The authors would like to acknowledge the following funding sources: NIH R01-AR063702, R21-AR064941, K99-AR067283, and T90-DE021989.

<ol>
	<li>Schofield, P. N., Vogel, P., Gkoutos, G. V., Sundberg, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploring+the+elephant:+histopathology+in+high-throughput+phenotyping+of+mutant+mice.">Exploring the elephant: histopathology in high-throughput phenotyping of mutant mice.</a> Dis Model Mech. 5 (1), 19-25 (2012).</li><li>Adissu, H. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histopathology+reveals+correlative+and+unique+phenotypes+in+a+high-throughput+mouse+phenotyping+screen.">Histopathology reveals correlative and unique phenotypes in a high-throughput mouse phenotyping screen.</a> Disease Models and Mechanisms. 7 (5), 515-524 (2014).</li><li>Johnson, J. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Virtual+histology+of+transgenic+mouse+embryos+for+high-throughput+phenotyping.">Virtual histology of transgenic mouse embryos for high-throughput phenotyping.</a> PLoS Genet. 2 (4), e61 (2006).</li><li>Ayadi, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+large-scale+phenotyping+initiatives:+overview+of+the+European+Mouse+Disease+Clinic+(EUMODIC)+and+of+the+Wellcome+Trust+Sanger+Institute+Mouse+Genetics+Project.">Mouse large-scale phenotyping initiatives: overview of the European Mouse Disease Clinic (EUMODIC) and of the Wellcome Trust Sanger Institute Mouse Genetics Project.</a> Mamm.Genome. 23 (9-10), 600-610 (2012).</li><li>Utreja, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+and+matrix+response+of+temporomandibular+cartilage+to+mechanical+loading.">Cell and matrix response of temporomandibular cartilage to mechanical loading.</a> Osteoarthr Cartil. 24 (2), 335-344 (2016).</li><li>Dyment, N. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gdf5+progenitors+give+rise+to+fibrocartilage+cells+that+mineralize+via+hedgehog+signaling+to+form+the+zonal+enthesis.">Gdf5 progenitors give rise to fibrocartilage cells that mineralize via hedgehog signaling to form the zonal enthesis.</a> Dev.Biol. 405 (1), 96-107 (2015).</li><li>Lalley, A. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+biomechanical+and+biological+outcomes+in+the+MRL/MpJ+murine+strain+following+a+full-length+patellar+tendon+injury.">Improved biomechanical and biological outcomes in the MRL/MpJ murine strain following a full-length patellar tendon injury.</a> J.Orthop.Res. 33 (11), 1693-1703 (2015).</li><li>Breidenbach, A. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ablating+hedgehog+signaling+in+tenocytes+during+development+impairs+biomechanics+and+matrix+organization+of+the+adult+murine+patellar+tendon+enthesis.">Ablating hedgehog signaling in tenocytes during development impairs biomechanics and matrix organization of the adult murine patellar tendon enthesis.</a> J.Orthop.Res. 33 (8), 1142-1151 (2015).</li><li>Ushiku, C., Adams, D., Jiang, X., Wang, L., Rowe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long+Bone+Fracture+Repair+in+Mice+Harboring+GFP+Reporters+for+Cells+within+the+Osteoblastic+Lineage.">Long Bone Fracture Repair in Mice Harboring GFP Reporters for Cells within the Osteoblastic Lineage.</a> J.Orthop.Res. 28 (10), 1338-1347 (2010).</li><li>Matthews, B. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+asMA-labeled+progenitor+cell+commitment+identifies+notch+signaling+as+an+important+pathway+in+fracture+healing.">Analysis of asMA-labeled progenitor cell commitment identifies notch signaling as an important pathway in fracture healing.</a> J.Bone Miner.Res. 29 (5), 1283-1294 (2014).</li><li>Dyment, N. A., Hagiwara, Y., Jiang, X., Huang, J., Adams, D. J., Rowe, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Response+of+knee+fibrocartilage+to+joint+destabilization.">Response of knee fibrocartilage to joint destabilization.</a> Osteoarthritis Cartilage. 23 (6), 996-1006 (2015).</li><li>Grcevic, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+fate+mapping+identifies+mesenchymal+progenitor+cells.">In vivo fate mapping identifies mesenchymal progenitor cells.</a> Stem Cells. 30 (2), 187-196 (2012).</li><li>Hong, S. H., Jiang, X., Chen, L., Josh, P., Shin, D. G., Rowe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computer-Automated+Static,+Dynamic+and+Cellular+Bone+Histomorphometry.">Computer-Automated Static, Dynamic and Cellular Bone Histomorphometry.</a> J Tissue Sci Eng. Suppl 1, 004 (2012).</li><li>Matthews, B. G., Torreggiani, E., Roeder, E., Matic, I., Grcevic, D., Kalajzic, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteogenic+potential+of+alpha+smooth+muscle+actin+expressing+muscle+resident+progenitor+cells.">Osteogenic potential of alpha smooth muscle actin expressing muscle resident progenitor cells.</a> Bone. 84, 69-77 (2016).</li><li>Hagiwara, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fixation+stability+dictates+the+differentiation+pathway+of+periosteal+progenitor+cells+in+fracture+repair.">Fixation stability dictates the differentiation pathway of periosteal progenitor cells in fracture repair.</a> J.Orthop.Res. 33 (7), 948-956 (2015).</li><li>Jiang, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histological+analysis+of+GFP+expression+in+murine+bone.">Histological analysis of GFP expression in murine bone.</a> J.Histochem.Cytochem. 53 (5), 593-602 (2005).</li><li>Nissanov, J., Bertrand, L., Tretiak, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryosectioning+distortion+reduction+using+tape+support.">Cryosectioning distortion reduction using tape support.</a> Microsc.Res.Tech. 53 (3), 239-240 (2001).</li><li>Kawamoto, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+a+new+adhesive+film+for+the+preparation+of+multi-purpose+fresh-frozen+sections+from+hard+tissues,+whole-animals,+insects+and+plants.">Use of a new adhesive film for the preparation of multi-purpose fresh-frozen sections from hard tissues, whole-animals, insects and plants.</a> Arch.Histol.Cytol. 66 (2), 123-143 (2003).</li></ol>

The authors declare that they have no competing financial interests.

Here we have presented a detailed cryohistology protocol to co-localize and quantify several biological measures by aligning images from multiple rounds of staining/imaging on a single section. The method outlined using the cryotape is especially useful as it maintains the morphology of difficult to section tissue (e.g., mineralized bone and cartilage). In addition, the sectioned tissue is adhered firmly to the glass slide, allowing for multiple rounds of staining/imaging of the same section; unlike traditional ...

Biological research often requires efficient phenotyping, which is frequently associated with some sort of histological analysis1-3. This need is even more evident with the ambitious projects to disrupt each gene in the mouse genome4. These histological analyses can range from assessing cell morphology and/or anatomical features to mapping expression of specific genes or proteins to individual cells. In fact, one of the fundamental contributions of histology to the field of genomics is the ability to associate a specific molecular signal to a specific region or cell type.
Traditional methods of histology, especially for musculoskeletal tissues, are often time consuming and laborious, requiring sometimes weeks to fix, decalcify, section, stain, and image the specimen then analyze the images via human interpretation. Analyzing multiple molecular signals, whether via immunohistochemistry, in situ hybridization, or special stains, requires multiple sections and even multiple specimens to perform appropriately. In addition, these multiple responses cannot be co-localized to the same cell and sometimes cannot be co-localized to a specific region within a given specimen. As the genomics and epigenomics field moves into the digital age, the histological field must also follow suit to provide efficient, high-throughput, and automated analysis of a variety of molecular signals within a single histological section.
Indeed, there is a demand for improved histological techniques that can associate multiple molecular signals to specific cells within a given specimen. Recently, we have published a new high-throughput cryohistological method for assessing several response measures within a given section from mineralized tissue5-14. The process involves stabilizing the cryosection with frozen cryotape, adhering the taped section rigidly to a microscope slide, and conducting several rounds of staining and imaging on each section. These rounds of images are then aligned manually or via computer automation prior to image analysis (Figure 1). Here, we present detailed protocols of this process and provide examples where these techniques have improved our understanding of different biological processes.

<table><tbody><tr><td>10% neutral buffered formalin</td><td>Sigma Aldrich</td><td>HT501128-4L</td><td>Multiple suppliers available. Toxic. Can be substituted with 4% paraformaldehyde.</td></tr><tr><td>Sucrose</td><td>Sigma Aldrich</td><td>S9378</td><td>Multiple suppliers available.</td></tr><tr><td>PBS</td><td>Sigma Aldrich</td><td>P5368</td><td>Multiple suppliers available.</td></tr><tr><td>Cryomolds</td><td>Fisher Scientific</td><td>Fisherbrand #22-363-554</td><td>Different sizes can be used depending on tissue</td></tr><tr><td>Cryomatrix</td><td>Thermo Scientific</td><td>6769006</td><td>Can be substitituted with other cryomatrices. However, PVA/PEG-based resins have worked best in our hands.</td></tr><tr><td>2-methyl-butane</td><td>Sigma Aldrich</td><td>M32631</td><td>Multiple suppliers available.</td></tr><tr><td>Cryostat</td><td>Leica Biosystems</td><td>3050s</td><td>Can be substituted with other brands/models.</td></tr><tr><td>Specimen disc</td><td>Leica Biosystems</td><td>14037008587</td><td>Can be substituted with other brands/models.</td></tr><tr><td>Cryostat blades</td><td>Thermo Scientific</td><td>3051835</td><td>Can be substituted with other brands/models.</td></tr><tr><td>Cryotape</td><td>Section Lab</td><td>Cryofilm 2C</td><td></td></tr><tr><td>Roller</td><td>Electron Microscopy Sciences</td><td>62800-46</td><td>Can be substituted with other brands/models.</td></tr><tr><td>Plastic microscope slides</td><td>Electron Microscopy Sciences</td><td>71890-01</td><td>Can be substituted with other brands/models.</td></tr><tr><td>Glass microscope slides</td><td>Thermo Scientific</td><td>3051</td><td>Can be substituted with other brands/models.</td></tr><tr><td>Norland Optical Adhesive, 61</td><td>Norland Optical</td><td>Norland Optical Adhesive, 61</td><td></td></tr><tr><td>UV Black Light</td><td>General Electric</td><td>F15T8-BLB</td><td></td></tr><tr><td>Glacial acetic acid</td><td>Sigma Aldrich</td><td>ARK2183</td><td>Multiple suppliers available.</td></tr><tr><td>Chitosan</td><td>Sigma Aldrich</td><td>C3646</td><td>Multiple suppliers available.</td></tr><tr><td>InSpeck red microscopheres</td><td>ThermoFisher Scientific</td><td>I-14787</td><td></td></tr><tr><td>InSpeck green microspheres</td><td>ThermoFisher Scientific</td><td>I-14785</td><td></td></tr><tr><td>Calcein Blue</td><td>Sigma Aldrich</td><td>M1255</td><td>Multiple suppliers available.</td></tr><tr><td>Calcein</td><td>Sigma Aldrich</td><td>C0875&amp;nbsp;</td><td>Multiple suppliers available.</td></tr><tr><td>Alizarin complexone</td><td>Sigma Aldrich</td><td>A3882&amp;nbsp;</td><td>Multiple suppliers available.</td></tr><tr><td>Demeclocycline</td><td>Sigma Aldrich</td><td>D6140&amp;nbsp;</td><td>Multiple suppliers available.</td></tr><tr><td>NaHCO&lt;sub&gt;3&lt;/sub&gt;</td><td>Sigma Aldrich</td><td>S5761</td><td>Multiple suppliers available.</td></tr><tr><td>Glycerol</td><td>Sigma Aldrich</td><td>G5516</td><td>Multiple suppliers available.</td></tr><tr><td>ELF 97 yellow fluorescent acid phosphatase substrate</td><td>ThermoFisher Scientific</td><td>E-6588</td><td></td></tr><tr><td>DAPI</td><td>ThermoFisher Scientific</td><td>62247</td><td>Multiple suppliers available. Can be substituted with Hoechst 33342 or other nuclear dyes.</td></tr><tr><td>TO-PRO-3 (Cy5 nuclear counterstain)</td><td>ThermoFisher Scientific</td><td>T3605</td><td></td></tr><tr><td>Propidium Iodide</td><td>ThermoFisher Scientific</td><td>R37108</td><td>Multiple suppliers available.</td></tr><tr><td>Sodium acetate anhydrous</td><td>Sigma Aldrich</td><td>S2889</td><td>Multiple suppliers available.</td></tr><tr><td>sodium tartrate dibasic dihydrate&amp;nbsp;</td><td>Sigma Aldrich</td><td>T6521</td><td>Multiple suppliers available.</td></tr><tr><td>Sodium nitrite</td><td>Sigma Aldrich</td><td>S2252</td><td>Multiple suppliers available.</td></tr><tr><td>Tris</td><td>Sigma Aldrich</td><td>15504</td><td>Multiple suppliers available.</td></tr><tr><td>MgCl&lt;sub&gt;2&lt;/sub&gt; hexahydrate</td><td>Sigma Aldrich</td><td>M9272</td><td>Multiple suppliers available.</td></tr><tr><td>NaCl</td><td>Sigma Aldrich</td><td>S7653</td><td>Multiple suppliers available.</td></tr><tr><td>Fast Red TR Salt</td><td>Sigma Aldrich</td><td>F8764</td><td>Multiple suppliers available. Can also be substituted with other substrate kits such as Vector Blue (Vector Laboratories, Cat# SK-5300)</td></tr><tr><td>Naphthol AS-MX&amp;nbsp;</td><td>Sigma Aldrich</td><td>N4875</td><td>Multiple suppliers available.</td></tr><tr><td>N,N dimethylformamide</td><td>Sigma Aldrich</td><td>D158550</td><td>Multiple suppliers available.</td></tr><tr><td>Toluidine blue O</td><td>Sigma Aldrich</td><td>T3260</td><td>Multiple suppliers available.</td></tr><tr><td>Axio Scan.Z1</td><td>Carl Zeiss AG</td><td>Axio Scan.Z1</td><td>Other linear or tiled scanners may also be used.</td></tr><tr><td>DAPI Filter Set</td><td>Chroma Technology Corp.</td><td>49000</td><td></td></tr><tr><td>CFP Filter Set</td><td>Chroma Technology Corp.</td><td>49001</td><td></td></tr><tr><td>GFP Filter Set</td><td>Chroma Technology Corp.</td><td>49020</td><td></td></tr><tr><td>YFP Filter Set</td><td>Chroma Technology Corp.</td><td>49003</td><td></td></tr><tr><td>Custom yellow (ELF 97) Filter Set</td><td>Chroma Technology Corp.</td><td>custom; HQ409sp, HQ555/30m, 425dxcr</td><td></td></tr><tr><td>TRITC Filter Set</td><td>Chroma Technology Corp.</td><td>49004</td><td></td></tr><tr><td>Cy5 Filter Set</td><td>Chroma Technology Corp.</td><td>49009</td><td></td></tr><tr><td>CryoJane Tape Transfer System</td><td>Electron Microscopy Sciences</td><td>62800-10</td><td>Multiple suppliers available.</td></tr><tr><td>CryoJane Tape Windows</td><td>Electron Microscopy Sciences</td><td>62800-72</td><td>Multiple suppliers available.</td></tr><tr><td>CryoJane Adhesive Slides</td><td>Electron Microscopy Sciences</td><td>62800-4X</td><td>Multiple suppliers available.</td></tr></tbody></table>

high-throughput, multi-image cryohistology of mineralized tissues

There is an increasing need for efficient phenotyping and histopathology of a variety of tissues. This phenotyping need is evident with the ambitious projects to disrupt every gene in the mouse genome. The research community needs rapid and inexpensive means to phenotype tissues via histology. Histological analyses of skeletal tissues are often time consuming and semi-quantitative at best, regularly requiring subjective interpretation of slides from trained individuals. Here, we present a cryohistological paradigm for efficient and inexpensive phenotyping of mineralized tissues. First, we present a novel method of tape-stabilized cryosectioning that preserves the morphology of mineralized tissues. These sections are then adhered rigidly to glass slides and imaged repeatedly over several rounds of staining. The resultant images are then aligned either manually or via computer software to yield composite stacks of several layered images. The protocol allows for co-localization of numerous molecular signals to specific cells within a given section. In addition, these fluorescent signals can be quantified objectively via computer software. This protocol overcomes many of the shortcomings associated with histology of mineralized tissues and can serve as a platform for high-throughput, high-content phenotyping of musculoskeletal tissues moving forward.

A General Workflow for the High-Throughput, Multi-Image Cryohistology
Figure 1 represents the general workflow used for this technique. It includes several steps from fixation through several rounds of imaging and finally image alignment/analysis. The process can take as little as a week to go from sample fixation through 4 rounds of imaging, which is less time than it takes to decalcify these t...

Watch this Scientific Journal Video about High-Throughput, Multi-Image Cryohistology of Mineralized Tissues at JoVE.com

High-Throughput, Multi-Image Cryohistology of Mineralized Tissues

In this manuscript, we present a high-throughput, semi-automated cryohistology platform to produce aligned composite images of multiple response measures from several rounds of fluorescent imaging on frozen sections of mineralized tissues.

There is an increasing need for efficient phenotyping and histopathology of a variety of tissues. This phenotyping need is evident with the ambitious ...

high-throughput-multi-image-cryohistology-of-mineralized-tissues

Research

JoVE Journal

Biology

15.9K Views.  University of Connecticut Health Center. In this manuscript, we present a high-throughput, semi-automated cryohistology platform to produce aligned composite images of multiple response measures from several rounds of fluorescent imaging on frozen sections of mineralized tissues. 

Video: High-Throughput, Multi-Image Cryohistology of Mineralized Tissues

High Resolution 3D Imaging of Ex-Vivo Biological Samples by Micro CT

Non-destructive volume visualization can be achieved only by tomographic techniques, of which the most efficient is the x-ray micro computerized tomography (&mu;CT).
High resolution &mu;CT is a very versatile yet accurate (1-2 microns of resolution) technique for 3D examination of ex-vivo biological samples1, 2. As opposed to electron tomography, the &mu;CT allows the examination of up to 4 cm thick samples. This technique requires only few hours of measurement as compared to weeks in histology. In addition, &mu;CT does not rely on 2D stereologic models, thus it may complement and in some cases can even replace histological methods3, 4, which are both time consuming and destructive. Sample conditioning and positioning in &mu;CT is straightforward and does not require high vacuum or low temperatures, which may adversely affect the structure. The sample is positioned and rotated 180&deg; or 360&deg;between a microfocused x-ray source and a detector, which includes a scintillator and an accurate CCD camera, For each angle a 2D image is taken, and then the entire volume is reconstructed using one of the different available algorithms5-7. The 3D resolution increases with the decrease of the rotation step. The present video protocol shows the main steps in preparation, immobilization and positioning of the sample followed by imaging at high resolution.

High Resolution 3D Imaging of Ex-Vivo Biological Samples by Micro CT

Non-destructive volume visualization can be achieved only by tomographic techniques, of which the most efficient is the x-ray micro computerized tomography ( CT).

Non-destructive volume visualization can be achieved only by tomographic techniques, of which the most efficient is the x-ray micro computerized ...

Bioengineering

Horizontal Whole Mount: A Novel Processing and Imaging Protocol for Thick, Three-dimensional Tissue Cross-sections of Skin

Processing a tissue of interest to generate a microscopic image that supports a scientific argument can be challenging. The acquisition of high-quality microscopic images is not entirely dependent upon the quality of the microscope, but also upon the methods of tissue processing, which often involve multiple critical actions or steps. Furthermore, mesenchymal cell types in the skin and other tissues represent a new challenge for tissue preparation and imaging. Here, we present a complete process, from tissue harvest to microscopy. Our technique, called &#34;horizontal whole mount,&#34; is one that novices can quickly become proficient in and that allows for antigen preservation and detection in 60-300 &#181;m-thick sections cut with a cryostat. Sections of this thickness provide enhanced visualization of tissue microarchitecture in a three-dimensional environment. In addition, the protocol preserves mesenchymal cells in a manner that enhances image quality when compared to standard cryostat or paraffin sections, thereby increasing the efficacy and reliability of immunostaining. We believe that this protocol will benefit all laboratories that visualize skin, and possibly other tissues and organs.

This work presents a novel processing and imaging protocol for thick, three-dimensional tissue cross-section analysis that enables the full exploitation of confocal imaging modalities. This protocol preserves antigenicity and represents a robust system to analyze skin histology and potentially other tissue types.

Processing a tissue of interest to generate a microscopic image that supports a scientific argument can be challenging. The acquisition of high-quality ...

Developmental Biology

Multimodal Hierarchical Imaging of Serial Sections for Finding Specific Cellular Targets within Large Volumes

Targeting specific cells at ultrastructural resolution within a mixed cell population or a tissue can be achieved by hierarchical imaging using a combination of light and electron microscopy. Samples embedded in resin are sectioned into arrays consisting of ribbons of hundreds of ultrathin sections and deposited on pieces of silicon wafer or conductively coated coverslips. Arrays are imaged at low resolution using a digital consumer like smartphone camera or light microscope (LM) for a rapid large area overview, or a wide field fluorescence microscope (fluorescence light microscopy (FLM)) after labeling with fluorophores. After post-staining with heavy metals, arrays are imaged in a scanning electron microscope (SEM). Selection of targets is possible from 3D reconstructions generated by FLM or from 3D reconstructions made from the SEM image stacks at intermediate resolution if no fluorescent markers are available. For ultrastructural analysis, selected targets are finally recorded in the SEM at high-resolution (a few nanometer image pixels). A ribbon-handling tool that can be retrofitted to any ultramicrotome is demonstrated. It helps with array production and substrate removal from the sectioning knife boat. A software platform that allows automated imaging of arrays in the SEM is discussed. Compared to other methods generating large volume EM data, such as serial block-face SEM (SBF-SEM) or focused ion beam SEM (FIB-SEM), this approach has two major advantages: (1) The resin-embedded sample is conserved, albeit in a sliced-up version. It can be stained in different ways and imaged with different resolutions. (2) As the sections can be post-stained, it is not necessary to use samples strongly block-stained with heavy metals to introduce contrast for SEM imaging or render the tissue blocks conductive. This makes the method applicable to a wide variety of materials and biological questions. Particularly prefixed materials e.g., from biopsy banks and pathology labs, can directly be embedded and reconstructed in 3D.

This protocol targets specific cells in tissue for imaging at nanoscale resolution using a scanning electron microscope (SEM). Large numbers of serial sections from resin-embedded biological material are first imaged in a light microscope to identify the target and then in a hierarchical manner in the SEM.

Targeting specific cells at ultrastructural resolution within a mixed cell population or a tissue can be achieved by hierarchical imaging using a ...

Clonal Genetic Tracing using the Confetti Mouse to Study Mineralized Tissues

Labeling an individual cell in the body to monitor which cell types it can give rise to and track its migration through the organism or determine its longevity can be a powerful way to reveal mechanisms of tissue development and maintenance. One of the most important tools currently available to monitor cells in vivo is the Confetti mouse model. The Confetti model can be used to genetically label individual cells in living mice with various fluorescent proteins in a cell type-specific manner and monitor their fate, as well as the fate of their progeny over time, in a process called clonal genetic tracing or clonal lineage tracing. This model was generated almost a decade ago and has contributed to an improved understanding of many biological processes, particularly related to stem cell biology, development, and renewal of adult tissues. However, preserving the fluorescent signal until image collection and simultaneous capturing of various fluorescent signals is technically challenging, particularly for mineralized tissue. This publication describes a step-by-step protocol for using the Confetti model to analyze growth plate cartilage that can be applied to any mineralized or nonmineralized tissue.

This method describes the use of the R26R-Confetti (Confetti) mouse model to study mineralized tissues, covering all steps from the breeding strategy to the image acquirements. Included is a general protocol that can be applied to all soft tissues and a modified protocol that can be applied to mineralized tissues.

Labeling an individual cell in the body to monitor which cell types it can give rise to and track its migration through the organism or determine its ...

A Rapid Method for Multispectral Fluorescence Imaging of Frozen Tissue Sections

Multispectral fluorescence imaging on formalin-fixed paraffin-embedded (FFPE) tissues enables the detection of multiple markers in a single tissue sample that can provide information about antigen coexpression and spatial distribution of the markers. However, a lack of suitable antibodies for formalin-fixed tissues may restrict the nature of markers that can be detected. In addition, the staining method is time-consuming. Here we describe a rapid method to perform multispectral fluorescence imaging on frozen tissues. The method includes the fluorophore combinations used, detailed steps for the staining of mouse and human frozen tissues, and the scanning, acquisition, and analysis procedures. For staining analysis, a commercially available semiautomated multispectral fluorescence imaging system is used. Through this method, up to six different markers were stained and detected in a single frozen tissue section. The machine learning analysis software can phenotype cells that can be used for quantitative analysis. The method described here for frozen tissues is useful for the detection of markers that cannot be detected in FFPE tissues or for which antibodies are not available for FFPE tissues.

We describe a rapid staining method to perform multispectral imaging on frozen tissues.

Multispectral fluorescence imaging on formalin-fixed paraffin-embedded (FFPE) tissues enables the detection of multiple markers in a single tissue sample ...

Immunology and Infection

Cryosectioning of Contiguous Regions of a Single Mouse Skeletal Muscle for Gene Expression and Histological Analyses

With this method, consecutive cryosections are collected to enable both microscopy applications for tissue histology and enrichment of RNA for gene expression using adjacent regions from a single mouse skeletal muscle. Typically, it is challenging to achieve adequate homogenization of small skeletal muscle samples because buffer volumes may be too low for efficient grinding applications, yet without sufficient mechanical disruption, the dense tissue architecture of muscle limits penetration of buffer reagents, ultimately causing low RNA yield. By following the protocol reported here, 30 &#956;m sections are collected and pooled allowing cryosectioning and subsequent needle homogenization to mechanically disrupt the muscle, increasing the surface area exposed for buffer penetration. The primary limitations of the technique are that it requires a cryostat, and it is relatively low throughput. However, high-quality RNA can be obtained from small samples of pooled muscle cryosections, making this method accessible for many different skeletal muscles and other tissues. Furthermore, this technique enables matched analyses (e.g., tissue histopathology and gene expression) from adjacent regions of a single skeletal muscle so that measurements can be directly compared across applications to reduce experimental uncertainty and to reduce replicative animal experiments necessary to source a small tissue for multiple applications.

Consecutive cryo-sections are collected to enable histological applications and enrichment of RNA for gene expression measurements using adjacent regions from a single mouse skeletal muscle. High-quality RNA is obtained from 20 - 30 mg of pooled cryosections and measurements are directly compared across applications.

With this method, consecutive cryosections are collected to enable both microscopy applications for tissue histology and enrichment of RNA for gene ...

Biological Sample Preparation by High-pressure Freezing, Microwave-assisted Contrast Enhancement, and Minimal Resin Embedding for Volume Imaging

The described sample preparation technique is designed to combine the best quality of ultrastructural preservation with the most suitable contrast for the imaging modality in a focused ion beam scanning electron microscope (FIB-SEM), which is used to obtain stacks of sequential images for 3D reconstruction and modelling. High-pressure freezing (HPF) allows close to native structural preservation, but the subsequent freeze substitution often does not provide sufficient contrast, especially for a bigger specimen, which is needed for high-quality imaging in the SEM required for 3D reconstruction. Therefore, in this protocol, after the freeze substitution, additional contrasting steps are carried out at room temperature. Although these steps are performed in a microwave, it is also possible to follow traditional bench processing, which requires longer incubation times.The subsequent embedding in minimal amounts of resin allows for faster and more precise targeting and preparation inside the FIB-SEM. This protocol is especially useful for samples that require preparation by high-pressure freezing for a reliable ultrastructural preservation but do not gain enough contrast during the freeze substitution for volume imaging using FIB-SEM. In combination with the minimal resin embedding, this protocol provides an efficient workflow for the acquisition of high-quality volume data.

Here we present a protocol for combining two sample processing techniques, high-pressure freezing and microwave-assisted sample processing, followed by minimal resin embedding for acquiring data with a focused ion beam scanning electron microscope (FIB-SEM). This is demonstrated using a mouse tibial nerve sample and Caenorhabditis elegans.

The described sample preparation technique is designed to combine the best quality of ultrastructural preservation with the most suitable contrast for the ...

A Sectioning, Coring, and Image Processing Guide for High-Throughput Cortical Bone Sample Procurement and Analysis for Synchrotron Micro-CT

Bone is a dynamic and mechanically active tissue that changes in structure over the human lifespan. The products of the bone remodeling process have been studied substantially using traditional two-dimensional techniques. Recent advancements in X-ray imaging technology via desktop micro-computed tomography (&#181;CT) and synchrotron radiation micro-computed tomography (SR&#181;CT) have allowed for the acquisition of high-resolution three-dimensional (3D) scans of a larger field of view (FOV) than other 3D imaging techniques (e.g., SEM) providing a more complete picture of microscopic structures within human cortical bone. The specimen should be accurately centered within the FOV, however, to limit the appearance of streak artifacts known to impact data analysis. Previous studies have reported procurement of irregularly shaped rectilinear bone blocks that result in imaging artifacts due to uneven edges or image truncation. We have applied a geological sampling protocol (coring) to procure consistently sized cortical bone core specimens for SR&#181;CT experiments from the anterior aspect of human femora. This coring method is efficient and minimally destructive to tissue. It creates uniform cylindrical samples that decrease imaging artifacts by nature of being isometric during rotation and providing a uniform path length for X-ray beams throughout scanning. Image processing of X-ray tomographic data of cored and irregularly shaped samples confirms the potential of the technique to improve visualization and analysis of cortical bone microarchitecture. A goal of this protocol is to deliver a reliable and repeatable method for the extraction of cortical bone cores that is adaptable for various types of high-resolution bone imaging experiments. An overarching goal of the work is to create a standardized cortical bone procurement for SR&#181;CT that is affordable, consistent, and straightforward. This procedure may further be adapted by researchers in related fields who commonly evaluate hard composite materials such as in biological anthropology, geosciences, or material sciences.

We employed a geological (coring) sampling protocol to procure cortical bone specimens of uniform size for SR&#181;CT experiments from the anterior aspect of human femora. This method is minimally destructive, efficient, results in cylindrical specimens that minimize imaging artifacts from irregular sample shapes and improves microarchitectural visualization and analysis.

Bone is a dynamic and mechanically active tissue that changes in structure over the human lifespan. The products of the bone remodeling process have been ...

A 3D Cartographic Description of the Cell by Cryo Soft X-ray Tomography

Imaging techniques are fundamental in order to understand cell organization and machinery in biological research and the related fields. Among these techniques, cryo soft X-ray tomography (SXT) allows imaging whole cryo-preserved cells in the water window X-ray energy range (284-543 eV), in which carbon structures have intrinsically higher absorption than water, allowing the 3D reconstruction of the linear absorption coefficient of the material contained in each voxel. Quantitative structural information at the level of whole cells up to 10 &#181;m thick is then achievable this way, with high throughput and spatial resolution down to 25-30 nm half-pitch. Cryo-SXT has proven itself relevant to current biomedical research, providing 3D information on cellular infection processes (virus, bacteria, or parasites), morphological changes due to diseases (such as recessive genetic diseases) and helping us understand drug action at the cellular level, or locating specific structures in the 3D cellular environment. In addition, by taking advantage of the tunable wavelength at synchrotron facilities, spectro-microscopy or its 3D counterpart, spectro-tomography, can also be used to image and quantify specific elements in the cell, such as calcium in biomineralization processes. Cryo-SXT provides complementary information to other biological imaging techniques such as electron microscopy, X-ray fluorescence or visible light fluorescence, and is generally used as a partner method for 2D or 3D correlative imaging at cryogenic conditions in order to link function, location, and morphology.

Here, a protocol describing the sample preparation and data collection steps required in cryo soft X-ray tomography (SXT) to image the ultrastructure of whole cryo-preserved cells at a resolution of 25 nm half pitch, is presented.

Imaging techniques are fundamental in order to understand cell organization and machinery in biological research and the related fields. Among these ...

Cryo-Structured Illumination Microscopic Data Collection from Cryogenically Preserved Cells

Three-dimensional (3D) structured illumination microscopy (SIM) allows imaging of fluorescently labelled cellular structures at higher resolution than conventional fluorescence microscopy. This super-resolution (SR) technique enables visualization of molecular processes in whole cells and has the potential to be used in conjunction with electron microscopy and X-ray tomography to correlate structural and functional information. A SIM microscope for cryogenically preserved samples (cryoSIM) has recently been commissioned at the correlative cryo-imaging beamline B24 at the UK synchrotron. 
It was designed specifically for 3D imaging of biological samples at cryogenic temperatures in a manner compatible with subsequent imaging of the same samples by X-ray microscopy methods such as cryo-soft X-ray tomography. This video article provides detailed methods and protocols for successful imaging using the cryoSIM. In addition to instructions on the operation of the cryoSIM microscope, recommendations have been included regarding the choice of samples, fluorophores, and parameter settings. The protocol is demonstrated in U2OS cell samples whose mitochondria and tubulin have been fluorescently labelled.

This protocol demonstrates how to image biological cryo-preserved samples using cryo-structured illumination microscopy. We demonstrate the methodology by imaging the cytoskeleton of U2OS cells.

Three-dimensional (3D) structured illumination microscopy (SIM) allows imaging of fluorescently labelled cellular structures at higher resolution than ...

High-Throughput, Multi-Image Cryohistology of Mineralized Tissues

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