Current progress in application of polymeric nanofibers to tissue engineering.

Tissue engineering uses a combination of cell biology, chemistry, and biomaterials to fabricate three dimensional (3D) tissues that mimic the architecture of extracellular matrix (ECM) comprising diverse interwoven nanofibrous structure. Among several methods for producing nanofibrous scaffolds, electrospinning has gained intense interest because it can make nanofibers with a porous structure and high specific surface area. The processing and solution parameters of electrospinning can considerably affect the assembly and structural morphology of the fabricated nanofibers. Electrospun nanofibers can be made from natural or synthetic polymers and blending them is a straightforward way to tune the functionality of the nanofibers. Furthermore, the electrospun nanofibers can be functionalized with various surface modification strategies. In this review, we highlight the latest achievements in fabricating electrospun nanofibers and describe various ways to modify the surface and structure of scaffolds to promote their functionality. We also summarize the application of advanced polymeric nanofibrous scaffolds in the regeneration of human bone, cartilage, vascular tissues, and tendons/ligaments.

Multipotency expression of human adipose stem cells in filament-like alginate and gelatin derivative hydrogel fabricated through visible light-initiated crosslinking.

Hydrogel fibers are structurally and biologically useful devices for differentiation of stem cells and fabrication of filament-like tissues. We established cell-laden degradable hydrogel fibers through visible light-initiated crosslinking to differentiate stem cells and fabricate filament-like tissue. Human adipose stem cell (hADSC)-laden fibers were fabricated by cross-linking phenolic-substituted alginate and gelatin (Alg-Ph and Gela-Ph respectively) in an aqueous solution containing cells. The crosslinking of phenolic moieties was mediated by ruthenium(II) tris-bipyridyl dication (Ru(II) bpy and sodium ammonium persulfate (SPS) and irradiating visible light. The hydrogel microfiber fabricated with desirable geometries and dimensions. The encapsulated hADSCs proliferated and grew within hydrogel microfiber, maintained their multipotency ability and formed filament-like constructs. The filament-like tissues covered with an additional heterogeneous cell layer was made by degrading the fiber membrane using alginate-lyase after covering the fiber surface with vascular endothelial cells. Cellular viability is preserved during Alg-Ph and Gela-Ph hydrogel fiber fabrication and filament-like tissue formation. These results demonstrate the feasibility of Alg-based hydrogel fibers obtained through the Ru/SPS-mediated crosslinking system and visible light irradiation for the engineering of filament-like tissues and cell-based therapeutic treatments.

Encapsulation of rat cardiomyoblasts with alginate-gelatin microspheres preserves stemness feature in vitro.

INTRODUCTION: The emergence of numerous tissue engineering and regenerative medicine techniques cell encapsulation paves a way to heal and restore the function of various injured tissues mainly cardiovascular system. Here, we aimed to investigate the role of alginate-gelatin encapsulation on the dynamic of rat cardiomyoblasts in vitro. MATERIALS AND METHODS: Rat cardiomyoblasts cell line H9C2 were enclosed by using alginate-gelatin microspheres and incubated for 7 days. MTT method was used to examine cell viability. The level of genes associated with cardiomyoblasts maturation MYL7, NPPA, NKX2-5, and GATA4 real-time PCR. ELISA was used to measure the protein levels of Bcl-2 and Bax factor post-encapsulation. The level of SOD, GPx, and TAC was detected by biochemical analyses. Western blotting was performed to measure the content of AMP-activated protein kinase. RESULTS: We found that encapsulation was able to increase the viability of rat cardiomyocytes after 7 days. The decreased level of Bcl-2 (p < 0.001) coincided with non-significant differences in the level of Bax (p > 0.05). The transcription level of all genes MYL7, NPPA, NKX2-5, and GATA4 were found to down-regulate compared to the control non-treated cells (p < 0.05). No significant differences were found regarding the level of SOD, GPx, and TAC compared to the control (p>0.05). According to western blotting, revealed a reduced level of AMPK following 7-day incubation of rat cardiomyoblasts (p < 0.05). CONCLUSION: Data confirmed that the encapsulation of rat cardiomyoblasts with alginate-gelatin microspheres maintained the cells multipotentiality.

The effect of alginate-gelatin encapsulation on the maturation of human myelomonocytic cell line U937.

Today, many attempts have been collected in the field of tissue engineering for reconstitution of injured bone marrow capacity by transplantation of functional cell source. By having a three-dimensional condition, microcapsules are appropriate candidates for cells transplantation to target sites. Here, we examined the effect of alginate-gelatin microcapsules on functional maturation of human myelomonocytic cell line U937 after 7 days in vitro. U937 cells were encapsulated by the mixture of alginate-gelatin and cultured for 7 days. Trypan blue staining was used to show cell survival rate. Morphological changes were determined by haematoxylin and eosin staining. The expression of monocyte (CD14) and leukocyte (CD33) factors were measured by flow cytometry. The functional maturation of encapsulated cells was shown by immunocytochemistry targeting myeloperoxidase (MPO) activity and level of CD68. Transcription level of adhesion molecules CD68L, CD18, CD11b, and CD49d/VLA was detected by real-time polymerase chain reaction. In vivo constitutive capacity of encapsulated U937 was investigated in rabbits via administration to bone marrow. We showed enhanced U937 viability and monocyte and band cell-like appearance 7 days after encapsulation. These changes coincided with increasing CD33 and CD14 levels and a decrease of CD15, confirming cell maturation (p < 0.05). High level of MPO and CD68-positive cells showed the functional maturation of U937 cells into neutrophils and macrophages. Compared with that of nonencapsulated cells, the level of adhesion factor was up-regulated. We found labelled cells in the peripheral blood after cell transplantation to bone marrow. These data suggest that alginate-gelatin encapsulation of U937 cells promotes functional leukopoiesis and monocytopoiesis.

Alginate-gelatin encapsulation of human endothelial cells promoted angiogenesis in in vivo and in vitro milieu.

Up to present, many advantages have been achieved in the field of cell-based therapies by applying sophisticated methodologies and delivery approaches. Microcapsules are capable to provide safe microenvironment for cells during transplantation in a simulated physiological 3D milieu. Here, we aimed to investigate the effect of alginate-gelatin encapsulation on angiogenic behavior of human endothelial cells over a period of 5 days. Human umbilical vein endothelial cells were encapsulated by alginate-gelatin substrate and incubated for 5 days. MTT and autophagy PCR array analysis were used to monitor cell survival rate. For in vitro angiogenesis analysis, cell distribution of Tie-1, Tie-2, VEGFR-1, and VEGFR-2 were detected by ELISA. In addition to in vitro tubulogenesis assay, we monitored the expression of VE-cadherin by Western blotting. The migration capacity of encapsulated HUVECs was studied by measuring MMP-2 and MMP-9 via gelatin zymography. The in vivo angiogenic potential of encapsulated HUVECs was analyzed in immune-compromised mouse implant model during 7 days post-transplantation. We demonstrated that encapsulation promoted HUVECs cell survival and proliferation. Compared to control, no significant differences were observed in autophagic status of encapsulated cells (p > 0.05). The level of Tie-1, Tie-2, VEGFR-1, and VEGFR-2 were increased, but did not reach to significant levels. Encapsulation decreased MMP-2, -9 activity and increased the VE-cadherin level in enclosed cells (p < 0.05). Moreover, an enhanced in vivo angiogenic response of encapsulated HUVECs was evident as compared to non-capsulated cells (p < 0.05). These observations suggest that alginate-gelatin encapsulation can induce angiogenic response in in vivo and in vitro conditions.

Barium-cross-linked alginate-gelatine microcapsule as a potential platform for stem cell production and modular tissue formation.

Influence of gelatine concentration and cross-linker ions of Ca2+ and Ba2+ was evaluated on characteristics of alginate hydrogels and proliferation behaviours of model adherent and suspendable stem cells of fibroblast and U937 embedded in alginate microcapsules. Increasing gelatine concentration to 2.5% increased extent of swelling to 15% and 25% for barium- and calcium-cross-linked hydrogels, respectively. Mechanical properties also decreased with increasing swelling of hydrogels. Both by increasing gelatine concentration and using barium ions increased considerably the proliferation of encapsulated model stem cells. Barium-cross-linked alginate-gelatine microcapsule tested for bone building block showed a 13.5 ± 1.5-fold expansion for osteoblast cells after 21 days with deposition of bone matrix. The haematopoietic stem cells cultured in the microcapsule after 7 days also showed up to 2-fold increase without adding any growth factor. The study demonstrates that barium-cross-linked alginate-gelatine microcapsule has potential for use as a simple and efficient 3D platform for stem cell production and modular tissue formation.