Tenascin-R as a regulator of CNS glial cell function

EA Improves the Motor Function in Rats with Spinal Cord Injury by Inhibiting Signal Transduction of Semaphorin3A and Upregulating of the Peripheral Nerve Networks

Peripheral nerve networks (PNNs) play a vital role in the neural recovery after spinal cord injury (SCI). Electroacupuncture (EA), as an alternative medicine, has been widely used in SCI and was proven to be effective on neural functional recovery. In this study, the interaction between PNNs and semaphrin3A (Sema3A) in the recovery of the motor function after SCI was observed, and the effect of EA on them was evaluated. After the establishment of the SCI animal model, we found that motor neurons in the ventral horn of the injured spinal cord segment decreased, Nissl bodies were blurry, and PNNs and Sema3A as well as its receptor neuropilin1 (NRP1) aggregated around the central tube of the gray matter of the spinal cord. When we knocked down the expression of Sema3A at the damage site, NRP1 also downregulated, importantly, PNNs concentration decreased, and tenascin-R (TN-R) and aggrecan were also reduced, while the Basso-Beattie-Bresnahan (BBB) motor function score dramatically increased. In addition, when conducting EA stimulation on Jiaji (EX-B2) acupoints, the highly upregulated Sema3A and NRP1 were reversed post-SCI, which can lessen the accumulation of PNNs around the central tube of the spinal cord gray matter, and simultaneously promote the recovery of motor function in rats. These results suggest that EA may further affect the plasticity of PNNs by regulating the Sema3A signal and promoting the recovery of the motor function post-SCI.

Passive immunization with tenascin-R (TN-R) polyclonal antibody promotes axonal regeneration and functional recovery after spinal cord injury in rats

Tenascin-R (TN-R) is a neural specific protein and an important molecule involved in inhibition of axonal regeneration after spinal cord injury (SCI). Here we report on rabbit-derived TN-R polyclonal antibody, which acts as a TN-R antagonist with high titer and high specificity, promoted neurite outgrowth and sprouting of rat cortical neurons cultured on the inhibitory TN-R substrate in vitro. When locally administered into the lesion sites of rats received spinal cord dorsal hemisection, these TN-R antibodies could significantly decrease RhoA activation and improve functional recovery from corticospinal tract (CST) transection. Thus, passive immunotherapy with specific TN-R antagonist may represent a promising repair strategy following acute SCI.

Functional delay of myelination of auditory delay lines in the nucleus laminaris of the barn owl

In the barn owl, maps of interaural time difference (ITD) are created in the nucleus laminaris (NL) by interdigitating axons that act as delay lines. Adult delay line axons are myelinated, and this myelination is timely, coinciding with the attainment of adult head size, and stable ITD cues. The proximal portions of the axons become myelinated in late embryonic life, but the delay line portions of the axon in NL remain unmyelinated until the first postnatal week. Myelination of the delay lines peaks at the third week posthatch, and myelinating oligodendrocyte density approaches adult levels by one month, when the head reaches its adult width. Migration of oligodendrocyte progenitors into NL and the subsequent onset of myelination may be restricted by a glial barrier in late embryonic stages and the first posthatch week, since the loss of tenascin-C immunoreactivity in NL is correlated with oligodendrocyte progenitor migration into NL.

Early coevolution of adhesive but not antiadhesive tenascin-R ligand-receptor pairs in vertebrates: A phylogenetic study

Axon growth inhibitory CNS matrix proteins, such as tenascin-R (TN-R), have been supposed to contribute to the poor regenerative capacity of adult mammalian CNS. With regard to TN-R function in low vertebrates capable of CNS regeneration, questions of particular interest concern the (co)evolution of ligand-receptor pairs and cellular response mechanisms associated with axon growth inhibition and oligodendrocyte differentiation. We address here these questions in a series of comparative in vivo and in vitro analyses using TN-R proteins purified from different vertebrates (from fish to human). Our studies provide strong evidence that unlike TN-R of higher vertebrates, fish TN-R proteins are not repellent for fish and less repellent for mammalian neurons and do not interfere with F3/contactin- and fibronectin-mediated mammalian cell adhesion and axon growth. However, axonal repulsion is induced in fish neurons by mammalian TN-R proteins, suggesting that the intracellular inhibitory machinery induced by TN-R-F3 interactions is already present during early vertebrate evolution. In contrast to TN-R-F3, TN-R-sulfatide interactions, mediating oligodendrocyte adhesion and differentiation, are highly conserved during vertebrate evolution. Our findings thus indicate the necessity of being cautious about extrapolations of the function of ligand-receptor pairs beyond a species border and, therefore, about the phylogenetic conservation of a molecular function at the cellular/tissue level.

Expression of KAI1 and tenascin, and microvessel density are closely correlated with liver metastasis of gastrointestinal adenocarcinoma

AIM

To seek good markers to predict invasion and metastasis of gastrointestinal adenocarcinoma (GIA).

METHODS

Expression of KAI1 and tenascin were examined on tissue microarrays containing gastric adenocarcinoma (n = 98), colorectal adenocarcinoma (n = 125), gastric adjacent non-cancerous mucosa (n = 95) and colorectal adjacent non-cancerous mucosa (n = 112) by immunostaining. Microvessel density (MVD) in GIA was labelled using anti-CD34 antibody by immunostaining. Expression of KAI1 and tenascin, and MVD were compared with clinicopathological features of tumours, including PTEN (phosphatase and tensin homology deleted from human chromosome 10) and EMMPRIN (extracellular matrix metalloproteinase inducer) expression.

RESULTS

KAI1 expression was higher in GIAs than in their adjacent non-cancerous mucosa (p<0.05). KAI1 and tenascin expression showed a significantly negative association with liver metastasis of GIA (p<0.05), but not with depth of invasion, venous invasion or lymph node metastasis (p>0.05). A significantly negative relationship was observed between EMMPRIN and tenascin expression in GIA (p<0.05). MVD was positively correlated with depth of invasion, venous invasion, lymph node metastasis and liver metastasis of tumours (p<0.05), whereas it was negatively correlated with PTEN expression (p<0.05).

CONCLUSIONS

Up-regulated KAI1 expression may play an important part in malignant transformation of gastrointestinal epithelial cells. Reduced expression of KAI1 and tenascin might underlie the molecular basis of liver metastasis of GIA. Angiogenesis is a key event in the invasion and metastasis of GIA. These markers might be used to indicate liver metastasis of GIA in clinicopathological practice.

Radial migration of developing microglial cells in quail retina: A confocal microscopy study

Microglial cells spread within the nervous system by tangential and radial migration. The cellular mechanism of tangential migration of microglia has been described in the quail retina but the mechanism of their radial migration has not been studied. In this work, we clarify some aspects of this mechanism by analyzing morphological features of microglial cells at different steps of their radial migration in the quail retina. Microglial cells migrate in the vitreal half of the retina by successive jumps from the vitreal border to progressively more scleral levels located at the vitreal border, intermediate regions, and scleral border of the inner plexiform layer (IPL). The cellular mechanism used for each jump consists of the emission of a leading thin radial process that ramifies at a more scleral level before retraction of the rear of the cell. Hence, radial migration and ramification of microglial cells are simultaneous events. Once at the scleral border of the IPL, microglial cells migrate through the inner nuclear layer to the outer plexiform layer by another mechanism: they retract cell processes, become round, and squeeze through neuronal bodies. Microglial cells use radial processes of s-laminin-expressing Müller cells as substratum for radial migration. Levels where microglial cells stop and ramify at each jump are always interfaces between retinal strata with strong tenascin immunostaining and strata showing weak or no tenascin immunoreactivity. When microglial cell radial migration ends, tenascin immunostaining is no longer present in the retina. These findings suggest that tenascin plays a role in the stopping and ramification of radially migrating microglial cells.

Tenascins: regulation and putative functions during pathological stress

In this review, we discuss the structure and function of the extracellular matrix protein family of tenascins with emphasis on their involvement in human pathologies. The article is divided into the following sections:

INTRODUCTION

the tenascin family of extracellular matrix proteins; Structural roles: tenascin-X deficiency and Ehlers-Danlos syndrome; Tenascins as modulators of cell adhesion, migration, and growth; Role of tenascin-C in inflammation; Regulation of tenascins by mechanical stress: implications for wound healing and regeneration; Association of tenascin-C with cancer: antibodies as diagnostic and therapeutic tools; Conclusion and perspectives.