The Effect of Sensory Innervation on the Inorganic Component of Bones and Teeth; Experimental Denervation - Review

Effect of Inferior Alveolar Nerve Transection on the Inorganic Component of Molars of Rat Mandible

The objective of the study was to determine the effects of inferior alveolar nerve transection on inorganic components in mandibular molars of the rat. We used 26 male laboratory rats of the Wistar strain for the study, age 7-9 weeks. The rats were divided in three groups. The control group (intact) included 6 rats. The surgery was performed under general anesthesia. The experimental group included (group with the nerve transected on the left) included 12 rats. The sham group (group with the nerve prepared without transection) included 8 rats. The animals were sacrificed after 4 weeks. Molars from the left and right sides of the mandible were extracted. Element content levels were determined using inductively coupled plasma mass spectrometry. The following elements were determined in all samples: magnesium (Mg), sodium (Na), potassium (K), calcium (Ca), zinc (Zn), and strontium (Sr). The nerve transection caused: a reduction of the contents of Ca and Sr in the mandibular molars; an increase in the contents of Mg and Zn; a difference arrangement of both sides for Na. The surgery approach itself caused a decrease in the contents of Na and K in the experimental and sham groups; the difference in K in M3 between the left and right sides disappeared due to the surgery. Our results have confirmed the hypothesis of inferior alveolar nerve transection having an effect on inorganic components in mandibular molars in the rat.

Stratified-structural hydrogel incorporated with magnesium-ion-modified black phosphorus nanosheets for promoting neuro-vascularized bone regeneration

Angiogenesis and neurogenesis play irreplaceable roles in bone repair. Although biomaterial implantation that mimics native skeletal tissue is extensively studied, the nerve-vascular network reconstruction is neglected in the design of biomaterials. Our goal here is to establish a periosteum-simulating bilayer hydrogel and explore the efficiency of bone repair via enhancement of angiogenesis and neurogenesis. In this contribution, we designed a bilayer hydrogel platform incorporated with magnesium-ion-modified black phosphorus (BP) nanosheets for promoting neuro-vascularized bone regeneration. Specifically, we incorporated magnesium-ion-modified black phosphorus (BP@Mg) nanosheets into gelatin methacryloyl (GelMA) hydrogel to prepare the upper hydrogel, whereas the bottom hydrogel was designed as a double-network hydrogel system, consisting of two interpenetrating polymer networks composed of GelMA, PEGDA, and β-TCP nanocrystals. The magnesium ion modification process was developed to enhance BP nanosheet stability and provide a sustained release platform for bioactive ions. Our results demonstrated that the upper layer of hydrogel provided a bionic periosteal structure, which significantly facilitated angiogenesis via induction of endothelial cell migration and presented multiple advantages for the upregulation of nerve-related protein expression in neural stem cells (NSCs). Moreover, the bottom layer of the hydrogel significantly promoted bone marrow mesenchymal stem cells (BMSCs) activity and osteogenic differentiation. We next employed the bilayer hydrogel structure to correct rat skull defects. Based on our radiological and histological examinations, the bilayer hydrogel scaffolds markedly enhanced early vascularization and neurogenesis, which prompted eventual bone regeneration and remodeling. Our current strategy paves way for designing nerve-vascular network biomaterials for bone regeneration.

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Developing a periosteum-simulating bilayer hydrogel to improve the efficiency of neuro-vascularized bone repair.

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A magnesium-ion-modified black phosphorus (BP) nanosheets incorporated hydrogel platform was designed.

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Designing nerve-vascular network biomaterials for bone regeneration.

Nanocellulose-Reinforced Hydroxyapatite Nanobelt Membrane as a Stem Cell Multi-Lineage Differentiation Platform for Biomimetic Construction of Bioactive 3D Osteoid Tissue In Vitro

Severe bone defects, especially accompanied by vascular and peripheral nerve injuries, remain a massive challenge. Most studies related to bone tissue engineering have focused on osteogenic differentiation of mesenchymal stem cells (MSCs), and ignored the formation of blood vessels and nerves in the newly generated bone owing to the lack of proper materials and methodology for tuning stem cells differentiated into osteogenic, neuronal, and endothelial cells (ECs) in the same scaffold system. Herein, a nanocellulose-reinforced hybrid membrane with good mechanical properties and control over biodegradation by assembling ultralong hydroxyapatite nanobelts in a bacterial nanocellulose hydrogel is designed and synthesized. Osteogenic, neuronal cells are successfully differentiated on this hybrid membrane. Based on the multi-lineage differentiation property of the membrane, a bioactive 3D osteoid tissue (osteogenic, neural, and ECs) is mimetically constructed in vitro using layer-by-layer culture and integration. The bone regeneration ability of the as-prepared bioactive osteoid tissue is assessed in vivo via heterotopic osteogenesis experiments for eight weeks. The rapid new bone growth and formation of blood capillaries and nerve fibers prove that the hybrid membrane can be universally applied as a stem cell multi-lineage differentiation platform, which has significant applications in bone tissue engineering.

Sensory neurons from dorsal root ganglia regulate endothelial cell function in extracellular matrix remodelling

BACKGROUND

Recent physiological and experimental data highlight the role of the sensory nervous system in bone repair, but its precise role on angiogenesis in a bone regeneration context is still unknown. Our previous work demonstrated that sensory neurons (SNs) induce the osteoblastic differentiation of mesenchymal stem cells, but the influence of SNs on endothelial cells (ECs) was not studied.

METHODS

Here, in order to study in vitro the interplay between SNs and ECs, we used microfluidic devices as an indirect co-culture model. Gene expression analysis of angiogenic markers, as well as measurements of metalloproteinases protein levels and enzymatic activity, were performed.

RESULTS

We were able to demonstrate that two sensory neuropeptides, calcitonin gene-related peptide (CGRP) and substance P (SP), were involved in the transcriptional upregulation of angiogenic markers (vascular endothelial growth factor, angiopoietin 1, type 4 collagen, matrix metalloproteinase 2) in ECs. Co-cultures of ECs with SNs also increased the protein level and enzymatic activity of matrix metalloproteinases 2 and 9 (MMP2/MMP9) in ECs.

CONCLUSIONS

Our results suggest a role of sensory neurons, and more specifically of CGRP and SP, in the remodelling of endothelial cells extracellular matrix, thus supporting and enhancing the angiogenesis process. Video abstract.

The Role of Acid-sensing Ion Channel 3 in the Modulation of Tooth Mechanical Hyperalgesia Induced by Orthodontic Tooth Movement

This study aimed to explore the role of acid-sensing ion channel 3 (ASIC3) in the modulation of tooth mechanical hyperalgesia induced by orthodontic tooth movement. In male Sprague-Dawley rats, closed coil springs were ligated between mandibular incisors and molars to mimic orthodontic tooth movement. Bite force was assessed to evaluate tooth mechanical hyperalgesia. The alveolar bone, trigeminal ganglia, and trigeminal nucleus caudalis underwent immunohistochemical staining and immunoblotting for ASIC3. The inferior alveolar nerves were transected to explore the interaction between the periodontal sensory endings and trigeminal ganglia. The role of ASIC3 in trigeminal ganglia was further explored with lentivirus-mediated ASIC3 ribonucleic acid interference. Results showed that ASIC3 was expressed in the periodontal Ruffini endings and expression of ASIC3 protein was elevated in periodontal tissues, trigeminal ganglia, and trigeminal nucleus caudalis, following orthodontic tooth movement. ASIC3 agonists and antagonists significantly aggravated and mitigated tooth mechanical hyperalgesia, respectively. ASIC3 expression decreased after inferior alveolar nerve transection in periodontal tissues. Both in vitro and vivo, the lentivirus vector carrying ASIC3 shRNA inhibited ASIC3 expression and relieved tooth mechanical hyperalgesia. To conclude, ASIC3 is important in the modulation of tooth mechanical hyperalgesia induced by orthodontic tooth movement. Further, the role of ASIC3 in the modulation of pain in periodontal tissues is regulated by trigeminal ganglia. An adjuvant analgesic therapy targeting ASIC3 could alleviate orthodontic movement-associated mechanical hyperalgesia in rats.

Development of a cell-free and growth factor-free hydrogel capable of inducing angiogenesis and innervation after subcutaneous implantation

Despite significant progress in the field of biomaterials for bone repair, the lack of attention to the vascular and nervous networks within bone implants could be one of the main reasons for the delayed or impaired recovery of bone defects. The design of innovative biomaterials should improve the host capacity of healing to restore a functional tissue, taking into account that the nerve systems closely interact with blood vessels in the bone tissue. The aim of this work is to develop a cell-free and growth factor-free hydrogel capable to promote angiogenesis and innervation. To this end, we have used elastin-like polypeptides (ELPs), poly(ethylene glycol) (PEG) and increasing concentrations of the adhesion peptide IKVAV (25% (w/w) representing 1.7 mM and 50% (w/w) representing 4.1 mM) to formulate and produce hydrogels. When characterized in vitro, hydrogels have fine-tunable rheological properties, microporous structure and are biocompatible. At the biological level, 50% IKVAV composition up-regulated Runx2, Osx, Spp1, Vegfa and Bmp2 in mesenchymal stromal cells and Tek in endothelial cells, and sustained the formation of long neurites in sensory neurons. When implanted subcutaneously in mice, hydrogels induced no signals of major inflammation and the 50% IKVAV composition induced higher vessel density and formation of nervous terminations in the peripheral tissue. This novel composite has important features for tissue engineering, showing higher osteogenic, angiogenic and innervation potential in vitro, being not inflammatory in vivo, and inducing angiogenesis and innervation subcutaneously. STATEMENT OF SIGNIFICANCE: One of the main limitations in the field of tissue engineering remains the sufficient vascularization and innervation during tissue repair. In this scope, the development of advanced biomaterials that can support these processes is of crucial importance. Here, we formulated different compositions of Elastin-like polypeptide-based hydrogels bearing the IKVAV adhesion sequence. These compositions showed controlled mechanical properties, and were degradable in vitro. Additionally, we could identify in vitro a composition capable to promote neurite formation and to modulate endothelial and mesenchymal stromal cells gene expression, in view of angiogenesis and osteogenesis, respectively. When tested in vivo, it showed no signs of major inflammation and induced the formation of a highly vascularized and innervated neotissue. In this sense, our approach represents a potential advance in the development of new strategies to promote tissue regeneration, taking into account both angiogenesis and innervation.