Selective cyclooxygenase-2 inhibition reverses microcirculatory and inflammatory sequelae of closed soft-tissue trauma in an animal model

Mesenchymal stem cells derived-exosomes as a new therapeutic strategy for acute soft tissue injury

The study aimed to investigate the role of exosomes derived from rat bone marrow mesenchymal stem cells (rBMSCs) in acute soft tissue injury and its related mechanisms. Exosomes were isolated from rBMSCs and characterized by Nanosight NS300 particle size analyser (NTA), transmission electron microscopy (TEM), and western blot. Twenty four rats were randomly divided into four groups (n = 6): control group, strike group, rBMSCs group, and rBMSCs-exo group. Haematoxylin-eosin (HE) staining was used to observe the morphology. Real-time quantification PCR (RT-qPCR) and western blot were used to analyse the expression of IL-1A, IL-12A, COL11A1, COL4A4, and Wnt4. NTA, TEM and western blot results showed that exosomes isolated from rBMSCs were cup-shaped morphology with a size of about 100 nm. HE staining showed that there was severe soft tissue inflammation in strike group, and the symptoms were alleviated after rBMSCs and rBMSCs-exo treatment. RT-qPCR and western blot indicated that in the strike group, the expression levels of IL-1A and IL-12A were significantly increased, and their expressions were decreased markedly by exosomes treatment. In addition, after treatment, the expression levels of COL11A1 and Wnt4 were up-regulated, while the expression of COL4A4 was down-regulated. Exosomes isolated from rBMSCs could improve acute soft tissue injury, and may be used as a new therapeutic strategy acute soft tissue injury. SIGNIFICANCE OF THE STUDY: Acute soft tissue injury is a common clinical exercise injury, which has a significant impact on people's health and work ability. Exosomes have been attracting increasing attention as a media of cell-to-cell communication. This study showed that exosomes isolated from rBMSCs could improve acute soft tissue injury by inhibiting inflammatory response, regulating the levels of COL11A1 and COL4A4, and up-regulating the expression of Wnt4. These will provide a new therapy strategy of acute soft tissue injury, and improve our understanding of the occurrence and development in acute soft tissue injury.

Oral cyclo-oxygenase 2 inhibitors versus other oral analgesics for acute soft tissue injury: systematic review and meta-analysis

BACKGROUND

Acute soft tissue injuries are common and carry significant societal costs. Cyclo-oxygenase 2 (COX-2) inhibitors (coxibs), non-selective nonsteroidal anti-inflammatory drugs (NSAIDs) and other analgesics are used to treat acute soft tissue injuries, with ongoing debate about their analgesic efficacy, effects on tissue healing and adverse effects (AEs).

OBJECTIVES

To systematically review the evidence comparing oral coxibs with other oral analgesics for acute soft tissue injuries, using the outcomes: pain, swelling, function and AEs.

METHODS

The following databases were searched: MEDLINE, EMBASE, Cochrane CENTRAL, CINAHL, AMED, PEDro and SPORTDiscus. Further studies were sought through clinical trials registries, dissertations, correspondence with pharmaceutical companies and manual searches of relevant journals. There was no language restriction.

DEFINITIONS

'Coxibs' were defined as drugs that inhibit COX-2 >5-fold more than COX-1; 'acute' was defined as injury occurring within 48 hours of enrollment; 'soft tissue injury' was defined as closed injuries to upper or lower limb soft tissues (ligaments, muscles or tendons).

STUDY SELECTION

Randomized controlled trials in humans comparing a coxib to a different class of oral analgesic agent for the treatment of acute soft tissue injuries for <30 days, and in which >or=80% of participants met the definition of acute soft tissue injury, were included. Studies were excluded if >20% of participants enrolled had back pain, cervical spine injury, repetitive strain injuries, delayed-onset muscle soreness, fractures, cartilage injury, penetrating wounds or primary inflammatory conditions (tendonitis, bursitis and arthritis). Nine out of 23 (39.1%) potentially relevant studies met the selection criteria.

DATA EXTRACTION

A standard form was used to extract data. Included studies were screened by the authors for risk of bias using the Cochrane risk of bias tool and evidence was graded for quality using the GRADE tool.

DATA SYNTHESIS

Clinical heterogeneity was minimized by application of strict selection criteria. Statistical heterogeneity was assessed using the I2 statistic and meta-analysis was undertaken if appropriate. Weighted mean difference (WMD) was used to assess pain, relative risk (RR) to assess AEs, and Peto odds ratio (OR) to assess return to function.

RESULTS

The nine RCTs evaluated in the meta-analysis included 3060 patients. Coxibs were found to be equal to NSAIDs (day 7+, n = 1884, 100 mm visual analogue scale [VAS]), WMD = 0.18 mm (95% CI -1.76, 2.13), p = 0.85 and tramadol (day 7+, n = 706, 100 mm VAS), WMD = -6.6 mm (95% CI -9.63, -3.47) [single study, difference clinically insignificant] for treating pain after soft tissue injuries. Coxibs had fewer gastrointestinal AEs than NSAIDs, even with short-term use (RR 0.59 [95% CI 0.41, 0.85], p = 0.004) [low quality evidence]. Swelling was measured in two studies with no difference being found between groups, but the presentation of the data was not sufficient to allow further analysis. Coxibs were found to be unlikely to be different to NSAIDs in helping patients return to function (OR 1.0 [95% CI 0.77, 1.3], p = 0.99); however, a single study suggested they may improve time to return to function (moderate quality evidence) and may have fewer AEs than tramadol (very low quality evidence). The risk of serious AEs with both coxibs and NSAIDs in this setting was low (but incompletely defined).

CONCLUSIONS

More studies comparing coxibs with NSAIDs and other analgesics in the setting of acute soft tissue injuries are necessary. A different review methodology would be required to answer the question of cardiovascular risk associated with short-term use of coxibs and NSAIDs.

Microcirculatory sequelae of the rotator cuff after antegrade nailing in proximal humerus fracture

INTRODUCTION

Antegrade nailing allows a stable fixation and, thus, an early functional after treatment in proximal humerus fractures. Since the surgical procedure in antegrade humeral nailing requires a split of the supraspinatus tendon, the question arises whether the surgical approach causes microcirculatory dysfunction of the tendon.

MATERIALS AND METHODS

A total of 15 consecutive patients suffering from proximal humerus fractures were enrolled. During the implantation of an antegrade humerus nail, microvascular perfusion of the supraspinatus tendon was directly visualized after the exposition and stabilization of the fracture using the OPS-imaging technique.

RESULTS

Immediately after exposure, the nutritive perfusion showed physiological values of tendon microcirculation. After implanting antegrade humeral nails, the perfusion of the supraspinatus tendon reduced markedly. Capillary width was unaffected by the surgical procedure.

CONCLUSION

The trauma leading to proximal humerus fracture causes no fundamental impairment of nutritive perfusion of the rotator cuff. Whereas the implantation of an antegrade humerus nail, which necessarily includes a splitting of the rotator cuff, nearly halves the functional capillary density of the supraspinatus tendon. Even though this effect seems to be reversible, the surgical dissection of the supraspinatus tendon should be performed in a soft tissue sparing way.

Cyclooxygenase-2 inhibitor celecoxib in a rat model of hindlimb ischemia reperfusion

Acute ischemia–reperfusion (IR) of the limbs initiates both local and systemic injuries by triggering a systemic inflammatory response. Cyclooxygenase-2 (COX-2), an endogenous inducible enzyme, rises in response to inflammation. The aim of this work is to investigate the role of celecoxib, a selective COX-2 inhibitor, in abrogating remote organ dysfunction after hindlimb IR in rats by comparing it with a standard hemorrheologic drug (pentoxifylline). Rats were divided into 4 groups (n = 6 each), group I (sham control, received saline and was kept under anaesthetic for 7 h). Group II (IR, subjected to 1 h of hindlimb tourniquet ischemia and 6 h reperfusion). Group III and IV (pretreated with 200 mg/kg pentoxifylline or 10 mg/kg celecoxib, respectively, intragastrically for 7 days before IR induction). Administration of pentoxifylline or celecoxib produced significant reduction in SGPT, serum creatinine, malondialdehyde, and tumor necrosis factor-α and significant increase in blood pH, blood adenosine triphosphate, and reduced glutathione compared with the IR group (p < 0.05). There was no significant difference among the pretreated groups. Histopathologic findings of the IR lung showed alveolar destruction, inflammatory cells infiltration, mast cell degranulation, and necrosis of the gastrocnemius muscle fibres. These changes were attenuated in the pretreated groups. In conclusion, celecoxib can ameliorate IR induced remote organ injury to a similar extent as pentoxifylline through its antiinflammatory and antioxidant action.

The inflammatory response to skeletal muscle injury: illuminating complexities

Injury of skeletal muscle, and especially mechanically induced damage such as contusion injury, frequently occurs in contact sports, as well as in accidental contact sports, such as hockey and squash. The large variations with regard to injury severity and affected muscle group, as well as non-specificity of reported symptoms, complicate research aimed at finding suitable treatments. Therefore, in order to increase the chances of finding a successful treatment, it is important to understand the underlying mechanisms inherent to this type of skeletal muscle injury and the cellular processes involved in muscle healing following a contusion injury. Arguably the most important of these processes is inflammation since it is a consistent and lasting response. The inflammatory response is dependent on two factors, namely the extent of actual physical damage and the degree of muscle vascularization at the time of injury. However, long-term anti-inflammatory treatment is not necessarily effective in promoting healing, as indicated by various studies on NSAID treatment. Because of the factors named earlier, human studies on the inflammatory response to contusion injury are limited, but several experimental animal models have been designed to study muscle damage and regeneration. The early recovery phase is characterized by the overlapping processes of inflammation and occurrence of secondary damage. Although neutrophil infiltration has been named as a contributor to the latter, no clear evidence exists to support this claim. Macrophages, although forming part of the inflammatory response, have been shown to have a role in recovery, rather than in exacerbating secondary damage. Several probable roles for this cell type in the second phase of recovery, involving resolution processes, have been identified and include the following: (i) phagocytosis to remove cellular debris; (ii) switching from a pro- to anti-inflammatory phenotype in regenerating muscle; (iii) preventing muscle cells from undergoing apoptosis; (iv) releasing factors to promote muscle precursor cell activation and growth; and (v) secretion of cytokines and growth factors to facilitate vascular and muscle fibre repair. These many different roles suggest that a single treatment with one specific target cell population (e.g. neutrophils, macrophages or satellite cells) may not be equally effective in all phases of the post-injury response. To find the optimal targeted, but time-course-dependent, treatments requires substantial further investigations. However, the techniques currently used to induce mechanical injury vary considerably in terms of invasiveness, tools used to induce injury, muscle group selected for injury and contractile status of the muscle, all of which have an influence on the immune and/or cytokine responses. This makes interpretation of the complex responses more difficult. After our review of the literature, we propose that a standardized non-invasive contusion injury is the ideal model for investigations into the immune responses to mechanical skeletal muscle injury. Despite its suitability as a model, the currently available literature with respect to the inflammatory response to injury using contusion models is largely inadequate. Therefore, it may be premature to investigate highly targeted therapies, which may ultimately prove more effective in decreasing athlete recovery time than current therapies that are either not phase-specific, or not administered in a phase-specific fashion.

Erythropoietin improves functional and histological recovery of traumatized skeletal muscle tissue

Apart from its hematopoietic effect, erythropoietin (EPO) is known as pleiotropic cytokine with anti-inflammatory and anti-apoptotic properties. Here, we evaluated for the first time the EPO-dependent regeneration capacity in an in vivo rat model of skeletal muscle trauma. A myoblast cell line was used to study the effect of EPO on serum deprivation-induced cell apoptosis in vitro. A crush injury was performed to the left soleus muscle in 80 rats treated with either EPO or saline. Muscle recovery was assessed by analysis of contraction capacities. Intravital microscopy, BrdU/laminin double immunohistochemistry and cleaved caspase-3 immunohistochemistry of muscle tissue on days 1, 7, 14, and 42 posttrauma served for assessment of local microcirculation, tissue integrity, and cell proliferation. Serum deprivation-induced myoblast apoptosis of 23.9 +/- 1.5% was reduced by EPO to 17.2 +/- 0.8%. Contraction force analysis in the EPO-treated animals revealed significantly improved muscle strength with 10-20% higher values of twitch and tetanic forces over the 42-day observation period. EPO-treated muscle tissue displayed improved functional capillary density as well as reduced leukocytic response and consecutively macromolecular leakage over day 14. Concomitantly, muscle histology showed significantly increased numbers of BrdU-positive satellite cells and interstitial cells as well as slightly lower counts of cleaved caspase-3-positive interstitial cells. EPO results in faster and better regeneration of skeletal muscle tissue after severe trauma and goes along with improved microcirculation. Thus, EPO, a compound established as clinically safe, may represent a promising therapeutic option to optimize the posttraumatic course of muscle tissue healing.

Use of prescription drugs in athletes

Although athletes are young and generally healthy, they use a variety of non-doping classified medicines to treat injuries, cure illnesses and obtain a competitive edge. Athletes and sports medicine physicians try to optimize the treatment of symptoms related to extreme training during an elite athlete's active career. According to several studies, the use of antiasthmatic medication is more frequent among elite athletes than in the general population. The type of training and the kind of sport influence the prevalence of asthma. Asthma is most common among those competing in endurance events, such as cycling, swimming, cross-country skiing and long-distance running. Recent studies show that athletes use also NSAIDs and oral antibacterials more commonly than age-matched controls, especially athletes competing in speed and power sports. Inappropriately high doses and concomitant use of several different NSAIDs has been observed. All medicines have adverse effects that may have deleterious effects on elite athletes' performance. Thus, any unnecessary medication use should be minimized in elite athletes. Inhaled beta(2)-agonists may cause tachycardia and muscle tremor, which are especially harmful in events requiring accuracy and a steady hand. In experimental animal models of acute injury, especially selective cyclo-oxygenase-2 inhibitors have been shown to be detrimental to tissue-level repair. They have been shown to impair mechanical strength return following acute injury to bone, ligament and tendon. This may have clinical implications for future injury susceptibility. However, it should be noted that the current animal studies have limited translation to the clinical setting. Adverse effects related to the CNS and gastrointestinal adverse reactions are commonly reported in connection with NSAID use also in elite athletes. In addition to the potential for adverse effects, recent studies have shown that NSAID use may negatively regulate muscle growth by inhibiting protein synthesis. Physicians and pharmacists taking care of athletes' medication need to be aware of the medicines that an athlete is taking and how those medicines interact with performance, exercise, environment and other medicines. Sport associations should repeatedly monitor not only the use of banned substances, but also the trends of use of legal medicines in athletes. Not only physicians and pharmacists, but also athletes and coaches should be better educated with respect to potential benefits and risks, and how each agent may affect an athlete's performance. The attitudes and beliefs leading to ample use of legal medicines in athletes is an interesting area of future research.

Serotonin mediates PGE2 overexpression through 5-HT2A and 5-HT3 receptor subtypes in serum-free tissue culture of macrophage-like synovial cells

Serotonin antagonists show impressive analgesic efficacy in rheumatoid arthritis, osteoarthritis (OA) or fibromyalgia; however, this effect is not well understood. We examined the mechanism of serotonin-induced inflammation and its antagonists in OA. Serotonin receptor subtypes and COX-2 were analysed by RT-PCR from synovial tissue. Serum-free cultures were stimulated with 10 muM serotonin and/or the antagonists ketanserin (5-HT(2A)), tropisetron (5-HT(3)) and parecoxib (COX-2). Prostaglandin E(2) (PGE(2)), tumour necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta) and leukotriene B4 (LTB4) were measured by an immunoassay in the supernatants. RT-PCR results showed mRNA for 5-HT(2A) and 5-HT(3) receptors, and COX-2. PGE(2) in the supernatants increased by 261.2% +/- 56.7 (mean +/- SEM; P = 0.007) in response to serotonin. TNF-alpha, IL-1beta and LTB4 levels did not change. Ketanserin, tropisetron and parecoxib suppressed PGE(2). The serotonin-induced PGE(2) overexpression appeared thus to be mediated by 5-HT(2A) and 5-HT(3) receptors. This activation might involve COX-2. The findings may explain the potent benefit of 5-HT(3) antagonists.

Sublethal trauma model with systemic endotoxemia for the study of microcirculatory disorders after the second hit

BACKGROUND

Experimental models often cannot simulate the clinical situation in traumatized patients where the septic second hit finally leads to multiple organ dysfunction syndrome and death. We present an experimental animal model combining initial standardized soft tissue trauma to the left hindlimb of rats with subsequent sublethal systemic endotoxemia.

MATERIALS AND METHODS

This study characterizes the influence of trauma and systemic endotoxemia on nutritive blood flow, inflammatory cell-cell interaction and tissue cell integrity in the traumatized region.

RESULTS

At 24 h after local tissue contusion, in vivo analysis of the skeletal muscle microcirculation by means of high resolution fluorescence microscopy revealed intravascular leukocyte accumulation and impairment of nutritive perfusion with tissue hypoxia. Moreover, muscle tissue damage was characterized by myocyte cell apoptosis. Additional systemic exposure of animals to E. coli lipopolysaccharide at 6 h after soft tissue contusion caused a drop in arterial blood pressure as well as coagulatory disorders, as given by marked thrombocytopenia and reduced thromboplastin times. In double-hit exposed animals, skeletal muscle microcirculation presented with an aggravation of inflammation, perfusion failure, and apoptotic cell death after 24 h.

CONCLUSIONS

This model more closely resembles the scenario of polytraumatized patients with the risk of secondary infections and, thus, is suited to characterize anti-inflammatory drugs with respect to their potential to interfere with microcirculatory disorders and elaboration of disseminated intravascular coagulation after trauma.

Activated protein C reduces tissue hypoxia, inflammation, and apoptosis in traumatized skeletal muscle during endotoxemia

OBJECTIVE

Extensive surgical trauma leads to activation of the coagulation cascade and is often complicated by systemic inflammation and infection. Activated protein C, a natural coagulatory inhibitor, was recently shown to reduce mortality in septic patients. We herein report on the actions of activated protein C on skeletal muscle injury in experimental endotoxemia.

DESIGN

Prospective controlled animal study.

SETTING

University animal research facility.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Closed soft tissue trauma was applied on the left hind limb of pentobarbital-anesthetized rats. Six hours later endotoxemia was induced by intraperitoneal injection of Escherichia coli lipopolysaccharide. An equivalent volume of physiologic saline was given in controls. At the same time point, treatment of animals was started by continuous intravenous application of activated protein C (24 microg/kg.hr) or vehicle solution over 18 hrs. Twenty-four hours after trauma, the extensor digitorum longus muscle was microsurgically exposed and analyzed by means of high-resolution multifluorescence microscopy.

MEASUREMENTS AND MAIN RESULTS

Endotoxemia aggravated traumatized muscle injury, as evidenced by reduced nutritive perfusion, increased tissue hypoxia, enhanced leukocyte-endothelial cell interaction, and apoptotic myocyte cells (249 +/- 17 cm/cm vs. 298 +/- 22 cm/cm; reduced nicotinamide adenine dinucleotide [NADH], 149 +/- 15 arbitrary units [AU] vs. 130 +/- 13 AU; 417 +/- 79 cells/mm vs. 344 +/- 77 cells/mm and 62 +/- 9 cells/mm vs. 31 +/- 5 cells/mm). Therapeutic intervention with activated protein C 6 hrs after trama protected nutritive perfusion and tissue oxygenation (341 +/- 24 cm/cm and 115 +/- 8 AU) and reduced inflammatory leukocyte adherence (185 +/- 60 cells/mm) and cellular apoptosis (15 +/- 4 cells/mm). Of note, the protection of traumatized muscle tissue by activated protein C was also maintained during endotoxemia, as indicated by a functional capillary density of 379 +/- 10 cm/cm, a NADH-fluorescence of 102 +/- 6 AU, a leukocyte adherence of 82 +/- 12 cells/mm, and a myocyte apoptosis of 28 +/- 4 cells/mm.

CONCLUSIONS

Microcirculatory injury of traumatized skeletal muscle tissue is enhanced by intravenous endotoxin application in this model of soft tissue trauma. Activated protein C ameliorates microcirculatory dysfunction and tissue injury, in particular in traumatized animals during endotoxemia.

Postoperative Administration of the Analgesic Tramadol, but Not the Selective Cyclooxygenase-2 Inhibitor Parecoxib, Abolishes Postoperative Hyperalgesia in a New Model of Postoperative Pain in Rats

BACKGROUND/AIMS

Using a new animal model of postoperative pain we recently developed, we investigated whether the selective cyclooxygenase-2 (COX-2) inhibitor parecoxib sodium, and the analgesic tramadol hydrochloride, attenuated mechanical primary hyperalgesia induced by minor surgery on the rat tail.

METHODS

For surgery, rats were anesthetized with isoflurane, a 20-mm-long incision was made through the skin and fascia of their tails, and the wound was sutured. Immediately after surgery, rats were injected intraperitoneally with parecoxib sodium (10 or 20 mg x kg(-1)), tramadol hydrochloride (10 mg x kg(-1)), or sterile saline (0.1 ml x kg(-1)). Hyperalgesia was assessed by measuring rats' response latencies to a blunt noxious mechanical stimulus (4 N) applied to their tails. Nociceptive testing was performed before surgery and 90 min after surgery.

RESULTS

Hyperalgesia was present in all saline-injected animals within 90 min of surgery. This hyperalgesia was not attenuated by postoperative injection of parecoxib. However, administration of tramadol completely prevented the development of postoperative hyperalgesia.

CONCLUSION

We have shown that the hyperalgesia in our model of postoperative pain is responsive to treatment with the analgesic tramadol, but it is not responsive to the selective COX-2 inhibitor parecoxib at the doses we used.

Dose and time-dependent effects of cyclooxygenase-2 inhibition on fracture-healing

BACKGROUND

Fracture-healing is impaired in mice lacking a functional cyclooxygenase-2 (COX-2) gene or in rats continuously treated with COX-2 inhibitors. These observations indicate that COX-2 is a critical regulator of fracture repair. Nonsteroidal anti-inflammatory drugs are commonly used to treat pain associated with musculoskeletal trauma and disease. Nonsteroidal anti-inflammatory drugs inhibit COX-2 function and in so doing can impair fracture-healing. The goal of the present study was to determine how variations in nonsteroidal anti-inflammatory drug therapy ultimately affect fracture-healing.

METHODS

Closed femoral fractures were made in female Sprague-Dawley rats. The rats were treated with different doses of celecoxib (a COX-2-selective nonsteroidal anti-inflammatory drug) or were treated for different periods before or after fracture with celecoxib. Eight weeks after the fracture, healing was assessed with radiography and destructive torsional mechanical testing. The effect of celecoxib treatment on fracture callus prostaglandin E2 and F(2alpha) levels was determined as a measure of cyclooxygenase activity.

RESULTS

Celecoxib doses as small as 2 mg/kg/day reduced fracture callus mechanical properties and caused a significant increase in the proportion of nonunions. Similarly, treatment with celecoxib at a dose of 4 mg/kg/day for just five days reduced fracture callus mechanical properties and significantly increased the proportion of nonunions. Conversely, celecoxib therapy prior to fracture or initiated fourteen days after fracture did not significantly increase the proportion of nonunions. Celecoxib treatment at a dose of 4 mg/kg/day reduced fracture callus prostaglandin E2 and F(2alpha) levels by >60%.

CONCLUSIONS

COX-2-selective nonsteroidal anti-inflammatory drug therapy during the early stages of fracture repair significantly reduced fracture callus mechanical properties at later stages of healing and increased the proportion of nonunions in this animal model.

Exaggeration of tissue trauma induces signs and symptoms of acute CRPS I, however displays distinct differences to experimental CRPS II

As CRPS I frequently develops after tissue trauma, we proposed that an exaggerated inflammatory response to tissue trauma may underlie CRPS I. Therefore, we studied the vascular inflammatory, nociceptive and apoptotic sequelae of (i) soft tissue trauma and (ii) exaggerated soft tissue trauma in comparison to those of (iii) sciatic nerve chronic constriction injury, modeling CRPS II. Standardized soft tissue trauma (TR) was induced by means of a controlled impact injury technique in the hind limb of pentobarbital-anesthetized rats. Additional animals received soft tissue trauma and femoral arterial infusion of mediator-enriched supernatant achieved by homogenization and centrifugation of traumatized muscle tissue in order to provoke an exaggerated trauma response (ETR). Infusion of supernatant of non-traumatized muscle served as control intervention (STR, sham trauma response). Neuropathy was induced by chronic constriction injury of the sciatic nerve (CCI). Untreated animals served as controls (CO). Detailed nociceptive testing showed temporarily decreased mechanical pain thresholds in ETR animals that resolved within 14 days, while TR and STR animals, i.e. those with singular limb trauma, and controls remained free of pain. Neither cold- nor heat-evoked allodynia developed in post-traumatic animals, whereas CCI animals presented the well-known pattern of ongoing neuropathic pain. Using high-resolution in vivo multifluorescence microscopy, muscle tissue of traumatized animals revealed an enhanced inflammatory response that was found most pronounced in ETR animals. CCI of the sciatic nerve was not accompanied by tissue inflammation; however, induced myocyte apoptosis. Collectively, these data indicate that exaggeration of trauma response induces signs and symptoms of acute CRPS I. Pain perception displays differences to that in CRPS II. Apoptosis turns out to be a distinctive marker for CRPS, warranting further evaluation in clinical studies.

Effect of systemic hypothermia on local soft tissue trauma-induced microcirculatory and cellular dysfunction in mice*

OBJECTIVE

Changes in body temperature occur as a systemic reaction to severe trauma; however, its role in the manifestation of injury remains unclear. Thermoregulatory responses vary considerably from fever to hypothermia. Although hypothermic trauma patients seem to have a worse prognosis, there is the question whether hypothermia per se or the severity of trauma producing the hypothermia is responsible for aggravated injury and increased mortality rate. The present study unravels how moderate to severe systemic hypothermia modulates local microcirculatory dysfunction and cellular injury in local soft tissue trauma.

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university.

SUBJECTS

C57BL/6J mice.

INTERVENTIONS

A model involving standardized drop weight device-induced tissue trauma and high-resolution multifluorescence microscopy in the dorsal skinfold chamber was used to show arteriolar vasoconstriction, reduction of blood flow, nutritive perfusion failure, and apoptotic cell death at 1 hr after trauma.

MEASUREMENTS AND MAIN RESULTS

During the 8-hr posttrauma observation period, microcirculation, but not apoptosis, restituted to almost baseline level. Concomitant systemic hypothermia of either 34 degrees C or 30 degrees C did not affect late manifestation of apoptotic cell death but aggravated initial microcirculatory dysfunction and inhibited recovery during the 8-hr follow-up period.

CONCLUSIONS

Our study provides evidence that systemic hypothermia may aggravate soft tissue trauma-associated microcirculatory dysfunction. These experimental results clearly support clinical efforts to prevent hypothermia in the acutely traumatized patient.