Localization of mRNAs and proteins in methyl methacrylate-embedded tissues

Streamlined Full-Length Total RNA Sequencing of Paraformaldehyde-Fixed Brain Tissues

Paraformaldehyde (PFA) fixation is the preferred method for preserving tissue architecture for anatomical and pathological observations. Meanwhile, PFA reacts with the amine groups of biomolecules to form chemical cross-linking, which preserves RNA within the tissue. This has great prospects for RNA sequencing to characterize the molecular underpinnings after anatomical and pathological observations. However, RNA is inaccessible due to cross-linked adducts forming between RNA and other biomolecules in prolonged PFA-fixed tissue. It is also difficult to perform reverse transcription and PCR, resulting in low sequencing sensitivity and reduced reproducibility. Here, we developed a method to perform RNA sequencing in PFA-fixed tissue, which is easy to use, cost-effective, and allows efficient sample multiplexing. We employ cross-link reversal to recover RNA and library construction using random primers without artificial fragmentation. The yield and quality of recovered RNA significantly increased through our method, and sequencing quality metrics and detected genes did not show any major differences compared with matched fresh samples. Moreover, we applied our method for gene expression analysis in different regions of the mouse brain and identified unique gene expression profiles with varied functional implications. We also find significant dysregulation of genes involved in Alzheimer's disease (AD) pathogenesis within the medial septum (MS)/vertical diagonal band of Broca (VDB) of the 5×FAD mouse brain. Our method can thus increase the performance of high-throughput RNA sequencing with PFA-fixed samples and allows longitudinal studies of small tissue regions isolated by their in situ context.

Histology Strategies for Medical Implants and Interventional Device Studies

Histology of medical devices poses a variety of unique challenges. Comprehensive histologic assessment of medical devices often requires spatial context and high-quality retention of the device–tissue interface. However, the composition of many medical devices is often not amenable to traditional paraffin embedding and thus alternative specialized methodologies such as hard resin embedding must be used. Hard resin embedding requires specialized laboratory technical expertise and equipment, and the fixation techniques and resin composition used markedly impact the feasibility of immunohistochemistry. For the continuity of spatial context during histologic evaluation, additional imaging methods such as macrophotography, radiography, micro-Computerized Tomography (microCT), or magnetic resonance imaging (MRI) can be used to guide sectioning and to complement histologic findings. Although standardized approaches are scarce for medical devices, important considerations specific to medical device histology are discussed, including general specimen preparation, special considerations for devices by organ system, and the challenges of immunohistochemistry. Histologic preparation of medical devices must be thoughtful, thorough, and tailored to achieve optimal histologic outcomes for complex, valuable, and often limited implant specimens.

Immunohistochemical Studies of Cytoskeletal and Extracellular Matrix Components in Dogfish Scyliorhinus canicula L. Notochordal Cells

Immunofluorescence and immunohistochemical techniques were used to define the distribution of cytoskeletal (cytokeratin 8, vimentin) and extracellular matrix components (collagen type I, collagen type II, hyaluronic acid, and aggrecan) and bone morphogenetic proteins 4 and 7 (BMP4 and BMP7) in the notochord of the lesser spotted dogfish Scyliorhinus canicula L. Immunolocalization of hyaluronic acid was observed in the notochord, vertebral centrum, and neural and hemal arches, while positive labeling to aggrecan was observed in the ossified centrum, notochord, and the perichondrium of the hyaline cartilage. Type I collagen was observed in the mineralized cartilage of the vertebral bodies, the notochord, the fibrocartilage of intervertebral disc, and the perichondrium. A positive labeling to type II collagen was observed in the inner part of the cartilaginous vertebral centrum and the notochord, as well as in the neural arch and muscle tissue, but there was no appreciable labeling of the hyaline cartilage. The presence of both BMP4 and BMP7 was seen in the mineralized vertebral centrum, notochordal cells, and neural arch. The notochordal cells expressed both cytokeratin 8 and vimentin, but predominantly vimentin. Hyaluronic acid, collagen type I, and collagen type II expression confirmed the presence of a mixture of notochordal and fibrocartilaginous tissue in the intervertebral disc, while BMPs confirmed the presence of an ossification in the cartilaginous skeleton of the spotted dogfish.

Form and function of the intervertebral disc in health and disease: a morphological and stain comparison study

Multiple histologic measurements are commonly used to assess degenerative changes in intervertebral disc (IVD) structure; however, there is no consensus on which stains offer the clearest visualization of specific areas within the IVD. The objective of this study was to compare multiple tinctorial stains, evaluate their ability to highlight structural features within the IVD, and investigate how they influence the capacity to implement a degeneration scoring system. Lumbar IVDs from seven human autopsy specimens were stained using six commonly used stains (Hematoxylin/Eosin, Toluidine Blue, Safranin-O/Fast Green, Extended FAST, modified Gomori's Trichrome, and Picrosirius Red Alcian Blue). All IVDs were evaluated by three separate graders to independently determine which stains (i) were most effective at discerning different structural features within different regions of the IVDs and (ii) allowed for the most reproducible assessment of degeneration grade, as assessed via the Rutges histological scoring system (Rutges et al. A validated new histological classification for intervertebral disc degeneration. Osteoarthritis Cartilage, 21, 2039-47). Although Trichrome, XFAST and PR/AB stains were all effective at highlighting different regions of whole IVDs, we recommend the use of PR/AB because it had the highest degree of rater agreement on assigned degeneration grade, allowed greater resolution of degeneration grade, has an inferential relationship between color and composition, and allowed clear differentiation of the different regions and structural disruptions within the IVD. The use of a standard set of stains together with a histological grading scheme can aid in the characterization of structural changes in different regions of the IVD and may simplify comparisons across the field. This collection of human IVD histological images highlights how IVD degeneration is not a single disease but a composite of multiple processes such as aging, injury, repair, and disease, each of which are unique to the individual.

Small leucine-rich proteoglycans in the vertebrae of Atlantic salmon Salmo salar

We analysed the distribution and expression of the small leucine-rich proteoglycans (SLRPs) decorin, biglycan and lumican in vertebral columns of Atlantic salmon Salmo salar L. with and without radiographically detectable deformities. Vertebral deformities are a reoccurring problem in salmon and other intensively farmed species, and an understanding of the components involved in the pathologic development of the vertebrae is important in order to find adequate solutions to this problem. Using immunohistology and light microscopy, we found that in non-deformed vertebrae biglycan, lumican and decorin were all expressed in osteoblasts at the vertebral growth zones and at the ossification front of the chondrocytic arches. Hence, the SLRPs are expressed in regions where intramembranous and endochondral ossification take place. In addition, mRNA expression of biglycan, decorin and lumican was demonstrated in a primary osteoblast culture established from Atlantic salmon, supporting the in vivo findings. Transcription of the SLRPs increased during differentiation of the osteoblasts in vitro and where lumican mRNA expression increased later in the differentiation compared with decorin and biglycan. Intriguingly, in vertebral fusions, biglycan, decorin and lumican protein expression was extended to trans-differentiating cells at the border between arch centra and osteoblast growth zones. In addition, mRNA expression of biglycan, decorin and lumican differed between non-deformed and fused vertebrae, as shown by quantitative PCR (qPCR). Western blotting revealed an additional band of biglycan in fused vertebrae which had a higher molecular weight than in non-deformed vertebrae. Fourier-transform infrared (FTIR) spectroscopy revealed more spectral focality in the endplates of vertebral fusions and significantly more non-reducible collagen crosslinks compared with non-deformed vertebrae, thus identifying differences in bone structure.

Exercise induced mechano-sensing and substance P mediated bone modeling in Atlantic salmon

Mechanical stress plays a vital role in maintaining bone architecture. The process by which osteogenic cells convert the mechanical signal into a biochemical response governing bone modeling is not clear, however. In this study, we investigated how Atlantic salmon (Salmo salar) vertebra responds to exercise-induced mechanical loading. Bone formation in the vertebrae was favored through increased expression of genes involved in osteoid production. Fourier transform infrared spectroscopy (FT-IR) showed that bone matrix secreted both before and during sustained swimming had different properties after increased load compared to control, suggesting that both new and old bones are affected. Concomitantly, both osteoblasts and osteocytes in exercised salmon showed increased expression of the receptor nk-1 and its ligand substance P (SP), both known to be involved in osteogenesis. Moreover, in situ hybridization disclosed SP mRNA in osteoblasts and osteocytes, supporting an autocrine function. The functional role of SP was investigated in vitro using osteoblasts depleted for SP. The cells showed severely reduced transcription of genes involved in mineralization, demonstrating a regulatory role for SP in salmon osteoblasts. Investigation of α-tubulin stained osteocytes revealed cilia-like structures. Together with SP, cilia may link mechanical responses to osteogenic processes in the absence of a canaliculi network. Our results imply that salmon vertebral bone responds to mechanical load through a highly interconnected and complex signal and detection system, with SP as a key factor for initializing mechanically-induced bone formation in bone lacking the canaliculi system.

An immunocytochemical procedure for protein localization in various nematode life stages combined with plant tissues using methylacrylate-embedded specimens

Plant-parasitic nematodes possess a large number of proteins that are secreted in planta, allowing them to be successful parasites of plants. The majority of these proteins are synthesized mainly in the nematode subventral and dorsal glands as well as in other organs. To improve the immunovisualization of these proteins, we adapted a methacrylate embedding method for the localization of proteins inside nematode tissues, and extracellularly when secreted in planta or within plant cells. An important advantage is that the method is applicable for all nematode stages: preparasitic as well as parasitic stages, including large mature females. Herein, the method has been successfully applied for the localization of four nematode secreted proteins, such as Mi-MAP-1, Mi-CBM2-bearing proteins, Mi-PEL3, and Mi-6D4. In addition, we could also localize 14-3-3 proteins, as well as two cytoskeletal proteins, by double-immunolabeling on preparasitic juveniles. Superior preservation of nematode and plant morphology, allowed more accurate protein localization as compared with other methods. Besides excellent epitope preservation, dissolution of methacrylate from tissue sections unmasks target proteins and thereby drastically increases antibody access.

Molecular pathology of vertebral deformities in hyperthermic Atlantic salmon (Salmo salar)

Background

Hyperthermia has been shown in a number of organisms to induce developmental defects as a result of changes in cell proliferation, differentiation and gene expression. In spite of this, salmon aquaculture commonly uses high water temperature to speed up developmental rate in intensive production systems, resulting in an increased frequency of skeletal deformities. In order to study the molecular pathology of vertebral deformities, Atlantic salmon was subjected to hyperthermic conditions from fertilization until after the juvenile stage.

Results

Fish exposed to the high temperature regime showed a markedly higher growth rate and a significant higher percentage of deformities in the spinal column than fish reared at low temperatures. By analyzing phenotypically normal spinal columns from the two temperature regimes, we found that the increased risk of developing vertebral deformities was linked to an altered gene transcription. In particular, down-regulation of extracellular matrix (ECM) genes such as col1a1, osteocalcin, osteonectin and decorin, indicated that maturation and mineralization of osteoblasts were restrained. Moreover, histological staining and in situ hybridization visualized areas with distorted chondrocytes and an increased population of hypertrophic cells. These findings were further confirmed by an up-regulation of mef2c and col10a, genes involved in chondrocyte hypertrophy.

Conclusion

The presented data strongly indicates that temperature induced fast growth is severely affecting gene transcription in osteoblasts and chondrocytes; hence change in the vertebral tissue structure and composition. A disrupted bone and cartilage production was detected, which most likely is involved in the higher rate of deformities developed in the high intensive group. Our results are of basic interest for bone metabolism and contribute to the understanding of the mechanisms involved in development of temperature induced vertebral pathology. The findings may further conduce to future molecular tools for assessing fish welfare in practical farming.

Morphological and molecular characterization of developing vertebral fusions using a teleost model

BACKGROUND

Spinal disorders are a major cause of disability for humans and an important health problem for intensively farmed animals. Experiments have shown that vertebral deformities present a complex but comparable etiology across species. However, the underlying molecular mechanisms involved in bone deformities are still far from understood. To further explicate the mechanisms involved, we have examined the fundamental aspects of bone metabolism and pathogenesis of vertebral fusions in Atlantic salmon (Salmo salar).

RESULTS

Experimentally, juvenile salmon were subjected to hyperthermic conditions where more than 28% developed fused vertebral bodies. To characterize the fusion process we analyzed an intermediate and a terminal stage of the pathology by using x-ray, histology, immunohistochemistry, real-time quantitative PCR and in situ hybridization. At early stage in the fusion process, disorganized and proliferating osteoblasts were prominent at the growth zones of the vertebral body endplates. PCNA positive cells further extended along the rims of fusing vertebral bodies. During the developing pathology, the marked border between the osteoblast growth zones and the chondrocytic areas connected to the arches became less distinct, as proliferating cells and chondrocytes blended through an intermediate zone. This cell proliferation appeared to be closely linked to fusion of opposing arch centra. During the fusion process a metaplastic shift appeared in the arch centra where cells in the intermediate zone between osteoblasts and chondrocytes co-expressed mixed signals of chondrogenic and osteogenic markers. A similar shift also occurred in the notochord where proliferating chordoblasts changed transcription profile from chondrogenic to also include osteogenic marker genes. In progressed fusions, arch centra and intervertebral space mineralized.

CONCLUSION

Loss of cell integrity through cell proliferation and metaplastic shifts seem to be key events in the fusion process. The fusion process involves molecular regulation and cellular changes similar to those found in mammalian deformities, indicating that salmon is suitable for studying general bone development and to be a comparative model for spinal deformities.