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The Hygroscopic Opening of Sesame Fruits Is Induced by a Functionally Graded Pericarp Architecture.

ABSTRACT: To enhance the distribution of their seeds, plants often utilize hygroscopic deformations that actuate dispersal mechanisms. Such movements are based on desiccation-induced shrinkage of tissues in predefined directions. The basic hygroscopic deformations are typically actuated by a bi-layer configuration, in which shrinking of an active tissue layer is resisted by a stiff layer, generating a set of basic movements including bending, coiling, and twisting. In this study, we investigate a new type of functionally graded hygroscopic movement in the fruit (capsule) of sesame (Sesamum indicum L.). Microscopic observations of the capsules showed that the inner stiff endocarp layer is built of a bilayer of transverse (i.e., circumferential) and longitudinal fiber cells with the layers positioned in a semi-circle, one inside the other. The outer mesocarp layer is made of soft parenchyma cells. The thickness of the fibrous layers and of the mesocarp exhibits a graded architecture, with gradual changes in their thickness around the capsule circumference. The cellulose microfibrils in the fiber cell walls are lying parallel to the cell long axis, rendering them stiff. The outer mesocarp layer contracted by 300% as it dried. Removal of this outer layer inhibited the opening movement, indicating that it is the active tissue. A biomechanical hygro-elastic model based on the relative thicknesses of the layers successfully simulated the opening curvature. Our findings suggest that the sesame capsules possess a functionally graded architecture, which promotes a non-uniform double-curvature hygroscopic bending movement. In contrast to other hygroscopic organs described in the literature, the sesame capsule actuating and resisting tissues are not uniform throughout the device, but changing gradually. This newly described mechanism can be exploited in bio-inspired designs of novel actuating platforms.

SUBMITTER: Shtein I

PROVIDER: S-EPMC5056167 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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The Hygroscopic Opening of Sesame Fruits Is Induced by a Functionally Graded Pericarp Architecture.

Shtein Ilana I Elbaum Rivka R Bar-On Benny B

Frontiers in plant science 20161010

To enhance the distribution of their seeds, plants often utilize hygroscopic deformations that actuate dispersal mechanisms. Such movements are based on desiccation-induced shrinkage of tissues in predefined directions. The basic hygroscopic deformations are typically actuated by a bi-layer configuration, in which shrinking of an active tissue layer is resisted by a stiff layer, generating a set of basic movements including bending, coiling, and twisting. In this study, we investigate a new type ...[more]

PMID: 27777579

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Project description:Osteochondral tissue repair remains a significant challenge in orthopedic surgery. Tissue engineering of osteochondral tissue has transpired as a potential therapeutic solution as it can effectively regenerate bone, cartilage, and the bone-cartilage interface. While advancements in scaffold fabrication and stem cell engineering have made significant progress towards the engineering of composite tissues, such as osteochondral tissue, new approaches are required to improve the outcome of such strategies. Herein, we discuss the use of a single-unit trilayer scaffold with depth-varying pore architecture and mineral environment to engineer osteochondral tissues in vivo. The trilayer scaffold includes a biomineralized bottom layer mimicking the calcium phosphate (CaP)-rich bone microenvironment, a cryogel middle layer with anisotropic pore architecture, and a hydrogel top layer. The mineralized bottom layer was designed to support bone formation, while the macroporous middle layer and hydrogel top layer were designed to support cartilage tissue formation. The bottom layer was kept acellular and the top two layers were loaded with cells prior to implantation. When implanted in vivo, these trilayer scaffolds resulted in the formation of osteochondral tissue with a lubricin-rich cartilage surface. The osteochondral tissue formation was a result of continuous differentiation of the transplanted cells to form cartilage tissue and recruitment of endogenous cells through the mineralized bottom layer to form bone tissue. Our results suggest that integrating exogenous cell-based cartilage tissue engineering along with scaffold-driven in situ bone tissue engineering could be a powerful approach to engineer analogs of osteochondral tissue. In addition to offering new therapeutic opportunities, such approaches and systems could also advance our fundamental understanding of osteochondral tissue regeneration and repair. STATEMENT OF SIGNIFICANCE:In this work, we describe the use of a single-unit trilayer scaffold with depth-varying pore architecture and mineral environment to engineer osteochondral tissues in vivo. The trilayer scaffold was designed to support continued differentiation of the donor cells to form cartilage tissue while supporting bone formation through recruitment of endogenous cells. When implanted in vivo, these trilayer scaffolds partially loaded with cells resulted in the formation of osteochondral tissue with a lubricin-rich cartilage surface. Approaches such as the one presented here that integrates ex vivo tissue engineering along with endogenous cell-mediated tissue engineering can have a significant impact in tissue engineering composite tissues with diverse cell populations and functionality.

Dataset Information

The Hygroscopic Opening of Sesame Fruits Is Induced by a Functionally Graded Pericarp Architecture.

Publications

The Hygroscopic Opening of Sesame Fruits Is Induced by a Functionally Graded Pericarp Architecture.

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