Multiplexing and Spectral Microscopy

Visualization of proteins within a tissue sample via immunohistochemistry (IHC) is a central aspect of pathology. However, such methods are limited to the detection of one or two proteins, due to the overlapping absorption/emission spectra of chromogens and fluorescent dyes. The advent of spectral microscopy has enabled improved visualization of multiple proteins by allowing for the specific light wavelengths/spectral signatures of individual fluorophores and chromogens to be unmixed and analyzed, thus detecting signals that would be indistinguishable with conventional microscopy. Combined with improvements to multiplexed immunohistochemistry (mIHC) protocols, spectral microscopy facilitates the interrogation of spatial relationships between four (enzymatic mIHC) or seven (fluorescent mIHC) proteins, unlocking the wealth of information contained within a single tissue section. Furthermore, the application of linear unmixing for image analysis allows for a reduction in background signal associated with tissue autofluorescence and can distinguish chromogens with similar absorption spectra to identify protein colocalization in brightfield spectral microscopy. While many mIHC protocols have been optimized for spectral microscopy, this chapter will focus in detail on two common methods: enzymatic mIHC and manual fluorescent mIHC using tyramide signal amplification and microwave technology.

Scaffolds for Intracerebral Grafting of Neural Progenitor Cells After Cerebral Infarction: A Systematic Review

Context

Intracerebral grafting of neural progenitor cells is a promising potential treatment to improve recovery after stroke, but the structural disruption and cavitation of brain tissue that occurs creates an unfavorable environment for graft cell survival. To overcome this obstacle, scaffold materials have been used as extracellular matrix to provide structural support for the transplanted cells. Many materials could potentially be used as scaffolds for this application.

Evidence Acquisition

We performed a systematic review to determine the available evidence supporting specific scaffolds for neural progenitor cell grafting after stroke. Articles were identified with a MeSH search on PubMed. Relevant references and “related articles” of selected manuscripts were also reviewed. Full original articles published prior to May 2013 presenting unique experimental data describing intracerebral grafting of neural progenitor cells in a scaffold after cerebral infarction were included in our study. All selected articles were reviewed thoroughly by the authors for relevant data.

Results

We found reports of use of scaffolds composed of polyglycolic acid, poly [lactic-co-glycolic acid] particles (with and without VEGF), hyaluronan-heparin-collagen hydrogel, Matrigel, collagen and extracellular matrix derived from porcine brain and urinary bladder. While multiple beneficial effects were reported, the optimal scaffold is unclear as we found no direct comparisons.

Conclusions

We conclude that multiple scaffolds appear promising for neural progenitor cell grafting after stroke, but further research is needed to optimize this neurorestorative approach. Thus, we hope to provide a basic understanding of the state of scaffolds for neural progenitor cell grafting after stroke and to encourage further research. Based on the methods of the discussed studies, we propose a standardized set of outcomes that would best be used to evaluate and compare the effectiveness of a given scaffold.

Autoantibodies in Human Diabetic Depression Inhibit Adult Neural Progenitor Cells In vitro and Induce Depressive-Like Behavior in Rodents

AIM

Diabetic depression increases in association with microvascular complications. We tested a hypothesis that circulating autoantibodies having anti-endothelial and anti-neuronal properties increase in subsets of diabetes with co-morbid depression.

METHODS

Protein-A eluates from plasma of 20 diabetic depression patients and 30 age-matched controls were tested for effects on endothelial cell survival, neurite outgrowth in rat pheochromocytoma (PC12) cells, or process extension and survival in adult rat dentate gyrus neural progenitor cells. The protein-A eluates from depressed or non-depressed, diabetic patients were injected (via intracerebroventricular route) into mice and 7-10 days later behavioral tests (sucrose preference, and tail suspension tests) were conducted to determine whether the autoantibodies induced anhedonia or despair.

RESULTS

Diabetic depression (n=20) autoantibodies caused a significant inhibition of PC12 cell neurite outgrowth (P<0.001) or endothelial cell proliferation compared to autoantibodies in control, diabetic (n=20) or non-diabetic (n=10) patients without depression. Process extension and survival in adult rat dentate gyrus neural progenitor cells was significantly reduced (P<0.001) by diabetic depression autoantibodies (n= 11) compared to the effects from similar concentrations (5-7 μg/mL) of autoantibodies in diabetic (n=12) or non-diabetic patients without depression (n=7). Ten micromolar concentrations of Y27632, a selective Rho-Associated Protein Kinase (ROCK) inhibitor, significantly prevented (P<0.0001) neural progenitor cell process retraction induced by diabetes depression autoantibodies (n=5). Mice treated with diabetic depression autoantibodies (n=16 from two different patients' autoantibodies) exhibited significantly reduced (P=0.027) sucrose preference (anhedonia) compared to mice treated with diabetic control autoantibodies (n=16 from two different patients' autoantibodies).

CONCLUSION

These data suggest that autoantibodies in a subset of older adult diabetic depression inhibit endothelial cell survival, and impair process extension and survival in adult dentate gyrus neural progenitor cells in vitro.