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The fusion of tissue spheroids attached to pre-stretched electrospun polyurethane scaffolds.

Beachley V, Kasyanov V, Nagy-Mehesz A, Norris R, Ozolanta I, Kalejs M, Stradins P, Baptista L, da Silva K, Grainjero J, Wen X, Mironov V - J Tissue Eng (2014)

Bottom Line: Tissue spheroids attached, spread, and fused after being placed on pre-stretched polyurethane electrospun matrices and formed tissue constructs.Efforts to eliminate hole defects with fibrogenic tissue growth factor-β resulted in the increased synthesis of collagen and periostin and a dramatic reduction in hole size and number.In control experiments, tissue spheroids fuse on a non-adhesive hydrogel and form continuous tissue constructs without holes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA.

ABSTRACT
Effective cell invasion into thick electrospun biomimetic scaffolds is an unsolved problem. One possible strategy to biofabricate tissue constructs of desirable thickness and material properties without the need for cell invasion is to use thin (<2 µm) porous electrospun meshes and self-assembling (capable of tissue fusion) tissue spheroids as building blocks. Pre-stretched electrospun meshes remained taut in cell culture and were able to support tissue spheroids with minimal deformation. We hypothesize that elastic electrospun scaffolds could be used as temporal support templates for rapid self-assembly of cell spheroids into higher order tissue structures, such as engineered vascular tissue. The aim of this study was to investigate how the attachment of tissue spheroids to pre-stretched polyurethane scaffolds may interfere with the tissue fusion process. Tissue spheroids attached, spread, and fused after being placed on pre-stretched polyurethane electrospun matrices and formed tissue constructs. Efforts to eliminate hole defects with fibrogenic tissue growth factor-β resulted in the increased synthesis of collagen and periostin and a dramatic reduction in hole size and number. In control experiments, tissue spheroids fuse on a non-adhesive hydrogel and form continuous tissue constructs without holes. Our data demonstrate that tissue spheroids attached to thin stretched elastic electrospun scaffolds have an interrupted tissue fusion process. The resulting tissue-engineered construct phenotype is a direct outcome of the delicate balance of the competing physical forces operating during the tissue fusion process at the interface of the pre-stretched elastic scaffold and the attached tissue spheroids. We have shown that with appropriate treatments, this process can be modulated, and thus, a thin pre-stretched elastic polyurethane electrospun scaffold could serve as a supporting template for rapid biofabrication of thick tissue-engineered constructs without the need for cell invasion.

No MeSH data available.


Related in: MedlinePlus

Tissue spheroids behavior on pre-stretched electrospun polyurethane scaffolds. (a) Single tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (b) Three fused tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (c) Seven fused tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (d) Tissue spheroid on electrospun polyurethane scaffold. Tissue spheroid imposes traction forces on electrospun scaffold and changes original orientation of polyurethane fibers in centripetal direction. The original size and counters of tissue spheroid before spreading are outlined by dotted line. Scale bar—300 µm. (e) Adhesion of tissue spheroids to electrospun matrix—scanning electron microscopy.
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fig3-2041731414556561: Tissue spheroids behavior on pre-stretched electrospun polyurethane scaffolds. (a) Single tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (b) Three fused tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (c) Seven fused tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (d) Tissue spheroid on electrospun polyurethane scaffold. Tissue spheroid imposes traction forces on electrospun scaffold and changes original orientation of polyurethane fibers in centripetal direction. The original size and counters of tissue spheroid before spreading are outlined by dotted line. Scale bar—300 µm. (e) Adhesion of tissue spheroids to electrospun matrix—scanning electron microscopy.

Mentions: Tissue spheroids do not fall through the electrospun scaffold due to their relatively large size (300–400 µm) and therefore attached and spread on the scaffold surface (Figure 3). Two, three, and seven closely placed tissue spheroids attached to the electrospun scaffold and underwent fusion to form a thick confluent tissue layer (Figure 3(a)–(c)). Therefore, small tissue-engineered constructs could be biofabricated from a small number of tissue spheroids to form a confluent tissue layer without any holes. It has also been demonstrated that tissue spheroids can not only attach but also spread on electrospun matrices and change orientation of nanofibers by imposing traction forces (Figure 3(d)). Scanning electron microscopy demonstrates close interaction of tissue spheroids with electrospun matrices and incorporation of some electrospun fibers (Figure 3(e)). However, the fusion of 50 closely placed tissue spheroids attached to an electrospun scaffold resulted in the formation of a non-confluent tissue layer with holes of different diameters and shape (Figure 4(a) and (b)). The addition of second and third layers of tissue spheroids did not eliminate or close these observed holes. Moreover, in this case, the preexisting holes evolved into larger crater-like structures (Figure 4(c)). Increasing the cultivation time to 2 weeks also failed to eliminate the holes. Tissue spheroids placed on pre-stretched electrospun porous PU scaffolds fuse into tissue-engineered constructs with pores or one perforated tissue layer of fused tissue spheroids. The appearance of holes strongly correlates with an increased number of tissue spheroids forming the tissue construct.


The fusion of tissue spheroids attached to pre-stretched electrospun polyurethane scaffolds.

Beachley V, Kasyanov V, Nagy-Mehesz A, Norris R, Ozolanta I, Kalejs M, Stradins P, Baptista L, da Silva K, Grainjero J, Wen X, Mironov V - J Tissue Eng (2014)

Tissue spheroids behavior on pre-stretched electrospun polyurethane scaffolds. (a) Single tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (b) Three fused tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (c) Seven fused tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (d) Tissue spheroid on electrospun polyurethane scaffold. Tissue spheroid imposes traction forces on electrospun scaffold and changes original orientation of polyurethane fibers in centripetal direction. The original size and counters of tissue spheroid before spreading are outlined by dotted line. Scale bar—300 µm. (e) Adhesion of tissue spheroids to electrospun matrix—scanning electron microscopy.
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Related In: Results  -  Collection

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fig3-2041731414556561: Tissue spheroids behavior on pre-stretched electrospun polyurethane scaffolds. (a) Single tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (b) Three fused tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (c) Seven fused tissue spheroids attached to the electrospun polyurethane scaffold (arrows indicate the areas of attachment-dependent cell and tissue spreading). Scale bar—300 µm. (d) Tissue spheroid on electrospun polyurethane scaffold. Tissue spheroid imposes traction forces on electrospun scaffold and changes original orientation of polyurethane fibers in centripetal direction. The original size and counters of tissue spheroid before spreading are outlined by dotted line. Scale bar—300 µm. (e) Adhesion of tissue spheroids to electrospun matrix—scanning electron microscopy.
Mentions: Tissue spheroids do not fall through the electrospun scaffold due to their relatively large size (300–400 µm) and therefore attached and spread on the scaffold surface (Figure 3). Two, three, and seven closely placed tissue spheroids attached to the electrospun scaffold and underwent fusion to form a thick confluent tissue layer (Figure 3(a)–(c)). Therefore, small tissue-engineered constructs could be biofabricated from a small number of tissue spheroids to form a confluent tissue layer without any holes. It has also been demonstrated that tissue spheroids can not only attach but also spread on electrospun matrices and change orientation of nanofibers by imposing traction forces (Figure 3(d)). Scanning electron microscopy demonstrates close interaction of tissue spheroids with electrospun matrices and incorporation of some electrospun fibers (Figure 3(e)). However, the fusion of 50 closely placed tissue spheroids attached to an electrospun scaffold resulted in the formation of a non-confluent tissue layer with holes of different diameters and shape (Figure 4(a) and (b)). The addition of second and third layers of tissue spheroids did not eliminate or close these observed holes. Moreover, in this case, the preexisting holes evolved into larger crater-like structures (Figure 4(c)). Increasing the cultivation time to 2 weeks also failed to eliminate the holes. Tissue spheroids placed on pre-stretched electrospun porous PU scaffolds fuse into tissue-engineered constructs with pores or one perforated tissue layer of fused tissue spheroids. The appearance of holes strongly correlates with an increased number of tissue spheroids forming the tissue construct.

Bottom Line: Tissue spheroids attached, spread, and fused after being placed on pre-stretched polyurethane electrospun matrices and formed tissue constructs.Efforts to eliminate hole defects with fibrogenic tissue growth factor-β resulted in the increased synthesis of collagen and periostin and a dramatic reduction in hole size and number.In control experiments, tissue spheroids fuse on a non-adhesive hydrogel and form continuous tissue constructs without holes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Rowan University, Glassboro, NJ, USA.

ABSTRACT
Effective cell invasion into thick electrospun biomimetic scaffolds is an unsolved problem. One possible strategy to biofabricate tissue constructs of desirable thickness and material properties without the need for cell invasion is to use thin (<2 µm) porous electrospun meshes and self-assembling (capable of tissue fusion) tissue spheroids as building blocks. Pre-stretched electrospun meshes remained taut in cell culture and were able to support tissue spheroids with minimal deformation. We hypothesize that elastic electrospun scaffolds could be used as temporal support templates for rapid self-assembly of cell spheroids into higher order tissue structures, such as engineered vascular tissue. The aim of this study was to investigate how the attachment of tissue spheroids to pre-stretched polyurethane scaffolds may interfere with the tissue fusion process. Tissue spheroids attached, spread, and fused after being placed on pre-stretched polyurethane electrospun matrices and formed tissue constructs. Efforts to eliminate hole defects with fibrogenic tissue growth factor-β resulted in the increased synthesis of collagen and periostin and a dramatic reduction in hole size and number. In control experiments, tissue spheroids fuse on a non-adhesive hydrogel and form continuous tissue constructs without holes. Our data demonstrate that tissue spheroids attached to thin stretched elastic electrospun scaffolds have an interrupted tissue fusion process. The resulting tissue-engineered construct phenotype is a direct outcome of the delicate balance of the competing physical forces operating during the tissue fusion process at the interface of the pre-stretched elastic scaffold and the attached tissue spheroids. We have shown that with appropriate treatments, this process can be modulated, and thus, a thin pre-stretched elastic polyurethane electrospun scaffold could serve as a supporting template for rapid biofabrication of thick tissue-engineered constructs without the need for cell invasion.

No MeSH data available.


Related in: MedlinePlus