Regeneration: From cells to tissues to organisms

Multicolor 3D Confocal Imaging of Thick Tissue Sections

In multicellular organisms, most physiological and pathological processes involve an interplay between various cells and molecules that act both locally and systemically. To understand how these complex and dynamic processes occur in time and space, imaging techniques are key. Advances in tissue processing techniques and microscopy now allow us to probe these processes at a large scale and at the same time at a level of detail previously unachievable. Indeed, it is now possible to reliably quantify multiple protein expression levels at single-cell resolution in whole organs using three-dimensional fluorescence imaging techniques. Here we describe a method to prepare adult mouse bone tissue for multiplexed confocal imaging of thick tissue sections. Up to eight different fluorophores can be multiplexed using this technique and spectrally resolved using standard confocal microscopy. The optical clearing method described allows detection of these fluorophores up to a depth of >700 μm in the far-red. Although the method was initially developed for bone tissue imaging, we have successfully applied it to several other tissue types.

The Tentacular Spectacular: Evolution of Regeneration in Sea Anemones

Sea anemones vary immensely in life history strategies, environmental niches and their ability to regenerate. While the sea anemone Nematostella vectensis is the starlet of many key regeneration studies, recent work is emerging on the diverse regeneration strategies employed by other sea anemones. This manuscript will explore current molecular mechanisms of regeneration employed by non-model sea anemones Exaiptasia diaphana (an emerging model species for coral symbiosis studies) and Calliactis polypus (a less well-studied species) and examine how these species compare to the model sea anemone N. vectensis. We summarize the field of regeneration within sea anemones, within the greater context of phylum Cnidaria and in other invertebrate models of regeneration. We also address the current knowledge on two key systems that may be implemented in regeneration: the innate immune system and developmental pathways, including future aspects of work and current limitations.

Identification of proteins that mediate the role of androgens in antler regeneration using label free proteomics in sika deer (Cervus nippon)

Deer antlers offer a unique model to study organ regeneration in mammals. Antler regeneration relies on the pedicle periosteum (PP) cells and is triggered by a decrease in circulating testosterone (T). The molecular mechanism for antler regeneration is however, unclear. Label-free liquid chromatography-mass spectrometry (LC-MS/MS) was used to identify differentially-expressed proteins (DEPs) in the regeneration-potentiated PP (under low T environment) over the non-regeneration-potentiated PP (under high T environment). Out of total 273 DEPs, 189 were significantly up-regulated and 84 were down-regulated from these comparisons: after castration vs before castration, natural T vs before castration, and exogenous T vs before castration. We focused on the analysis only of those DEPs that were present in fully permissive environment to antler regeneration (low T). Nine transduction pathways were identified through the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, including the estrogen signaling pathway. A total of 639 gene ontology terms were found to be significantly enriched in regeneration-potentiated PP (low T) from the DEPs. Reliability of the label free LC-MS/MS was determined by qRT-PCR to estimate the expression level of selected genes. The results suggest that up-regulated heat shock proteins (HSP90AB1, HSP90B1), peptidyl-prolyl cis-trans isomerase 4 (FKBP4), mitogen-activated protein kinase 3 (MAPK3) and calreticulin (CALR) and down-regulated SHC-transforming protein 1 (SHC1), heat shock protein family A member 1A (HSPA1A) and proto-oncogene tyrosine-protein kinase (SRC) may be associated directly or indirectly with antler regeneration. Further studies are required to investigate the roles of these proteins in regeneration using appropriate in vivo models.