Evaluation of fibrin sealants in cutaneous wound closure

Influence of sealant fibrin on the wound healing of the pigs vocal folds

Fibrin sealants or fibrin glue are products made from human plasma proteins, which mimic the final pathway of the coagulation cascade. Its application to stimulate the healing process has been a topic of debate in the literature. The use of fibrin sealants in phonosurgery has been empirical; there have been no studies that investigate the action of fibrin sealant in Reinke's space.

Aim

To evaluate the effect of fibrin glue in healing of the vocal folds of pigs after surgical manipulation.

Materials and Methods

This was a prospective and experimental study. Six animals had both vocal folds incised. Sealant was applied in one of them; the other served as a control. After three months, the animals were sacrificed and a collagen count was carried out.

Results

The side on which glue was applied had an average of 27.8% against 20.4% of the side without glue.

Conclusion

The collagen concentration in the samples where the fibrin sealant was applied was significantly higher compared to samples without glue. Thus, the presence of a fibrin sealant stimulates fibrogenesis in this tissue.

Effects of PerClot® on the healing of full-thickness skin wounds in rats

PerClot(®) is a hemostatic material made of polysaccharide from modified starch and has been shown to assist in topical hemostasis. The principal goal in treating surgical and non-surgical wounds is the need for rapid closure of the lesion. This study investigated whether topical application of PerClot(®) could improve impaired wound healing in Sprague-Dawley (SD) rats. Full-thickness skin wounds were created on the back of the rats. Immediately, PerClot(®) was introduced into the wound bed, while wounds receiving starch or nothing served as controls. Wound closure was monitored using well-recognized wound-healing parameters: histological examination for inflammatory cells and fibroblast infiltration, newly formed capillaries, and collagen deposition. Meanwhile, transforming growth factor (TGF-β1) was measured by immunochemistry. Wound closure was significantly accelerated by local application of PerClot(®). Furthermore, PerClot(®)-treated wounds showed significantly increased fibroblast numbers at 5 days post-wounding, and newly formed capillaries at 7 days post-wounding, and collagen regeneration at 7 and 14 days post-wounding. The number of infiltrating fibroblasts expressing TGF-β1 was significantly higher than that in the controls at 7 and 14 days post-wounding. PerClot(®) can improve the wound healing and this effect might involve an increase in the activity of fibroblasts and increased release of TGF-β1.

Coalescence of extracellular matrix (ECM) from porcine urinary bladder (UBM) with a laser-activated chitosan-based surgical adhesive

Urinary bladder matrix (UBM) has been extensively investigated as a naturally occurring biomaterial in therapeutic applications for tissue repair or regeneration, while other strategies involve biopolymers such as chitosan for tissue reconstruction. The coalescence of UBM with chitosan has considerable potential in enhancing tissue reconstruction. Characterisation of a novel, laser-activated, chitosan-based, thin-film surgical adhesive with UBM in various morphologies showed that the films had increased surface rugosities and crystallinities (Ra approx. 0.83 um, approx. 12% crystallinity) when compared to the chitosan adhesive alone (R a = 0.74 um, 7% crystallinity). Tensile strength of the films was significantly increased by the addition of UBM in particulate form (12.1-32.4 MPa). Furthermore, tissue adhesion strengths using these hybrid biomaterials were maintained at approx. 15 kPa compared to 3 kPa for fibrin glue. Histological analysis demonstrated that laser irradiation of the UBM-chitosan adhesive biomaterial caused no thermal damage to tissue. Examination of the cellular response at the material interface showed that 3T3 fibroblasts maintained their regular morphology with enhanced growth compared to films of both chitosan and its adhesive form. These results suggest that coalescence of UBM with a chitosan-based adhesive supports the development of biomaterial devices for sutureless wound closure that could enhance tissue repair and reconstruction.

The healing of full-thickness burns treated by using plasmid DNA encoding VEGF-165 activated collagen-chitosan dermal equivalents

Repair of deep burn by use of the dermal equivalent relies strongly on the angiogenesis and thereby the regeneration of dermis. To enhance the dermal regeneration, in this study plasmid DNA encoding vascular endothelial growth factor-165 (VEGF-165)/N,N,N-trimethyl chitosan chloride (TMC) complexes were loaded into a bilayer porous collagen-chitosan/silicone membrane dermal equivalents (BDEs), which were applied for treatment of full-thickness burn wounds. The DNA released from the collagen-chitosan scaffold could remain its supercoiled structure but its degree was decayed along with the prolongation of incubation time. The released DNA could transfect HEK293 cells in vitro with decayed efficiency too. Human umbilical vein endothelial cells (HUVECs) in vitro cultured in the scaffold loaded with TMC/pDNA-VEGF complexes expressed a significantly higher level of VEGF and showed higher viability than those cultured in the controls, i.e. blank scaffold, and scaffolds loaded with naked pDNA-VEGF and TMC/pDNA-eGFP, respectively. The four different BDEs were then transplanted in porcine full-thickness burn wounds. Results showed that the TMC/pDNA-VEGF group had a significantly higher number of newly-formed and mature blood vessels, and fastest regeneration of the dermis. RT-qPCR and western blotting found that the experimental group also had the highest expression of VEGF, CD31 and α-SMA in both mRNA and protein levels. Furthermore, ultra-thin skin grafting was performed on the regenerated dermis 14 days later, leading to complete repair of the burn wounds with normal histology. Moreover, the tensile strength of the repaired tissue increased along with the time prolongation of post grafting, resulting in a value of approximately 70% of the normal skin at 105 days.

Cell Compatibility of Fibrin Sealants: In Vitro Study with Cells Involved in Soft Tissue Repair

Fibrin sealants can be used to support tissue regeneration or as vehicles for delivery of cells in tissue engineering. Differences in the composition of fibrin sealants, however, could determine the success of such applications. The results presented in this article show clear differences between Fibrin sealant A (FS A) clots and Fibrin sealant B (FS B) clots with respect to their compatibility with primary human cells involved in soft tissue repair. FS A clots, which are characterized by a physiological coarse fibrin structure, promoted attachment, spreading, and proliferation of keratinocytes, fibroblasts, and endothelial cells. In contrast, FS B clots displaying a fine to medium clot structure failed to support spreading of all three cell types. Adhesion of keratinocytes was decreased on FS B clots compared to FS A clots after 3 h incubation, whereas number of attached fibroblasts and endothelial cells was initially comparable between the two fibrin sealants. However, all three cell types proliferated on FS A clots but no sustained proliferation was detected on FS B clots. We further demonstrate that the observed differences between FS A and B clots are partly based upon 1 M sodium chloride extractable constituents, like thrombin, and partly on nonextractable constituents or the fibrin structure. In conclusion, our in vitro results demonstrate that FS A clots serve as a provisional matrix that encourages adhesion and growth of keratinocytes, fibroblasts, and endothelial cells. Therefore, FS A seems to be well suited for applications in tissue engineering.

Enhanced angiogenesis of gene-activated dermal equivalent for treatment of full thickness incisional wounds in a porcine model

Angiogenesis of dermal equivalent is one of the key issues for treatment of full thickness skin defects. To develop a gene-activated bilayer dermal equivalent (BDE), N,N,N-trimethyl chitosan chloride (TMC), a cationic gene delivery vector, was used to form complexes with the plasmid DNA encoding vascular endothelial growth factor-165 (VEGF-165), which was then incorporated into a collagen-chitosan/silicone membrane scaffold. To evaluate the angiogenesis property in vivo, full thickness skin defects were made on the back of pigs, into which the TMC/pDNA-VEGF complexes loaded BDE and other three control BDEs, i.e. the blank BDE, and the BDEs loaded with pDNA-VEGF and TMC/pDNA-eGFP complexes, respectively, were transplanted. Biopsy specimens were harvested at day 7, 10 and 14 after surgery for histology, immunohistochemistry, immunofluorescence, real-time quantitative PCR (RT-qPCR) and western blotting analyses. The results showed that the TMC/pDNA-VEGF group had the strongest VEGF expression in mRNA and protein levels, resulting in the highest densities of newly-formed and mature vessels. The ultra-thin skin graft was further transplanted onto the dermis regenerated by the TMC/pDNA-VEGF complexes loaded BDE at day 10 and well survived. At 112 days grafting, the healing skin had a similar structure and approximately 80% tensile strength of the normal skin.

Enhancement of incisional wound healing by thrombin conjugated iron oxide nanoparticles

Thrombin has been clinically used for topical hemostasis and wound management for more than six decades. The half-life of thrombin in human plasma is shorter than 15s due to close control by inhibitors. In order to stabilize the thrombin, it was bound to maghemite (gamma-Fe(2)O(3)) nanoparticles, as demonstrated in previous work. The aim of the present study was to examine the efficiency of the bound thrombin for wound healing applications compared to the free thrombin. For this purpose incisional wounds on rat skin were treated with a mixture of fibrinogen, CaCl(2) solution and free or bound thrombin. The wounds' edges were then approximated by skin staples. The control incisional wounds were closed with staples only. In the course of 28 days of healing the highest values of skin tensile strength were observed following treatment with the bound thrombin. Significantly lower values of tensile strength were observed following treatment with the free thrombin, and the lowest values were obtained following treatment with staples only. The histological findings correlate with the mechanical strength measurements, which demonstrate the most advanced stages of healing following treatment with the bound thrombin.

Differences in cutaneous wound healing between dogs and cats

Regardless of the species involved, wound healing follows a predictable course of overlapping phases. In spite of these commonalities, significant species differences in cutaneous wound healing have been uncovered in the Equidae and, more recently, between the dog and cat. It has also recently been shown that the subcutaneous tissues play an important supporting role in cutaneous wound healing, which may help to ex-plain healing differences between cats and dogs. These discoveries may improve veterinarians' understanding of problem wound healing in the cat and, hopefully, lead to better strategies for wound management in this sometimes troublesome species.

Fibrin sealant as a treatment for canine aural haematoma: a case history

Aural haematomas occur commonly in dogs in which predisposing factors include trauma to the pinna, a history of violent head shaking, and acute or chronic otitis externa. Treatment usually involves invasive surgery performed under general anaesthesia but these techniques can create wounds requiring intensive aftercare. Furthermore, certain breeds of dog and/or older animals are often at greater risk due to complications arising from the use of anaesthetics. Therefore, a need exists for a less invasive procedure which can be performed easily in general practice and with minimal reliance on anaesthetics. Fibrin sealants fulfil these criteria and have been used successfully to treat aural haematomas in humans. This is the first known report on the use of fibrin sealant to treat a canine aural haematoma. In the present case, the haematoma recurred shortly after removal of the protective collar, and was subsequently treated by conventional surgery. Possible reasons for initial success of the fibrin sealant and then later recurrence of the haematoma (e.g. premature removal of the collar) are discussed.

Effect of radiation and cell implantation on wound healing in a rat model

BACKGROUND AND OBJECTIVES

Having shown that intra-dermal injection of fibroblasts decreases the effect of radiation on healing of superficial wounds, we now test the effect of fibroblasts and syngeneic marrow stromal cells on irradiated deep and superficial wounds.

METHODS

Wistar rats received bilateral buttock irradiation followed by partial excision of the gluteus muscle bilaterally. In Protocol 1, one irradiated wound was treated with 1.2 x 10(7) autologous cells injected intra-dermally. In Protocol 2, the experimental side was treated with a fibrin and autologous cell implant (1.2 x 10(7) cells). Twenty-one days later, wound mechanical characteristics were tested. In Protocol 3, the effect of pooled marrow stromal cells on healing of superficial irradiated wounds in Lewis rats was similarly tested.

RESULTS

The fibrin-fibroblast implant (Protocol 2) had no effect on wound mechanics. Superficial injection of fibroblasts (Protocol 1) significantly improved wound breaking strength when compared to the control group (mean +/- SEM, breaking strength: treated 504.6 +/- 37.0 g vs. control 353.4 +/- 35.2 g, P = 0.005). The dermal injection of marrow stromal cells also resulted in marked increases in breaking strength (mean +/- SEM, breaking strength: treated 338.5 +/- 39.9 g vs. control 187.1 +/- 12.0 g, P < 0.01). In both Protocols 1 and 3, ultimate tensile strength and toughness were increased in the side receiving cell transplantation.

CONCLUSIONS

Cell implantation holds promise for decreasing the effect of radiation on healing of irradiated wounds.

Effects of a hydrolyzed collagen dressing on the healing of open wounds in dogs

OBJECTIVE

To determine the effects of a hydrolyzed bovine collagen dressing (HBCD) on healing of open wounds in healthy dogs.

ANIMALS

9 female Beagles.

PROCEDURES

2 full-thickness skin wounds were made bilaterally on the trunk of each dog. Wounds on 1 side were treated with powdered HBCD covered with a semiocclusive nonadherent bandage. Wounds on the other side (control wounds) were covered with a semiocclusive nonadherent bandage only. Wound healing was subjectively assessed, and percentage increase in tissue perfusion was assessed by use of laser Doppler perfusion imaging (LDPI). Planimetry was performed to determine the percentages of contraction, epithelialization, and total wound healing. Biopsy specimens were examined microscopically to evaluate histologic changes.

RESULTS

The HBCD did not induce a strong inflammatory reaction, as reflected by results of LDPI and histologic examination. Moreover, HBCD appeared hydrophilic and provided an environment to keep wounds clean and enhance early epithelialization. After treatment for 7 days, treated wounds had a significantly greater percentage of epithelialization than control wounds (12.13 vs. 7.03%).

CONCLUSION AND CLINICAL RELEVANCE

The hydrophilic property of HBCD may cleanse contaminated wounds with the body's homeostatic fluids and enhance early wound epithelialization.

Fibrin sealant in wound repair: a systematic survey of the literature

Fibrin sealants have recently been approved for clinical use in the US by the FDA and have been available for clinical use in Europe for years. The indication for use in the US is haemostasis. Nevertheless, both commercial and non-commercial fibrin sealant preparations are also for wound healing and for prevention of abdominal adhesions in the US and Europe. To the non-cognoscenti of fibrin sealants, their use to promote wound repair and to prevent abdominal adhesions appears contradictory since an agent that promotes connective tissue repair might be expected to promote abdominal adhesion rather than prevent them. In this systematic survey of the animal and clinical data evidence is presented that supports both off-label uses. However there is much inconsistency in the data secondary to the use of various fibrin sealant preparations, different animal models and clinical situations and different application techniques. It is clear from this survey that standard preparation and application of fibrin sealant for a particular surgical setting are needed to resolve the many apparent discrepancies in the literature. A corollary to this is the likelihood that different fibrin sealant preparations may be preferred for different clinical situations.