Enamel matrix derivative and bone grafts for periodontal regeneration of intrabony defects. A systematic review and meta-analysis

OBJECTIVE The aim of the present systematic review and meta-analysis was to assess the clinical efficacy of regenerative periodontal surgery of intrabony defects using a combination of enamel matrix derivative (EMD) and bone graft compared with that of EMD alone. MATERIALS AND METHODS The Cochrane Oral Health Group specialist trials, MEDLINE, and EMBASE databases were searched for entries up to February 2014. The primary outcome was gain of clinical attachment (CAL). Weighted means and forest plots were calculated for CAL gain, probing depth (PD), and gingival recession (REC). RESULTS Twelve studies reporting on 434 patients and 548 intrabony defects were selected for the analysis. Mean CAL gain amounted to 3.76 ± 1.07 mm (median 3.63 95 % CI 3.51-3.75) following treatment with a combination of EMD and bone graft and to 3.32 ± 1.04 mm (median 3.40; 95 % CI 3.28-3.52) following treatment with EMD alone. Mean PD reduction measured 4.22 ± 1.20 mm (median 4.10; 95 % CI 3.96-4.24) at sites treated with EMD and bone graft and yielded 4.12 ± 1.07 mm (median 4.00; 95 % CI 3.88-4.12) at sites treated with EMD alone. Mean REC increase amounted to 0.76 ± 0.42 mm (median 0.63; 95 % CI 0.58-0.68) at sites treated with EMD and bone graft and to 0.91 ± 0.26 mm (median 0.90; 95 % CI 0.87-0.93) at sites treated with EMD alone. CONCLUSIONS Within their limits, the present results indicate that the combination of EMD and bone grafts may result in additional clinical improvements in terms of CAL gain and PD reduction compared with those obtained with EMD alone. The potential influence of the chosen graft material or of the surgical procedure (i.e., flap design) on the clinical outcomes is unclear. CLINICAL RELEVANCE The present findings support the use of EMD and bone grafts for the treatment of intrabony periodontal defects.

Grafts, A. S., Currier, H. B. y Stocking, C. R. - El agua en la fisiología vegetal (Water in the physiology of plants); 40 pp. Ed. por Chronica Botanica Company, Waltham, Mass. USA., 1949

Fil: H. G. C..

Assessing priorities for allocation of donor liver grafts: survey of public and clinicians

Objectives: To compare the priorities of the general public, family doctors, and gastroenterologists in allocating donor livers to potential recipients of liver allograft.

Grafts of adenosine-releasing cells suppress seizures in kindling epilepsy

Adenosine is an inhibitor of neuronal activity in the brain. The local release of adenosine from grafted cells was evaluated as an ex vivo gene therapy approach to suppress synchronous discharges and epileptic seizures. Fibroblasts were engineered to release adenosine by inactivating the adenosine-metabolizing enzymes adenosine kinase and adenosine deaminase. After encapsulation into semipermeable polymers, the cells were grafted into the brain ventricles of electrically kindled rats, a model of partial epilepsy. Grafted rats provided a nearly complete protection from behavioral seizures and a near-complete suppression of afterdischarges in electroencephalogram recordings, whereas the full tonic–clonic convulsions in control rats remained unaltered. Thus, the local release of adenosine resulting in adenosine concentrations <25 nM at the site of action is sufficient to suppress seizure activity and, therefore, provides a potential therapeutic principle for the treatment of drug-resistant partial epilepsies.

Lymphocytes selected in allogeneic thymic epithelium mediate dominant tolerance toward tissue grafts of the thymic epithelium haplotype.

Athymic mice grafted at birth with allogeneic thymic epithelium (TE) from day 10 embryos before hematopoietic cell colonization reconstitute normal numbers of T cells and exhibit full life-long tolerance to skin grafts of the TE haplotype. Intravenous transfers of splenic cells, from these animals to adult syngeneic athymic recipients, reconstitute T-cell compartments and the ability to reject third-party skin grafts. The transfer of specific tolerance to skin grafts of the TE donor strain, however, is not observed in all reconstituted recipients, and the fraction of nontolerant recipients increases with decreasing numbers of cells transferred. Furthermore, transfers of high numbers of total or CD4+ T cells from TE chimeras to T-cell receptor-anti-H-Y antigen transgenic immunocompetent syngeneic hosts specifically hinder the rejection of skin grafts of the TE haplotype that normally occurs in such recipients. These observations demonstrate (i) that mice tolerized by allogeneic TE and bearing healthy skin grafts harbor peripheral immunocompetent T cells capable of rejecting this very same graft; and (ii) that TE selects for regulatory T cells that can inhibit effector activities of graft-reactive cells.

Genetic engineering of vein grafts resistant to atherosclerosis.

Previously, researchers have speculated that genetic engineering can improve the long-term function of vascular grafts which are prone to atherosclerosis and occlusion. In this study, we demonstrated that an intraoperative gene therapy approach using antisense oligodeoxynucleotide blockage of medial smooth muscle cell proliferation can prevent the accelerated atherosclerosis that is responsible for autologous vein graft failure. Selective blockade of the expression of genes for two cell cycle regulatory proteins, proliferating cell nuclear antigen and cell division cycle 2 kinase, was achieved in the smooth muscle cells of rabbit jugular veins grafted into the carotid arteries. This alteration of gene expression successfully redirected vein graft biology away from neointimal hyperplasia and toward medial hypertrophy, yielding conduits that more closely resembled normal arteries. More importantly, these genetically engineered grafts proved resistant to diet-induced atherosclerosis. These findings establish the feasibility of developing genetically engineered bioprostheses that are resistant to failure and better suited to the long-term treatment of occlusive vascular disease.

Bridging grafts and transient nerve growth factor infusions promote long-term central nervous system neuronal rescue and partial functional recovery.

Grafts of favorable axonal growth substrates were combined with transient nerve growth factor (NGF) infusions to promote morphological and functional recovery in the adult rat brain after lesions of the septohippocampal projection. Long-term septal cholinergic neuronal rescue and partial hippocampal reinnervation were achieved, resulting in partial functional recovery on a simple task assessing habituation but not on a more complex task assessing spatial reference memory. Control animals that received transient NGF infusions without axonal-growth-promoting grafts lacked behavioral recovery but also showed long-term septal neuronal rescue. These findings indicate that (i) partial recovery from central nervous system injury can be induced by both preventing host neuronal loss and promoting host axonal regrowth and (ii) long-term neuronal loss can be prevented with transient NGF infusions.

Human growth hormone presented by K14hGH-transgenic skin grafts induces a strong immune response but no graft rejection

Although immune responses leading to rejection of transplantable tumours have been well studied, requirements for epithelial tumour rejection are unclear. Here, we use human growth hormone (hGH) expressed in epithelial cells (skin keratinocytes) as a model neo-self antigen to investigate the consequences of antigen presentation from epithelial cells. Mice transgenic for hGH driven from the keratin 14 promoter express hGH in skin keratinocytes. This hGH-transgenic skin is not rejected by syngeneic non-transgenic recipients, although an antibody response to hGH develops in grafted animals. Systemic immunization of graft recipients with hGH peptides, or local administration of stimulatory anti-CD40 antibody, induces temporary macroscopic graft inflammation, and an obvious dermal infiltrate of inflammatory cells, but not graft rejection. These results suggest that a neo-self antigen expressed in somatic cells in skin can induce an immune response that can be enhanced further by induction of specific immunity systemically or non-specific immunity locally. However, immune responses do not always lead to rejection, despite induction of local inflammatory changes. Therefore, in vitro immune responses and in vivo delayed type hypersensitivity are not surrogate markers for immune responses effective against epithelial cells expressing neoantigens.

Dog peritoneal and pleural cavities as bioreactors to grow autologous vascular grafts

Objective: The purpose of this study was to grow artificial blood vessels for autologous transplantation as arterial interposition grafts in a large animal model (dog). Method and results: Tubing up to 250 mm long, either bare or wrapped in biodegradable polyglycolic acid (Dexon) or nonbiodegradable polypropylene (Prolene) mesh, was inserted in the peritoneal or pleural cavity of dogs, using minimally invasive techniques, and tethered at one end to the wall with a loose suture. After 3 weeks the tubes and their tissue capsules were harvested, and the inert tubing was discarded. The wall of living tissue was uniformly 1-1.5 mm thick throughout its length, and consisted of multiple layers of myofibroblasts and matrix overlaid with a single layer of mesothelium. The myofibroblasts stained for a-smooth muscle actin, vimentin, and desmin. The bursting strength of tissue tubes with no biodegradable mesh scaffolds was in excess of 2500 mm Hg, and the suture holding strength was 11.5 N, both similar to that in dog carotid and femoral arteries. Eleven tissue tubes were transplanted as interposition grafts into the femoral artery of the same dog in which they were grown, and were harvested after 3 to 6.5 months. Eight remained patent during this time. At harvest, their lumens were lined with endothelium-like cells, and wall cells stained for alpha-actin, smooth muscle myosin, desmin and smoothelin; there was also a thick adventitia containing vasa vasorum. Conclusion: Peritoneal and pleural cavities of large animals can function as bioreactors to grow myofibroblast tubes for use as autologous vascular grafts.

Improving the function of islet and beta-cell grafts

Background: Human islet transplantation would offer a less invasive and more physiological alternative than whole pancreas transplantation and insulin injections respectively for the treatment of diabetes mellitus if islet graft survival can be improved. Initial recipient post-transplant insulin independence declines to <10% after 5 years. Factors contributing to graft failure include enzymatic disruption of the islet microenvironment during isolation, diabetogenic effects of immunosuppressants and metabolic stress resulting from slow revascularisation. Aims: To investigate the effect of co-culture in both static (SC) and rotational culture (RC) of BRINBDII beta-cells (Dl1) and human umbilical vein endothelial cells (HUVEC) on Dl1 insulin secretion; and the effect of a thiazolidinedione (TZD) on DII function and HUVEC proliferation. To assess the effect of culture media, SC, RC and a TZD on human islet morphology, insulin secretion and VEGF production. To initiate in vivo protocol development for assessment of revascularisation of human islet grafts. Methods: D11 cells were cultured +/-TZD and co-cultured with HUVEC +/-TZD in SC and RC. Dl1 insulin secretion was induced by static incubation with low glucose (1.67mM), high glucose (l6.7mM: and high glucose with 10mM theophylline (G+T) and determined by ELISA. HUVEC were cultured +/-TZD in SC and RC and proliferation was assessed by ATP luminescence assay and VEGF ELISA. D II and HUVEC morphology was determined by immunocytochemistry. Human islets were cultured in SC and RC in various media +/-TZD. Insulin secretion was determined as above and VEGF production by fluorescence immunocytochemistry (FI) and ELISA. Revascularisation of islet grafts was assessed by vascular corrosion cast and FI. Results: Dll cultures showed significantly increased insulin secretion in response to 16.7mM and G+T over basal; this was enhanced by RC and further improved by adding 10mM TZD. Untreated Dll/HUVEC co-cultures displayed significantly increased insulin secretion in response to 16.7mM and G+T over basal, again enhanced by RC and improved with 10mM TZD. 10mM TZD significantly increased HUVEC proliferation over control. Human islets maintained in medium 199 (mI99) in SC and RC exhibited comparable maintenance of morphology and insulin secretory profiles compared to islets maintained in RPMI, endothelial growth media and dedicated islet medium Miami# I. All cultures showed significantly increased insulin secretion in response to 16.7mM and G+T over basal; this was enhanced by RC and in certain instances further improved by adding 25mM TZD. TZD increased VEGF production and release as determined by ELISA. Post-implant vascular corrosion casts of mouse kidneys analysed by x-ray micro tomography indicates a possible TZD enhancement of microvessel growth via VEGF upregulation. Conclusions: D II /HUVEC co-culture in SC or RC does not alter the morphology of either cell type and supports D 11 function. TZD improves 0 I I and D I I/HUVEC SC and RC co-culture insulin secretion while increasing HUVEC proliferation. Human islet RC supports islet functional viability and structural integrity compared to SC while the addition of TZD occasionally further improves secretagogue induced insulin secretion. Expensive, 'dedicated' islet media showed no advantage over ml99 in terms of maintaining islet morphology or function. TZD upregulates VEGF in islets as shown by ELISA and suggested by x-ray micro tomography analysis of vascular corrosion casts. Maintenance of islets in RC and treatment with TZD prior to transplant may improve the functional viability and revascularisation rate of islet grafts.