Papers by Shelly Sakiyama-Elbert
Abstract A consistent problem with stem/neural progenitor cell transplantation following spinal c... more Abstract A consistent problem with stem/neural progenitor cell transplantation following spinal cord injury (SCI) is poor cell survival and uncontrolled differentiation following transplantation.
Abstract The goal of this work was to improve the potential of fibrin to promote nerve regenerati... more Abstract The goal of this work was to improve the potential of fibrin to promote nerve regeneration by enzymatically incorporating exogenous neurite-promoting heparin-binding peptides. The effects on neurite extension of four different heparin-binding peptides, derived from the heparin-binding domains of antithrombin III, neural cell adhesion molecule and platelet factor 4, were determined. These exogenous peptides were synthesized as bi-domain peptide chimeras, with the second domain being a substrate for factor XIIIa.
Journal of Vascular Surgery, Jan 1, 2000
Journal of Hand Surgery-european Volume, Jan 1, 2007
Purpose: A bioactive fibrin-based delivery system was used to provide sustained administration of... more Purpose: A bioactive fibrin-based delivery system was used to provide sustained administration of platelet-derived growth factor (PDGF-BB) in a clinically relevant model of intrasynovial flexor tendon repair. We hypothesized that PDGF-BB administered in this manner would improve the sutured tendon's functional and structural properties 3 weeks after repair. Methods: A delivery system consisting of 30 L of fibrin matrix, peptide, heparin, and 100 ng of PDGF-BB was incorporated into the repair sites of randomly selected medial or lateral forepaw flexor digitorum profundus tendons of 8 adult mongrel dogs. The remaining forepaw flexor digitorum profundus tendons were repaired without the growth-factor and fibrin-based delivery system and served as controls. The surgically treated forelimbs were treated with controlled passive motion rehabilitation. The animals were killed at 3 weeks, at which time the tendons were tested for range of motion with a motion analysis system and for tensile properties with a materials testing machine. Results: Proximal interphalangeal joint and distal interphalangeal joint rotation values were significantly higher for the PDGF-BB-treated tendons compared with the repair-alone tendons. Excursion values were also significantly higher in the PDGF-BB-treated tendons. There were no significant differences in tensile properties when comparing PDGF-BB-treated with repair-alone tendons. Conclusions: The functional properties of repaired intrasynovial flexor tendons were significantly improved with the sustained administration of PDGF-BB. The failure to achieve improvements in ultimate load, stiffness, and strain in the experimental group may have been due to suboptimal PDGF-BB dosage or suboptimal release kinetics. (J Hand Surg 2007;32A: 373-379.
Annual Review of Materials Research, Jan 1, 2001
▪ Abstract The field of biomaterials has recently been focused on the design of intelligent mater... more ▪ Abstract The field of biomaterials has recently been focused on the design of intelligent materials. Toward this goal, materials have been developed that can provide specific bioactive signals to control the biological environment around them during the process of materials integration and wound healing. In addition, materials have been developed that can respond to changes in their environment, such as a change in pH or cell-associated enzymatic activity. In designing such novel biomaterials, researchers have sought not ...
Group, Jan 1, 2002
Recent advances in pharmaceutical research and development have led to an increased need for more... more Recent advances in pharmaceutical research and development have led to an increased need for more sophisticated drug delivery models. Today's technology calls for a wide range of delivery techniques that allow for different rates of drug release. Tailoring drug release rates for delivery under specific conditions is essential to maximizing efficiency and effectiveness of treatment. Delivery rates can be modified by altering parameters such as diffusion coefficients, number of available binding sites, and drug affinities. Because tissues regenerate at different rates, an ideal drug delivery system would be synchronized with the regeneration of the specific tissue it is affecting. A computer simulation would assist in determining the optimal parameters for this synchronization.
Journal of controlled …, Jan 1, 2004
This study investigated whether delayed treatment of spinal cord injury with controlled release o... more This study investigated whether delayed treatment of spinal cord injury with controlled release of neurotrophin-3 (NT-3) from fibrin scaffolds can stimulate enhanced neural fiber sprouting. Long Evans rats received a T9 dorsal hemisection spinal cord injury. Two weeks later, the injury site was re-exposed, and either a fibrin scaffold alone, a fibrin scaffold containing a heparin-based delivery system with different concentrations of NT-3 (500 and 1000 ng/mL), or a fibrin scaffold containing 1000 ng/mL of NT-3 (no delivery system) was implanted into the injury site. The injured spinal cords were evaluated for morphological differences using markers for neurons, astrocytes, and chondroitin sulfate proteoglycans 2 weeks after treatment. The addition of 500 ng/ mL of NT-3 with the delivery system resulted in an increase in neural fiber density compared to fibrin alone. These results demonstrate that the controlled release of NT-3 from fibrin scaffolds can enhance neural fiber sprouting even when treatment is delayed 2 weeks following injury.
Experimental …, Jan 1, 2003
Based on previous studies demonstrating the potential of growth factors to enhance peripheral ner... more Based on previous studies demonstrating the potential of growth factors to enhance peripheral nerve regeneration, we developed a novel growth factor delivery system to provide sustained delivery of nerve growth factor (NGF). This delivery system uses heparin to immobilize NGF and slow its diffusion from a fibrin matrix. This system has been previously shown to enhance neurite outgrowth in vitro, and in this study, we evaluated the ability of this delivery system to enhance nerve regeneration through conduits. We tested the effect of controlled NGF delivery on peripheral nerve regeneration in a 13-mm rat sciatic nerve defect. The heparin-containing delivery system was studied in combination with three doses of NGF (5, 20, or 50 ng/mL) and the results were compared with positive controls (isografts) and negative controls (fibrin alone, NGF alone, and empty conduits). Nerves were harvested at 6 weeks postoperatively for histomorphometric analysis. Axonal regeneration in the delivery system groups revealed a marked dose-dependent effect. The total number of nerve fibers at both the mid-conduit level and in the distal nerve showed no statistical difference for NGF doses at 20 and 50 ng/mL from the isograft (positive control). The results of this study demonstrate that the incorporation of a novel delivery system providing controlled release of growth factors enhances peripheral nerve regeneration and represents a significant contribution toward enhancing nerve regeneration across short nerve gaps.
abstracts.conferencestrategists.com
Journal of Orthopaedic …
Despite advances in surgical technique, rotator cuff repairs are plagued by a high rate of failur... more Despite advances in surgical technique, rotator cuff repairs are plagued by a high rate of failure. This failure rate is in part due to poor tendon-to-bone healing; rather than regeneration of a fibrocartilaginous attachment, the repair is filled with disorganized fibrovascular (scar) tissue. Transforming growth factor beta 3 (TGF-b3) has been implicated in fetal development and scarless fetal healing and, thus, exogenous addition of TGF-b3 may enhance tendon-to-bone healing. We hypothesized that: TGF-b3 could be released in a controlled manner using a heparin/fibrin-based delivery system (HBDS); and delivery of TGF-b3 at the healing tendon-to-bone insertion would lead to improvements in biomechanical properties compared to untreated controls. After demonstrating that the release kinetics of TGF-b3 could be controlled using a HBDS in vitro, matrices were incorporated at the repaired supraspinatus tendon-to-bone insertions of rats. Animals were sacrificed at 14-56 days. Repaired insertions were assessed using histology (for inflammation, vascularity, and cell proliferation) and biomechanics (for structural and mechanical properties). TGF-b3 treatment in vivo accelerated the healing process, with increases in inflammation, cellularity, vascularity, and cell proliferation at the early timepoints. Moreover, sustained delivery of TGF-b3 to the healing tendon-to-bone insertion led to significant improvements in structural properties at 28 days and in material properties at 56 days compared to controls. We concluded that TGF-b3 delivered at a sustained rate using a HBDS enhanced tendon-to-bone healing in a rat model. ß
Fibrin is the natural biomaterial of nerve regeneration. Fibrin possesses the ability to promote ... more Fibrin is the natural biomaterial of nerve regeneration. Fibrin possesses the ability to promote cell adhesion and can be degraded locally by cell-regulated proteases. However, fibrin lacks sufficient neuroinductive character to promote nerve regeneration across large gaps. A previously developed method for the incorporation of peptides via the transglutaminase activity of factor XIIIa was used to immobilize cell adhesion sites and growth factors within fibrin matrices that could serve as potential therapeutics for ...
Plastic and …, Jan 1, 2010
METHODS: We evaluated the effect of controlled delivery of GDNF from fibrin-filled nerve guidance... more METHODS: We evaluated the effect of controlled delivery of GDNF from fibrin-filled nerve guidance conduits on motor nerve regeneration and functional recovery in a 13 mm rat sciatic nerve defect. Seven experimental groups were evaluated including: GDNF and DS and NGF with DS and control groups including: GDNF without a DS, isograft (positive control), fibrin with growth factors and empty conduits. Animals were monitored monthly for behavioral recovery, which included sciatic functional index and grid-grip abilities, and ...
Structure-function relationships incorporate anisotropy of soft tissues, to account for their dir... more Structure-function relationships incorporate anisotropy of soft tissues, to account for their direction-dependent loading response [1]. Empirical measures: fiber alignment and distribution have been used to describe soft tissue response due to cell-matrix interactions and applied loads [2, 3]. To complement these measures, noninvasive estimation of anisotropic mechanical properties is essential. Magnetic resonance elastography (MRE) is a noninvasive technique to obtain elastic properties form propagating shear waves [4]. ...
Journal of …, Jan 1, 2011
Phenotypic differences in Schwann cells (SCs) may help to guide axonal regeneration down motor or... more Phenotypic differences in Schwann cells (SCs) may help to guide axonal regeneration down motor or sensory specific pathways following peripheral nerve injury. The goal of this study was to identify phenotypic markers for SCs harvested from the cutaneous (sensory) and quadriceps (motor) branches of the rat femoral nerve and to study the effects of expansion culture on the expression patterns of these motor or sensory phenotypic markers. RNA was extracted from SCs harvested from the motor and sensory branches of the rat femoral nerve and analyzed using Affymetrix Gene Chips (Rat Genome 230 v2.0 Array A). Genes that were upregulated in motor SCs compared with the sensory SCs or vice versa were identified, and the results were verified for a subset of genes using quantitative real-time polymerase chain reaction (qRT-PCR). The expression levels of the "phenotype-specific" genes were then evaluated in SC expansion cultures at various time points over 30 days by qRT-PCR to determine the effect of expansion on SC phenotype. Expression levels of the phenotype-specific genes were significantly altered after expansion culture for both the motor and the sensory markers compared with fresh nerve tissue. These results indicate that both motor and sensory SC gene expression patterns are disrupted during expansion in vitro and may affect the ability of SCs to express phenotype-specific genes after transplantation.
Journal of Neuroscience …, Jan 1, 2011
Peripheral nerve regeneration after injury depends on environmental cues and trophic support. Sch... more Peripheral nerve regeneration after injury depends on environmental cues and trophic support. Schwann cells (SCs) secrete trophic factors that promote neuronal survival and help guide axons during regeneration. The addition of SCs to acellular nerve grafts is a promising strategy for enhancing peripheral nerve regeneration; however, inconsistencies in seeding parameters have led to varying results. The current work sought to establish a systematic approach to seeding SCs in cold-preserved acellular nerve grafts. Studies were undertaken to (1) determine the needle gauge for optimal cell survival and minimal epineurial disruption during injection, (2) track the seeded SCs using a commercially available dye, and (3) evaluate the seeding efficiency of SCs in nerve grafts. It was determined that seeding with a 27-gauge needle resulted in the highest viability of SCs with the least damage to the epineurium. In addition, Qtracker® dye, a commercially available quantum dot nanocrystal, was used to label SCs prior to transplantation, which allowed visualization of the seeded SCs in nerve grafts. Finally, stereological methods were used to evaluate the seeding efficiency of SCs in nerve grafts immediately after injection and following a 1-or 3-day in vitro incubation in SC growth media. Using a systematic approach, the best needle gauge and a suitable dye for SC visualization in acellular nerve grafts were identified. Seeding efficiency in these grafts was also determined. The findings will lead to improvements ability to assess injection of cells (including SCs) for use with acellular nerve grafts to promote nerve regeneration.
Plastic and …, Jan 1, 2009
METHODS: The rat femoral motor nerve model was used to examine the effect of controlled delivery ... more METHODS: The rat femoral motor nerve model was used to examine the effect of controlled delivery of GDNF on motor nerve regeneration across a 5 mm nerve gap. Four experimental groups (n= 7-8) were evaluated. These included GDNF with the fibrin based delivery system (DS), fibrin matrix without growth factor, empty silicone conduit (negative control) and nerve isograft (positive control). Nerves were harvested 5 weeks after treatment for analysis by histomorphometry and electron microscopy.
Biotechnology and …, Jan 1, 2010
Glial-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) have both been shown to en... more Glial-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) have both been shown to enhance peripheral nerve regeneration following injury and target different neuronal populations. The delivery of either growth factor at the site of injury may, therefore, result in quantitative differences in motor nerve regeneration and functional recovery. In this study we evaluated the effect of affinity-based delivery of GDNF or NGF from fibrin-filled nerve guidance conduits (NGCs) on motor nerve regeneration and functional recovery in a 13 mm rat sciatic nerve defect. Seven experimental groups were evaluated consisting of GDNF or NGF and the affinity-based delivery system (DS) within NGCs, control groups excluding the DS and/or growth factor, and nerve isografts. Groups with growth factor in the conduit demonstrated equivalent or superior performance in behavioral tests and relative muscle mass measurements compared to isografts at 12 weeks. Additionally, groups with GDNF demonstrated greater specific twitch and tetanic force production in extensor digitorum longus (EDL) muscle than the isograft control, while groups with NGF produced demonstrated similar force production compared to the isograft control. Assessment of motor axon regeneration by retrograde labeling further revealed that the number of ventral horn neurons regenerating across NGCs containing GDNF and NGF DS was similar to the isograft group and these counts were greater than the groups without growth factor. Overall, the GDNF DS group demonstrated superior functional recovery and equivalent motor nerve regeneration compared to the isograft control, suggesting it has potential as a treatment for motor nerve injury.
… Polymer Edition, 21, Jan 1, 2010
The controlled delivery of nerve growth factor (NGF) to the peripheral nervous system has been sh... more The controlled delivery of nerve growth factor (NGF) to the peripheral nervous system has been shown to enhance nerve regeneration following injury, although the effect of release rate has not been previously studied with an affinity-based delivery system (DS). The goal of this research was to determine if the binding site affinity of the DS affected nerve regeneration in vivo using nerve guidance conduits (NGCs) in a 13-mm rat sciatic nerve defect. These DSs consisted of bi-domain peptides that varied in heparin-binding affinity, heparin and NGF, which binds to heparin with moderate affinity. Eight experimental groups were evaluated consisting of NGF with DS, control groups excluding one or more components of the DS within silicone conduits and nerve isografts. Nerves were harvested 6 weeks after treatment for analysis by histomorphometry. These DSs with NGF resulted in a higher frequency of nerve regeneration compared to control groups and were similar to the nerve isograft group in measures of nerve fiber density and percent neural tissue, but not in total nerve fiber count. In addition, these DSs with NGF contained a significantly greater percentage of larger diameter nerve fibers, suggesting more mature regenerating nerve content. While there were no differences in nerve regeneration due to varying peptide affinity with these DSs, their use with NGF enhanced peripheral nerve regeneration through a NGC across a critical nerve gap.
Soft Matter, Jan 1, 2010
Two recurring problems with stem/neural progenitor cell (NPC) transplantation therapies for spina... more Two recurring problems with stem/neural progenitor cell (NPC) transplantation therapies for spinal cord injury (SCI) are poor cell survival and uncontrolled cell differentiation. The current study evaluated the viability and differentiation of embryonic stem cell-derived neural progenitor cells (ESNPCs) transplanted within fibrin scaffolds containing growth factors (GFs) and a heparin-binding delivery system (HBDS) to enhance cell survival and direct differentiation into neurons. Mouse ESNPCs were generated from mouse embryonic stem cells (ESCs) using a 4−/4+ retinoic acid (RA) induction protocol that resulted in a population of cells that was 70% nestin positive NPCs. The ESNPCs were transplanted directly into a rat subacute dorsal hemisection lesion SCI model. ESNPCs were either encapsulated in a fibrin scaffold; encapsulated in fibrin containing the HBDS, neurotrophin-3 (NT-3) and platelet derived growth factor (PDGF-AA); or encapsulated in fibrin scaffolds with NT-3 and PDGF-AA without the HBDS. We report that the combination of GFs and fibrin scaffold (without HBDS) enhanced the total number of ESNPCs present in the treated spinal cords and increased the number of ESNPC-derived NeuN positive neurons 8 weeks after transplantation. All experimental groups treated with ESNPCs exhibited an increase in behavioral function 4 weeks after transplantation. In a subset of animals, the ESNPCs over-proliferated as evidenced by SSEA-1 positive/Ki67 positive ESCs found at 4 and 8 weeks. These results demonstrate the potential of tissue-engineered fibrin scaffolds to enhance the survival of NPCs and highlight the need to purify cell populations used in therapies for SCI.
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Papers by Shelly Sakiyama-Elbert