Cytokine response of electrolytic ablation in an ex vivo perfused liver model

[Molecular repair mechanisms using the Intratissue Percutaneous Electrolysis technique in patellar tendonitis]

OBJECTIVE

To investigate the molecular mechanisms of tissue response after treatment with the Intratissue Percutaneous Electrolysis (EPI(®)) technique in collagenase-induced tendinopathy in Sprague-Dawley rats.

METHODS

Tendinopathy was induced by injecting 50 μg of type i collagenase into the patellar tendon of 24 Sprague Dawley rats of 7 months of age and weighting 300 g. The sample was divided into 4 groups: the control group, collagenase group, and two EPI(®) technique treatment groups of 3 and 6 mA, respectively. An EPI(®) treatment session was applied, and after 3 days, the tendons were analysed using immunoblotting and electrophoresis techniques. An analysis was also made of cytochrome C protein, Smac/Diablo, vascular endothelial growth factor and its receptor 2, as well as the nuclear transcription factor peroxisome proliferator-activated receptor gamma.

RESULTS

A statistically significant increase, compared to the control group, was observed in the expression of cytochrome C, Smac/Diablo, vascular endothelial growth factor, its receptor 2 and peroxisome proliferator-activated receptor gamma in the groups in which the EPI(®) technique was applied.

CONCLUSIONS

EPI(®) technique produces an increase in anti-inflammatory and angiogenic molecular mechanisms in collagenase-induced tendon injury in rats.

Steps for the autologous ex vivo perfused porcine liver-kidney experiment

The use of ex vivo perfused models can mimic the physiological conditions of the liver for short periods, but to maintain normal homeostasis for an extended perfusion period is challenging. We have added the kidney to our previous ex vivo perfused liver experiment model to reproduce a more accurate physiological state for prolonged experiments without using live animals. Five intact livers and kidneys were retrieved post-mortem from sacrificed pigs on different days and perfused for a minimum of 6 hr. Hourly arterial blood gases were obtained to analyze pH, lactate, glucose and renal parameters. The primary endpoint was to investigate the effect of adding one kidney to the model on the acid base balance, glucose, and electrolyte levels. The result of this liver-kidney experiment was compared to the results of five previous liver only perfusion models. In summary, with the addition of one kidney to the ex vivo liver circuit, hyperglycemia and metabolic acidosis were improved. In addition this model reproduces the physiological and metabolic responses of the liver sufficiently accurately to obviate the need for the use of live animals. The ex vivo liver-kidney perfusion model can be used as an alternative method in organ specific studies. It provides a disconnection from numerous systemic influences and allows specific and accurate adjustments of arterial and venous pressures and flow.

History, ethics, advantages and limitations of experimental models for hepatic ablation

Numerous techniques developed in medicine require careful evaluation to determine their indications, limitations and potential side effects prior to their clinical use. At present this generally involves the use of animal models which is undesirable from an ethical standpoint, requires complex and time-consuming authorization, and is very expensive. This process is exemplified in the development of hepatic ablation techniques, starting experiments on explanted livers and progressing to safety and efficacy studies in living animals prior to clinical studies. The two main approaches used are ex vivo isolated non-perfused liver models and in vivo animal models. Ex vivo non perfused models are less expensive, easier to obtain but not suitable to study the heat sink effect or experiments requiring several hours. In vivo animal models closely resemble clinical subjects but often are expensive and have small sample sizes due to ethical guidelines. Isolated perfused ex vivo liver models have been used to study drug toxicity, liver failure, organ transplantation and hepatic ablation and combine advantages of both previous models.

The autologous normothermic ex vivo perfused porcine liver-kidney model: improving the circuit's biochemical and acid-base environment

BACKGROUND

The ex vivo porcine liver perfused model isolates the organ from extrinsic regulatory mechanisms, facilitating an improved understanding of the organ physiology and reaction to various conditions. We have assessed the influence of the addition of a porcine kidney to the circuit.

METHODS

Eight livers were harvested and perfused for 6 hours. In 5 additional experiments a kidney also was connected in parallel. Hourly arterial blood gases were collected to analyze glucose, acid base, and renal parameters. The primary end point was an evaluation of the influence of the kidney on glucose, pH, and electrolyte levels.

RESULTS

In the combined porcine liver-kidney circuit all the parameters significantly improved compared with the liver circuit alone. This was particularly evident for glucose values because normoglycemia was reached by the end of the perfusion, and for pH and electrolyte values that were maintained at initial levels.

CONCLUSIONS

The addition of a porcine kidney to the perfusion circuit improves the biochemical milieu. This might produce more consistent and reliable results, particularly during studies requiring a steady-state environment.

Addition of a kidney to the normothermic ex vivo perfused porcine liver model does not increase cytokine response

The addition of a kidney to the ex vivo liver perfused model may facilitate the circuit homeostatic balance of important biochemical parameters (i.e. pH changes, urea and creatinine, or glucose levels) but might also increase the inflammatory reaction produced. In this study, we compared the production of various cytokines between liver-kidney and liver-alone circuits. Seven livers were harvested from female pigs and perfused for 6 h. In five additional experiments, a kidney was also harvested and connected in parallel. Blood samples for interleukins (IL) 1, 2, 4, 6, 8, 10, and 12, interferon (IFN)-γ and tumor necrosis factor (TNF)-α were collected before perfusion and at hours 1, 2, 4 and 6 postperfusion. In the combined liver-kidney circuit, a significant increase was present only for IL-6 and IL-8, but this did not differ significantly from those recorded in the liver-alone circuit. All other cytokines were not modified from baseline levels. The addition of a kidney to the perfusion circuit does not stimulate a greater inflammatory reaction than that of the liver alone and therefore further confirms the safety of the experimental setups in view of more delicate experiments requiring strict homeostatic conditions.