Incorporation Of Growth Factors Research Articles

Thermoresponsive Injectable Microparticle-Gel Composites with Recombinant BMP-9 and VEGF Enhance Bone Formation in Rats.

Bone morphogenetic protein-9 (BMP-9) has been shown to be the most osteogenic BMP. Most of these experiments, however, involve an adenovirus-transfection strategy. Here, we used the scaffold-based strategy to study the bone forming ability of recombinant BMP-9 combined with vascular endothelial growth factor (VEGF). A robust, injectable, multicomponent-releasing scaffold in the form of a composite gel was developed by combining chitosan microparticles (MPs) with thermosensitive gel (MPs-gel). The MPs acted as the carriers for BMP-9 and the gel was loaded with VEGF. The developed gel consisted of hydrophobic chains of methyl cellulose (MC) and the cross-linked structures of alginate (Alg) and calcium. Gelation was achieved at physiological temperature and thus facilitated the injection and localization of MPs enabling an increased efficacy of incorporated growth factors at the target site. A release profile of incorporated growth factors over a two-week period showed higher release of VEGF at each time point compared to that of BMP-9. Human mesenchymal stem cells (hMSCs) encapsulated within the MPs-gel maintained their viability. BMP-9 enhanced the proliferation of hMSCs along the surface of MPs. Furthermore, BMP-9 potently induced the osteogenic differentiation of encapsulated hMSCs elucidated by the increased alkaline phosphatase (ALP) activity and the higher expression of ALP, collagen 1, and osteocalcin genes. In addition, in vivo experiments demonstrated that MPs-gel with the combination of BMP-9-VEGF could significantly enhance both subcutaneous and cranial bone formation (p < 0.05). Taken together, the results here strongly suggest that BMP-9-VEGF incorporated MPs-gel holds promise as an injectable bone tissue engineering platform.

Influence of fiber architecture and growth factor formulation on osteoblastic differentiation of mesenchymal stem cells in coacervate-coated electrospun fibrous scaffolds

In order to achieve effective bone regeneration, the architectural/structural and biological environment must be considered. In this study, we investigated the influence of structure of extracellular matrix-mimicking electrospun poly (l-lactic acid) (PLLA) fibrous scaffolds and incorporated growth factors (bone morphogenetic protein2 (BMP2) and platelet-derived growth factor (PDGF)) (GFs) on in vitro differentiation of human mesenchymal stem cells (hMSCs) cultured onto the scaffolds. Furthermore, Cargo GFs were first encapsulated into coacervate (Coa). Coa-coated nano-sized PLLA (Coa-nPLLA) exhibited relatively higher coating efficacy, than Coa-coated micro-sized PLLA (Coa-mPLLA) due to large mesh hole area of mPLLA. Consequently, a faster GF release pattern was observed in nPLLA groups. As a result of osteogenic differentiation of hMSC which cultured onto GFs loaded Coa-PLLA, the architectural cue of fiber diameters effectively modulated early osteogenic differentiation of hMSCs. Facilitated long-term differentiation of hMSCs could be achieved by synergistic effect of dual BMP2 and PDGF in nanofbrous environments.

A Review of Growth Factor Support in Bloodless Autologous Hematopoietic Stem Cell Transplant.

Bloodless autologous hematopoietic cell transplantation is associated with risks of severe bleeding and profound anemia. RBC or platelet transfusions are often used to prevent these hematologic complications. However, in patients such as Jehovah's Witnesses who refuse major blood components, the lack of transfusion support is not an absolute contraindication to an autologous hematopoietic cell transplant. Pennsylvania Hospital performed the world's first bloodless hematopoietic cell transplant more than 15 years ago and has gradually improved its technique with a sizable patient population. Erythropoiesis-stimulating agents were successfully employed as part of their pretransplant regimen to prevent severe anemia. Thrombopoietin agonists' potential role in bloodless transplant is also currently being explored. Although there is limited literature, available reports in combination with physiologic reasoning may support the use of these growth factors to promote transplant success. These agents offer potential benefit and may be of utility in minimizing complications of a bloodless transplant. In this review, we summarize the available literature and offer insight into how we may incorporate growth factors to allow bloodless autologous hematopoietic cell transplantation to be an available option to patients who may otherwise be denied.

BIODEGRADABLE VASCULAR GRAFT REINFORCED WITH A BIODEGRADABLE SHEATH

Background. Tissue-engineered vascular grafts can be reinforced by a biostable or biodegradable polymer sheath. A combination of electrospinning, routinely used for fabrication of biodegradable tubular grafts, and the layer-by-layer coating allows forming a polymeric sheath ensuring long-term integrity and high biocompatibility of the vascular grafts after the implantation. Aim To evaluate mechanical properties and in vivo performance of biodegradable small-diameter vascular grafts with a reinforcing sheath.Methods. Tubular grafts (4 mm diameter) were fabricated from poly(3-hydroxybutyrate-co3-hydroxyvalerate) and poly(ε-caprolactone) by emulsion electrospinning with the incorporation of vascular endothelial growth factor (VEGF) into the inner third of the graft and basic fibroblast growth factor (bFGF) along with stromal cell-derived factor-1α (SDF-1α) into the outer two thirds of the graft wall. Poly(ε-caprolactone) sheath was formed by the layer-by-layer coating. Upon graft fabrication, scanning electron microscopy was performed to assess the grafts’ surface, tensile testing allowed evaluating mechanical properties. The samples were implanted into the ovine carotid artery (n = 5 animals) for 12 months with the subsequent histological examination.Results. Sintering temperature of 160°C during the extrusion allowed effective and delicate merging of poly(ε-caprolactone) coating with the outer surface of the poly(3hydroxybutyrate-co-3-hydroxyvalerate)/poly(ε-caprolactone) tubular graft. The thickness of poly(ε-caprolactone) fiber was 380–400 μm, the increment of the reinforcing filament was 1 mm. The reinforcing sheath led to a 3-fold increase in durability and elastic modulus of the vascular grafts. At the 12-months follow-up, the grafts reported retained integrity. No signs of inflammation or calcification were found.Conclusion. The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(ε-caprolactone) vascular grafts with hierarchically incorporated growth factors and the reinforced poly(ε-caprolactone) spiral sheath demonstrated improved mechanical properties while retaining integrity and high biocompatibility after the long-term implantation into the ovine carotid artery.

Impact of growth factors on wound healing in polysaccharide blend thin films

Abstract The potential of alginate/carboxymethyl cellulose based thin films was demonstrated as a testing platform for evaluation of the influence of in situ incorporated growth factors into formulations intended for 3D bio-printed wound healing materials. Actual formation of blend films with and without included growth factors was analysed using ATR-IR spectroscopy. Surface morphology and topography were evaluated by atomic force and scanning electron microscopies, whereas the hydrophilicity of all tested materials was determined using the water contact angle measurement method. The inclusion of growth factors into blend films did not affect the films' formation, nor their morphology, whereas their highly hydrophilic character was even slightly enhanced by the added growth factors. Further, several aspects (viability, proliferation and cell morphology), in regard to the blend films included growth factors' influence on both of the most abundant skin cell types (keratynocytes and fibroblasts) were tested. A significantly improved cell viability was detected for films with incorporated growth factors. The prepared thin film-based testing platform could present an important tool to aid the development of novel printable (bio)inks.

Barrier membranes: More than the barrier effect?

AimTo review the knowledge on the mechanisms controlling membrane–host interactions in guided bone regeneration (GBR) and investigate the possible role of GBR membranes as bioactive compartments in addition to their established role as barriers.Materials and MethodsA narrative review was utilized based on in vitro, in vivo and available clinical studies on the cellular and molecular mechanisms underlying GBR and the possible bioactive role of membranes.ResultsEmerging data demonstrate that the membrane contributes bioactively to the regeneration of underlying defects. The cellular and molecular activities in the membrane are intimately linked to the promoted bone regeneration in the underlying defect. Along with the native bioactivity of GBR membranes, incorporating growth factors and cells in membranes or with graft materials may augment the regenerative processes in underlying defects.ConclusionIn parallel with its barrier function, the membrane plays an active role in hosting and modulating the molecular activities of the membrane‐associated cells during GBR. The biological events in the membrane are linked to the bone regenerative and remodelling processes in the underlying defect. Furthermore, the bone‐promoting environments in the two compartments can likely be boosted by strategies targeting both material aspects of the membrane and host tissue responses.

Progress in three-dimensional printing with growth factors

Incorporation of growth factors in biomedical constructs can encourage cellular activities necessary for tissue regeneration within an implant system. Three-dimensional printing offers a capacity for spatial dictation and dosage control of incorporated growth factors which promises to minimize complications from the supraphysiologic doses and burst release involved in current growth factor delivery systems. Successful implementation of three-dimensional printing with growth factors requires preservation of the bioactivity of printed growth factors, spatial localization of growth factors within the construct architecture during printing, and controlled release of growth factors after printing. This review describes demonstrated approaches for addressing each of these goals, including direct inclusion of growth factors with the biomaterial during printing, or intermediary encapsulation of growth factors in delivery vehicles such as microparticles or nanoparticles.

Mesenchymal stem cell interacted with PLCL braided scaffold coated with poly-l-lysine/hyaluronic acid for ligament tissue engineering.

The challenge of finding an adapted scaffold for ligament tissue engineering remains unsolved after years of researches. A technology to fabricate a multilayer braided scaffold with flexible and elastic poly (l-lactide-co-caprolactone) (PLCL 85/15) has been recently pioneered by our team. In this study, polyelectrolyte multilayer films (PEM) with poly-l-lysine (PLL)/ hyaluronic acid (HA) were deposited on this scaffold. After PEM modification, polygonal (PLL) and particle-like (HA) structures were present on the braided scaffold with no significant variation of fibers Young's modulus. Wharton's jelly mesenchymal stem cells (WJ-MSC) and bone marrow mesenchymal stem cells (BM-MSC) showed good metabolic activity on scaffolds. They presented a spindled shape along the fiber longitudinal direction, and crossed the fibers to form cell bridges. Collagen type I, collagen type III, and tenascin-C secreted by MSCs were detected on day 14. Moreover, one-layer modified scaffold presented increased chemotaxis. As a conclusion, our results indicate that this braided PLCL scaffold with one-layer PEM modification shows inspiring potential with satisfying mechanical properties and biocompatibility. It opens new perspectives to incorporate growth factors within PEM-modified braided PLCL scaffold for ligament tissue engineering and to recruit endogenous cells after implantation. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3042-3052, 2018.

IN SITU VASCULAR TISSUE REMODELING USING BIODEGRADABLE TUBULAR SCAFFOLDS WITH INCORPORATED GROWTH FACTORS AND CHEMOATTRACTANT MOLECULES

Background Currently, the search for the bioactive molecules capable of promoting formation of the vascular tissue is still ongoing. We have previously demonstrated that incorporation of the growth factors and chemoattractant molecules into the biodegradable tubular scaffolds can increase their primary patency upon the implantation into rat abdominal aorta. However, further studies are required to investigate tissue remodeling using functionalized vascular grafts with the same diameter as a replaced native vessel. Aim To investigate the specific aspects of de novo vascular tissue formation and calcification employing rat abdominal aorta interposition model and vascular grafts with 1.5 mm diameter with incorporated vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and stromal cell-derived factor (SDF)-1α. Methods Tubular grafts with a diameter of 1.5 mm were blended of poly(3-hydroxybutyrateco-3-hydroxyvalerate) and poly(ε-caprolactone) (PHBV/PCL). Grafts without growth factors were fabricated using standard electrospinning technique whilst grafts with incorporated growth factors were prepared utilizing emulsion electrospinning. VEGF was incorporated into the inner third, whereas bFGF and SDF-1α were incorporated into the outer two-thirds of the graft. Grafts were implanted into the abdominal aortas of Wistar rats for 1, 3, 6, and 12 months following scanning electron microscopy along with histological and immunofluorescent examination. Results Primary patency of the grafts with VEGF, bFGF, and SDF-1α reached 93% indicative of structural integrity of the vascular tissue. Neither signs of inflammation nor severe calcification was detected. Conclusion As in 2 mm diameter vascular grafts, incorporation of bioactive factors into 1.5 mm diameter grafts increased their long-term primary patency and improved vascular tissue formation in comparison with non-modified grafts.

3D printing bioactive PLGA scaffolds using DMSO as a removable solvent

Present bioprinting techniques lack the methodology to print with bioactive materials that retain their biological functionalities. This constraint is due to the fact that extrusion-based printing of synthetic polymers is commonly performed at very high temperatures in order to achieve desired mechanical properties and printing resolutions. Consequently, current methodology prevents printing scaffolds embedded with bioactive molecules, such as growth factors. With the wide use of mesenchymal stem cells (MSCs) in regenerative medicine research, the integration of growth factors into 3D printed scaffolds is critical because it can allow for inducible MSC differentiation. We have successfully incorporated growth factors into extrusion printed poly (lactic-co-glycolic acid) (PLGA) scaffolds by introducing dimethyl sulfoxide (DMSO) for low temperature printing. Mechanical testing results demonstrated significantly different compressive and tensile properties for PLGA scaffolds printed with or without DMSO. In particular, the PLGA/DMSO scaffolds displayed a highly stretchable feature compared to the regular PLGA scaffolds. The cellular response of growth factor introduction was evaluated in vitro using human mesenchymal stem cells (hMSCs). By evaporating the DMSO after printing, we ensured that there was no cytotoxic effect on seeded hMSCs. The addition of lineage specific growth factors led to increased expression of corresponding genetic markers for chondrogenesis, osteogenesis, and adipogenesis. We concluded that the use of DMSO for 3D printed scaffold fabrication with bioactive items is a revolutionary methodology in advancing regenerative medicine. The incorporation of bioactive molecules opens pathways to more therapeutic uses for 3D printing in treating damaged or deteriorating native tissue.

Recent Advances in Biomaterials for 3D Printing and Tissue Engineering.

Three-dimensional printing has significant potential as a fabrication method in creating scaffolds for tissue engineering. The applications of 3D printing in the field of regenerative medicine and tissue engineering are limited by the variety of biomaterials that can be used in this technology. Many researchers have developed novel biomaterials and compositions to enable their use in 3D printing methods. The advantages of fabricating scaffolds using 3D printing are numerous, including the ability to create complex geometries, porosities, co-culture of multiple cells, and incorporate growth factors. In this review, recently-developed biomaterials for different tissues are discussed. Biomaterials used in 3D printing are categorized into ceramics, polymers, and composites. Due to the nature of 3D printing methods, most of the ceramics are combined with polymers to enhance their printability. Polymer-based biomaterials are 3D printed mostly using extrusion-based printing and have a broader range of applications in regenerative medicine. The goal of tissue engineering is to fabricate functional and viable organs and, to achieve this, multiple biomaterials and fabrication methods need to be researched.

Magnetically Controlled Growth-Factor-Immobilized Multilayer Cell Sheets for Complex Tissue Regeneration.

The scaffold-free cell-sheet technique plays a significant role in stem-cell-based regeneration. Furthermore, growth factors are known to direct stem cell differentiation and enhance tissue regeneration. However, the absence of an effective means to incorporate growth factors into the cell sheets hinders further optimization of the regeneration efficiency. Here, a novel design of magnetically controlled "growth-factor-immobilized cell sheets" is reported. A new Fe3 O4 magnetic nanoparticle (MNP) coated with nanoscale graphene oxide (nGO@Fe3 O4 ) is developed to label stem cells and deliver growth factors. First, the nGO@Fe3 O4 MNPs can be easily swallowed by dental-pulp stem cells (DPSCs) and have no influence on cell viability. Thus, the MNP-labeled cells can be organized via magnetic force to form multilayered cell sheets in different patterns. Second, compared to traditional Fe3 O4 nanoparticles, the graphene oxide coating provides plenty of carboxyl groups to bind and deliver growth factors. Therefore, with these nGO@Fe3 O4 MNPs, bone-morphogenetic-protein-2 (BMP2) is successfully incorporated into the DPSCs sheets to induce more bone formation. Furthermore, an integrated osteochondral complex is also constructed using a combination of DPSCs/TGFβ3 and DPSCs/BMP2. All these results demonstrate that the new cell-sheet tissue-engineering approach exhibits promising potential for future use in regenerative medicine.

Two-phase electrospinning to incorporate growth factors loaded chitosan nanoparticles into electrospun fibrous scaffolds for bioactivity retention and cartilage regeneration

Growth factor is an essential ingredient to regulate mesenchymal stem cells (MSCs) chondrogenic differentiation in cartilage tissue engineering. However, non-osteochondral specification, short plasma half time and bioactivity loss restrict growth factor's application. Thus, novel chondrogenic growth factors, specifically target osteochondral lineage cells, that can be sustained release and bioactivity protected to exert functions continually and effectively have attracted increasing researchers' interest. To achieve these goals, chitosan nanoparticles and electrospun fiber scaffolds were used as dual release system to sustain release Nel-like molecule-1 (Nell-1) growth factor and protect bioactivity, then the effect and mechanism of Nell-1 on inducing human bone MSCs (hBMSCs) differentiate toward chondrocytes were investigated. For release and bioactivity protection study, preloading Nell-1 into chitosan nanoparticles significantly extended the release time, increased the released Nell-1's bioactivity than directly incorporating Nell-1 into the scaffolds. Furthermore, Nell-1 specifically promotes hBMSCs in vitro chondrogenic differentiation by increasing expression of chondrogenic related genes and proteins. These findings suggest the potential utility of Nell-1 incorporated dual release scaffold for cartilage tissue engineering.

Cellularizing hydrogel-based scaffolds to repair bone tissue: How to create a physiologically relevant micro-environment?

Tissue engineering is a promising alternative to autografts or allografts for the regeneration of large bone defects. Cell-free biomaterials with different degrees of sophistication can be used for several therapeutic indications, to stimulate bone repair by the host tissue. However, when osteoprogenitors are not available in the damaged tissue, exogenous cells with an osteoblast differentiation potential must be provided. These cells should have the capacity to colonize the defect and to participate in the building of new bone tissue. To achieve this goal, cells must survive, remain in the defect site, eventually proliferate, and differentiate into mature osteoblasts. A critical issue for these engrafted cells is to be fed by oxygen and nutrients: the transient absence of a vascular network upon implantation is a major challenge for cells to survive in the site of implantation, and different strategies can be followed to promote cell survival under poor oxygen and nutrient supply and to promote rapid vascularization of the defect area. These strategies involve the use of scaffolds designed to create the appropriate micro-environment for cells to survive, proliferate, and differentiate in vitro and in vivo. Hydrogels are an eclectic class of materials that can be easily cellularized and provide effective, minimally invasive approaches to fill bone defects and favor bone tissue regeneration. Furthermore, by playing on their composition and processing, it is possible to obtain biocompatible systems with adequate chemical, biological, and mechanical properties. However, only a good combination of scaffold and cells, possibly with the aid of incorporated growth factors, can lead to successful results in bone regeneration. This review presents the strategies used to design cellularized hydrogel-based systems for bone regeneration, identifying the key parameters of the many different micro-environments created within hydrogels.

An invitro study of fibrin sealant as a carrier system for recombinanthuman bone morphogenetic protein (rhBMP)-9forbonetissue engineering.

In the craniofacial bone field, fibrin sealants are used as coagulant and adhesive tools to stabilize grafts during surgery. Despite this, their exact role in osteogenesis is poorly characterized. In the present study, we aimed to characterize the osteogenic potential of TISSEEL fibrin sealant and used its technology to incorporate growth factors within its matrix. We focused on recombinant human bone morphogenetic protein (rhBMP)-9, which has previously been characterized as one of the strongest osteogenetic inducers in the BMP family. TISSEEL displayed an excellent ability to retain rhBMP9, which was gradually released over a 10-day period. Although TISSEEL decreased bone stromal ST2 cell attachment at 8h, it displayed normal cell proliferation at 1, 3, and 5 days when compared to tissue culture plastic. Interestingly, TISSEEL had little influence on osteoblast differentiation; however its combination with rhBMP9 significantly increased ALP activity at 7 days, Alizarin Red staining at 14 days, and mRNA levels of osteoblast differentiation markers ALP, bone sialoprotein, and osteocalcin. In summary, although fibrin sealants were shown to have little influence on osteogenesis, their combination with bone-inducing growth factors such as rhBMP9 may serve as an attractive carrier/scaffold for future bone regenerative strategies. Future animal studies are now necessary.

Heparinized collagen sutures for sustained delivery of PDGF-BB: Delivery profile and effects on tendon-derived cells In-Vitro

Suturing is the standard of repair for lacerated flexor tendons. Past studies focused on delivering growth factors to the repair site by incorporating growth factors to nylon sutures which are commonly used in the repair procedure. However, conjugation of growth factors to nylon or other synthetic sutures is not straightforward. Collagen holds promise as a suture material by way of providing chemical sites for conjugation of growth factors. On the other hand, collagen also needs to be reconstituted as a mechanically robust thread that can be sutured. In this study, we reconstituted collagen solutions as suturable collagen threads by using linear electrochemical compaction. Prolonged release of PDGF-BB (Platelet derived growth factor-BB) was achieved by covalent bonding of heparin to the collagen sutures. Tensile mechanical tests of collagen sutures before and after chemical modification indicated that the strength of sutures following chemical conjugation stages was not compromised. Strength of lacerated tendons sutured with epitendinous collagen sutures (11.2±0.7N) converged to that of the standard nylon suture (14.9±2.9N). Heparin conjugation of collagen sutures didn’t affect viability and proliferation of tendon-derived cells and prolonged the PDGF-BB release up to 15days. Proliferation of cells seeded on PDGF-BB incorporated collagen sutures was about 50% greater than those seeded on plain collagen sutures. Collagen that is released to the media by the cells increased by 120% under the effects of PDGF-BB and collagen production by cells was detectable by histology as of day 21. Addition of PDGF-BB to collagen sutures resulted in a moderate decline in the expression of the tendon-associated markers scleraxis, collagen I, tenomodulin, and COMP; however, expression levels were still greater than the cells seeded on collagen gel. The data indicate that the effects of PDGF-BB on tendon-derived cells mainly occur through increased cell proliferation and that longer term studies are needed to confirm whether this proliferation is outweighs the moderate reduction in the expression of tendon-associated genes. Statement of SignificanceA mechanically robust pure collagen suture was fabricated via linear electrocompaction and conjugated with heparin for prolonged delivery of PDFG-BB. Sustained delivery of the PDGF-BB improved the proliferation of tendon derived cells substantially at the expense of a moderate downregulation of tenogenic markers. The collagen threads were functionally applicable as epitendinous sutures when applied to chicken flexor tendons in vitro. Overall, electrocompacted collagen sutures holds potential to improve repair outcome in flexor tendon surgeries by improving cellularity and collagen production through delivery of the PDGF-BB. The bioinductive suture concept can be applied to deliver other growth factors for a wide-array of applications.

Microparticle scaffolds support osteogenic differentiation of mscs

Event Abstract Back to Event Microparticle scaffolds support osteogenic differentiation of mscs Karolina Stumbraite1, Ryan M. Clohessy1, Barbara D. Boyan1, 2 and Zvi Schwartz1, 3 1 Virginia Commonwealth University, Biomedical Engineering, United States 2 Georgia Institute of Technology, Biomedical Engineering, United States 3 University of Texas Health Science Center at San Antonio, Periodontics, United States Introduction: The effect metal surface features have on the differentiation of mesenchymal stem cells (MSCs) is well studied; however, less is known about polymers. Scaffolds with varying porosities, architectures, and topographies have been shown to support osteogenic differentiation, but they typically incorporate growth factors or small peptides or cells and are cultured in the presence of osteogenic media supplements. The objective of this study was to investigate the effect polymer surface roughness has on osteoblast differentiation of MSCs by examining the response to a sintered and etched poly-lactide-co-glycolide microparticle (PLGA) scaffold. Materials and Methods: PLGA (65:35) was cast at 150°C for 2h and ground into particles. Sieved particles (250-500µm) were packed into 15mm molds and heat sintered at 90°C for 2h. Scaffolds were etched with 5N NaOH for 1h (1hrEtch) or 2hr (2hrEtch), rinsed with ultrapure water, and dried. Scaffolds were characterized qualitatively by SEM, and quantitatively by CLSM and µCT. Construct yield stress and compressive modulus were measured at 10% strain/min using an MTS Instron Insight 30. Osteogenic differentiation of human MSCs on etched scaffolds was compared to cells on un-etched scaffolds (NoEtch). Cells cultured on tissue culture polystyrene (TCPS) served as a control. MSCs (20,000 cells/scaffold) were cultured in growth media (GM) for 2d, after which a subset of scaffolds were cultured in osteogenic media (OM) while the others continued in GM for 6d. DNA, alkaline phosphatase activity, osteocalcin, vascular endothelial growth factor (VEGF), bone morphogenetic protein-2 (BMP-2) and osteoprotegerin (OPG) were measured after eight days in culture. Results are n=6 cultures/variable for one representative experiment and analyzed by ANOVA and post-hoc by Bonferroni. Results: Etched micropits were visible on 1hrEtch and 2hrEtch that were not present on NoEtch samples. Total scaffold porosity was 43.9% (NoEtch), 42.3% (1hrEtch), and 45.4% (2hrEtch) with more than 99% of pores being open or interconnected. Etching significantly increased average scaffold roughness (Ra, µm: NoEtch 1.25±0.42; 1hrEtch 1.99±0.18; 2hrEtch 2.79±0.18). Compressive modulus and yield stress decreased as etching time increased. DNA content was lower on scaffolds than on TCPS (data not shown). Cells on etched scaffolds had elevated levels of osteocalcin, VEGF, BMP-2, and OPG (Fig 1) when treated with OM whereas OM did not affect cells on TCPS or non-etched scaffolds. Discussion and Conclusions: Microparticle scaffolds can be fabricated using a heat sintering process and surface modified through an etching treatment. The surface-etched scaffold enhanced effects of OM on osteoblast differentiation of MSCs after only 6d v. more than 14d on TCPS. Although etching decreased mechanical properties, the beneficial cell response outweighs this drawback and suggests that etched polymer scaffolds may be used as a bone substitute. Keywords: Scaffold, Bone repair, Nano/micro particle Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Synthetic scaffolds as extracellular matrices Citation: Stumbraite K, Clohessy RM, Boyan BD and Schwartz Z (2016). Microparticle scaffolds support osteogenic differentiation of mscs. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.02817 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Karolina Stumbraite Ryan M Clohessy Barbara D Boyan Zvi Schwartz Google Karolina Stumbraite Ryan M Clohessy Barbara D Boyan Zvi Schwartz Google Scholar Karolina Stumbraite Ryan M Clohessy Barbara D Boyan Zvi Schwartz PubMed Karolina Stumbraite Ryan M Clohessy Barbara D Boyan Zvi Schwartz Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Tubular Tissues and Organs of Human Body--Challenges in Regenerative Medicine.

Tissue engineering of tubular organs such as the blood vessel, trachea gastrointestinal tract, urinary tract are of the great interest due to the high amount of surgeries performed annually on those organs. Development in tissue engineering in recent years and promising results, showed need to investigate more complex constructs that need to be designed in special manner. Stent technology remain the most widely used procedure to restore functions of tubular tissues after cancer treatment, or after organ removal due to traumatic accidents. Tubular structures like blood vessels, intestines, and trachea have to work in specific environment at the boundary of the liquids, solids or air and surrounding tissues and ensure suitable separation between them. This brings additional challenges in tissue engineering science in order to construct complete organs by using combinations of various cells along with the support material systems. Here we give a comprehensive review of the tubular structures of the human body, in perspective of the current methods of treatment and progress in regenerative medicine that aims to develop fully functioning organs of tubular shape. Extensive analysis of the available literature has been done focusing on materials and methods of creations of such organs. This work describes the attempts to incorporate growth factors and drugs within the scaffolds to ensure localized drug release and enhance vascularization of the organ by attracting blood vessels to the site of implantation.

Cell-free scaffolds with different stiffness but same microstructure promote bone regeneration in rabbit large bone defect model.

To promote bone healing, bone repair biomaterials are increasingly designed to incorporate growth factors. However, the impact of matrix mechanics of cell-free scaffold independent of microstructure on the osteogenic differentiation of endogenous osteoprogenitor cells orchestrating bone repair and regeneration remains not to be fully understood. In our recent study, three-dimensional (3D) scaffolds with different stiffness but same microstructure have been successfully fabricated by coating decellularized bone with collagen/hydroxyapatite (HA) mixture with different collagen rations. It has been demonstrated that the scaffold with optimal stiffness can induce the osteogenic differentiation of MSCs in vitro and in the subcutaneous tissue. The present in vivo study further investigated the repair efficiency of these scaffolds in a rabbit radius with a critical-sized segmental defect model and its potential mechanism. Micro-computed tomography (μ-CT), X-ray and histological analysis were carried out to evaluate the repair capacity of these scaffolds. The results demonstrated that the cell-free scaffold with optimal stiffness incorporation of endogenous osteoprogenitor cells significantly promoted the repair and reconstruction quality of mass bone defect. One of the crucial mechanisms was that hypoxia and stromal cell-derived factor-1α (SDF-1α) mediated mesenchymal stem cells (MSCs) migration by which matrix mechanics exerted influence on bone fracture healing. These findings suggested that only modulating the matrix stiffness of cell-free scaffold can be one of the most attractive strategies for promoting the progression of bone healing.

Concentrated growth factor increases Schwann cell proliferation and neurotrophic factor secretion and promotes functional nerve recovery in vivo.

Concentrated growth factor (CGF) is a newly generated complex that comprises a fibrin matrix incorporating growth factors and plasmatic and leukocyte cytokines. It has been widely used in bone regenerative medicine. However, the effect of CGF on peripheral nerve regeneration had not been previously investigated. The aim of the present study was to evaluate the possibility of using CGF for nerve regeneration by i) investigating the effect of CGF on the proliferation of Schwann cells (SCs) and secretion of neurotrophic factors nerve growth factor (NGF) and glial cell line‑derived neurotrophic factor (GDNF) in vitro; and ii) analyzing the effect of CGF on functional nerve recovery after nerve injury in vivo. CGF was prepared from venous blood taken from rats, and using scanning electron microscopy (SEM) we noted that it featured a fiber‑like appearance with pore size ranging from 0.1 to 1.0 µm. The soluble component of CGF was used to produce conditioned media with which to treat the Schwann cell line. A cell counting kit-8 assay and cell cycle analysis were both used to study the proliferative effect of CGF on SCs. Reverse transcription-quantitative PCR and western blot analysis demonstrated that there was an increase in the mRNA and protein expression of NGF and GDNF, both of which are markers of SC neurotrophic secretion. A model of sciatic nerve crush injury was established for the in vivo experiment, and CGF was found to increase the sciatic functional index (indicative of nerve function). We noted that CGF increased SC proliferation and secretion of neurotrophic factors in vitro, and promoted functional recovery after peripheral nerve injuries in vivo. These results suggest that CGF is a promising candidate biomaterial for peripheral nerve regeneration, and may potentially be utilized to repair nerve injuries.