On the Use of a Multimodal Optimizer for Fitting Neuron Models. Application to the Cerebellar Granule Cell

This article extends a recent methodological workflow for creating realistic and computationally efficient neuron models whilst capturing essential aspects of single-neuron dynamics. We overcome the intrinsic limitations of the extant optimization methods by proposing an alternative optimization component based on multimodal algorithms. This approach can natively explore a diverse population of neuron model configurations. In contrast to methods that focus on a single global optimum, the multimodal method allows directly obtaining a set of promising solutions for a single but complex multi-feature objective function. The final sparse population of candidate solutions has to be analyzed and evaluated according to the biological plausibility and their objective to the target features by the expert. In order to illustrate the value of this approach, we base our proposal on the optimization of cerebellar granule cell (GrC) models that replicate the essential properties of the biological cell. Our results show the emerging variability of plausible sets of values that this type of neuron can adopt underlying complex spiking characteristics. Also, the set of selected cerebellar GrC models captured spiking dynamics closer to the reference model than the single model obtained with off-the-shelf parameter optimization algorithms used in our previous article. The method hereby proposed represents a valuable strategy for adjusting a varied population of realistic and simplified neuron models. It can be applied to other kinds of neuron models and biological contexts.

Deleterious Effect of Human Umbilical Cord Blood Mononuclear Cell Transplantation on Thioacetamide-Induced Chronic Liver Damage in Rats

Our research group investigates whether human mononuclear cells isolated from umbilical cord blood (HUCBM cells) might be valuable in hepatic regenerative medicine. We recently demonstrated that HUCBM cell transplantation improves histological alterations and function of the liver in rats with acute liver damage induced by D-galactosamine. In the present study, HUCBM cells were transplanted into rats with thioacetamide (TAA)-induced liver cirrhosis, an experimental model that generates an intense fibrosis and mimics the histological and biochemical alterations found in the human disease. HUCBM transplantation had no effect on hepatic histology of cirrhotic animals. In contrast, analysis of plasma albumin and total bilirubin, liver damage markers, revealed a harmful effect of HUCBM cell transplantation in our experimental model of liver cirrhosis. Significantly higher plasma urea concentrations, marker of renal function, were observed in the cirrhotic and control rats intraportally injected with HUCBM cells than in those not receiving this therapy. Histological study revealed tubular and glomerular lesions in kidneys of cirrhotic animals transplanted with HUCBM cells. The glomeruli appeared ischemic, and the tubules showed a severe involvement that included peripheral asymmetric vacuolization and disappearance of the tubular lumen. Taken together, the histological and biochemical data suggest that the cirrhotic rats subjected to HUCBM cell therapy developed a hepatorenal syndrome.

Xenotransplantation of Human Umbilical Cord Blood Mononuclear Cells to Rats with D-Galactosamine-Induced Hepatitis

Cord blood is an attractive cell source in regenerative medicine and represents an alternative to bone marrow. The aim of this study was to investigate whether human umbilical cord blood mononuclear (HUCBM) cells might be valuable in hepatic regenerative medicine. HUCBM cells differentiated in vitro into hepatocytes, as suggested by expression of albumin, cytokeratin-18, glutamine synthetase, α-fetoprotein, and cytochrome P450 3A4 at both mRNA and protein levels in a time-dependent fashion. In contrast, the hematopoietic phenotype was gradually lost, as demonstrated by disappearance of CD45 expression. The regenerative potential of HUCBM cells was tested by using a human-to-rat xenotransplant model in which HUCBM cells were intraportally injected into rats with D-galactosamine-induced hepatitis. Liver histology and biochemical markers of hepatic damage were determined. Presence of human cells was detected in blood and liver of both control and D-galactosamine-treated animals. Cell transplantation produced an improvement in both the histological damage and liver function, as demonstrated by plasma values of alkaline phosphatase, γ-glutamyl transferase, lactate dehydrogenase, and total and direct bilirubins. Results obtained suggest that HUCBM cells are capable of hepatic engraftment in this human-to-rat xenotransplant model and that transplantation of HUCBM cells may be a suitable therapy for liver disease.

Exogenous nucleosides modulate the expression of rat liver extracellular matrix genes in single cultures of primary hepatocytes and a liver stellate cell line and in their co-culture

BACKGROUND & AIMS

We have previously reported the antifibrotic effect of dietary nucleotides in cirrhotic rats. In this work, we used primary rat hepatocytes, a liver stellate cell line (CFSC-2G) and co-cultures of both cell types to investigate the effects of exogenous nucleosides on the gene expression of various extracellular matrix components and on markers of liver function, and to ascertain whether the effects found in vivo are due to CFSC-2G, hepatocytes, or are the consequence of cell-cell interactions.

RESULTS

Nucleosides enhanced fibronectin, laminin, and alpha1(I) procollagen levels in CFSC-2G and hepatocytes, as well as collagen synthesis and secretion in CFSC-2G. In contrast, nucleosides lowered fibronectin, laminin and alpha1(I) procollagen levels, and decreased collagen synthesis in co-cultures. Matrix metalloproteinase-13 content and collagen secretion increased in co-cultures incubated with nucleosides. Albumin increased in hepatocytes and co-cultures incubated in the presence of nucleosides.

CONCLUSIONS

Nucleosides modulate the production of extracellular matrix in single cultures of hepatocytes and of CFSC-2G, and in co-cultures. This effect seems to be regulated at the translational level. The opposite behavior of single cultures and co-cultures is probably due to the fact that the latter model reproduces many of the physical and functional relationships observed in vivo between hepatocytes and stellate cells.