Axolotls with an under- or oversupply of neural crest can regulate the sizes of their dorsal root ganglia to normal levels

The Multiscale Wisdom of the Body: Collective Intelligence as a Tractable Interface for Next-Generation Biomedicine

The dominant paradigm in biomedicine focuses on genetically-specified components of cells and their biochemical dynamics, emphasizing bottom-up emergence of complexity. Here, I explore the biomedical implications of a complementary emerging field: diverse intelligence. Using tools from behavioral science and multiscale neuroscience, we can study development, regenerative repair, and cancer suppression as behaviors of a collective intelligence of cells navigating the spaces of possible morphologies and transcriptional and physiological states. A focus on the competencies of living material-from molecular to organismal scales-reveals a new landscape for interventions. Such top-down approaches take advantage of the memories and homeodynamic goal-seeking behavior of cells and tissues, offering the same massive advantages in biomedicine and bioengineering that reprogrammable hardware has provided information technologies. The bioelectric networks that bind individual cells toward large-scale anatomical goals are an especially tractable interface to organ-level plasticity, and tools to modulate them already exist. This suggests a research program to understand and tame the software of life for therapeutic gain by understanding the many examples of basal cognition that operate throughout living bodies.

Collective intelligence: A unifying concept for integrating biology across scales and substrates

A defining feature of biology is the use of a multiscale architecture, ranging from molecular networks to cells, tissues, organs, whole bodies, and swarms. Crucially however, biology is not only nested structurally, but also functionally: each level is able to solve problems in distinct problem spaces, such as physiological, morphological, and behavioral state space. Percolating adaptive functionality from one level of competent subunits to a higher functional level of organization requires collective dynamics: multiple components must work together to achieve specific outcomes. Here we overview a number of biological examples at different scales which highlight the ability of cellular material to make decisions that implement cooperation toward specific homeodynamic endpoints, and implement collective intelligence by solving problems at the cell, tissue, and whole-organism levels. We explore the hypothesis that collective intelligence is not only the province of groups of animals, and that an important symmetry exists between the behavioral science of swarms and the competencies of cells and other biological systems at different scales. We then briefly outline the implications of this approach, and the possible impact of tools from the field of diverse intelligence for regenerative medicine and synthetic bioengineering.

Embryonic Tissue and Blastema Transplantations

Embryo grafts have been an experimental pillar in developmental biology, and particularly, in amphibian biology. Grafts have been essential in constructing fate maps of different cell populations and migratory patterns. Likewise, autografts and allografts in older larvae or adult salamanders have been widely used to disentangle mechanisms of regeneration. The combination of transgenesis and grafting has widened even more the application of this technique.In this chapter, we provide a detailed protocol for embryo transplants in the axolotl (Ambystoma mexicanum ). The location and stages to label connective tissue, muscle, or blood vessels in the limb and blood cells in the whole animal. However, the potential of embryo transplants is enormous and impossible to cover in one chapter. Furthermore, we provide a protocol for blastema transplantation as an example of allograft in older larvae.

An integrated cell isolation and purification method for rat dorsal root ganglion neurons

Objective

Neurobiology studies are increasingly focused on the dorsal root ganglion (DRG), which plays an important role in neuropathic pain. Existing DRG neuron primary culture methods have considerable limitations, including challenging cell isolation and poor cell yield, which cause difficulty in signaling pathway studies. The present study aimed to establish an integrated primary culture method for DRG neurons.

Methods

DRGs were obtained from fetal rats by microdissection, and then dissociated with trypsin. The dissociated neurons were treated with 5-fluorouracil to promote growth of neurons from the isolated cells. Then, reverse transcription polymerase chain reaction and immunofluorescence assays were used to identify and purify DRG neurons.

Results

Isolated DRGs were successfully dissociated and showed robust growth as individual DRG neurons in neurobasal medium. Both mRNA and protein assays confirmed that DRG neurons expressed neurofilament-200 and neuron-specific enolase.

Conclusions

Highly purified, stable DRG neurons could be easily harvested and grown for extended periods by using this integrated cell isolation and purification method, which may help to elucidate the mechanisms underlying neuropathic pain.

MARCKS-like protein is an initiating molecule in axolotl appendage regeneration

Identifying key molecules that launch regeneration has been a long-sought goal. Multiple regenerative animals show an initial wound-associated proliferative response that transits into sustained proliferation if a considerable portion of the body part has been removed. In the axolotl, appendage amputation initiates a round of wound-associated cell cycle induction followed by continued proliferation that is dependent on nerve-derived signals. A wound-associated molecule that triggers the initial proliferative response to launch regeneration has remained obscure. Here, using an expression cloning strategy followed by in vivo gain- and loss-of-function assays, we identified axolotl MARCKS-like protein (MLP) as an extracellularly released factor that induces the initial cell cycle response during axolotl appendage regeneration. The identification of a regeneration-initiating molecule opens the possibility of understanding how to elicit regeneration in other animals.

Why are enteric ganglia so small? Role of differential adhesion of enteric neurons and enteric neural crest cells

The avian enteric nervous system (ENS) consists of a vast number of unusually small ganglia compared to other peripheral ganglia. Each ENS ganglion at mid-gestation has a core of neurons and a shell of mesenchymal precursor/glia-like enteric neural crest (ENC) cells. To study ENS cell ganglionation we isolated midgut ENS cells by HNK-1 fluorescence-activated cell sorting (FACS) from E5 and E8 quail embryos, and from E9 chick embryos. We performed cell-cell aggregation assays which revealed a developmentally regulated functional increase in ENS cell adhesive function, requiring both Ca ²⁺ -dependent and independent adhesion. This was consistent with N-cadherin and NCAM labelling. Neurons sorted to the core of aggregates, surrounded by outer ENC cells, showing that neurons had higher adhesion than ENC cells. The outer surface of aggregates became relatively non-adhesive, correlating with low levels of NCAM and N-cadherin on this surface of the outer non-neuronal ENC cells. Aggregation assays showed that ENS cells FACS selected for NCAM-high and enriched for enteric neurons formed larger and more coherent aggregates than unsorted ENS cells. In contrast, ENS cells of the NCAM-low FACS fraction formed small, disorganised aggregates.  This suggests a novel mechanism for control of ENS ganglion morphogenesis where i) differential adhesion of ENS neurons and ENC cells controls the core/shell ganglionic structure and ii) the ratio of neurons to ENC cells dictates the equilibrium ganglion size by generation of an outer non-adhesive surface.