Growth Factor Delivery System Research Articles

Cell-Mediated Proteolytic Release of Growth Factors from Poly(Ethylene Glycol) Matrices.

Engineering in vitro tissue mimetics that resemble the corresponding living tissues requires the 3D arrangement of tissue progenitor cells and their differentiation by localized growth factor (GF) signaling cues. Recent technological advances open a large field of possibilities for the creation of complex GF arrangements. Additionally, cell-instructive biomaterials, which bind GFs by various mechanisms and release them with different kinetics depending on binding affinity, have become available. This paper describes the development of a matrix metalloproteinase (MMP)-degradable streptavidin-based linker module, which allows the release of immobilized GFs from synthetic biomimetic poly(ethylene glycol) hydrogels independently of the hydrogel degradation. The MMP-sensitive streptavidin linker is shown to efficiently bind biotinylated molecules, and as proof of concept, bone morphogenetic protein-2 (BMP-2) delivery via the MMP-degradable linker is used to induce osteogenic differentiation in C2C12 cells and mesenchymal stem cells. The results show a significantly increased net effect of proteolytically releasable BMP-2 in comparison to stably immobilized and soluble BMP-2. This study indicates that a GF delivery system directly responsive to cellular activity can have important implications for the synthesis of tissue mimetics and regenerative medicine, as it can influence the availability, the localization of effects, as well as efficacy of employed GFs.

Effects of BMP-9 and BMP-2 on the PI3K/Akt Pathway in MC3T3-E1 Preosteoblasts.

The bone morphogenetic proteins (BMPs), which are involved in bone formation and repair, play an important role in tissue engineering. For example, BMP-9 and BMP-2, which are members of different BMP subfamilies, are osteoinductive factors. However, several studies have recently shown that BMP-9 is more osteogenic than BMP-2. We have previously shown that fetal bovine serum (FBS) strongly enhances the osteoblast differentiation of murine preosteoblasts (MC3T3-E1) to BMP-9 but not to BMP-2. This effect is mimicked by IGF-2, which primarily activates the PI3K/Akt pathway, but how Akt phosphorylation sites are implicated in such differentiation is unclear. The effects of BMP-9 and BMP-2 with or without FBS or IGF-2 on Akt phosphorylation sites and subsequent osteoblastic differentiation were determined, respectively, by western blot analysis and alkaline phosphatase activity measurements. The involvement of phosphorylated Akt at Thr308 and/or Ser473 on BMP-mediated osteoblast differentiation was further studied using specific inhibitors. In MC3T3-E1 incubated with or without FBS, BMP-9 and BMP-2 activate Akt on Ser473 and Thr308 very differently in a time and dose-dependent manner. Using inhibitors specific to each Akt phosphorylation site, we showed that both Ser473 and Thr308 must be phosphorylated for BMP-9 and/or IGF-2-induced osteoblast differentiation, whereas BMP-2 requires phosphorylation of only Ser473. Furthermore, cells stimulated with BMP-2 in the presence of FBS require the phosphorylation of Akt at Ser473 and the dephosphorylation of Akt at Thr308 to increase the osteoblast differentiation with alkaline phosphatase activity similar to that of BMP-9 plus FBS. These results provide a better understanding into how BMP-9 induces osteoblast differentiation and its synergy with IGF-2 at the signaling level. This knowledge is essential for preparing the serum-free osteogenic media required for bone tissue engineering or developing growth factor delivery systems to improve bone formation.

Stem cells display a donor dependent response to escalating levels of growth factor release from extracellular matrix-derived scaffolds

Numerous growth factor delivery systems have been developed for tissue engineering. However, little is known about how the dose of a specific protein will influence tissue regeneration, or how different patients will respond to altered levels of growth factor presentation. The objective of the present study was to assess stem cell chondrogenesis within extracellular-matrix (ECM)-derived scaffolds loaded with escalating levels of transforming growth factor (TGF)-β3. It was also sought to determine if stem cells display a donor-dependent response to different doses of TGF-β3, from low (5ng) to high (200ng), released from such scaffolds. It was found that ECM-derived scaffolds possess the capacity to bind and release increasing amounts of TGF-β3, with between 60% and 75% of this growth factor released into the media over the first 12days of culture. After seeding these scaffolds with human infrapatellar fat pad-derived stem cells (FPSCs), it was found that cartilage-specific ECM accumulation was greatest for the higher levels of growth factor loading. Importantly, soak-loading cartilage ECM-derived scaffolds with high levels of TGF-β3 always resulted in at least comparable levels of chondrogenesis to controls where this growth factor was continuously added to the culture media. Similar results were observed for FPSCs from all donors, although the absolute level of secreted matrix did vary from donor to donor. Therefore, while no single growth factor release profile will be optimal for all patients, the results of this study suggest that the combination of a highly porous cartilage ECM-derived scaffold coupled with appropriate levels of TGF-β3 can consistently drive chondrogenesis of adult stem cells. Copyright © 2016 John Wiley & Sons, Ltd.

Extracellular Matrix (ECM) Multilayer Membrane as a Sustained Releasing Growth Factor Delivery System for rhTGF-β3 in Articular Cartilage Repair

Recombinant human transforming growth factor beta-3 (rhTGF-β3) is a key regulator of chondrogenesis in stem cells and cartilage formation. We have developed a novel drug delivery system that continuously releases rhTGF-β3 using a multilayered extracellular matrix (ECM) membrane. We hypothesize that the sustained release of rhTGF-β3 could activate stem cells and result in enhanced repair of cartilage defects. The properties and efficacy of the ECM multilayer-based delivery system (EMLDS) are investigated using rhTGF-β3 as a candidate drug. The bioactivity of the released rhTGF-ß3 was evaluated through chondrogenic differentiation of mesenchymal stem cells (MSCs) using western blot and circular dichroism (CD) analyses in vitro. The cartilage reparability was evaluated through implanting EMLDS with endogenous and exogenous MSC in both in vivo and ex vivo models, respectively. In the results, the sustained release of rhTGF-ß3 was clearly observed over a prolonged period of time in vitro and the released rhTGF-β3 maintained its structural stability and biological activity. Successful cartilage repair was also demonstrated when rabbit MSCs were treated with rhTGF-β3-loaded EMLDS ((+) rhTGF-β3 EMLDS) in an in vivo model and when rabbit chondrocytes and MSCs were treated in ex vivo models. Therefore, the multilayer ECM membrane could be a useful drug delivery system for cartilage repair.

Catheter-based Intramyocardial Injection of FGF1 or NRG1-loaded MPs Improves Cardiac Function in a Preclinical Model of Ischemia-Reperfusion.

Cardiovascular protein therapeutics such as neuregulin (NRG1) and acidic-fibroblast growth factor (FGF1) requires new formulation strategies that allow for sustained bioavailability of the drug in the infarcted myocardium. However, there is no FDA-approved injectable protein delivery platform due to translational concerns about biomaterial administration through cardiac catheters. We therefore sought to evaluate the efficacy of percutaneous intramyocardial injection of poly(lactic-co-glycolic acid) microparticles (MPs) loaded with NRG1 and FGF1 using the NOGA MYOSTAR injection catheter in a porcine model of ischemia-reperfusion. NRG1- and FGF1-loaded MPs were prepared using a multiple emulsion solvent-evaporation technique. Infarcted pigs were treated one week after ischemia-reperfusion with MPs containing NRG1, FGF1 or non-loaded MPs delivered via clinically-translatable percutaneous transendocardial-injection. Three months post-treatment, echocardiography indicated a significant improvement in systolic and diastolic cardiac function. Moreover, improvement in bipolar voltage and decrease in transmural infarct progression was demonstrated by electromechanical NOGA-mapping. Functional benefit was associated with an increase in myocardial vascularization and remodeling. These findings in a large animal model of ischemia-reperfusion demonstrate the feasibility and efficacy of using MPs as a delivery system for growth factors and provide strong evidence to move forward with clinical studies using therapeutic proteins combined with catheter-compatible biomaterials.

Engineered cell-free scaffold with two-stage delivery of miRNA-26a for bone repair.

The treatment of non-unions and bone defects is a major challenge. In these situations, autologous bone is the preferred treatment but has several serious limitations. Treatment alternatives including the use of calcium-based scaffolds alone or associated with either growth factors or stem cells have therefore been developed, or are under development, to overcome these shortcomings. Each of these are, however, associated with their own drawbacks, such as the lack of sustained/controlled delivery system for growth factors and poor cell survival and engraftment for stem cells. MicroRNAs (miRNAs), a class of small noncoding RNAs fine-tune the expression of as much as 30% of all mammalian protein-encoding genes. For instance, miRNA26a is able to promote the repair of critical-size calvarial bone defects. Yet, the clinical application of these fascinating molecules has been hampered by a lack of appropriate delivery systems. In an elegant report entitled cell-free 3D scaffold with two-stage delivery of miRNA-26a to regenerate critical-sized bone defects, Zhang et al. 2016, developped a non-viral vector with high affinity to miR-26a that ensured its efficient delivery in bone defects. Engineered scaffolds were able to induce the regeneration of calvarial bone defects in healthy and osteoporotic mice. Taken together, these data pave the way for the development of advanced bone substitutes that at least will match, and preferably supersede, the clinical efficiency of autologous bone grafts. However, the transfer from the bench to the bedside of such scaffolds requires further investigations including (I) a better understanding of the underlying biological mechanisms involved in bone formation via miRNA26a; (II) evidences of polymer scaffold biocompatibility upon its complete degradation; and (III) demonstration of the engineered scaffold functionality in defects of clinically relevant volume.

Peptide Amphiphile Nanogel as an Improved BMP-2 Carrier for Spinal Arthrodesis

Introduction Advances in biologics have led to improvements in spine fusion rates, but a commercially available bone graft substitute that elicits high bony fusion rates with minimal adverse effects is yet to be developed. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is FDA-approved for delivery on an absorbable collagen sponge (ACS), and promotes spine fusion at rates of > 90% in humans. However, the supraphysiologic dose required to elicit these high rates of fusion can lead to serious complications. In prior work, we found that nanofiber scaffolds composed of self-assembling peptide amphiphiles (PA) are improved carriers relative to ACS, with the ability to reduce the dose of exogenous growth factor necessary for spine arthrodesis by a factor of 10. We have also shown that assembling a PA nanogel on ACS improves the handling properties of the nanogel without compromising bioactivity. The purpose of this study was to develop a novel PA-based growth-factor carrier that would further reduce the amount of rhBMP-2 necessary to achieve high spine fusion rates, while simultaneously improving ease-of-delivery. We hypothesized that assembling a carboxyl-rich E3-PA nanogel with a slurry of Type I collagen particles would yield a malleable paste with improved growth factor delivery in a spine fusion setting. Material and Methods Female Sprague-Dawley rats underwent L4-L5 posterolateral spine fusion (PLF) with one of two experimental scaffolds: 1) E3PA-collagen slurry scaffold; or 2) E3PA/ACS. Scaffolds were preloaded with either saline or 100 ng rhBMP-2 (per animal). A negative comparative control group received ACS + 100 ng rhBMP-2. Bone regeneration and spine fusion were assessed using radiographs, fusion scoring, microCT imaging, and histology. Fusion scores were determined by blinded manual palpation using an established scoring system: 0 = no bridging bone, 1 = unilateral bridging, and 2 = bilateral bridging bone. Spines with an average score of ≥ 1.0 were considered successfully fused. Results When preloaded with 100 ng rhBMP-2, the E3PA/collagen slurry elicited a significantly higher mean fusion score relative to both equivalently pre-loaded ACS ( p < 0.001) and E3PA/ACS ( p < 0.01). Successful fusion was seen in 100% of animals treated with E3PA-collagen slurry + 100 ng rhBMP-2 (12/12 animals), which was significantly higher than fusion rates of both ACS + 100 ng rhBMP-2 (0%) and E3PA + 100 ng rhBMP-2 (8%) treatment groups. Use of the E3-collagen slurry for rhBMP-2 delivery reduced the growth factor requirement by 100-fold relative to the positive control in this model (10 µg rhBMP-2/ACS, which yields a fusion rate of 100% in the rat). Conclusion Exogenous growth factors, such as rhBMP-2, have the potential to significantly improve bony fusion rates. However, concerns regarding the safety of supraphysiologic concentrations of rhBMP-2—which are required for efficacy when delivered on ACS—make the development of improved growth factor delivery systems attractive. This study examined the growth factor delivery capacity of a PA nanogel/collagen slurry composite scaffold in a lumbar spine fusion setting. We found that delivery of rhBMP-2 using an E3PA-collagen slurry scaffold reduces the requirement for growth factor by a 100-fold relative to ACS in the rat PLF model.

A Novel HA/β-TCP-Collagen Composite Enhanced New Bone Formation for Dental Extraction Socket Preservation in Beagle Dogs.

Past studies in humans have demonstrated horizontal and vertical bone loss after six months following tooth extraction. Many biomaterials have been developed to preserve bone volume after tooth extraction. Type I collagen serves as an excellent delivery system for growth factors and promotes angiogenesis. Calcium phosphate ceramics have also been investigated because their mineral chemistry resembles human bone. The aim of this study was to compare the performance of a novel bioresorbable purified fibrillar collagen and hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) ceramic composite versus collagen alone and a bovine xenograft-collagen composite in beagles. Collagen plugs, bovine graft-collagen composite and HA/β-TCP-collagen composite were implanted into the left and right first, second and third mandibular premolars, and the fourth molar was left empty for natural healing. In total, 20 male beagle dogs were used, and quantitative and histological analyses of the extraction ridge was done. The smallest width reduction was 19.09% ± 8.81% with the HA/β-TCP-collagen composite at Week 8, accompanied by new bone formation at Weeks 4 and 8. The HA/β-TCP-collagen composite performed well, as a new osteoconductive and biomimetic composite biomaterial, for socket bone preservation after tooth extraction.

Dentin regeneration by stem cells of apical papilla on injectable nanofibrous microspheres and stimulated by controlled BMP-2 release

The aim of this study was to investigate the effects of PLLA nanofibrous microspheres (NF-MS) as a cell delivery carrier in combination with controlled release of BMP-2 from PLGA microspheres on the induction of odontogenic differentiation of human stem cells of apical papilla (SCAP). Injectable NF-MS, which mimic the physical architecture of collagen fibers on the nano scale, were fabricated by combining thermally-induced phase separation techniques with an emulsification process. SCAP cultured in a monolayer or cultured on NF-MS in spinner flasks were treated with 100ng/ml BMP-2 in vitro. Odontogenic differentiation was characterized by measuring alkaline phosphatase activity, odontogenic gene expression levels, calcium content, and dentin sialophosphoprotein accumulation. The results demonstrated that BMP-2 enhanced human SCAP odontogenic differentiation both in monolayer culture and on 3D NF-MS in spinner flask culture in vitro. We also developed and tested a system combining NF-MS with controlled BMP-2 release for dentin regeneration in vivo. The results indicate that controlled release of BMP-2 promoted more mineralization and osteodentin formation compared to a BSA-releasing control in a dose-dependent and time-dependent manner. In summary, the NF-MS combined with controlled release of BMP-2 provides an excellent microenvironment for SCAP to regenerate dentin tissue. Statement of SignificanceTooth lesion and loss affect masticatory efficiency, speaking function, facial aesthetics and even psychological health. Current treatments depend on “inert” restorative materials, which do not have the healing capacity and may lead to the failure of the restorations over a long term. The aim of this study was to develop an injectable biomaterial and desired growth factor delivery system to support stem cells for mineralized dental tissue regeneration. The study showed that novel injectable and biodegradable nanofibrous microspheres and controlled release of BMP-2 synergistically induce the odontogenic differentiation of human stem cells from the apical papilla and mineralized tissue regeneration, demonstrating the potential of living dental tissue repair.

Non-mulberry silk fibroin grafted poly(ε-caprolactone) nanofibrous scaffolds mineralized by electrodeposition: an optimal delivery system for growth factors to enhance bone regeneration

Nanofibrous PCL matrix with non-mulberry silk fibroin grafting and electrodeposited nHAp was used successfully as dual growth factor delivery medium forin vitroosteogenesis.

Fabrication and Characterization of NanoCalcium Sulfate and Human Platelet Lysate as a Growth Factor Delivery System

Fabrication and Characterization of NanoCalcium Sulfate and Human Platelet Lysate as a Growth Factor Delivery System

Characterization of novel autologous leukocyte fibrin platelet membranes for tissue engineering applications

Autologous hemocomponents have recently emerged as potential biologic tools for regenerative purpose, consisting mainly of platelet concentrates which locally release growth factors (GFs) to enhance the tissue healing process. Despite two decades of clinical studies, the therapeutic efficacy of platelet concentrates is still controversial. This work represents a first characterization of a novel autologous leukocyte fibrin platelet membrane (LFPm), which is prepared by the Department of Immunohematology of Belluno Hospital according to a well standardized protocol. The quantification of their specific content showed that LFPms are enriched not only with platelets, but also with monocytes/macrophages, fibrinogen and CD34+ cells. Mechanical properties of LFPms were investigated by tensile tests, revealing that the specific elasticity of membranes was maintained over time. Furthermore, the release kinetics of Platelet Derived Growth Factor, Vascular Endothelial Growth Factor, Tumor Necrosis Factor alpha and Interleukin-10 was assessed by ELISA, demonstrating that LFPms act as GF delivery systems which sustain the local release of bioactive molecules. For in vitro biodegradation analysis, LFPm samples were incubated into PBS solution for 4, 7, 14, 21 days. SEM micrographs showed a progressive loss in cellular elements associated to a simultaneous exposure of the fibrin scaffold, also confirmed by histological and immunohistochemical investigations. In parallel, LFPm disks were implanted into a subcutaneous dorsal pouch of healthy nude rats and explanted after 4, 7, 14, 21 days for in vivo biodegradation study. SEM, histological and immunohistochemical analysis revealed that the typical LFPm fibrin structure was maintained until day 7, with a contemporary loss of cellular elements. From day 14, the morphology and texture of samples became less and less recognizable, confirming that a progressive biodegradation occurred. Overall, collected evidences could support the rationale for the clinical use of LFPms, shading some light on the regenerative effect they may exert after the autologous implant on a defect site.

Affinity-based growth factor delivery system for tissue engineering

Affinity-based growth factor delivery system for tissue engineering

Chitosan sulfate: engineering a biomimetic growth factor delivery system

Chitosan sulfate: engineering a biomimetic growth factor delivery system

Controlled Dual Growth Factor Delivery From Microparticles Incorporated Within Human Bone Marrow-Derived Mesenchymal Stem Cell Aggregates for Enhanced Bone Tissue Engineering via Endochondral Ossification.

Bone tissue engineering via endochondral ossification has been explored by chondrogenically priming cells using soluble mediators for at least 3 weeks to produce a hypertrophic cartilage template. Although recapitulation of endochondral ossification has been achieved, long-term in vitro culture is required for priming cells through repeated supplementation of inductive factors in the media. To address this challenge, a microparticle-based growth factor delivery system was engineered to drive endochondral ossification within human bone marrow-derived mesenchymal stem cell (hMSC) aggregates. Sequential exogenous presentation of soluble transforming growth factor-β1 (TGF-β1) and bone morphogenetic protein-2 (BMP-2) at various defined time courses resulted in varying degrees of chondrogenesis and osteogenesis as demonstrated by glycosaminoglycan and calcium content. The time course that best induced endochondral ossification was used to guide the development of the microparticle-based controlled delivery system for TGF-β1 and BMP-2. Gelatin microparticles capable of relatively rapid release of TGF-β1 and mineral-coated hydroxyapatite microparticles permitting more sustained release of BMP-2 were then incorporated within hMSC aggregates and cultured for 5 weeks following the predetermined time course for sequential presentation of bioactive signals. Compared with cell-only aggregates treated with exogenous growth factors, aggregates with incorporated TGF-β1- and BMP-2-loaded microparticles exhibited enhanced chondrogenesis and alkaline phosphatase activity at week 2 and a greater degree of mineralization by week 5. Staining for types I and II collagen, osteopontin, and osteocalcin revealed the presence of cartilage and bone. This microparticle-incorporated system has potential as a readily implantable therapy for healing bone defects without the need for long-term in vitro chondrogenic priming. Significance: This study demonstrates the regulation of chondrogenesis and osteogenesis with regard to endochondral bone formation in high-density stem cell systems through the controlled presentation of inductive factors from incorporated microparticles. This work lays the foundation for a rapidly implantable tissue engineering system that promotes bone repair via endochondral ossification, a pathway that can delay the need for a functional vascular network and has an intrinsic ability to promote angiogenesis. The modular nature of this system lends well to using different cell types and/or growth factors to induce endochondral bone formation, as well as the production of other tissue types.

Beta Hairpin Peptide Hydrogels as an Injectable Solid Vehicle for Neurotrophic Growth Factor Delivery.

There is intense interest in developing novel methods for the sustained delivery of low levels of clinical therapeutics. MAX8 is a peptide-based beta-hairpin hydrogel that has unique shear thinning properties that allow for immediate rehealing after the removal of shear forces, making MAX8 an excellent candidate for injectable drug delivery at a localized injury site. The current studies examined the feasibility of using MAX8 as a delivery system for nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), two neurotrophic growth factors currently used in experimental treatments of spinal cord injuries. Experiments determined that encapsulation of NGF and BDNF within MAX8 did not negatively impact gel formation or rehealing and that shear thinning did not result in immediate growth factor release. ELISA, microscopy, rheology, and Western blotting experiments collectively demonstrate the functional capabilities of the therapeutic-loaded hydrogels to (i) maintain a protective environment against in vitro degradation of encapsulated therapeutics for at least 28 days; and (ii) allow for sustained release of NGF and BDGF capable of initiating neurite-like extensions of PC12 cells, most likely due to NGF/BDGF signaling pathways. Importantly, while the 21 day release profiles could be tuned by adjusting the MAX8 hydrogel concentration, the initial shear thinning of the hydrogel (e.g., during injection) does not induce significant premature loss of the encapsulated therapeutic, most likely due to effective trapping of growth factors within structurally robust domains that are maintained during the application of shear forces. Together, our data suggests that MAX8 allows for greater dosage control and sustained therapeutic growth factor delivery, potentially alleviating side effects and improving the efficacy of current therapies.

Osteogenic/angiogenic dual growth factor delivery microcapsules for regeneration of vascularized bone tissue.

Growth factors (GFs) are major biochemical cues for tissue regeneration. Herein, a novel dual GF delivery system is designed composed of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and alginate microcapsules (MCs) via an electrodropping method. While bone morphogenetic protein (BMP)-2 is encapsulated in the PLGA NPs, vascular endothelial growth factor (VEGF) is included in the alginate MCs, where BMP-2-loaded PLGA NPs are entrapped together in the fabrication process. The initial loading efficiencies of BMP-2 and VEGF are 78% ± 3.6% and 43% ± 1.7%, respectively. When our dual GF-loaded MCs are assessed for in vitro osteogenesis of umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) on 2D and 3D environment, MCs contribute to much better UCB-MSCs osteogenesis as confirmed by von Kossa staining, immunofluorescence (osteocalcin, collagen 1), calcium content measurement, and osteogenic markers expression. In addition, when dual GF-encapsulated MCs are combined with collagen and then applied to 8 mm diameter rat calvarial defect model, the positive effects on vascularized bone regeneration are much more pronounced; micro computed tomography (CT) and histology analyses exhibit 82.3% bone healing coupled with 12.6% vessel occupied area. Put together, current study indicates a synergistic effect of BMP-2/VEGF and highlights the great potential of dual GF delivery modality (PLGA NPs-in-MC) for regeneration of vascularized bone.

Controlled release of rhEGF and rhbFGF from electrospun scaffolds for skin regeneration.

Controlled delivery of multiple therapeutic agents can be considered as an effective approach in skin tissue engineering. In this study, recombinant human epidermal growth factor (rhEGF) and recombinant human basic fibroblast growth factor (rhbFGF) encapsulated in PLGA microspheres were loaded in hybrid scaffolds of PLGA and PEO. The scaffolds with various formulations were fabricated through electrospinning in order to maintain dual, individual or different release rate of rhEGF and rhbFGF. Morphological, physical and mechanical properties of the scaffold were investigated. The scaffold possessed uniform morphology with an average diameter of 280 nm for PLGA and 760 nm for PEO nanofibers. Furthermore, the mechanical properties of the scaffolds were shown to be akin to those of human skin. Bioactivity of the scaffolds for human skin fibroblasts was evaluated. The HSF acquired significant proliferation and well-spread morphology on the scaffolds particularly in the case of different release rate of rhEGF and rhbFGF which implies the synergistic effect of the growth factors. Additionally, collagen and elastin gene expression was significantly up-regulated in the HSF seeded on the scaffolds in the case of individual delivery of rhEGF and dual delivery of rhEGF and rhbFGF. In conclusion, the prepared scaffolds as a suitable supportive substrate and multiple growth factor delivery system can find extensive utilization in skin tissue engineering.

Biomimetic extracellular matrix mediated somatic stem cell differentiation: applications in dental pulp tissue regeneration.

Dental caries is one of the most widely prevalent infectious diseases in the world. It affects more than half of the world's population. The current treatment for necrotic dental pulp tissue arising from dental caries is root canal therapy. This treatment results in loss of tooth sensitivity and vitality making it prone for secondary infections. Over the past decade, several tissue-engineering approaches have attempted regeneration of the dental pulp tissue. Although several studies have highlighted the potential of dental stem cells, none have transitioned into a clinical setting owing to limited availability of dental stem cells and the need for growth factor delivery systems. Our strategy is to utilize the intact ECM of pulp cells to drive lineage specific differentiation of bone marrow derived mesenchymal stem cells. From a clinical perspective, pulp ECM scaffolds can be generated using cell lines and patient specific somatic stem cells can be used for regeneration. Our published results have shown the feasibility of using pulp ECM scaffolds for odontogenic differentiation of non-dental mesenchymal cells. This focused review discusses the issues surrounding dental pulp tissue regeneration and the potential of our strategy to overcome these issues.

Controlled release of growth factors for regenerative medicine.

How to release growth factors (GFs) scientifically to promote stem cell proliferation and differentiation is one of the most significant research focuses in the field of regenerative medicine. In a controlled release system, growth factors, extracellular matrices or biomaterial carriers, and sometimes stem cells together form a geometric entirety. Biomaterial carriers provide GFs with a support structure to be adhered, immobilized, encapsulated or/and protected. As a unity, the release rate and rhythm of GFs on cells are normally very delicate and precise. Up to now, the best strategy for clinical applications is the combination systems that encapsulate GFs in microspheres, particularly the nano- or micro-encapsulation techniques integrated GFs with biomaterial carriers. In this mini review, we summarize the current progress in GF delivery systems for regenerative medicine and provide an outlook on two main aspects: one is the classes of stem cells and GFs that have been used frequently in regenerative medicine, including their respective application conditions and functions; the other is the controlled GF release systems, in which various GFs are released orderly and continuously without diffusing simply and rapidly, including their respective opportunities and challenges.