Three-dimensional Reconstruction of the Vascular Architecture of the Passive CLARITY-cleared Mouse Ovary

Spatiotemporal observations of host-pathogen interactions in mucosa during SARS-CoV-2 infection indicate a protective role of ILC2s

IMPORTANCE

Our study revealed the spatial interaction between humanized ACE2 and pseudovirus expressing Spike, emphasizing the role of type 2 innate lymphoid cells during the initial phase of viral infection. These findings provide a foundation for the development of mucosal vaccines and other treatment approaches for both pre- and post-infection management of coronavirus disease 2019.

Conventional histomorphometry and fast free of acrylamide clearing tissue (FACT) visualization of sciatic nerve in chicken (Gallus domesticus)

Histomorphometry and use of the fast free of acrylamide clearing tissue (FACT) protocol were studied on the sciatic nerve in chicken (Gallus domesticus). In the first part of the study, the sciatic nerves of 20 chickens of four age groups (7, 14, 26 and 40 days) were studied (n=5 birds per age class). Their sciatic nerve samples were stained with Hematoxylin and Eosin and Masson's trichrome and were histomorphometrically evaluated. In the second part of the study, FACT protocol was applied on the sciatic nerve of a 26 days old chicken. After clearing of 1.00 mm-thick sciatic nerve sections, they were immunolabelled using Hoechst for nuclei staining and recorded by a Z-stack motorized fluorescent microscope. In the conventional histo-morphometry, the epineurium, perineurium and endoneurium were thicker and the nerve bundle diameter was bigger in the left sciatic nerve of chicken of all age groups compared to the right sciatic nerve. On the contrary, the axon diameter and the myelinated nerve fiber diameter were bigger, the myelin sheath was thicker, the nodes of Ranvier intervals were higher and the density of myelinated nerve fibers was also higher in the right sciatic nerve compared to the left one. In conclusion, histomorphometric parameters in the left and right sciatic nerve during chicken growth were significantly different. Furthermore, the FACT protocol could be used for the 3D imaging of the chicken sciatic nerve and its immunostained evaluation.

Three-Dimensional Imaging in Stem Cell-Based Researches

Stem cells have an important role in regenerative therapies, developmental biology studies and drug screening. Basic and translational research in stem cell technology needs more detailed imaging techniques. The possibility of cell-based therapeutic strategies has been validated in the stem cell field over recent years, a more detailed characterization of the properties of stem cells is needed for connectomics of large assemblies and structural analyses of these cells. The aim of stem cell imaging is the characterization of differentiation state, cellular function, purity and cell location. Recent progress in stem cell imaging field has included ultrasound-based technique to study living stem cells and florescence microscopy-based technique to investigate stem cell three-dimensional (3D) structures. Here, we summarized the fundamental characteristics of stem cells via 3D imaging methods and also discussed the emerging literatures on 3D imaging in stem cell research and the applications of both classical 2D imaging techniques and 3D methods on stem cells biology.

Three-dimensional and two-dimensional relationships of gangliogenesis with folliculogenesis in mature mouse ovary: a Golgi-Cox staining approach

The present study was set out to investigate two-dimensional (2D) and three-dimensional (3D) evaluations of ovarian nervous network development and the structural relationship between folliculogenesis and gangliogenesis in mouse ovaries. Adult mice ovarian tissue samples were collected from follicular and luteal phases after cardiac perfusion. Ovarian samples were stained by a Golgi-Cox protocol. Following staining, tissues were serially sectioned for imaging. Neural filaments and ganglia were present in the ovaries. In both 2D and 3D studies, an increase in the number and area of ganglia was seen during the follicular growth. The same pattern was also seen in corpora lutea development. However, in some cases such as ratio of ganglia number to follicle area, the ratio of ganglia area to follicular area, 2D findings were different compared with the 3D results. 3D analysis of ovarian gangliogenesis showed the possible direct effect of them on folliculogenesis. Golgi-Cox staining was used in this study for 3D evaluation in non-brain tissue. The results of 3D analysis of the present study showed that, in some cases, the information provided by 2D analysis does not match the reality of ovarian neuronal function. This confirmed the importance of 3D analysis for evaluation of ovarian function.

Spatial and temporal changes in follicle distribution in the human ovarian cortex

RESEARCH QUESTION

How does follicle distribution evolve in the human ovarian cortex between the ages of 20 and 35 years?

DESIGN

Fragments of ovarian cortex from women undergoing unilateral oophorectomy for fertility preservation were obtained for quantitative histological assessment, including recording the two-dimensional coordinates of the follicles. Data were analysed using spatial statistical methods.

RESULTS

A total of 53 ovarian cortex tissue samples, containing 1-803 follicles each, were obtained from 14 women aged 20-35 years. Primordial and transitory follicles lay in a clustered manner in the human ovarian cortex, with an average cluster radius of around 270 µm (95% confidence interval 154-377 µm; n = 49). Follicle density declined with age (P = 0.006, n = 13), and the distance from the nearest neighbouring follicle increased (P = 0.004, n = 13). Cluster radius decreased with age (P = 0.02, n = 13), but the degree of clustering tended to increase (P = 0.11, n = 13). In the majority of the samples, follicles at different stages lay in different clusters (P < 0.05, n = 13).

CONCLUSIONS

This study shows that primordial and transitory follicles lie in different clusters in the human ovarian cortex. Spatio-temporal computer simulation suggests that interfollicular signals may hinder follicle loss and may therefore drive clustered follicle distribution. In clinical practice, the woman's age should be taken into account when assessing follicle density, as follicle distribution is increasingly clustered with advancing age.

FACT or PACT: A Comparison between Free-Acrylamide and Acrylamide-Based Passive Sodium Dodecyl Sulfate Tissue Clearing for whole Tissue Imaging

Major biological processes rely on the spatial organization of cells in complex, highly orchestrated three-dimensional (3D) tissues. Until the recent decade, most of information on spatial neural representation primarily came from microscopic imaging of “2D” (5-50 μm) tissue using traditional immunohistochemical techniques. However, serially sectioned and imaged tissue sections for tissue visualization can lead to unique non-linear deformations, which dramatically hinders scientists’ insight into the structural organization of intact organs. An emerging technique known as CLARITY renders large-scale biological tissues transparent for 3D phenotype mapping and thereby, greatly facilitates structure-function relationships analyses. Since then, numerous modifications and improvements have been reported to push the boundaries of knowledge on tissue clearing techniques in research on assembled biological systems. This review aims to outline our current knowledge on next-generation protocols of fast free-of-acrylamide clearing tissue (FACT) and passive CLARITY (PACT). The most important question is what method we should select for tissue clearing, FACT or PACT. This review also highlights how FACT differs from PACT on spanning multiple dimensions of the workflow. We systematically compared a number of factors including hydrogel formation, clearing solution, and clearing temperatures between free-acrylamide and acrylamide-based passive sodium dodecyl sulfate (SDS) tissue clearing and discussed negative effects of polyacrylamide on clearing, staining, and imaging in detail. Such information may help to gain a perspective for interrogating neural circuits spatial interactions between molecules and cells and provide guidance for developing novel tissue clearing strategies to probe deeply into intact organ.

A Simple Technique for Three-Dimensional Imaging and Segmentation of Brain Vasculature U sing Fast Free-of-Acrylamide Clearing Tissue in Murine

Objective

Fast Free-of-Acrylamide Clearing Tissue (FACT) is a recently developed protocol for the whole tissue three-dimensional (3D) imaging. The FACT protocol clears lipids using sodium dodecyl sulfate (SDS) to increase the penetration of light and reflection of fluorescent signals from the depth of cleared tissue. The aim of the present study was using FACT protocol in combination with imaging of auto-fluorescency of red blood cells in vessels to image the vasculature of a translucent mouse tissues.

Materials and Methods

In this experimental study, brain and other tissues of adult female mice or rats were dissected out without the perfusion. Mice brains were sliced for vasculature imaging before the clearing. Brain slices and other whole tissues of rodent were cleared by the FACT protocol and their clearing times were measured. After 1 mm of the brain slice clearing, the blood vessels containing auto-fluorescent red blood cells were imaged by a z-stack motorized epifluorescent microscope. The 3D structures of the brain vessels were reconstructed by Imaris software.

Results

Auto-fluorescent blood vessels were 3D imaged by the FACT in mouse brain cortex. Clearing tissues of mice and rats were carried out by the FACT on the brain slices, spinal cord, heart, lung, adrenal gland, pancreas, liver, esophagus, duodenum, jejunum, ileum, skeletal muscle, bladder, ovary, and uterus.

Conclusion

The FACT protocol can be used for the murine whole tissue clearing. We highlighted that the 3D imaging of cortex vasculature can be done without antibody staining of non-perfused brain tissue, rather by a simple auto- fluorescence.

Skeletal Muscle CLARITY: A Preliminary Study of Imaging The Three-Dimensional Architecture of Blood Vessels and Neurons

Objective

Passive CLARITY is a whole-tissue clearing protocol, based on sodium dodecyl sulfate (SDS) clearing, for imaging intact tissue containing transgenic or immunolabeled fluorescent proteins. In this study, we present an improved passive CLARITY protocol with efficient immunolabeling without the need for electrophoresis or complex instrumentation.

Materials and Methods

In this experimental study, after perfusion of C57BL/6N mice with phosphate-buffered saline (PBS) and then with acrylamide-paraformaldehyde (PFA), the quadriceps femoris muscle was removed. The muscle samples were post-fixed and degassed to initiate polymerization. After removing the excess hydrogel around the muscle, lipids were washed out with the passive CLARITY technique. The transparent whole intact muscles were labeled for vessel and neuron markers, and then imaged by confocal microscopy. Three-dimensional images were reconstructed to present the muscle tissue architecture.

Results

We established a simple clearing protocol using wild type mouse muscle and labeling of vasculatures and neurons. Imaging the fluorescent signal was achieved by protein fixation, adjusting the pH of the SDS solution and using an optimum temperature (37˚C) for tissue clearing, all of which contributed to the superiority of our protocol.

Conclusion

We conclude that this passive CLARITY protocol can be successfully applied to three-dimensional cellular and whole muscle imaging in mice, and will facilitate structural analyses and connectomics of large assemblies of muscle cells, vessels and neurons in the context of three-dimensional systems.