Innervation Of Teeth Research Articles

The temporospatial relationship between mouse dental pulp stem cells and tooth innervation

Background/purposeDental pulp stem cells (DPSCs) exhibit versatile differentiation capabilities, including neural differentiation, prompting the hypothesis that they may be implicated in the neurodevelopment of teeth. This study aimed to explore the temporospatial dynamics between DPSCs and tooth innervation, employing immunofluorescence staining and fluorescent dye injections to investigate the distribution of DPSCs, neural stem cells (NSCs), nerve growth cones, and sensory nerves in developing mouse tooth germs at various stages. Materials and methodsImmunofluorescence staining targeting CD146, Nestin, and GAP-43, along with the injection of AM1-43 fluorescent dye, were utilized to observe the distribution of DPSCs, NSCs, nerve growth cones, and sensory nerves in mouse tooth germs at different developmental stages. ResultsPositive CD146 immunostaining was observed in microvascular endothelial cells and pericytes within and around the tooth germ. The percentage of CD146-positive cells remained consistent between 4-day-old and 8-day-old second molar tooth germs. Conversely, Nestin expression in odontoblasts and their processes decreased in 8-day-old tooth germs compared to 4-day-old ones. Positive immunostaining for GAP-43 and AM1-43 fluorescence revealed the entry of nerve growth cones and sensory nerves into the pulp in 8-day-old tooth germs, while these elements were confined to the dental follicle in 4-day-old germs. No co-localization of CD146-positive DPSCs with nerve growth cones and sensory nerves was observed. ConclusionDPSCs and NSCs were present in dental pulp tissue before nerves penetrated the pulp. The decline in NSCs after nerve entry suggests a potential role for DPSCs and NSCs in attracting neural growth and/or differentiation within the pulp.

From teeth to pad: tooth loss and development of keratinous structures in sirenians.

Sirenians are a well-known example of morphological adaptation to a shallow-water grazing diet characterized by a modified feeding apparatus and orofacial morphology. Such adaptations were accompanied by an anterior tooth reduction associated with the development of keratinized pads, the evolution of which remains elusive. Among sirenians, the recently extinct Steller's sea cow represents a special case for being completely toothless. Here, we used μ-CT scans of sirenian crania to understand how motor-sensor systems associated with tooth innervation responded to innovations such as keratinized pads and continuous dental replacement. In addition, we surveyed nine genes associated with dental reduction for signatures of loss of function. Our results reveal how patterns of innervation changed with modifications of the dental formula, especially continuous replacement in manatees. Both our morphological and genomic data show that dental development was not completely lost in the edentulous Steller's sea cows. By tracing the phylogenetic history of tooth innervation, we illustrate the role of development in promoting the innervation of keratinized pads, similar to the secondary use of dental canals for innervating neomorphic keratinized structures in other tetrapod groups.

Comparative Evaluation of Passive Tactile Sensibility Associated with Osseointegrated Implants in Various Regions of Partially Edentulous ArchA Prospective Cohort Study

Introduction: The extremely sensitive tactile sensors periodontal mechanoreceptors play a key role in sensory innervation of teeth. The oral kinaesthetic perceptual abilities in the absence of periodontal mechanoreceptive input can be achieved by osseointegrated prosthesis. Aim: To evaluate the passive tactile sensibility associated with osseointegrated dental implant in various regions of the maxillary and mandibular arch. Materials and Methods: A prospective cohort study was performed in SRM Dental College, Chennai, India between August 2013 to February 2015. Fifty patients who had single tooth replacement with functioning implants loaded six months before were included. A compressive force was applied along the long axis of the implant supported prosthesis using a push type force measuring gauge until the subject felt the first sensation of pressure and subsequently it displayed the magnitude of force that provided the tactile sensation. The force measuring gauge used was Model: FG 5000 A form Lutron electronic enterprises co., ltd. The procedure was repeated thrice. The patient was guided to record the force perception on visual analogue scale with continuous force. The visual analogue scale has values 0-4 starting from no sensation, mild, moderate, intense and pain and the average force measured. The values of the force recorded were statistically analysed using the t-test, SPSS Windows version 17.0 was used. The p-value of 0.05 was considered statistically significant. Results: The overall mean value of maxilla was 23.12 N and the standard deviation was ±2.88 N. The overall mean value of mandibular was 22.44 N and the standard deviation of ±2.06 N and there was no significant difference in the threshold for passive tactile perception between maxilla and mandible. Conclusion: The results showed that mandibular anterior teeth had least threshold for force applied than any other region of the mouth and the maxillary posterior had the highest threshold. The anterior region exhibited better passive tactile threshold measure when compared to posterior region.

A Co-Culture Method to Study Neurite Outgrowth in Response to Dental Pulp Paracrine Signals.

Tooth innervation allows teeth to sense pressure, temperature and inflammation, all of which are crucial to the use and maintenance of the tooth organ. Without sensory innervation, daily oral activities would cause irreparable damage. Despite its importance, the roles of innervation in tooth development and maintenance have been largely overlooked. Several studies have demonstrated that DP cells secrete extracellular matrix proteins and paracrine signals to attract and guide TG axons into and throughout the tooth. However, few studies have provided detailed insight into the crosstalk between the DP mesenchyme and neuronal afferents. To address this gap in knowledge, researchers have begun to utilize co-cultures and a variety of techniques to investigate these interactions. Here, we demonstrate the multiple steps involved in co-culturing primary DP cells with TG neurons dispersed on an overlying transwell filter with large diameter pores to allow axonal growth through the pores. Primary DP cells with the gene of interest flanked by loxP sites were utilized to facilitate gene deletion using an Adenovirus-Cre-GFP recombinase system. Using TG neurons from the Thy1-YFP mouse allowed for precise afferent imaging, with expression well above background levels by confocal microscopy. The DP responses can be investigated via protein or RNA collection and analysis, or alternatively, through immunofluorescent staining of DP cells plated on removable glass coverslips. Media can be analyzed using techniques such as proteomic analyses, although this will require albumin depletion due to the presence of fetal bovine serum in the media. This protocol provides a simple method that can be manipulated to study the morphological, genetic, and cytoskeletal responses of TG neurons and DP cells in response to the controlled environment of a co-culture assay.

Ret Signaling Is Required for Tooth Pulp Innervation during Organogenesis

During organogenesis, the timing and patterning of dental pulp innervation require both chemoattractive and chemorepellent cues for precise spatiotemporal regulation. Our understanding of the signaling mechanisms that regulate tooth innervation during development, as well as the basic biology of these sensory neurons, remains rudimentary. In this study, we analyzed the expression and function of glial cell line–derived neurotrophic factor (GDNF) and its receptor tyrosine kinase, Ret, in the regulation of innervation of the mouse tooth pulp by dental pulpal afferent (DPA) neurons of the trigeminal ganglion (TG). Using reporter mouse models, we demonstrate that Ret is highly expressed by a subpopulation of DPA neurons projecting to the tooth pulp at both postnatal day 7 (P7) and in the adult. In the adult tooth, GDNF is highly expressed by many cell types throughout the dental pulp. Using a ubiquitous tamoxifen (TMX)–inducible Cre (UBC-Cre/ERT2) line crossed to Ret conditional knockout mice (Retfx/fx), Ret was deleted immediately prior to tooth innervation, and the neural projections into P7 molars were analyzed. TMX treatment was efficient in ablating >95% of Ret protein. We observed that UBC-Cre/ERT2; Retfx/fx mice had a significant reduction in the total number of neurites present within the pulp at P7, with a significant accumulation of aberrant fibers in the dental follicle and periodontium. In agreement with these findings, inhibition of Ret signaling through in vivo administration of a highly specific pharmacologic inhibitor (1NM-PP1) of Ret also caused a substantial reduction in pulpal innervation. Taken together, these findings indicate that Ret signaling regulates the timing and patterning of tooth innervation by dental primary afferent neurons of the TG during organogenesis and provide a rationale to explore whether alterations in the GDNF-Ret pathway contribute to pathophysiological conditions in the adult dentition.

Establishment of tooth blood supply and innervation is developmentally regulated and takes place through differential patterning processes.

Teeth are richly supported by blood vessels and peripheral nerves. The aim of this study was to describe in detail the developmental time-course and localization of blood vessels during early tooth formation and to compare that to innervation, as well as to address the putative role of vascular endothelial growth factor (VEGF), which is an essential regulator of vasculature development, in this process. The localization of blood vessels and neurites was compared using double immunofluorescence staining on sections at consecutive stages of the embryonic (E) and postnatal (PN) mandibular first molar tooth germ (E11-PN7). Cellular mRNA expression domains of VEGF and its signaling receptor VEGFR2 were studied using sectional radioactive insitu hybridization. Expression of VEGF mRNA and the encoded protein were studied by RT-PCR and western blot analysis, respectively, in the cap and early bell stage tooth germs, respectively. VEGFR2 was immunolocalized on tooth tissue sections. Smooth muscle cells were investigated by anti-alpha smooth muscle actin (αSMA) antibodies. VEGF showed developmentally regulated epithelial and mesenchymal mRNA expression domains including the enamel knot signaling centers that correlated with the growth and navigation of the blood vessels expressing Vegfr2 and VEGFR2 to the dental papilla and enamel organ. Developing blood vessels were present in the jaw mesenchyme including the presumptive dental mesenchyme before the appearance of the epithelial dental placode and dental neurites. Similarly, formation of a blood vessel plexus around the bud stage tooth germ and ingrowth of vessels into dental papilla at E14 preceded ingrowth of neurites. Subsequently, pioneer blood vessels in the dental papilla started to receive smooth muscle coverage at the early embryonic bell stage. Establishment and patterning of the blood vessels and nerves during tooth formation are developmentally regulated, stepwise processes that likely involve differential patterning mechanisms. Development of tooth vascular supply is proposed to be regulated by local, tooth-specific regulation by epithelial-mesenchymal tissue interactions and involving tooth target expressed VEGF signaling. Further investigations on tooth vascular development by local VEGF signaling, as well as how tooth innervation and development of blood vessels are integrated with advancing tooth organ formation by local signaling mechanisms, are warranted.

Evolutionary Tinkering of the Mandibular Canal Linked to Convergent Regression of Teeth in Placental Mammals

Loss or reduction of teeth has occurred independently in all major clades of mammals [1]. This process is associated with specialized diets, such as myrmecophagy and filter feeding [2, 3], and led to an extensive rearrangement of the mandibular anatomy. Themandibular canal enables lower jaw innervation through the passage of the inferior alveolar nerve (IAN) [4, 5]. In order to innervate teeth, the IAN projects ascending branches directly through tooth roots [5, 6], bone trabeculae [6], or bone canaliculi (i.e., dorsal canaliculi) [7]. Here, we used micro-computed tomography (μ-CT) scans of mandibles, from eight myrmecophagous species with reduced dentition and 21 non-myrmecophages, to investigate the evolutionary fate of dental innervation structures following convergent tooth regression in mammals. Our observations provide strong evidence for a link between the presence of tooth loci and the development of dorsal canaliculi. Interestingly, toothless anteaters present dorsal canaliculi and preserve intact tooth innervation, while equally toothless pangolins do not. We show that the internal mandibular morphology of anteaters has a closer resemblance to that of baleen whales [7] than to pangolins. This is despite masticatory apparatus resemblances that have made anteaters and pangolins a textbook example of convergent evolution. Our results suggest that early tooth loci innervation [8] is required for maintaining the dorsal innervation of the mandible and underlines the dorsal canaliculi sensorial role inthe context of mediolateral mandibular movements. This study presents a unique example of convergent redeployment of the tooth developmental pathway toa strictly sensorial function following tooth regression in anteaters and baleen whales.

Contribution of capsaicin-sensitive innervation to the continuous eruption of the rat mandibular incisors.

A major component of tooth innervation is made of capsaicin-sensitive primary afferents (CSPA). These fibers play a key role in tooth pain and inflammation; little is known, however, about the role of CSPA in tooth eruption. The aim of this study was to examine the role of the capsaicin-sensitive afferents in the process of eruption of intact rat incisors. CSPA fibers in several rat groups, were subjected to one of the following experimental procedures: systemic chemical ablation, systemic ablation followed by chemical sympathectomy and localized activation. The observed effects on incisor eruption were compared to those made on controls. The total amount of eruption in control/naïve rats, measured over a total period of 144h, was 3.18 ± 0.07mm and decreased to 2.43 ± 0.08mm (n = 7; p < 0.001) following systemic ablation of CSPA. Further decrease to 2.24 ± 0.08mm (n = 7; p < 0.001) was noticed when chemical sympathectomy was added to CSPA ablation. The average rate of eruption was 1.7 ± 0.25mm following CSPA activation, compared to an average of 0.8 ± 0.07mm for controls (n = 7; p < 0.001). Capsaicin sensitive fibers play an important role in tooth homeostasis, and intact neural supply is required for tooth growth under normal conditions.

Bone Marrow Stromal Cells Promote Innervation of Bioengineered Teeth

Transplantation of bone marrow mesenchymal stem cells (BMDCs) into a denervated side of the spinal cord was reported to be a useful option for axonal regeneration. The innervation of teeth is essential for their function and protection but does not occur spontaneously after injury. Cultured reassociations between dissociated embryonic dental mesenchymal and epithelial cells and implantation lead to a vascularized tooth organ regeneration. However, when reassociations were coimplanted with a trigeminal ganglion (TG), innervation did not occur. On the other hand, reassociations between mixed embryonic dental mesenchymal cells and bone marrow–derived cells isolated from green fluorescent protein (GFP) transgenic mice (BMDCs-GFP) (50/50) with an intact and competent dental epithelium (ED14) were innervated. In the present study, we verified the stemness of isolated BMDCs, confirmed their potential role in the innervation of bioengineered teeth, and analyzed the mechanisms by which this innervation can occur. For that purpose, reassociations between mixed embryonic dental mesenchymal cells and BMDCs-GFP with an intact and competent dental epithelium were cultured and coimplanted subcutaneously with a TG for 2 wk in ICR mice. Axons entered the dental pulp and reached the odontoblast layer. BMDCs-GFP were detected at the base of the tooth, with some being present in the pulp associated with the axons. Thus, while having a very limited contribution in tooth formation, they promoted the innervation of the bioengineered teeth. Using quantitative reverse transcription polymerase chain reaction and immunostainings, BMDCs were shown to promote innervation by 2 mechanisms: 1) via immunomodulation by reducing the number of T lymphocytes (CD3+, CD25+) in the implants and 2) by expressing neurotrophic factors such as NGF, BDNF, and NT3 for axonal growth. This strategy using autologous mesenchymal cells coming from bone marrow could be used to innervate bioengineered teeth without treatment with an immunosuppressor such as cyclosporine A (CsA), thus avoiding multiple side effects.

Promoting bioengineered tooth innervation using nanostructured and hybrid scaffolds.

Tooth innervation is essential for their function and protection and this can be promoted in vivo using polymeric scaffolds functionalized with immunosuppressive drug-loaded nanoparticles. Immunosuppressive therapy using biodegradable nanoparticles loaded with Cyclosporine A was found to accelerate the innervation of bioengineered teeth after two weeks of implantation.

The anastomotic network around the anterior superior alveolar nerve: an anatomical and radiological study

Innervation of superior teeth is supplied by the posterior (PSAN), anterior (ASAN) and sometimes by middle superior alveolar nerve (MSAN). PSAN arises from the maxillary nerve and passes through the posterolateral maxillary wall towards the posterior teeth. ASAN arises from the anterior portion of the infraorbital nerve and courses within the infraorbital canal passing nearby the piriform aperture and premaxilla. When present, MSAN arises from the posterior portion of the infraorbital nerve and runs along the lateral maxillary wall. However, an additional nasopalatine or sublabial injection is frequently required to obtain a complete anesthesia of the maxillary teeth due to rich anastomotic network (1-2). With the aim to better describe the complexity of the superior alveolar nerve network, fifty-seven high-definition sinonasal cone-beam CT (CBCT) were analyzed. PSAN, ASAN and MSAN were detected by specific bony landmarks/canals and nervous anastomoses were accurately evaluated. In addition, medial anastomotic branches from the palatal and/or nasal nervous plexi were also considered. PSAN and ASAN were identified in 100% of cases whereas MSAN in 19.6% of cases. Anastomotic branch versus ASAN was identified in all cases from MSAN and in 60.3% from PSAN. Medial anastomotic branch was detected in 62.0% of cases from the nasal plexus and in 6.2% from the palatal plexus: the former passed through a bony defect in the floor of the piriform aperture or at the base of the nasal septum; the latter passed through a tiny canal in the interface between maxilla and premaxilla. These data confirm that maxillary teeth innervation, especially for incisor teeth, could be provided not only by alveolar nerves but also from palatal and nasal plexi via small branches running within maxillary bony canals. These results support the need of additional anesthetic injection to obtain adequate anesthesia of the maxillary teeth; moreover, the role of CBCT in the identification of the nervous pattern was underlined.

Mandibular canal, foramina of the mandible and their variations: part II: the clinical relevance of the preoperative radiographic evaluation and report of five cases

AbstractAimsIn part I of the article, a detailed description of the anatomical variations of the mandibular canal and the foramina of the mandible was given. The aim of part II is to discuss the clinical relevance of the anatomical variations.Materials and methodsA literature review was carried out, and five cases of mandibular canal variations are reported.ResultsAnatomical variations of the mandibular canal and foramina of the mandible are reported in bibliography. Bifid and double mandibular canals have been firstly reported in 1973. Since then, the anatomical variations of the mandibular canal have been described by case reports, cadaveric and retrospective radiological studies. It has been proved that the inferior alveolar nerve gives communication fibers to other nerves and extraosseous branches, before entering the mandibular canal, whereas even if it enters the mandible, it branches during its course into the canal. Also, the supplementary innervation of mandibular teeth and periodontal tissues by the long buccal and mylohyoid nerves has been suggested. Several authors also reported the existence of retromolar foramen and supplementary buccal and lingual foramina and their important role either in vascularisation or innervation.ConclusionsThe neurovascular contents of the mandibular canals and foramina gain more importance in oral surgery and implantology because these components are vulnerable to damage during implant placement and sagittal split osteotomy surgery, and complications may occur during the surgery (i.e. unsuspected bleeding, nerve injury). Also, clinicians should be aware of accessory foramina or canals of the mandible in understanding failed inferior alveolar nerve block.

Microfluidics co-culture systems for studying tooth innervation.

Innervation plays a key role in the development and homeostasis of organs and tissues of the orofacial complex. Among these structures, teeth are peculiar organs as they are not innervated until later stages of development. Furthermore, the implication of neurons in tooth initiation, morphogenesis and differentiation is still controversial. Co-cultures constitute a valuable method to investigate and manipulate the interactions of nerve fibers with their target organs in a controlled and isolated environment. Conventional co-cultures between neurons and their target tissues have already been performed, but these cultures do not offer optimal conditions that are closely mimicking the in vivo situation. Indeed, specific cell populations require different culture media in order to preserve their physiological properties. In this study we evaluate the usefulness of a microfluidics system for co-culturing mouse trigeminal ganglia and developing teeth. This device allows the application of specific media for the appropriate development of both neuronal and dental tissues. The results show that mouse trigeminal ganglia and teeth survive for long culture periods in this microfluidics system, and that teeth maintain the attractive or repulsive effect on trigeminal neurites that has been observed in vivo. Neurites are repealed when co-cultured with embryonic tooth germs, while postnatal teeth exert an attractive effect to trigeminal ganglia-derived neurons. In conclusion, microfluidics system devices provide a valuable tool for studying the behavior of neurons during the development of orofacial tissues and organs, faithfully imitating the in vivo situation.

Nanofibers Implant Functionalized by Neural Growth Factor as a Strategy to Innervate a Bioengineered Tooth

Current strategies for jaw reconstruction require multiple procedures, to repair the bone defect, to offer sufficient support, and to place the tooth implant. The entire procedure can be painful and time-consuming, and the desired functional repair can be achieved only when both steps are successful. The ability to engineer combined tooth and bone constructs, which would grow in a coordinated fashion with the surrounding tissues, could potentially improve the clinical outcomes and also reduce patient suffering. A unique nanofibrous and active implant for bone-tooth unit regeneration and also the innervation of this bioengineered tooth are demonstrated. A nanofibrous polycaprolactone membrane is functionalized with neural growth factor, along with dental germ, and tooth innervation follows. Such innervation allows complete functionality and tissue homeostasis of the tooth, such as dentinal sensitivity, odontoblast function, masticatory forces, and blood flow.

Expression patterns of nociceptin in rats following experimental tooth movement

To determine the expression levels of nociceptin following experimental tooth movement. A total of 72 male Sprague-Dawley rats were divided into two groups: sham and experimental groups. For the experimental group, closed coil springs were used to mimic orthodontic force (80 g) between upper incisors and first molars, and the rats were killed at 0 hours, 4 hours, 12 hours, 1 day, 2 days, 5 days, 7 days, 10 days, and 14 days. All of these procedures were similar for the sham group, except for that no force was applied. The four rats killed at 0 hours without any intervention were used as the baseline control in each group. Trigeminal nucleus caudalis from both the ipsilateral and contralateral sides of force applications were obtained for immunostaining. Nociceptin was expressed in both the ipsilateral and contralateral sides of each group. Its expression levels started to increase on day 2, peaked on day 7, and returned to baseline on day 10 in the experimental group, while expression levels started to decrease on day 1 and returned to baseline on day 10 in the sham group. Moreover, the expression levels were similar between the ipsilateral and contralateral sides in each group. The expression levels of nociceptin were elevated following experimental tooth movement. The anesthetic agent used in this study (chloral hydrate) may have an antagonism with nociceptin. Due to bilateral innervation of anterior teeth and bilateral projection of nerve fibers, the expression levels of nociceptin were similar between ipsilateral and contralateral sides.

Transverse cervical nerve: Implications for dental anesthesia

The inferior alveolar nerve block (IANB) has the highest failure incidence of any dental anesthetic technique. Many authors have outlined potential reasons for these failures in permanent lower molars, including accessory innervations from the mylohyoid and mental foramen. However, the potential accessory innervation of posterior mandibular teeth from the transverse cervical nerve (TCN), a branch of ventral rami from the C2-C3 spinal nerves from the cervical plexus (CP), has been difficult to assess as a result of the small size and thickness of the mandibular accessory foramina and nerve branches, as well as due to the dissection technique performed. The goal of this study was to identify and trace the CP branches from fresh human cadaver tissue samples using the Sihler's technique. Two fresh human cadaver samples were used. Samples were fixed in neutralized formalin, macerated in potassium hydroxide, decalcified in acetic acid, stained in Ehrlich's hematoxylin, destained in acetic acid, and cleared in glycerin. Both specimens skin was dissected. The Sihler's technique delineated all nerves three dimensionally and helped to disclose structures of small size and thickness. The TCN from the CP, stained in blue, innervated the posterior mandible in one of the two samples. These results confirmed that the CP may supply accessory innervation to the inferior border of the posterior mandible through the TCN. These findings illustrate variations of anatomy that may account for IANB failures in posterior mandibular teeth and allows for clinical decisions for implementing supplemental anesthetic techniques.

Semaphorin 3A controls timing and patterning of the dental pulp innervation

Timing and patterning of dental pulp innervation are strictly spatio-temporally regulated but it is still not known how they are controlled at molecular level. We analyzed postnatal innervation of the dental pulp in the mandibular first molar of mice deficient for Semaphorin 3A (Sema3A) axon repellant molecule. Immunohistochemical localization of nerve fibers on serial sections covering the whole tooth germs using anti-peripherin antibody revealed that nerve fibers were prematurely present within the preodontoblast layer next to the inner enamel epithelium already at PN0 in Sema3A−/− mice. In contrast, in the wild-type (Sema3A+/+) mice nerve fibers were seen in the pulp only after enamel formation at PN3. The nerves in Sema3A−/− pulp were notably defasciculated and thinner compared to that of Sema3A+/+ mice. A premature formation of an abnormal, enlarged nerve plexus with a high number of arborizations was apparent in the pulp–dentin border target area in Sema3A−/− already at PN2 whereas in the wild-type mice the first sign of plexus formation was seen at PN7. The expression of mRNAs for Ngf, Gdnf and Ncam neuroregulatory molecules in mandibular molar as well as receptors for neurotrophic factors and class 3 semaphorins including Sema3A (TrkA, p75, TrkB, TrkC, Ret, Npn1, Npn2, PlxA4) in trigeminal ganglia were not altered in the Sema3A−/− mice. Collectively, this data show that Sema3A serves an essential role in molar tooth pulp innervation controlling the timing of nerve fiber penetration into the pulp, their patterning and the formation of nerve plexus at pulp–dentin border area, and provide further support for the hypothesis that tooth innervation is regulated by the coordinated activity of locally expressed neuroregulatory molecules exerting positive and negative influences on growing dental nerve fibers.

Expression patterns of Sema3F, PlexinA4, -A3, Neuropilin1 and -2 in the postnatal mouse molar suggest roles in tooth innervation and organogenesis

Objective. Semaphorins form a family of axon wiring molecules but still little is known about their role in tooth formation. A class 3 semaphorin, Semaphorin3F (Sema3F), besides acting as a chemorepellant for different types of axons, controls a variety of non-neuronal developmental processes. Materials and methods. Cellular mRNA expression patterns of Sema3F as well as neuropilin 1 (Npn1), neuropilin 2 (Npn2), plexinA3 and plexinA4 receptors were analyzed by sectional in situ hybridization in the mouse molar tooth during postnatal days 0–7. The expression of the receptors was studied in PN5 trigeminal ganglia. Results. Sema3F, Npn1, -2 and plexinA4 exhibited distinct, spatiotemporally changing expression patterns, whereas plexinA3 was not observed in the tooth germs. Besides being expressed in the base of the dental mesenchyme Sema3F, like plexinA4, Npn1 and -2, was present in the ameloblast cell lineage. Npn1 and Npn2 were additionally seen in the pulp horns and endothelial cells and like PlexinA4 in the developing alveolar bone. Npn1, plexinA3 and -A4 were observed in trigeminal ganglion neurons. Conclusions. Sema3F may act as a tooth target-derived axonal chemorepellant controlling establishment of the tooth nerve supply. Furthermore, Sema3F, like Npn1, -2 and plexinA4 may serve non-neuronal functions by controlling the development of the ameloblast cell lineage. Moreover, Npn1 and Npn2 may regulate dental vasculogenesis and, together with PlexinA4, alveolar bone formation. Further analyses such as investigation of transgenic mouse models will be required to elucidate in vivo signaling functions of Sema3F and the receptors in odontogenesis.

Tooth injury increases expression of the cold sensitive TRP channel TRPA1 in trigeminal neurons

ObjectiveTransient receptor potential (TRP) channels, a family of structurally related proteins have been implicated in the sensation of pain and hyperalgesia caused by exogenous and endogenous agonists, as well as touch, pH, and temperature. The objective of this study was to determine the effects of tooth injury on the expression of the cold sensitive channel TRPA1, in the trigeminal ganglion, the primary source of sensory and nociceptive innervation of teeth. DesignWe analyzed TRPA1 expression in a rodent model of tooth injury, by Western blot analyses of proteins extracted from trigeminal ganglia. ResultsWe found that TRPA1 was selectively increased in trigeminal ganglia innervating injured teeth when compared to TRPA1 expression in trigeminal ganglia innervating healthy teeth. ConclusionsOur results provide the first evidence of increased expression of a cold-sensitive TRP channel in trigeminal ganglia after pulp exposure, and are consistent with the possibility that increased expression and function of TRPA1 in trigeminal neurons contributes to hyperalgesia and allodynia following tooth injury.

Development of the pioneer sympathetic innervation into the dental pulp of the mouse mandibular first molar

Objective Our goal was to study the development of pioneer sympathetic innervation of dental pulp of mouse mandibular first molar. Design We used double fluorescent immunohistochemistry with tyrosine hydroxylase (TH) and anti-medium-chain neurofilament (2H3) antibodies to detect sympathetic and sensory nerve fibres. Serial sections of whole teeth from postnatal days (PN) 0–14, trigeminal and sympathetic superior cervical ganglia of PN 15 mice were examined with confocal microscope. Results There were two main findings. The unexpected finding was that 2H3 antibody was specific only for sensory nerve fibres and neurons and failed to stain either sympathetic nerve fibres or neurons. The main finding was that although both sympathetic and sensory nerve fibres were already seen near the tooth germ at the newborn stage, the pioneer sympathetic nerve fibres were first observed in the dental pulp only after the onset of root formation on day 9, in contrast to sensory nerve fibres which entered the tooth already on day 4. Conclusion Pioneer sympathetic innervation of dental pulp starts on postnatal day 9 and follows sensory innervation. This indicates differential developmental regulation of the initial sensory and sympathetic innervation of teeth and provides essential background data for further studies on the molecular regulation of pulp innervation.