Initiating the inflammatory phase of incisional healing prior to tissue injury

Long-Term Controlled Growth Factor Release Using Layer-by-Layer Assembly for the Development of In Vivo Tissue-Engineered Blood Vessels

The development of a well-designed tissue-engineered blood vessel (TEBV) still remains a challenge. In recent years, approaches in which the host response to implanted biomaterials is used to generate vascular constructs within the patient's body have gained increasing interest. The delivery of growth factors to these in situ-engineered vascular grafts might enhance myofibroblast recruitment and the secretion of essential extracellular matrix proteins, thereby optimizing their functional properties. Layer-by-layer (LbL) coating has emerged as an innovative technology for the controlled delivery of growth factors in tissue engineering applications. In this study, we combined the use of surface-etched polymeric rods with LbL coatings to control the delivery of TGF-β1, PDGF-BB, and IGF-1 and steer the foreign body response toward the formation of a functional vascular graft. Results showed that the regenerated tissue is composed of elastin, glycosaminoglycans, and circumferentially oriented collagen fibers, without calcification or systemic spill of the released growth factors. Functional controlled delivery was observed, whereas myofibroblast-rich tissue capsules were formed with enhanced collagen and elastin syntheses using TGF-β1 and TGF-β1/PDGF-BB releasing rods, when compared to control rods that were solely surface-engineered by chloroform etching. By combining our optimized LbL method and surface-engineered rods in an in vivo bioreactor approach, we could regulate the fate and ECM composition of in situ-engineered vascular grafts to create a successful in vivo vascular tissue-engineered replacement.

Immunohistochemical Expression of Cyclooxygenases in Hypertrophic Scars and Keloids

Background:

There are studies demonstrating an increased expression of cyclooxygenase (COX) in keloids and hypertrophic scars, suggesting that anti-inflammatory drugs could be used in their treatment. However, a precise relationship between COX and pathological scarring has not been established in the literature yet. This study aims to evaluate the immunohistochemical expression of COXs in these scars.

Methods:

Prospective study, including 54 patients (aged 18–60 years) undergoing scar excision: 18 normal scars (group 1), 18 hypertrophic scar (group 2), and 18 keloids (group 3). The group classification was performed by clinical criteria. Scars samples were collected and anatomopathological examination (through hematoxylin-eosin method) was performed to confirm the scar type. Immunohistochemistry was performed to assess the expression of COX1 and COX2 in epidermis and dermis. Results were compared among all groups and between group I versus II and III together (abnormal scars).

Results:

For COX1, in the epidermis, there was no significant difference in the immunohistochemical expression when comparing the 3 groups. In the dermis, groups 2 and 3 had greater expression than group 1, with a significant difference being found when comparing all groups (P = 0.014), and in the comparison between normal versus abnormal scars (P = 0.004). For COX2, there was no significant difference between the groups in both the epidermis and dermis.

Conclusions:

The immunohistochemical expression of COX1 was greater in the dermis of abnormal scars when compared with normal scars. Future studies can be performed involving COX blockade as a perspective of these scars treatment.

WOUND-HEALING PROPERTIES OF TRANSFORMING GROWTH FACTOR β (TGF-β) INDUCIBLE EARLY GENE 1 (TIEG1) KNOCKOUT MICE

Transforming growth factor beta (TGF-β) has a broad effect on wound healing, but many questions remain about the regulation of TGF-β during the healing process. TGF-β inducible early gene 1 (TIEG1) is a primary response gene for TGF-β that controls the activities of the TGF-β/Smad pathway, the primary TGF-β signaling pathway. The purpose of this study was to investigate the role of TIEG1 in cutaneous wound healing using TIEG1 knockout mice. The wound healing in TIEG1 knockout mice and wild-type controls was evaluated by wound breaking strength, Western blot, and histology at postoperative days 3, 7, and 14. Although re-epithelialization of both groups was similarly complete at day 7, the TIEG1 knockout mice had a significantly lower wound breaking strength than the controls at postoperative day 14. These results suggest that TIEG1 expression may be an important factor involved in the initiation and support of normal cutaneous wound healing.

Platelet-rich fibrin versus albumin in surgical wound repair: a randomized trial with paired design

OBJECTIVE

To study the effects of autologous platelet-rich fibrin (PRF) versus human albumin on incisional wound breaking strength and subcutaneous collagen deposition in patients undergoing laparoscopic cholecystectomy in a randomized trial.

SUMMARY BACKGROUND DATA

Platelet peptidic growth factors may stimulate collagen synthesis and tissue repair.

METHODS

One expanded polytetrafluoroethylene (ePTFE) tube was inserted subcutaneously from the edge of each of the two 10-mm trocar incisions in 51 patients. Treatment with PRF prepared from the patient's own blood or human albumin was randomized to respective wound site by concealed allocation. On postoperative day 10, breaking strength of the incisional wounds as well as the collagen concentration, type I procollagen mRNA, type III procollagen mRNA, matrix metalloproteinase-1 mRNA, and fibroblast density in the ePTFE tubes were determined. All analyses were assessor-blinded. The trial was registered in the Current Controlled Trials Registry (ISRCTN34481461).

RESULTS

Local PRF had no significant effect on incisional wound-breaking strength. In the ePTFE tubes, PRF treatment decreased collagen concentration by 24% (P=0.046) and type I procollagen mRNA level by 29% (P=0.003), but had no significant impact on type III procollagen mRNA, matrix metalloproteinase-1 mRNA or fibroblast infiltration. The profibrotic transforming growth factor-beta1 level increased (P<0.0001) 2-fold with PRF. Collagen concentration in albumin-treated ePTFE tubes correlated with breaking strength of the skin incisions (rs=0.48, P=0.03).

CONCLUSIONS

PRF did not improve wound strength significantly compared with albumin but suppressed subcutaneous collagen synthesis and deposition during early repair of surgical wounds in humans. Furthermore, deposition of reparative collagen in the subcutaneous ePTFE tube model partly predicted the breaking strength of an incisional skin wound.

Effect of cytokine growth factors on the prevention of acute wound failure

Cytokine growth factor treatment of chronic wounds has met with mixed results. The chronic wound presents a hostile environment to peptides such as growth factors. Cytokine growth factors have not been studied extensively in acute wounds. However, incisional hernias are a major example of acute wound failure that has not been solved by various mechanical approaches. A biological approach to acute wound failure by use of cytokine growth factors may offer a new strategy. A rodent incisional hernia model was used. Seventy-six rats underwent 3-cm midline celiotomies and were closed with fine, fast-absorbing sutures to induce intentional acute wound failure. Group 1 received no other treatment. The midline fascia in Groups 2-10 was infiltrated with 100 microl of vehicle alone or vehicle containing various test cytokine growth factors. Necropsy was performed on postoperative day 28 and the wounds were examined for herniation. Incisional hernias developed in 83 percent (13/16) of untreated incisional and 88 percent (7/8) and 83 percent (5/6) of the two vehicle-treated incisions (PBS and carboxymethylcellulose). Hernia incidences were decreased by priming of the fascial incision with transforming growth factor-beta(2) (12%, 1/8), basic fibroblast growth factor (25%, 2/8) and interleukin-1 beta (50%, 3/6) (p < 0.05). Aqueous platelet-derived growth factor, becaplermin, insulin-like growth factor, and granulocyte macrophage-colony stimulating factor did not significantly decrease the incidence of acute wound failure (p > 0.05). A biological approach to acute wound failure as measured by incisional hernia formation can be useful in reducing the incidence of this complication. Transforming growth factor-beta(2), basic fibroblast growth factor, and interleukin 1 beta all eliminated or significantly reduced the development of incisional hernias in the rat model.

Profiles of inflammatory cytokines following colorectal surgery: Relationship with wound healing and outcome

Inflammation is an essential component of normal wound healing. This study has correlated systemic (plasma) and local (wound fluid) concentrations of inflammatory cytokines (interleukin [IL]-6, tumor necrosis factor-alpha [TNF-alpha], and IL-1beta) with wound healing and surgical outcome following elective colorectal surgery. Paired plasma and wound fluid samples were collected (n = 44) postoperatively (days 1, 3, 5, 7) and analyzed by enzyme-linked immunosorbent assay (pg/mL). Cytokine levels were significantly greater in drain fluid than plasma on each postoperative day (POD); e.g., POD 1 : IL-6; drain fluid, median, 77,050 pg/mL (range 9,928-456,408); plasma, 241 pg/mL (22-1,333). Daily profiles of IL-6 and TNF-alpha were similar in drain fluid and plasma; IL-6 levels peaked on POD 1 decreasing to POD 7, and TNF-alpha levels increased from PODs 1 to 7. However, IL-1beta in plasma peaked on POD 1 and plateaued, whereas drain fluid showed two peaks (PODs 1 and 7). Only plasma levels of cytokines correlated to clinical parameters; IL-6 levels significantly correlated with postoperative complications; e.g., POD 5, complications 92(1-597) and no complications, 14(2-217). IL-6 also correlated with tumor pathology (Dukes stage, tumor depth, vascular invasion), and TNF-alpha levels correlated with the estimated blood loss during surgery. We conclude that local wound levels of cytokines correlated with the stage of wound healing, whereas systemic levels correlated with postoperative complications and tumor pathology.

Local administration of TGF-β1 to reinforce the anterior abdominal wall in a rat model of incisional hernia

The purpose of this study was to investigate different forms of the local application of TGF-beta(1) for augmentation of the anterior abdominal wall in an appropriate model of an incisional hernia. Sixty male Sprague-Dawley rats were divided into six groups. Artificial defects of the anterior abdominal wall were closed with one of the following methods: running Prolene suture, Vicryl mesh, prolene suture followed by an intramuscular injection of 1 mug TGF-beta(1), Vicryl mesh coated with 1 mug TGF-beta(1), and prolene suture coated with 1 mug TGF-beta(1). A control group did not receive any defect and treatment. Six weeks after operation, tensile strength, collagen content, gene expression of collagen I and III, blood vessels, and thickness of collagen fibres were evaluated. Tensile strength was strongest in the controls (14.2 (10.5-18 N)). There was no increase in tensile strength due to the administration of TGF-beta(1). On the contrary, bolus injection of the growth factor resulted in a significantly decreased strength of the wound tissue when compared to the groups 1, 4, 5, and 6 (9.1 (4.2-9.1 N)). These results correlated with the gene expression of collagen I and III. Local application of TGF-beta(1) did not augment the strength of the abdominal wall after 6 weeks.

Evaluation of antibiotic-loaded collagen-hyaluronic acid matrix as a skin substitute

The 1-ethyl-(3-3-dimethylaminopropyl) carbodiimide hydrochloride-crosslinked collagen-hyaluronic acid (HA) matrices containing tobramycin or ciprofloxacin as an antibiotic agent were fabricated for the control of wound contamination and characterized with respect to morphology, mechanical strength, in vitro release, antibacterial activity and cytotoxicity. For the tobramycin loaded matrix, the antibacterial capacity increased with the drug loading. Tobramycin and ciprofloxacin loaded matrices maintained their antibacterial effects for over 96 and 48 h, respectively. However, cell viability testing revealed that 0.4 mg/ml of ciprofloxacin has a cytotoxic effect on fetal human dermal fibroblasts. The effects of the bilayered collagen-HA matrices containing tobramycin and growth factors were also evaluated using an in vivo full thickness dermal defect model. Though the tobramycin incorporated collagen-HA matrix had no significant effect on wound healing compared with the control, the tobramycin incorporated matrix containing basic fibroblast growth factor or platelet-derived growth factor significantly enhanced wound healing. This study demonstrates the potential efficacy of crosslinked collagen-HA matrix containing antibiotics and growth factors for defective skin tissue replacement and infection prevention.

Local administration of hepatocyte growth factor gene enhances the regeneration of dermis in acute incisional wounds

Hepatocyte growth factor (HGF) has a number of biological activities, e.g., mitogenic, motogenic, antiapoptotic, antifibrous, and morphogenic. It also has angiogenic and angioprotective activities for endothelial cells. The aim of this study was to characterize the role of HGF in wound healing by administering the HGF gene locally to acute incisional skin wounds created on the backs of rats. To create wounds, the backs of Wistar rats were clipped and three 2-cm-long incisional wounds were made deep to the fascia. The wounds contained pannicrus carnosum and were created at intervals of 2 cm. After suturing, the HGF gene was then administered intradermally. Apoptotic cells in wound lesions were identified by TUNEL method as well as by immunological detection of active caspase-3. In the HGF-treated animals, we found almost complete suppression of apoptosis and well-organized wound healing. Histopathological examination revealed that the proliferation of fibroblasts was suppressed and that scar formation was less apparent in the HGF-treated animals compared to the controls. It is thought that administration of the HGF gene immediately after surgery may enhance the healing process through suppressing apoptosis, which occurred in the controls 1 week after suturing the incisional wound. In addition, locally increased HGF expression due to the introduction of the HGF gene to cells around wounds enhances dermal regeneration, possibly by promoting regeneration of dermal tissue, which results in less scarring due to its antifibrotic effect. Thus, HGF supplementation through gene therapy may be an effective strategy for treating wounds, as it increases the regeneration of the dermis to allow for "scarless wound healing."

Effects of granulocyte macrophage colony stimulating factor on random flap healing and immune profile in rats with impaired wound healing by glucocorticoids

Wound healing involves inflammation, cell proliferation, matrix deposition, and tissue remodeling. Priming the tissue to be incised with proinflammatory cytokines offers a new approach to wound healing. This has been studied mostly in incisional wounds till now. This study was designed to investigate the role of granulocyte macrophage colony stimulating factor (GM-CSF) priming of planned incision lines in random flaps in rats with impaired wound healing due to glucocorticoid administration, and immune profiles of rats were also evaluated. GM-CSF priming of incision lines in immunosuppressed rats was shown to improve the wound healing parameters, hydroxyproline levels, breaking strength, flap survival, and immune profile, although all of the parameters were somewhat lower than those of control group. The findings of this study suggest that wound healing can be accelerated and thus morbidity lowered by making use of the immunomodulator effects of GM-CSF in cases where wound healing is impaired due to systemic disease or drug use and flap reconstruction is necessary.

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.

Acute wound healing: the biology of acute wound failure

Acute wound healing failure is an important source of morbidity and mortality for surgical patients. Many incisional hernias, gastrointestinal anastomotic leaks, and vascular pseudoaneurysms occur despite patient optimization and standardized surgical technique. Modern surgical experience suggests that biologic and mechanical pathways overlap during "normal" acute wound healing. The cellular and molecular processes activated to repair tissue from the moment of injury are under the control of biologic and mechanical signals. Successful acute wound healing occurs when a dynamic balance is met between the loads placed across a provisional matrix and the feedback and feed-forward responses of repair cells.

Wound-healing trajectories

Healing of a wound is a dynamic process involving soluble mediators, a variety of cells, and extracellular matrix. These components are involved in a number of different processes or steps in healing, including coagulation, inflammation, fibroplasia, collagen deposition, epithelialization, and scar contraction with remodeling. The processes can be organized into three phases: inflammation, fibroplasia, and remodeling. The events in healing occur in an orderly and timely fashion, and there is significant overlap between each of the processes.

Fibroblasts from chronic wounds show altered TGF-beta-signaling and decreased TGF-beta Type II receptor expression

Chronic wounds are characterized by failure to heal in a defined time frame. However, the pathogenic steps leading from the etiological factors to failure to heal are unknown. Recently, increasing evidence suggests that resident cells in chronic wounds display a number of critical abnormalities, including senescence and unresponsiveness to the stimulatory action of transforming growth factor-beta1 (TGF-beta1). In this study, we have determined some of the mechanisms that might be responsible for unresponsiveness to TGF-beta1. Using Northern analysis and affinity labeling, we show that venous ulcer fibroblasts have decreased TGF-beta Type II receptor expression. This finding is not the result of genetic mutation, as shown by experiments with Type II receptor satellite instability. Decreased Type II receptor expression was accompanied by failure of ulcer fibroblasts to phosphorylate Smad 2, Smad 3, and p42/44 mitogen activating protein kinase (MAPK), and was associated with a slower proliferative rate in response to TGF-beta1. We conclude that venous ulcer fibroblasts show decreased Type II receptor expression and display abnormalities in the downstream signaling pathway involving MAPK and the early Smad pathway. These findings suggest ways to address and treat the abnormal cellular phenotype of cells in chronic wounds.

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.

Reduction of scar formation in full-thickness wounds with topical celecoxib treatment

Adult wound repair occurs with an initial inflammatory response, reepithelialization, and the formation of a permanent scar. Although the inflammatory phase is often considered a necessity for successful adult wound healing, fetal healing studies have shown the ability to regenerate skin and to heal wounds in a scarless manner in the absence of inflammation. The cyclooxygenase-2 (COX-2) enzyme, a known mediator of inflammation, has been shown to contribute to a variety of inflammatory conditions and to the development of cancer in many organs. To examine the role of COX-2 in the wound healing process, incisional wounds were treated topically with the anti-inflammatory COX-2 inhibitor celecoxib. Acutely, celecoxib inhibited several parameters of inflammation in the wound site. This decrease in the early inflammatory phase of wound healing had a significant effect on later events in the wound healing process, namely a reduction in scar tissue formation, without disrupting reepithelialization or decreasing tensile strength. Our data suggest that in the absence of infection, adult wound healing is able to commence with decreased inflammation and that anti-inflammatory drugs may be used to improve the outcome of the repair process in the skin by limiting scar formation.

Cytokine manipulation of the wound

Most individuals expect that healing is an inevitable outcome; wound healing is taken for granted. Although wound healing is perceived as inevitable, it can be fraught with problems and altered at many points. In the past, optimization of wound healing focused on minimizing contamination, accurate tissue approximation, and providing protection. With the advent of recombinant technology, optimization can now include manipulation of the molecular and cellular wound environment. Although the exact manipulative scheme has not yet evolved, it is clear from the multiple attempts reported in this article that understanding and progress is being made.

Dose-dependent impairment of collagen deposition by topical granulocyte-macrophage colony-stimulating factor in human experimental wounds

OBJECTIVE

The authors studied the dose-dependent effect of topically administered granulocyte-macrophage colony-stimulating factor (GM-CSF) on the connective tissue response using an experimental repair model in surgical patients.

SUMMARY BACKGROUND DATA

GM-CSF is primarily indicated in the treatment of immunosuppressed states. The effect of GM-CSF on the tissue repair response in humans is unclear.

METHODS

Expanded polytetrafluoroethylene tubes were implanted subcutaneously and GM-CSF was applied locally at concentrations of 0.1 micro g/mL (total dose 0.4 micro g), 1.0 micro g/mL (4.0 micro g), 10 micro g/mL (40 micro g), or 75 micro g/mL (300 micro g) in one arm and saline alone (control) in the contralateral arm of 56 surgical patients. The content of collagen and total protein in the tubes was quantified as hydroxyproline and proline by high-performance liquid chromatography 10 days after implantation. Cellularity and the number of procollagen I-positive fibroblasts were determined by histology and immunohistochemistry. The direct effects of GM-CSF on collagen production by and proliferation of wound fibroblasts cultured from granulation tissue were also measured.

RESULTS

Local application of GM-CSF stimulated the inflammatory cell infiltration but reduced the number of fibroblasts in the granulation tissue. GM-CSF treatment suppressed specifically and dose-dependently collagen deposition by up to 81%. A reduced collagen accumulation was also found in the control-treated arm at GM-CSF doses of 4 micro g or more, indicating a systemic depressive effect of GM-CSF on tissue repair. The selective downregulation of collagen production by GM-CSF was also found in wound fibroblasts in vitro.

CONCLUSIONS

Inhibition of fibrogenesis with GM-CSF intervention may impair tissue repair processes during surgery.

Dose-dependent impairment of collagen deposition by topical granulocyte-macrophage colony-stimulating factor in human experimental wounds

OBJECTIVE

The authors studied the dose-dependent effect of topically administered granulocyte-macrophage colony-stimulating factor (GM-CSF) on the connective tissue response using an experimental repair model in surgical patients.

SUMMARY BACKGROUND DATA

GM-CSF is primarily indicated in the treatment of immunosuppressed states. The effect of GM-CSF on the tissue repair response in humans is unclear.

METHODS

Expanded polytetrafluoroethylene tubes were implanted subcutaneously and GM-CSF was applied locally at concentrations of 0.1 micro g/mL (total dose 0.4 micro g), 1.0 micro g/mL (4.0 micro g), 10 micro g/mL (40 micro g), or 75 micro g/mL (300 micro g) in one arm and saline alone (control) in the contralateral arm of 56 surgical patients. The content of collagen and total protein in the tubes was quantified as hydroxyproline and proline by high-performance liquid chromatography 10 days after implantation. Cellularity and the number of procollagen I-positive fibroblasts were determined by histology and immunohistochemistry. The direct effects of GM-CSF on collagen production by and proliferation of wound fibroblasts cultured from granulation tissue were also measured.

RESULTS

Local application of GM-CSF stimulated the inflammatory cell infiltration but reduced the number of fibroblasts in the granulation tissue. GM-CSF treatment suppressed specifically and dose-dependently collagen deposition by up to 81%. A reduced collagen accumulation was also found in the control-treated arm at GM-CSF doses of 4 micro g or more, indicating a systemic depressive effect of GM-CSF on tissue repair. The selective downregulation of collagen production by GM-CSF was also found in wound fibroblasts in vitro.

CONCLUSIONS

Inhibition of fibrogenesis with GM-CSF intervention may impair tissue repair processes during surgery.

The effects of basic fibroblast growth factor (bFGF) on the breaking strength of acute incisional wounds

Many researchers have reported the effects of cytokines on ulcers, especially on chronic ulcers. However, the long-term influences of cytokines on acute incisional wounds with respect to breaking strength, quality of the scar etc. have not been elucidated completely. In the present study, the breaking strength of scars produced by full thickness incisional wounds of the skin created on backs of rabbits were compared when the wounds were treated by conventional suturing or with basic fibroblast growth factor (bFGF) in addition to suturing. We administered bFGF to full thickness acute incisional wounds of the skin created on backs of rabbits. The breaking strengths of wounds treated by conventional suturing and those treated with bFGF soon after the operation were compared as were the conditions of the scars after long-term follow up of up to 7 weeks. They were also examined histopathologically. Administration of bFGF at the time of wound closure, especially 1.0 microg in amount per cm, increased the breaking strength significantly compared to the control group from 5 weeks after the operation. Moreover, histopathological examination revealed that there was rich vascularization soon after the operation and an arrangement of collagen fibers which lenticulated horizontally from the 5th week and later after the operation in the bFGF treated groups in a dose dependent manner. This study demonstrates that administration of bFGF at the time of wound closure significantly increased the breaking strength compared to the control group from 5 weeks after the operation. And the administration of bFGF also improved the quality of the scar, the condition of the scar by surface condition by inspection as well as the width of scar at histological evaluations. So we think this cytokine may be highly effective clinically. This may be especially true for patients whose wound healing process tends to be delayed such as aged patients or when high breaking strength is recommended even for patients with normal wound healing potential.

Expression of CD3 and CD11b antigens on blood and mammary gland leukocytes and bacterial survival in milk of cows with experimentally induced Staphylococcus aureus mastitis

OBJECTIVES

To differentiate early (1 to 8 days) from late (9 to 14 days) inflammatory phases and assess relationships between leukocyte phenotype and bacterial recovery in cows with Staphylococcus aureus-induced mastitis.

ANIMALS

10 first-lactation Holstein cows.

PROCEDURE

Blood and milk samples were collected from 4 or 6 cows before and after intramammary infusion of sterile broth or S. aureus, respectively. Flow cytometric expression of CD3 and CD11b antigens on blood and milk leukocytes, leukocyte differential counts, bacterial counts in milk, and somatic cell counts were determined longitudinally.

RESULTS

Density of CD3 molecules decreased on blood lymphocytes and increased on milk lymphocytes after infusion of bacteria. Density of CD11b molecules on lymphocytes and phagocytes and percentage of CD11b+ lymphocytes in milk increased significantly after infusion; maximum values were achieved during the early inflammatory phase. Density of CD3 and CD11b molecules on milk lymphocytes and macrophages, respectively, 1 day after inoculation were negatively correlated with bacterial recovery on day 1 and days 9 to 14, respectively. Density of CD11b molecules on milk macrophages and the ratios of phagocyte to lymphocyte percentages and polymorphonuclear cell to macrophage percentages in milk differentiated the early from the late inflammatory phase.

CONCLUSIONS AND CLINICAL RELEVANCE

Activation of bovine mammary gland macrophages and T cells in response to intramammary infusion of S. aureus was associated with an inability to culture this bacterium from milk. Identification of specific inflammatory phases of S. aureus-induced mastitis in cows may allow for the design of more efficacious treatment and control programs.

Longitudinal evaluation of bovine mammary gland health status by somatic cell counting, flow cytometry, and cytology

Bovine mastitis phases induced by Staphylococcus aureus were assessed in 6 lactating cows before challenge and at 1, 4-8, and 9-14 days postinoculation (dpi). Milk lymphocytes, macrophages, and polymorphonuclear cells (PMN) were counted by conventional (manual) cytology, identified by CD3+ and CD11b+ immunofluorescence and counted by flow cytometry (based on leukocyte forward and side light scatter values). Somatic cell counts (SCC) and recovery of bacteria were recorded at the same times. Preinoculation samples showed a lymphocyte-dominated composition. At 1 dpi, the percentage of PMN increased and that of lymphocytes decreased. At 4-8 dpi, PMN were predominant, but the percentage of mononuclear cells increased above that at 1 dpi and further increased by 9-14 dpi (when lymphocytes approached prechallenge values). Based on leukocyte percentages, 3 indices were created from the data: 1) the PMN/lymphocyte percentage ratio (PMN/L), 2) the PMN/macrophage percentage ratio (PMN/M), and 3) the phagocyte (PMN and macrophage)/lymphocyte percentage ratio (Phago/L). Significant correlations were found between cytologic and flow cytometric data in all of these indicators (all with P < or = 0.01). These indices identified nonmastitic, early inflammatory (1-8 dpi), and late inflammatory (9-14 dpi) animals. In contrast, SCC and bacteriology did not. Although sensitivity of the SCC was similar to that of Phago/L, the specificity of SCC was almost half that of the Phago/L index. Based on flow cytometry indicators, an algorithm for presumptive diagnosis of bovine mastitis was developed. Flow cytometry provides results as valid as those obtained by conventional (manual) cytology, shows greater ability to identify mastitic cases than does SCC, and may identify 3 mammary gland health-related conditions.

Transforming growth factor beta(2) lowers the incidence of incisional hernias

BACKGROUND

Approximately 200,000 incisional hernias are repaired annually in the United States. The high incidence (11-20%) and recurrence rate (24-54%) for incisional hernias have not changed appreciably in 75 years. Mechanical advances in suture material, incision orientation, and closure technique have failed to eliminate this common surgical complication. A biological approach to acute wound failure may offer a new strategy.

METHODS

A rodent incisional hernia model was used. Seventy rats underwent 5-cm midline celiotomies and were closed with fine, fast-absorbing sutures to induce intentional acute wound failure. Group 1 received no other treatment. The midline fascia in groups 2 and 3 was injected immediately prior to incision with 100 microl of vehicle alone or vehicle containing 1 microg of transforming growth factor beta(2) (TGF-beta(2)). Necropsy was performed on Postoperative Day 28 and the wounds were examined for herniation.

RESULTS

Incisional hernias developed in 88% (35/40) and 79% (11/14) of untreated incisions and those treated with vehicle alone. No hernias formed in the TGF-beta(2)-treated incisions (0/16, P < 0.05). Standard histology and immunohistochemistry demonstrated enhanced macrophage, lymphocyte, and fibroblast chemotaxis and increased collagen I and III production in TGF-beta(2) treated incisions.

CONCLUSIONS

Treatment of abdominal wall fascial incisions with TGF-beta(2) prevented the development of incisional hernias in this rat model. TGF-beta(2) stimulated fascial macrophage and fibroblast chemotaxis as well as acute wound collagen production. A biological approach such as this may reduce the incidence of incisional hernia formation in humans.

Use of the wound healing trajectory as an outcome determinant for acute wound healing

Accurate and clinically practical methods for measuring the progress of acute wound healing is necessary before interventions designed to optimize and even accelerate acute wound healing can be applied. Complete wound closure rates and operative wound closure severity are irrelevant to most acute wounds since most are closed at the time of primary tissue repair and remain closed throughout healing. Analogous to chronic wound closure, the rate of increase of incision tensile strength progressively decreases as time passes and 100% unwounded tissue strength is never achieved making the endpoint definition of "healed" vague. Conceptualizing acute wound healing in terms of its design elements with reintegration into a final outcome lends itself to the description of acute wound healing as a mathematical trajectory. Frequently such an equation is a rate expressing the change in an acute healing parameter, most often tensile strength, over time. Such an approach also normalizes misinterpretations in analysis or errors in theory developed by measuring healing parameters at fixed points in time. Distributions of fractional strength gain times (e.g., 85% normal strength) can be determined using statistical methodology similar that used for failure time of survival analysis. Preclinical studies show that acute wound healing trajectories can be shifted to the left from a "normal" or "impaired" curve to an accelerated or more "ideal" curve. A useful method for measuring acute wound healing outcomes is therefore required before the basic science of acute wound healing is inevitably applied to the problem of acute surgical wounds.