Cytomorphic Electronics With Memristors for Modeling Fundamental Genetic Circuits.

Cytomorphic engineering attempts to study the cellular behavior of biological systems using electronics. As such, it can be considered analogous to the study of neurobiological concepts for neuromorphic engineering applications. To date, digital and analog translinear electronics have commonly been used in the design of cytomorphic circuits; Such circuits could greatly benefit from lowering the area of the digital memory via memristive circuits. In this article, we propose a novel approach that utilizes the Boltzmann-exponential stochastic transport of ionic species through insulators to naturally model the nonlinear and stochastic behavior of biochemical reactions. We first show that two-terminal memristive devices can capture the non-linear and stochastic behavior of biochemical reactions. Then, we present the design of several building blocks based on analog memristive circuits that inherently model the biophysical mechanisms of gene expression. The circuits model induction by small molecules, activation and repression by transcription factors, biological promoters, cooperative binding, and transcriptional and translational regulation of gene expression. Finally, we utilize the building blocks to form complex mixed-signal networks that can simulate the delay-induced oscillator and the p53-mdm2 interaction in the cancer signaling pathway. Our approach can provide a fast and simple emulative framework for studying genetic circuits and arbitrary large-scale biological networks in systems and synthetic biology. Some challenges may be that memristive devices with frequent learning and programming do not have the same longevity as traditional transistor-based electron-transport devices, and operate with significantly slower time constants, which can limit emulation speed.

Ligation of the intersphincteric fistula tract procedure and its modifications / Procedimento de ligadura de trato de fístula interesfincteriana e suas modificações

ABSTRACT Purpose: Treatment of anal fistulae is regarded as a challenge due to the diverse nature of this disease and its countless complications. Ligation of the intersphincteric fistula tract procedure and its modifications have been popularized among many surgeons worldwide due to their simplicity and promising outcomes. The main purpose of this article was to conduct a comprehensives review of the published literature on ligation of the intersphincteric fistula tract procedure and its modifications. Method: PubMed, the Cochrane database and Ovid were searched from January 2007 to June 2017. Fully published peer-reviewed studies which applied ligation of the intersphincteric fistula tract procedure and its modifications for the treatment of anal fistulae of cryptogenic origin with follow-up of median 12 months were eligible. Uncompleted studies, case reports, reviews, abstracts, letters, short communication, comments, and studies which did not fulfill inclusion criteria were excluded. The primary outcome was to measure primary healing, overall healing, failure, and recurrence of ligation of the intersphincteric fistula tract procedure and its modifications. Results: Twenty-two studies were identified with only ten studies meeting criteria of inclusion. Original ligation of the intersphincteric fistula tract was performed in five studies with a population of 199 patients while the remaining five studies showed four different modifications of the ligation of the intersphincteric fistula tract with a total number of 147 patients. Both original LIFT and its modifications have promising as well as potentially similar outcomes; primary healing in the original ligation of the intersphincteric fistula tract (73.95%) (95% CI 60.3-85.6) performed less than the modifications (82.3%) (95% CI 64.8-94.7). Overall healing in the original ligation of the intersphincteric fistula tract (78.9%) (95% CI 58.5-93.7) performed relatively less than in the modifications (93.6%) (95% CI 81.4-99.6). Failure in the original ligation of the intersphincteric fistula tract (17.9%) (95% CI 4.9-36.5) performed almost the same as the modifications (17.7%) (95% CI 5.3-35.2). Recurrence in the original ligation of the intersphincteric fistula tract was 9.7% (95% CI 1.7-23.2). However, there was no recurrence in the modifications. Conclusion: Ligation of the intersphincteric fistula tract and its modifications are effective and simple procedures in treating simple anal fistulae, especially high transsphincteric ones. However, more trials should be performed to evaluate its effectiveness regarding complex fistulae.

RESUMO Objetivo: O tratamento de fístulas anais é considerado um desafio devido à natureza diversa dessa doença e suas incontáveis complicações. O procedimento de ligadura do trato da fístula interesfincteriana e suas modificações foi popularizado entre cirurgiões em todo o mundo devido a sua simplicidade e desfechos promissores. O principal objetivo deste artigo foi conduzir uma revisão abrangente da literatura publicada sobre o procedimento de ligadura do trato da fístula interesfincteriana e suas modificações. Método: as bases de dados PubMed, Cochrane e Ovid foram pesquisadas de janeiro de 2007 a junho de 2017. Estudos publicados com revisão por pares que aplicaram o procedimento de ligadura do trato da fístula interesfincteriana e suas modificações para o tratamento de fístulas anais de origem criptogênica com acompanhamento de mediana de 12 meses foram elegíveis. Estudos incompletos, relatos de casos, revisões, resumos, cartas, comunicação breve, comentários e estudos que não preenchiam os critérios de inclusão foram excluídos. O desfecho primário foi medir a cicatrização primária, a cicatrização geral, falhas e recorrência do procedimento de ligadura do trato da fístula interesfincteriana e suas modificações. Resultados: Vinte e dois estudos foram identificados com apenas dez estudos atendendo aos critérios de inclusão. A ligadura original do trato da fístula interesfincteriana foi realizada em cinco estudos com uma população de 199 pacientes, enquanto os cinco estudos restantes apresentaram quatro modificações diferentes da ligadura do trato da fístula interesfincteriana com um total de 147 pacientes. Tanto o LIFT original quanto suas modificações têm resultados promissores e desfechos potencialmente semelhantes; cicatrização primária na ligadura original do trato da fístula interesfincteriana de 73,95% (IC 95% 60,3-85,6) menos realizada que as modificações de 82,3% (IC 95% 64,8-94,7). Cicatrização geral na ligadura original do trato da fístula interesfincteriana de 78,9% (IC 95% 58,5-93,7) realizada relativamente menos do que as modificações (93,6%, IC 95% 81,4-99,6). A falha na ligadura original do trato da fístula interesfincteriana (17,9%; IC 95% 4,9-36,5) realizada quase tanto quanto as modificações (17,7%; IC 95% 5,3-35,2). Recidiva na ligadura original do trato da fístula interesfincteriana em 9,7% (IC 95% 1,7-23,2). No entanto, não houve recorrência nas modificações. Conclusão: A ligadura do trato da fístula interesfincteriana e suas modificações são procedimentos eficazes e simples no tratamento de fístulas anais simples, especialmente as transesfincterianas altas. No entanto, mais estudos devem ser realizados para avaliar sua eficácia em relação às fístulas complexas.

In vitro osteoblastic differentiation of mesenchymal stem cells generates cell layers with distinct properties.

BACKGROUND: Differentiation of mesenchymal stem cells to osteoblasts is widely performed in research laboratories. Classical tests to prove this differentiation employ procedures such as cell fixation, cell lysis or cell scraping. Very few studies report gentle dissociation of mesenchymal stem cells undergoing an osteodifferentiation process. Here we used this technique to reveal the presence of several cell layers during osteogenesis and to study their different properties. METHODS: Through the sequential enzymatic detachment of the cells, we confirm the presence of several layers of differentiated cells and we compare them in terms of enzymatic sensitivity for dissociation, expression of cluster of differentiation, cytosolic calcium oscillations and osteogenic potential. Adipogenic and neurogenic differentiations were also performed in order to compare the cell layers. RESULTS: The cells undergoing differentiation formed one layer in the neurogenic differentiation, two layers in the adipogenic differentiation and at least four layers in the osteogenic differentiation. In the latter, the upper layers, maintained by a collagen I extracellular matrix, can be dissociated using collagenase I, while the remaining lowest layer, attached to the bottom of the dish, is sensitive only to trypsin-versene. The action of collagenase I is more efficient before the mineralization of the extracellular matrix. The collagenase-sensitive and trypsin-sensitive layers differ in their cluster of differentiation expression. The dissociation of the cells on day 15 reveals that cells could resume their growth (increase in cell number) and rapidly differentiate again in osteoblasts, in 2 weeks (instead of 4 weeks). Cells from the upper layers displayed a higher mineralization. CONCLUSIONS: MSCs undergoing osteogenic differentiation form several layers with distinct osteogenic properties. This could allow the investigators to use upper layers to rapidly produce differentiated osteoblasts and the lowest layer to continue growth and differentiation until an ulterior dissociation.

Electrical control of calcium oscillations in mesenchymal stem cells using microsecond pulsed electric fields.

BACKGROUND: Human mesenchymal stem cells are promising tools for regenerative medicine due to their ability to differentiate into many cellular types such as osteocytes, chondrocytes and adipocytes amongst many other cell types. These cells present spontaneous calcium oscillations implicating calcium channels and pumps of the plasma membrane and the endoplasmic reticulum. These oscillations regulate many basic functions in the cell such as proliferation and differentiation. Therefore, the possibility to mimic or regulate these oscillations might be useful to regulate mesenchymal stem cells biological functions. METHODS: One or several electric pulses of 100 µs were used to induce Ca2+ spikes caused by the penetration of Ca2+ from the extracellular medium, through the transiently electropermeabilized plasma membrane, in human adipose mesenchymal stem cells from several donors. Attached cells were preloaded with Fluo-4 AM and exposed to the electric pulse(s) under the fluorescence microscope. Viability was also checked. RESULTS: According to the pulse(s) electric field amplitude, it is possible to generate a supplementary calcium spike with properties close to those of calcium spontaneous oscillations, or, on the contrary, to inhibit the spontaneous calcium oscillations for a very long time compared to the pulse duration. Through that inhibition of the oscillations, Ca2+ oscillations of desired amplitude and frequency could then be imposed on the cells using subsequent electric pulses. None of the pulses used here, even those with the highest amplitude, caused a loss of cell viability. CONCLUSIONS: An easy way to control Ca2+ oscillations in mesenchymal stem cells, through their cancellation or the addition of supplementary Ca2+ spikes, is reported here. Indeed, the direct link between the microsecond electric pulse(s) delivery and the occurrence/cancellation of cytosolic Ca2+ spikes allowed us to mimic and regulate the Ca2+ oscillations in these cells. Since microsecond electric pulse delivery constitutes a simple technology available in many laboratories, this new tool might be useful to further investigate the role of Ca2+ in human mesenchymal stem cells biological processes such as proliferation and differentiation.