Fourier transform infrared imaging Nutrient transport Nucleus pulposus cell Low back pain s u m m a r y Objective: Intradiscal biologic therapy is a promising strategy for managing intervertebral disc degeneration. However, these therapies require a rich nutrient supply, which may be limited by the transport properties of the cartilage endplate (CEP). This study investigated how fluctuations in CEP transport properties impact nutrient diffusion and disc cell survival and function. Design: Human CEP tissues harvested from six fresh cadaveric lumbar spines (38e66 years old) were placed at the open sides of diffusion chambers. Bovine nucleus pulposus (NP) cells cultured inside the chambers were nourished exclusively by nutrients diffusing through the CEP tissues. After 72 h in culture, depth-dependent NP cell viability and gene expression were measured, and related to CEP transport properties and biochemical composition determined using fluorescence recovery after photobleaching and Fourier transform infrared (FTIR) spectroscopy. Results: Solute diffusivity varied nearly 4-fold amongst the CEPs studied, and chambers with the least permeable CEPs appeared to have lower aggrecan, collagen-2, and matrix metalloproteinase-2 gene expression, as well as a significantly shorter viable distance from the CEP/nutrient interface. Increasing chamber cell density shortened the viable distance; however, this effect was lost for low-diffusivity CEPs, which suggests that these CEPs may not provide enough nutrient diffusion to satisfy cell demands. Solute diffusivity in the CEP was associated with biochemical composition: low-diffusivity CEPs had greater amounts of collagen and aggrecan, more mineral, and lower cross-link maturity. Conclusions: CEP transport properties dramatically affect NP cell survival/function. Degeneration-related CEP matrix changes could hinder the success of biologic therapies that require increased nutrient supply.

Yu S, Ouyang A. TRPA1 in bradykinin-induced mechanical hypersensitivity of vagal C fibers in guinea pig esophagus. Am J Physiol Gastrointest Liver Physiol 296: G255-G265, 2009. First published November 25, 2008 doi:10.1152/ajpgi.90530.2008 activates sensory nerves and causes hyperalgesia. Transient receptor potential A1 (TRPA1) is expressed in sensory nerves and mediates cold, mechanical, and chemical nociception. TRPA1 can be activated by BK. TRPA1 knockout mice show impaired responses to BK and mechanical nociception. However, direct evidence from sensory nerve terminals is lacking. This study aims to determine the role of TRPA1 in BK-induced visceral mechanical hypersensitivity. Extracellular recordings of action potentials from vagal nodose and jugular neurons are performed in an ex vivo guinea pig esophagealvagal preparation. Peak frequencies of action potentials of afferent nerves evoked by esophageal distension and chemical perfusion are recorded and compared. BK activates most nodose and all jugular C fibers. This activation is repeatable and associated with a significant increase in response to esophageal distension, which can be prevented by the B2 receptor antagonist WIN64338. TRPA1 agonist allyl isothiocyanate (AITC) activates most BK-positive nodose and jugular C fibers. This is associated with a transient loss of response to mechanical distensions and desensitization to a second AITC perfusion. Desensitization with AITC and pretreatment with TRPA1 inhibitor HC-030031 both inhibit BK-induced mechanical hypersensitivity but do not affect BK-evoked activation in nodose and jugular C fibers. In contrast, esophageal vagal afferent A␦ fibers do not respond to BK or AITC and fail to show mechanical hypersensitivity after BK perfusion. This provides the first evidence directly from visceral sensory afferent nerve terminals that TRPA1 mediates BK-induced mechanical hypersensitivity. This reveals a novel mechanism of visceral peripheral sensitization. transient receptor potential A1; vagus; nociceptor; visceral hypersensitivity ABNORMAL ESOPHAGEAL SENSATIONS, such as heartburn and esophageal-related noncardiac chest pain, are common complaints (12). They result from noxious stimuli (mechanical, chemical, and thermal stimuli) that are transduced into action potentials by esophageal primary sensory afferents and transmitted to the central nervous system via both spinal and vagal pathways (27,28,31,32,33,40). These esophageal sensations are enhanced after tissue injury or inflammation through mechanisms that involve both peripheral and central sensitization of sensory inputs, resulting in visceral hypersensitivity (22, 13). Peripheral sensitization plays an important role in this process but is less understood.Visceral sensory afferent nerves provide gastrointestinal sensory inputs in both physiological and noxious ranges. Those that sense noxious stimuli are referred to as nociceptors (17, 37). Gastrointestinal primary afferent nociceptive nerves usually are polymodel with their cell bodies situated not only ...

Several esophageal pathologies are associated with an increased number of mast cells in the esophageal wall. We addressed the hypothesis that activation of esophageal mast cells leads to an increase in the excitability of local sensory C fibers. Guinea pigs were actively sensitized to ovalbumin. The mast cells in the esophagus were selectively activated ex vivo by superfusion with ovalbumin. Action potential discharge in guinea pig vagal nodose esophageal C-fiber nerve endings was monitored in the isolated (ex vivo) vagally innervated esophagus by extracellular recordings. Ovalbumin activated esophageal mast cells, leading to the rapid release of approximately 20% of the tissue histamine stores. This was associated with a consistent and significant increase in excitability of the nodose C fibers as reflected in a two- to threefold increase in action potential discharge frequency evoked by mechanical (increases in intraluminal pressure) stimulation. The increase in excitability persisted unchanged for at least 90 min (longest time period tested) after ovalbumin was washed from the tissue. This effect could be prevented by the histamine H1 receptor antagonist pyrilamine, but once the increase in excitability occurred, it persisted in the nominal absence of histamine and could not be reversed even with large concentrations of the histamine receptor antagonist. In conclusion, activation of esophageal mast cells leads to a pronounced and long-lived increase in nociceptive C-fiber excitability such that any sensation or reflex evoked via the vagal nociceptors will likely be enhanced. The effect is initiated by histamine acting via H1 receptor activation and maintained in the absence of the initiating stimulus.

The choice between pneumatic dilatation and surgical esophagomyotomy as the initial treatment for achalasia is controversial. The aims of this study were to determine the long term clinical outcome and costs of treating achalasia initially with pneumatic dilatation as compared to esophagomyotomy. Of 123 patients undergoing an initial pneumatic dilatation for achalasia at our institution from 1976 to 1986, 71 (58%) received no further treatment for achalasia during a mean follow up of 4.7 +/- 2.8 years. Only 15 of these 123 patients (12%) eventually underwent surgical esophagomyotomy (two for perforation during pneumatic dilatation, 13 for persistent or recurrent symptoms). The degree of dysphagia at follow up was improved to a similar degree in patients treated with an initial pneumatic dilatation as compared to patients treated with an initial esophagomyotomy. Patients with age > or = 45 years at time of initial pneumatic dilatation had fewer subsequent treatments for persistent or recurrent symptoms and had less dysphagia on follow up as compared to patients < 45 years. Subsequent pneumatic dilatations to treat persistent or recurrent symptoms were less beneficial than an initial pneumatic dilatation. The cost of esophagomyotomy was 5 times greater than the cost of pneumatic dilatation. When costs were analyzed to include subsequent treatments of symptomatic patients, the total expectant costs of treating with an initial esophagomyotomy remained 2.4 times greater than treating with an initial pneumatic dilatation. This study suggests that an initial pneumatic dilatation will be the only treatment needed for the majority of patients with achalasia. A treatment regimen starting with pneumatic dilatation has less overall costs than starting with esophagomyotomy. For each subsequent pneumatic dilatation, however, the clinical benefit leans toward surgery.

The afferent neurons innervating the oesophagus originate from two embryonic sources: neurons located in vagal nodose ganglia originate from embryonic placodes and neurons located in vagal jugular and spinal dorsal root ganglia (DRG) originate from the neural crest. Here, we address the hypothesis that 5-hydroxytryptamine (5-HT) differentially stimulates afferent nerve subtypes in the oesophagus. Extracellular recordings of single unit activity originating from nerve terminals were made in the isolated innervated guinea-pig oesophagus. Whole cell patch clamp recordings (35 degrees C) were made from the primary afferent neurons retrogradely labelled from the oesophagus. 5-Hydroxytryptamine (10 micromol L(-1)) activated vagal nodose C-fibres (70%) in the oesophagus but failed to activate overtly vagal jugular nerve fibres and oesophagus-specific spinal DRG neurons. The response to 5-HT in nodose C-fibre nerve terminals was mimicked by the selective 5-HT(3) receptor agonist 2-methyl-5-HT (10 micromol L(-1)) and nearly abolished by the 5-HT(3) receptor antagonists ondansetron (10 micromol L(-1)) and Y-25130 (10 micromol L(-1)). In patch clamp studies, 2-methyl-5-HT (10 micromol L(-1)) activated a proportion of isolated oesophagus-specific nodose capsaicin-sensitive neurons (putative cell bodies of nodose C-fibres). We conclude that the responsiveness to 5-HT discriminates placode-derived (vagal nodose) C-fibres from the neural crest-derived (vagal jugular and spinal DRG) afferent nerves in the oesophagus. The response to 5-HT in nodose C-fibres is mediated by the 5-HT(3) receptor in their neuronal membrane.