Name: undecalcified bone preparation for histology, histomorphometry and fluorochrome analysis
Uploaded: 2010-01-08T17:00:00
Description: Watch this Scientific Journal Video about Undecalcified Bone Preparation for Histology, Histomorphometry and Fluorochrome Analysis at JoVE.com

The authors would like to acknowledge the assistance of Ms Sue Connell for her expertise in resin embedding and Ms Stephania Tombs for her laboratory expertise. The authors would like to thank Professor Frank Kandziora and Dr Marie-Anne Polboth for their advice.

<ol>
 <li>The tissue is placed in a sealed container containing 10% phosphate buffered formalin solution3. Ensure minimal exposure to light, if fluorochrome analysis is to be performed, as the fluorochromes are light sensitive. </li>
 <li>Establish which orientation of the tissue will be required. </li>
 <li>Trim the specimen to size, in the correct orientation, using a band saw. Ensure safety measures are adhered to. The specimen is then placed into an opaque container, the volume of which should be approximately ten times t...

<ol>
	<li>Kerr, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Atlas of Functional Histology. , 164-168 (2000).</li><li>Parfitt, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+histomorphometry:+standardization+of+nomenclature,+symbols,+and+units.+Report+of+the+ASBMR+Histomorphometry+Nomenclature+Committee.">Bone histomorphometry: standardization of nomenclature, symbols, and units. Report of the ASBMR Histomorphometry Nomenclature Committee.</a> J Bone Miner Res. 2, 595-610 (1987).</li><li>An, Y. H., Martin, K. l. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Handbook of histology methods for bone and cartilage. , (2003).</li><li>Bancroft, J. D., Gamble, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Theory and Practice of Histological Techniques. , 352-360 (2008).</li></ol>

Solvents:
 <ul>
 <li>10% Normal Buffered Formalin, Ethanol, Xylene and Butanol acid 
 All histology grade, sulfur free. Grale Scientific Pty Ltd. http://www.grale.com.au</li>
</ul>
Moulds:
 <ul>
 <li>Peel away, plastic moulds Grale Scientific</li>
</ul>
Slides:
 <ul>
 <li>SUPERFROST PLUS Microscope slides Lomb Scientific Pty Ltd. 
 <a href="http://www.lomb.com.au/">http://www.lomb.com.au</a></li>
 </ul>
Resin:
 <ul>
 <li>GlycolMethacrylate Technovit 7100 Heraeus Kulzer 
 <a href="http://www.kulzer-technik.de/168/Products/Histology/Technovit_7100.htm">http://www.kulzer-technik.de/168/Products/Histology/Technovit_7100.htm</a></li>
 <li>Backing Block Resin- Technovit 3040 Histo block Heraeus Kulzer</li>
 </ul>
Stains 
(Reagents from Grale Scientific)
Goldner's Trichrome stain</li>
1. Weigert's iron hemotoxylin (DeGroat)
<table style="margin-left:40px;" border="0">
<tr><td colspan="2" style="font-weight:bold;">a) Hemotoxylin solution</td></tr>
<tr><td>Hemotoxylin</td><td>1g</td></tr>
<tr><td>Absolute Alcohol</td><td>100mL</td></tr>
<tr><td colspan="2" style="font-weight:bold;">b) Iron Solution</td></tr>
<tr><td>30% aqueous ferric chloride</td><td>4mL</td></tr>
<tr><td>Hydrochloric acid (concentrated)</td><td>1mL</td></tr>
<tr><td>distilled Water</td><td>95mL</td></tr>
</table>
Filtered and added to equal volume of hemotoxylin immediately before stain used.
2. Ponceau-fuchsin-azophloxin stock solutions
<table style="margin-left:40px;" border="0">
<tr><td colspan="2" style="font-weight:bold;">a) Ponceau de xylidine solution</td></tr>
<tr><td>Ponceau de xylidine</td><td>0.75g</td></tr>
<tr><td>acid fuchsion</td><td>0.25g</td></tr>
<tr><td>Acetic Acid</td><td>1mL</td></tr>
<tr><td colspan="2">mix, and add distilled water (100mL)</td></tr>
<tr><td colspan="2" style="font-weight:bold;">b) azophloxin solution</td></tr>
<tr><td>Azophloxin</td><td>0.5g</td></tr>
<tr><td>Acetic acid</td><td>0.6mL</td></tr>
<tr><td colspan="2">mix, and add distilled water (100mL)</td></tr>
<tr><td colspan="2" style="font-weight:bold;">c) Final working stain solution</td></tr>
<tr><td>Ponceau-fuchsin solution</td><td>5-10mL</td></tr>
<tr><td>Azophloxin</td><td>2mL</td></tr>
<tr><td>0.2% acetic acid solution</td><td>88mL</td></tr>
</table>
3. Light Green Solution
<table style="margin-left:40px;" border="0">
<tr><td>Light Green</td><td>1g</td></tr>
<tr><td>acetic acid</td><td>1mL</td></tr>
<tr><td colspan="2">Mix, and add distilled water (500mL)</td></tr>
</table>
4. Phophomolybdic acid-Orange G solution
<table style="margin-left:40px;" border="0">
<tr><td>Phosphomolybdic acid</td><td>3g</td></tr>
<tr><td>Orange G</td><td>2g</td></tr>
<tr><td colspan="2">Dissolve in 500mL of distilled water and add crystal thymol.</td></tr>
</table>
Von Kossa Stain
<table style="margin-left:40px;" border="0">
<tr><td>1% aqueous silver nitrate</td></tr>
<tr><td>2.5% sodium thiosulfate</td></tr>
<tr><td>1% safranin O</td></tr>
</table>
Alcian blue stain
<table style="margin-left:40px;" border="0">
<tr><td>Alcian blue 8GX</td><td>1g</td></tr>
<tr><td>3% acetic acid solution</td><td>100mL</td></tr>
</table>
Hemotoxylin and Eosin stain
 <table style="margin-left:40px;" border="0">
<tr><td colspan="2" style="font-weight:bold;">a)Harris's hemotoxylin</td></tr>
<tr><td>Hemotoxylin</td><td>2.5g</td></tr>
<tr><td>Absolute alcohol</td><td>25mL</td></tr>
<tr><td>Potassium Alum</td><td>50g</td></tr>
<tr><td>distilled water</td><td>500mL</td></tr>
<tr><td>mercuric oxide</td><td>1.25g OR</td></tr>
<tr><td>Sodium iodate</td><td>0.5g</td></tr>
<tr><td>Glacial acetic acid</td><td>20mL</td></tr>
<tr><td colspan="2" style="font-weight:bold;">b) Eosin solution</td></tr>
<tr><td colspan="2">Commercially produced Eosin was used.</td></tr>
</table>
All stain dye powders are Gurr dye powders. 
 All reagents are analytical reagents, and not Lab reagents
Fluorochromes
<table border="1" cellspacing="0" cellpadding="0">
 <tr>
 <td> 
 Manufacturer </td>
 <td>Fluorochrome</td>
 <td>Catalogue Number</td>
 </tr>
 <tr>
 <td>Sigma-Aldrich, Sydney</td>
 <td>Calcein Green</td>
 <td>C0875</td>
 </tr>
 <tr>
 <td>Sigma-Aldrich, Sydney</td>
 <td>Alizarin Complexone </td>
 <td>A3882</td>
 </tr>
 <tr>
 <td>Intervet Australia, Victoria</td>
 <td>Oxytetracycline 
 (off the shelf antimicrobial drug)</td>
 <td>Tradename; Engemycin 100</td>
 </tr>
</table>

undecalcified bone preparation for histology, histomorphometry and fluorochrome analysis

Undecalcified bone histology demonstrates the micro-architecture of bone. It shows both the mineralised and cellular components of bone, which provides vital information on bone turnover or bone formation and resorption. This has tremendous importance in a variety of clinical and research applications. It yields beautiful images1 and allows for techniques such as fluorochrome assessment and histomorphometry2. Fluorochrome analysis is a technique where fluorescent dyes that bind to calcium are injected at a particular time point, which allows for quantification of the amount of mineralisation at that given time. Histomorphometry is a process of bone quantification at the microscopic level. 
Performing undecalcified bone histology is technically challenging, particularly with large size specimens. It requires variations in technique from those used in standard paraffin embedded histology. This video illustrates the process of producing good quality sections and demonstrates the technical difficulties and methods with which to overcome them. Specimen preparation, fixation and processing are achieved with a manner similar to other soft tissues, however due to the density and lower permeability of bone considerably longer fixation and processing times are required, often taking several weeks. Embedding is achieved using a supporting medium with similar or equal hardness and density to the bone such as methacrylate- based resins, but unlike paraffin infiltration and embedding, this is an irreversible step. Sectioning can be achieved by grinding which produces a thicker section, which is optimal for studies such as fluorochrome analysis. This is best achieved using a diamond blade on a macrotome. Alternatively, thinner sections can be produced for light microscopy and this is achieved using a sledge microtome with a very sharp blade. The sledge microtome provides the additional strength and stability required for large, hard blocks. Resin embedded sections can be stained with a variety of stains, which are demonstrated.

Watch this Scientific Journal Video about Undecalcified Bone Preparation for Histology, Histomorphometry and Fluorochrome Analysis at JoVE.com

Undecalcified Bone Preparation for Histology, Histomorphometry and Fluorochrome Analysis

Undecalcified bone histology provides important information for a variety of clinical and research applications. It is technically challenging, particularly with large size specimens. This video illustrates the process of producing good quality sections and demonstrates the technical difficulties and methods with which to overcome them.

Undecalcified bone histology demonstrates the micro-architecture of bone. It shows both the mineralised and cellular components of bone, which provides ...

undecalcified-bone-preparation-for-histology-histomorphometry

Research

JoVE Journal

Biology

The Preparation of Primary Hematopoietic Cell Cultures From Murine Bone Marrow for Electroporation

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell  electroporation system and Gene Pulser  electroporation buffer were specifically developed to transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells.This video demonstrates how to establish primary hematopoietic cell cultures from murine bone marrow, and then prepare them for electroporation in the MXcell system. We begin by isolating femur and tibia. Bone marrow from both femur and tibia are then harvested and cultures are established. Cultured bone marrow cells are then transfected and analyzed.

This procedure describes how to establish primary hematopoietic cell cultures from murine bone marrow and is followed by transfection using the Gene Pulser MXCell electroporation system.

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser ...

A Neuronal and Astrocyte Co-Culture Assay for High Content Analysis of Neurotoxicity

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing measurement of multiple cellular phenotypes within a single assay. In this study, we utilized HCA to develop a novel assay for neurotoxicity. Neurotoxicity assessment represents an important part of drug safety evaluation, as well as being a significant focus of environmental protection efforts. Additionally, neurotoxicity is also a well-accepted in vitro marker of the development of neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Recently, the application of HCA to neuronal screening has been reported. By labeling neuronal cells with &beta;III-tubulin, HCA assays can provide high-throughput, non-subjective, quantitative measurements of parameters such as neuronal number, neurite count and neurite length, all of which can indicate neurotoxic effects. However, the role of astrocytes remains unexplored in these models. Astrocytes have an integral role in the maintenance of central nervous system (CNS) homeostasis, and are associated with both neuroprotection and neurodegradation when they are activated in response to toxic substances or disease states. GFAP is an intermediate filament protein expressed predominantly in the astrocytes of the CNS. Astrocytic activation (gliosis) leads to the upregulation of GFAP, commonly accompanied by astrocyte proliferation and hypertrophy. This process of reactive gliosis has been proposed as an early marker of damage to the nervous system. The traditional method for GFAP quantitation is by immunoassay. This approach is limited by an inability to provide information on cellular localization, morphology and cell number. We determined that HCA could be used to overcome these limitations and to simultaneously measure multiple features associated with gliosis - changes in GFAP expression, astrocyte hypertrophy, and astrocyte proliferation - within a single assay. In co-culture studies, astrocytes have been shown to protect neurons against several types of toxic insult and to critically influence neuronal survival. Recent studies have suggested that the use of astrocytes in an in vitro neurotoxicity test system may prove more relevant to human CNS structure and function than neuronal cells alone. Accordingly, we have developed an HCA assay for co-culture of neurons and astrocytes, comprised of protocols and validated, target-specific detection reagents for profiling &beta;III-tubulin and glial fibrillary acidic protein (GFAP). This assay enables simultaneous analysis of neurotoxicity, neurite outgrowth, gliosis, neuronal and astrocytic morphology and neuronal and astrocytic development in a wide variety of cellular models, representing a novel, non-subjective, high-throughput assay for neurotoxicity assessment. The assay holds great potential for enhanced detection of neurotoxicity and improved productivity in neuroscience research and drug discovery.

This article describes a novel protocol and reagent set designed for sensitive measurement of neurotoxic effects of compounds and treatments on co-cultures of neurons and astrocytes using high content analysis. Results demonstrate that high content analysis represents an exciting novel technology for neurotoxicity assessment.

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing ...

Preparation of Adult Drosophila Eyes for Thin Sectioning and Microscopic Analysis

Drosophila has long been used as model system to study development, mainly due to the ease with which it is genetically tractable. Over the years, a plethora of mutant strains and technical tricks have been developed to allow sophisticated questions to be asked and answered in a reasonable amount of time. Fundamental insight into the interplay of components of all known major signaling pathways has been obtained in forward and reverse genetic Drosophila studies. The fly eye has proven to be exceptionally well suited for mutational analysis, since, under laboratory conditions, flies can survive without functional eyes. Furthermore, the surface of the insect eye is composed of some 800 individual unit eyes (facets or ommatidia) that form a regular, smooth surface when looked at under a dissecting microscope. Thus, it is easy to see whether a mutation might affect eye development or growth by externally looking for the loss of the smooth surface ('rough eye' phenotype; Fig. 1) or overall eye size, respectively (for examples of screens based on external eye morphology see e.g.1). Subsequent detailed analyses of eye phenotypes require fixation, plastic embedding and thin-sectioning of adult eyes.
The Drosophila eye develops from the so-called eye imaginal disc, a bag of epithelial cells that proliferate and differentiate during larval and pupal stages (for review see e.g. 2). Each ommatidium consists of 20 cells, including eight photoreceptors (PR or R-cells; Fig. 2), four lens-secreting cone cells, pigment cells ('hexagon' around R-cell cluster) and a bristle. The photoreceptors of each ommatidium, most easily identified by their light sensitive organelles, the rhabdomeres, are organized in a trapezoid made up of the six "outer" (R1-6) and two "inner" photoreceptors (R7/8; R8 [Fig. 2] is underneath R7 and thus only seen in sections from deeper areas of the eye). The trapezoid of each facet is precisely aligned with those of its neighbors and the overall anteroposterior and dorsoventral axes of the eye (Fig. 3A). In particular, the ommatidia of the dorsal and ventral (black and red arrows, respectively) halves of the eye are mirror images of each other and correspond to two chiral forms established during planar cell polarity signaling (for review see e.g. 3).
The method to generate semi-thin eye sections (such as those presented in Fig. 3) described here is slightly modified from the one originally described by Tomlinson and Ready4. It allows the morphological analysis of all cells except for the transparent cone cells. In addition, the pigment of R-cells (blue arrowheads in Fig. 2 and 3) can be used as a cell-autonomous marker for the genotype of a R-cell, thus genetic requirements of genes in a subset of R-cells can readily be determined5,6.

Preparation of Adult Drosophila Eyes for Thin Sectioning and Microscopic Analysis

A standard approach to prepare adult Drosophila eyes for semi-thin sectioning and light microscopic analysis is presented here. The protocol can be used for gross morphological analysis of eye defects, or with the indicated adjustments can be used to determine genetic requirements of genes in specific cell types of the eye (e.g. clonal analysis of photoreceptors) or for electron microscopic analysis.

Drosophila has long been used as model system to study development, mainly due to the ease with which it is genetically tractable. Over the years, a ...

Bone Conditioned Medium: Preparation and Bioassay

Autologous bone grafts are widely used in oral and maxillofacial surgery, orthopedics, and traumatology. Autologous bone grafts not only replace missing bone, they also support the complex process of bone regeneration. This favorable behavior of autografts is attributed to the three characteristics: osteoconductivity, osteogenicity, and osteoinductivity. However, there is another aspect: Bone grafts release a myriad of molecules, including growth factors, which can target mesenchymal cells involved in bone regeneration. The paracrine properties of bone grafts can be studied in vitro by the use of bone-conditioned medium (BCM). Here we present a protocol on how to prepare bone-conditioned medium from native pig cortical bone, and bone that underwent thermal processing or demineralization. Cells can be directly exposed to BCM or seeded onto biomaterials, such as collagen membranes, previously soaked with BCM. We give examples for in vitro bioassays with mesenchymal cells on the expression of TGF-&#946; regulated genes. The presented protocols should encourage to further reveal the paracrine effects of bone grafts during bone regeneration and open a path for translational research in the broad field of reconstructive surgery.

We describe here how to prepare bone-conditioned medium (BCM) and test its activity in vitro.

Autologous bone grafts are widely used in oral and maxillofacial surgery, orthopedics, and traumatology. Autologous bone grafts not only replace missing ...

Sample Preparation for Mass Cytometry Analysis

Mass cytometry utilizes antibodies conjugated with heavy metal labels, an approach that has greatly increased the number of parameters and opportunities for deep analysis well beyond what is possible with conventional fluorescence-based flow cytometry. As with any new technology, there are critical steps that help ensure the reliable generation of high-quality data. Presented here is an optimized protocol that incorporates multiple techniques for the processing of cell samples for mass cytometry analysis. The methods described here will help the user avoid common pitfalls and achieve consistent results by minimizing variability, which can lead to inaccurate data. To inform experimental design, the rationale behind optional or alternative steps in the protocol and their efficacy in uncovering new findings in the biology of the system being investigated is covered. Lastly, representative data is presented to illustrate expected results from the techniques presented here.

This article describes the collection and processing of samples for mass cytometry analysis.

Mass cytometry utilizes antibodies conjugated with heavy metal labels, an approach that has greatly increased the number of parameters and opportunities ...

Tissue Collection and RNA Extraction from the Human Osteoarthritic Knee Joint

Osteoarthritis (OA) is a chronic and degenerative joint disease most often affecting the knee. As there is currently no cure, total knee arthroplasty (TKA) is a common surgical intervention. Experiments using primary human OA tissues obtained from TKA provide the capability to investigate disease mechanisms ex vivo. While OA was previously thought to impact mainly the cartilage, it is now known to impact multiple tissues in the joint. This protocol describes patient selection, sample processing, tissue homogenization, RNA extraction, and quality control (based on RNA purity, integrity, and yield) from each of seven unique tissues to support disease mechanism investigation in the knee joint. With informed consent, samples were obtained from patients undergoing TKA for OA. Tissues were dissected, washed, and stored within 4 h of surgery by flash freezing for RNA or formalin fixation for histology. Collected tissues included articular cartilage, subchondral bone, meniscus, infrapatellar fat pad, anterior cruciate ligament, synovium, and vastus medialis oblique muscle. RNA extraction protocols were tested for each tissue type. The most significant modification involved the method of disintegration used for low-cell, high-matrix, hard tissues (considered as cartilage, bone, and meniscus) versus relatively high-cell, low-matrix, soft tissues (considered as fat pad, ligament, synovium, and muscle). It was found that pulverization was appropriate for hard tissues, and homogenization was appropriate for soft tissues. A proclivity for some subjects to yield higher RNA integrity number (RIN) values than other subjects consistently across multiple tissues was observed, suggesting that underlying factors such as disease severity may impact RNA quality. The ability to isolate high-quality RNA from primary human OA tissues provides a physiologically relevant model for sophisticated gene expression experiments, including sequencing, that can lead to clinical insights that are more readily translated to patients.

Primary tissues obtained from patients following total knee arthroplasty provide an experimental model for osteoarthritis research with maximal clinical translatability. This protocol describes how to identify, process, and isolate RNA from seven unique knee tissues to support mechanistic investigation in human osteoarthritis.

Osteoarthritis (OA) is a chronic and degenerative joint disease most often affecting the knee. As there is currently no cure, total knee arthroplasty ...

Using Real-Time Cell Metabolic Flux Analyzer to Monitor Osteoblast Bioenergetics

Bone formation by osteoblasts is an essential process for proper bone acquisition and bone turnover to maintain skeletal homeostasis, and ultimately, prevent fracture. In the interest to both optimize peak bone mass and combat various musculoskeletal diseases (i.e., post-menopausal osteoporosis, anorexia nervosa, type 1 and 2 diabetes mellitus), incredible efforts have been made in the field of bone biology to fully characterize osteoblasts throughout their differentiation process. Given the primary role of mature osteoblasts to secrete matrix proteins and mineralization vesicles, it has been noted that these processes take an incredible amount of cellular energy, or adenosine triphosphate (ATP). The overall cellular energy status is often referred to as cellular bioenergetics, and it includes a series of metabolic reactions that sense substrate availability to derive ATP to meet cellular needs. Therefore, the current method details the process of isolating primary, murine bone marrow stromal cells (BMSCs) and monitoring their bioenergetic status using the Real-time cell metabolic flux analyzer at various stages in osteoblast differentiation. Importantly, these data have demonstrated that the metabolic profile changes dramatically throughout osteoblast differentiation. Thus, using this physiologically relevant cell type is required to fully appreciate how a cell's bioenergetic status can regulate the overall function.

Real-time cell metabolic flux assay measures the oxygen consumption rate and extracellular acidification rate, which corresponds to mitochondrial and glycolytic adenosine triphosphate production, using pH and oxygen sensors. The manuscript explains a method to understand the energy status of osteoblasts and the characterization and interpretation of the cellular bioenergetic status.

Bone formation by osteoblasts is an essential process for proper bone acquisition and bone turnover to maintain skeletal homeostasis, and ultimately, ...

An Improved Chemotaxis Assay for the Rapid Identification of Rhizobacterial Chemoattractants in Root Exudates

Chemotaxis identification is very important for the research and application of rhizosphere growth-promoting bacteria. We established a straightforward method to quickly identify the chemoattractants that could induce the chemotactic movement of rhizosphere growth-promoting bacteria on sterile glass slides via simple steps. Bacteria solution (OD600 = 0.5) and sterile chemoattractant aqueous solution were added dropwise on the glass slide at an interval of 1 cm. An inoculating loop was used to connect the chemoattractant aqueous solution to the bacterial solution. The slide was kept at room temperature for 20 min on the clean bench. Finally, the chemoattractant aqueous solution was collected for bacterial counting and microscopic observation. In this study, through multiple comparisons of experimental results, the method overcame multiple shortcomings of traditional bacterial chemotaxis methods. The method reduced the error of plate counting and shortened the experimental cycle. For the identification of chemoattractant substances, this new method can save 2-3 days compared to the traditional method. Additionally, this method allows any researcher to systematically complete a bacterial chemotaxis experiment within 1-2 days. The protocol can be considered a valuable resource for understanding plant-microbe interactions.

Here, we present an improved chemotaxis assay protocol. The goal of this protocol is to reduce the steps and costs of traditional bacterial chemotaxis methods and to serve as a valuable resource for understanding plant-microbe interactions.

Chemotaxis identification is very important for the research and application of rhizosphere growth-promoting bacteria. We established a straightforward ...

Artificial Cartilage Implants for Bone Regeneration via Endochondral Ossification

Integrated Bone Formation Through In Vivo Endochondral Ossification Using Mesenchymal Stem Cells

Conventional bone regeneration therapy using mesenchymal stem cells (MSCs) is difficult to apply to bone defects larger than the critical size because it does not have a mechanism to induce angiogenesis. Implanting artificial cartilage tissue fabricated from MSCs induces angiogenesis and bone formation in vivo via endochondral ossification (ECO). Therefore, this ECO-mediated approach may be a promising bone regeneration therapy in the future. An important aspect of the clinical application of this ECO-mediated approach is establishing a protocol for preparing enough cartilage to be implanted to repair the bone defect. It is especially not practical to design a single mass of grafted cartilage of a size that conforms to the shape of the actual bone defect. Therefore, the cartilage to be transplanted must have the property of forming bone integrally when multiple pieces are implanted. Hydrogels may be an attractive tool for scaling up tissue-engineered grafts for endochondral ossification to meet clinical requirements. Although many naturally derived hydrogels support MSC cartilage formation in vitro and ECO in vivo, the optimal scaffold material to meet the needs of clinical applications has yet to be determined. Hyaluronic acid (HA) is a crucial component of the cartilage extracellular matrix and is a biodegradable and biocompatible polysaccharide. Here, we show that HA hydrogels have excellent properties to support in vitro differentiation of MSC-based cartilage tissue and promote endochondral bone formation in vivo.

Author Spotlight: Enhancing Bone Regeneration with Vascularized Artificial Cartilage Integration 

Bone therapy via endochondral ossification by implanting artificial cartilage tissue produced from mesenchymal stem cells has the potential to circumvent the drawbacks of conventional therapies. Hyaluronic acid hydrogels are effective in scaling up uniformly differentiated cartilage grafts as well as creating integrated bone with vascularization between fused grafts in vivo.

Conventional bone regeneration therapy using mesenchymal stem cells (MSCs) is difficult to apply to bone defects larger than the critical size because it ...

High-Quality Sample Preparation for Multiome 10X Genomics Analysis

High-Quality Brain and Bone Marrow Nuclei Preparation for Single Nuclei Multiome Assays

Single-cell analysis has become the approach of choice for unraveling the complexity of biological processes that require assessing the variability of individual cellular responses to treatment or infection with single-cell resolution. 
Many techniques for single-cell molecular profiling have been developed over the past 10 years, and several dedicated technologies have been commercialized. The 10X Genomics droplet-based single-cell profiling is a widespread technology that offers ready-to-use reagents for transcriptomic and multi-omic single-cell profiling. The technology includes workflows for single-cell and single-nuclei RNA sequencing (scRNA-Seq and snRNA-Seq, respectively), scATAC-Seq, single-cell immune profiling (BCR/TCR sequencing), and multiome. The latter combines transcriptional (scRNA-Seq) and epigenetic information (scATAC-Seq) coming from the same cell. 
The quality (viability, integrity, purity) of single-cell or single-nuclei suspensions isolated from tissues and analyzed by any of these approaches is critical for generating high-quality data. Therefore, the sample preparation protocols should be adapted to the particularities of each biological tissue and ensure the generation of high-quality cell and nuclei suspensions.
This article describes two protocols for preparing brain and bone marrow samples for the downstream multiome 10X Genomics pipeline. The protocols are performed stepwise and cover tissue dissociation, cell sorting, nuclei isolation, and quality control of prepared nuclei suspension that is used as starting material for cell partitioning and barcoding, library preparation, and sequencing. These standardized protocols produce high-quality nuclei libraries and robust and reliable data.

Author Spotlight: Advancing Biomedical Research Through Single Cell Analysis 

The success of single-cell/single-nuclei transcriptomics and multi-omics largely depends on the quality of cells/nuclei. Therefore, isolating cells/nuclei from tissue and their purification must be highly standardized. This protocol describes the preparation of nuclei from the brain and bone marrow for downstream single-nuclei multiome assay.

Single-cell analysis has become the approach of choice for unraveling the complexity of biological processes that require assessing the variability of ...