Inhibition of inducible nitric oxide synthase reduces an acute peripheral motor neuropathy produced by dermal burn injury in mice

Autologous adipose-derived stem cells attenuate muscular atrophy and protect spinal cord ventral horn motor neurons in an animal model of burn injury

BACKGROUND AIMS

Burn injuries might increase muscle mass loss, but the mechanisms are still unclear. In this study, we demonstrated that burn injury induced spinal cord ventral horn motor neuron (VHMN) apoptosis and subsequently caused muscle atrophy and revealed the potential protection of autologous adipose-derived stem cells (ASCs) transplantation on spinal cord VHMNs and muscle against burn injury.

METHODS

Third-degree hind-paw burns were established by contact with a 75°C metal surface for 10 seconds. Adipose tissues were harvested from the groin fat pad, expanded in culture and labeled with chloromethyl-benzamido/1,1'-dioctadecyl-3,3,3',3'- tetramethyl indocarbocyanine perchlorate. The ASCs were transplanted into the injured hind paw at 4 weeks after burn injury. The lumbar spinal cord, sciatic nerve, gastrocnemius muscle and hind-paw skin were processed for immunofluorescent staining at 4 weeks after transplantation, including terminal deoxynucleotidyl transferase (TUNEL) assay, caspase-3, caspase-9, CD 90 and S100, and the gastrocnemius muscle was evaluated through the use of hematoxylin and eosin staining.

RESULTS

Caspase-3-positive, caspase-9-positive and TUNEL-positive cells were significantly increased in the corresponding dermatome spinal cord VHMNs after burn injury. Moreover, the decrease of Schwann cells in sciatic nerve and the increase of denervation atrophy in gastrocnemius muscle were observed. Furthermore, ASCs transplantation significantly attenuated apoptotic death of VHMNs and the area of muscle denervation atrophy in the gastrocnemius muscle fibers.

CONCLUSIONS

The animal model of third-degree burns in the hind paw showed significant apoptosis in the corresponding spinal cord VHMNs, which suggests that neuroprotection might be the potentially therapeutic target in burn-induced muscle atrophy. ASCs have potential neuroprotection against burn injuries through its anti-apoptotic effects.

ICU-Acquired Weakness Is Associated With Differences in Clinical Outcomes in Critically Ill Children

OBJECTIVE

ICU-acquired weakness, comprised critical illness myopathy and critical illness neuropathy, occurs in a significant proportion of critically ill adults and is associated with high morbidity and mortality. Little is known about ICU-acquired weakness among critically ill children. We investigated the incidence of ICU-acquired weakness among PICUs participating in the Virtual PICU Systems database. We also sought to identify associated risk factors for ICU-acquired weakness and evaluate the hypothesis that ICU-acquired weakness is associated with poor clinical outcomes.

DESIGN

Retrospective cohort study.

SETTING

PICU.

MEASUREMENTS AND MAIN RESULTS

Virtual PICU System was queried for critical illness myopathy and critical illness neuropathy between January 2009 and November 2013. Demographic, admission, and clinical outcome variables including mechanical ventilation days, PICU length of stay, and discharge disposition were analyzed. The Pediatric Index of Mortality-2 was used to evaluate and control for illness severity and risk of mortality. Among 203,875 admissions, there were 55 cases of critical illness myopathy reported and no cases of critical illness neuropathy, resulting in an incidence of 0.02%. Mechanical ventilation days were higher among patients with ICU-acquired weakness versus those who did not develop ICU-acquired weakness (31.6 ± 28.9 vs 9.3 ± 20.6; p < 0.001). In our multivariable analysis, when controlling for Pediatric Index of Mortality-2, ICU-acquired weakness was more frequently reported in those with admission diagnoses of respiratory illness and infection and the need for mechanical ventilation, renal replacement therapy, extracorporeal life support, and tracheostomy. ICU-acquired weakness was associated with a longer PICU length of stay, episodes requiring mechanical ventilation, and discharge to an intermediate, chronic care, and rehabilitation care unit. ICU-acquired weakness was not independently associated with mortality.

CONCLUSIONS

ICU-acquired weakness is uncommonly diagnosed among PICU patients reported in Virtual PICU System. ICU-acquired weakness is associated with critical care therapies, invasive procedures, and resource utilization. Limitations of our retrospective study include underrecognition of ICU-acquired weakness and lack of standardized diagnostic criteria within Virtual PICU System. Prospective studies are needed to better understand the true incidence, risk factors, and clinical course for patients who develop ICU-acquired weakness.

Human adult stem cells derived from adipose tissue and bone marrow attenuate enteric neuropathy in the guinea-pig model of acute colitis

Introduction

Mesenchymal stem cells (MSCs) have been identified as a viable treatment for inflammatory bowel disease (IBD). MSCs derived from bone marrow (BM-MSCs) have predominated in experimental models whereas the majority of clinical trials have used MSCs derived from adipose tissue (AT-MSCs), thus there is little consensus on the optimal tissue source. The therapeutic efficacies of these MSCs are yet to be compared in context of the underlying dysfunction of the enteric nervous system innervating the gastrointestinal tract concomitant with IBD. This study aims to characterise the in vitro properties of MSCs and compare their in vivo therapeutic potential for the treatment of enteric neuropathy associated with intestinal inflammation.

Methods

BM-MSCs and AT-MSCs were validated and characterised in vitro. In in vivo experiments, guinea-pigs received either 2,4,6-trinitrobenzene-sulfonate acid (TNBS) for the induction of colitis or sham treatment by enema. MSCs were administered at a dose of 1x10⁶ cells via enema 3 hours after the induction of colitis. Colon tissues were collected 24 and 72 hours after TNBS administration to assess the level of inflammation and damage to the ENS. MSC migration to the myenteric plexus in vivo was elucidated by immunohistochemistry and in vitro using a modified Boyden chamber assay.

Results

Cells exhibited multipotency and a typical surface immunophenotype for validation as bona fide MSCs. In vitro characterisation revealed distinct differences in growth kinetics, clonogenicity and cell morphology between MSC types. In vivo, BM-MSCs were comparatively more effective than AT-MSCs in attenuating leukocyte infiltration and neuronal loss in the myenteric plexus. MSCs from both sources equally ameliorated body weight loss, gross morphological damage to the colon, changes in the neurochemical coding of neuronal subpopulations and the reduction in density of extrinsic and intrinsic nerve fibres innervating the colon. MSCs from both sources migrated to the myenteric plexus in in vivo colitis and in an in vitro assay.

Conclusions

These data from in vitro experiments suggest that AT-MSCs are ideal for cellular expansion. However, BM-MSCs were more therapeutic in the treatment of enteric neuropathy and plexitis. These characteristics should be considered when deciding on the MSC tissue source.

Third-degree hindpaw burn injury induced apoptosis of lumbar spinal cord ventral horn motor neurons and sciatic nerve and muscle atrophy in rats

Background. Severe burns result in hypercatabolic state and concomitant muscle atrophy that persists for several months, thereby limiting patient recovery. However, the effects of burns on the corresponding spinal dermatome remain unknown. This study aimed to investigate whether burns induce apoptosis of spinal cord ventral horn motor neurons (VHMNs) and consequently cause skeletal muscle wasting. Methods. Third-degree hindpaw burn injury with 1% total body surface area (TBSA) rats were euthanized 4 and 8 weeks after burn injury. The apoptosis profiles in the ventral horns of the lumbar spinal cords, sciatic nerves, and gastrocnemius muscles were examined. The Schwann cells in the sciatic nerve were marked with S100. The gastrocnemius muscles were harvested to measure the denervation atrophy. Result. The VHMNs apoptosis in the spinal cord was observed after inducing third-degree burns in the hindpaw. The S100 and TUNEL double-positive cells in the sciatic nerve increased significantly after the burn injury. Gastrocnemius muscle apoptosis and denervation atrophy area increased significantly after the burn injury. Conclusion. Local hindpaw burn induces apoptosis in VHMNs and Schwann cells in sciatic nerve, which causes corresponding gastrocnemius muscle denervation atrophy. Our results provided an animal model to evaluate burn-induced muscle wasting, and elucidate the underlying mechanisms.

Pathophysiology of nerve regeneration and nerve reconstruction in burned patients

In extensive burns peripheral nerves can be involved. The injury to the nerve can be direct by thermal or electrical burns, but nerves can also be indirectly affected by the systemic reaction that follows the burn. Mediators will be released causing a neuropathy to nerves remote from the involved area. Involved mediators and possible therapeutic options will be discussed. In burned patients nerves can be reconstructed using autologous nerve grafts or nerve conduits. A key factor is an adequate wound debridement and a well-vascularized bed to optimize the outgrowth of the axons. Early free tissue transfers have shown promising results.