Composite tissue-engineered intervertebral tissue was assembled in the shape of cylindrical disks composed of an outer shell of PGA mesh seeded with annulus fibrosus cells with an inner core of nucleus pulposus cells seeded into an alginate gel. Samples were implanted subcutaneously in athymic mice and retrieved at time points up to 16 weeks. At all retrieval times, samples maintained shape and contained regions of distinct tissue formation. Histology revealed progressive tissue formation with distinct morphological differences in tissue formation in regions seeded with annulus fibrosus and nucleus pulposus cells. Biochemical analysis indicated that DNA, proteoglycan, and collagen content in tissue-engineered discs increased with time, reaching >50% of the levels of native tissue by 16 weeks. The exception to this was the collagen content of the nucleus pulposus portion of the implants with were approximately 15% of native values. The equilibrium modulus of tissue-engineered discs was 49.0+/-13.2 kPa at 16 weeks, which was between the measured values for the modulus of annulus fibrosus and nucleus pulposus. The hydraulic permeability of tissue-engineered discs was 5.1+/-1.7x10(-14) m2/Pa at 16 weeks, which was between the measured values for the hydraulic permeability of annulus fibrosus and nucleus pulposus. These studies document the feasibility of creating composite tissue-engineered intevertebral disc implants with similar composition and mechanical properties to native tissue.
"Similarly, heterogeneity of MSCs originated from different donors has already been reported (Karp and Leng Teo, 2009). Increase of proteoglycan content has gained particular note, because it has been shown to be important for functional compressive and mechanical properties (Kisiday et al., 2002; Mizuno et al., 2006), although the role of collagen type II is more prominent (Huang et al., 2008). It is important to consider that a low cell seeding density of 1 Â 10 7 cells/mL was used here to specifically examine the effect of the biomaterial on cell behaviour. "
[Show abstract][Hide abstract] ABSTRACT: Chitosan-beta glycerophosphate-hydroxyethyl cellulose (CH-GP-HEC) is a biocompatible and biodegradable scaffold exhibiting a sol-gel transition at 37°C. Chondrogenic factors or mesenchymal stem cells (MSCs) can be included in the CH-GP-HEC, and injected into the site of injury to fill the cartilage tissue defects with minimal invasion and pain. The possible impact of the injectable CH-GP-HEC on the viability of the encapsulated MSCs was assessed by propidium iodide-fluorescein diacetate (PI-FDA) staining. Proliferation of the human and rat MSCs was also determined by MTS assay on days 0, 7, 14, and 28 after encapsulation. To investigate the potential application of CH-GP-HEC as a drug delivery device, the in vitro release profile of insulin was quantified by QuantiPro-BCA(TM) protein assay. Chondrogenic differentiation capacity of the encapsulated human MSCs (hMSCs) was also determined after induction of differentiation with transforming growth factor β3 (TGF-β3). MSCs have very good survival and proliferative rates within CH-GP-HEC hydrogel during the 28 day investigation. A sustained release of insulin occurred over 8 days. The CH-GP-HEC hydrogel also provided suitable conditions for chondrogenic differentiation of the encapsulated hMSCs. In conclusion the high potential of CH-GP-HEC as an injectable hydrogel for cartilage tissue engineering is emphasised.
Cell Biology International 01/2014; 38(1). DOI:10.1002/cbin.10181 · 1.93 Impact Factor
"More research is required to integrate all IVD structures. Other studies (Mizuno et al., 2006; Nerurkar et al., 2008) developed an interesting strategy to replicate the microstructural organization of AF by using scaffolds made of aligned PCL nanofibers. The centre of the PCL scaffold was filled with agarose to resemble NP. "
"(E) Polarized light micrograph of an electrospun poly(e-caprolactone) (PCL) nanofibrous scaffold oriented in opposing bilayers (+30°/−30°) seeded with mesenchymal stem cells which elaborate aligned intra-lamellar collagen that recapitulates the gross fiber orientation of the native AF (Nerukar et al., 2009). Scale: 200 µm (F) Composite whole disc equivalent comprised of NP cells encapsulated in an alginate hydrogel surrounded by a reinforced poly(glycolic acid) mesh seeded with AF cells (Mizuno et al., 2006). (G) Disc-like angle-ply structure constructed from PCL nanofibers oriented at +30°/−30° to mimic the AF with a central agarose hydrogel core serving as an NP analog (Nerukar et al., 2010). "
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND CONTEXT: Degeneration and injuries of the intervertebral disc (IVD) result in large alterations in biomechanical behaviors. Repair strategies using biomaterials can be optimized based on the biomechanical and biological requirements of the IVD. PURPOSE: To review the present literature on the effects of degeneration, simulated degeneration, and injury on biomechanics of the IVD, with special attention paid to needle puncture injuries, which are a pathway for diagnostics and regenerative therapies and the promising biomaterials for disc repair with a focus on how those biomaterials may promote biomechanical repair. STUDY DESIGN: A narrative review to evaluate the role of biomechanics on disc degeneration and regenerative therapies with a focus on what biomechanical properties need to be repaired and how to evaluate and accomplish such repairs using biomaterials. Model systems for the screening of such repair strategies are also briefly described. METHODS: Articles were selected from two main PubMed searches using keywords: intervertebral AND biomechanics (1,823 articles) and intervertebral AND biomaterials (361 articles). Additional keywords (injury, needle puncture, nucleus pressurization, biomaterials, hydrogel, sealant, tissue engineering) were used to narrow the articles down to the topics most relevant to this review. RESULTS: Degeneration and acute disc injuries have the capacity to influence nucleus pulposus (NP) pressurization and annulus fibrosus (AF) integrity, which are necessary for an effective disc function and, therefore, require repair. Needle injection injuries are of particular clinical relevance with the potential to influence disc biomechanics, cellularity, and metabolism, yet these effects are localized or small and more research is required to evaluate and reduce the potential clinical morbidity using such techniques. NP replacement strategies, such as hydrogels, are required to restore the NP pressurization or the lost volume. AF repair strategies including cross-linked hydrogels, fibrous composites, and sealants offer promise for regenerative therapies to restore AF integrity. Tissue engineered IVD structures, as a single implantable construct, may promote greater tissue integration due to the improved repair capacity of the vertebral bone. CONCLUSIONS: IVD height, neutral zone characteristics, and torsional biomechanics are sensitive to specific alterations in the NP pressurization and AF integrity and must be addressed for an effective functional repair. Synthetic and natural biomaterials offer promise for NP replacement, AF repair, as an AF sealant, or whole disc replacement. Meeting mechanical and biological compatibilities are necessary for the efficacy and longevity of the repair.
The spine journal: official journal of the North American Spine Society 01/2013; 13(3). DOI:10.1016/j.spinee.2012.12.002 · 2.43 Impact Factor
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