Cytokine productive capacity of alveolar macrophages and Kupffer cells after femoral fracture and blunt chest trauma in a murine trauma model

Polytrauma impairs fracture healing accompanied by increased persistence of innate inflammatory stimuli and reduced adaptive response

The field of bone regeneration has primarily focused on investigating fracture healing and nonunion in isolated musculoskeletal injuries. Compared to isolated fractures, which frequently heal well, fractures in patients with multiple bodily injuries (polytrauma) may exhibit impaired healing. While some papers have reported the overall cytokine response to polytrauma conditions, significant gaps in our understanding remain in how fractures heal differently in polytrauma patients. We aimed to characterize fracture healing and the temporal local and systemic immune responses to polytrauma in a murine model of polytrauma composed of a femur fracture combined with isolated chest trauma. We collected serum, bone marrow from the uninjured limb, femur fracture tissue, and lung tissue over 3 weeks to study the local and systemic immune responses and cytokine expression after injury. Immune cell distribution was assessed by flow cytometry. Fracture healing was characterized using microcomputed tomography (microCT), histological staining, immunohistochemistry, mechanical testing, and small angle X-ray scattering. We detected more innate immune cells in the polytrauma group, both locally at the fracture site and systemically, compared to other groups. The percentage of B and T cells was dramatically reduced in the polytrauma group 6 h after injury and remained low throughout the study duration. Fracture healing in the polytrauma group was impaired, evidenced by the formation of a poorly mineralized and dysregulated fracture callus. Our data confirm the early, dysregulated inflammatory state in polytrauma that correlates with disorganized and impaired fracture healing.

Experimental study of a novel mouse model of tibial shaft fracture combined with blunt chest trauma

BACKGROUD

Thoracic Trauma and Limb Fractures Are the Two most Common Injuries in Multiple Trauma. However, there Is Still a Lack of Mouse Models of Trauma Combining Tibial Shaft Fracture (TSF) and Thoracic Trauma. In this Study, we Attempted to Develop a Novel Mouse Model of TSF Combined with Blunt Chest Trauma (BCT).

METHODS

A total of 84 C57BL/6J male mice were used as the multiple trauma model. BCT was induced by hitting the chests of mice with heavy objects, and TSF was induced by hitting the tibia of mice with heavy objects after intramedullary fixation. Serum specimens of mice were received by cardiac puncture at defined time points of 0, 6, 12, 24, 48, and 72 h.

RESULTS

Body weight and body temperature tended to decrease within 24 h after multiple trauma. Hemoglobin analyses revealed a decrease during the first 24 h after multiple trauma. Some animals died by cardiac puncture immediately after chest trauma. These animals exhibited the most severe pulmonary contusion and hemorrhage. The level of lung damage varied in diverse mice but was apparent in all animals. Classic hematoxylin and eosin (H&E)-stained paraffin pulmonary sections of mice with multiple trauma displayed hemorrhage and an immunoinflammatory reaction. Bronchoalveolar lavage fluid (BALF) and serum samples of mice with multiple trauma showed an upregulation of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-1α (TNF-1α) compared with the control group. Microimaging confirmed the presence of a tibia fracture and pulmonary contusion.

CONCLUSIONS

The novel mouse multiple trauma model established in this study is a common trauma model that shows similar pathological mechanisms and imaging characteristics in patients with multiple injuries. This study is useful for determining whether blockade or intervention of the cytokine response is beneficial for the treatment of patients with multiple trauma. Further research is needed in the future.

Effect of Targeted Cytokine Inhibition on Progression of Post-Traumatic Osteoarthritis Following Intra-Articular Fracture

Intra-articular fractures (IAF) result in significant and prolonged inflammation, increasing the chances of developing post-traumatic osteoarthritis (PTOA). Interleukin-one beta (IL-1β) and Tumor Necrosis Factor-alpha (TNF-α) are key inflammatory factors shown to be involved in osteochondral degradation following IAF. As such, use of targeted biologics such as Infliximab (INX), a TNF-α inhibitor, and Anakinra (ANR), an interleukin-one (IL-1) receptor antagonist (IL1RA), may protect against PTOA by damping the inflammatory response to IAF and reducing osteochondral degradation. To test this hypothesis, IAFs were induced in the hindlimb knee joints of rats treated with INX at 10 mg/kg/day, ANR at 100 g/kg/day, or saline (vehicle control) by subcutaneous infusion for a period of two weeks and healing was evaluated at 8-weeks post injury. Serum and synovial fluid (SF) were analyzed for soluble factors. In-vivo microcomputed tomography (µCT) scans assessed bone mineral density and bone morphometry measurements. Cationic CA4+ agent assessed articular cartilage composition via ex vivo µCT. Scoring according to the Osteoarthritis Research Society International (OARSI) guidelines was performed on stained histologic tibia sections at the 56-day endpoint on a 0-6 scale. Systemically, ANR reduced many pro-inflammatory cytokines and reduced osteochondral degradation markers Cross Linked C-Telopeptide Of Type II (CTXII, p < 0.05) and tartrate-resistant acid phosphatase (TRAP, p < 0.05). ANR treatment resulted in increased chemokines; macrophage-chemotractant protein-1 (MCP-1), MPC-3, macrophage inhibitory protein 2 (MIP2) with a concomitant decrease in proinflammatory interleukin-17A (IL17A) at 14 days post-injury within the SF. Microcomputed tomography (µCT) at 56 days post-injury revealed ANR Treatment decreased epiphyseal degree of anisotropy (DA) (p < 0.05) relative to saline. No differences were found with OARSI scoring but contrast-enhanced µCT revealed a reduction in glycosaminoglycan content with ANR treatment. These findings suggest targeted cytokine inhibition, specifically IL-1 signaling, as a monotherapy has minimal utility for improving IAF healing outcomes but may have utility for promoting a more permissive inflammatory environment that would allow more potent disease modifying osteoarthritis drugs to mitigate the progression of PTOA after IAF.

Selective Inhibition of IL-6 Trans-Signaling Has No Beneficial Effect on the Posttraumatic Cytokine Release after Multiple Trauma in Mice

While improvements in pre-hospital and in-hospital care allow more multiple trauma patients to advance to intensive care, the incidence of posttraumatic multiple organ dysfunction syndrome (MODS) is on the rise. Herein, the influence of a selective IL-6 trans-signaling inhibition on posttraumatic cytokine levels was investigated as an approach to prevent MODS caused by a dysbalanced posttraumatic immune reaction. Therefore, the artificial IL-6 trans-signaling inhibitor sgp130Fc was deployed in a murine multiple trauma model (femoral fracture plus bilateral chest trauma). The traumatized mice were treated with sgp130Fc (FP) and compared to untreated mice (WT) and IL-6 receptor knockout mice (RKO), which received the same traumas. The overall trauma mortality was 4.4%. Microscopic pulmonary changes were apparent after multiple trauma and after isolated bilateral chest trauma. Elevated IL-6, MCP-3 and RANTES plasma levels were measured after trauma, indicating a successful induction of a systemic inflammatory reaction. Significantly reduced IL-6 and RANTES plasma levels were visible in RKO compared to WT. Only a little effect was visible in FP compared to WT. Comparable cytokine levels in WT and FP indicate neither a protective nor an adverse effect of sgp130Fc on the cytokine release after femoral fracture and bilateral chest trauma.

Experimental induction of blunt chest trauma in mice: A modified approach with evaluation in dummies and cadavers

Experimental chest trauma or blunt thoracic trauma using a blast wave mechanism is well established in animal models. The aim of the present study was to establish a complementary, murine experimental chest trauma model precisely defined by physical data and calculations. For this purpose, a device was developed using a dropped weight and physical properties, including velocity, energy and impact, were calculated. The device allowed for the maximum depth of impression to be measured. The device was first tested using blocks of modelling clay and was then applied to mouse cadavers. X-ray and dissection were performed to check for bone fractures and organ injuries following blunt chest traumas of increasing impact. Lesions and hemorrhages were observed in mouse cadavers which sustained a force equivalent to the energy of ~1 J.

Contributing factors in the development of acute lung injury in a murine double hit model

OBJECTIVES

Blunt chest (thoracic) trauma (TxT) is known to contribute to the development of secondary pulmonary complications. Of these, acute lung injury (ALI) is common especially in multiply injured patients and might not only be due to the direct trauma itself, but seems to be caused by ongoing and multifactorial inflammatory changes. Nevertheless, the exact mechanisms and contributing factors of the development of ALI following blunt chest trauma are still elusive.

METHODS

60 CL57BL/6N mice sustained either blunt chest trauma combined with laparotomy without further interventions or a double hit (DH) including TxT and cecal ligation puncture (CLP) after 24 h to induce ALI. Animals were killed either 6 or 24 h after the second procedure. Pulmonary expression of inflammatory mediators cxcl1, cxcl5, IL-1β and IL-6, neutrophil infiltration and lung tissue damage using the Lung Injury Score (LIS) were determined.

RESULTS

Next to a moderate increase in other inflammatory mediators, a significant increase in CXCL1, neutrophil infiltration and lung injury was observed early after TxT, which returned to baseline levels after 24 h. DH induced significantly increased gene expression of cxcl1, cxcl5, IL-1β and IL-6 after 6 h, which was followed by the postponed significant increase in the protein expression after 24 h compared to controls. Neutrophil infiltration was significantly enhanced 24 h after DH compared to all other groups, and exerted a slight decline after 24 h. LIS has shown a significant increase after both 6 and 24 h compared to both control groups as well the late TxT group.

CONCLUSION

Early observed lung injury with moderate inflammatory changes after blunt chest trauma recovered quickly, and therefore, may be caused by mechanical lung injury. In contrast, lung injury in the ALI group did not undergo recovery and is closely associated with significant changes of inflammatory mediators. This model may be used for further examinations of contributing factors and therapeutic strategies to prevent ALI.

Comparative Analysis of the Regulatory T Cells Dynamics in Peripheral Blood in Human and Porcine Polytrauma

Background

Severely injured patients experience substantial immunological stress in the aftermath of traumatic insult, which often results in systemic immune dysregulation. Regulatory T cells (Treg) play a key role in the suppression of the immune response and in the maintenance of immunological homeostasis. Little is known about their presence and dynamics in blood after trauma, and nothing is known about Treg in the porcine polytrauma model. Here, we assessed different subsets of Treg in trauma patients (TP) and compared those to either healthy volunteers (HV) or data from porcine polytrauma.

Methods

Peripheral blood was withdrawn from 20 TP with injury severity score (ISS) ≥16 at the admittance to the emergency department (ED), and subsequently on day 1 and at day 3. Ten HV were included as controls (ctrl). The porcine polytrauma model consisted of a femur fracture, liver laceration, lung contusion, and hemorrhagic shock resulting in an ISS of 27. After polytrauma, the animals underwent resuscitation and surgical fracture fixation. Blood samples were withdrawn before and immediately after trauma, 24 and 72 h later. Different subsets of Treg, CD4+CD25+, CD4+CD25+FoxP3+, CD4+CD25+CD127-, and CD4+CD25+CD127-FoxP3+ were characterized by flow cytometry.

Results

Absolute cell counts of leukocytes were significantly increasing after trauma, and again decreasing in the follow-up in human and porcine samples. The proportion of human Treg in the peripheral blood of TP admitted to the ED was lower when compared to HV. Their numbers did not recover until 72 h after trauma. Comparable data were found for all subsets. The situation in the porcine trauma model was comparable with the clinical data. In porcine peripheral blood before trauma, we could identify Treg with the typical immunophenotype (CD4+CD25+CD127-), which were virtually absent immediately after trauma. Similar to the human situation, most of these cells expressed FoxP3, as assessed by intracellular FACS stain.

Conclusion

Despite minor percental differences in the recovery of Treg populations after trauma, our findings show a comparable decrease of Treg early after polytrauma, and strengthen the immunological significance of the porcine polytrauma model. Furthermore, the Treg subpopulation CD4+CD25+CD127- was characterized in porcine samples.

A new multiple trauma model of the mouse

Background

Blunt trauma is the most frequent mechanism of injury in multiple trauma, commonly resulting from road traffic collisions or falls. Two of the most frequent injuries in patients with multiple trauma are chest trauma and extremity fracture. Several trauma mouse models combine chest trauma and head injury, but no trauma mouse model to date includes the combination of long bone fractures and chest trauma. Outcome is essentially determined by the combination of these injuries. In this study, we attempted to establish a reproducible novel multiple trauma model in mice that combines blunt trauma, major injuries and simple practicability.

Methods

Ninety-six male C57BL/6 N mice (n = 8/group) were subjected to trauma for isolated femur fracture and a combination of femur fracture and chest injury. Serum samples of mice were obtained by heart puncture at defined time points of 0 h (hour), 6 h, 12 h, 24 h, 3 d (days), and 7 d.

Results

A tendency toward reduced weight and temperature was observed at 24 h after chest trauma and femur fracture. Blood analyses revealed a decrease in hemoglobin during the first 24 h after trauma. Some animals were killed by heart puncture immediately after chest contusion; these animals showed the most severe lung contusion and hemorrhage. The extent of structural lung injury varied in different mice but was evident in all animals. Representative H&E-stained (Haematoxylin and Eosin-stained) paraffin lung sections of mice with multiple trauma revealed hemorrhage and an inflammatory immune response. Plasma samples of mice with chest trauma and femur fracture showed an up-regulation of IL-1β (Interleukin-1β), IL-6, IL-10, IL-12p70 and TNF-α (Tumor necrosis factor- α) compared with the control group. Mice with femur fracture and chest trauma showed a significant up-regulation of IL-6 compared to group with isolated femur fracture.

Conclusions

The multiple trauma mouse model comprising chest trauma and femur fracture enables many analogies to clinical cases of multiple trauma in humans and demonstrates associated characteristic clinical and pathophysiological changes. This model is easy to perform, is economical and can be used for further research examining specific immunological questions.

CD43Lo classical monocytes participate in the cellular immune response to isolated primary blast lung injury

BACKGROUND

Understanding of the cellular immune response to primary blast lung injury (PBLI) is limited, with only the neutrophil response well documented. Moreover, its impact on the immune response in distal organs remains poorly understood. In this study, a rodent model of isolated primary blast injury was used to investigate the acute cellular immune response to isolated PBLI in the circulation and lung, including the monocyte response, and investigate distal subacute immune effects in the spleen and liver 6 hours after injury.

METHODS

Rats were subjected to a shock wave (~135 kPa overpressure, 2 ms duration) inducing PBLI or sham procedure. Rat physiology was monitored, and at 1, 3, and 6 hours thereafter, blood, lung, and bronchoalveolar lavage fluid (BALF) were collected and analyzed by flow cytometry, enzyme-linked immunosorbent assay, and histologic examination. In addition, at 6 hours, spleen and liver were collected and analyzed by flow cytometry.

RESULTS

Lung histology confirmed pulmonary barotrauma and inflammation. This was associated with rises in CXCL-1, interleukin 6 (IL-6), tumor necrosis factor α and albumin protein in the BALF. Significant acute increases in blood and lung neutrophils and CD43Lo/His48Hi (classical) monocytes/macrophages were detected. No significant changes were seen in blood or lung "nonclassical" monocyte and in natural killler, B, or T cells. In the BALF, significant increases were seen in neutrophils, CD43Lo monocyte-macrophages and monocyte chemoattractant protein-1. Significant increases in CD43Lo and Hi monocyte-macrophages were detected in the spleen at 6 hours.

CONCLUSION

This study reveals a robust and selective response of CD43Lo/His48Hi (classical) monocytes, in addition to neutrophils, in blood and lung tissue following PBLI. An increase in monocyte-macrophages was also observed in the spleen at 6 hours. This profile of immune cells in the blood and BALF could present a new research tool for translational studies seeking to monitor, assess, or attenuate the immune response in blast-injured patients.

Hepatocytes express the antimicrobial peptide HBD-2 after multiple trauma: an experimental study in human and mice

Background

Human-beta defensins (HBD) belong to the family of acute phase peptides and hold a broad antimicrobial spectrum that includes gram-positive and gram-negative bacteria. HBD are up-regulated after severe injuries but the source of posttraumatic HBD expression has not been focused on before.

In the current study we analysed the role of liver tissue in expression of HBD after multiple trauma in human and mice.

Methods

HBD-2 expression has been detected in plasma samples of 32 multiple trauma patients (ISS > 16) over 14 days after trauma by ELISA. To investigate major sources of HBD-2, its expression and regulation in plasma samples, polymorphonuclear neutrophils (PMN) and human tissue samples of liver and skin were analysed by ELISA. As liver samples of trauma patients are hard to obtain we tried to review findings in an established trauma model. Plasma samples and liver samples of 56 male C57BL/6 N-mice with a thorax trauma and a femur fracture were analysed by ELISA, real-time PCR and immunohistochemistry for murine beta defensin 4 (MBD-4) and compared with the expression of control group without trauma.

The induction of HBD-2 expression in cultured hepatocytes (Hep G2) was analysed after incubation with IL-6, supernatant of Staphylococcus aureus (SA) and Lipopolysaccharides (LPS). One possible signalling pathway was tested by blocking toll-like receptor 2 (TLR2) in hepatocytes.

Results

Compared to healthy control group, plasma of multiple traumatized patients and mice showed significantly higher defensin levels after trauma. Compared to skin cells, which are known for high beta defensin expression, liver tissue showed less HBD-2 expression, but higher HBD-2 expression compared to PMN. Immunhistochemical staining demonstrated upregulated MBD-4 in hepatocytes of traumatised mice. In HepG2 cells HBD-2 expression could be increased by stimulation with IL-6 and SA. Neutralization of HepG2 cells with αTLR2 showed reduced HBD-2 expression after stimulation with SA.

Conclusion

Plasma samples of multiple traumatized patients showed high expression of HBD-2, which may protect the severely injured patient from overwhelming bacterial infection. Our data support the hypothesis that liver is one possible source for HBD-2 in plasma while posttraumatic inflammatory response.

Potential Role of Chemokines in Fracture Repair

Chemokines are a family of small cytokines that share a typical key structure that is stabilized by disulfide bonds between the cysteine residues at the NH₂-terminal of the protein, and they are secreted by a great variety of cells in several different conditions. Their function is directly dependent on their interactions with their receptors. Chemokines are involved in cell maturation and differentiation, infection, autoimmunity, cancer, and, in general, in any situation where immune components are involved. However, their role in postfracture inflammation and fracture healing is not yet well established. In this article, we will discuss the response of chemokines to bone fracture and their potential roles in postfracture inflammation and healing based on data from our studies and from other previously published studies.

Repetitive reduction lead to significant elevated IL-6 and decreased IL-10 levels in femoral osteotomies: A quantitative analysis of a robot-assisted reduction process in a rat model

INTRODUCTION

The field of robot-assisted fracture reduction has been developed by several research groups over more than one decade by now, with the main goals of increasing the fracture reduction accuracy. However, the influence of different reduction paths to patients' physiology is not fully known yet. The aim of our study was to compare the impacts of a robot-assisted direct reduction path versus an artificially prolonged reduction path by measuring the cytokine responses in an in vivo rat model.

MATERIALS AND METHODS

Thirty-six male CD(©) rats were assigned into three groups with an external fixator and osteotomy on the left femur. Seven days later, the robot was attached and one group was reduced in a single attempt, while the other group underwent 10 attempts by the robot. The third group was the control group without reduction. Before, and as well as 6, 24 and 48h after the reduction process blood samples were collected. IL-1, IL-6, IL-10, IL-17, and MCP-1 concentrations where analysed via ELISA or cytometric bead assay. Muscle biopsies in the osteotomy area were collected 48h after the reduction process for histological analyses. Statistical significance was set at p≤0.05.

RESULTS

Analysis of the cytokines showed that the pro-inflammatory cytokine IL-6 of the Ten-Attempts reduction group significantly increased 6h after reduction compared to the control group. IL-6 further showed markedly elevated levels 6h after surgery in the Ten-Attempts reduction group compared to the Single-Attempt reduction group. On the anti-inflammatory side, IL-10 showed a significant decrease in the Ten-Attempts reduction group 6h after reduction compared to the Single-Attempt reduction and control group. Muscle biopsies showed a significant increase of pathological changes in both reduction groups and an increase in the severity of bleedings of the Ten-Attempts reduction group compared to the Single-Attempt reduction and control group.

CONCLUSION

A direct and gentle reduction procedure as feasible by the aid of a robot is preferable over a prolonged reduction in terms of cytokine response and tissue changes.

Identification of potential biomarkers for post-traumatic complications released after trauma-hemorrhage from murine Kupffer cells and its investigation in lung and liver

CONTEXT

Early diagnosis of complications after severe trauma by specific biomarkers remains difficult.

OBJECTIVE

Identify potential new biomarkers for early diagnosis of post-traumatic complications.

MATERIAL AND METHODS

Mice underwent pressure-controlled hemorrhage or sham procedure. Four hours later, genome-wide expression of isolated Kupffer cells was compared with controls using Affymetrix-Genechip-Expression-Analysis and real-time-PCR.

RESULTS

Expression analysis and real-time-PCR revealed a significant increase of gene expression of Cxcl10, Il4ra, Csf2rb2, Lcn2, and Gbp5.

CONCLUSION

Cxcl10, Il4ra, Csf2rb2, Lcn2, and Gbp5 might represent new biomarkers for early diagnosis of post-traumatic complications, if they are linked to the development of post-traumatic complications.

Video-assisted thoracoscopic surgery for retained hemothorax in blunt chest trauma

Purpose of review

In the last decade, video-assisted thoracoscopic surgery (VATS) has become a popular method in diagnosis and treatment of acute chest injuries. Except for patients with unstable vital signs who require larger surgical incisions to check bleeding, this endoscopic surgery could be employed in the majority of thoracic injury patients with stable vital signs.

Recent findings

In the past, VATS was used to evacuate traumatic-retained hemothorax. Recent study has revealed further that lung repair during VATS could decrease complications after trauma. Management of fractured ribs could also be assisted by VATS. Early VATS intervention within 7 days after injury can decrease the rate of posttraumatic infection and length of hospital stay. In studies of the pathophysiology of animal models, N-acetylcysteine and methylene blue were used in animals with blunt chest trauma and found to improve clinical outcomes.

Summary

Retained hemothorax derived from blunt chest trauma should be managed carefully and rapidly. Early VATS intervention is a well tolerated and reliable procedure that can be applied to manage this complication cost effectively.

Activation of markers of inflammation, coagulation and fibrinolysis in musculoskeletal trauma

Background

Traumatic injury induces changes in mediators of inflammation and coagulation, but the pivotal roles of inflammation and coagulation has not been precisely clarified. Therefore we have studied markers of inflammation and coagulation after a standardized musculoskeletal trauma like total hip replacement surgery.

Methods

We allocated 21 patients aged 50 to 84 years who underwent total hip replacement surgery. Releases of TNF-α, IL-1β, IL-6, IL-8 and IL-10 and protrombin fragment F1.2 and plasmin-antiplasmin complex (PAP) were examined during surgery and up 6 days postoperatively, and systemic releases were compared to pre-operative values. Surgery induced significant increments in serum levels of IL-6 at 6 hours and at 1 day after surgery and in levels of IL-8 at 6 hours after surgery. There were no significant changes in serum levels of TNF-α, IL-1β or IL-10. There were significant increments in blood levels of F1.2 and PAP up to 6 days postoperatively with highest levels at 6 hours after surgery. There were only week correlations between IL-6 and IL-8 and F1.2 and PAP.

Conclusion

Major musculoskeletal surgery causes changes of the inflammatory, coagulatory and fibrinolytic cascades in stable patients, but with no correlations between inflammation and coagulation and fibrinolysis.

Is boosting the immune system in sepsis appropriate?

A relative immunosuppression is observed in patients after sepsis, trauma, burns, or any severe insults. It is currently proposed that selected patients will benefit from treatment aimed at boosting their immune systems. However, the host immune response needs to be considered in context with pathogen-type, timing, and mainly tissue specificity. Indeed, the immune status of leukocytes is not universally decreased and their activated status in tissues contributes to organ failure. Accordingly, any new immune-stimulatory therapeutic intervention should take into consideration potentially deleterious effects in some situations.