Short and long gap peripheral nerve repair with magnesium metal filaments.

A current clinical challenge is to replace autografts for repair of injury gaps in peripheral nerves, which can occur due to trauma or surgical interruption. Biodegradable metallic magnesium filaments, placed inside hollow nerve conduits, could support nerve repair by providing contact guidance support for axonal regeneration. This was tested by repairing sciatic nerves of adult rats with single magnesium filaments placed inside poly(caprolactone) nerve conduits. Controls were empty conduits, conduits containing titanium filaments and/or isografts from donor rats. With a nerve gap of 6 mm and 6 weeks post-repair, magnesium filaments had partially resorbed. Regenerating cells had attached to the filaments and axons were observed in distal stumps in all animals. Axon parameters were improved with magnesium compared to conduits alone or conduits with single titanium filaments. With a longer gap of 15 mm and 16 weeks post-repair, functional parameters were improved with isografts, but not with magnesium filaments or empty conduits. Magnesium filaments were completely resorbed and no evidence of scarring was seen. While axon outgrowth was not improved with the longer gap, histological measures of the tissues were improved with magnesium compared to empty conduits. Therefore, the use of magnesium filaments is promising because they are biocompatible and improve aspects of nerve regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3148-3158, 2017.

Ethylene Oxide Sterilization Preserves Bioactivity and Attenuates Burst Release of Encapsulated Glial Cell Line Derived Neurotrophic Factor from Tissue Engineered Nerve Guides For Long Gap Peripheral Nerve Repair.

Synthetic nerve guides are widely utilized to reconstruct peripheral nerve defects that are less than three centimeters. However, there are no clinically available nerve guides that are approved to promote repair over long gaps (>3 cm). Many currently available guides are unable to sustain large defect regeneration either because of limitations in fabrication or short degradation times in vivo. Furthermore, current clinically available nerve guides do not contain neurotrophic factor delivery systems to promote nerve tissue regeneration over long gaps. The purpose of this paper is to describe the manufacturing parameters and sterilization procedures of a 5.2 cm poly(caprolactone) nerve conduit with embedded polymeric microspheres that encapsulate glial cell line-derived neurotrophic factor (GDNF) for implantation into a preclinical rhesus macaque 5 cm median nerve defect model. Nerve conduits were sterilized with room temperature ethylene oxide (RT EtO) and assessed for morphology as well as maintenance of porosity. Release kinetics and bioactivity of GDNF were also assessed in RT EtO sterilized guides. Scanning electron microscopy indicated that RT EtO treatment did not affect morphology and porosity percentage of nerve guides. Furthermore, RT EtO had no effect on GDNF bioactivity based on Schwannoma cell migration studies. RT EtO guides exhibited significantly slowed GDNF release compared to GDNF release from nonsterile guides indicating that EtO treatment may enhance the long-term delivery kinetics of GDNF from polymeric microspheres within the nerve guide.

Initial observations on using magnesium metal in peripheral nerve repair.

Biodegradable magnesium metal filaments placed inside biodegradable nerve conduits might provide the physical guidance support needed to improve the rate and extent of regeneration of peripheral nerves across injury gaps. In this study, we examined basic issues of magnesium metal resorption and biocompatibility by repairing sub-critical size gap injuries (6 mm) in one sciatic nerve of 24 adult male Lewis rats. Separated nerve stumps were connected with poly(caprolactone) nerve conduits, with and without magnesium filaments (0.25 mm diameter, 10 mm length), with two different conduit filler substances (saline and keratin hydrogel). At 6 weeks after implantation, magnesium degradation was examined by micro-computed tomography and histological analyses. Magnesium degradation was significantly greater when the conduits were filled with an acidic keratin hydrogel than with saline (p < 0.05). But magnesium filaments in some animals remained intact for 6 weeks. Using histological and immunocytochemical analyses, good biocompatibility of the magnesium implants was observed at 6 weeks, as shown by good development of regenerating nerve mini-fascicles and only mild inflammation in tissues even after complete degradation of the magnesium. Nerve regeneration was not interrupted by complete magnesium degradation. An initial functional evaluation, determination of size recovery of the gastrocnemius muscle, showed a slight improvement due to magnesium with the saline but not the keratin filler, compared with respective control conduits without magnesium. These results suggest that magnesium filament implants have the potential to improve repair of injured peripheral nerve defects in this rodent model.

Exogenous connective tissue growth factor preserves the hair-inductive ability of human dermal papilla cells.

Connective tissue growth factor influences human dermal papilla cells' hair inductive ability through several signaling pathways.

Assessments of injectable alginate particle-embedded fibrin hydrogels for soft tissue reconstruction.

Soft tissue reconstruction is often needed after massive traumatic damage or cancer removal. In this study, we developed a novel hybrid hydrogel system consisting of alginate particles and a fibrin matrix that could maintain tissue volume long term. Alginate particles were fabricated by mixing 5% alginate with a 20 mM calcium solution. Cells and these alginate particles were then embedded in fibrin (alginate-fibrin) hydrogels using a dual syringe mixer. Cell-hydrogel constructs were evaluated in terms of cell survival and proliferation in the constructs in vitro. The results indicated that cellular viability, spreading and proliferation in the alginate-fibrin hydrogels were significantly higher compared to constructs fabricated with fibrin or alginate only. In vivo explants showed that cells contained within fibrin-only hydrogels did not contribute to neo-tissue formation, and the fibrin was fully degraded within a 12 week period. In the alginate-fibrin system, higher cellularity and vascular ingrowth were observed in vivo. This resulted in neo-tissue formation in the alginate-fibrin hydrogels. These results demonstrate that fibrin may enhance cell proliferation and accelerate the formation of extracellular matrix proteins in the alginate-fibrin system, while the alginate particles could contribute to volume retention. This injectable hybrid system composed of degradable and non-degradable hydrogels may be a preferable approach to the repair of soft tissue defects.

Adipose stem cells for soft tissue regeneration.

Adipose-derived stem cells (ASCs) can be isolated from human adipose tissue with the exceptional potential for differentiation into mature adipocytes. Utilization of this system is very promising in developing improved techniques to repair soft tissue defects. Current reconstructive procedures, especially after trauma and oncological surgery, transfer autologous soft tissue grafts having limitations. However, ASCs offer the ability to either generate soft tissue with no donor-site morbidity (with the exception of a minor loss of adipose tissue) or enhance the viability and durability of other grafts. This review will discuss the relevant properties of human adult adipose-derived stem cells for the regeneration of adipose tissue. Discussion will focus on the biology of ASCs, cell delivery vehicles/scaffolds useful in applying ASCs as a therapy, and suitable IN VIVO animal models for studying adipose tissue engineering. Also included is a description of the current clinical studies with ASCs in Europe and Asia.

Chondrogenesis, bone morphogenetic protein-4 and mesenchymal stem cells.

OBJECTIVE: As adult cartilage has very limited potential to regenerate, cartilage repair is challenging. Available treatments have several disadvantages, including formation of fibrocartilage instead of hyaline-like cartilage, as well as eventual ossification of the newly formed tissue. The focus of this review is the application of bone morphogenetic protein-4 (BMP-4) and mesenchymal stem cells (MSCs) in cartilage repair, a combination that could potentially lead to the formation of permanent hyaline-like cartilage in the defect. METHODS: This review is based on recent literature in the orthopaedic and tissue engineering fields, and is focused on MCSs and bone morphogenetic proteins (BMPs). RESULTS: BMP-4, a stimulator of chondrogenesis, both in vitro and in vivo, is a potential therapeutic agent for cartilage regeneration. BMP-4 delivery can improve the healing process of an articular cartilage defect by stimulating the synthesis of the cartilage matrix constituents: type II collagen and aggrecan. BMP-4 has also been shown to suppress chondrogenic hypertrophy and maintain regenerated cartilage. Use of an appropriate carrier for BMP-4 is crucial for successful reconstruction of cartilage defects. Due to the relatively short half-life in vivo of BMP-4, there is a need to localize and maintain the delivery of BMP-4 to the injury site. Additionally, the delivery of MSCs to the wound site could improve cartilage regeneration; therefore, the carrier should function both as a cell and a protein delivery vehicle. CONCLUSION: The role of BMP-4 in chondrogenesis is significant, and successful methods to deliver BMP-4, with or without MSCs, to the cartilage defect site are a promising therapy to treat cartilage defects.

Rabbit calvarial wound healing by means of seeded Caprotite scaffolds.

Autologous bone is the most successful bone-grafting material; however, limited supply and donor site morbidity are problematic. Synthetic bone substitutes are effective, but healing is slow and unpredictable. Osseous wound healing may be enhanced if bone substitutes are combined with autologous bone marrow cells. To test this hypothesis, we created 40 calvarial defects in 20 12-week-old New Zealand White rabbits, divided into four groups: (1) unrepaired controls, (2) autologous bone grafts, (3) unseeded Caprotite (a polymer-ceramic composite) grafts, and (4) Caprotite grafts seeded with autologous bone marrow stromal cells. CT scans were obtained at 0, 6, and 12 weeks post-operatively, and defects were harvested for histology. Defects repaired with autologous bone had significantly (p < 0.05) more bone than the other three groups, although seeded Caprotite defects showed different wound-healing sequelae. Results suggest that seeded Caprotite scaffolds did not significantly enhance osseous defect healing compared with controls.

The influence of polymer blend composition on the degradation of polymer/hydroxyapatite biomaterials.

The in vitro degradation of biodegradable polymer/ceramic composites was assessed in two different environments under both static and pseudodynamic conditions. The blends, consisting of polycaprolactone, poly(lactic-co-glycolic acid), and hydroxyapatite, have potential use in bone tissue engineering applications, thus it is essential to establish a standardized method of characterizing the degradation of new biomaterials. In this study, the variation in polymer blend ratio was examined to observe a change in degradation rate. The porous blends were degraded in water and serum-containing media. A previous study examined in vitro degradation in serum-free buffer. Molecular weight loss, gravimetric weight loss, pH changes and morphological changes were evaluated. The changes in porosity were observed with scanning electron microscopy and quantitatively assessed using image analysis. There was a significant difference in molecular weight loss and gravimetric weight loss between the blends after 10 weeks in vitro. Blends containing the greatest amount of poly(lactic-co-glycolic acid) degraded most rapidly.

Controlled release from coated polymer microparticles embedded in tissue-engineered scaffolds.

The controlled release of proteins in tissue-engineered implants is being examined with the potential application to improve vascularization and hasten tissue growth. Bovine serum albumin (BSA), was encapsulated within poly(D,L-lactic-co-glycolic acid) [PLGA] microparticles. The microparticles were coated with poly(vinyl alcohol) and incorporated into PLGA tissue-engineered scaffolds during fabrication. The release of BSA from PLGA microparticles, coated PLGA microparticles, and microparticles embedded in a porous PLGA scaffold was measured. We have developed a novel approach that will permit incorporation of coated polymeric microparticles during PLGA scaffold fabrication. Growth factors or drugs could be incorporated into the microparticles resulting in a long-term, controlled release.

Characterization of osteoblast-like behavior of cultured bone marrow stromal cells on various polymer surfaces.

The creation of novel bone substitutes requires a detailed understanding of the interaction between cells and materials. This study was designed to test certain polymers, specifically poly(caprolactone) (PCL), poly(D,L-lactic-CO-glycolic acid) (PLGA), and combinations of these polymers for their ability to support bone marrow stromal cell proliferation and differentiation. Bone marrow stromal cells were cultured from New Zealand White rabbits and were seeded onto glass slides coated with a thin layer of PCL, PLGA, and combinations of these two polymers in both a 40:60 and a 10:90 ratio. Growth curves were compared. At the end of 2 weeks, the cells were stained for both matrix mineralization and alkaline phosphatase activity. There was no statistically significant difference in growth rate of the cells on any polymer or polymer combination. However, there was a striking difference in Von Kossa staining and alkaline phosphatase staining. Cells on PCL did not show Von Kossa staining or alkaline phosphatase staining. However, in the 40:60 and 10:90 blends, there was both positive Von Kossa and alkaline phosphatase staining. These data indicate that PCL alone may not be a satisfactory material for the creation of a bone substitute. However, it may be used in combination with PLGA for the creation of a bone substitute material.

In vitro analysis of biodegradable polymer blend/hydroxyapatite composites for bone tissue engineering.

Blends of biodegradable polymers, poly(caprolactone) and poly(D, L-lactic-co-glycolic acid), have been examined as scaffolds for applications in bone tissue engineering. Hydroxyapatite granules have been incorporated into the blends and porous discs were prepared. Mechanical properties and degradation rates in vitro of the composites were determined. The discs were seeded with rabbit bone marrow or cultured bone marrow stromal cells and incubated under physiological conditions. Polymer/ceramic scaffolds supported cell growth throughout the scaffold for 8 weeks. Scanning and transmission electron microscopy, and histological analyses were used to characterize the seeded composites. This study suggests the feasibility of using novel polymer/ceramic composites as scaffold in bone tissue engineering applications.

Cytomimetic biomaterials. 3. Preparation and transport studies of an alginate/amphiphilic copolymer/polymerized phospholipid film.

The significance of molecular design methodologies based upon membrane-mimetic systems lies in the ability to engineer robust materials of varying geometry with a high degree of reproducibility and molecular control over surface order and chemistry. However, non-covalently associated assemblies, in and of themselves, are often insufficiently robust for many applications. We have previously reported the in situ polymerization of a single phospholipid monolayer on a self-assembled film of octadecyltrichrolosilane (OTS) on glass, as well as the polymerization of phospholipids on an amphiphilic, dialkyl-containing terpolymer bound to a gold-coated silicon wafer. We now report the polymerization of a phospholipid monolayer assembly onto an alkylated hydrogel substrate with significant alteration in both surface chemistry and mass transport properties at the hydrogel-water interface. A general platform is thereby created for enhancing the control of either the local delivery of specific macromolecules or the immunoisolation barrier for many cell based therapies.

A pain management documentation tool.

PURPOSE/OBJECTIVES: To describe the development, implementation, and evaluation of a tool to standardize assessment, monitoring, management, and documentation of acute and chronic pain in hospitalized patients. DATA SOURCES: A multidisciplinary hospital committee, nursing staff, a pain consultant, published standards, and hospital standards. DATA SYNTHESIS: A comprehensive pain flow sheet and pain protocol was developed to assess, monitor, document, and evaluate clients at risk for or with actual pain. The tool was designed to assess and document acute and chronic pain in patients with cancer. CONCLUSIONS: Based on an initial review of quality assurance indicators, the tool has demonstrated increased consistency in documentation of pain management activities. IMPLICATIONS FOR NURSING PRACTICE: The use of a pain assessment and management flow sheet with a pain protocol provides an organized, consistent approach that maximizes quality, cost-effective care.