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A Structurally and Functionally Biomimetic Biphasic Scaffold for Intervertebral Disc Tissue Engineering.

Choy AT, Chan BP - PLoS ONE (2015)

Bottom Line: On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc.Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery.However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs.

View Article: PubMed Central - PubMed

Affiliation: Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China.

ABSTRACT
Tissue engineering offers high hopes for the treatment of intervertebral disc (IVD) degeneration. Whereas scaffolds of the disc nucleus and annulus have been extensively studied, a truly biomimetic and mechanically functional biphasic scaffold using naturally occurring extracellular matrix is yet to be developed. Here, a biphasic scaffold was fabricated with collagen and glycosaminoglycans (GAGs), two of the most abundant extracellular matrix components in the IVD. Following fabrication, the scaffold was characterized and benchmarked against native disc. The biphasic scaffold was composed of a collagen-GAG co-precipitate making up the nucleus pulposus-like core, and this was encapsulated in multiple lamellae of photochemically crosslinked collagen membranes comprising the annulus fibrosus-like lamellae. On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc. The annulus-independent nature of disc height recovery suggests that the fluid replacement function of the engineered nucleus pulposus core might mimic this hitherto unique feature of native disc. Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery. However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs. This study contributes to the rationalized design and development of a biomimetic and mechanically viable biphasic scaffold for IVD tissue engineering.

No MeSH data available.


Related in: MedlinePlus

Histomorphometric and ultrastructural characterization of the fabricated biphasic scaffold and native disc.(A-D) Fabricated biphasic scaffold and (E-H) native disc; (A&E) Alcian blue staining and (B&F) immunohistochemistry of type I collagen. (C-D & G&H) SEM images. (C) AF-like collagen lamellae; (D) NP-like core with compaction; (D1) NP-like core without compaction; (G) AF lamellae in the native disc; (H) NP core in the native disc. Scale bars are 500 μm (for A-B & E-F); 10 μm (for C&G); 1 μm (for G1) and 500 nm (for D-D1&H).
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pone.0131827.g004: Histomorphometric and ultrastructural characterization of the fabricated biphasic scaffold and native disc.(A-D) Fabricated biphasic scaffold and (E-H) native disc; (A&E) Alcian blue staining and (B&F) immunohistochemistry of type I collagen. (C-D & G&H) SEM images. (C) AF-like collagen lamellae; (D) NP-like core with compaction; (D1) NP-like core without compaction; (G) AF lamellae in the native disc; (H) NP core in the native disc. Scale bars are 500 μm (for A-B & E-F); 10 μm (for C&G); 1 μm (for G1) and 500 nm (for D-D1&H).

Mentions: Following the mechanical tests, the fabricated biphasic scaffold and native IVD constructs were sectioned and stained with either Alcian blue or an antibody against type I collagen. The histological and ultrastructure appearance of a biphasic scaffold comprised of 4 layers of AF-like collagen lamellae as shown in Fig 4A–4D, while the same characterization in native discs is shown in Fig 4E–4H. Whereas the biphasic scaffolds did not have the endplate-vertebrae structure of the native discs (Fig 4E and 4F), the dimensions and structure of both were comparable, except that the AF region in the biphasic scaffolds was thinner, being comprised of just 4 layers of collagen lamellae (Fig 4A and 4B), when compared with the 15–40 layers in native discs (Fig 4E and 4F). In the biphasic IVD scaffold, the GAG-rich NP scaffold was surrounded by an AF-like multi-lamellae structure, with a clear boundary. The NP scaffold was intensely stained with Alcian blue, indicating the successful retention of GAGs within the collagen fibrous meshwork after both the fabrication process and the mechanical test. On the other hand, the AF scaffold was not stained with the dye, and appeared pink due to the photosensitizer (Fig 4A). Immunohistology of type I collagen showed positive staining throughout the fabricated constructs (Fig 4B). In comparison, the native disc showed a typical GAG-rich NP core surrounded by multiple AF lamellae (Fig 4E and 4F), while type I collagen was mainly confined to the AF region (Fig 4F). Ultrastructural analysis of the fabricated scaffolds demonstrated that the AF region consisted of multiple interconnected lamellae structures when viewed at low magnification (Fig 4C). At higher magnification (see insert, Fig 4C1), these structures were resolved as randomly oriented, nano-sized collagen fibers. On the other hand, the AF lamellae in the native disc consisted of well-organized fibers (Fig 4G) with nano-sized fibrils (Fig 4G1), which are of comparable dimension to those found in the AF region of the biphasic scaffolds (compare Fig 4G1 with Fig 4C1). Ultrastructural analysis of the NP core in the fabricated scaffold showed thick and aggregated fibrous collagen structures intercalating with bead-like structures, which correspond to the co-precipitated GAGs (Fig 4D). For comparison, the insert (Fig 4D1) clearly shows the bead-like GAG structures in samples prior to the compaction procedure during fabrication. The NP region of the native disc showed well organized strings of fibrils covered with numerous bead-like GAG structures (Fig 4H), which were also present in the collagen-GAG NP-like core of the biphasic structure (Fig 4D1).


A Structurally and Functionally Biomimetic Biphasic Scaffold for Intervertebral Disc Tissue Engineering.

Choy AT, Chan BP - PLoS ONE (2015)

Histomorphometric and ultrastructural characterization of the fabricated biphasic scaffold and native disc.(A-D) Fabricated biphasic scaffold and (E-H) native disc; (A&E) Alcian blue staining and (B&F) immunohistochemistry of type I collagen. (C-D & G&H) SEM images. (C) AF-like collagen lamellae; (D) NP-like core with compaction; (D1) NP-like core without compaction; (G) AF lamellae in the native disc; (H) NP core in the native disc. Scale bars are 500 μm (for A-B & E-F); 10 μm (for C&G); 1 μm (for G1) and 500 nm (for D-D1&H).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4482706&req=5

pone.0131827.g004: Histomorphometric and ultrastructural characterization of the fabricated biphasic scaffold and native disc.(A-D) Fabricated biphasic scaffold and (E-H) native disc; (A&E) Alcian blue staining and (B&F) immunohistochemistry of type I collagen. (C-D & G&H) SEM images. (C) AF-like collagen lamellae; (D) NP-like core with compaction; (D1) NP-like core without compaction; (G) AF lamellae in the native disc; (H) NP core in the native disc. Scale bars are 500 μm (for A-B & E-F); 10 μm (for C&G); 1 μm (for G1) and 500 nm (for D-D1&H).
Mentions: Following the mechanical tests, the fabricated biphasic scaffold and native IVD constructs were sectioned and stained with either Alcian blue or an antibody against type I collagen. The histological and ultrastructure appearance of a biphasic scaffold comprised of 4 layers of AF-like collagen lamellae as shown in Fig 4A–4D, while the same characterization in native discs is shown in Fig 4E–4H. Whereas the biphasic scaffolds did not have the endplate-vertebrae structure of the native discs (Fig 4E and 4F), the dimensions and structure of both were comparable, except that the AF region in the biphasic scaffolds was thinner, being comprised of just 4 layers of collagen lamellae (Fig 4A and 4B), when compared with the 15–40 layers in native discs (Fig 4E and 4F). In the biphasic IVD scaffold, the GAG-rich NP scaffold was surrounded by an AF-like multi-lamellae structure, with a clear boundary. The NP scaffold was intensely stained with Alcian blue, indicating the successful retention of GAGs within the collagen fibrous meshwork after both the fabrication process and the mechanical test. On the other hand, the AF scaffold was not stained with the dye, and appeared pink due to the photosensitizer (Fig 4A). Immunohistology of type I collagen showed positive staining throughout the fabricated constructs (Fig 4B). In comparison, the native disc showed a typical GAG-rich NP core surrounded by multiple AF lamellae (Fig 4E and 4F), while type I collagen was mainly confined to the AF region (Fig 4F). Ultrastructural analysis of the fabricated scaffolds demonstrated that the AF region consisted of multiple interconnected lamellae structures when viewed at low magnification (Fig 4C). At higher magnification (see insert, Fig 4C1), these structures were resolved as randomly oriented, nano-sized collagen fibers. On the other hand, the AF lamellae in the native disc consisted of well-organized fibers (Fig 4G) with nano-sized fibrils (Fig 4G1), which are of comparable dimension to those found in the AF region of the biphasic scaffolds (compare Fig 4G1 with Fig 4C1). Ultrastructural analysis of the NP core in the fabricated scaffold showed thick and aggregated fibrous collagen structures intercalating with bead-like structures, which correspond to the co-precipitated GAGs (Fig 4D). For comparison, the insert (Fig 4D1) clearly shows the bead-like GAG structures in samples prior to the compaction procedure during fabrication. The NP region of the native disc showed well organized strings of fibrils covered with numerous bead-like GAG structures (Fig 4H), which were also present in the collagen-GAG NP-like core of the biphasic structure (Fig 4D1).

Bottom Line: On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc.Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery.However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs.

View Article: PubMed Central - PubMed

Affiliation: Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China.

ABSTRACT
Tissue engineering offers high hopes for the treatment of intervertebral disc (IVD) degeneration. Whereas scaffolds of the disc nucleus and annulus have been extensively studied, a truly biomimetic and mechanically functional biphasic scaffold using naturally occurring extracellular matrix is yet to be developed. Here, a biphasic scaffold was fabricated with collagen and glycosaminoglycans (GAGs), two of the most abundant extracellular matrix components in the IVD. Following fabrication, the scaffold was characterized and benchmarked against native disc. The biphasic scaffold was composed of a collagen-GAG co-precipitate making up the nucleus pulposus-like core, and this was encapsulated in multiple lamellae of photochemically crosslinked collagen membranes comprising the annulus fibrosus-like lamellae. On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc. The annulus-independent nature of disc height recovery suggests that the fluid replacement function of the engineered nucleus pulposus core might mimic this hitherto unique feature of native disc. Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery. However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs. This study contributes to the rationalized design and development of a biomimetic and mechanically viable biphasic scaffold for IVD tissue engineering.

No MeSH data available.


Related in: MedlinePlus