Autoantibodies to bullous pemphigoid antigen 180 induce dermal-epidermal separation in cryosections of human skin

Bullous pemphigoid is a subepidermal autoimmune blistering disease associated with autoantibodies to the hemidesmosomal bullous pemphigoid antigens 180 and 230. Most sera from bullous pemphigoid patients recognize epitopes within the N-terminal NC16A portion of the bullous pemphigoid 180 ectodomain. Using cryosections of human skin, patients' sera were shown to generate dermal-epidermal separation when coincubated with leukocytes and complement from healthy volunteers; however, the specificity of pathogenic autoantibodies in bullous pemphigoid patients has not yet been elucidated. In this study, by the use of a modified version of the cryosection model, we show that sera from all of 13 bullous pemphigoid patients and from two rabbits, immunized against bullous pemphigoid 180 NC16A, induced dermal-epidermal separation. This finding was confirmed with the use of IgG purified from patients' sera, whereas sera and purified IgG from healthy controls were not pathogenic. The induction of subepidermal splits in this experimental model was shown to be dependent on the presence of neutrophils, but not complement. Interestingly, patients' autoantibodies affinity purified against a recombinant form of bullous pemphigoid 180 NC16A retained their blister-inducing capacity, whereas patients' IgG depleted of reactivity to NC16A lost this ability. F(ab')2 fragments of antibodies specific to NC16A, lacking the Fc portion, did not induce splits. In addition, patients' autoantibodies purified against a recombinant fragment of the C-terminus of bullous pemphigoid 180 as well as rabbit antibodies to the intracellular portion of bullous pemphigoid 180 and to bullous pemphigoid 230 did not cause dermal-epidermal separation. Our in vitro results support the idea that autoantibodies to bullous pemphigoid 180 from patients with bullous pemphigoid are of pathogenic relevance.     

Central nervous system control mechanisms of swallowing: A neuropharmacological perspective

Neuropharmacologicalin vivo andin vitro investigations are beginning to provide insight into chemical signaling processes within brainstem networks controlling the individual stages of swallowing. Different subtypes of excitatory amino acid (EAA) receptors operate at the level of solitarial interneurons programming the buccopharyngeal and esophageal stage, as well as motoneurons innervating esophageal striated musculature. Muscarinic cholinoceptors (MAChRs), probably activated via a propriobulbar input, are critically involved in generating output from solitarial neurons to esophageal motoneurons. Inhibition to tonically active GABA_A-receptor mediated afferents to solitarial premotor neurons results in rhythmic deglutitive output, reflecting disinhibition of EAA and MACK receptor activity. Motoneuronal EAA receptors may be regulated by a somatostatinergic input arising from solitarial premotoneurons. The available evidence is consistent with a transmitter heterogeneity in esophageal premotor neurons that may operate to provide chemical coding of afferents to the motor output stage of the pattern generator for esophageal peristalsis.     

Polycaprolactone scaffold and reduced rhBMP-7 dose for the regeneration of critical-sized defects in sheep tibiae

The transplantation of autologous bone graft as a treatment for large bone defects has the limitation of harvesting co-morbidity and limited availability. This drives the orthopaedic research community to develop bone graft substitutes. Routinely, supra-physiological doses of bone morphogenetic proteins (BMPs) are applied perpetuating concerns over undesired side effects and cost of BMPs. We therefore aimed to design a composite scaffold that allows maintenance of protein bioactivity and enhances growth factor retention at the implantation site. Critical-sized defects in sheep tibiae were treated with the autograft and with two dosages of rhBMP-7, 3.5 mg and 1.75 mg, embedded in a slowly degradable medical grade poly(ε-caprolactone) (PCL) scaffold with β-tricalcium phosphate microparticles (mPCL–TCP). Specimens were characterised by biomechanical testing, microcomputed tomography and histology. Bridging was observed within 3 months for the autograft and both rhBMP-7 treatments. No significant difference was observed between the low and high rhBMP-7 dosages or between any of the rhBMP-7 groups and autograft implantation. Scaffolds alone did not induce comparable levels of bone formation compared to the autograft and rhBMP-7 groups. In summary, the mPCL–TCP scaffold with the lower rhBMP-7 dose led to equivalent results to autograft transplantation or the high BMP dosage. Our data suggest a promising clinical future for BMP application in scaffold-based bone tissue engineering, lowering and optimising the amount of required BMP.     

Numerical simulation and biomechanical analysis of an orthodontically treated periodontally damaged dentition

Background and objective

Once periodontitis has been completely resolved, one common follow-up method is to carry out orthodontic treatment to take advantage of the residual bone, i.e., via tooth intrusion. In this study, the biomechanical behavior of teeth in a reduced periodontium was studied by numerically simulating upper-incisor intrusion accomplished with various orthodontic mechanics.

Materials and methods

Using the finite element method, a patient-customized 3D model of a periodontally reduced dentition was generated in order to simulate tooth movement. The morphology of this upper-jaw model was derived from cone-beam computed tomography (CBCT) datasets of four patients. Material parameters were adopted from previous investigations, including teeth (E=20 GPa), periodontal ligament (PDL) (bilinear elastic; E₁=0.05 MPa; E₂=0.20 MPa; ε₁₂=7%), and bone (homogeneous, isotropic; E=2 GPa). Two intrusion scenarios were used, the first drawing from Burstone’s segmented-arch technique to intrude four splinted incisors at a time, and the second one using cantilevers to intrude single incisors. The aforementioned PDL material parameters were varied in several ways to simulate different biological and biomechanical states of PDL. All simulations were recalculated with an idealized, periodontally intact model to assess the effect of bone loss by way of comparison.

Results

Single-tooth intrusion via cantilever mechanics was accompanied by less rotation than the segmented-arch approach. Both intrusion systems involved significantly greater degrees of tooth displacement and PDL load in the periodontally reduced model.

Conclusion

Periodontally reduced dentitions are associated with an increased load on periodontal tissue. This can be counteracted by reducing orthodontic force levels and by selecting mechanics that do not harm the tissue. In so doing, the use of numerical methods may greatly facilitate individualized computer-aided treatment-planning strategies.