Physiology of the Acute Wound

Wound Healing and Physiology of Skin Flaps

This article focuses on the dynamic process of wound healing, including the three phases of wound healing and the different types of wound healing. The physiology of skin flaps is described, with a focus on the vascular supply and biomechanics of skin flaps. The article reviews older and newer concepts of skin flap design.

Acute vocal fold wound healing in a rabbit model

Several authors have eloquently described the characteristics of vocal fold scar, a long-term consequence of vocal fold injury. However, events in the acute stage of mucosal injury, which lead up to fibrosis, have been largely overlooked. The current study describes acute events with regard to mucosal re-formation in a rabbit model. Vocal fold injury was induced surgically. A fibrinous clot was present 1 day after injury. Massive cellular infiltration was noted on day 3, and complete epithelial coverage was achieved by day 5. Also, neo-matrix deposition was noted as early as 5 days after injury, and more mature collagen was seen by day 7. The general timetable described in the current study can contribute to the experimental foundation for the development of regenerative models of healing in the vocal folds. Most notably, the proliferation phase of wound healing appears to occur approximately 3 days after injury, indicating a critical time for intervention. Manipulation and/or alteration of naturally occurring neo-matrix deposition and organization may yield improved biophysical function of the injured vocal fold.

Posttraumatic inflammation is a complex response based on the pathological expression of the nervous, immune, and endocrine functional systems

The successive phases that make up both the local and systemic posttraumatic acute inflammatory response could represent the expression of three concatenated pathological or "primitive" functional systems with trophic properties: the nervous, immune, and endocrine ones. The nervous functional system would play an important role in the phenomenon of ischemia-reperfusion, which would be represented by nutrition by diffusion that is either anaerobic (ischemia) or with defective use of oxygen (reperfusion) and, thus, with a limited energy requirement. The immune functional system would be represented by the infiltration of the tissues by inflammatory cells and bacteria, which would become mediators in providing nutrition to the injured tissues. Although the use of oxygen would still be defective, hypermetabolism and fever would occur. In these inflammatory response phases, the lymphatic is the most important circulation. The endocrine functional system would be the most specialized and would have high energy requirements because it would be represented by the blood capillary-mediated nutrition. Highly specialized epithelial cells would already possess a perfected oxidative metabolism. The successive expression of these three functional systems during embryonic development and also during the evolutionary development of our species could explain why the inflammatory response is a ubiquitous mechanism that is common to multiple diseases, because it is an integrator of the ontogeny and phylogeny.

Closure of skin incisions in rabbits by laser soldering: I: Wound healing pattern

BACKGROUND AND OBJECTIVES

Temperature-controlled tissue laser soldering is an innovative sutureless technique awaiting only solid experimental data to become the gold-standard surgical procedure for incision closure. The goals of the current study were: (1) to define the optimal laser soldering conditions, (2) to explore the immediate skin reparative healing events after sealing the wound, and (3) to determine the long-term trajectory of skin wound healing.

STUDY DESIGN/MATERIALS AND METHODS

Skin incisions were generated over rabbit dorsa and were closed using different wound-closure interventions, in three groups: (a) closure, using a temperature-controlled infrared fiberoptic CO2 laser system, employing 47% bovine serum albumin as a solder; (b) wound closure by cyanoacrylate glues; and (c) wound closure by sutures. The reparative outcomes were evaluated macroscopically and microscopically, employing semi-quantitative grading indices.

RESULTS

Laser soldering of incisions at T = 65 degrees C emerged as the optimal method achieving immediate wound sealing. This in turn induced accelerated reparative events characterized by a reduced inflammatory reaction, followed by minimal scarring and leading to a fine quality healing.

CONCLUSIONS

Temperature-controlled laser soldering offers an accelerated wound reparative process with numerous advantages over the conventional methods. Further investigations may reveal additional benefits in the spectrum of advantages that this innovative surgical technology has to offer. This can introduce new scientific insight that will pave the way for clinical use.

Closure of skin incisions in rabbits by laser soldering II: Tensile strength

BACKGROUND AND OBJECTIVES

The basic characteristic property of wound closure is the immediate and long-term tensile strength (LTS). The objective of the current study was to compare tissue laser soldering to other available methods (i.e., cyanoacrylate glues and sutures) in the performance and outcome of wound closure and reparative healing process, with an emphasis on the immediate and LTS.

STUDY DESIGN/MATERIALS AND METHODS

The animals were divided into three groups according to the type and details of the closure procedure. Group A: laser treatments at different temperatures were compared to sutured incisions, emphasizing the LTS after 10 days. Group B: laser soldering at 65 +/- 5 degrees C was compared to chemical glues (i.e., Histoacryl and Dermabond), emphasizing the immediate tensile strength (ITS). Group C: LTS of laser soldered incisions was compared to that of sutured incisions at various time intervals emphasizing LTS (3, 7, 14, 28 days).

RESULTS

Group A: LTS at 60 degrees C exhibited the highest values (0.48 MPa). Group B: no ITS difference was detected between laser soldering and chemical glues. Group C: soldered incisions at 65 degrees C exhibited higher LTS (1.81 MPa) than that of sutured incisions (1.08 MPa) (P < 0.043).

CONCLUSIONS

Temperature-controlled laser soldering at 65 degrees C provided sufficient ITS and higher bonding LTS values compared with sutures, resulting in better wound healing characteristics. The laser soldering system presented here should be tested on larger animal models before adopting it for clinical usage.

Inflammatory mediators in wound healing

This article provides much evidence that the inflammatory process has direct effects on normal and abnormal wound healing. As better understanding develops for the mechanism for these outcomes, targeted proinflammatory and anti-inflammatory interventions are likely to be successful. When inflammation is maintained as a regulated and orchestrated response, effective and normal wound healing is likely to result.

Acute wound healing an overview

The ability to heal an injury is a biologic necessity for all organisms, with mammals lagging in proficiency when compared with lower life forms that have the ability to regenerate differentiated structures. Technology and increased scientific knowledge have established a coordinated interplay that has improved the ability to manage wounds in a logical manner, and, on occasion, to accelerate the healing process. Insight into the complex chain of events leading to the formation of scar is a necessity for every individual who attempts wound management.

Healing the diabetic wound and keeping it healed: modalities for the early 21st century

The incidence of lower extremity wounds, infections, and amputations continues to increase worldwide. Fortunately, the past decade has seen a surge of activity in research into new modalities in wound healing and, even more recently, prevention. This article discusses the basic physiology of wound healing, with particular attention being paid to current and potential wound healing modalities. These include, among other modalities, discussions of bioengineered skin, hyaluronic acid, subatmospheric pressure therapy, growth factors, and endogenous cytokine stimulation. Emerging concepts targeting prevention through novel methods of patient empowerment, dermal thermometry, and computerized activity monitoring are also discussed.

Gene expression analysis in burn wounds of rats

The events occurring early in the burn wound trigger a sequence of local and systemic responses that influence cell and tissue survival and, consequently, wound healing and recovery. Using high-density oligonucleotide arrays we identified gene expression patterns in skin samples taken from a region of injury in the burn rat model. The associated genomic events include the differential expression of genes involved in cell survival and death, cell growth regulation, cell metabolism, inflammation, and immune response. The functional gene cluster detected and their time appearance matched the time sequence known to occur in burn wound healing.

Regional differences in the extracellular matrix of the human spongy urethra as evidenced by the composition of glycosaminoglycans

PURPOSE

Despite the concept that the spongy urethra is a unique entity clinical evidence suggests the existence of segmental structural differences. The spongy urethra has a vascular nature, its cells may express different phenotypes and the extracellular matrix that they synthesize should reflect these differences. Glycosaminoglycans are components of the extracellular matrix that have key roles in the normal physiology and pathology of several tissues. Although total collagen content of the urethra was determined, we also analyzed urethral glycosaminoglycans (GAGs).

MATERIALS AND METHODS

Fresh, macroscopically normal cadaveric urethral samples were obtained from 15 men who died at a mean age of 25.4 years. The urethra was divided into glanular, penile and bulbar segments, which were then analyzed separately. Total GAG concentration was assessed by hexuronic acid assay and expressed as microg. hexuronic acid per mg. dry tissue, while the proportions of sulfated GAGs were determined by agarose gel electrophoresis. Hyaluronan concentration was determined by ion exchange chromatography and total tissue collagen was estimated as hydroxyproline content.

RESULTS

Total GAG concentration was heterogeneous along the spongy urethra (p <0.001). Mean values plus or minus standard deviation in the glanular, penile and bulbar segments were 2.53 +/- 0.42, 2.11 +/- 0.47 and 1.47 +/- 0.4 microg./mg., respectively. The most predominant GAG was hyaluronan and its highest mean concentration of 50.1% +/- 3.7% was found in the glanular urethra. The most predominant sulfated GAG in the male urethra was dermatan sulfate, followed by chondroitin sulfate and heparan sulfate. Total collagen content and the GAG-to-collagen ratio varied along the spongy urethra and were lowest in the bulbar segment.

CONCLUSIONS

The extracellular matrix of the human spongy urethra shows regional differences, as evidenced by biochemical analysis of GAG and collagen. This heterogeneity implies functional adaptations in the various segments and may affect the physiology and segmental incidence of urethral diseases.

Laser soldering of rat skin, using fiberoptic temperature controlled system

BACKGROUND AND OBJECTIVE

Laser soldering of tissues is based on the application of a biological solder on the approximated edges of a cut. Our goal was to use laser soldering for sealing cuts in skin under temperature feedback control and compare the results with ones obtained using standard sutures.

STUDY DESIGN/MATERIALS AND METHODS

Albumin solder was applied onto the approximated edges of cuts created in rat skin. A fiberoptic system was used to deliver the radiation of a CO(2) laser, to heat a spot near the cut edges, and to control the temperature. Laser soldering was carried out, spot by spot, where the temperature at each spot was kept at 65-70 degrees C for 10 sec.

RESULTS

The tensile strength of laser-soldered cuts was measured after 3-28 days postoperatively and was found comparable to that of sutured cuts. Histopathological studies showed no thermal damage and less inflammatory reaction than that caused by standard sutures (P = 0.04).

CONCLUSIONS

Temperature controlled laser soldering of cuts in rat skin gave strong bonding. The cosmetic and histological results were very good, in comparison to those of standard sutures.

Neuro-immune-endocrine functional system and vascular pathology

A new interpretation of the response to injury by the nervous, immune and endocrine system is proposed, in order to integrate biochemical knowledge into the respective clinical areas. The discovery that the signaling molecules of the classical nervous, immune and endocrine systems, that is, the neurotransmitters, cytokines and hormones, respectively, are expressed and perceived by the three systems, has enabled us to establish a functional concept of these systems. The hypothetical integration of different pathological processes in a functional response made up by three phases, the immediate or nervous, intermediate or immune and late or endocrine ones, makes it possible to consider that all of them represent different forms of expression of a functional response whose meaning is always the same, that is, inflammation. If the functions that characterize each one of these three phases represent the activity of the nervous, immune and endocrine systems, the biochemical knowledge could be integrated into the functional meaning of each system.

Postsurgical wound management

Successful outcomes in cutaneous surgery depend on a variety of factors, including preoperative assessment of the patient's health and expectations, intraoperative skill and attention to detail, and managing the postoperative period. Once the procedure is complete, careful selection of dressings, provision of adequate analgesia, judicious management of complications and monitoring the phases of early maturation while providing patient education improve the likelihood of long-term patient and physician satisfaction.

p63 expression during normal cutaneous wound healing in humans

p63, a recently identified member of the p53 family, was shown to play a role in morphogenesis and, probably, in tumors of keratinocyte origin. Because p63 seems to be a marker of keratinocytes with a high proliferative potential, the expression of this protein was studied along with another marker of cell proliferation, Ki67, during normal epidermal regeneration in humans. Serial biopsies of human skin healing by a secondary intention were taken at various time intervals (between days 2 and 21 after the injury) and were studied immunohistochemically with the use of a 4A4 monoclonal antibody against the DeltaNp63 variant and MM1 monoclonal antibody against the Ki67 antigen. In the normal and injured skin, the expression of the DeltaNp63 protein was restricted to the epidermal keratinocytes and hair follicle keratinocytes. In the first days of the healing process, there was a dramatic down-regulation of both DeltaNp63 and Ki67 expression in the area of the epidermal tongue invading under the crust. Five days after the injury, induction of DeltaNp63 in the basal keratinocytes could be detected, followed by a gradual increase of its expression in subsequent days. Several days after complete wound closure, DeltaNp63 was still strongly expressed not only in the basal keratinocytes but also in the entire spinous layer, whereas the Ki67 expression was restricted to single cells in the basal layer. The results indicate that DeltaNp63 could be involved in the control of physiologic processes, such as cell proliferation and migration, related to epidermal repair during healing of normal skin in humans.

Dynamic contrast-enhanced MRI studies in oncology with an emphasis on quantification, validation and human studies

Magnetic resonance imaging (MRI), after the administration of an extracellular, gadolinium-based contrast medium, can be used to detect and characterize human tumours. The success of dynamic contrast-enhanced MRI (DCE-MRI) is dependent on its ability to demonstrate intrinsic differences between a variety of tissues that affect contrast medium behaviour. Evidence is mounting that DCE-MRI measurements correlate with immunohistochemical surrogates of tumour angiogenesis. DCE-MRI can monitor the effectiveness of a variety of treatments including chemotherapy, hormonal manipulation, radiotherapy and novel therapeutic approaches including antiangiogenic drugs. Kinetic parameters in the treatment setting have been correlated with histopathological outcome and patient survival. This article reviews quantification analysis of these studies together with current and future clinical applications.

In-vivo particle mediated delivery of mRNA to mammalian tissues: ballistic and biologic effects

Biolistic transmission of mRNA provides transient gene therapy to in vivo organs. This study documents particle mediated mRNA transmission to a solid organ and wound healing model using the mRNA of Green Fluorescent Protein to determine optimal delivery parameters. Renal function, bullet penetration, cellular injury, and Green Fluorescent Protein synthesis were quantified. Chimeric human epidermal growth factor-FLAG epitope cDNA or mRNA was transmitted to wounds in normal or steroid treated animals. Wound bursting strength, human epidermal growth factor-FLAG, and collagen synthesis were determined. Injury and bullet penetration correlated with the delivery velocity and bullet size. Optimal delivery parameters were established which provided widespread Green Fluorescent Protein synthesis. Human epidermal growth factor-FLAG treatment significantly increased collagen content and wound breaking strength in normal and steroid treated animals. FLAG protein synthesis was evident in mRNA treated fascia following treatment. We found the gene gun provides a novel method for efficient, in vivo delivery of mRNA-based therapeutic strategies to mammalian organs with minimal histologic damage allowing transient expression of protein in in vivo target tissues. Co-delivery of Green Fluorescent Protein mRNA may provide a useful positive control to determine effective transmission. Biolistic transmission of human epidermal growth factor-FLAG mRNA provides increased tissue epidermal growth factor levels and accelerates wound healing in normal and steroid exposed animals.

Effect of soft-tissue trauma on the early periosteal response of bone to injury

OBJECTIVE

To determine whether the periosteal response to skeletal trauma is impaired when muscle is also injured, thereby providing a possible explanation for why fractures with extensive soft-tissue damage may take longer to heal.

METHODS

A bone defect was made in the tibia of male Fisher rats, and the proliferative response, osteoblast concentration, and callus formation that occurred within 7 days were measured in the presence and absence of simultaneously administered model soft-tissue injury (removal of 10% of the anterior tibialis muscle from a region within 2 to 3 mm of the bone defect). Measurements were made by using autoradiography, quantitative histology, and morphometry.

RESULTS

Addition of the muscle injury increased proliferation in the cambium and in the fibrous periosteum on day 1, but had no effect thereafter; proliferation of fibroblasts in the loose connective tissue above the periosteum was not affected. Addition of the muscle injury resulted in increased osteoblast levels 2 to 5 days after injury but had no effect on the amount of callus produced.

CONCLUSION

The inflammatory milieu created by the muscle injury unexpectedly resulted in an increased periosteal response to skeletal trauma, suggesting that inflammatory mediators generated in response to wounding of soft tissues are unlikely to account for delayed fracture healing. These findings may indicate that surgical trauma associated with internal fixation by using plates and screws may not be as deleterious to the fracture-healing response as previously thought.

The antifibrogenic effects of liposome-encapsulated IFN-alpha2b cream on skin wounds

Interferons (IFN), including IFN-alpha2b, have been used as antifibrogenic factors to modulate the excessive production of extracellular matrix (ECM) associated with dermal fibroproliferative disorders. This study was conducted to examine the ability of a dermal cream containing liposome-encapsulated IFN-alpha2b (LIPO+IFN) to affect the synthesis of ECM in open and reepithelialized wounds. Full-thickness skin wounds in 32 female Hartley guinea pigs (6 wounds per animal, 3 on each side) were made with an 8-mm biopsy punch. Each wound on the right side received 3,000 U LIPO+IFN, whereas wounds on the left side received cream containing empty liposomes. Histologic examination revealed a significant reduction in scar formation in LIPO+IFN-treated but not in vehicle-treated wounds. Northern analysis showed reductions in type I procollagen mRNA in healed wounds treated with LIPO+IFN (day 4 groups: 1596.9 +/- 207 vs. 3710.2 +/- 493 densitometry units, p < 0.01, n = 8). This was consistent with a reduction in the concentration of collagen in the tissue, assayed as 4-hydroxyproline (day 4 group: 38.5 +/- 3.8 vs. 54.5 +/- 3.9 microg per tissue, p < 0.01, n = 8). Even when applied to reepithelialized wounds, LIPO+IFN caused a marked reduction in type I collagen mRNA (1938.5 +/- 579 vs. 4085.7 +/- 1271 densitometry units, p < 0.01, n = 8). These findings support the concept of the early topical use of this antifibrogenic agent for treatment of dermal fibroproliferative disorders, such as hypertrophic scars.