The fibroblast and wound repair

Ultrasound-triggered piezocatalytic composite hydrogels for promoting bacterial-infected wound healing

Wound healing has become one of the basic issues faced by the medical community because of the susceptibility of skin wounds to bacterial infection. As such, it is highly desired to design a nanocomposite hydrogel with excellent antibacterial activity to achieve high wound closure effectiveness. Here, based on ultrasound-triggered piezocatalytic therapy, a multifunctional hydrogel is designed to promote bacteria-infected wound healing. Under ultrasonic vibration, the surface of barium titanate (BaTiO3, BT) nanoparticles embedded in the hydrogel rapidly generate reactive oxygen species (ROS) owing to the established strong built-in electric field, endowing the hydrogel with superior antibacterial efficacy. This modality shows intriguing advantages over conventional photodynamic therapy, such as prominent soft tissue penetration ability and the avoidance of serious skin phototoxicity after systemic administration of photosensitizers. Moreover, the hydrogel based on N-[tris(hydroxymethyl)methyl]acrylamide (THM), N-(3-aminopropyl)methacrylamide hydrochloride (APMH) and oxidized hyaluronic acid (OHA) exhibits outstanding self-healing and bioadhesive properties able to accelerate full-thickness skin wound healing. Notably, compared with the widely reported mussel-inspired adhesive hydrogels, OHA/THM-APMH hydrogel due to the multiple hydrogen bonds from unique tri-hydroxyl structure overcomes the shortage that catechol groups are easily oxidized, giving it long-term and repeatable adhesion performance. Importantly, this hybrid hydrogel confines BT nanoparticles to wound area and locally induced piezoelectric catalysis under ultrasound to eradicate bacteria, markedly improving the therapeutic biosafety and exhibits great potential for harmless treatment of bacteria-infected tissues.

3D-Printed Janus Piezoelectric Patches for Sonodynamic Bacteria Elimination and Wound Healing

Management of infected wounds has raised worldwide concerns. Attempts in this field focus on the development of intelligent patches for improving the wound healing. Here, inspired by the cocktail treatment and combinational therapy stratagem, we present a novel Janus piezoelectric hydrogel patch via 3-dimensional printing for sonodynamic bacteria elimination and wound healing. The top layer of the printed patch was poly(ethylene glycol) diacrylate hydrogel with gold-nanoparticle-decorated tetragonal barium titanate encapsulation, which realizes the ultrasound-triggered release of reactive oxygen species without leaking nanomaterials. The bottom layer is fabricated with methacrylate gelatin and carries growth factors for the cell proliferation and tissue reconstruction. Based on these features, we have demonstrated in vivo that the Janus piezoelectric hydrogel patch can exert substantial infection elimination activity under the excitation of ultrasound, and its sustained release of growth factors can promote tissue regeneration during wound management. These results indicated that the proposed Janus piezoelectric hydrogel patch had practical significance in sonodynamic infection alleviation and programmable wound healing for treating different clinical diseases.

Transient mechanical interactions between cells and viscoelastic extracellular matrix

During various physiological processes, such as wound healing and cell migration, cells continuously interact mechanically with a surrounding extracellular matrix (ECM). Contractile forces generated by the actin cytoskeleton are transmitted to a surrounding ECM, resulting in structural remodeling of the ECM. To better understand how matrix remodeling takes place, a myriad of in vitro experiments and simulations have been performed during recent decades. However, physiological ECMs are viscoelastic, exhibiting stress relaxation or creep over time. The time-dependent nature of matrix remodeling induced by cells remains poorly understood. Here, we employed a discrete model to investigate how the viscoelastic nature of ECMs affects matrix remodeling and stress profiles. In particular, we used explicit transient cross-linkers with varied density and unbinding kinetics to capture viscoelasticity unlike most of the previous models. Using this model, we quantified the time evolution of generation, propagation, and relaxation of stresses induced by a contracting cell in an ECM. It was found that matrix connectivity, regulated by fiber concentration and cross-linking density, significantly affects the magnitude and propagation of stress and subsequent matrix remodeling, as characterized by fiber displacements and local net deformation. In addition, we demonstrated how the base rate and force sensitivity of cross-linker unbinding regulate stress profiles and matrix remodeling. We verified simulation results using in vitro experiments performed with fibroblasts encapsulated in a three-dimensional collagen matrix. Our study provides key insights into the dynamics of physiologically relevant mechanical interactions between cells and a viscoelastic ECM.

Bioactive nano yarns as surgical sutures for wound healing

Surgical sutures are the most widely used medical device in any surgical procedure worldwide. In this study, modified electrospinning technique has been used as manufacturing technique to produce nanofiber bundles twisted simultaneously to obtain nanofiber yarns. Taking the advantage of nanofiber yarns in terms of biomimetic structure, mechanical strength and handling properties, the material is chosen. Curcumin, a natural compound is incorporated to the nanofiber yarns by blend electrospinning technique for its anti-inflammatory, antibiotic and wound healing properties. The synthesized nanofiber yarns were characterized by various characterization techniques such as XRD, FTIR, SEM, Tensile testing, stem cell interaction, hemocompatibility, bacterial response, drug release profiling and in vivo studies. Curcumin loaded nanofiber yarns demonstrated sustained release with improved antibacterial, antiplatelet, cell migration and stem cell interaction in vitro. The results from skin inflammation animal model revealed that curcumin laden nanofiber yarn suture manifested reduced inflammation and cellularity. The three dimensional structure, adequate mechanical strength and biological properties of the nanofiber yarn provide naive environment for wound healing with the balanced degradation of suture material in rat model.

Treatment of Skin Disorders with Aloe Materials

The skin is the largest organ and functions as a barrier to protect the underlying tissues against the elements and pathogens, while also fulfilling many physiological roles and biochemical functions such as preventing excessive water loss. Skin disorders vary greatly in terms of origin, severity, symptoms and affect persons of all ages. Many plants have been used for medicinal purposes since ancient times including the treatment of skin disorders and diseases. Aloe represents one of the earliest medicinal plant species mentioned in antique scriptures and even in rock art dating back thousands of years. Different Aloe species and materials have been used in the prevention and treatment of skin related disorders. Aloe vera is the most commonly used Aloe species for medicinal purposes. Some of the most prominent skin related applications and disorders that Aloe materials have been investigated for are discussed in this paper, which include cosmetic, radiation, cancer, wound and antimicrobial applications. Both in vitro and in vivo studies are included in the discussions of this paper and comprehensive summaries of all these studies are given in tables in each section. Although some contradictory results were obtained among studies, certain Aloe materials have shown excellent efficacy and exhibited potential for the treatment of skin related disorders and cosmetic applications.

Impact of diabetes on gingival wound healing via oxidative stress

The aim of this study is to investigate the mechanisms linking high glucose to gingival wound healing. Bilateral wounds were created in the palatal gingiva adjacent to maxillary molars of control rats and rats with streptozotocin-induced diabetes. After evaluating postsurgical wound closure by digital imaging, the maxillae including wounds were resected for histological examinations. mRNA expressions of angiogenesis, inflammation, and oxidative stress markers in the surgical sites were quantified by real-time polymerase chain reaction. Primary fibroblast culture from the gingiva of both rats was performed in high glucose and normal medium. In vitro wound healing and cell proliferation assays were performed. Oxidative stress marker mRNA expressions and reactive oxygen species production were measured. Insulin resistance was evaluated via PI3K/Akt and MAPK/Erk signaling following insulin stimulation using Western blotting. To clarify oxidative stress involvement in high glucose culture and cells of diabetic rats, cells underwent N-acetyl-L-cysteine treatment; subsequent Akt activity was measured. Wound healing in diabetic rats was significantly delayed compared with that in control rats. Nox1, Nox2, Nox4, p-47, and tumor necrosis factor-α mRNA levels were significantly higher at baseline in diabetic rats than in control rats. In vitro study showed that cell proliferation and migration significantly decreased in diabetic and high glucose culture groups compared with control groups. Nox1, Nox2, Nox4, and p47 expressions and reactive oxygen species production were significantly higher in diabetic and high glucose culture groups than in control groups. Akt phosphorylation decreased in the high glucose groups compared with the control groups. Erk1/2 phosphorylation increased in the high glucose groups, with or without insulin treatment, compared with the control groups. Impaired Akt phosphorylation partially normalized after antioxidant N-acetyl-L-cysteine treatment. Thus, delayed gingival wound healing in diabetic rats occurred because of impaired fibroblast proliferation and migration. Fibroblast dysfunction may occur owing to high glucose-induced insulin resistance via oxidative stress.

MAPK/ERK signalling is required for zebrafish cardiac regeneration

OBJECTIVES

To better understand the molecular mechanisms of regeneration and explore the potential signalling pathways as therapeutic targets for heart attacks.

RESULTS

After treatment with the MEK inhibitor AZD6244 upon cardiac injury, the core members in MAPK/ERK signalling-mek and erk-demonstrate elevated expression, and these proteins are deposited at the injury site in zebrafish. pERK is also induced in non-cardiomyocytes near the injury site. Furthermore, the induced expression of a dominant-negative form of MEK1 inhibits zebrafish cardiac regeneration, characterized by increased cardiac fibrosis (a hallmark of regenerative failure), reduced or delayed production of regenerative myocardium, and migration of FLI1⁺ endothelial cells, without direct inhibition of cardiomyocyte proliferation.

CONCLUSION

Appropriate activation of MAPK/ERK signalling is essential for zebrafish cardiac regeneration.

Exploring the dynamics of progenitor cells in the urethra after simulated birth trauma in mice

OBJECTIVE

To examine the alteration in the cellular dynamics of the urethral tissue after a simulated birth trauma in a mouse model.

MATERIALS AND METHODS

A total of 36 B6 mice received vaginal distention treatment, and four untreated mice were used as controls. Specimens were collected every 24 hours after the injury for 9 consecutive days and examined using immunofluorescent staining for cell markers including c-kit, smooth muscle actin (SMA), and vimentin. Confocal microscopy was used to localize the stained cells and determine the cell number.

RESULTS

The number of c-kit positive cells increased after the 1^st day and peaked on the 3^rd day. The amount of SMA positive cells rapidly reduced to its lowest count on the 1^st day and maintained a statistically significant low cell number than that at the basal level for 4 days after vaginal distension. The cell number finally returned to basal level on the 9^th day. The amount of vimentin positive cells increased dramatically after the 1^st day and plateaued from the 3^rd day to the 9^th day. The number of vimentin positive cells in the plateau phase was significantly higher than that of the control group.

CONCLUSION

Our study confirmed that the dynamic change in different cell types after the urethral injury was dependent on the nature and physiology of the wound repairing cells during the tissue healing process. It might be a simple animal model to study birth trauma repair; however, the varied progenitor cell activity in different species should also be considered.

Fibroblasts and Mesenchymal Stromal/Stem Cells Are Phenotypically Indistinguishable

BACKGROUND/AIMS

Human mesenchymal stromal/stem cells (MSCs), derived from many different tissues, are characterized by a fibroblast-like morphology, the expression of certain cell surface markers and their ability to differentiate into adipocytes, chondrocytes and osteoblasts. A number of studies have shown that MSCs share many characteristics with fibroblasts; however, there is no well-defined set of phenotypic characteristics that could distinguish between these 2 types of cells.

METHODS

We used 4 well-established human fibroblast strains from 3 different tissue sources and several human MSC strains from 2 different tissue sources to compare the phenotypic and immunological characteristics of these cells.

RESULTS

Fibroblast strains had a similar morphology to MSCs, expressed the same cell surface markers as MSCs and could also differentiate into adipocytes, chondrocytes and osteoblasts. Also, similar to MSCs, these fibroblasts were capable of suppressing T cell proliferation and modulating the immunophenotype of macrophages. We also show that MSCs deposit extracellular matrices of collagen type I and fibronectin, and express FSP1 in patterns similar to fibroblasts.

CONCLUSIONS

Based on currently accepted definitions for cultured human MSCs and fibroblasts, we could not find any immunophenotypic property that could make a characteristic distinction between MSCs and fibroblasts.

Role of the KATP channel in the protective effect of nicorandil on cyclophosphamide-induced lung and testicular toxicity in rats

This study is the first to investigate the role of the KATP channel in the possible protection mediated by nicorandil against cyclophosphamide-induced lung and testicular toxicity in rats. Animals received cyclophosphamide (150 mg/kg/day, i.p.) for 2 consecutive days and then were untreated for the following 5 days. Nicorandil (3 mg/kg/day, p.o.) was administered starting from the day of cyclophosphamide injection with or without glibenclamide (5 mg/kg/day, p.o.). Nicorandil administration significantly reduced the cyclophosphamide-induced deterioration of testicular function, as demonstrated by increases in the level of serum testosterone and the activities of the testicular 3β- hydroxysteroid, 17β-hydroxysteroid and sorbitol dehydrogenases. Furthermore, nicorandil significantly alleviated oxidative stress (as determined by lipid peroxides and reduced glutathione levels and total antioxidant capacity), as well as inflammatory markers (tumour necrosis factor-α and interleukin-1β), in bronchoalveolar lavage fluid and testicular tissue. Finally, the therapy decreased the levels of fibrogenic markers (transforming growth factor-β and hydroxyproline) and ameliorated the histological alterations (as assessed by lung fibrosis grading and testicular Johnsen scores). The co-administration of glibenclamide (a KATP channel blocker) blocked the protective effects of nicorandil. In conclusion, KATP channel activation plays an important role in the protective effect of nicorandil against cyclophosphamide-induced lung and testicular toxicity.

Identifying functional anti-Staphylococcus aureus antibodies by sequencing antibody repertoires of patient plasmablasts

Infection by Staphylococcus aureus is on the rise, and there is a need for a better understanding of host immune responses that combat S. aureus. Here we use DNA barcoding to enable deep sequencing of the paired heavy- and light-chain immunoglobulin genes expressed by individual plasmablasts derived from S. aureus-infected humans. Bioinformatic analysis of the antibody repertoires revealed clonal families of heavy-chain sequences and enabled rational selection of antibodies for recombinant expression. Of the ten recombinant antibodies produced, seven bound to S. aureus, of which four promoted opsonophagocytosis of S. aureus. Five of the antibodies bound to known S. aureus cell-surface antigens, including fibronectin-binding protein A. Fibronectin-binding protein A-specific antibodies were isolated from two independent S. aureus-infected patients and mediated neutrophil killing of S. aureus in in vitro assays. Thus, our DNA barcoding approach enabled efficient identification of antibodies involved in protective host antibody responses against S. aureus.

Periostin modulates myofibroblast differentiation during full-thickness cutaneous wound repair

The matricellular protein periostin is expressed in the skin. Although periostin has been hypothesized to contribute to dermal homeostasis and repair, this has not been directly tested. To assess the contribution of periostin to dermal healing, 6 mm full-thickness excisional wounds were created in the skin of periostin-knockout and wild-type, sex-matched control mice. In wild-type mice, periostin was potently induced 5-7 days after wounding. In the absence of periostin, day 7 wounds showed a significant reduction in myofibroblasts, as visualized by expression of α-smooth muscle actin (α-SMA) within the granulation tissue. Delivery of recombinant human periostin by electrospun collagen scaffolds restored α-SMA expression. Isolated wild-type and knockout dermal fibroblasts did not differ in in vitro assays of adhesion or migration; however, in 3D culture, periostin-knockout fibroblasts showed a significantly reduced ability to contract a collagen matrix, and adopted a dendritic phenotype. Recombinant periostin restored the defects in cell morphology and matrix contraction displayed by periostin-deficient fibroblasts in a manner that was sensitive to a neutralizing anti-β1-integrin and to the FAK and Src inhibitor PP2. We propose that periostin promotes wound contraction by facilitating myofibroblast differentiation and contraction.

Amnion-derived cellular cytokine solution promotes macrophage activity

Activated macrophages play a significant role in wound healing and infected tissue repair. In this study, we investigate the recruitment of macrophages into the wound, and the effects on the bactericidal/phagocyte activity after exposure to amnion-derived cellular cytokine solution (ACCS). To evaluate the influence of ACCS on the migratory behavior of macrophages, cell migration was assayed quantitatively using a Boyden chamber. Chemotactic migration activity of macrophages through the membrane determined the influence of ACCS. In the presence of ACCS, macrophages demonstrated a statistically significant (P < 0.05) increase in migration as compared with controls. Subsequently, groups of macrophages were exposed to different concentrations of ACCS solution. The killing and phagocytic activity of each group was compared with the control after exposure to Escherichia coli. Macrophage activity following activation by higher concentrations of ACCS demonstrated significantly increased phagocytosis as well as a trend correlation between percentage ACCS concentration and bactericidal activity. These cell types, critical to normal wound healing, may be influenced by ACCS to accelerate migration and enhance bactericidal/phagocytic activity in wounds.

Rapid screening, in vitro study of metal oxide and polymer hybrids as delivery coatings for improved soft-tissue integration of implants

Metal-organic chemistry allows for molecular mixing and creation of a range of submicron phase-separated structures from normally brittle metal oxides and flexible polymers with improved bioactivity and delivery properties. In this study, we used a high throughput platform to investigate the influence of organic metal oxide doping of polydimethylsiloxane (PDMS) coatings on cellular bioactivity and controlled release of vanadium compared with titanium oxide coatings without additional PDMS. Metal-organic-derived titanium and or vanadium was doped into PDMS and used to form a coating on the bottom of cell culture microplates in the absence of added water, acids, or bases. These hybrid coatings were rapidly screened to establish how titanium and vanadium concentration influences cell proliferation, adhesion, and morphology. We demonstrate that titanium doping of PDMS can be used to improve cell proliferation and adhesion, and that vanadium doping caused a biphasic dose response in proliferation. A 28-day vanadium and titanium elution study indicated that titanium was not released, but the presence of PDMS in coatings increased delivery rates of vanadium compared with titania coatings without polymer. Hybrid coatings of titanium-doped polymers have potential for improving wound healing dynamics, soft-tissue integration of medical implants, and use as controlled delivery vehicles.

The cellular biology of flexor tendon adhesion formation: an old problem in a new paradigm

Intrasynovial flexor tendon injuries of the hand can frequently be complicated by tendon adhesions to the surrounding sheath, limiting finger function. We have developed a new tendon injury model in the mouse to investigate the three-dimensional cellular biology of intrasynovial flexor tendon healing and adhesion formation. We investigated the cell biology using markers for inflammation, proliferation, collagen synthesis, apoptosis, and vascularization/myofibroblasts. Quantitative immunohistochemical image analysis and three-dimensional reconstruction with cell mapping was performed on labeled serial sections. Flexor tendon adhesions were also assessed 21 days after wounding using transmission electron microscopy to examine the cell phenotypes in the wound. When the tendon has been immobilized, the mouse can form tendon adhesions in the flexor tendon sheath. The cell biology of tendon healing follows the classic wound healing response of inflammation, proliferation, synthesis, and apoptosis, but the greater activity occurs in the surrounding tissue. Cells that have multiple "fibripositors" and cells with cytoplasmic protrusions that contain multiple large and small diameter fibrils can be found in the wound during collagen synthesis. In conclusion, adhesion formation occurs due to scarring between two damaged surfaces. The mouse model for flexor tendon injury represents a new platform to study adhesion formation that is genetically tractable.

Aberrant wound-healing response in mitomycin C-treated leaking blebs: a histopathologic study

OBJECTIVE

To characterize histopathologic features of leaking mitomycin C-treated blebs and aberrant wound healing that may lead to persistent conjunctival thinning and leakage.

METHODS

Forty mitomycin C-treated filtering blebs excised for persistent leaks from 40 patients were examined histopathologically using hematoxylin-eosin, periodic acid-Schiff, Masson trichrome, and Alcian blue histochemical stains.

RESULTS

Ninety percent of the leaking blebs contained epithelial-stromal domes with areas of acellular stroma covered by attenuated epithelium. Seventy-five percent of the blebs demonstrated varying degrees of fibrovascular repair growing from the bleb margin, either beneath or interdigitating with the acellular zone. A novel observation in 65% of specimens was Alcian blue-positive myxoid stroma at the interface between the fibrovascular proliferation and the epithelial-stromal dome. The association between the presence of fibrovascular proliferation and Alcian blue-staining myxoid stroma was significant by Fisher exact test (P = .002).

CONCLUSIONS

A desirable filtration bleb requires a sufficient reparative fibrovascular response to maintain an epithelial-stromal barrier to prevent leakage. Fibroblasts must lay down a continuous collagen-rich fibrous layer, rather than merely myxoid stroma, beneath the conjunctival epithelium to promote bleb stability. Surgical techniques and postsurgical care should aim to attain this desired outcome.

Host immune factors regulating fibrosis

Mononuclear cells produce lymphokines and monokines, the function of which is to initiate the mobilization, proliferation and differentiation of additional mononuclear cells in an inflammatory site. In addition, these inflammatory cells produce biologically active mediators which modulate the functions of certain non-inflammatory cell targets. Lymphokines and monokines can stimulate chemotaxis, division, and matrix synthesis by connective tissue fibroblasts. Additional mononuclear cell-derived mediators can inhibit or suppress these fibroblast functions, implicating the host immune system in the regulation of connective tissue metabolism associated with an inflammatory response. Altering the balance of the production and/or release of these connective tissue-active agents could result in excess fibroblast growth and matrix synthesis (fibrosis) and its pathological manifestations.

Platelet-rich plasma enhances the initial mobilization of circulation-derived cells for tendon healing

Circulation-derived cells play a crucial role in the healing processes of tissue. In early phases of tendon healing processes, circulation-derived cells temporarily exist in the wounded area to initiate the healing process and decrease in number with time. We assumed that a delay of time-dependent decrease in circulation-derived cells could improve the healing of tendons. In this study, we injected platelet-rich plasma (PRP) containing various kinds of growth factors into the wounded area of the patellar tendon, and compared the effects on activation of circulation-derived cells and enhancement of tendon healing with a control group (no PRP injection). To follow the circulation-derived cells, we used a green fluorescent protein (GFP) chimeric rat expressing GFP in the circulating cells and bone marrow cells. In the PRP group, the numbers of GFP-positive cells and heat-shock protein (HSP47; collagen-specific molecular chaperone)-positive cells were significantly higher than in the control group at 3 and 7 days after injury. At the same time, the immunoreactivity for types I and III collagen was higher in the PRP group than in the control group at early phase of tendon healing. These findings suggest that locally injected PRP is useful as an activator of circulation-derived cells for enhancement of the initial tendon healing process.

Elastic fibers in myocardial scars in rats: development teraction with other components

This work was designed to determine the course of development of elastic fibers in myocardial scars in rats and their relationship to other components of such structures. Light and electron microscopic observations were made on tissues from 24 rats, killed at sequent stages from 4 to 24 days postinjury. By both techniques, elastic fibers, shown to be forming by 4 days, had increased in size and number with maturation of the scar. At later stages they became interdigitated with the stumps of viable myocytes. We also saw that these fibers often had formed close contacts with the cell surfaces of myofibroblasts and nonvascular smooth muscle cells; a process found in some other situations but not previously in myocardial scars. This information is relevant, in particular, to the dynamics of myocardial scars and thus to the maintenance of function in the injured heart, but also to elastic fiber behavior in general. The integral role of elastic fibers in cell-matrix interactions as well as their biomechanical function is emphasized.

Bone Marrow Stromal Cells Act as Feeder Cells for Tendon Fibroblasts through Soluble Factors

Feeder effects of bone marrow stromal cells (BMSCs) on tendon fibroblasts were investigated using a co-culture method for the application of ligament or tendon tissue engineering and cell therapy. BMSCs had significant effects on enhancing cell proliferation, the ability of cells to migrate, and cell adhesivity but little effect on the extracellular matrix (ECM) synthesis of tendon fibroblasts without cell-cell contact. Furthermore, the conditioned medium from BMSCs, despite the existence of fibroblasts, significantly increased the number of fibroblasts. Based on these results, the mechanism of the feeder effects is considered to be a certain signal of soluble factors from BMSCs to the fibroblasts. Comparative proteome analysis of the conditioned medium from co-culture of fibroblasts and BMSCs revealed less expression of plasminogen, which showed inhibitory effects on fibroblast proliferation. With regard to the relationships between plasminogen and BMSCs in the co-culture system, we speculate that BMSCs allow resolution of plasminogen or its cleavage activity in the medium via some mechanism.

Dermal fibroblast-associated gene induction by asiaticoside shown in vitro by DNA microarray analysis

BACKGROUND

Asiaticoside, isolated from Centella asiatica, promotes fibroblast proliferation and extracellular matrix (ECM) synthesis in wound healing. The precise mechanism, however, in molecular and gene expression levels is still unclear.

OBJECTIVE

Using cDNA microarray technology, the alteration of gene expression profiles was determined for human dermal fibroblasts in vitro in the presence of asiaticoside (30 microg mL(-1)). Fifty-four genes, with known functions for cell proliferation, cell cycle progression and synthesis of ECM, were significantly upregulated in our 'genome-nest' expression profile at various time points. Furthermore, the mRNA levels and protein production of certain genes responsible for ECM synthesis (e.g. encoding type I and type III collagen proteins) were evaluated by Northern blot and radioimmunoassay, respectively.

RESULTS

We found that there is a close correlation between the gene profile, mRNA and protein production in the response of the cells to asiaticoside stimulation.

CONCLUSIONS

This information could be used for exploring the response of the target genes to asiaticoside in fibroblasts.

Platelet-derived growth factor gene delivery stimulates ex vivo gingival repair

Destruction of tooth support due to the chronic inflammatory disease periodontitis is a major cause of tooth loss. There are limitations with available treatment options to tissue engineer soft tissue periodontal defects. The exogenous application of growth factors (GFs) such as platelet-derived growth factor (PDGF) has shown promise to enhance oral and periodontal tissue regeneration. However, the topical administration of GFs has not led to clinically significant improvements in tissue regeneration because of problems in maintaining therapeutic protein levels at the defect site. The utilization of PDGF gene transfer may circumvent many of the limitations with protein delivery to soft tissue wounds. The objective of this study was to test the effect of PDGF-A and PDGF-B gene transfer to human gingival fibroblasts (HGFs) on ex vivo repair in three-dimensional collagen lattices. HGFs were transduced with adenovirus encoding PDGF-A and PDGF-B genes. Defect fill of bilayer collagen gels was measured by image analysis of cell repopulation into the gingival defects. The modulation of gene expression at the defect site and periphery was measured by RT-PCR during a 10-day time course after gene delivery. The results demonstrated that PDGF-B gene transfer stimulated potent (>4-fold) increases in cell repopulation and defect fill above that of PDGF-A and corresponding controls. PDGF-A and PDGF-B gene expression was maintained for at least 10 days. PDGF gene transfer upregulated the expression of phosphatidylinosital 3-kinase and integrin alpha5 subunit at 5 days after adenovirus transduction. These results suggest that PDGF gene transfer has potential for periodontal soft tissue-engineering applications.

Meningeal cell-derived semaphorin 3A inhibits neurite outgrowth

The neural scar that forms after injury to the mammalian central nervous system is a barrier to sprouting and regenerating axons. In addition to reactive astrocytes that are present throughout the lesion site, leptomeningeal fibroblasts invade the lesion core. When isolated in vitro, these cells form a very poor substrate for growing neurites, even more so than reactive astrocytes. Nevertheless the molecular mechanisms involved in this growth inhibition are not well understood. Semaphorins have been reported to be upregulated in meningeal cells (MCs) on mechanical injury to the brain and spinal cord. In the present study, we show that Sema3A mRNA and active protein are produced by cultured meningeal cells. A protein extract from these cells induces the collapse of embryonic dorsal root ganglion (DRG) growth cones. This collapsing activity is partially blocked by neuropilin-1 antibodies and is absent in meningeal cells derived from Sema3A-knockout mice. In addition to growth cone collapse, recombinant Sema3A but not Sema3C inhibits neurite outgrowth of embryonic DRGs. Consistent with this result we find that the inhibitory effect of meningeal cells on neurite outgrowth is partially overcome on Sema3A-deficient MCs. Furthermore we show that the inhibitory effect of MC-derived Sema3A on neurite outgrowth is modulated by nerve growth factor. Our results show that Sema3A, a chemorepellent during nervous system development, is a major neurite growth-inhibitory molecule in meningeal fibroblasts and is therefore likely to contribute to the inhibitory properties of the neural scar.

Evaluation of the effect of ascorbic acid treatment on wound healing in mice exposed to different doses of fractionated gamma radiation

Alteration of the radiation-induced changes in wound contraction, collagen synthesis and wound histology by ascorbic acid was studied in mice exposed to 10, 16 and 20 Gy of fractionated (2 Gy/fraction) gamma radiation. The animals were given double-distilled water or ascorbic acid daily before exposure to 2 Gy/day of fractionated irradiation. A full-thickness skin wound was created on the dorsum of the irradiated mice, and the progression of wound contraction and collagen synthesis were examined and histological evaluations were carried out at various times after wounding. Irradiation caused a dose-dependent delay in wound contraction, and pretreatment with ascorbic acid resulted in a significant increase in wound contraction. The greatest increase in wound contraction was observed 6 and 9 days after wounding in both groups. Pretreatment with ascorbic acid augmented the synthesis of collagen significantly as revealed by an increase in hydroxyproline content. The collagen deposition and fibroblast and vasculature densities declined in a dose-dependent manner in groups receiving radiation alone as indicated by histological evaluation. Pretreatment with ascorbic acid ameliorated the observed effect significantly. These studies demonstrate that pretreatment with ascorbic acid resulted in a significant reduction of radiation-induced delay in wound healing as shown by earlier wound closure and increased collagen content and fibroblast and vascular densities.

Fate of donor bone marrow cells in medial collateral ligament after simulated autologous transplantation

A potential strategy to enhance ligament healing by transplantation of mesenchymal stem cells (MSCs), which are demonstrated to differentiate into fibroblast-like cells in vitro, is presented. The objective of this study was to follow transplanted nucleated cells from bone marrow, which contain MSCs, in the healing medial collateral ligament (MCL) over time, and to examine their phenotype and survivability. It was hypothesized that MSCs in nucleated cells from bone marrow would differentiate into fibroblast-like cells in the healing ligament following adaptation to the environment. The transplantation model employed in this study eliminates the immune response to a donor by the recipient using a transgenic rat (donor), which does not produce foreign protein from transgenes, and its wild-type rat (recipient) in order to simulate autologous transplantation. The MCL of the wild-type rat was ruptured, where 1 x 10(6) nucleated cells of bone marrow from the transgenic rat were injected. The transgenes in transplanted nucleated cells were detected throughout the healing MCL for 28 days by in situ hybridization. At 3 days, many donor cells were evident in the injury site and fascial pocket, and some were found in the midsubstance. Morphologically, transplanted cells with elongated nuclei were found at the ruptured edge of the midsubstance and surface of the unruptured site after 3 days. At 28 days, these cells continued to survive in the healing MCL. Their shapes were similar to those of surrounding recipient MCL fibroblasts. Thus, transplanted cells might differentiate into fibroblasts. Therefore, it was demonstrated that there is a potential for nucleated cells from bone marrow to serve as a vehicle for therapeutic molecules as well as to be a source in enhancing healing of ligaments.

Wound healing response in the presence of stromal irregularities after excimer laser treatment

PURPOSE

To trace the fate of stromal irregularities after excimer laser treatment and to increase our knowledge of the reasons why surface irregularities in the ablation bed cause inferior postoperative results.

METHODS

Twelve New Zealand White rabbits received a transepithelial photoablation to a preset depth of 60 microm. An electron microscopy specimen grid was then placed on the denuded stroma and another 20 microm ablation was applied in order to produce surface irregularities. Another six rabbits received a plano transepithelial photoablation to a preset depth of 80 microm. The treated corneas were harvested at various timepoints and differentially further processed for microradiography, hematoxylin-eosin -, hyaluronan (HA)- and leukocyte protein L1 staining.

RESULTS

In the grid treated corneas the subepithelial mesh pattern is clearly discernible after 1 week, and after 4 weeks it is replaced by a subepithelial layer containing HA and water. The thinning of this layer between 1 and 12 weeks is statistically significant (p<0.05). After 4 and 8 week the plano treated corneas only exhibit some subepithelial HA- and water accumulation. After 1 day the grid treated corneas show an extensive stromal infiltration of leukocytes. In the plano treated corneas the leukocytes mainly remain on the surface.

CONCLUSIONS

During the healing process stromal irregularities are flattened, leaving a homogeneous zone with increased water content. This subepithelial layer is rarefying as new subepithelial tissue is forming. Postablational irregularities induce a more pronounced healing reaction when compared to a smooth ablation surface. Leukocyte infiltration seems to play a role in this process.

Vascular alterations in the rabbit patellar tendon after surgical incision

Open incision of the patellar tendon (PT) is thought to promote acute vascular responses which ultimately result in an enhanced degree of tendon repair. Such a clinical procedure is commonly applied to patients with refractory tendinitis. The objective of this study was to quantify the vascular adaptations (both anatomical and physiological) to longitudinal incision of the PT, and the resultant effects on tendon organisation. Fifty-four New Zealand White rabbits were separated into 3 experimental groups and 2 control groups. Experimental groups underwent surgical incision of the right PT, and were assessed 3 d, 10 d and 42 d following injury; normal unoperated controls were evaluated at time zero, and sham-operated controls were evaluated at 3 d to control for the effects of incising the overlying skin. Quantitative measures of PT blood supply (blood flow, microvascular volume) and geometric properties of PT substance were obtained for each PT. Histomorphology was assessed to evaluate vascular remodelling and matrix organisation in the healing PT. Longitudinal open incision surgery of the PT led to rapid increases in both blood flow and vascular volume. The incision of overlying tissues alone (sham-operated) contributed to this measurable increase, and accounted for 36% and 42% of the elevated blood flow and vascular volume respectively at the 3 d interval. In the incised PT, blood flow significantly increased by 3 d compared with both time zero and sham-operated controls, and remained significantly elevated at the 10 d interval. Similarly, vascular volume of the incised PT increased at 3 d compared both with time zero and sham-operated controls. At the 10 d interval, the increase in vascular volume was greatest in the central PT substance. By 42 d both blood flow and vascular volume of the incised tendon had diminished, with only blood flow remaining significantly different from controls. In the contralateral limb, a significant neurogenically mediated vasodilation was measured in the contralateral PTs at both early time intervals, but was not seen by the later 42 d interval. With respect to PT geometric properties in the experimental animals, a larger PT results as the tendon matrix and blood vessels remodel. PT cross-sectional area increased rapidly by 3 d to 1.3 times control values, and remained significantly elevated at 42 d postinjury. Morphological assessments demonstrated the disruption of matrix organisation by vascular and soft tissue components associated with the longitudinal incisions. Substantial changes in matrix organisation persisted at 42 d after surgery. These findings suggest that open longitudinal incision of the PT increases the vascular supply to deep tendon early after injury. These changes probably arise through both vasomotor and angiogenic activity in the tissue. Since PT blood flow and vascular volume return towards control levels after 6 wk but structural features remain disorganised, we propose that vascular remodelling is more rapid and complete than matrix remodelling after surgical incision of the PT.

The effect of cytokines on the migration of fibroblasts derived from different regions of the canine shoulder capsule

This study examined the effect of several cytokines on the chemotactic migration of fibroblasts derived from 3 different parts of the canine shoulder: the upper part of the medial glenohumeral ligament (equivalent to the anterior part of the inferior glenohumeral ligament of the human shoulder); the inferior part of the medial glenohumeral ligament (equivalent to the axillary pouch of the human shoulder); and the posterior capsule (equivalent to the thin posterior capsule in the human shoulder). Platelet-derived growth factor-AB stimulated the migration of all 3 cell types in a dose-dependent manner, with increases from 150% to 300% at 1 ng/mL to 500% to 700% at 10 ng/mL. Hepatocyte growth factor also stimulated the migration of all 3 cell types in a dose-dependent manner (130% to 310%). Insulinlike growth factor-1 increased the migration of all 3 types of fibroblasts by 160% to 250%. Bone morphogenic protein-2, interleukin-1, and transforming growth factor-b had no significant effect on migration of shoulder capsular fibroblasts. These data demonstrate that capsular fibroblasts are responsive to specific growth factors and suggest the potential for use of growth factors to augment healing and/or remodeling of the shoulder capsule.

The effects of early mobilization in the healing of achilles tendon repair

Twenty-four male New Zealand rabbits underwent suture repair of a tenotomy of the left achilles tendon. The rabbits were randomized into two groups of 12 animals; in group (A), the ankle was immobilized by pinning for 35 days, while in the group (B), the ankle was immobilized for only 14 days followed by active mobilization. Following sacrifice at 35 days postoperatively, the retrieved tendons were evaluated by biomechanical testing and histologic examination. Approximately 50% of stretching occurred in the first four days; average overall elongation was 9.5+/-1.0 mm and 12.7+/-1.5 mm (p=0.102) and average stiffness recovery was 67.4+/- 2.0% and 82.9 +/- 1.9% (p=0.0004) for groups A and B respectively. Histologically both groups demonstrated traces of disorganized neo-collagen fibers at the repair site as early as the fourth day with subsequent appearance of more mature collagen. The results obtained from our study favor early mobilization of the repaired tendon, which seems to restore the functional properties of the tendons more rapidly than continuous immobilization of an identical surgical repair.

Electrothermally-assisted capsulorrhaphy (ETAC): a new surgical method for glenohumeral instability and its rehabilitation considerations

Knowledge of current surgical procedures and the effect they have on healing tissue is important when developing rehabilitation guidelines. Recently, clinicians have been asked to treat patients who have undergone Electrothermally-Assisted Capsulorrhaphy (ETAC) for shoulder instability. The ultimate tensile strength of the tightened capsule is unknown during various timeframes following surgery. The use of thermal energy to shrink the shoulder joint capsule initially causes weakness of the collagen ultrastructure. Rehabilitation following ETAC includes a period of relative immobilization, followed by controlled range of motion exercises. Exercises to strengthen shoulder muscles must be done in a manner that minimizes stress on the surgically treated capsule. This article provides a brief review of capsuloligamentous repair; describes the surgical procedure, its indications, contraindications, and the effect ETAC has on the healing tissue; and provides guidelines for rehabilitation following ETAC based on the evidence available and the authors clinical experience.

Compressive compared with tensile loading of medial collateral ligament scar in vitro uniquely influences mRNA levels for aggrecan, collagen type II, and collagenase

To test the hypothesis that loading conditions can be used to engineer early ligament scar behaviors, we used an in vitro system to examine the effect that cyclic hydrostatic compression and cyclic tension applied to 6-week rabbit medial collateral ligament scars had on mRNA levels for matrix molecules, collagenase, and the proto-oncogenes c-fos and c-jun. Our specific hypothesis was that tensile stress would promote more normal mRNA expression in ligament whereas compression would lead to higher levels of mRNA for cartilage-like molecules. Femur (injured medial collateral ligament)-tibia complexes were subjected to a hydrostatic pressure of 1 MPa or a tensile stress of 1 MPa of 0.5 Hz for 1 minute followed by 14 minutes of rest. On the basis of a preliminary optimization experiment, this 15-minute testing cycle was repeated for 4 hours. Semiquantitative reverse transcription-polymerase chain reaction analysis was performed for mechanically treated medial collateral ligament scars with use of rabbit specific primer sets for types I, II, and III collagen, decorin, biglycan, fibromodulin, versican, aggrecan, collagenase, c-fos, c-jun, and a housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase. Cyclic hydrostatic compression resulted in a statistically significant increase in mRNA levels of type-II collagen (171% of nonloaded values) and aggrecan (313% of nonloaded values) but statistically significant decreases in collagenase mRNA levels (35% of nonloaded values). Cyclic tension also resulted in a statistically significant decrease in collagenase mRNA levels (66% of nonloaded values) and an increase in aggrecan mRNA levels (458% of nonloaded values) but no significant change in the mRNA levels for the other molecules. The results show that it is possible to alter mRNA levels for a subset of genes in scar tissue by supplying unique mechanical stimuli in vitro and thus that further investigation of scar engineering for potential reimplantation appears feasible.

Porcine anterior cruciate ligament fibroblasts are similar to cells derived from the ligamentum teres, another non-healing intra-articular ligament

Porcine ligament fibroblasts were cultured from the anterior cruciate (ACL), medial collateral (MCL), and ligamentum teres (LT). There were no apparent differences in confluent cellular morphology among the ligament cell types as evaluated by phase contrast microscopy. The proliferation rate of MCL cells from 24-120 h was significantly higher (p < 0.05) than that of cells from either the LT or the ACL. MCL cells produced more collagen and less non-collagenous protein than the LT and ACL as determined by [3H]proline incorporation. This resulted in MCL cells producing a higher percentage (37%, p < 0.05) of collagen relative to total protein than either the ACL (28%) or the LT (32%). The MCL cells produced a significantly higher percentage (34.7%, p < 0.05) of type-III collagen relative to total type-I and III collagen than either the ACL (29.2%) or the LT (29.5%). The LT and MCL cells had similar and significantly greater coverage of in vitro wounds than the ACL. This study provides the first in vitro study of the LT and demonstrates that fibroblasts from the LT and ACL, two ligaments that heal poorly, have similar in vitro characteristics, with the exception of wound healing.

Immuno-inflammatory cell dynamics during cutaneous wound healing

The process of wound healing begins with an inflammatory reaction that is principally dependent on cellular immune elements. Although the involvement in wound healing of leucocytes that mediate nonspecific immunity (e.g. neutrophils and macrophages) is well known, the participation of cells which prime the immune reaction, i.e. the lymphocytes, requires further investigation. This study was performed to examine the temporal sequence and kinetics of these cells during cutaneous wound repair. The model selected was a full-thickness skin excisional wound made on the flanks of female Wistar rats. At time points ranging from 3 h to 2 wk wound samples were processed for polyester wax-embedding. Target antigens were identified and monitored quantitatively in sections stained immunohistochemically. Monoclonal antibodies against neutrophils, macrophages, pan T cells and cytotoxic populations of lymphocytes were used. The results showed that these cells are involved in the process of wound healing in a distinctive dynamic pattern. The accumulation of CD3+ T lymphocytes in the wound bed was mainly associated with the phase of granulation tissue formation. Intraepithelial CD3+ T lymphocytes were detected in considerable numbers within the regenerating epidermis. The cytotoxic cell populations (OX8+) were classified morphologically into the cytotoxic/suppressor subset of T cells and NK cells. The OX8+ T cells were shown to have a kinetic pattern similar to CD3+ T lymphocytes but of a lower magnitude. The accumulation of OX8+ NK cells was confined to the early inflammatory phase of repair. It is concluded that CD3+ T lymphocytes as well as OX8+ cytotoxic populations of the immune system are involved in the process of cutaneous wound healing in temporal sequences which suggest that they may be involved in its modulation.

Dynamics of wound healing after silicone device implantation

A large surgical wound is required for implantation of silicone mammary devices. Formation of capsules around silicone devices follows wound healing processes except that the healing is conformed and significantly delayed by the physical presence of the implant. Multilayered capsules are thicker and lymphocytic and plasmalymphocytic vasculitis, markers for delayed hypersensitivity, also correlate with thicker capsules. Polyurethane-coated devices induce very thick capsules that remain so for over 20 years. By contrast, gel and saline content devices show maximum thickness at 6. 5 years. Active T(H) lymphocyte memory does not differ by implant type for individuals with devices in place and that for gel content devices peaks at 10.5 years. There was a significant decrease in T cell indexes only after the removal of saline content devices. Comparison of the rate of formation of the periprosthetic capsule with the healing time of large wounds of similar size indicates that silicone devices interfere with the healing process, requiring substantially more time. This extended period has the potential for enhancing autoimmune conversion as a consequence of persistent delayed hypersensitivity.

Open versus closed repair of the Achilles tendon: an experimental animal study

This experimental animal study compared the healing patterns between open and closed treatments of Achilles tendon tenotomies. Twenty-four male New Zealand rabbits underwent tenotomy of the left Achilles tendon and were randomized into two groups, treated with either open surgical repair or closed management. After the death of the animal, the retrieved tendons were submitted for biomechanical and histological testing. The total elongation of the open treatment group was 9.5+/-1.0 mm compared with 21.2+/-3.4 mm for the closed treatment group (P = 0.008), and the regain of stiffness was 67.4+/-2.0% and 48.9+/-5.3%, respectively (P = 0.132). Histological evaluation demonstrated similar healing patterns in both groups.

Expression of the gene encoding the chemorepellent semaphorin III is induced in the fibroblast component of neural scar tissue formed following injuries of adult but not neonatal CNS

This study evaluates the expression of the chemorepellent semaphorin III (D)/collapsin-1 (sema III) following lesions to the rat CNS. Scar tissue, formed after penetrating injuries to the lateral olfactory tract (LOT), cortex, perforant pathway, and spinal cord, contained numerous spindle-shaped cells expressing high levels of sema III mRNA. The properties of these cells were investigated in detail in the lesioned LOT. Most sema III mRNA-positive cells were located in the core of the scar and expressed proteins characteristic for fibroblast-like cells. Neuropilin-1, a sema III receptor, was expressed in injured neurons with projections to the lesion site, in a subpopulation of scar-associated cells and in blood vessels around the scar. In contrast to lesions made in the mature CNS, LOT transection in neonates did not induce sema III mRNA expression within cells in the lesion and was followed by vigorous axonal regeneration. The concomitant expression of sema III and its receptor neuropilin-1 in the scar suggests that sema III/neuropilin-1-mediated mechanisms are involved in CNS scar formation. The expression of the secreted chemorepellent sema III following CNS injury provides the first evidence that chemorepulsive semaphorins may contribute to the inhibitory effects exerted by scars on the outgrowth of injured CNS neurites. The vigorous regrowth of injured axons in the absence of sema III following early neonatal lesions is consistent with this notion. The inactivation of sema III in scar tissue by either antibody perturbation or by genetic or pharmacological intervention could be a powerful means to promote long-distance regeneration in the adult CNS.