A modified Spalteholz technique with preservation of the histology

Tissue clearing and imaging approaches for in toto analysis of the reproductive system

New microscopy techniques in combination with tissue clearing protocols and emerging analytical approaches have presented researchers with the tools to understand dynamic biological processes in a three-dimensional context. This paves the road for the exploration of new research questions in reproductive biology, for which previous techniques have provided only approximate resolution. These new methodologies now allow for contextualized analysis of far larger volumes than was previously possible. Tissue optical clearing and three-dimensional imaging techniques posit the bridging of molecular mechanisms, macroscopic morphogenic development, and maintenance of reproductive function into one cohesive and comprehensive understanding of the biology of the reproductive system. In this review, we present a survey of the various tissue clearing techniques and imaging systems, as they have been applied to the developing and adult reproductive system. We provide an overview of tools available for analysis of experimental data, giving particular attention to the emergence of AI-assisted methods and their applicability to image analysis. We conclude with an evaluation of how novel image analysis approaches which have been applied to other organ systems could be incorporated into future experimental evaluation of reproductive biology.

A Method to Visualize and Quantify the Intraosseous Arteries of the Femoral Head by Vascular Corrosion Casting

OBJECTIVE

To describe a method to display the three-dimensional distribution of intraosseous arteries in the femoral head by vascular corrosion casting.

METHODS

An experimental study was done to expose the intraosseous arteries of the femoral head by a microperfusion corrosion method between January 2021 and May 2021. Specimens were 23 swine femoral heads (12 female specimens and 11 male specimens, where age of swine ranged from 8 to 12 months, and the weight was approximately 150 kg). The femoral heads were microperfused with the vascular casting resin through retinacular arteries, and the bone of the femoral head was dissolved with 50% sodium hydroxide and 10% hydrochloric acid and rinsed under the microscope until the vessel casts were completely exposed. The distribution and anastomosis of the arteries in the femoral head were observed under direct vision and microscopy. The diameter of the artery in the femoral head was measured at 0.5 cm after its entry into the bone of the femoral head with a microscale under the microscope. The number of internal arteries with diameter ≥0.05 mm was counted. The number and diameter of the main trunk of the epiphyseal arteries in the femoral head between male and female swine were compared.

RESULTS

The vascular casting specimen of the swine femoral head was successfully produced by using epoxy resin as a casting agent, and the three-dimensional intraosseous vascular structures were clearly visible. The number of epiphyseal arteries in male and female swine was 8.55 ± 2.15 and 8.83 ± 2.15 (t = -0.31, p = 0.38), respectively. The diameters of the superior epiphyseal arteries in male and female swine were 0.35 ± 0.09 and 0.31 ± 0.08 mm (t = 1.03, p = 0.16), the diameters of the inferior epiphyseal arteries were 0.47 ± 0.05 and 0.49 ± 0.09 mm (t = -0.57, p = 0.29), and the diameters of the anterior epiphyseal arteries were 0.34 ± 0.08 and 0.33 ± 0.13 mm (t = 0.32, p = 0.37). There was no significant difference in the number and diameter of the main trunk of intraosseous arteries between male and female swine (p > 0.05). The main trunk of intraosseous arteries formed an anastomosis in the center of the femoral head. Among 23 swine femoral head samples, three types of intraosseous anastomosis were observed, including 13 (57%) posterior superior-posterior inferior, seven (30%) posterior inferior-anterior, and three (13%) uniform intraosseous anastomosis.

CONCLUSION

The microperfusion corrosion method can produce the vascular casting specimen of swine femoral head revealing the three-dimensional structure of the intraosseous artery, which clearly shows the origin, course and branches, and diameter, as well as the anastomosis, of nutrient arteries in the femoral head. This method provides a simple and rapid technique for quantifying and visualizing intraosseous arteries.

A fast, aqueous, reversible three-day tissue clearing method for adult and embryonic mouse brain and whole body

Optical clearing methods serve as powerful tools to study intact organs and neuronal circuits. We developed an aqueous clearing protocol, Fast 3D Clear, that relies on tetrahydrofuran for tissue delipidation and iohexol for clearing, such that tissues can be imaged under immersion oil in light-sheet imaging systems. Fast 3D Clear requires 3 days to achieve high transparency of adult and embryonic mouse tissues while maintaining their anatomical integrity and preserving a vast array of transgenic and viral/dye fluorophores. A unique advantage of Fast 3D Clear is its complete reversibility and thus compatibility with tissue sectioning and immunohistochemistry. Fast 3D Clear can be easily and quickly applied to a wide range of biomedical studies, facilitating the acquisition of high-resolution two- and three-dimensional images.

Avoiding the blood supply to the femoral head during cannulated screw fixation: A comparison of two techniques

Objectives

To compare the strength of the inverted triangle (IT) versus the L-shaped cannulated screw fixation technique for stabilizing a Pauwels 2 femoral neck fracture. To demonstrate the risk to the blood supply to the femoral head from a posterior-superior screw.

Methods

The IT construct was compared with the L-shaped design in 10 composite femurs. A Pauwels 2 fracture was made with a 5 mm gap. Each specimen was loaded over 5000 cycles, measuring angular/shear displacement then loaded to failure. The data were analyzed using Mann-Whitney U test. Three separate fresh frozen cadavers were injected with low-viscosity epoxy. The intraosseous bloody supply was inspected in each femoral head (no fixation, IT, L-shaped).

Results

There was no difference in angular (P = .3) or shear displacement (P = .99) between either screw design after cyclical loading. Also, there was not statistical difference in load to failure testing between either construct (P = .99). The average load to failure in the IT group was 3204.4 N. The average was 3180.2 N in the L-shaped design. We demonstrated the presence of the intraosseous portion of the lateral epiphyseal vessel in the specimen without screw fixation. This was preserved in the specimen with the L-shaped design but absent in the specimen following IT fixation.

Conclusions

The strength of the L-shaped construct was not statistically different than the strength of the IT design. The posterior-superior screw may put the main blood supply to the femoral head at risk and should be avoided.

Ovary Development: Insights From a Three-Dimensional Imaging Revolution

The ovary is an indispensable unit of female reproduction and health. However, the study of ovarian function in mammals is hindered by unique challenges, which include the desynchronized development of oocytes, irregular distribution and vast size discrepancy of follicles, and dynamic tissue remodeling during each hormonal cycle. Overcoming the limitations of traditional histology, recent advances in optical tissue clearing and three-dimensional (3D) visualization offer an advanced platform to explore the architecture of intact organs at a single cell level and reveal new relationships and levels of organization. Here we summarize the development and function of ovarian compartments that have been delineated by conventional two-dimensional (2D) methods and the limits of what can be learned by these approaches. We compare types of optical tissue clearing, 3D analysis technologies, and their application to the mammalian ovary. We discuss how 3D modeling of the ovary has extended our knowledge and propose future directions to unravel ovarian structure toward therapeutic applications for ovarian disease and extending female reproductive lifespan.

Volumetric histological characterization of optic nerve degeneration using tissue clearing: literature review and practical study

Tissue clearing technologies can greatly improve the depth and accuracy with which the three-dimensional structure of tissues, especially those of the nervous system, can be visualized. A review of the present literature suggests that the growing diversity and sophistication of various approaches have contributed to the expansion of this method to a greater variety of tissue types, experimental conditions, and imaging modalities. In the proof-of-concept study presented in this paper, a simplified and modified version of the tissue clearing method CUBIC (clear, unobstructed brain imaging cocktails and computational analysis) was used in conjunction with fluorescent staining and immunohistochemistry to illustrate the three-dimensional structure and molecular characteristics of inflammatory and degenerative activity in the mouse optic nerve. Based on the studies summarized in this mini-review, and our impression from using the mCUBIC method, it appears that tissue clearing could be a viable approach revealing three-dimensional histological features of myelin-rich tissues under normal conditions and after injury.

Tissue Optical Clearing for Biomedical Imaging: From In Vitro to In Vivo

Tissue optical clearing technique provides a prospective solution for the application of advanced optical methods in life sciences. This chapter firstly gives a brief introduction to mechanisms of tissue optical clearing techniques, from the physical mechanism to chemical mechanism, which is the most important foundation to develop tissue optical clearing methods. During the past years, in vitro and in vivo tissue optical clearing methods were developed. In vitro tissue optical clearing techniques, including the solvent-based clearing methods and the hydrophilic reagents-based clearing methods, combined with labeling technique and advanced microscopy, can be applied to image 3D microstructure of tissue blocks or whole organs such as brain and spinal cord with high resolution. In vivo skin or skull optical clearing, promise various optical imaging techniques to detect cutaneous or cortical cell and vascular structure and function without surgical window.

A Simple Method for Generating, Clearing, and Imaging Pre-vascularized 3D Adipospheres Derived from Human iPS Cells

Beige/brite/brown-like adipocytes (BAs), dispersed in white adipose tissue, represent promising cell targets to counteract obesity and associated diseases. However, there are major limitations for a BA-based treatment of obesity, among which the main ones are the rareness of BAs in adult humans and the lack of a relevant cell culture condition for modeling the development of BAs. We describe in this chapter the capacity of human induced pluripotent stem cells-derived BA progenitors (hiPSC-BAPs) to self-organize in spheroids and a method for their differentiation at a high efficiency in hiPSC-derived 3D adipospheres containing UCP1-expressing cells. Enrichment of adipospheres with human dermal microvascular endothelial cells (HDMECs) allows to better mimic native adipose tissue. To observe the accumulation of lipid droplets, organization of the extracellular matrix and expression of adipogenic markers on the surface of hiPSC-adipospheres, we detail how to combine Oil Red O staining with immunostaining both imaged by fluorescence microscopy. Furthermore, to have a global view of pre-vascularized network formed by HDMECs inside of hiPSC-adipospheres, we describe a method which consists of the whole adipospheres fixation, multicolor immunostaining, clearing, and imaging.

3D Whole-Brain Imaging Approaches to Study Brain Tumors

Simple Summary

Brain tumors integrate into the brain and consist of tumor cells with different molecular alterations. During brain tumor pathogenesis, a variety of cell types surround the tumors to either inhibit or promote tumor growth. These cells are collectively referred to as the tumor microenvironment. Three-dimensional and/or longitudinal visualization approaches are needed to understand the growth of these tumors in time and space. In this review, we present three imaging modalities that are suitable or that can be adapted to study the volumetric distribution of malignant or tumor-associated cells in the brain. In addition, we highlight the potential clinical utility of some of the microscopy approaches for brain tumors using exemplars from solid tumors.

Abstract

Although our understanding of the two-dimensional state of brain tumors has greatly expanded, relatively little is known about their spatial structures. The interactions between tumor cells and the tumor microenvironment (TME) occur in a three-dimensional (3D) space. This volumetric distribution is important for elucidating tumor biology and predicting and monitoring response to therapy. While static 2D imaging modalities have been critical to our understanding of these tumors, studies using 3D imaging modalities are needed to understand how malignant cells co-opt the host brain. Here we summarize the preclinical utility of in vivo imaging using two-photon microscopy in brain tumors and present ex vivo approaches (light-sheet fluorescence microscopy and serial two-photon tomography) and highlight their current and potential utility in neuro-oncology using data from solid tumors or pathological brain as examples.

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.

Cellular and Molecular Probing of Intact Human Organs

Optical tissue transparency permits scalable cellular and molecular investigation of complex tissues in 3D. Adult human organs are particularly challenging to render transparent because of the accumulation of dense and sturdy molecules in decades-aged tissues. To overcome these challenges, we developed SHANEL, a method based on a new tissue permeabilization approach to clear and label stiff human organs. We used SHANEL to render the intact adult human brain and kidney transparent and perform 3D histology with antibodies and dyes in centimeters-depth. Thereby, we revealed structural details of the intact human eye, human thyroid, human kidney, and transgenic pig pancreas at the cellular resolution. Furthermore, we developed a deep learning pipeline to analyze millions of cells in cleared human brain tissues within hours with standard lab computers. Overall, SHANEL is a robust and unbiased technology to chart the cellular and molecular architecture of large intact mammalian organs.

Clearing techniques for visualizing the nervous system in development, injury, and disease

Modern clearing techniques enable high resolution visualization and 3D reconstruction of cell populations and their structural details throughout large biological samples, including intact organs and even entire organisms. In the past decade, these methods have become more tractable and are now being utilized to provide unforeseen insights into the complexities of the nervous system. While several iterations of optical clearing techniques have been developed, some are more suitable for specific applications than others depending on the type of specimen under study. Here we review findings from select studies utilizing clearing methods to visualize the developing, injured, and diseased nervous system within numerous model systems and species. We note trends and imbalances in the types of research questions being addressed with clearing methods across these fields in neuroscience. In addition, we discuss restrictions in applying optical clearing methods for postmortem tissue from humans and large animals and emphasize the lack in continuity between studies of these species. We aim for this review to serve as a key outline of available tissue clearing methods used successfully to address issues across neuronal development, injury/repair, and aging/disease.

In-vivo and ex-vivo optical clearing methods for biological tissues: review

Every optical imaging technique is limited in its penetration depth by scattering occurring in biological tissues. Possible solutions to overcome this problem consist of limiting the detrimental effects of scattering by reducing optical inhomogeneities within the sample. This can be achieved either by using physical methods (such as refractive index matching solutions) or by chemical methods (such as the removal of scatterers), based on tissue transformation protocols. This review provides an overview of the current state-of-the-art methods used for both ex-vivo and in-vivo optical clearing of biological tissues. We start with a brief history of the development of the most widespread clearing methods across the new millennium, then we describe the working principles of both physical and chemical methods. Clearing methods are then reviewed, pointing the attention of the reader on both physical and chemical methods, classified based on the tissue size and type for each specific application. A small section is reserved for methods that have already found in-vivo applications at the research level. Finally, a detailed discussion highlighting both the most relevant results achieved and the new ongoing developments in this field is reported in the last part, together with future perspectives for the clearing methodology.

On the importance of the innervation of the human cervical longitudinal ligaments at vertebral level

PURPOSE

In our aging society, the prevalence of degenerative spinal diseases rose drastically within the last years. However, up till now, the origin of cervical pain is incompletely understood. While animal and small cadaver studies indicate that a complex system of sensory and nociceptive nerve fibers in the anterior (ALL) and posterior longitudinal ligament (PLL) at the level of the intervertebral disc might be involved, there is a lack of data exploring whether such a network exists and is equally distributed within the cervical vertebrae (VB). We, therefore, aimed to investigate the spatial distribution of the mentioned nerve networks in human tissue.

METHODS

We performed macroscopic (Sihler staining, Spalteholz technique, and Plastination) and microscopic (immunohistochemistry for PGP 9.5 and CGRP) studies to characterize spatial differences in sensory and nociceptive innervation patterns. Therefore, 23 human body donors were dissected from level C3-C6.

RESULTS

We could show that there is a focal increase in sensory and nociceptive nerve fibers at the level of C4 and C5 for both ALL and PLL, while we observed less nerve fiber density at the level of C3 and C6. An anatomical vicinity between nerve and vessels was observed.

CONCLUSION

To our knowledge, these findings for the first time report spatial differences in sensory and nociceptive nerve fibers in the human cervical spine at VB level. The interconnection between nerves and vessels supports the importance of the perivascular plexus. These findings might be of special interest for clinical practice as many patients suffer from pain after cervical spine surgery.

Anatomic study on the blood supply to the femoral head following hip resurfacing using the posterior approach

OBJECTIVES

The aim of this study was to investigate femoral head perfusion following cadaveric hip resurfacing using the posterior approach.

METHODS

This cadaveric study involved injecting Higgins India ink into the common iliac arteries and evaluating the distribution of ink in the resurfaced heads using the modified Spalteholz technique. The study consisted of 2 parts. The 1st part involved utilisation of 22 cadaveric hips for establishing the injection and histological technique. The 2nd part of the study included 4 control cadaveric hips and 12 cadaveric hips with posterior approach hip resurfacing. Each specimen was divided into 15 zones (12 head zones and 3 neck zones) to evaluate detailed geographic distribution of dye-containing blood vessels.

RESULTS

All 4 controls had good flow of ink to all head zones and the neck region. In all the resurfaced heads, there was good flow to all the neck zones. 6 resurfaced specimens had no dye flow to any of the head zones. In the remaining 6, dye-stained vessels were seen variably in the anterior and middle zones but were consistently absent in the posterior zones of the head. Zones representing the antero-inferior parts of femoral head had the maximum flow of ink, followed by zones representing middle-inferior parts.

CONCLUSIONS

Posterior approach for hip resurfacing arthroplasty results in vascular insult to the femoral head, with posterior zones more affected than the anterior zones. The persistence of the dye in the intraosseous blood vessels of the neck and in anteroinferior head may be a source of revascularisation of the femoral head after posterior approach hip resurfacing.

Optimisation and validation of hydrogel-based brain tissue clearing shows uniform expansion across anatomical regions and spatial scales

Imaging of fixed tissue is routine in experimental neuroscience, but is limited by the depth of tissue that can be imaged using conventional methods. Optical clearing of brain tissue using hydrogel-based methods (e.g. CLARITY) allows imaging of large volumes of tissue and is rapidly becoming commonplace in the field. However, these methods suffer from a lack of standardized protocols and validation of the effect they have upon tissue morphology. We present a simple and reliable protocol for tissue clearing along with a quantitative assessment of the effect of tissue clearing upon morphology. Tissue clearing caused tissue swelling (compared to conventional methods), but this swelling was shown to be similar across spatial scales and the variation was within limits acceptable to the field. The results of many studies rely upon an assumption of uniformity in tissue swelling, and by demonstrating this quantitatively, research using these methods can be interpreted more reliably.

Optical clearing methods: An overview of the techniques used for the imaging of 3D spheroids

Spheroids have emerged as in vitro models that reproduce in a great extent the architectural microenvironment found in human tissues. However, the imaging of 3D cell cultures is highly challenging due to its high thickness, which results in a light-scattering phenomenon that limits light penetration. Therefore, several optical clearing methods, widely used in the imaging of animal tissues, have been recently explored to render spheroids with enhanced transparency. These methods are aimed to homogenize the microtissue refractive index (RI) and can be grouped into four different categories, namely (a) simple immersion in an aqueous solution with high RI; (b) delipidation and dehydration followed by RI matching; (c) delipidation and hyperhydration followed by RI matching; and (d) hydrogel embedding followed by delipidation and RI matching. In this review, the main optical clearing methods, their mechanism of action, advantages, and disadvantages are described. Furthermore, the practical examples of the optical clearing methods application for the imaging of 3D spheroids are highlighted.

Tissue Clearing and Its Application to Bone and Dental Tissues

Opaqueness of animal tissue can be attributed mostly to light absorption and light scattering. In most noncleared tissue samples, confocal images can be acquired at no more than a 100-µm depth. Tissue-clearing techniques have emerged in recent years in the neuroscience field. Many tissue-clearing methods have been developed, and they all follow similar working principles. During the tissue-clearing process, chemical or physical treatments are applied to remove components blocking or scattering the light. Finally, samples are immersed in a designated clearing medium to achieve a uniform refractive index and to gain transparency. Once the transparency is reached, images can be acquired even at several millimeters of depth with high resolution. Tissue clearing has become an essential tool for neuroscientists to investigate the neural connectome or to analyze spatial information of various types of brain cells. Other than neural science research, tissue-clearing techniques also have applications for bone research. Several methods have been developed for clearing bones. Clearing treatment enables 3-dimensional imaging of bones without sectioning and provides important new insights that are difficult or impossible to acquire with conventional approaches. Application of tissue-clearing technique on dental research remains limited. This review will provide an overview of the recent literature related to the methods and application of various tissue-clearing methods. The following aspects will be covered: general principles for the tissue-clearing technique, current available methods for clearing bones and teeth, general principles of 3-dimensional imaging acquisition and data processing, applications of tissue clearing on studying biological processes within bones and teeth, and future directions for 3-dimensional imaging.

Tissue clearing of both hard and soft tissue organs with the PEGASOS method

Tissue clearing technique enables visualization of opaque organs and tissues in 3-dimensions (3-D) by turning tissue transparent. Current tissue clearing methods are restricted by limited types of tissues that can be cleared with each individual protocol, which inevitably led to the presence of blind-spots within whole body or body parts imaging. Hard tissues including bones and teeth are still the most difficult organs to be cleared. In addition, loss of endogenous fluorescence remains a major concern for solvent-based clearing methods. Here, we developed a polyethylene glycol (PEG)-associated solvent system (PEGASOS), which rendered nearly all types of tissues transparent and preserved endogenous fluorescence. Bones and teeth could be turned nearly invisible after clearing. The PEGASOS method turned the whole adult mouse body transparent and we were able to image an adult mouse head composed of bones, teeth, brain, muscles, and other tissues with no blind areas. Hard tissue transparency enabled us to reconstruct intact mandible, teeth, femur, or knee joint in 3-D. In addition, we managed to image intact mouse brain at sub-cellular resolution and to trace individual neurons and axons over a long distance. We also visualized dorsal root ganglions directly through vertebrae. Finally, we revealed the distribution pattern of neural network in 3-D within the marrow space of long bone. These results suggest that the PEGASOS method is a useful tool for general biomedical research.

Blood Supply to the Integument of the Abdomen of the Rat: A Surgical Perspective

BACKGROUND

Many fundamental questions regarding the blood supply to the integument of the rat remain to be clarified, namely the degree of homology between rat and humans. The aim of this work was to characterize in detail the macro and microvascular blood supply to the integument covering the ventrolateral aspect of the abdominal wall of the rat.

METHODS

Two hundred five Wistar male rats weighing 250-350 g were used. They were submitted to gross anatomical dissection after intravascular colored latex injection (n = 30); conversion in modified Spalteholz cleared specimens (n=10); intravascular injection of a Perspex solution, and then corroded, in order to produce vascular corrosion casts of the vessels in the region (n = 5); histological studies (n = 20); scanning electron microscopy of vascular corrosion casts (n = 10); surgical dissection of the superficial caudal epigastric vessels (n = 100); and to thermographic evaluation (n = 30).

RESULTS

The ventrolateral abdominal wall presented a dominant superficial vascular system, which was composed mainly of branches from the superficial caudal epigastric artery and vein in the caudal half. The cranial half still received significant arterial contributions from the lateral thoracic artery in all cases and from large perforators coming from the intercostal arteries and from the deep cranial epigastric artery.

CONCLUSIONS

These data show that rats and humans present a great deal of homology regarding the blood supply to the ventrolateral aspect of the abdominal integument. However, there are also significant differences that must be taken into consideration when performing and interpreting experimental procedures in rats.

Vascular Structures of the Lateral Wall of the Maxillary Sinus: A Vascular Labeling Technique

PURPOSE

Sinus floor augmentation is a common procedure in implant dentistry. However, several intraoperative complications can occur during this procedure, such as bleeding from the lateral wall of the maxillary sinus. The aim of this study was to describe the vascular structures of the lateral wall of the maxillary sinus using a vascular labeling technique.

MATERIALS AND METHODS

Ten cadaveric specimens were prepared by the vascular labeling technique. Liquid latex was injected into the large vessels of the head, and the lateral wall of the maxillary sinus was exposed by dissection. The diameter of the vessels and their distance from the alveolar ridge (AR) were recorded.

RESULTS

Blood vessels could be observed in all the dissected specimens (100%). The mean distance from the lower edge of the blood vessels to the AR was 18.5 mm (SD 3.31 mm).

CONCLUSIONS

The vascular labeling technique detects maxillary sinus vessels in a predictable and effective way. These structures are clinically relevant because they are located in the area where the lateral window is usually created in sinus augmentation procedures and can cause profuse bleeding.

Optical clearing of the eye using the See Deep Brain technique

PurposeTissue clearing has been used in anatomy for the first time in Germany over a century ago. Neuronal tissue, like cortex, was investigated in mice using a water-based optical clearing method termed See Deep Brain (SeeDB). However, although the eye belongs to the central nervous system, this histological technique was not applied in the eye up to date. We applied SeeDB for the visualization of intraocular structures.Patients and methodsFour eyes of cornea donors (two male, two female: 73-84 years) obtained from the Cornea Bank of the Department of Ophthalmology Erlangen, four chicken eyes and two mices' optic nerve were used. Bulbi were fixed in 4% paraformaldehyde in phosphate-buffered saline and treated with increasing concentrations of aqueous fructose solution with 0.5% α-thioglycerol. After SeeDB, transscleral macrophotographs of the choroid were performed.ResultsComplete transparency of the sclera was obtained in enucleated human and chicken eyes after SeeDB treatment. Macroscopical anatomy of the choroid (partially transparent due to the remaining retinal pigment epithelium and melanocytes) showing vessels and other related structures was possible without preparing slides. Mice optic nerves were also transparent after SeeDB treatment.ConclusionThe SeeDB method allows visualization of intraocular structures through a completely translucent sclera. This innovative processing technique could facilitate comprehensive qualitative and quantitative topographical anatomical studies of human and animal eyes, preserving their 3D architecture. Supra- and intrachoroidal ganglionic plexus could potentially be visualized transsclerally. Finally, clinical-pathological correlations of intraocular diseases-for example, retinal tumors-will be possible in non-dissected eyes.

Vascular labeling of the head and neck vessels: Technique, advantages and limitations

Background

Vascular staining techniques have been used to describe the vascular structures of several anatomic areas. However, few reports have described this procedure in the head and neck region. This paper describes a head and neck vascular labeling procedure, and describes some of the technical complications that may occur.

Material and Methods

Fifteen specimen cadaver heads were prepared. After drying the vascular system, the internal carotid arteries were ligated and a solution with latex and a gelling agent was injected into the internal carotid arteries and external jugular veins. Two different colors were employed to differentiate arteries from veins. A total of 60ml latex was injected into each blood vessel. Subsequently, the specimens were refrigerated at 5°C for a minimum of 24 hours. Finally, a dissection was performed to identify the venous and arterial systems of the maxillofacial region.

Results

In most specimens, correct identification of the vascular structures (lingual artery, pterigoyd plexus, and the major palatal arteries, among others) was possible. However, in three heads a major technical problem occurred (the latex remained liquid), making the dissection unfeasible. Other minor complications such as latex obstruction due to the presence of atheromas were found in two further specimens.

Conclusions

The vascular labeling technique is a predictable, effective and simple method for analyzing the vascular system of the maxillofacial area in cadaveric studies, including vessels of reduced diameter or with an intraosseous course. This procedure can be especially useful to teach vascular anatomy to dental students and postgraduate residents.

Key words:Blood vessels, vascular casting, vascular labeling, head and neck arteries, carotid arteries, jugular veins.

Reflection imaging of China ink-perfused brain vasculature using confocal laser-scanning microscopy after clarification of brain tissue by the Spalteholz method

Confocal laser-scanning microscopy is a useful tool for visualizing neurons and glia in transparent preparations of brain tissue from laboratory animals. Currently, imaging capillaries and venules in transparent brain tissues requires the use of fluorescent proteins. Here, we show that vessels can be imaged by confocal laser-scanning microscopy in transparent cortical, hippocampal and cerebellar preparations after clarification of China ink-injected specimens by the Spalteholz method. This method may be suitable for global, three-dimensional, quantitative analyses of vessels, including stereological estimations of total volume and length and of surface area of vessels, which constitute indirect approaches to investigate angiogenesis.

A survey of clearing techniques for 3D imaging of tissues with special reference to connective tissue

For 3-dimensional (3D) imaging of a tissue, 3 methodological steps are essential and their successful application depends on specific characteristics of the type of tissue. The steps are 1° clearing of the opaque tissue to render it transparent for microscopy, 2° fluorescence labeling of the tissues and 3° 3D imaging. In the past decades, new methodologies were introduced for the clearing steps with their specific advantages and disadvantages. Most clearing techniques have been applied to the central nervous system and other organs that contain relatively low amounts of connective tissue including extracellular matrix. However, tissues that contain large amounts of extracellular matrix such as dermis in skin or gingiva are difficult to clear. The present survey lists methodologies that are available for clearing of tissues for 3D imaging. We report here that the BABB method using a mixture of benzyl alcohol and benzyl benzoate and iDISCO using dibenzylether (DBE) are the most successful methods for clearing connective tissue-rich gingiva and dermis of skin for 3D histochemistry and imaging of fluorescence using light-sheet microscopy.

Advanced CUBIC protocols for whole-brain and whole-body clearing and imaging

Here we describe a protocol for advanced CUBIC (Clear, Unobstructed Brain/Body Imaging Cocktails and Computational analysis). The CUBIC protocol enables simple and efficient organ clearing, rapid imaging by light-sheet microscopy and quantitative imaging analysis of multiple samples. The organ or body is cleared by immersion for 1-14 d, with the exact time required dependent on the sample type and the experimental purposes. A single imaging set can be completed in 30-60 min. Image processing and analysis can take <1 d, but it is dependent on the number of samples in the data set. The CUBIC clearing protocol can process multiple samples simultaneously. We previously used CUBIC to image whole-brain neural activities at single-cell resolution using Arc-dVenus transgenic (Tg) mice. CUBIC informatics calculated the Venus signal subtraction, comparing different brains at a whole-organ scale. These protocols provide a platform for organism-level systems biology by comprehensively detecting cells in a whole organ or body.

Clarifying Tissue Clearing

Biological specimens are intrinsically three dimensional; however, because of the obscuring effects of light scatter, imaging deep into a tissue volume is problematic. Although efforts to eliminate the scatter by "clearing" the tissue have been ongoing for over a century, there have been a large number of recent innovations. This Review introduces the physical basis for light scatter in tissue, describes the mechanisms underlying various clearing techniques, and discusses several of the major advances in light microscopy for imaging cleared tissue.

Single-cell phenotyping within transparent intact tissue through whole-body clearing

Understanding the structure-function relationships at cellular, circuit, and organ-wide scale requires 3D anatomical and phenotypical maps, currently unavailable for many organs across species. At the root of this knowledge gap is the absence of a method that enables whole-organ imaging. Herein, we present techniques for tissue clearing in which whole organs and bodies are rendered macromolecule-permeable and optically transparent, thereby exposing their cellular structure with intact connectivity. We describe PACT (passive clarity technique), a protocol for passive tissue clearing and immunostaining of intact organs; RIMS (refractive index matching solution), a mounting media for imaging thick tissue; and PARS (perfusion-assisted agent release in situ), a method for whole-body clearing and immunolabeling. We show that in rodents PACT, RIMS, and PARS are compatible with endogenous-fluorescence, immunohistochemistry, RNA single-molecule FISH, long-term storage, and microscopy with cellular and subcellular resolution. These methods are applicable for high-resolution, high-content mapping and phenotyping of normal and pathological elements within intact organs and bodies.

Scanning thin-sheet laser imaging microscopy elucidates details on mouse ear development

BACKGROUND

The mammalian inner ear is transformed from a flat placode into a three-dimensional (3D) structure with six sensory epithelia that allow for the perception of sound and both linear and angular acceleration. While hearing and balance problems are typically considered to be adult onset diseases, they may arise as a developmental perturbation to the developing ear. Future prevention of hearing or balance loss requires an understanding of how closely genetic mutations in model organisms reflect the human case, necessitating an objective multidimensional comparison of mouse ears with human ears that have comparable mutations in the same gene.

RESULTS

Here, we present improved 3D analyses of normal murine ears during embryonic development using optical sections obtained through Thin-Sheet Laser Imaging Microscopy. We chronicle the transformation of an undifferentiated otic vesicle between mouse embryonic day 11.5 to a fully differentiated inner ear at postnatal day 15.

CONCLUSIONS

Our analysis of ear development provides new insights into ear development, enables unique perspectives into the complex development of the ear, and allows for the first full quantification of volumetric and linear aspects of ear growth. Our data provide the framework for future analysis of mutant phenotypes that are currently under-appreciated using only two dimensional renderings.

Bone lengthening osteogenesis, a combination of intramembranous and endochondral ossification: an experimental study in sheep

We evaluated the morphological features of the newly formed tissue in an experimental model of tibial callotasis lengthening on 24 lambs, aged from 2 to 3 months at the time of operation. A unilateral external fixator prototype Monotube Triax^® (Stryker Howmedica Osteonics, New Jersey) was applied to the left tibia. A percutaneous osteotomy was performed in a minimally traumatic manner using a chisel. Lengthening was started 7 days after surgery and was continued to 30 mm. The 24 animals were randomly divided into three groups of 8 animals each: in Group 1, lengthening took place at a rate of 1 mm/day for 30 days; in Group 2, at a rate of 2 mm/day for 15 days; in Group 3, at a rate of 3 mm/day for 10 days. In each group, 4 animals were killed 2 weeks after end of lengthening, and the other 4 animals at 4 weeks after end of lengthening. To assess bony formation in the distraction area, radiographs were taken every 2 weeks from the day of surgery. To study the process of vascularization, we used Spalteholz’s technique. After killing, the tibia of each animal was harvested, and sections were stained with hematoxylin and eosin, Masson’s trichrome, and Safranin-O. Immunohistochemistry was performed, using specific antibodies to detect collagens I and II, S100 protein, and fibronectin. A combination of intramembranous and endochondral ossification occurred together at the site of distraction. Our study provides a detailed structural characterization of the newly formed tissue in an experimental model of tibial lengthening in sheep and may be useful for further investigations on callotasis.

Treatment of complex hand trauma using the distal ulnar and radial artery perforator-based flaps

The clinical value of distal ulnar or radial artery adipofascial perforator flaps is shown in a series of 30 patients with severe hand and wrist injuries and major soft tissue defects requiring coverage. There were 22 men and 8 women, aged 16-73 years. The defects were dorsal and/or palmar, with or without transpalmar or transcarpal amputation, or amputation of the thumb and/or the digits. Tendon injuries have been treated primarily or secondarily, or reconstructed using silicon rods. In all cases, after surgical debridement of the wound, reconstruction of the defect was done using distal ulnar (21 patients, in 3 patients primary reconstruction) and distal radial artery (11 patients; in 2 patients primary reconstruction and in 2 patients after necrosis of distal ulnar perforator flap) adipofascial perforator flaps. Minimum follow-up was 6 months. Two ulnar flap showed partial necrosis and were revised successfully by distal radial adipofascial perforator flaps. One radial and one ulnar flap showed 50% and 60% necrosis, respectively, and were revised by groin flaps. All donor sites healed uneventfully. Functional and cosmetic result was very good in 15 patients and good or satisfactory in the remaining. Range of motion of the wrist and hand joints was almost within normal limits (less than 25 degrees extension or flexion deficits). Distal ulnar and radial artery adipofascial perforator flaps for traumatic defects of the hand and wrist offer several advantages compared to other local flaps; they are easy to obtain and cover effectively both dorsal and palmar defects without significant functional deficits or donor site complications to the upper limb.

A review of vascular injection techniques for the study of perforator flaps

BACKGROUND

With a new era of flap surgery, additional anatomical information is required. The relatively recent interest in musculocutaneous perforator flaps has once again sparked interest in the vascular anatomy of surgical flaps. There are a variety of anatomical techniques available to define the vascular anatomy of tissues of interest. In this article, the authors review vascular injection techniques available and describe the technique currently used in their laboratory.

METHODS

A comprehensive review of vascular injection techniques is summarized. Barium sulfate and lead oxide in particular are reviewed in detail.

RESULTS

This article reviews the historical development of vascular injection techniques, outlines current investigative methods, and expands on a radiopaque lead oxide and gelatin injection method that provides high-quality angiograms.

CONCLUSIONS

The standard method for the study of perforator flap is the lead oxide-gelatin technique. However, other methods can provide complementary information on vascular anatomy.

The medial branch of the lateral branch of the posterior ramus of the spinal nerve

In the needle insertion of epidural anesthesia with the paramedian approach, the needle can pass through the longissimus muscle in the dorsum of the patients. When the needle touches a nerve in the muscles, the patients may experience pain in the back. Obviously, the needle should avoid the nerve tract. To provide better anesthetic service, analysis of the structure and where the concerned nerves lie in that region is inevitable.

MATERIAL AND METHOD

We studied five cadavers in this study. Two cadavers were fixed with Thiel's method. With these cadavers, we studied the nerve running of the posterior rami of the spinal nerve from the nerve root to the distal portion. Three of them were used for the study of transparent specimen, with which we studied the course and size of the nerve inside the longissimus muscle.

RESULTS

We observed there were three branches at the stem of the posterior rami of the spinal nerves between the body segment T3 and L5, i.e. medial branch, medial branch of the lateral branch and lateral branch of the lateral branch. The medial branch of the lateral branch supplied to the longissimus muscle. With the transparent specimen, we found that there were different nerve layouts between the upper thoracic, lower thoracic, upper lumbar, and lower lumbar segments in the medial branch of the lateral branch in the longissimus muscle. In the lower thoracic and upper lumbar segments, the medial branch of the lateral branch of the upper lumbar segments produced layers nerve network in the longissimus muscle. L1 and L2 nerves were large in size in the muscle.

CONCLUSION

In the upper lumbar segments the medial branch of the lateral branch of the posterior rami of the spinal nerve produced dense network in the longissimus muscle, where the epidural needle has high possibility to touch the nerve. Anesthetists have to consider the existence of the medial branch of the lateral branch of the posterior rami of the spinal nerve when they insert the needle in the paramedical approach to the spinal column.

The thoracodorsal artery perforator flap: anatomic basis and clinical application

Based on the dissection of 20 fresh cadavers, the authors have detailed further the vascular anatomy of the thoracodorsal artery and its cutaneous perforator vessels. The thoracodorsal artery showed a constant bifurcation into a horizontal branch and a lateral branch, located on the deep surface of the latissimus dorsi muscle 4 cm (range, 3-6 cm) distal to the inferior scapular border and 2.5 cm (range, 1-4 cm) medial to the lateral free margin of the muscle. In 20 specimens there was a total of 64 musculocutaneous perforators larger than 0.5 mm. Thirty-six perforators (56%) originated from the lateral branch and 28 perforators (44%) originated from the horizontal branch. All perforators originated within a distance of 8 cm from the neurovascular hilus and ran in proximity with the horizontal or lateral branches. In 11 dissections (55%) there was also a direct cutaneous branch originating from the extramuscular course of the thoracodorsal artery before the neurovascular hilus. This cutaneous branch did not pierce the latissimus muscle but rounded the lateral muscle edge and supplied the overlying subcutaneous tissue and skin. It is hoped that the constant anatomy will encourage surgeons in the future to use the thoracodorsal artery perforator flap more often.