Regenerating Cartilage

This study shows zebrafish can regenerate cartilage throughout their life, and the role played in that by the vitmain A metabolite retinoic acid – implications for using retinoic acid agonists as treatment in humans for diseases such as osteochondromas.

Read the published research article here

Image from work by Claire Arata and colleagues

Eli and Edythe Broad California Institute for Regenerative Medicine Center for Regenerative Medicine & Stem Cell Research, Department of Stem Cell Biology & Regenerative Medicine, University of Southern California Keck School of Medicine, LA, CA, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY-NC 4.0)

Published in bioRxiv, May 2024 (not peer reviewed)

A section of tissue is taken as it would for Histology (see prev post)

The section is then treated with an antibody that recognises the marker we’re looking for. This is referred to as the primary antibody.

The primary antibody is then recognised by a secondary antibody that is linked to an enzyme, or several copies of the enzymes (conjugates).

Finally, the section is treated with a chromogen, a reagent that is acted upon by the enzyme, to deposit an insoluble coloured compound onto the cell, where the original primary antibody had bound.

A molecule that binds to, and is recognised by, an antibody, is called an antigen, 

In histology, antigens = markers, since they act as ways of recognising a particular cell. 

Many markers are designated by a CD number. 

EG different classes of lymphocyte appear virtually identical in size and shape (morphology), but they can be distinguished according to their surface markers. 

All T lymphocytes express CD3, 

Helper T cells and cytotoxic T cells express CD4 and CD8, respectively.

Therefore, a T cell lymphoma can be tracked in different tissues using these markers.

 Double immunolabelling of an islet of Langerhans in the pancreas identifies Insulin-producing cells (blue) and glucagon-producing cells (brown)

Another use for IHC is in guiding treatment. 

The glorious dentate gyrus of the hippocampus. Green (GFP) stains astrocytes. Red (mcherry) stains double cortin, proteins present in immature neurons. Blue (DAPI) stains cell bodies.

🗣️ The Sebaceous Man 🗣️

Destined to become the head of a pimple

i❤️histo

This image shows a section through the skin. The stratified squamous epithelium of the epidermis appears as numerous stacked nuclei at the bottom of the image (forming the man’s shoulders and turtle neck) while the dense irregular collagen fibers of the dermis occupy the remaining image (surrounding the man’s head).

The head itself is composed of the specialized lipid secreting epithelial cells of a sebaceous gland. These glands release sebum, an oily substance that is essential for preventing the skin from drying out and also helps to forming a waterproof barrier between the outside world and your epidermis. The cells of the gland are organized into sub-units called acini (translates as: ‘berry’ or ‘grape’ as in shaped like a berry or a bunch of grapes) and have a duct that opens onto the surface of the epidermis. Sometimes the duct can get blocked and the gland can become inflamed which causes a pimple to form.

This particular image was prepared using immunohistochemistry a process where antibodies are used to demonstrate specific proteins/molecules in tissues. In this case the antibody used was D2-40 which binds to a human mucoprotein (the antigen) called podoplanin. This protein is found in numerous regions of the body but is frequently used by histologists to label the endothelial cells of lymphatic vessels. In this skin section you can see that it also labels the periphery of sebaceous glands and hairs (brown). 

The stain could be useful in certain circumstances to see if a tumor is derived from lymph tissues or to see if there has been lymphatic invasion within a tumor, but it could also be used to see if a skin carcinoma originated from those cells associated with the skin that normally bind the antibody. If the tumor originated from other cells in the body, they would be less likely to bind the antibody.

Gut Protection

In the gut, a cytokine [a type of small signalling molecule] called IL-22 can have either an inflammatory or protective effect. This study reveals the molecular mechanisms underlying maintenance of a mucus layer and cell regeneration conferring a protective effect by IL-22 in a mouse colitis model and in human tissue

Read the published research article here

Image from work by Ankita Singh and colleagues

Department of Microbiology and Immunology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Cell Reports, May 2024