Chondroitin Sulfate Expression in Perineuronal Nets After Goldfish Spinal Cord Lesion.

Akihito Takeda,Masashige Shuto,Kengo Funakoshi

doi:10.3389/fncel.2018.00063

Akihito Takeda, Masashige Shuto + Show 1 more

Open Access

https://doi.org/10.3389/fncel.2018.00063

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Abstract

Perineuronal nets (PNNs) surrounding neuronal cell bodies regulate neuronal plasticity during development, but their roles in regeneration are unclear. In the PNNs, chondroitin sulfate (CS) is assumed to be involved in inhibiting contact formation. Here, we examined CS expression in PNNs in the ventral horn of a goldfish hemisected spinal cord in which descending axons regenerate beyond the lesion to connect with distal spinal neurons. In intact fish, chondroitin sulfate A (CS-A)–positive PNNs accounted for 5.0% of HuC/D-immunoreactive neurons, and 48% of choline acetyltransferase (ChAT)-immunoreactive neurons. At 2, 4 and 8 weeks after spinal hemisection, CS-A–positive PNNs accounted for 8.4%–9.9% of HuC/D-immunoreactive neurons, and 50%–60% of ChAT-immunoreactive neurons, which was not significantly different from intact fish. Chondroitin sulfate C (CS-C)–positive PNNs accounted for 6.4% of HuC/D-immunoreactive neuron, and 67% of ChAT-immunoreactive neurons in intact fish. At 2, 4 and 8 weeks after spinal hemisection, CS-C–positive PNNs accounted for 7.9%, 5.5% and 4.3%, respectively, of HuC/D-immunoreactive neurons, and 65%, 52% and 42%, respectively, of ChAT-immunoreactive neurons, demonstrating a significant decrease at 4 and 8 weeks after spinal hemisection. Among ventral horn neurons that received descending axons labeled with tetramethylrhodamine dextran amine (RDA) applied at the level of the first spinal nerve, CS-A–positive PNNs accounted for 53% of HuC/D-immunoreactive neurons. At 2 and 4 weeks after spinal hemisection, CS-A–positive PNNs accounted for 57% and 56% of HuC/D-immunoreactive neurons, which was not significantly different from intact fish. CS-C–positive PNNs, accounted for 48% of HuC/D-immunoreactive neurons that received RDA-labeled axons. At 2 and 4 weeks after spinal hemisection, CS-C–positive PNNs significantly decreased to 22% of the HuC/D-immunoreactive neurons, and by 4 weeks after spinal hemisection they had returned to 47%. These findings suggest that CS expression is maintained in the PNNs after spinal cord lesion, and that the descending axons regenerate to preferentially terminate on neurons not covered with CS-C–positive PNNs. Therefore, CS-C in the PNNs possibly inhibits new contact with descending axons, and plasticity in the spinal neurons might be endowed by downregulation of CS-C in the PNNs in the regeneration process after spinal hemisection in goldfish.

Highlights

Perineuronal nets (PNNs) are reticular structures that surround the cell bodies and proximal dendrites of various neurons in the central nervous system
In the intact spinal cord, many chondroitin sulfate (CS)-A–positive PNNs were present around HuC/D-immunoreactive neurons in the ventral horn
Most of the chondroitin sulfate A (CS-A)–positive PNNs were observed around large neurons, but some were observed around small neurons (Figure 2A)

Summary

INTRODUCTION

Perineuronal nets (PNNs) are reticular structures that surround the cell bodies and proximal dendrites of various neurons in the central nervous system. There is a significant increase in some types of CSPGs in the extracellular matrix surrounding the lesion site and a decrease in other types (Jones et al, 2003; Tang et al, 2003). Removal of PNNs by the application of ChABC is a potential therapeutic strategy to enhance neuronal plasticity and promote reorganization of connections in the spinal cord (Galtrey et al, 2007), but the expression of CSPGs in PNNs after injury has not been investigated in sufficient detail to confirm this notion. We used immunohistochemistry with specific monoclonal antibodies to examine two CS variants with different sulfation patterns, CS-A and CS-C Both CS-A and CS-C negatively affect axonal growth in mammals (Wang et al, 2008; Swarup et al, 2013). To evaluate whether CS-A and CS-C are co-expressed in the same PNN, we performed multiple labeling studies with tenascin-R, a pan-marker for CSPG, and CS-A or CS-C in the PNNs of intact fish

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DISCUSSION