Evaluation of an In Situ Gelable and Injectable Hydrogel Treatment to Preserve Human Disc Mechanical Function Undergoing Physiologic Cyclic Loading Followed by Hydrated Recovery.

Despite the prevalence of disc degeneration and its contributions to low back problems, many current treatments are palliative only and ultimately fail. To address this, nucleus pulposus replacements are under development. Previous work on an injectable hydrogel nucleus pulposus replacement composed of n-carboxyethyl chitosan, oxidized dextran, and teleostean has shown that it has properties similar to native nucleus pulposus, can restore compressive range of motion in ovine discs, is biocompatible, and promotes cell proliferation. The objective of this study was to determine if the hydrogel implant will be contained and if it will restore mechanics in human discs undergoing physiologic cyclic compressive loading. Fourteen human lumbar spine segments were tested using physiologic cyclic compressive loading while intact, following nucleotomy, and again following treatment of injecting either phosphate buffered saline (PBS) (sham, n = 7) or hydrogel (implant, n = 7). In each compressive test, mechanical parameters were measured immediately before and after 10,000 cycles of compressive loading and following a period of hydrated recovery. The hydrogel implant was not ejected from the disc during 10,000 cycles of physiological compression testing and appeared undamaged when discs were bisected following all mechanical tests. For sham samples, creep during cyclic loading increased (+15%) from creep during nucleotomy testing, while for implant samples creep strain decreased (-3%) toward normal. There was no difference in compressive modulus or compressive strains between implant and sham samples. These findings demonstrate that the implant interdigitates with the nucleus pulposus, preventing its expulsion during 10,000 cycles of compressive loading and preserves disc creep within human L5-S1 discs. This and previous studies provide a solid foundation for continuing to evaluate the efficacy of the hydrogel implant.

Sustained Ocular Delivery of Bevacizumab Using Densomeres in Rabbits: Effects on Molecular Integrity and Bioactivity.

Purpose: To demonstrate that a single administration of an anti-angiogenic monoclonal antibody, when integrated into a novel biodegradable Densomere composed only of the active pharmaceutical ingredient and polymer, maintains molecular integrity, sustained release, and prolonged bioactivity in vitro and in vivo for up to 12 months. Methods: Bevacizumab, a high-molecular-weight antibody (140,000-150,000 Da) was incorporated at 5% loading into Densomere microparticle carriers (DMCs) for injection to observe in vitro release over time from an aqueous suspension. The molecular integrity of the released bevacizumab was assessed by enzyme-linked immunosorbent assay (ELISA) and size-exclusion chromatography-high-performance liquid chromatography (SEC-HPLC). Anti-angiogenic bioactivity in vivo was assessed using the rabbit corneal suture model for suppression of neovascular encroachment from the limbus following a single subconjunctival administration. Results: Continuous release of bevacizumab in vitro was observed in serial samples over a period of 12 months. ELISA and SEC-HPLC yielded profiles from aqueous supernatant samples indistinguishable from the reference bevacizumab. A single subconjunctival administration in rabbit eyes significantly suppressed corneal neovascularization in vivo compared to control eyes for 12 months. Conclusions: The Densomere carrier platform maintained the molecular integrity of bevacizumab with a prolonged release profile in vitro and demonstrated sustained in vivo drug delivery with continuous bioactivity in the rabbit cornea eye model for 12 months. Translational Relevance: The Densomere platform provides a significant opportunity for prolonged delivery of biologics in ocular and other tissues.

Rosiglitazone modulates the behaviors of diabetic host-derived fibroblasts in a carboxymethyllysine-modified collagen model.

Utilizing a three-dimensional in vitro glycated collagen model, we evaluated the therapeutic effects of a peroxisome proliferator-activated receptor-γ ligand, rosiglitazone, and its potential as a topical treatment of diabetic chronic wounds. Rosiglitazone induced fibroblast migration, α-smooth muscle actin production, and transformation into myofibroblasts in the presence of advanced glycation end products. Both transforming growth factor ß and peroxisome proliferator-activated receptor-γ expression were induced, while the receptor for advanced glycation end products was suppressed. Lastly, the reduced activities of matrix metalloproteinase-2 and matrix metalloproteinases-9 in the carboxymethyllysine-modified collagen matrices by rosiglitazone increases extracellular matrix deposition. Our findings identify rosiglitazone as a candidate for localized topical treatment of diabetic chronic wounds.

A multidisciplinary team approach to hydroxyurea-associated chronic wound with squamous cell carcinoma.

Hydroxyurea (HU) has been shown to induce a variety of cutaneous adverse reactions, including severe leg ulcers. This report shows a successful treatment of a HU-induced chronic wound associated with squamous cell carcinomas (SCC). A 62-year-old patient affected with polycythemia vera and treated with HU for 10 years, presented with a non healing ulcer on a left heel. The patient gave a history of suffering from the wound for over 2 years. Biopsy showed evidence of invasive SCC. The patient underwent Mohs surgery and a greater saphenous vein ablation for polycythemia vera-associated vascular complications. The wound consistently decreased in size following successive debridements and coverage with human skin equivalent. The wound healed completely after a 6-month period. A multidisciplinary team approach to the treatment proved to be effective resulting in healing of this multifactorial chronic ulcer.

In situ gelable interpenetrating double network hydrogel formulated from binary components: thiolated chitosan and oxidized dextran.

In situ gelable interpenetrating double-network hydrogels composed of thiolated chitosan (Chitosan-NAC) and oxidized dextran (Odex), completely devoid of potentially cytotoxic small molecule cross-linkers and that do not require complex maneuvers or catalysis, have been formulated. The interpenetrating network structure is created by Schiff base formations and disulfide bond inter-cross-linkings through exploiting the disparity of their reaction times. Compared with the autogelable thiolated chitosan hydrogels that typically require a relatively long time span for gelation to occur, the Odex/Chitosan-NAC composition solidifies rapidly and forms a well-developed 3D network in a short time span. Compared with typical hydrogels derived from natural materials, the Odex/Chitosan-NAC hydrogels are mechanically strong and resist degradation. The cytotoxicity potential of the hydrogels was determined by an in vitro viability assay using fibroblast as a model cell, and the results reveal that the hydrogels are noncytotoxic. In parallel, in vivo results from subdermal implantation in mice models demonstrate that this hydrogel is not only highly resistant to degradation but also induces very mild tissue response.

Mesenchymal stem cell therapy and delivery systems in nonhealing wounds.

OBJECTIVE: The objective of the study was to inform wound care practitioners of mesenchymal stem cell application for nonhealing wounds. Recent advances in delivery systems are also discussed in order to highlight potential improvements toward clinical application of stem cell therapy for chronic wounds. DATA SOURCES: MEDLINE and PubMed Central were searched for scientific studies regarding the use of mesenchymal stem cells and delivery systems in wound healing. STUDY SELECTION: Preclinical studies using stem cells as therapeutic modality for chronic wounds were selected for this review. DATA EXTRACTION: Information on study design, sample size and characteristics, stem cell source, type of delivery systems, and rate and time of wound closure was abstracted. DATA SYNTHESIS: Application of mesenchymal stem cells improved wound healing in experimental and clinical settings. Advances in stem cell therapy and delivery vehicles offer promising alternatives to current limited therapeutic modalities for chronic wounds. CONCLUSIONS: Stem cell therapy has recently emerged as a promising therapeutic strategy for nonhealing wounds. Further research is needed to evaluate the relationship between the various delivery systems and stem cells in order to maximize their therapeutic effects. Development of novel delivery vehicles for stem cells can open new opportunities for more effective cell therapy of chronic wounds.

Combined Hydrogel and Mesenchymal Stem Cell Therapy for Moderate-Severity Disc Degeneration in Goats.

Intervertebral disc degeneration is a cascade of cellular, structural, and biomechanical changes that is strongly implicated as a cause of low-back pain. Current treatment strategies have poor long-term efficacy as they seek only to alleviate symptoms without preserving or restoring native tissue structure and function. The objective of this study was to evaluate the efficacy of a combined triple interpenetrating network hydrogel (comprising dextran, chitosan, and teleostean) and mesenchymal stem cell (MSC) therapy targeting moderate-severity disc degeneration in a clinically relevant goat model. Degeneration was induced in lumbar discs of 10 large frame goats by injection of chondroitinase ABC. After 12 weeks, degenerate discs were treated by injection of either hydrogel alone or hydrogel seeded with allogeneic, bone marrow-derived MSCs. Untreated healthy and degenerate discs served as controls, and animals were euthanized 2 weeks after treatment. Discs exhibited a significant loss of disc height 12 weeks after degeneration was induced. Two weeks after treatment, discs that received the combined hydrogel and MSC injection exhibited a significant, 10% improvement in disc height index, as well as improvements in histological condition. Discs that were treated with hydrogel alone exhibited reduced tumor necrosis factor-α expression in the nucleus pulposus (NP). Microcomputed tomography imaging revealed that the hydrogel remained localized to the central NP region of all treated discs after 2 weeks of unrestricted activity. These encouraging findings motivate further, longer term studies of therapeutic efficacy of hydrogel and MSC injections in this large animal model. Impact statement Low-back pain is the leading cause of disability worldwide, and degeneration of the intervertebral discs is considered to be one of the most common reasons for low-back pain. Current treatment strategies focus solely on alleviation of symptoms, and there is a critical need for new treatments that also restore disc structure and function. In this study, using a clinically relevant goat model of moderate-severity disc degeneration, we demonstrate that a combined interpenetrating network hydrogel and mesenchymal stem cell therapy provides acute improvements in disc height, histological condition, and local inflammation.

Novel macromolecular crosslinking hydrogel to reduce intra-abdominal adhesions.

BACKGROUND: The aim of this study was to compare the anti-adhesion efficacy of a biodegradable, in situ, macromolecular cross-linking hydrogel made from oxidized dextran/N-carboxyethyl chitosan (Odex/CEC) with a commercially available carboxymethylcellulose/modified hyaluronan barrier film (Seprafilm; Genzyme Corporation, Cambridge, MA) in a rat cecum abrasion model. METHODS: The rat model utilized a cecal abrasion and abdominal wall insult surgical protocol. The 2% Odex/CEC hydrogel treatment was applied by syringe to coat both the cecal and the abdominal wall insults, while other animals were treated with Seprafilm applied to the cecal injury only. Control animals did not receive any treatment. Animals were sacrificed after post operative day 21 and adhesion severity was quantitatively graded using a whole number scale from 0 - 3. Histological analysis was also performed for animals receiving Odex/CEC hydrogel treatment and no treatment (control). RESULTS: Mean adhesion score was 2.09+/-1.22 for control animals, 1.00+/-1.00 for 2% Odex/CEC hydrogel animals, and 1.25+/-1.22 for Seprafilm animals. Hydrogel treated animals showed significantly lower adhesion scores than control animals (P<0.05), while Seprafilm demonstrated a marginally lower adhesion score (P<0.1) compared with the controls. Histological analysis of an Odex/CEC treated rat showed tissue repair and small fragments of hydrogel inside both healed abdominal and cecal surfaces. CONCLUSIONS: Both Seprafilm and the 2% Odex/CEC hydrogel showed a significantly decreased adhesion score compared with the control. However, the hydrogel, compared with Seprafilm, offers ease of application and ability to conform to complex tissue geometries that could provide surgeons with another prophylactic treatment to prevent abdominal adhesions.

Prevention of cerebral vasospasm by local delivery of cromakalim with a biodegradable controlled-release system in a rat model of subarachnoid hemorrhage.

OBJECT: One mechanism that contributes to cerebral vasospasm is the impairment of potassium channels in vascular smooth muscles. Adenosine triphosphate-sensitive potassium channel openers (PCOs) appear to be particularly effective for dilating cerebral arteries in experimental models of subarachnoid hemorrhage (SAH). A mode of safe administration that provides timed release of PCO drugs is still a subject of investigation. The authors tested the efficacy of locally delivered intrathecal cromakalim, a PCO, incorporated into a controlled-release system to prevent cerebral vasospasm in a rat model of SAH. METHODS: Cromakalim was coupled to a viscous carrier, hyaluronan, 15% by weight. In vitro release kinetics studies showed a steady release of cromakalim over days. Fifty adult male Sprague-Dawley rats weighing 350-400 g each were divided into 10 groups and treated with various doses of cromakalim or cromakalim/hyaluronan in a rat double SAH model. Treatment was started 30 minutes after the second SAH induction. Animals were killed 3 days after treatment, and the basilar arteries were processed for morphometric measurements and histological analysis. RESULTS: Controlled release of cromakalim from the cromakalim/hyaluronan implant at a dose of 0.055 mg/kg significantly increased lumen patency in a dose-dependent manner up to 94 +/- 8% (mean +/- standard error of the mean) of the basilar arteries of the sham group compared with the empty polymer group (p = 0.006). Results in the empty polymer group were not different from those in the SAH-only group, with a lumen patency of 65 +/- 12%. Lumen patencies of the cromakalim-only groups did not differ in statistical significance at low (64 +/- 9%) or high (66 +/- 7%) doses compared to the SAH-only group. CONCLUSIONS: Treatment of SAH with a controlled-release cromakalim/hyaluronan implant prevented experimental cerebral vasospasm in this rat double hemorrhage model; this inhibition was dose-dependent. The authors' results confirm that sustained delivery of cromakalim perivascularly to cerebral vessels could be an effective therapeutic strategy in the treatment of cerebral vasospasm after SAH.

Cross-linked hyaluronic acid films to reduce intra-abdominal postsurgical adhesions in an experimental model.

BACKGROUND/AIMS: Intra-abdominal adhesions typically occur after surgically damaged tissues are situated in apposition, leading to fibrotic connections. The goal of this study was to demonstrate the in vivo efficacy of a cross-linked and insoluble hyaluronic acid (HA) film to reduce postsurgical adhesion in a rat model. METHODS: To measure in vitro adhesion resistance, porcine monocytes were deposited on the surface of films and their attachment was monitored by scanning electron microscopy. A rat cecum abrasion and abdominal insult model was utilized to demonstrate in vivo efficacy. Briefly, an HA film was deployed as a barrier between the damaged cecal and abdominal tissue surfaces for 21 days; control animals did not receive treatment. At the study conclusion, the rats were sacrificed and the degree of adhesion was determined using a scale from 0 to 3, where 0 = no adhesion and 3 = severe fibrosis. RESULTS: HA films resisted monocyte adhesion in vitro. The in vivo study results demonstrated a significantly lower mean adhesion score (0.625 +/- 0.517) with HA film treatment compared to the controls (2.09 +/- 1.22). CONCLUSION: Placement of HA films between injured tissues significantly decreases the severity of abdominal adhesions. Furthermore, the HA film's resistance to monocyte adhesion could be contributory to lowering in vivo adhesion scores.

Differential physical, rheological, and biological properties of rapid in situ gelable hydrogels composed of oxidized alginate and gelatin derived from marine or porcine sources.

Marine derived gelatin is not known to associate with any communicable diseases to mammals and could be a reasonable substitute for gelatin derived from either bovine or porcine sources. The low melting point of marine gelatin (8 degrees C) also offers greater formulation flexibility than mammalian derived gelatins. However, the sub-optimal physical properties of marine gelatin generally limit the interest to further develop it for biomedical applications. This study aimed at investigating the feasibility of using oxidized alginate (Oalg) as a high activity macromolecular crosslinker of marine gelatin to formulate in situ gelable hydrogels with the goal of enhancing the latter's physical properties. The performance of Oalg/marine gelatin hydrogel was compared to Oalg/porcine gelatin hydrogel; in general, the physicomechanical properties of both hydrogels were comparable, with the hydrogels containing porcine gelatin exhibiting moderately higher mechanical strengths with shorter gelation times, smaller size pores, and higher swelling ratios. On the contrary, the biological performances of the two hydrogels were significantly difference. Cells cultured in the marine gelatin derived hydrogel grew significantly faster, with greater than 60% more cells by 7 days and they exhibited more spread-out conformations as compared those cultured in the porcine derived hydrogel. Production of ECM by cells cultured in the Oalg/marine gelatin hydrogel was up to 2.4 times greater than that of in the Oalg/porcine gelatin hydrogel. The biodegradation rate of the hydrogel formulated from marine gelatin was greater than its counterpart prepared from porcine gelatin. These differences have important implications in the biomedical applications of the two hydrogels.

The biodegradability of electrospun Dextran/PLGA scaffold in a fibroblast/macrophage co-culture.

Fibroblast and macrophage are 2 dominant cell types respond cooperatively to degrade implanted biomaterials. Using an electrospun Dextran/Poly-lactide-co-glycolide (PLGA) scaffold as a model, an in vitro fibroblast/macrophage co-culture system was developed to investigate the degradability of implantable biodegradable materials. SEM showed that both fibroblasts and macrophages were able to degrade the scaffold, separately or cooperatively. Under the synergistic coordination of macrophages and fibroblasts, scaffolds showed faster degradation rate than their counterparts incubated with a single type of cells as well as in PBS or cell culture medium. Lysozyme, non-specific esterase (NSE), gelatinase, hyaluronidase-1 and alpha-glucosidase were up-regulated in the presence of the scaffold, suggesting their roles in the cell-mediated scaffold degradation. In addition, the expressions of cell surface receptors CD204 and Toll like receptor 4 (TLR4) were elevated 1 week after cell seeding, implying that these receptors might be involved in scaffold degradation. The results of in vivo subdermal implantation of the scaffold further confirmed the biodegradability of the Dextran/PLGA scaffold. The fibroblast/macrophage co-culture model adequately mimicked the in vivo environment and could be further developed into an in vitro tool for initial biomaterial evaluation.

Mechanically strong double network photocrosslinked hydrogels from N,N-dimethylacrylamide and glycidyl methacrylated hyaluronan.

Hyaluronan (HA) is a natural polysaccharide abundant in biological tissues and it can be modified to prepare biomaterials. In this work, HA modified with glycidyl methacrylate was photocrosslinked to form the first network (PHA), and then a series of highly porous PHA/N,N-dimethylacrylamide (DAAm) hydrogels (PHA/DAAm) with high mechanical strength were obtained by incorporating a second network of photocrosslinked DAAm into PHA network. Due to the synergistic effect produced by double network (DN) structure, despite containing 90% of water, the resulting PHA/DAAm hydrogel showed a compressive modulus and a fracture stress over 0.5 MPa and 5.2 MPa, respectively. Compared to the photocrosslinked hyaluronan single network hydrogel, which is generally very brittle and fractures easily, the PHA/DAAm hydrogels are ductile. Mouse dermal fibroblast was used as a model cell line to validate in vitro non-cytotoxicity of the PHA/DAAm hydrogels. Cells deposited extracellular matrix on the surface of these hydrogels and this was confirmed by positive staining of Type I collagen by Sirius Red. The PHA/DAAm hydrogels were also resistant to biodegradation and largely retained their excellent mechanical properties even after 2 months of co-culturing with fibroblasts.

Non-cytotoxic, in situ gelable hydrogels composed of N-carboxyethyl chitosan and oxidized dextran.

A series of in situ gelable hydrogels were prepared from oxidized dextran (Odex) and N-carboxyethyl chitosan (CEC) without any extraneous crosslinking agent. The gelation readily took place at physiological pH and body temperature. The gelation process was monitored rheologically, and the effect of the oxidation degree of dextran on the gelation process was investigated. The higher the oxidation degree of Odex, the faster the gelation. A highly porous hydrogel structure was revealed under scanning electron microscopy (SEM). Swelling and degradation of the Odex/CEC hydrogels in PBS showed that both swelling and degradation were related to the crosslinking density of the hydrogels. In particular, the hydrogels underwent fast mass loss in the first 2 weeks, followed by a more moderate degradation. The results of long-term cell viability tests revealed that the hydrogels were non-cytotoxic. Mouse fibroblasts were encapsulated in the hydrogels and cell viability was at least 95% within 3 days following encapsulation. Furthermore, cells entrapped inside the hydrogel assumed round shape initially but they gradually adapted to the new environment and spread-out to assume more spiny shapes. Additionally, the results from applying the Odex/CEC system to mice full-thickness transcutaneous wound models suggested that it was capable of enhancing wound healing.

Biodegradable fibrous scaffolds composed of gelatin coated poly(epsilon-caprolactone) prepared by coaxial electrospinning.

A facile coaxial electrospinning technique was devised to prepare biodegradable core-shell fibrous scaffolds with poly(epsilon-caprolactone) (PCL) comprising the core structure and gelatin forming the coating of the fibers. The effect of the feed rate of the inner dope on the electrospinning process and fiber morphology was investigated. The results indicated that core-shell fibers with narrow size distribution and smooth surface morphology could be obtained when the feed rate was below 8 mL/h. An increase of the feed rate resulted in analogous increase in the diameters of both the inner PCL fiber core and the entire core-shell fibers. XPS analyses revealed that the surface of the core-shell fibers was tainted with a small amount of PCL. The outer gelatin layer in the core-shell fibers was crosslinked with glutaraldehyde. By optimizing the glutaraldehyde/gelatin feed ratio, crosslinked scaffolds with high porosity were obtained. The mechanic strength of the hydrated, crosslinked core-shell fibrous scaffolds was significantly enhanced because of the presence of hydrophobic PCL in the core region of the fibers. Results of cell culture studies suggested that the crosslinked, core-shell fibrous scaffold were nontoxic and capable of supporting fibroblast adhesion and proliferation.

Water soluble complexes of chitosan-g-MPEG and hyaluronic acid.

Novel water soluble, biocompatible, and highly viscoelastic polyelectrolyte complexes were prepared by mixing of positively charged chitosan grafted with poly (ethylene glycol) monomethyl ether (CS-g-MPEG) and negatively charged hyaluronic acid (HA). CS-g-MPEGs having different degrees of substitution were synthesized by reacting chitosan with MPEG-aldehyde. The molecular structure, thermal and rheological properties, as well as biocompatibility of CS-g-MPEG/HA complexes were characterized. Rheological results showed that a small amount of HA could greatly enhance the viscosity of CS-g-MPEG solution. The highest viscosity was obtained when the charge ratio of CS-g-MPEG/HA was close to 1.0. Small-angle X-ray scattering measurements provided some insights into the lamellar structure of the CS-g-MPEG/HA complex. The CS-g-MPEG/HA complex system offers promising potentials in pharmaceutical, cosmetic, and biotechnology applications (e.g., cell scaffold, artificial synovial fluid, and drug/gene delivery medium).

Human hepatoblast phenotype maintained by hyaluronan hydrogels.

Human hepatoblasts and hepatic stem cells, pluripotent hepatic progenitors that give rise to hepatocytes and biliary cells, were isolated from fetal livers and found to express hyaluronan receptors (CD44) in both the freshly isolated cells and after culture. This implicates an in vivo connection to hyaluronan (HA), an embryonic matrix component, as a candidate 3-dimensional (3-D) scaffold for hepatic progenitor cell expansion and/or differentiation. To assess HAs as scaffolds, hepatoblasts and hepatic stem cells were seeded into HA hydrogels with a serum-free, hormonally defined medium tailored for expansion of hepatic progenitors. Cell aggregates formed within the HA hydrogels and remained viable, proliferative, and demonstrated a stable phenotype intermediate between that of hepatic stem cells and hepatoblasts throughout more than 4 weeks of culturing, with little evidence of lineage restriction towards either hepatocytic or biliary pathways. The phenotype consisted of stable co-expression of both hepatocytic and biliary markers such as biliary-specific cytokeratin, CK19, low levels of expression of albumin, and urea synthesis. HA hydrogels are ideal as 3-D scaffolds for pluripotent hepatic progenitors and should be useful for generating cells to be used in bioartificial livers or tissue engineered liver grafts.

Translation of an injectable triple-interpenetrating-network hydrogel for intervertebral disc regeneration in a goat model.

Degeneration of the intervertebral discs is a progressive cascade of cellular, compositional and structural changes that is frequently associated with low back pain. As the first signs of disc degeneration typically arise in the disc's central nucleus pulposus (NP), augmentation of the NP via hydrogel injection represents a promising strategy to treat early to mid-stage degeneration. The purpose of this study was to establish the translational feasibility of a triple interpenetrating network hydrogel composed of dextran, chitosan, and teleostean (DCT) for augmentation of the degenerative NP in a preclinical goat model. Ex vivo injection of the DCT hydrogel into degenerated goat lumbar motion segments restored range of motion and neutral zone modulus towards physiologic values. To facilitate non-invasive assessment of hydrogel delivery and distribution, zirconia nanoparticles were added to make the hydrogel radiopaque. Importantly, the addition of zirconia did not negatively impact viability or matrix producing capacity of goat mesenchymal stem cells or NP cells seeded within the hydrogel in vitro. In vivo studies demonstrated that the radiopaque DCT hydrogel was successfully delivered to degenerated goat lumbar intervertebral discs, where it was distributed throughout both the NP and annulus fibrosus, and that the hydrogel remained contained within the disc space for two weeks without evidence of extrusion. These results demonstrate the translational potential of this hydrogel for functional regeneration of degenerate intervertebral discs. STATEMENT OF SIGNIFICANCE: The results of this work demonstrate that a radiopaque hydrogel is capable of normalizing the mechanical function of the degenerative disc, is supportive of disc cell and mesenchymal stem cell viability and matrix production, and can be maintained in the disc space without extrusion following intradiscal delivery in a preclinical large animal model. These results support evaluation of this hydrogel as a minimally invasive disc therapeutic in long-term preclinical studies as a precursor to future clinical application in patients with disc degeneration and low back pain.

Interaction of dermal fibroblasts with electrospun composite polymer scaffolds prepared from dextran and poly lactide-co-glycolide.

A highly porous electrospun scaffold was prepared by physically blending Dextran and poly lactide-co-glycolide (PLGA). The interaction between dermal fibroblasts and the Dextran/PLGA scaffold such as viability, proliferation, attachment, migration, extracellular matrix deposition, cytoskeleton organization and the functional gene expressions were characterized. The results indicated that cells interacted favorably with the scaffold. Moreover, cells migrated into the highly porous three dimensional matrix of the scaffold and organized into dense multi-layered structures that resembled dermal structure. The results of collagen gel assay also revealed that gel contraction was enhanced by the presence of the scaffold. The additional mechanical strength provided by the scaffold could enhance the binding of the seeded fibroblasts. These findings suggested that Dextran/PLGA scaffold can potentially be useful in enhancing the healing of chronic or trauma wounds.

High resolution mechanical function in the intact porcine heart: mechanical effects of pacemaker location.

The necessity to quantify the mechanical function with high spatial resolution stemmed from the advancement of myocardial salvaging techniques. Since these therapies are localized interventions, a whole field technique with high spatial resolution was needed to differentiate the normal, diseased, and treated myocardium. We developed a phase correlation algorithm for measuring myocardial displacement at high spatial resolution and to determine the regional mechanical function in the intact heart. Porcine hearts were exposed and high contrast microparticles were placed on the myocardium. A pressure transducer, inserted into the left ventricle, synchronized the pressure (LVP) with image acquisition using a charge-coupled device camera. The deformation of the myocardium was measured with a resolution of 0.58+/-0.04 mm. Within the region of interest (ROI), regional stroke work (RSW), defined as the integral of LVP with respect to regional area, was determined on average at 21 locations with a resolution of 27.1+/-2.7 mm2. To alter regional mechanical function, the heart was paced at three different locations around the ROI. Independent of the pacemaker location, RSW decreased in the ROI. In addition, a gradient of increasing RSW in the outward direction radiating from the pacemaker was observed in all pacing protocols. These data demonstrated the ability to determine regional whole field mechanical function with high spatial resolution, and the significant alterations induced by electrical pacing.