Juan F. Del Cañizo

3D bioprinting of functional human skin: production and in vivo analysis

Significant progress has been made over the past 25 years in the development of in vitro-engineered substitutes that mimic human skin, either to be used as grafts for the replacement of lost skin, or for the establishment of in vitro human skin models. In this sense, laboratory-grown skin substitutes containing dermal and epidermal components offer a promising approach to skin engineering. In particular, a human plasma-based bilayered skin generated by our group, has been applied successfully to treat burns as well as traumatic and surgical wounds in a large number of patients in Spain. There are some aspects requiring improvements in the production process of this skin; for example, the relatively long time (three weeks) needed to produce the surface required to cover an extensive burn or a large wound, and the necessity to automatize and standardize a process currently performed manually. 3D bioprinting has emerged as a flexible tool in regenerative medicine and it provides a platform to address these challenges. In the present study, we have used this technique to print a human bilayered skin using bioinks containing human plasma as well as primary human fibroblasts and keratinocytes that were obtained from skin biopsies. We were able to generate 100 cm2, a standard P100 tissue culture plate, of printed skin in less than 35 min (including the 30 min required for fibrin gelation). We have analysed the structure and function of the printed skin using histological and immunohistochemical methods, both in 3D in vitro cultures and after long-term transplantation to immunodeficient mice. In both cases, the generated skin was very similar to human skin and, furthermore, it was indistinguishable from bilayered dermo-epidermal equivalents, handmade in our laboratories. These results demonstrate that 3D bioprinting is a suitable technology to generate bioengineered skin for therapeutical and industrial applications in an automatized manner.

Synchrony Relationships between the Left Ventricle and a left Ventricular Assist Device: An Experimental Study in Pigs:

Background: Synchronization between the left ventricle and a left ventricular assist device (LVAD) may be important for ventricular unloading and coronary perfusion. We assessed the synchrony between cardiac and LVAD cycles by increasing delays in steps of 100 msec throughout the cycle, under conditions of total and partial left ventricular support. Methods: We studied 7 healthy minipigs weighing 30–40 kg. A 60–cc Berlin Heart Excor LVAD was implanted and connected to a BCM 1200 console, making it possible to synchronize the LVAD systole and the EKG signal with a prefixed delay. We recorded hemodynamic parameters (including aortic, pulmonary, and left ventricular pressure) and LVAD flow for each delay. Results: Intraventricular pressure during LVAD systole was minimized with delays of around 40–80% of one cycle. In addition, total flow was higher under these conditions. Conclusions: This study shows that the synchronous mode of LVAD operation is feasible. Moreover, a delay in device contraction until the second half of the cardiac cycle optimizes ventricular unloading and may eventually improve myocardial recovery.

Low-Cost Pulsatile Cardiac Assist Device With Compliant Input Chamber

We propose a new, low-cost pulsatile ventricular assist device (VAD) for short-term applications. The new device could prove very useful in emergency ventricular failure in which patient survival is not assured. In these cases, the device allows ventricular function to be maintained as the patients situation is evaluated and a decision is made on whether to perform a heart transplant or to replace the device with a long-term VAD. The device has a pneumatic tubular blood chamber, clip valves over the cannulae, and a compliant input chamber that improves filling of the pump. Clip valves and all other functions of the device are controlled by means of a computerized console. The use of clip valves reduces the cost of the disposable part of the device.

Effects of Sevoflurane and Propofol on Organ Blood Flow in Left Ventricular Assist Devices in Pigs

The aim of this study was to assess the effect of sevoflurane and propofol on organ blood flow in a porcine model with a left ventricular assist device (LVAD). Ten healthy minipigs were divided into 2 groups (5 per group) according to the anesthetic received (sevoflurane or propofol). A Biomedicus centrifugal pump was implanted. Organ blood flow (measured using colored microspheres), markers of tissue injury, and hemodynamic parameters were assessed at baseline (pump off) and after 30 minutes of partial support. Blood flow was significantly higher in the brain (both frontal lobes), heart (both ventricles), and liver after 30 minutes in the sevoflurane group, although no significant differences were recorded for the lung, kidney, or ileum. Serum levels of alanine aminotransferase and total bilirubin were significantly higher after 30 minutes in the propofol group, although no significant differences were detected between the groups for other parameters of liver function, kidney function, or lactic acid levels. The hemodynamic parameters were similar in both groups. We demonstrated that, compared with propofol, sevoflurane increases blood flow in the brain, liver, and heart after implantation of an LVAD under conditions of partial support.

Development of an automated liver perfusion system: The benefit of a hemofilter

Introduction: Liver perfusion machines are close to becoming a reality in the transplantation field. However, depending on the techniques used and the goals pursued, their application is limited in the research field. Here, we present the entire development of a perfusion system with self-made engineering, completely autonomous controls, and a high degree of versatility that allows the design of different studies on liver functionality. Methods: A user-friendly interface permits real-time monitoring and remote control by the devices within the circuit. Centrifugal pumps allow the perfusate enter the organ with controlled pressures and flows at both hepatic artery and portal vein. The implementation of a hemofilter as a novel tool permits to control and maintain homeostasis. Peristaltic pumps adjust pH, extraction rate, and total volume by means of sensors. Results: Real-time monitoring facilitates liver functionality assessment. The controlled system shows rapid stabilization and quick responses to changes during 6 h of perfusion experiments. Furthermore, the integration of a hemofilter helps the system to eliminate toxic waste and maintain homeostasis. Discussion: The machine provides the basis of a perfusion system with autonomous controls and the implementation of a hemofilter that enables a more efficient control of hemostasis. Moreover, the developed hardware and software are subjected to further tuning for additional purposes such as pathophysiologic studies, suboptimal grafts recovery, or recellularization of decellularized scaffolds among others.

Corrigendum to “Effects of Sevoflurane and Propofol on Organ Blood Flow in Left Ventricular Assist Devices in Pigs”

[This corrects the article DOI: 10.1155/2015/898373.].

Beneficial Effect of Short Pretransplant Period of Hypothermic Pulsatile Perfusion of the Warm-Ischemic Kidney after Cold Storage: Experimental Study

Warm ischemia (WI) produces a significant deleterious effect in potential kidney grafts. Hypothermic machine perfusion (HMP) seems to improve immediate graft function after transplant. Our aim was to analyze the effect of short pretransplant periods of pulsatile HMP on histology and renal injury in warm-ischemic kidneys. Twelve minipigs were used. WI was achieved in the right kidney by applying a vascular clamp for 45 min. After nephrectomy, autotransplant was performed following one of two strategies: cold storage of the kidneys or cold storage combined with perfusion in pulsatile HMP. The graft was removed early to study renal morphology, inflammation (fibrosis), and apoptosis. Proinflammatory activity and fibrosis were less pronounced after cold storage of the kidneys with HMP than after cold storage only. The use of HMP also decreased apoptosis compared with cold storage only. The detrimental effects on cells of an initial and prolonged period of WI seem to improve with a preservation protocol that includes a short period of pulsatile HMP after cold storage and immediately before the transplant, in comparison with cold storage only.