Recombinant human granulocyte colony-stimulating factor treatment improves macrophage suppression of granulocyte and macrophage growth after burn and burn wound infection

Clinical application of growth factors and cytokines in wound healing

Wound healing is a complex and dynamic biological process that involves the coordinated efforts of multiple cell types and is executed and regulated by numerous growth factors and cytokines. There has been a drive in the past two decades to study the therapeutic effects of various growth factors in the clinical management of nonhealing wounds (e.g., pressure ulcers, chronic venous ulcers, diabetic foot ulcers). For this review, we conducted an online search of Medline/PubMed and critically analyzed the literature regarding the role of growth factors and cytokines in the management of these wounds. We focused on currently approved therapies, emerging therapies, and future research possibilities. In this review, we discuss four growth factors and cytokines currently being used on and off label for the healing of wounds. These include granulocyte-macrophage colony-stimulating factor, platelet-derived growth factor, vascular endothelial growth factor, and basic fibroblast growth factor. While the clinical results of using growth factors and cytokines are encouraging, many studies involved a small sample size and are disparate in measured endpoints. Therefore, further research is required to provide definitive evidence of efficacy.

Inhalation injury severity and systemic immune perturbations in burned adults

OBJECTIVE

We aimed to determine whether the severity of inhalation injury evokes an immune response measurable at the systemic level and to further characterize the balance of systemic pro- and anti-inflammation early after burn and inhalation injury.

BACKGROUND

Previously, we reported that the pulmonary inflammatory response is enhanced with worse grades of inhalation injury and that those who die of injuries have a blunted pulmonary immune profile compared with survivors.

METHODS

From August 2007 to June 2011, bronchoscopy was performed on 80 patients admitted to the burn intensive care unit when smoke inhalation was suspected. Of these, inhalation injury was graded into 1 of 5 categories (0, 1, 2, 3, and 4), with grade 0 being the absence of visible injury and grade 4 corresponding to massive injury. Plasma was collected at the time of bronchoscopy and analyzed for 28 immunomodulating proteins via multiplex bead array or enzyme-linked immunosorbent assay.

RESULTS

The concentrations of several plasma immune mediators were increased with worse inhalation injury severity, even after adjusting for age and % total body surface area (TBSA) burn. These included interleukin (IL)-1RA (P = 0.002), IL-6 (P = 0.002), IL-8 (P = 0.026), granulocyte colony-stimulating factor (P = 0.002), and monocyte chemotactic protein 1 (P = 0.007). Differences in plasma immune mediator concentrations in surviving and deceased patients were also identified. Briefly, plasma concentrations of IL-1RA, IL-6, IL-8, IL-15, eotaxin, and monocyte chemotactic protein 1 were higher in deceased patients than in survivors (P < 0.05 for all), whereas IL-4 and IL-7 were lower (P < 0.05). After adjusting for the effects of age, % TBSA burn, and inhalation injury grade, plasma IL-1RA remained significantly associated with mortality (odds ratio, 3.12; 95% confidence interval, 1.03-9.44). Plasma IL-1RA also correlated with % TBSA burn, inhalation injury grade, fluid resuscitation, Baux score, revised Baux score, Denver score, and the Sequential Organ Failure Assessment score.

CONCLUSIONS

The severity of smoke inhalation injury has systemically reaching effects, which argue in favor of treating inhalation injury in a graded manner. In addition, several plasma immune mediators measured early after injury were associated with mortality. Of these, IL-1RA seemed to have the strongest correlation with injury severity and outcomes measures, which may explain the blunted pulmonary immune response we previously found in nonsurvivors.

Early pulmonary immune hyporesponsiveness is associated with mortality after burn and smoke inhalation injury

This prospective study aims to address mortality in the context of the early pulmonary immune response to burn and inhalation injury. The authors collected bronchoalveolar lavage fluid from 60 burn patients within 14 hours of their injury when smoke inhalation was suspected. Clinical and laboratory parameters and immune mediator profiles were compared with patient outcomes. Patients who succumbed to their injuries were older (P = .005), had a larger % TBSA burn (P < .001), and required greater 24-hour resuscitative fluids (P = .002). Nonsurvivors had lower bronchoalveolar lavage fluid concentrations of numerous immunomodulators, including C5a, interleukin (IL)-1β, IL-1RA, IL-8, IL-10, and IL-13 (P < .05 for all). Comparing only those with the highest Baux scores to account for the effects of age and % TBSA burn on mortality, nonsurvivors also had reduced levels of IL-2, IL-4, granulocyte colony-stimulating factor, interferon-γ, macrophage inflammatory protein-1β, and tumor necrosis factor-α (P < .05 for all). The apparent pulmonary immune hyporesponsiveness in those who died was confirmed by in vitro culture, which revealed that pulmonary leukocytes from nonsurvivors had a blunted production of numerous immune mediators. This study demonstrates that the early pulmonary immune response to burn and smoke inhalation may be attenuated in patients who succumb to their injuries.

Combined gene and stem cell therapy for cutaneous wound healing

In current medical practice, wound therapy remains a clinical challenge and much effort has been focused on the development of novel therapeutic approaches for wound treatment. Gene therapy, initially developed for treatment of congenital defects, represents a promising option for enhancing wound repair. In order to accelerate wound closure, genes encoding for growth factors or cytokines have shown the most potential. The majority of gene delivery systems are based on viral transfection, naked DNA application, high pressure injection, and liposomal vectors. Besides advances stemming from breakthroughs in recombinant growth factors and bioengineered skin, there has been a significant increase in the understanding of stem cell biology in the field of cutaneous wound healing. A variety of sources, such as bone marrow, umbilical cord blood, adipose tissue and skin/hair follicles, have been utilized to isolate stem cells and to modulate the healing response of acute and chronic wounds. Recent data have demonstrated the feasibility of autologous adult stem cell therapy in cutaneous repair and regeneration. Very recently, stem cell based skin engineering in conjunction with gene recombination, in which the stem cells act as both the seed cells and the vehicle for gene delivery to the wound site, represents the most attractive field for generating a regenerative strategy for wound therapy. The aim of this article is to discuss the use and the potential of these novel technologies in order to improve wound healing capacities.

Fms-like tyrosine kinase 3 ligand decreases T helper type 17 cells and suppressors of cytokine signaling proteins in the lung of house dust mite-sensitized and -challenged mice

We previously reported that Fms-like tyrosine kinase 3 ligand (Flt3-L) reversed airway hyperresponsiveness (AHR) and airway inflammation, and increased the number of regulatory CD11c(high)CD8α(high)CD11b(low) dendritic cells and CD4(+)CD25(+)ICOS(+)Foxp3(+)IL-10(+) T-regulatory cells in the lung of allergen-sensitized and -challenged mice. In this study, we evaluated the effect of Flt3-L on Th17 cells and expression of suppressors of cytokine signaling (SOCS) proteins in the lungs of house dust mite (HDM)-sensitized and -challenged mice. BALB/c mice were sensitized and challenged with HDM, and AHR to methacholine was established. Mice were treated with Flt3-L (5 μg, intraperitoneal) daily for 10 days. Levels of IL-4, -5, -6, -8, and -13, and transforming growth factor (TGF)-β in the bronchoalveolar lavage fluid (BALF) were examined by ELISA. Flt3-L treatment reversed existing AHR to methacholine and substantially decreased eosinophils, neutrophils, IL-5, -6, -8, and IL-13, and TGF-β levels in the BALF. HDM-sensitized and -challenged mice showed a significant increase in lung CD4(+)IL-17(+)IL-23R(+)CD25⁻ T cells with high expression of retinoic acid-related orphan receptor (ROR)-γt transcripts. However, administration of Flt3-L substantially decreased the number of lung CD4(+)IL-17(+)IL-23R(+)CD25⁻ T cells, with significantly decreased expression of ROR-γt mRNA in these cells. HDM sensitization caused a significant increase in the expression of SOCS-1, -3, and -5 in the lung. Flt3-L treatment abolished the increase in SOCS-1 and SOCS-3 proteins, whereas SOCS-5 expression was significantly reduced. These data suggest that the therapeutic effect of Flt3-L in reversing the hallmarks of allergic asthma in a mouse model is mediated by decreasing IL-6 and TGF-β levels in the BALF, which, in turn, decrease CD4(+)IL-17(+)IL-23R(+)ROR-γt(+)CD25⁻ T cells and the expression of SOCS-1 and SOCS-3 in the lung of HDM-sensitized and -challenged mice.

Stem cells for skin tissue engineering and wound healing

The tremendous ability of the skin's epidermis to regenerate is due to the presence of epidermal stem cells that continuously produce keratinocytes, which undergo terminal differentiation to a keratinized layer that provides the skin's barrier properties. The ability to control this process in vitro has made it possible to develop various types of tissue-engineered skin grafts, some of which are among the first tissue-engineered products to ever reach the market. In the past 30 years, these products have been applied with some success to the treatment of chronic skin wounds such as diabetic and venous ulcers and deep, acute wounds such as burns. Current technologies remain partially effective in their ability to restore other skin structures, for example, the dermis, which is critical to the overall long-term appearance and function of the skin. As yet, none of these approaches can regenerate skin appendages (e.g. hair follicles and sweat glands). The use of earlier progenitor and stem cells, including embryonic stem cells, is gaining interest in the attempt to overcome such limitations. Furthermore, recent evidence suggests that "adult" stem cells, which are present in the circulation, target areas of injury and likely participate in the wound-healing process. In this paper, we start with an overview of the wound-healing process and current methods used for wound treatment, both conventional and tissue-engineering based. We then review current research on the various types of stem cells used for skin tissue engineering and wound healing, and provide future directions.

A review of gene and stem cell therapy in cutaneous wound healing

Different therapies that effect wound repair have been proposed over the last few decades. This article reviews the emerging fields of gene and stem cell therapy in wound healing. Gene therapy, initially developed for treatment of congenital defects, is a new option for enhancing wound repair. In order to accelerate wound closure, genes encoding for growth factors or cytokines showed the greatest potential. The majority of gene delivery systems are based on viral transfection, naked DNA application, high pressure injection, or liposomal vectors. Embryonic and adult stem cells have a prolonged self-renewal capacity with the ability to differentiate into various tissue types. A variety of sources, such as bone marrow, peripheral blood, umbilical cord blood, adipose tissue, skin and hair follicles, have been utilized to isolate stem cells to accelerate the healing response of acute and chronic wounds. Recently, the combination of gene and stem cell therapy has emerged as a promising approach for treatment of chronic and acute wounds.

Stem cell strategies in burns care

The prospect of being able to replace damaged tissue by the process of regeneration would dramatically and irrevocably change the impact, management and outcome of burns. The current understanding of stem cell-based modulation and therapy together with their potential developments do bring this prospect ever closer to a clinical reality. This paper gives a background to stem cell strategies in burns care and identifies actual or prospective applications which, collectively, will forever change burns care throughout the world.

Enhancement of dendritic cell production by fms-like tyrosine kinase-3 ligand increases the resistance of mice to a burn wound infection

Fms-like tyrosine kinase-3 ligand (Flt3L) is a hemopoietic cytokine that stimulates the production of dendritic cells. This study evaluated the ability of Flt3L-enhanced dendritic cell production to increase the resistance of mice to a burn wound infection with Pseudomonas aeruginosa, a common source of infections in burn patients that have impaired immunity and are susceptible to opportunistic microorganisms. Treatment of mice with Flt3L for 5 days caused a significant increase in dendritic cell numbers in the spleen and significantly increased survival upon a subsequent burn wound infection. Improved survival in Flt3L-treated mice was associated with limited bacterial growth and spread within the burn wounds and a decrease in systemic dissemination of P. aeruginosa. Resistance to burn wound infection could also be conferred to recipient mice by the adoptive transfer of dendritic cells that had been isolated from spleens of Flt3L-treated mice. Adoptive transfer of the same number of splenic dendritic cells from nontreated mice did not confer resistance to burn wound infection. These data indicate that Flt3L can increase the resistance of mice to a P. aeruginosa burn wound infection through both stimulation of dendritic cell production and enhancement of dendritic cell function.

Stimulation of hematopoiesis by the Fms-like tyrosine kinase 3 ligand restores bacterial induction of Th1 cytokines in thermally injured mice

Patients with large burn injuries are susceptible to opportunistic infections due to impaired functions of multiple effector cells of innate immunity and acquired immunity, including macrophages, dendritic cells (DC), natural killer (NK) cells, and T cells. The ability of a host to produce Th1 cytokines, such as gamma interferon (IFN-gamma) and interleukin-12 (IL-12), upon infectious challenge is also impaired after burn injury. Stimulation of hematopoiesis, to regenerate new immune cells, may be an effective strategy for improving resistance to infections after severe burn trauma. Fms-like tyrosine kinase 3 ligand (Flt3L) is a hematopoietic cytokine that stimulates the expansion and differentiation of NK cells and DC. Using a mouse model, we tested the hypothesis that Flt3L treatments after burn injury stimulate the production of functional effector cells of innate immunity and restore appropriate Th1 cytokine responses to Pseudomonas aeruginosa, a common source of pneumonia and wound infections in burn victims. Flt3L increased splenic cellularity in sham (uninjured) and burned mice and increased the numbers of NK cells (DX5(+)) and DC (CD11c(+)). In response to P. aeruginosa, significant increases in the serum IFN-gamma levels and the numbers of splenic IFN-gamma-producing DC, NK cells, and T cells were observed in Flt3L-treated burned mice compared to the values obtained for untreated burned mice. The splenic levels of IL-12 and IL-15 mRNAs and the IL-12 and IL-15 receptors were also increased. In addition, Flt3L treatment restored the ability of splenic cultures prepared from burned mice to produce IFN-gamma and IL-12 after in vitro challenge with P. aeruginosa. Flt3L may have potential for restoring NK cell and DC functions and improving immunity after burn injury.

Age-associated loss of immunomodulatory protection by granulocyte-colony stimulating factor in endotoxic rats

Elderly patients have a higher incidence of morbidity and mortality due to infectious diseases. Because most immune functions in the elderly differ compared with those in younger subjects, we studied the effect of the immunomodulating agent G-CSF on endotoxic liver injury and cytokine release in an aging animal model of acute sepsis. Young (3-month-old), mature (12-month-old), and senescent (24-month-old) male Sprague-Dawley rats (n = 6 each) were treated with bacterial endotoxin for 6 h. Age-matched groups of animals (n = 6 each) received G-CSF (200 microg/kg i.v.) 1 h prior to endotoxin. LPS-induced hepatic toxicity, as assessed in vivo by nutritive perfusion failure, intravascular leukocyte accumulation, biliary excretion dysfunction, and liver enzyme release, was significantly more pronounced in mature and old animals when compared with young animals. Concomitantly, mature but, in particular, senescent endotoxic animals exhibited 2- to 14-fold higher plasma levels of TNF-alpha, IL-1beta, IL-6, IL-10, and Rantes than young endotoxic rats. The percentage of G-CSF receptor surface expression on neutrophils did not significantly differ between young, mature, and senescent animals (36%-46%) and was found comparably down-regulated at 6 h after LPS exposure (15%-19%). Kupffer cell activation, i.e., clearance of intravascularly applied fluorescent latex beads, did not differ between the LPS-exposed age groups. G-CSF dampened LPS-induced Kupffer cell activation, and significantly reduced plasma cytokine levels in young and mature, but not in senescent animals. Thereby, G-CSF caused attenuation of hepatic tissue injury in all except the senescent endotoxic animals. In summary, our results show an age-dependent increase in hepatic LPS toxicity. Because flow cytometric analysis of G-CSF receptor expression disproved that cytokinemia-induced down-regulation of G-CSF receptors might account for the unresponsiveness to G-CSF in the senescent animals, other homeostatic regulatory mechanisms appear to undergo changes with age that bring out a disrupted balance between inflammatory cytokines with unresponsiveness to G-CSF and, thus, compromised host defense mechanisms in the elderly.

Granulocyte colony-stimulating factor: release is not impaired after burn wound infection

BACKGROUND

The production of granulocyte colony-stimulating factor (G-CSF), the lineage specific essential regulator of neutrophil progenitor cell proliferation and differentiation, has been thought to be impaired in the setting of burn infection. The ability to directly measure murine G-CSF allows the further delineation of the G-CSF response in a clinically relevant model of thermal injury and infection.

METHODS

We used a commercially available solid phase enzyme-linked immunoabsorbent assay to quantify G-CSF production after burn wound infection in mice. Bone marrow cells, splenic cells, and serum were obtained from BDF1 mice on day 3 after a 15% total body surface area full-thickness scald burn with or without Pseudomonas aeruginosa burn wound infection. G-CSF production of bone marrow cells or splenic cells and the serum level of G-CSF were measured. A clonogenic assay of bone marrow and spleen granulocyte-macrophage progenitor cells as well as blood leukocyte counts were also performed.

RESULTS

After burn sepsis, we noted that G-CSF production of the bone marrow and spleen was significantly increased; the numbers of progenitor cells in bone marrow and spleen were markedly enhanced; serum values of G-CSF were 14 times greater than control values; serum colony-stimulating activity was greater than in control mice; and total blood leukocyte counts were significantly depressed.

CONCLUSION

These findings support the notion that granulocytopoietic failure after burn sepsis is not significantly related to defective endogenous G-CSF synthesis. More likely, hyporesponsiveness of granulocyte progenitor cells to G-CSF, changes in the relative balance of granulocyte versus monocyte progenitors within the granulocyte-macrophage progenitor cell compartment, and enhanced release of monocyte lineage specific growth factors are the critical elements responsible for burn infection-induced hematopoietic failure.

The relationship between tumor necrosis factor (TNF)-alpha and survival following granulocyte-colony stimulating factor (G-CSF) administration in burn sepsis

Blood levels of tumor necrosis factor (TNF)-alpha were determined in 78 patients with burn sepsis. Of these patients, 51 were managed with additional administration of granulocyte colony-stimulating factor (G-CSF) in addition to routine treatment procedures (group A), while 27 received only routine treatment (group B). G-CSF was administrated for at least nine and at most 14 days; doses were gradually decreased in each 3 day period. On the 1st, 4th, 7th, 10th and 15th days, blood levels of TNF-alpha were determined. We sought to determine whether TNF alpha levels had a prognostic value in the management of burn induced sepsis that was treated with G-CSF. In our study, patients with gradually decreasing TNF-alpha levels in the second 3 day period, were strong candidates for survival, because TNF-alpha levels decreased little in nonsurvivors but decreased greatly in survivors. The survival rate was 42/51 (82.3%) in group A and 9/27 (33.3%) in group B. In conclusion, G-CSF had positive effects on survival, and TNF-alpha was a predictor of prognosis in burn-induced sepsis.

Recombinant human granulocyte colony-stimulating factor attenuates inflammatory responses in septic patients with neutropenia

OBJECTIVE

The objective of this study was to determine the effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) administration in septic patients with neutropenia.

METHODS

Twenty consecutive septic patients were administered rhG-CSF subcutaneously (2 microg x kg(-1) x d(-1)) for 5 days (group G). They were compared with 14 septic patients treated earlier without rhG-CSF (group N). All patients in both groups met the criteria of total leukocyte count (TLC) less than 5,000/mm3 and C-reactive protein (CRP) more than 10 mg/dL. Changes in TLC, absolute neutrophil count (ANC), CRP, respiratory index (RI), Acute Physiology and Chronic Health Evaluation (APACHE) II score, and Goris's Multiple Organ Failure (MOF) index were evaluated. In addition, nucleated cell count (NCC), differentiation in bone marrow aspiration, neutrophil phagocytic and bactericidal activity, serum concentrations of interleukin-6 (IL-6) and IL-8 as inflammatory markers, and plasma concentration of leukocyte elastase (LE) as an indicator of the tissue injury were evaluated in group G.

RESULTS

In group G, TLC, ANC, NCC, and neutrophil functions increased significantly, whereas CRP, IL-6, and IL-8 decreased reciprocally. There was no deterioration of LE and RI. Consequently, the APACHE II score and MOF index improved. In group N, however, CRP showed no change concomitant with the APACHE II score and MOF index.

CONCLUSION

Administration of rhG-CSF attenuates inflammatory responses without inducing tissue injury in septic patients with neutropenia.