Reviving matrix for nerve reconstruction in rat model of acute and chronic complete spinal cord injury.

This study aimed to investigate the innovative antigliotic guiding regenerative gel (AGRG) as reviving matrix for reconnection of spinal cord defect in rat models of complete acute and chronic spinal cord injury (SCI). In acute SCI, a 2 mm segment of the spinal cord (SC) was removed at Th7-Th8. Then AGRG was injected to the gap or left untreated. In chronic SCI, a 1 mm segment of the spinal cord (SC) was removed at Th7-Th8. One month later, the injured area was cleaned from connective and scar tissue, creating a gap of 2-3 mm. Then, AGRG was injected to the gap or left untreated. Functional, electrophysiological, histological and immunohistochemical assessments were performed. In acute SCI, at week 24, 75% of AGRG group showed a somatosensory evoked potential (SEP) signal. Appearance of myelin basic protein (MBP) was observed in the injured area in the AGRG group (p < 0.1), compared to the untreated group. In chronic SCI, 24 weeks after 2nd surgery, appearance of MBP, indicating presence of myelinated axons, was observed in AGRG group, compared to the untreated group (p < 0.01). These preliminary results suggest that AGRG can serve as a vital bridging station inducing regeneration of injured SC in acute and chronic cases of paraplegia.

Modified Hyaluronic Acid-Laminin-Hydrogel as Luminal Filler for Clinically Approved Hollow Nerve Guides in a Rat Critical Defect Size Model.

Hollow nerve guidance conduits are approved for clinical use for defect lengths of up to 3 cm. This is because also in pre-clinical evaluation they are less effective in the support of nerve regeneration over critical defect lengths. Hydrogel luminal fillers are thought to improve the regeneration outcome by providing an optimized matrix inside bioartificial nerve grafts. We evaluated here a modified hyaluronic acid-laminin-hydrogel (M-HAL) as luminal filler for two clinically approved hollow nerve guides. Collagen-based and chitosan-based nerve guides were filled with M-HAL in two different concentrations and the regeneration outcome comprehensively studied in the acute repair rat sciatic nerve 15 mm critical defect size model. Autologous nerve graft (ANG) repair served as gold-standard control. At 120 days post-surgery, all ANG rats demonstrated electrodiagnostically detectable motor recovery. Both concentrations of the hydrogel luminal filler induced improved regeneration outcome over empty nerve guides. However, neither combination with collagen- nor chitosan-based nerve guides resulted in functional recovery comparable to the ANG repair. In contrast to our previous studies, we demonstrate here that M-HAL slightly improved the overall performance of either empty nerve guide type in the critical defect size model.

In Vivo and In Vitro Evaluation of a Novel Hyaluronic Acid-Laminin Hydrogel as Luminal Filler and Carrier System for Genetically Engineered Schwann Cells in Critical Gap Length Tubular Peripheral Nerve Graft in Rats.

In the current study we investigated the suitability of a novel hyaluronic acid-laminin hydrogel (HAL) as luminal filler and carrier system for co-transplanted cells within a composite chitosan-based nerve graft (CNG) in a rat critical nerve defect model. The HAL was meant to improve the performance of our artificial nerve guides by giving additional structural and molecular support to regrowing axons. We filled hollow CNGs or two-chambered nerve guides with an inserted longitudinal chitosan film (CNG[F]s), with cell-free HAL or cell-free HA or additionally suspended either naïve Schwann cells (SCs) or fibroblast growth factor 2-overexpressing Schwann cells (FGF2-SCs) within the gels. We subjected female Lewis rats to immediate 15 mm sciatic nerve gap reconstruction and comprehensively compared axonal and functional regeneration parameters with the gold standard autologous nerve graft (ANG) repair. Motor recovery was surveyed by means of electrodiagnostic measurements at 60, 90, and 120 days post-reconstruction. Upon explantation after 120 days, lower limb target muscles were harvested for calculation of muscle-weight ratios. Semi-thin cross-sections of nerve segments distal to the grafts were evaluated histomorphometrically. After 120 days of recovery, only ANG treatment led to full motor recovery. Surprisingly, regeneration outcomes revealed no regeneration-supportive effect of HAL alone and even an impairment of peripheral nerve regeneration when combined with SCs and FGF2-SCs. Furthermore, complementary in vitro studies, conducted to elucidate the reason for this unexpected negative result, revealed that SCs and FGF2-SCs suspended within the hydrogel relatively downregulated gene expression of regeneration-supporting neurotrophic factors. In conclusion, cell-free HAL in its current formulation did not qualify for optimizing regeneration outcome through CNG[F]s. In addition, we demonstrate that our HAL, when used as a carrier system for co-transplanted SCs, changed their gene expression profile and deteriorated the pro-regenerative milieu within the nerve guides.

Reviving Matrix for Nerve Reconstruction in Rabbit Model of Chronic Peripheral Nerve Injury With Massive Loss Defect.

Background and Aims: The aim of this study was to investigate the innovative guiding regenerative gel (GRG) and antigliotic GRG (AGRG) fillings for nerve conduits, prepared with Food and Drug Administration (FDA)-approved agents and expected to provide an alternative to autologous nerve graft and to enable reconnection of massive nerve gaps in a rabbit model of chronic peripheral nerve injury with massive loss defect that simulates the human condition of chronic injury with a large gap. Methods: The components and dosimetry for GRG and AGRG formulations were investigated in vitro on nerve cell culture and in vivo on 10-mm reconstructed sciatic nerves of 72 rats using different concentrations of agents and completed on a rabbit model of delayed (chronic) complete peripheral nerve injury with a 25-mm gap. Forty rabbits underwent delayed (9 weeks after complete injury of the tibial portion of the sciatic nerve) nerve tube reconstruction of a gap that is 25 mm long. GRG and AGRG groups were compared with autologous and empty tube reconstructed groups. Rats and rabbits underwent electrophysiological and histochemical assessments (19 weeks for rats and 40 weeks for rabbits). Results: Application of AGRG showed a significant increase of about 78% in neurite length per cell and was shown to have the most promising effect on neuronal outgrowth, with total number of neurites increasing by 4-fold. The electrophysiological follow-up showed that AGRG treatment is most promising for the reconstruction of the tibial portion of the sciatic nerve with a critical gap of 25 mm. The beneficial effect of AGRG was found when compared with the autologous nerve graft reconstruction. Thirty-one weeks post the second surgery (delayed reconstruction), histochemical observation showed significant regeneration after using AGRG neurogel, compared with the empty tube, and succeeded in significantly regenerating the nerve, as well as the autologous nerve graft, which was almost similar to a healthy nerve. Conclusion: We demonstrate that in the model of delayed peripheral nerve repair with massive loss defect, the application of AGRG led to a stronger nerve recovery and can be an alternative to autologous nerve graft.

Improving the Mechanical Rigidity of Hyaluronic Acid by Integration of a Supramolecular Peptide Matrix.

Hyaluronic acid (HA), a major component of the extracellular matrix, is an attractive material for various medical applications. Yet, its low mechanical rigidity and fast in vivo degradation hinder its utilization. Here, we demonstrate the reinforcement of HA by its integration with a low-molecular-weight peptide hydrogelator to produce a composite hydrogel. The formulation of HA with the fluorenylmethoxycarbonyl diphenylalanine (FmocFF) peptide, one of the most studied self-assembling hydrogel-forming building blocks, showing notable mechanical properties, resulted in the formation of stable, homogeneous hydrogels. Electron microscopy analysis demonstrated a uniform distribution of the two matrices in the composite forms. The composite hydrogels showed improved mechanical properties and stability to enzymatic degradation while maintaining their biocompatibility. Moreover, the storage modulus of the FmocFF/HA composite hydrogels reached up to 25 kPa. The composite hydrogels allowed sustained release of curcumin, a hydrophobic polyphenol showing antioxidant, anti-inflammatory, and antitumor activities. Importantly, the rate of curcumin release was modulated as a function of the concentration of the FmocFF peptide within the hydrogel matrix. This work provides a new approach for conferring mechanical rigidity and stability to HA without the need of cross-linking, thus potentially facilitating its utilization in different clinical applications, such as sustained drug release.

Exostosin 1 is expressed in human odontoblasts.

OBJECTIVE: Dental pulp is soft connective tissue maintaining the vitality of the tooth, while odontoblasts form the dentin. Our earlier DNA microarray analysis revealed expression of putative tumour suppressor exostosin 1 (EXT-1) in odontoblasts. EXT-1 is essential for heparan sulphate synthesis, which may play a role in the dentin mineralization. Since the absence of the functional EXT-1 causes bone tumours, expression in odontoblasts is interesting. Our aim was to analyse further the EXT-1 expression in human tooth. DESIGNS: DNA microarray and PCR techniques were used to study the EXT-1 expression in mature native human odontoblasts and pulp tissue as well as in newly-differentiated cultured odontoblast-like cells. Immunohistochemistry was performed to study EXT-1 protein in mature human teeth, teeth with incomplete root and developing teeth. RESULTS: Markedly higher EXT-1 was observed in mature odontoblasts than in pulp at mRNA level with DNA microarray and PCR techniques. Immunohistochemistry of mature tooth revealed EXT-1 both in odontoblasts and the predentin but not in the dentin. EXT-1 was also observed in the odontoblasts of incomplete root, but the localization of the staining was different. In developing foetal tooth, staining was detected in ameloblasts and the basal lamina. CONCLUSIONS: The detection of EXT-1 in both mature and newly-differentiated cells indicates a role in the odontoblast function, and EXT-1 staining in the predentin indicates a function in the dentin formation. Detection of EXT-1 in developing teeth indicates a role in tooth development.

Angiotensin converting-enzyme inhibition restores glomerular glycosaminoglycans in rat puromycin nephrosis.

BACKGROUND: Aberrant glomerular polyanionic charge of glycosaminoglycans (GAGs) and sialic acid expression has been observed in proteinuric human and experimental glomerular diseases. Angiotensin-converting enzyme inhibitors (ACEI) lower proteinuria and amend renal function deterioration via hemodynamic mechanisms. We tested the hypothesis that ACEI modulate proteinuria additionally by modifying glomerular GAGs. METHODS: In this study, we explored the effects of the ACEI enalapril on proteinuria and GAG synthesis in puromycin aminonucleoside (PAN)-treated rats. We employed cationic colloidal gold (CCG) localization in glomerular basement membranes (GBM) to identify GAGs by electron microscopy and determined sialic acid residues by immunohistochemical staining with lectins. To clarify ACEI effects on GAG production in vitro, we studied de novo GAG synthesis into newly synthesized proteoglycans in podocytes and mesangial cells using 35S incorporation. Cells were incubated with or without PAN, and with increasing doses of the ACEI enalaprilat. RESULTS: PAN rats developed severe proteinuria that was significantly improved by enalapril treatment. In non-treated PAN rats GBM GAGs were reduced, whereas in the enalapril-treated group GBM GAGs were significantly increased to control levels. Enalapril did not affect glomerular sialic acid. Furthermore, in cultured podocytes and mesangial cells PAN decreased de novo GAG synthesis, an effect which was significantly ameliorated by enalaprilat treatment. CONCLUSION: Treatment with ACEI improves permselectivity properties of the glomerular capillary wall by maintaining its GAG content. This finding provides an additional new mechanism, whereby ACEI exert anti-proteinuric effects.

Changes in the basal membrane of dorsal root ganglia Schwann cells explain the biphasic pattern of the peripheral neuropathy in streptozotocin-induced diabetic rats.

Peripheral neuropathy is one of the main complications of diabetes mellitus. The current study demonstrated the bimodal pattern of diabetic peripheral neuropathy found in the behavioral study of pain perception in parallel to the histopathological findings in dorsal root ganglia (DRGs) neurons and satellite Schwann cell basement membranes. A gradual decrease in heparan sulfate content, with a reciprocal increase in deposited laminin in the basement membranes of dorsal root ganglia Schwann cells, was shown in streptozotocin-treated rats. In addition, the characteristic biphasic pain profiles were demonstrated in diabetic rats, as shown by hypersensitivity at the third week and hyposensitivity at the tenth week post-streptozotocin injection, accompanied by a continuous decrease in the sciatic nerve conduction velocity. It appears that these basal membrane abnormalities in content of heparan sulfate and laminin, noticed in diabetic rats, may underline the primary damage in dorsal ganglion sensory neurons, simultaneously with the bimodal painful profile in diabetic peripheral neuropathy, simulating the scenario of filtration rate in diabetic kidney.

Recovery of peripheral nerve with massive loss defect by tissue engineered guiding regenerative gel.

OBJECTIVE: Guiding Regeneration Gel (GRG) was developed in response to the clinical need of improving treatment for peripheral nerve injuries and helping patients regenerate massive regional losses in peripheral nerves. The efficacy of GRG based on tissue engineering technology for the treatment of complete peripheral nerve injury with significant loss defect was investigated. BACKGROUND: Many severe peripheral nerve injuries can only be treated through surgical reconstructive procedures. Such procedures are challenging, since functional recovery is slow and can be unsatisfactory. One of the most promising solutions already in clinical practice is synthetic nerve conduits connecting the ends of damaged nerve supporting nerve regeneration. However, this solution still does not enable recovery of massive nerve loss defect. The proposed technology is a biocompatible and biodegradable gel enhancing axonal growth and nerve regeneration. It is composed of a complex of substances comprising transparent, highly viscous gel resembling the extracellular matrix that is almost impermeable to liquids and gasses, flexible, elastic, malleable, and adaptable to various shapes and formats. Preclinical study on rat model of peripheral nerve injury showed that GRG enhanced nerve regeneration when placed in nerve conduits, enabling recovery of massive nerve loss, previously unbridgeable, and enabled nerve regeneration at least as good as with autologous nerve graft "gold standard" treatment.

Chitosan-hyaluronate hybrid gel intraarticular injection delays osteoarthritis progression and reduces pain in a rat meniscectomy model as compared to saline and hyaluronate treatment.

Chitosan-Hyaluronate hybrid gel (CHHG) is a self-forming thermo-responsive hydrogel. The current study was undertaken in order to assess the effect of CHHG on rat's surgically induced osteoarthritis. Methods. Thirteen rats were included in the study. In all rats weight-bearing was assessed using a Linton Incapacitance tester. All rats underwent bilateral medial partial meniscectomy. Four rats received a saline injection in the control knee and a 200-microliter injection of CHHG in the experimental knee. Five rats received a high-molecular weight hyaluronate injection to the control knee and a 200-microliter injection of CHHG in the experimental knee. Four rats underwent the same surgical procedure, allowed to recuperate for seven days and then CHHG and hyaluronate were injected. The animals were followed for 6 weeks. Two weeks after injection of a therapeutic substance the amount of weight-bearing on each knee was evaluated using a Linton Incapacitance meter. Results. Two weeks after induction of osteoarthritis there is less pain in the CHHG-treated knee than in the control-treated knee, as determined using a Lintron Incapacitance meter. After six-weeks the histological appearance of the CHHG-treated knee was superior to that of the controls. This is indicated by thicker cartilage remaining on the medial femoral condyle as well as less cyst formation in the CHHG-treated knee. Discussion. CHHG appears to delay progression of osteoarthritis and lessen pain in a rat surgically-induced knee osteoarthritis model. These results support other published results, indicating that there is an ameliorative effect of chitosan on human and rabbit osteoarthritis.

ß-D-xylosides stimulate GAG synthesis in chondrocyte cultures due to elevation of the extracellular GAG domains, accompanied by the depletion of the intra-pericellular GAG pools, with alterations in the GAG profiles.

The familial disease of hereditary multiple exostoses is characterized by abnormal skeletal deformities requiring extensive surgical procedures. In hereditary multiple exostoses patients there is a shortage in the pericellular glycosaminoglycan (GAG) of heparan sulfate (HS), related to defective activity of HS glycosyltransferases, mainly in the pericellular regions of chondrocytes. This study searched for a novel approach employing xylosides with different aglycone groups priming a variety of GAG chains, in attempting to alter the GAG compositional profile. Cell cultures of patients with osteochondroma responded to p-nitrophenyl ß-D-xyloside by a significant increase in total GAG synthesis, expressed mainly in the extracellular domains, limited to chondroitin sulfate). The different ß-D-xylosides, in addition to increasing the synthesis of extracellular GAGs, led to a significant depletion of the intracellular GAG domains. In mouse chondrocyte cultures, ß-D-xylosides with different aglycones created a unique distribution of the GAG pools. Of special interest was the finding that the naphthalene methanol ß-D-xyloside showed the highest absolute levels of HS-GAGs in both extracellular and intra-pericellular moieties compared with other ß-D-xylosides and with controls without xyloside. In summary, ß-D-xylosides can be utilized in chondrocyte cultures to modify the distribution of GAGs between the extracellular and intracellular compartments. In addition, xylosides may alter the profile of specific GAG chains in each moiety.

The structural, compositional and mechanical features of the calcite shell of the barnacle Tetraclita rufotincta.

The microstructure and chemical composition of the calcite shell of the sea barnacle Tetraclita rufotincta (Pilsbry, 1916) were investigated using microscopic and analytical methods. The barnacle shell was separated mechanically into its three substructural units: outer, interior, and inner layers. The organic matrices of these structural parts were further separated into soluble and insoluble constituents and their characteristic functional groups were studied by FTIR. Investigation of the mechanical properties of the interior mass of the shell reveals remarkable viscoelastic behavior. In general, the mechanical behavior of the shell is a function of its geometry as well as of the material, of which it is constructed. In the case of T. rufotincta, as calcite is a brittle material, the elastic behavior of the shell is apparently related to its micro- and macroarchitecture. The latter enables the shell to fulfill its primary function which is to protect the organism from a hostile environment and enables its survival. Our detailed identification of the similarities and differences between the various structural components of the shell in regard to the composition and properties of the organic component will hopefully throw light on the role of organic matrices in biomineralization processes.

Hyaluronan and mesenchymal stem cells: from germ layer to cartilage and bone.

A simple, linear polysaccharide with unique molecular functions, hyaluronan is a glycosaminoglycan whose biomechanical and hydrodynamic properties have been thoroughly characterized. However, the exact role the molecular mechanisms and signaling pathways of hyaluronan play in the regulation of stem cell fate, such as self-renewal and differentiation, remains to be determined. The abundance of hyaluronan in embryonic tissues indicates that it is highly important in developmental processes. Recent studies have focused on understanding the mechanisms of hydrated hyaluronan action and its interaction with neighboring substances. This review is an attempt to elucidate the complex role of hyaluronan signaling in the initialization and regulation of developmental processes, particularly in events dictating the fates of mesenchymal stem cells during the organogenetic phases of chondrogenesis and osteogenesis.

Crystalline calcium carbonate and hydrogels as microenvironment for stem cells.

Stem cell development and fate decisions are dictated by the microenvironment in which the stem cell is embedded. Among the advanced goals of tissue engineering is the creation of a microenvironment that will support the maintenance and differentiation of the stem cell--based on embryonic and adult stem cells as potent, cellular sources--for a variety of clinical applications. This review discusses some of the approaches used to create regulatory and instructive microenvironments for the directed differentiation of mesenchymal stem cells (MSCs) using three-dimensional crystalline calcium carbonate biomaterials of marine origin combined with a hydrated gel based on hyaluronan.

Common skeletal growth retardation disorders resulting from abnormalities within the mesenchymal stem cells reservoirs in the epiphyseal organs pertaining to the long bones.

Among the objectives in writing the current chapter were the curiosity and the interest in allocating the sites and routes of migration of the reservoirs of the mesenchymal precartilaginous stem cells of the developing limbs in health and in disease. We chose to emphasize the events believed to initiate in these regions of stem cells, which may lead to growth retardation disorders. Thus, this narrow niche touches an enlarged scope of developmental biology angles and fields. The enclosed coverage sheds light on part of the musculoskeletal system, skeletogenesis, organogenesis of mobile structures and organs, the limbs, joints and digits (arthrology). It appears that the key role of the cartilage-bone regions is their responsibility to replenish the physis with committed chondrocytes, during the developmental, maturation and puberty periods. We shall start by outlining the framework of normal limb formation, the modalities, signals and the agents participating in this biological creation and regulation, illustrating potential sites that might deviate from normal development during the growth periods.

Increase of neuronal sprouting and migration using 780 nm laser phototherapy as procedure for cell therapy.

BACKGROUND AND OBJECTIVES: The present study focuses on the effect of 780 nm laser irradiation on the growth of embryonic rat brain cultures embedded in NVR-Gel (cross-linked hyaluronic acid with adhesive molecule laminin and several growth factors). Dissociated neuronal cells were first grown in suspension attached to cylindrical microcarriers (MCs). The formed floating cell-MC aggregates were subsequently transferred into stationary cultures in gel and then laser treated. The response of neuronal growth following laser irradiation was investigated. MATERIALS AND METHODS: Whole brains were dissected from 16 days Sprague-Dawley rat embryos. Cells were mechanically dissociated, using narrow pipettes, and seeded on positively charged cylindrical MCs. After 4-14 days in suspension, the formed floating cell-MC aggregates were seeded as stationary cultures in NVR-Gel. Single cell-MC aggregates were either irradiated with near-infrared 780 nm laser beam for 1, 4, or 7 minutes, or cultured without irradiation. Laser powers were 10, 30, 50, 110, 160, 200, and 250 mW. RESULTS: 780 nm laser irradiation accelerated fiber sprouting and neuronal cell migration from the aggregates. Furthermore, unlike control cultures, the irradiated cultures (mainly after 1 minute irradiation of 50 mW) were already established after a short time of cultivation. They contained a much higher number of large size neurons (P<0.01), which formed dense branched interconnected networks of thick neuronal fibers. CONCLUSIONS: 780 nm laser phototherapy of embryonic rat brain cultures embedded in hyaluronic acid-laminin gel and attached to positively charged cylindrical MCs, stimulated migration and fiber sprouting of neuronal cells aggregates, developed large size neurons with dense branched interconnected network of neuronal fibers and, therefore, can be considered as potential procedure for cell therapy of neuronal injury or disease.

The molecular and cellular basis of exostosis formation in hereditary multiple exostoses.

The different clinical entities of osteochondromas, hereditary multiple exostoses (HME) and non-familial solitary exostosis, are known to express localized exostoses in their joint metaphyseal cartilage. In the current study biopsies of osteochondromas patients were screened with respect to a number of cellular and molecular parameters. Specifically, cartilaginous biopsy samples of nine HME patients, 10 solitary exostosis patients and 10 articular cartilages of control subjects were collected and cell cultures were established. Results obtained showed that one of the two HME samples that underwent DNA sequencing analysis (HME-1) had a novel mutation for an early stop codon, which led to an aberrant protein, migrating at a lower molecular weight position. The EXT-1 mRNA and protein levels in chondrocyte cultures derived from all nine HME patients were elevated, compared with solitary exostosis patients or control subjects. Furthermore, cell cultures of HME patients had significantly decreased pericellular heparan sulphate (HS) in comparison with cultures of solitary exostosis patients or control subjects. Immunohistochemical staining of tissue sections and Western blotting of cell cultures derived from HME patients revealed higher levels of heparanase compared with solitary exostosis patients and of control subjects. Further investigations are needed to determine whether the low pericellular HS levels in HME patients stem from decreased biosynthesis of HS, increased degradation or a combination of both. In conclusion, it appears that due to a mutated glycosyltransferase, the low content of pericellular HS in HME patients leads to the anatomical deformations with exostoses formation. Hence, elevation of HS content in the pericellular regions should be a potential molecular target for correction.

Experimental repair of tracheal defects using a new biodegradable membrane.

BACKGROUND: The increasing number of newborns requiring intubation and artificial ventilation in the sophisticated premature and intensive care units of recent years has been followed by a concomitant increase in the number of children who develop tracheal stenosis as a sequela of prolonged intubation, with a consequent increasing need for tracheal surgical repair. This study was designed to evaluate the ability of a new tissue-engineered biodegradable membrane to tightly seal significant tracheal defects. MATERIALS AND METHODS: A surgically induced tracheal defect of 10 x 5 mm was repaired in rabbits using the NVR-7 membrane--a cross-linked copolymer derived from a dextran sulphate gelatin construct. The unique features of this new membrane are biocompatibility, biodegradability, elasticity, and suturability, as well as a smooth sterilization process. The animals were sacrificed and the tracheas examined at 2, 3, 4, and 8 weeks postsurgery. RESULTS: Seven (7) of 8 rabbits undergoing tracheal surgery survived, with a tight air seal and an almost normal airway. Macroscopic and microscopic studies of the removed specimens showed variable degrees of immunogenic reaction toward the membrane. In the long term (2-3 months), a complete regeneration of all the tracheal layers occurred, simulating the original structure and orderly arrangement of a normal trachea. CONCLUSIONS: The surgical correction using the above membrane enabled the operated animals to overcome any respiratory distress, adequately correcting the induced tracheal defect. From this experimental study, we conclude that the new NVR-7 membrane appears to be a promising therapeutic adjunct in the treatment of patients with tracheal defects.

Immediate tight sealing of skin incisions using an innovative temperature-controlled laser soldering device: in vivo study in porcine skin.

BACKGROUND: A feedback temperature-controlled laser soldering system (TCLS) was used for bonding skin incisions on the backs of pigs. The study was aimed: 1) to characterize the optimal soldering parameters, and 2) to compare the immediate and long-term wound healing outcomes with other wound closure modalities. MATERIALS AND METHODS: A TCLS was used to bond the approximated wound margins of skin incisions on porcine backs. The reparative outcomes were evaluated macroscopically, microscopically, and immunohistochemically. RESULTS: The optimal soldering temperature was found to be 65 degrees C and the operating time was significantly shorter than with suturing. The immediate tight sealing of the wound by the TCLS contributed to rapid, high quality wound healing in comparison to Dermabond or Histoacryl cyanoacrylate glues or standard suturing. CONCLUSIONS: TCLS of incisions in porcine skin has numerous advantages, including rapid procedure and high quality reparative outcomes, over the common standard wound closure procedures. Further studies with a variety of skin lesions are needed before advocating this technique for clinical use.

Repair of articular cartilage lesions in aged chickens by allogeneic transplantation of fresh embryonic epiphyses.

INTRODUCTION: The potential of fresh whole chick epiphyses of embryonic origin to serve as implant material for cartilage defects of aged chicken was tested. MATERIALS AND METHODS: Fresh epiphyses of 11-day-old embryos were collected from 24 animals and transplanted into defects created in the weight-bearing areas of tibiotarsal joint cartilage of 2-year-old chicks. Upon sacrifice, samples were examined macroscopically and microsections were prepared for histology. RESULTS: Macroscopically, control defects remained empty at all the time intervals. Defects of the experimental group were, on the other hand, filled with cartilaginous tissue as early as 2 weeks posttransplantation, although individual epiphyses could still be noted in the implant tissue. At 4 weeks and later, defects were filled with cartilaginous material indistinguishable from hyaline cartilage. Histologically, all grafts remained within the defect's pits, showing mitotic and metabolic activity typical to proliferating hyaline cartilage. The engrafted epiphyses showed a partial incorporation and integration with the surrounding host tissues already at 2 weeks. At 4 weeks and later, the integration was complete. CONCLUSIONS: It is concluded that a chick embryonic epiphyseal cartilage is suitable as a graft source for articular cartilage transplantation. The embryonic epiphyses provide immediate inherent stability to the graft and supply a good mix of mesenchymal progenitor cells responsible for the high rate of cell proliferation and adhesion to the differentiated committed chondrocytes of the host that create the typical favorable chondrogenic milieu. Based on the present findings, it is postulated that human embryonic epiphyses may, in the future, represent an alternative source to the commonly used techniques of hyaline cartilage repair.