Compartment syndrome causes systemic inflammation in a rat

ACETYL-COA PRODUCTION BY OCTANOIC ACID ALLEVIATES ACUTE COMPARTMENT SYNDROME-INDUCED SKELETAL MUSCLE INJURY THROUGH REGULATING MITOPHAGY

ABSTRACT

Background: Treatment of acute compartment syndrome (ACS)-induced skeletal muscle injury remains a challenge. Previous studies have shown that octanoic acid is a promising treatment for ACS owing to its potential ability to regulate metabolic/epigenetic pathways in ischemic injury. The present study was designed to investigate the efficacy and underlying mechanism of octanoic acid in ACS-induced skeletal muscle injury. Methods: In this study, we established a saline infusion ACS rat model. Subsequently, we assessed the protective effects of sodium octanoate (NaO, sodium salt of octanoic acid) on ACS-induced skeletal muscle injury. Afterward, the level of acetyl-coenzyme A and histone acetylation in the skeletal muscle tissue were quantified. Moreover, we investigated the activation of the AMP-activated protein kinas pathway and the occurrence of mitophagy in the skeletal muscle tissue. Lastly, we scrutinized the expression of proteins associated with mitochondrial dynamics in the skeletal muscle tissue. Results: The administration of NaO attenuated muscle inflammation, alleviating oxidative stress and muscle edema. Moreover, NaO treatment enhanced muscle blood perfusion, leading to the inhibition of apoptosis-related skeletal muscle cell death after ACS. In addition, NaO demonstrated the ability to halt skeletal muscle fibrosis and enhance the functional recovery of muscle post-ACS. Further analysis indicates that NaO treatment increases the acetyl-CoA level in muscle and the process of histone acetylation by acetyl-CoA. Lastly, we found NaO treatment exerts a stimulatory impact on the activation of the AMPK pathway, thus promoting mitophagy and improving mitochondrial dynamics. Conclusion: Our findings indicate that octanoic acid may ameliorate skeletal muscle injury induced by ACS. Its protective effects may be attributed to the promotion of acetyl-CoA synthesis and histone acetylation within the muscular tissue, as well as its activation of the AMPK-related mitophagy pathway.

Olink proteomics analysis uncovers the landscape of inflammation-related proteins in patients with acute compartment syndrome

Purpose

Our primary purpose was to explore the landscape of inflammation-related proteins, and our second goal was to investigate these proteins as potential biomarkers of acute compartment syndrome (ACS), which is a serious complication of tibial fractures.

Methods

We collected sera from 15 healthy subjects (control group, CG) and 30 patients with tibial fractures on admission day, comprising 15 patients with ACS (ACS group, AG) and 15 patients without ACS (fracture group, FG). Ten samples in each group were analyzed by the inflammation panel of Olink Proteomics Analysis, and all samples were verified by an ELISA. Receiver-operating characteristic (ROC) curve analysis was performed to identify the diagnostic ability and cutoff values of potential biomarkers.

Results

Our findings showed that the levels of IL6, CSF-1, and HGF in the FG were significantly higher than those in the CG. Similar results were found between the AG and CG, and their cutoff values for predicting ACS compared with the CG were 9.225 pg/ml, 81.04 pg/ml, and 0.3301 ng/ml, respectively. Furthermore, their combination had the highest diagnostic accuracy. Notably, compared with FG, we only found a higher expression of CCL23 in the AG. Additionally, we identified 35.75 pg/ml as the cutoff value of CCL23 for predicting ACS in patients with tibial fractures.

Conclusion

We identified CCL23 as a potential biomarker of ACS in comparison with tibial fracture patients and the significance of the combined diagnosis of IL6, CSF-1, and HGF for predicting ACS compared with healthy individuals. Furthermore, we also found their cutoff values, providing clinicians with a new method for rapidly diagnosing ACS. However, we need larger samples to verify our results.

Early assessment of extremity compartment syndrome by biochemical markers in a rat model

BACKGROUND

This experimental study aimed to define a biochemical marker that will enable early diagnosis of acute compartment syndrome (ACS) of extremities, a mortal condition that occurs due to trauma.

METHODS

A total of 15 Wistar rats were included in the study in which saline infusion technique, a clinically compatible ACS model, was applied. After the rats were anesthetized with ketamine-xylazine, the in-compartment pressure of the hind limb was slowly increased with saline delivered through the angiocatheter, and after reaching the target compartment pressure, the pressure level was kept with a rubber tourniquet. The in-compartment pressure level was continuously monitored with a pressure transducer. The rats were divided into three groups. No intervention was applied to the control group (CG) (n = 3). In study group 1 (SG1) (n = 6), ACS was created using the saline infusion technique, keeping the in-compartment pressure between 30 and 40 mmHg for 45 min. In study group 2 (SG2) (n = 6), ACS was created using the saline infusion technique, keeping the in-compartment pressure between 30 and 40 mmHg for 90 min. Fasciotomy was performed on all rats. Tissue samples were obtained for histopathological examination and blood samples for biochemical analysis.

RESULTS

Total oxidant status (TOS) (p = 0.004), ischemia-modified albumin (IMA) (p = 0.030), aspartate transferase (AST) (p = 0.003) and neopterin (p = 0.012) levels differed significantly between groups in the early period of muscle ischemia. In fact, TOS levels differed significantly between the groups even in the cellular phase where signs of ischemia were not observed (p = 0.048, p = 0.024). According to histopathological evaluation, there was no significant difference between the groups.

DISCUSSION

TOS can be detected in the early reversible stage of ischemia, when the histopathological findings of ACS do not occur.

Lower Extremity Extracorporeal Distal Revascularization in a Swine Model of Prolonged Extremity Ischemia

BACKGROUND

Acute arterial occlusion of the lower extremity is a time-dependent emergency that requires prompt revascularization. Lower extremity extracorporeal distal revascularization (LEEDR) is a technique that can be initiated bedside when definitive therapy is delayed. The aim of this study is to evaluate this technique in a swine model of prolonged extremity ischemia.

METHODS

Anesthetized swine underwent right femoral and left posterior tibial artery cannulation, left iliac venous flow monitoring (mL/min), and continuous left anterior compartment pressure (CP) monitoring (mm Hg). The iliac artery was clamped for 6 hr. LEEDR animals underwent 5 hr of extracorporeal femoral-to-tibial blood flow at 150 mL/min; controls had no intervention. At 6 hr, LEEDR was discontinued, iliac flow restored, and anterior CP monitored for 3 hr.

RESULTS

Baseline characteristics were similar across both the groups. Iliac clamping saw an expected fall in iliac venous flow (258 ± 30 to 82 ± 19; P < 0.001). LEEDR resulted in a rise in iliac venous flow (82 ± 20 to 181 ± 16; P < 0.001); control arm flow remained reduced (71 ± 8; P < 0.001). Once inflow was restored, venous flow returned to baseline. Revascularization provoked a higher peak CP in the control arm versus in the LEEDR group (25 ± 5 vs. 6 ± 1; P = 0.02).

CONCLUSIONS

An extracorporeal circuit can temporarily revascularize an extremity in a swine model of prolonged ischemia, mitigating reperfusion injury and maintaining normal CPs. This concept should undergo further evaluation as a bedside tool to mitigate extremity ischemia prior to definitive revascularization.

Single-cell RNA-seq reveals cellular heterogeneity from deep fascia in patients with acute compartment syndrome

Introduction

High stress in the compartment surrounded by the deep fascia can cause acute compartment syndrome (ACS) that may result in necrosis of the limbs. The study aims to investigate the cellular heterogeneity of the deep fascia in ACS patients by single-cell RNA sequencing (scRNA-seq).

Methods

We collected deep fascia samples from patients with ACS (high-stress group, HG, n=3) and patients receiving thigh amputation due to osteosarcoma (normal-stress group, NG, n=3). We utilized ultrasound and scanning electron microscopy to observe the morphologic change of the deep fascia, used multiplex staining and multispectral imaging to explore immune cell infiltration, and applied scRNA-seq to investigate the cellular heterogeneity of the deep fascia and to identify differentially expressed genes.

Results

Notably, we identified GZMK⁺interferon-act CD4 central memory T cells as a specific high-stress compartment subcluster expressing interferon-related genes. Additionally, the changes in the proportions of inflammation-related subclusters, such as the increased proportion of M2 macrophages and decreased proportion of M1 macrophages, may play crucial roles in the balance of pro-inflammatory and anti-inflammatory in the development of ACS. Furthermore, we found that heat shock protein genes were highly expressed but metal ion-related genes (S100 family and metallothionein family) were down-regulated in various subpopulations under high stress.

Conclusions

We identified a high stress-specific subcluster and variations in immune cells and fibroblast subclusters, as well as their differentially expressed genes, in ACS patients. Our findings reveal the functions of the deep fascia in the pathophysiology of ACS, providing new approaches for its treatment and prevention.

The mechanism of the Nfe2l2/Hmox1 signaling pathway in ferroptosis regulation in acute compartment syndrome

Acute compartment syndrome (ACS) is a life-threatening orthopedic emergency, which can even result in amputation. Ferroptosis is an iron-dependent form of nonapoptotic cell death. This study investigated the mechanism of ferroptosis in ACS, explored candidate markers, and determined effective treatments. This study identified pathways involved in the development of ACS through gene set enrichment analysis (GSEA), Gene Ontology, Kyoto Encyclopedia of Genes and Genomes (KEGG), and GSEA of heme oxygenase 1 (Hmox1). Bioinformatics methods, combined with real-time quantitative polymerase chain reaction, western blot analysis, and iron staining, were applied to determine whether ferroptosis was involved in the progression of ACS and to explore the mechanism of nuclear factor erythroid-2-related factor 2 (Nfe2l2)/Hmox1 in ferroptosis regulation. Optimal drugs for the treatment of ACS were also investigated using Connectivity Map. The ferroptosis pathway was enriched in GSEA, KEGG of DEGs, and GSEA of Hmox1. After ACS, the reactive oxygen species content, tissue iron content, and oxidative stress level increased, whereas glutathione peroxidase 4 protein expression decreased. The skeletal muscle was swollen and necrotized; the number of mitochondrial cristae became fewer or even disappeared, and Nfe2l2/Hmox1 expression increased at the transcriptional and protein levels. Hmox1 was highly expressed in ACS, indicating that Hmox1 is a possible marker for ACS. we could predict 12 potential target drugs for the treatment of ACS. In conclusion, Hmox1 was a potential candidate marker for ACS diagnosis. Ferroptosis was involved in the progression of ACS. It was speculated that ferroptosis is inhibited by the Nfe2l2/Hmox1 signaling pathway.

Efficacy of non-surgical interventions for promoting improved functional outcomes following acute compartment syndrome: A systematic review

BACKGROUND

Acute compartment syndrome (ACS) is a devastating complication which develops following a traumatic extremity injury that results in increased pressure within osteofascial compartments, thereby leading to ischemia, muscle and nerve necrosis, and creates a life-threatening condition if left untreated. Fasciotomy is the only available standard surgical intervention for ACS. Following fasciotomy the affected extremity is plagued by prolonged impairments in function. As such, an unmet clinical need exists for adjunct, non-surgical therapies which can facilitate accelerated functional recovery following ACS. Thus, the purpose of this systematic review was to examine the state of the literature for non-surgical interventions that aim to improve muscle contractile functional recovery of the affected limb following ACS.

METHODS

English language manuscripts which evaluated non-surgical interventions for ACS, namely those which evaluated the function of the affected extremity, were identified as per PRISMA protocols via searches within three databases from inception to February 2022. Qualitative narrative data synthesis was performed including: study characteristics, type of interventions, quality, and outcomes. Risk of bias (RoB) was assessed using the Systematic Review Centre for Laboratory Animal Experimentation's (SYRCLE) RoB tool and reported level of evidence for each article.

RESULTS

Upon review of all initially identified reports, 29 studies were found to be eligible and included. 23 distinct non-surgical interventions were found to facilitate improved muscle contractile function following ACS. Out of 29 studies, 15 studies which evaluated chemical and biological interventions, showed large effect sizes for muscle function improvement.

CONCLUSIONS

This systematic review demonstrated that the majority of identified non-surgical interventions facilitated an improvement in muscle contractile function following pathological conditions of ACS.

Embryonic stem cell-derived mesenchymal stem cells alleviate skeletal muscle injury induced by acute compartment syndrome

Background

Acute compartment syndrome (ACS), a well-known complication of musculoskeletal injury, results in muscle necrosis and cell death. Embryonic stem cell-derived mesenchymal stem cells (ESC-MSCs) have been shown to be a promising therapy for ACS. However, their effectiveness and potentially protective mechanism remain unknown. The present study was designed to investigate the efficacy and underlying mechanism of ESC-MSCs in ACS-induced skeletal muscle injury.

Method

A total of 168 male Sprague–Dawley (SD) rats underwent 2 h of intracompartmental pressure elevation by saline infusion into the anterior compartment of the left hindlimb to establish the ACS model. ESC-MSCs were differentiated from the human embryonic stem cell (ESC) line H9. A dose of 1.2 × 10⁶ of ESC-MSCs was intravenously injected during fasciotomy. Post-ACS assessments included skeletal edema index, serum indicators, histological analysis, apoptosis, fibrosis, regeneration, and functional recovery of skeletal muscle. Then, fluorescence microscopy was used to observe the distribution of labeled ESC-MSCs in vivo, and western blotting and immunofluorescence analyses were performed to examine macrophages infiltration in skeletal muscle. Finally, we used liposomal clodronate to deplete macrophages and reassess skeletal muscle injury in response to ESC-MSC therapy.

Result

ESC-MSCs significantly reduced systemic inflammatory responses, ACS-induced skeletal muscle edema, and cell apoptosis. In addition, ESC-MSCs inhibited skeletal muscle fibrosis and increased regeneration and functional recovery of skeletal muscle after ACS. The beneficial effects of ESC-MSCs on ACS-induced skeletal muscle injury were accompanied by a decrease in CD86-positive M1 macrophage polarization and an increase in CD206-positive M2 macrophage polarization. After depleting macrophages with liposomal clodronate, the beneficial effects of ESC-MSCs were attenuated.

Conclusion

Our findings suggest that embryonic stem cell-derived mesenchymal stem cells infusion could effectively alleviate ACS-induced skeletal muscle injury, in which the beneficial effects were related to the regulation of macrophages polarization.

Animal models in compartment syndrome: a review of existing literature

Objective:

Extremity compartment syndrome (ECS) is a morbid condition resulting in permanent myoneural damage. Currently, the diagnosis of compartment syndrome relies on clinical symptoms and/or intracompartment pressure measurements, both of which are poor predictors of ECS. Animal models have been used to better define cellular mechanisms, diagnosis, and treatment of ECS. However, no standardized model exists. The purpose of this study was to identify existing animal research on extremity compartment syndrome to summarize the current state of the literature and to identify weaknesses that could be improved with additional research.

Methods:

A MEDLINE database search and reverse inclusion protocol were utilized. We included all animal models of ECS.

Results:

Forty-one studies were included. Dogs were the most commonly used model species, followed by pigs and rats. Most studies sought to better define the pathophysiology of compartment syndrome. Other studies evaluated experimental diagnostic modalities or potential treatments. The most common compartment syndrome model was intracompartment infusion, followed by tourniquet and intracompartment balloon models. Few models incorporated additional soft tissue or osseous injury. Only 65.9% of the reviewed studies confirmed that their model created myoneural injury similar to extremity compartment syndrome.

Conclusions:

Study purpose, methodology, and outcome measures varied widely across included studies. A standardized definition for animal compartment syndrome would direct more consistent research in this field. Few animal models have investigated the pathophysiologic relationship between traumatic injury and the development of compartment syndrome. A validated, clinically relevant animal model of extremity compartment syndrome would spur improvement in diagnosis and therapeutic interventions.

Two-step machine learning method for the rapid analysis of microvascular flow in intravital video microscopy

Microvascular blood flow is crucial for tissue and organ function and is often severely affected by diseases. Therefore, investigating the microvasculature under different pathological circumstances is essential to understand the role of the microcirculation in health and sickness. Microvascular blood flow is generally investigated with Intravital Video Microscopy (IVM), and the captured images are stored on a computer for later off-line analysis. The analysis of these images is a manual and challenging process, evaluating experiments very time consuming and susceptible to human error. Since more advanced digital cameras are used in IVM, the experimental data volume will also increase significantly. This study presents a new two-step image processing algorithm that uses a trained Convolutional Neural Network (CNN) to functionally analyze IVM microscopic images without the need for manual analysis. While the first step uses a modified vessel segmentation algorithm to extract the location of vessel-like structures, the second step uses a 3D-CNN to assess whether the vessel-like structures have blood flowing in it or not. We demonstrate that our two-step algorithm can efficiently analyze IVM image data with high accuracy (83%). To our knowledge, this is the first application of machine learning for the functional analysis of microvascular blood flow in vivo.

Continual near-infrared spectroscopy monitoring in the injured lower limb and acute compartment syndrome: an FDA-IDE trial

Aims

The aim of this study was to evaluate near-infrared spectroscopy (NIRS) as a continuous, non-invasive monitor for acute compartment syndrome (ACS).

Patients and Methods

NIRS sensors were placed on 86 patients with, and 23 without (controls), severe leg injury. NIRS values were recorded for up to 48 hours. Longitudinal data were analyzed using summary and graphical methods, bivariate comparisons, and multivariable multilevel modelling.

Results

Mean NIRS values in the anterior, lateral, superficial posterior, and deep posterior compartments were between 72% and 78% in injured legs, between 69% and 72% in uninjured legs, and between 71% and 73% in bilaterally uninjured legs. In patients without ACS, the values were typically > 3% higher in injured compartments. All seven limbs with ACS had at least one compartment where NIRS values were 3% or more below a reference uninjured control compartment. Missing data were encountered in many instances.

Conclusion

NIRS oximetry might be used to aid the assessment and management of patients with ACS. Sustained hyperaemia is consistent with the absence of ACS in injured legs. Loss of the hyperaemic differential warrants heightened surveillance. NIRS values in at least one injured compartment(s) were > 3% below the uninjured contralateral compartment(s) in all seven patients with ACS. Additional interventional studies are required to validate the use of NIRS for ACS monitoring. Cite this article: Bone Joint J 2018;100-B:787-97.

Predictors of compartment syndrome of the foot after fracture of the calcaneus

Aims

Identifying predictors of compartment syndrome in the foot after a fracture of the calcaneus may lead to earlier diagnosis and treatment. The aim of our study was to identify any such predictors.

Patients and Methods

We retrospectively reviewed 303 patients (313 fractures) with a fracture of the calcaneus who presented to us between October 2008 and September 2016. The presence of compartment syndrome and potential predictors were identified by reviewing their medical records. Potential predictors included age, gender, concomitant foot injury, mechanism of injury, fracture classification, time from injury to admission, underlying illness, use of anticoagulant/antiplatelet agents, smoking status and occupation. Associations with predictors were analyzed using logistic regression analysis.

Results

Of the 313 fractures of the calcaneus, 12 (3.8%) developed a compartment syndrome. A Sanders type IV fracture was the only strongly associated factor (odds ratio 21.67, p = 0.007). Other variables did not reach statistical significance.

Conclusion

A Sanders type IV fracture is the best predictor of compartment syndrome after a fracture of the calcaneus. Cite this article: Bone Joint J 2018;100-B:303–8.