Improvement of Infusion Process in Cell Transplantation: Effect of Shear Stress on Hepatocyte Viability Under Horizontal and Vertical Syringe Orientation

Parallelized Droplet Vitrification Enables Single-Run Vitrification of the Whole Rat Liver Hepatocyte Yield

Drug discovery pipelines rely on the availability of isolated primary hepatocytes for investigating potential hepatotoxicity prior to clinical application. These hepatocytes are typically isolated from livers rejected for transplantation and subsequently cryopreserved for later usage. The gold-standard cryopreservation technique, slow-freezing, is a labor-intensive process, with significant post-storage viability loss. In this work, we introduce parallelized droplet vitrification, a technique for high-volumetric, rapid vitrification of suspended cells. We show the utility of this technique through the single-run vitrification of the whole-rate liver hepatocyte yield, resulting in a 1600% increase in single-batch vitrification and a 500% increase in droplet generation rate compared to previous droplet vitrification approaches. Additionally, we showed that these implementations maintained improved post-preservation outcomes in primary rat hepatocytes.

Cotransplantation With Adipose Tissue-derived Stem Cells Improves Engraftment of Transplanted Hepatocytes

BACKGROUND

Hepatocyte transplantation is expected to be an alternative therapy to liver transplantation; however, poor engraftment is a severe obstacle to be overcome. The adipose tissue-derived stem cells (ADSCs) are known to improve engraftment of transplanted pancreatic islets, which have many similarities to the hepatocytes. Therefore, we examined the effects and underlying mechanisms of ADSC cotransplantation on hepatocyte engraftment.

METHODS

Hepatocytes and ADSCs were cotransplanted into the renal subcapsular space and livers of syngeneic analbuminemic rats, and the serum albumin level was quantified to evaluate engraftment. Immunohistochemical staining and fluorescent staining to trace transplanted cells in the liver were also performed. To investigate the mechanisms, cocultured supernatants were analyzed by a multiplex assay and inhibition test using neutralizing antibodies for target factors.

RESULTS

Hepatocyte engraftment at both transplant sites was significantly improved by ADSC cotransplantation ( P < 0.001, P < 0.001). In the renal subcapsular model, close proximity between hepatocytes and ADSCs was necessary to exert this effect. Unexpectedly, ≈50% of transplanted hepatocytes were attached by ADSCs in the liver. In an in vitro study, the hepatocyte function was significantly improved by ADSC coculture supernatant ( P < 0.001). The multiplex assay and inhibition test demonstrated that hepatocyte growth factor, vascular endothelial growth factor, and interleukin-6 may be key factors for the abovementioned effects of ADSCs.

CONCLUSIONS

The present study revealed that ADSC cotransplantation can improve the engraftment of transplanted hepatocytes. This effect may be based on crucial factors, such as hepatocyte growth factor, vascular endothelial growth factor, and interleukin-6, which are secreted by ADSCs.

Improvement of hepatocyte engraftment by co-transplantation with pancreatic islets in hepatocyte transplantation

Because of the fragility of isolated hepatocytes, extremely poor engraftment of transplanted hepatocytes remains a severe issue in hepatocyte transplantation. Therefore, improving hepatocyte engraftment is necessary to establish hepatocyte transplantation as a standard therapy. Since the pancreatic islets are known to have favorable autocrine effects, we hypothesized that the transplanted islets might influence not only the islets but also the nearby hepatocytes, subsequently promoting engraftment. We evaluated the effects of islet co-transplantation using an analbuminemic rat model (in vivo model). Furthermore, we established a mimicking in vitro model to investigate the underlying mechanisms. In an in vivo model, the hepatocyte engraftment was significantly improved only when the islets were co-transplanted to the nearby hepatocytes (p < 0.001). Moreover, the transplanted hepatocytes appeared to penetrate the renal parenchyma together with the co-transplanted islets. In an in vitro model, the viability of cultured hepatocytes was also improved by coculture with pancreatic islets. Of particular interest, the coculture supernatant alone could also exert beneficial effects comparable to islet coculture. Although insulin, VEGF, and GLP-1 were selected as candidate crucial factors using the Bio-Plex system, beneficial effects were partially counteracted by anti-insulin receptor antibodies. In conclusion, this study demonstrated that islet co-transplantation improves hepatocyte engraftment, most likely due to continuously secreted crucial factors, such as insulin, in combination with providing favorable circumstances for hepatocyte engraftment. Further refinements of this approach, especially regarding substitutes for islets, could be a promising strategy for improving the outcomes of hepatocyte transplantation.

Holistic characterization of single-hepatocyte transcriptome responses to high-fat diet

During nutritional overload and obesity, hepatocyte function is grossly altered, and a subset of hepatocytes begins to accumulate fat droplets, leading to nonalcoholic fatty liver disease (NAFLD). Recent single-cell studies revealed how nonparenchymal cells, such as macrophages, hepatic stellate cells, and endothelial cells, heterogeneously respond to NAFLD. However, it remains to be characterized how hepatocytes, the major constituents of the liver, respond to nutritional overload in NAFLD. Here, using droplet-based, single-cell RNA sequencing (Drop-seq), we characterized how the transcriptomic landscape of individual hepatocytes is altered in response to high-fat diet (HFD) and NAFLD. We showed that the entire hepatocyte population undergoes substantial transcriptome changes upon HFD, although the patterns of alteration were highly heterogeneous, with zonation-dependent and -independent effects. Periportal (zone 1) hepatocytes downregulated many zone 1-specific marker genes, whereas a small number of genes mediating gluconeogenesis were upregulated. Pericentral (zone 3) hepatocytes also downregulated many zone 3-specific genes; however, they upregulated several genes that promote HFD-induced fat droplet formation, consistent with findings that zone 3 hepatocytes accumulate more lipid droplets. Zone 3 hepatocytes also upregulated ketogenic pathways as an adaptive mechanism to HFD. Interestingly, many of the top HFD-induced genes, which encode proteins regulating lipid metabolism, were strongly co-expressed with each other in a subset of hepatocytes, producing a variegated pattern of spatial co-localization that is independent of metabolic zonation. In conclusion, our data set provides a useful resource for understanding hepatocellular alteration during NAFLD at single cell level.

Method and Apparatus for the Automated Delivery of Continuous Neural Stem Cell Trails Into the Spinal Cord of Small and Large Animals

BACKGROUND

Immature neurons can extend processes after transplantation in adult animals. Neuronal relays can form between injected neural stem cells (NSCs) and surviving neurons, possibly improving recovery after spinal cord injury (SCI). Cell delivery methods of single or multiple bolus injections of concentrated cell suspensions thus far tested in preclinical and clinical experiments are suboptimal for new tract formation. Nonuniform injectate dispersal is often seen due to gravitational cell settling and clumping. Multiple injections have additive risks of hemorrhage, parenchymal damage, and cellular reflux and require additional surgical exposure. The deposition of multiply delivered cells boluses may be uneven and discontinuous.

OBJECTIVE

To develop an injection apparatus and methodology to deliver continuous cellular trails bridging spinal cord lesions.

METHODS

We improved the uniformity of cellular trails by formulating NSCs in hyaluronic acid. The TrailmakerTM stereotaxic injection device was automatized to extend a shape memory needle from a single-entry point in the spinal cord longitudinal axis to "pioneer" a new trail space and then retract while depositing an hyaluronic acid-NSC suspension. We conducted testing in a collagen spinal models, and animal testing using human NSCs (hNSCs) in rats and minipigs.

RESULTS

Continuous surviving trails of hNSCs within rat and minipig naive spinal cords were 12 and 40 mm in length. hNSC trails were delivered across semi-acute contusion injuries in rats. Transplanted hNSCs survived and were able to differentiate into neural lineage cells and astrocytes.

CONCLUSION

The TrailmakerTM creates longitudinal cellular trails spanning multiple levels from a single-entry point. This may enhance the ability of therapeutics to promote functional relays after SCI.

The Optimization of Short-Term Hepatocyte Preservation Before Transplantation

Background

No optimal methods for short-term hepatocyte preservation have been established. We have recently developed a prominent oxygen-permeable bag (Tohoku Device [TD]) for pancreatic islet culture and transplantation. In this study, we investigated whether TD is also effective for hepatocyte preservation and tried to optimize other conditions.

Methods

Hepatocytes were preserved in the following conditions, and their outcomes were observed. First, the effectiveness of TD was investigated. Second, hepatocyte medium (HM) and organ preservation solutions with or without fetal bovine serum (FBS) were compared. Third, as supplementations, FBS and human serum albumin (HSA) were compared. Fourth, low, room and high temperature were compared. And finally, hepatocytes preserved in various conditions were transplanted into the subrenal capsule space of nonalbumin rats and engrafted areas were assessed.

Results

The survival rate of hepatocytes preserved in TD tended to be higher and their viability and function were maintained significantly greater than those of non-TD group. Irrespective of FBS supplementation, the survival rate of HM group was significantly higher than those of organ preservation solution group while viabilities and plating efficiency were similar among them. Although survival rates of groups without FBS were extremely low, results of HSA supplemented group were not inferior to FBS supplemented group. Hepatocytes preserved at high temperature had the worst results. The engrafted area of TD group tended to be higher than those of other groups.

Conclusions

TD is effective for short-term hepatocyte preservation. HSA is a useful substitute for FBS, and preserving in HM at low temperature is recommended.