Antigenic markers and laminin expression in cultured enteric neural cells

A combinatorial panel for flow cytometry-based isolation of enteric nervous system cells from human intestine

Efficient isolation of neurons and glia from the human enteric nervous system (ENS) is challenging because of their rare and fragile nature. Here, we describe a staining panel to enrich ENS cells from the human intestine by fluorescence-activated cell sorting (FACS). We find that CD56/CD90/CD24 co-expression labels ENS cells with higher specificity and resolution than previous methods. Surprisingly, neuronal (CD24, TUBB3) and glial (SOX10) selective markers appear co-expressed by all ENS cells. We demonstrate that this contradictory staining pattern is mainly driven by neuronal fragments, either free or attached to glial cells, which are the most abundant cell types. Live neurons can be enriched by the highest CD24 and CD90 levels. By applying our protocol to isolate ENS cells for single-cell RNA sequencing, we show that these cells can be obtained with high quality, enabling interrogation of the human ENS transcriptome. Taken together, we present a selective FACS protocol that allows enrichment and discrimination of human ENS cells, opening up new avenues to study this complex system in health and disease.

Isolation, identification, and culture of normal mouse colonic glia

We have developed a novel method of isolating and culturing murine colonic mucosal glial cells. Two morphologies are appreciated, a small flat bi or tri polar cell and a larger multipolar cell. The glial cultures have been freed of contaminating fibroblasts and epithelial cells and have been passaged by trypsinization. By intermediate filament (IF) typing, the glial cells have been further characterized as astrocyte-like. All cells expressed glial fibrillary acid protein but not neurofilament 160 protein. The glial cultures expressed the neuropeptides, substance P and substance K. Central nervous system astrocytes synthesize neuropeptides, prostaglandins and cytokines, and can express major histocompatibility class II antigens. It is likely that enteric mucosal glia will also prove to have varied functions. These cultures can now be used to define the role of enteric mucosal glia and to further study their complex interaction with other cells of the colonic mucosa.

Electrophysiologic and molecular properties of cultured enteric glia

Enteric glia, the support cells of myenteric ganglia, have been widely studied with respect to their morphology and immunohistochemical phenotype, but little is known about their functional properties. We developed a method for the amplification of enteric glia from newborn guinea pigs to further characterize these cells. Treatment with a combination of basic fibroblast growth factor and the adenylate cyclase activator, cholera toxin, permitted expansion of enteric glial cultures to confluence and serial passage for up to 8 months. The long-term cultured cells retained expression of 1) S100 protein, 2) GD3 ganglioside recognized by the monoclonal antibody LB1, and 3) the gene encoding glutamine synthetase. The electrophysiologic properties of cultured enteric glia were studied under whole-cell patch clamp conditions. Most cells expressed "delayed rectifier"-type potassium currents, and some also demonstrated tetrodotoxin-sensitive sodium currents. Other subsets of voltage-dependent potassium currents, calcium currents, and glutamate-gated currents were not demonstrable.

The olfactory nerve contains two populations of glia, identified both in vivo and in vitro

The peripheral olfactory nervous system exhibits, uniquely, neuronal cell body replacement and reestablishment of central connections in adult mammals. The role of the olfactory nerve glia in these phenomena is unknown, but information might be provided by in vitro systems. This paper reports on the characterization of olfactory nerve glia in dissociated cell cultures of newborn rat nasal mucosal tissues. The predominant type of glial cell resembled Schwann cells and immunostained for the S-100 protein, found in all glial cell types; glial fibrillary acidic protein (GFAP), found in astrocytes and nonmyelinating Schwann cells; and showed binding of 217C, a monoclonal Schwann-cell marker that binds to the low-affinity NGF receptor in glioma cells. They were negative for A2B5. The Schwann-cell-like olfactory glia changed morphology upon culturing in serum-free medium, with further shape changes after plating on laminin. Plating on laminin increased cell numbers. A second population, found only after GFAP-immunostaining, was astrocyte-like in morphology and represented approximately 10 percent of all glial cells. These were S-100-, A2B5-, and 217C-negative, a unique glial cell immunological profile. At low dilutions of anti-GFAP (1/10,000), or with weak fluorescent secondary antibodies, astrocyte-like glia were immunostained but Schwann-cell-like glia were not detectable. Astrocyte-like glia were not an artifact of the dissection, since they were detectable in tissue sections of newborn-rat olfactory nerves immunostained with a low dilution of anti-GFAP. The presence of two types of glial cells in culture suggests similarities between olfactory glia and enteric glia.

Transplantation of postnatal rat enteric ganglia into denervated adult rat hippocampus

These experiments explore the possible value of the myenteric plexus as a source of donor cells for autografting into the central nervous system. Neurons and glia from 10-12-day postnatal rat myenteric plexus survive for at least one month after transplantation into cholinergically denervated syngeneic adult rat hippocampus. A population of donor cholinergic neurons has acetylcholinesterase-positive processes, but these appear not to innervate host tissue. Host gliosis in response to these implants seems to be less than that seen with other peripheral ganglia, and unlike Schwann cells, the enteric glia form end-feet on brain capillaries.

Anti-ganglioside antibodies reveal subsets of cultured rat dorsal root ganglion neurons

Subsets of cultured dorsal root ganglion neurons were identified by using the anti-ganglioside monoclonal antibodies A2B5, D1.1, R24 and JONES. A2B5 and D1.1 labelled a population of cells that was relatively stable between 2 and 20 days in vitro, while the population of cells labeled with both R24 and JONES decreased with time, suggesting that the gangliosides recognized by Jones and R24 are developmentally regulated. Given the observation that the relative proportions of ganglioside species changes with time in culture, it is very important to carefully define the stability of ganglioside antigens before using them as cell markers.

Transforming growth factor-beta and gamma-interferon have dual effects on growth of peripheral glia

The influence of transforming growth factor-beta (TGF-beta) and gamma-interferon on DNA synthesis in Schwann cells and enteric glia in culture has been studied. TGF-beta stimulated the DNA synthesis of short-term (less than 2 weeks in culture) Schwann cells, whereas gamma-interferon was ineffective. The stimulatory effect of TGF-beta was additive to the stimulation of DNA synthesis due to axonal membrane fragments. In contrast to their effect on short-term Schwann cells, both TGF-beta and gamma-interferon inhibited DNA synthesis in enteric glial cells and in long-term (over 3 months in culture) Schwann cells. When short-term Schwann cells were stimulated to divide by axolemma or glial growth factor, gamma-interferon did not inhibit this enhanced DNA synthesis although it suppressed DNA synthesis induced by cAMP analogues. These results raise the possibility that TGF-beta and gamma-interferon might have a role in controlling glial proliferation during development and/or regeneration of the peripheral nervous system.

Type I collagen preparations inhibit DNA synthesis in glial cells of the peripheral nervous system

The mechanisms underlying cessation of glial proliferation in the developing peripheral nervous system are obscure. One possibility, as yet little explored, is that mitotic inhibitory signals play a part in regulating glial cell numbers. In this study we demonstrate that type I collagen preparations from several different sources can inhibit the rate of DNA synthesis in purified populations of enteric glia and both short-term and long-term secondary Schwann cells in dissociated cell cultures. When these cells are grown on gelled or dried type I collagen substrata, they proliferate at substantially lower rates than on polylysine substrata. In contrast, type III or V collagen preparations do not inhibit glial DNA synthesis and laminin, fibronectin, type IV collagen, and secreted matrix from bovine corneal endothelial cells all stimulate thymidine incorporation. The inhibitory effect is not observed with heat denatured type I collagen preparations, but is seen equally in serum-containing medium, in medium containing fibronectin-free serum, or in serum-free medium, suggesting that the interaction of collagen with the cells requires structurally intact collagen molecules and does not occur via intermediary linkage to fibronectin. The inhibition on collagen is accompanied by a shape change from a more flattened morphology to a narrow spindle form. The labeling index of a rat Schwannoma cell line, 33B, is not inhibited on type I collagen substrata. These results demonstrate that type I collagen preparations inhibit the DNA synthesis levels of early postnatal peripheral glial cells in vitro. It remains to be determined whether this effect occurs via direct collagen-cell membrane interactions or whether it depends on accessory molecules, perhaps present in the collagen preparations themselves, since these are not purified to absolute homogeneity.

Establishment and properties of separate cultures of enteric neurons and enteric glia

In this paper methods are described for the preparation of two types of culture derived from myenteric explants: (a) highly enriched neuronal cell cultures, and (b) purified glial cells (greater than 98%). Both procedures combine the technique of antibody complement-mediated cytolysis with the use of an antimitotic agent. Immunohistochemical methods were used to compare the purified cells to their counterparts in mixed cultures (see accompanying paper). Antibodies to the glycoprotein Thy-1 and the monoclonal antibody A2B5 which recognizes gangliosides, labelled the cell surface of all enteric neurons in enriched cultures while subpopulations of the neurons expressed the Leu 7 carbohydrate epitope, the neurotransmitter 5-hydroxytryptamine and the neuropeptides substance P, methionine-enkephalin and vasoactive intestinal polypeptide. Autoradiographic experiments show that a subpopulation of enriched neurons exhibit high-affinity uptake sites for gamma-[3H]aminobutyric acid (GABA). All purified enteric glia continue to express the calcium binding protein S100, the basement membrane glycoprotein laminin and the antigens recognized by the A2B5 antibody, and subpopulations of glia are labelled by the monoclonal antibodies LB1 which binds to GD3 gangliosides, and Leu 7. Thus enteric neurons and glia can survive independently of each other and express molecular properties which are present in cultures normally containing both cell types.