPOSE

Tissue regeneration can be improved by local application of autologous bone marrow derived progenitor cells (BMSC) and platelet rich plasma (PRP). However, there is a lack of standardized application procedures for clinical use. Therefore, a technique in accordance with the guidelines for advanced therapies medical products of the European Medicine Agency was developed and established.

METHODS

In detail, a process for the isolation and formulation of autologous bone marrow cells (BMC) and PRP in a clinical setting was validated. To investigate the influence of storage time and temperature on gel formation and gel stability, different concentrations of BMC were stored with and without additional platelets, thrombin and fibrinogen and analyzed over a period of 28 days. In addition, cell vitality using a live-dead staining and migration ability of human mesenchymal stem cells (hMSC) in the gel clot was investigated.

RESULTS

For an optimized stable gel clot, human BMC and PRP should be combined with 10% to 20% fibrinogen (9 mg/mL to 18 mg/mL) and 5% to 20% thrombin (25 I.E. to 100 I.E.). Both freshly prepared and stored cells for 1 to 7 days had a stable consistence over 28 days at 37°C. Different platelet concentrations did not influence gel clot formation. The ratio of living cells did not decrease significantly over the observation period of 5 days in the live-dead staining.

CONCLUSIONS

The study identified an optimal gel texture for local application of BMC and PRP. Seeded hMSC could migrate therein and were able to survive to initiate a healing cascade.

Comparison of the characteristics and multipotential and in vivo cartilage formation capabilities between porcine adipose-derived stem cells and porcine skin-derived stem cell-like cells

OBJECTIVE

To compare the characteristics and multipotential and in vivo cartilage formation capabilities of porcine adipose-derived stem cells (pASCs) with those of porcine skin-derived stem cell-like cells (pSSCs).

ANIMALS

Three 6-month-old female pigs and four 6-week-old female athymic mice.

PROCEDURES

Adipose and skin tissue specimens were obtained from each pig following slaughter and digested to obtain pASCs and pSSCs. For each cell type, flow cytometry and reverse transcription PCR assays were performed to characterize the expression of cell surface and mesenchymal stem cell markers, and in vitro cell cultures were performed to determine the adipogenic, osteogenic, and chondrogenic capabilities. Each cell type was then implanted into athymic mice to determine the extent of in vivo cartilage formation after 6 weeks.

RESULTS

The cell surface and mesenchymal stem cell marker expression patterns, multipotential capability, and extent of in vivo cartilage formation did not differ significantly between pASCs and pSSCs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that pSSCs may be a viable alternative to pASCs as a source of progenitor cells for tissue engineering in regenerative medicine.

Generation and transplantation of reprogrammed human neurons in the brain using 3D microtopographic scaffolds

Cell replacement therapy with human pluripotent stem cell-derived neurons has the potential to ameliorate neurodegenerative dysfunction and central nervous system injuries, but reprogrammed neurons are dissociated and spatially disorganized during transplantation, rendering poor cell survival, functionality and engraftment in vivo. Here, we present the design of three-dimensional (3D) microtopographic scaffolds, using tunable electrospun microfibrous polymeric substrates that promote in situ stem cell neuronal reprogramming, neural network establishment and support neuronal engraftment into the brain. Scaffold-supported, reprogrammed neuronal networks were successfully grafted into organotypic hippocampal brain slices, showing an ∼3.5-fold improvement in neurite outgrowth and increased action potential firing relative to injected isolated cells. Transplantation of scaffold-supported neuronal networks into mouse brain striatum improved survival ∼38-fold at the injection site relative to injected isolated cells, and allowed delivery of multiple neuronal subtypes. Thus, 3D microscale biomaterials represent a promising platform for the transplantation of therapeutic human neurons with broad neuro-regenerative relevance.

Human pluripotent stem cell derived neurons have the potential for cell replacement therapy for brain injury and disease but problems on transplantation need to be overcome. Here, the authors use a microtopographic scaffold to graft neurons into both hippocampal organoids and the mouse brain striatum.

Differentiation of Human Endometrial Stem Cells into Schwann Cells in Fibrin Hydrogel as 3D Culture

Human endometrial stem cells (hEnSCs) are a new source of adult multipotent stem cells with the ability of differentiation into many cell lineages. Many stem cell sources are desirable for differentiation into Schwann cells. Schwann-like cells derived from hEnSCs may be one of the ideal alternative cell sources for Schwann cell generation. In this study, for differentiation of hEnSCs into Schwann cells, hEnSCs were induced with RA/FSK/PDGF-AA/HRG as an induction medium for 14 days. The cells were cultured in a tissue culture plate (TCP) and fibrin gel matrix. The viability of cultured cells in the fibrin gel and TCP was analyzed with 3-[4,5-dimethyl-2-thia-zolyl]-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay for 7 days. The attachment of cells was analyzed with SEM and DAPI staining. The expression of S100 and P75 as Schwann cell markers was evaluated by immunocytochemistry and quantitative real-time PCR (RT-PCR). The evaluation of the MTT assay and gene expression showed that the survival rate and differentiation of hEnSCs into Schwann cells in the fibrin gel were better than those in the TCP group. These results suggest that human EnSCs can be differentiated into Schwann cells in the fibrin gel better than in the TCP, and the fibrin gel might provide a suitable three-dimensional (3D) scaffold for clinical applications for cell therapy of the nervous system.

In Vitro Evaluation of Scaffolds for the Delivery of Mesenchymal Stem Cells to Wounds

Mesenchymal stem cells (MSCs) have been shown to improve tissue regeneration in several preclinical and clinical trials. These cells have been used in combination with three-dimensional scaffolds as a promising approach in the field of regenerative medicine. We compare the behavior of human adipose-derived MSCs (AdMSCs) on four different biomaterials that are awaiting or have already received FDA approval to determine a suitable regenerative scaffold for delivering these cells to dermal wounds and increasing healing potential. AdMSCs were isolated, characterized, and seeded onto scaffolds based on chitosan, fibrin, bovine collagen, and decellularized porcine dermis. In vitro results demonstrated that the scaffolds strongly influence key parameters, such as seeding efficiency, cellular distribution, attachment, survival, metabolic activity, and paracrine release. Chick chorioallantoic membrane assays revealed that the scaffold composition similarly influences the angiogenic potential of AdMSCs in vivo. The wound healing potential of scaffolds increases by means of a synergistic relationship between AdMSCs and biomaterial resulting in the release of proangiogenic and cytokine factors, which is currently lacking when a scaffold alone is utilized. Furthermore, the methods used herein can be utilized to test other scaffold materials to increase their wound healing potential with AdMSCs.

Optimization of adhesive conditions for neural differentiation of murine embryonic stem cells using hydrogels functionalized with continuous Ile-Lys-Val-Ala-Val concentration gradients

Stem cell therapies, which aim to restore neurological function after central nervous system injury, have shown increased efficacy when a tissue engineering matrix is implanted with cells compared to implantation of the cells alone. However, much work still needs to be done to characterize materials that can be used to facilitate and direct the differentiation of implanted cells. In the current study, polyethylene glycol hydrogels functionalized with continuous Ile-Lys-Val-Ala-Val (IKVAV) concentration gradients were fabricated and utilized to systematically study and optimize the adhesive conditions for neural differentiation of mouse embryonic stem cells in two- and three-dimensional environments. The results suggest that 570 μM and 60 μM are the optimal IKVAV concentrations for 2D and 3D neural differentiation, respectively, to maximize mRNA expression of neuron-specific markers and neurite extension while minimizing apoptotic activities in cultured cells compared to those exposed to higher IKVAV concentrations. The combinatorial approach presented in this work demonstrates that hydrogels functionalized with bioactive peptides provide a defined and tunable platform that can be employed to characterize and improve culture conditions for superior survival, maturation and integration of implanted cells, leading to enhanced restoration of neurological function for those receiving stem cell therapies after traumatic brain and spinal cord injuries.

Therapeutic-designed electrospun bone scaffolds: mesoporous bioactive nanocarriers in hollow fiber composites to sequentially deliver dual growth factors

A novel therapeutic design of nanofibrous scaffolds, holding a capacity to load and deliver dual growth factors, that targets bone regeneration is proposed. Mesoporous bioactive glass nanospheres (MBNs) were used as bioactive nanocarriers for long-term delivery of the osteogenic enhancer fibroblast growth factor 18 (FGF18). Furthermore, a core-shell structure of a biopolymer fiber made of polyethylene oxide/polycaprolactone was introduced to load FGF2, another type of cell proliferative and angiogenic growth factor, safely within the core while releasing it more rapidly than FGF18. The prepared MBNs showed enlarged mesopores of about 7 nm, with a large surface area and pore volume. The protein-loading capacity of MBNs was as high as 13% when tested using cytochrome C, a model protein. The protein-loaded MBNs were smoothly incorporated within the core of the fiber by electrospinning, while preserving a fibrous morphology. The incorporation of MBNs significantly increased the apatite-forming ability and mechanical properties of the core-shell fibers. The possibility of sequential delivery of two experimental growth factors, FGF2 and FGF18, incorporated either within the core-shell fiber (FGF2) or within MBNs (FGF18), was demonstrated by the use of cytochrome C. In vitro studies using rat mesenchymal stem cells demonstrated the effects of the FGF2-FGF18 loadings: significant stimulation of cell proliferation as well as the induction of alkaline phosphate activity and cellular mineralization. An in vivo study performed on rat calvarium defects for 6 weeks demonstrated that FGF2-FGF18-loaded fiber scaffolds had significantly higher bone-forming ability, in terms of bone volume and density. The current design utilizing novel MBN nanocarriers with a core-shell structure aims to release two types of growth factors, FGF2 and FGF18, in a sequential manner, and is considered to provide a promising therapeutic scaffold platform that is effective for bone regeneration.

Effects of polycaprolactone-based scaffolds on the blood-brain barrier and cerebral inflammation

Severe pathoanatomical and mechanical injuries compromise patient recovery and survival following penetrating brain injury (PBI). The realization that the blood-brain barrier (BBB) plays a major role in dictating post-PBI events has led to rising interests in possible therapeutic interventions through the BBB. Recently, the choroid plexus has also been suggested as a potential therapeutic target. The use of biocompatible scaffolds for the delivery of therapeutic agents, but little is known about their interaction with cerebral tissue, which has important clinical implications. Therefore, the authors have sought to investigate the effect of polycaprolactone (PCL) and PCL/tricalcium phosphate (PCL/TCP) scaffolds on the maintenance of BBB phenotype posttraumatic brain injury. Cranial defects of 3 mm depth were created in Sprague Dawley rats, and PCL and PCL/TCP scaffolds were subsequently implanted in predetermined locations for a period of 1 week and 1 month. Higher endothelial barrier antigen (EBA) expressions from PCL-based scaffold groups (p>0.05) were found, suggesting slight advantages over the sham group (no scaffold implantation). PCL/TCP scaffold group also expressed EBA to a higher degree (p>0.05) than PCL scaffolds. Importantly, higher capillary count and area as early as 1 week postimplantation suggested lowered ischemia from the PCL/TCP scaffold group as compared with PCL and sham. Evaluation of interlukin-1β expression suggested that the PCL and PCL/TCP scaffolds did not cause prolonged inflammation. BBB transport selectivity was evaluated by the expression of aquaporin-4 (AQP-4). Attenuated expression of AQP-4 in the PCL/TCP group (p<0.05) suggested that PCL/TCP scaffolds altered BBB selectivity to a lower degree as compared with sham and PCL groups, pointing to potential clinical implications in reducing cerebral edema. Taken together, the responses of PCL-based scaffolds with brain tissue suggested safety, and encourages further preclinical evaluation in PBI management with these scaffolds.

Dental pulp stem cells differentiation into retinal ganglion-like cells in a three dimensional network

The loss of retinal ganglion cells (RGCs) in majority of retinal degenerative diseases is the first seen pathological event. A lot of studies aim to discover suitable cell sources to replace lost and damaged RGCs. Among them dental pulp stem cells (DPSCs) have a great potential of differentiating into neuronal lineages as well as RGCs. Moreover, three-dimensional (3D) networks and its distribution for growing and differentiation of stem cells as much as possible mimic to native tissue holds great potential in retinal tissue engineering. In this study, we isolate DPSCs from rat incisors and validate them with flow cytometry. Briefly, we differentiated cells using DMEM/F12 containing FGF2, Shh and 0.5% FBS into retinal ganglion-like cells (RGLCs) in two conditions; 3D state in biocompatible fibrin hydrogel and two-dimensional (2D) or conventional culture in polystyrene plates. Immuncytochemical and gene expression analysis revealed the expression of Pax6, Atoh7 and BRN3B increased in 3D fibrin culture compared to 2D conventional culture. In combination, these data demonstrate that using 3D networks can resemble near natural tissue properties for effective generating RGCs which used to treat neurodegenerative diseases such as glaucoma.

Biological characteristics of human-urine-derived stem cells: potential for cell-based therapy in neurology

Stem cells in human urine have gained attention in recent years; however, urine-derived stem cells (USCs) are far from being well elucidated. In this study, we compared the biological characteristics of USCs with adipose-derived stem cells (ASCs) and investigated whether USCs could serve as a potential cell source for neural tissue engineering. USCs were isolated from voided urine with a modified culture medium. Through a series of experiments, we examined the growth rate, surface antigens, and differentiation potential of USCs, and compared them with ASCs. USCs showed robust proliferation ability. After serial propagation, USCs retained normal karyotypes. Cell surface antigen expression of USCs was similar to ASCs. With lineage-specific induction factors, USCs could differentiate toward the osteogenic, chondrogenic, adipogenic, and neurogenic lineages. To assess the ability of USCs to survive, differentiate, and migrate, they were seeded onto hydrogel scaffold and transplanted into rat brain. The results showed that USCs were able to survive in the lesion site, migrate to other areas, and express proteins that were associated with neural phenotypes. The results of our study demonstrate that USCs possess similar biological characteristics with ASCs and have multilineage differentiation potential. Moreover USCs can differentiate to neuron-like cells in rat brain. The present study shows that USCs are a promising cell source for tissue engineering and regenerative medicine.

Systems level approach reveals the correlation of endoderm differentiation of mouse embryonic stem cells with specific microstructural cues of fibrin gels

Stem cells receive numerous cues from their associated substrate that help to govern their behaviour. However, identification of influential substrate characteristics poses difficulties because of their complex nature. In this study, we developed an integrated experimental and systems level modelling approach to investigate and identify specific substrate features influencing differentiation of mouse embryonic stem cells (mESCs) on a model fibrous substrate, fibrin. We synthesized a range of fibrin gels by varying fibrinogen and thrombin concentrations, which led to a range of substrate stiffness and microstructure. mESCs were cultured on each of these gels, and characterization of the differentiated cells revealed a strong influence of substrate modulation on gene expression patterning. To identify specific substrate features influencing differentiation, the substrate microstructure was quantified by image analysis and correlated with stem cell gene expression patterns using a statistical model. Significant correlations were observed between differentiation and microstructure features, specifically fibre alignment. Furthermore, this relationship occurred in a lineage-specific manner towards endoderm. This systems level approach allows for identification of specific substrate features from a complex material which are influential to cellular behaviour. Such analysis may be effective in guiding the design of scaffolds with specific properties for tissue engineering applications.

Brain tissue interaction with three-dimensional, honeycomb polycaprolactone-based scaffolds designed for cranial reconstruction following traumatic brain injury

Following traumatic brain injury (TBI), resultant voids are unable to support injections of suspension treatments, leading to ineffective healing. Moreover, without a structure to support the large defect, the defect site suffers from mechanical instability, which may impair the healing process. Therefore, having a delivery vehicle that can temporarily fill and provide mechanical support to the defect site may alleviate the healing process. In this work, we reported for the first time, the inflammatory response of brain tissue with polycaprolactone (PCL) and PCL-tricalcium phosphate (TCP) scaffolds designed and fabricated for cranial reconstruction. After cranial defects were created in Sprague-Dawley rats, PCL and PCL-TCP scaffolds were implanted for a period of 1 week and 1 month. Following histology and immunofluorescence staining with the ionized calcium binding adaptor molecule-1 (IBA-1), glial fibrillary acidic protein (GFAP), nestin, and neuronal nuclei (NeuN), results indicated that IBA-1-positive activated microglia were observed across all groups, and declined significantly by 1 month (p<0.05). Interestingly, IBA-1-positive microglia were significantly fewer in the PCL-TCP group (p<0.05), suggesting a relatively milder inflammatory response. A decrease in the number of GFAP-positive cells among all groups over time (>29%) was also observed. Initially, astrocyte hypertrophy was observed proximal to the TBI site (55% in PCL and PCL-TCP groups, 75% in control groups), but it subsided by 1 month. Proximal to the TBI site, nestin immunoreactivity was intense during week 1, and which reduced by 1 month across all groups. NeuN-positive neurons were shrunken proximal to the TBI site (<0.9 mm), 32% smaller in the PCL-TCP group and 27% smaller in the PCL group. Based on above data indicating the comparatively milder, initial inflammatory response of brain tissue to PCL-TCP scaffolds, it is suggested that PCL-TCP scaffolds have notable clinical advantages as compared to PCL scaffolds.

Fibrin scaffolds containing ectomesenchymal stem cells enhance behavioral and histological improvement in a rat model of spinal cord injury

Fibrin has been widely used in wound healing. However, its benefit for spinal cord injury (SCI) is limited. In this study, we investigated the impact of fibrin scaffolds containing ectomesenchymal stem cells (EMSCs) on histological and behavioral recovery after SCI and compared it with fibrin alone. To achieve this, EMSCs derived from adult rat nasal respiratory mucosa were cultured, characterized and transfected with green fluorescent protein adenovirus before transplantation. Then, Sprague-Dawley host rats were randomly assigned into four groups: the control group (laminectomy); the SCI group (laminectomy and transection of spinal cords); the fibrin group (fibrin was transplanted immediately after SCI), and the fibrin cell (FC) group (fibrin scaffolds containing EMSCs were transplanted after SCI). Three days after the operation, a TUNEL assay indicated less apoptotic cells in the FC group than in the fibrin group. Two weeks after SCI, fluorescence staining demonstrated not only the survival and migration of EMSCs into the lesion sites, but also a higher number of nerve fibers in the FC group than in the fibrin group. Histological examination including immunohistochemistry and transmission electron microscopy 12 weeks after the operation showed more nerve fibers and a thicker myelin sheath in the FC group compared to the fibrin group. Western blotting confirmed these morphological results. Consistent with the histological results, Basso, Beattie and Bresnahan locomotor scores of the FC group were higher than those of the fibrin group. These results suggest that fibrin scaffolds containing EMSCs can improve the behavioral and histological recovery after SCI better than fibrin alone.

Ultrasound-mediated gene transfer (sonoporation) in fibrin-based matrices: potential for use in tissue regeneration

It has been suggested that gene transfer into donor cells is an efficient and practical means of locally supplying requisite growth factors for applications in tissue regeneration. Here we describe, for the first time, an ultrasound-mediated system that can non-invasively facilitate gene transfer into cells entrapped within fibrin-based matrices. Since ultrasound-mediated gene transfer is enhanced using microbubbles, we compared the efficacy of neutral and cationic forms of these reagents on the ultrasound-stimulated gene transfer process in gel matrices. In doing so we demonstrated the beneficial effects associated with the use of cationic microbubble preparations that interact directly with cells and nucleic acid within matrices. In some cases, gene expression was increased two-fold in gel matrices when cationic microbubbles were compared with neutral microbubbles. In addition, incorporating collagen into fibrin gels yielded a 25-fold increase in gene expression after application of ultrasound to microbubble-containing matrices. We suggest that this novel system may facilitate non-invasive temporal and spatial control of gene transfer in gel-based matrices for the purposes of tissue regeneration.

Electrospun silk fibroin nanofibers in different diameters support neurite outgrowth and promote astrocyte migration

Nerve tissue engineering has been one of the promising strategies for regenerative treatment in patients suffering from neural tissue loss, but considerable challenges remain before it is able to progress toward clinical application. It has been demonstrated that transplantation of cells in combination with physically or chemically modified biomaterials provides better environments for neurite outgrowth and further promotes axonal regeneration in animal models of spinal cord injury. In this study, neurons and astrocytes were incorporated into 400-nm, 800-nm, and 1200-nm electrospun Bombyx mori silk fibroin (SF) materials to investigate the effects of scaffold-diameter in regulating and directing cell behaviors. β-III-tubulin immunofluorescence analyses reveal that SF nanofibers with smaller diameters are more favorable to the development and maturation of subventricular zone-derived neurons than 1200-nm SF scaffolds. In addition, astrocytes exhibited well-arranged glial fibrillary acidic protein (GFAP) expression on SF scaffolds, and a significant increase in cell-spreading area was observed on 400-nm but not 1200-nm SF scaffolds. Moreover, a significantly enhanced migration efficiency of astrocytes grown on SF scaffolds was verified, which highlights the guiding roles of SF nanofibers to the migratory cells. Overall, our results may provide valuable information to develop effective tissue remodeling substrates and to optimize existing biomaterials for neural tissue engineering applications.

Nanomaterials design and tests for neural tissue engineering

Nanostructured scaffolds recently showed great promise in tissue engineering: nanomaterials can be tailored at the molecular level and scaffold morphology may more closely resemble features of extracellular matrix components in terms of porosity, framing and biofunctionalities. As a consequence, both biomechanical properties of scaffold microenvironments and biomaterial-protein interactions can be tuned, allowing for improved transplanted cell engraftment and better controlled diffusion of drugs. Easier said than done, a nanotech-based regenerative approach encompasses different fields of know-how, ranging from in silico simulations, nanomaterial synthesis and characterization at the nano-, micro- and mesoscales to random library screening methods (e.g. phage display), in vitro cellular-based experiments and validation in animal models of the target injury. All of these steps of the "assembly line" of nanostructured scaffolds are tightly interconnected both in their standard analysis techniques and in their most recent breakthroughs: indeed their efforts have to jointly provide the deepest possible analyses of the diverse facets of the challenging field of neural tissue engineering. The purpose of this review is therefore to provide a critical overview of the recent advances in and drawbacks and potential of each mentioned field, contributing to the realization of effective nanotech-based therapies for the regeneration of peripheral nerve transections, spinal cord injuries and brain traumatic injuries. Far from being the ultimate overview of such a number of topics, the reader will acknowledge the intrinsic complexity of the goal of nanotech tissue engineering for a conscious approach to the development of a regenerative therapy and, by deciphering the thread connecting all steps of the research, will gain the necessary view of its tremendous potential if each piece of stone is correctly placed to work synergically in this impressive mosaic.

Stem cell therapy for cerebral ischemia: from basic science to clinical applications

Recent stem cell technology provides a strong therapeutic potential not only for acute ischemic stroke but also for chronic progressive neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis with neuroregenerative neural cell replenishment and replacement. In addition to resident neural stem cell activation in the brain by neurotrophic factors, bone marrow stem cells (BMSCs) can be mobilized by granulocyte-colony stimulating factor for homing into the brain for both neurorepair and neuroregeneration in acute stroke and neurodegenerative diseases in both basic science and clinical settings. Exogenous stem cell transplantation is also emerging into a clinical scene from bench side experiments. Early clinical trials of intravenous transplantation of autologous BMSCs are showing safe and effective results in stroke patients. Further basic sciences of stem cell therapy on a neurovascular unit and neuroregeneration, and further clinical advancements on scaffold technology for supporting stem cells and stem cell tracking technology such as magnetic resonance imaging, single photon emission tomography or optical imaging with near-infrared could allow stem cell therapy to be applied in daily clinical applications in the near future.

Therapeutic effects of intra-arterial delivery of bone marrow stromal cells in traumatic brain injury of rats--in vivo cell tracking study by near-infrared fluorescence imaging

BACKGROUND

A noninvasive and effective route of cell delivery should be established to yield maximal therapeutic effects for central nervous system (CNS) disorders.

OBJECTIVE

To elucidate whether intra-arterial delivery of bone marrow stromal cells (BMSCs) significantly promotes functional recovery in traumatic brain injury (TBI) in rats.

METHODS

Rat BMSCs were transplanted through the ipsilateral internal carotid artery 7 days after the onset of cortical freezing injury. The BMSCs were labeled with fluorescent dye, and in vivo optical imaging was employed to monitor the behaviors of cells for 4 weeks after transplantation. Motor function was assessed for 4 weeks, and the transplanted BMSCs were examined using immunohistochemistry.

RESULTS

In vivo optical imaging and histologic analysis clearly demonstrated that the intra-arterially injected BMSCs were engrafted during the first pass without systemic circulation, and the transplanted BMSCs started to migrate from the cerebral capillary bed to the injured CNS tissue within 3 hours. Intra-arterial BMSC transplantation significantly promoted functional recovery after cortical freezing injury. A subgroup of BMSCs expressed the phenotypes of neurons, astrocytes, and endothelial cells around the injured neocortex 4 weeks after transplantation.

CONCLUSION

Intra-arterial transplantation may be a valuable option for prompt, noninvasive delivery of BMSCs to the injured CNS tissue, enhancing functional recovery after TBI. In vivo optical imaging may provide important information on the intracerebral behaviors of donor cells by noninvasive, serial visualization.

Cellular attachment and osteoblast differentiation of mesenchymal stem cells on natural cuttlefish bone

The purpose of this study was to describe an approach that aims to provide fundamental information for the application of natural cuttlefish bone. Before applying cuttlefish bone as a bone defect filling material, we evaluated proliferation, adhesion, and cell viability of human mesenchymal stem cells (hMSCs) cultured on cuttlefish bone. Cuttlefish bone was separated into two parts (dorsal shield and lamellar region) and each part was used. Cell proliferation and viability were assessed using the MTS assay and live/dead fluorescence staining method. The morphology was observed using scanning electron microscopy (SEM). hMSCs were stimulated with osteogenic medium and osteoblast differentiation was evaluated. The fluorescence images showed that the seeded cells grew well and that cell distribution was in accordance with the surface morphology of the cuttlefish bone. Compared with the dorsal shield, cells penetrated deeper into the three-dimensional inner space of the lamellar part. Furthermore, under osteogenic differentiation conditions, alkaline phosphatase activity increased and the mRNA expression of ALP, runt-related transcription factor 2, and collagen type I α1 was increased in hMSCs cultured on both the dorsal shield and lamellar block. These results indicate the potential of cuttlefish bone as an ideal scaffold for bone regenerative materials. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.

The effects of electrospun TSF nanofiber diameter and alignment on neuronal differentiation of human embryonic stem cells

Although transplantation of human embryonic stem cells (hESCs)-derived neural precursors (NPs) has been demonstrated with some success for nervous repair in small animal model, control of the survival, and directional differentiation of these cells is still challenging. Meanwhile, the notion that using suitable scaffolding materials to control the growth and differentiation of grafted hESC-derived NPs raises the hope for better clinical nervous repair. In this study, we cultured hESC-derived NPs on Tussah silk fibroin (TSF)-scaffold of different diameter (i.e., 400 and 800 nm) and orientation (i.e., random and aligned) to analyze the effect of fiber diameter and alignment on the cell viability, neuronal differentiation, and neurite outgrowth of hESC-derived NPs. The results show that TSF-scaffold supports the survival, migration, and differentiation of hESC-derived NPs. Aligned TSF-scaffold significantly promotes the neuronal differentiation and neurite outgrowth of hESC-derived neurons compared with random TSF-scaffold. Moreover, on aligned 400 nm fibers cell viability, neuronal differentiation and neurite outgrowth are greater than that on aligned 800 nm fibers. Together, these results demonstrate that aligned 400 nm TSF-scaffold is more suitable for the development of hESC-derived NPs, which shed light on optimization of the therapeutic potential of hESCs to be employed for neural regeneration.

Cellular modulation of polymeric device surfaces: promise of adult stem cells for neuro-prosthetics

Minimizing the foreign body response is seen as one critical research strategy for implants especially when designed for immune-privileged organs like the brain. The context of this work is to improve deep brain stimulating devices used in a consistently growing spectrum of psychomotor and psychiatric diseases mainly in form of stiff electrodes. Based on the compliance match hypothesis of biocompatibility we present another step forward using flexible implant materials covered with brain cell-mimicking layers. We covered two types of flexible polyimide films with glandular stem cells derived from pancreatic acini. Using real time-PCR and fluorescent immunocytochemistry we analyzed markers representing various cell types of all three germ layers and stemness. The results demonstrate an unchanged differentiation potential of the polyimide fixated cells as measured by mRNA and protein level. Additionally we developed a fibrinous hydrogel coating to protect them against shear forces upon eventual implantation. By repeating previous analysis and additional metabolism tests for all stages we corroborate the validity of this improvement. Consequently we assume that a stem cell-containing cover may provide a native, fully and actively integrating brain-mimicking interface to the neuropil.

Autologous bone marrow stromal cell transplantation for central nervous system disorders - recent progress and perspective for clinical application

There is increasing evidence that the transplanted BMSC significantly promote functional recovery after CNS damage in the animal models of various kinds of CNS disorders, including cerebral infarct, traumatic brain injury and spinal cord injury. However, there are several shortages of information when considering clinical application of BMSC transplantation for patients with CNS disorders. In this review, therefore, we discuss what we should clarify to establish cell transplantation therapy as the scientifically proven entity in clinical situation and describe our recent works for this purpose. The BMSC have the ability to alter their gene expression profile and phenotype in response to the surrounding circumstances and to protect the neurons by producing some neurotrophic factors. They also promote neurite extension and rebuild the neural circuits in the injured CNS. The BMSC can be expanded in vitro using the animal serum-free medium. Pharmacological modulation may accelerate the in vitro proliferation of the BMSC. Using in vivo optical imaging technique, the transplanted BMSC can non-invasively be tracked in the living animals for at least 8 weeks after transplantation. It is urgent issues to develop clinical imaging technique to track the transplanted cells in the CNS and evaluate the therapeutic significance of BMSC transplantation in order to establish it as a definite therapeutic strategy in clinical situation in the future.