Tissue Bridge Research Articles

Peripheral nerve-speci?c extracellular matrix hydrogel supports repair after peripheral nerve injury

Event Abstract Back to Event Peripheral nerve-specific extracellular matrix hydrogel supports repair after peripheral nerve injury Travis Prest1, 2, Meghan Wyatt1, Dhruv Srinivasachar1 and Bryan N. Brown1, 2, 3 1 University of Pittsburgh, Department of Bioengineering, United States 2 University of Pittsburgh, McGowan Institute for Regenerative Medicine, United States 3 Cornell University, Department of Biomedical Engineering, United States Introduction: Peripheral nerve injury commonly results in loss of neuromuscular function, often resulting in significant impact upon both quality of life and cost of care for patients. Surgical reconstruction of damaged peripheral nerves is possible, but recovery is slow and unpredictable and restoration of function is often incomplete. An easily injectable material in an off the shelf formulation which speeds and/or improves return to function would significantly improve quality of life for affected patients and result in a significant reduction of cost associated with chronic care related to their condition. Rather than attempting to engineer a complex microenvironment, an alternative would be to use the natural microenvironment of a healthy peripheral nerve through decellularization. We believe that a peripheral nerve specific extracellular matrix hydrogel (PNS-ECM) will provide a tissue-specific microenvironment which is conducive to nerve repair, including: nerve specific growth factors that are chemotactic signals for Schwann cells, promote neurite outgrown, and provide immune modulatory activity. Materials and Methods: Porcine sciatic nerve was decellularized to generate PNS-ECM using a previously described method [1]. PNS-ECM was compared in vitro to small-intestinal submucosa matrix (SIS) and urinary bladder matrix (UBM). Experiments included nerve specific growth factor ELISAs, neurite outgrowth, and Schwann cell migration assays. ). Neurite outgrowth performed using primary spinal cord neurons collected from E14 embryonic rat pups. Media was supplemented with PNS-ECM at low concentrations (125, 250, or 500 μg/ml), pepsin (50 μg/ml, negative control), or nerve growth factor (NGF 50 pg/ml, positive control). Schwann cell migration was performed using a boyden chamber with serum supplemented media with 50 or 100 pg/mg NGF as a positive control and negative controls were serum free media with pepsin and ECM supplemented on cell side only. The PNS-ECM was then used as a lumen filler during the repair of critical length gap nerve injury in a rodent sciatic nerve. Animals were sacrificed at days 7, 14, 28, and 90 and the nerves and gastrocnemius were harvested in %10 NBF. Nerves were investigated for macrophage involvement and potential phenotypic changes caused by PNS-ECM as well as the effect on the rate of outgrowth of Schwann cells and axons across a 15 mm nerve gap. Slides of the nerve were stained for axons (β-tubulin III), Schwann cells (S-100), and M1 (CD86), M2 (CD206), and pan (CD68) macrophage markers. Muscles sections were stained with collagen V and muscle fiber diameter was measured. Results and Discussion: PNS-ECM has a similar nerve specific growth factor profile to healthy nerve tissue, including high levels of nerve growth factor (NGF; PNS-ECM 6.1±0.6 pg/mg, healthy nerve 6.0±0.8 pg/mg), brain derived neurotrophic factor (BDNF; PNS-ECM 8.8±1.1 pg/mg, healthy nerve 10.8±0.6 pg/mg), and ciliary neurotrophic factor (CNTF; PNS-ECM 10.2±0.5 pg/mg, healthy nerve 10.2±0.4 pg/mg). SIS and UBM were dissimilar to native nerve except for SIS and BDNF (SIS 8.4±1.5 pg/mg and UBM and NFG (UBM 4.7±0.5 pg/mg). Outgrowth of cells supplemented with higher concentrations of PNS-ECM (250 and 500 μg/ml) were as much as 40% greater than negative control and the application of PNS-ECM showed a dose dependent effect that at 500 μg/ml promoted 80% of positive control. PNS-ECM produced similar migration to positive controls (serum supplemented media, with 50 ng/ml NGF, and with 100 ng/ml NGF). Treatment was statistically greater than negative controls (pepsin and PNS-ECM on cell side only). In vivo preliminary data suggest the use of PNS-ECM produced a more robust connective tissue bridge during the first weeks post-surgery. Axon migration into the connective tissue bridge appears to be enhanced by PNS-ECM compared to saline control. PNS-ECM groups have significantly less atrophy at 28 and 90 days (48±2, 68±1) than saline control (59±2, 75±1). Conclusions: In vitro experiments show chemotactic bioactivity of the PNS-ECM degradation products. Animal results suggest that treatment with PNS-ECM gel improved outcomes metrics after repair of a critical length defect.

Surface quality of human corneal SMILE lenticules in comparison with microkeratome free caps

Purpose The aim of this study was to compare electron microscopic morphological images of the posterior surface of corneal lenticules removed during femtosecond laser small-incision lenticule extraction (SMILE) with free corneal caps created using a mechanical microkeratome. Design An in-vitro comparative study was carried out including 30 human corneal lenticules from 15 patients who underwent bilateral SMILE refractive procedure (SMILE group) using the 500 kHz VisuMax femtosecond laser and 20 cadaveric donor corneas that were cut creating free caps using the Moria M2 microkeratome. Setting The present study was carried out at Roayah Vision Correction Center and Faculty of Science, Alexandria University. Participants and methods A total of 15 SMILE lenticules and 15 microkeratome free caps were examined by scanning electron microscopy (SEM), and another 15 SMILE lenticules and five microkeratome free caps were examined by transmission electron microscopy. The JEOL JSM-5300LV SEM was used for observations. A new scoring system was used for comparison. Results The surface and edge of SMILE lenticules showed more roughness in the form of tissue bridges, dome-shaped elevations, more cavitational changes, and tiny tissue fragments compared with the undersurface of free corneal microkeratome caps, but the difference was not statistically significant on SEM ( P =0.40654). Conclusion SMILE induces corneal surface roughness and structural changes that are slightly more pronounced than those induced by the microkeratome. The observed changes may cause surgically induced optical aberrations. Energy settings still need further adjustment to be able to create reproducible, predictable smooth surfaces in lenticules of SMILE cases.

Dentinogenic Specificity in the Preclinical Evaluation of Vital Pulp Treatment Strategies: A Critical Review.

Reviews on the clinical performance of vital pulp treatment strategies and capping materials repeatedly showed an insufficient grade of evidence concerning their therapeutic validity. The biological mechanisms underlying the regenerative potential of pulp-dentin complex have attracted much attention during the last two decades, since new pulp treatment modalities have been designed and tested at the preclinical level. It has been recognized that evaluation should be based on the specific ability of therapeutic interventions to signal recruitment and differentiation of odontoblast-like cells forming a matrix in a predentin-like pattern, rather than uncontrolled hard tissue deposition in a scar-like form. The aim of the present article was to critically review data from histological experimental studies on pulp capping, published during the last 7 decades. A comprehensive literature search covering the period from 1949 to 2015 was done using the Medline/Pubmed database. Inclusion of a study was dependent on having sufficient data regarding the type of capping material used and the unit of observation (human permanent tooth in vivo or animal permanent dentition; primary teeth were excluded). The post-operatively deposited matrix was categorized into three types: unspecified, osteotypic, or dentin-like matrix. One hundred fifty-two studies were included in the final evaluation. Data from the present systematic review have shown that only 30.2% of the 152 experimental histological pulp capping studies described the heterogenic nature of the hard tissue bridge formation, including osteotypic and tubular mineralized tissue. Structural characteristics of the new matrix and the associated formative cells were not provided by the remaining 106 studies. Analysis showed that more careful preclinical evaluation with emphasis on the evidence regarding the dentinogenic specificity of pulp therapies is required. It seems that selection of appropriate vital pulp treatment strategies and pulp capping materials would be further facilitated in terms of their therapeutic validity if international consensus could be reached on a select number of mandatory criteria for tissue-specific dentinogenic events.

Femtosecond Laser-Assisted Deep Lamellar Endothelial Keratoplasty: A New Approach to a Forgotten Technique.

To review indications and clinical results for a hybrid deep lamellar endothelial keratoplasty (Femto-DLEK) technique combining contemporary donor tissue preparation and implantation techniques with femtosecond laser-assisted dissection of the host tissue. A retrospective analysis of consecutive cases of Femto-DLEK performed between 2011 and 2014 at Moorfields Eye Hospital, London, was conducted. All patients underwent manifest refraction and optical coherence tomography examination at their most recent review visit. Secondary interventions, graft rejection, and graft failure were recorded alongside corrected distance visual acuity. Femto-DLEK was performed in 7 eyes of 7 cases. Mean postoperative follow-up duration was 19 months. Indications included revision of deep anterior lamellar keratoplasty (n = 4), revision of failed Descemet stripping endothelial keratoplasty in cases with an anterior chamber intraocular lens (n = 2), and primary surgery in cases of dense posterior stromal copper deposition. All corneas were recorded as clear by 6 weeks after surgery. Median (range) preoperative corrected distance visual acuity was 6/60 (6/9-1/60), which improved to 6/9 (6/6-6/24) at final review. Tissue bridges requiring significant additional manual lamellar dissection were present in all 4 cases in which deep stromal femtosecond laser lamellar dissection was performed. Femtosecond laser host dissection in the remaining cases was restricted to only a posterior side-cut. Femto-DLEK is a useful alternative endothelial keratoplasty modality for a narrow range of indications. The femtolaser posterior side-cut facilitates DLEK, but further development of the Femto-DLEK technique is required to optimize the combination with deep lamellar host dissection.

The future of BRS in bifurcations.

Bioresorbable scaffolds (BRS) provide a new tool for percutaneous treatment of coronary stenosis. Initially, relatively simple coronary artery lesions were treated with this novel technology; nowadays, we have gained more experience with a wide variety of lesions, including bifurcation lesions. Data are limited in terms of the use of BRS in coronary bifurcation lesions, although it has been demonstrated that over time the bioresorbable struts are replaced by a tissue bridge resembling a "neo-carina". Furthermore, data are emerging about the endothelial shear stress (ESS) alterations and blood flow patterns after scaffold implantation. It is likely that ESS and blood flow determinations will guide correct future bifurcation techniques. In the future, BRS with thinner struts and more resistant to fracture are likely to improve bifurcation treatment with BRS.

Nano-hydroxyapatite and calcium-enriched mixture for pulp capping of sound primary teeth: a randomized clinical trial.

Nano-hydroxyapatite (NHA) has been used for regeneration of osseous defects. Calcium-enriched mixture (CEM) cement is also used for various dental treatments. This trial compared the efficacy of NHA and CEM cement for direct pulp capping (DPC) of sound primary teeth. In this randomized clinical trial with split-mouth design, after attaining informed consent, 20 sound primary canines scheduled for orthodontic extraction, were selected. After mechanical pulp exposure, the exposed site was capped with either NHA or CEM cement and then immediately restored with glass-ionomer and resin composite. The teeth were extracted after two months and examined histologically. Parameters of hard tissue bridge (HTB) formation, its type and quality as well as pulpal inflammation scores were compared between the two experimental groups. The data were analyzed using the Mann Whitney U and Fisher's exact test. The level of significance was set at 0.001. All CEM specimens showed inflammation score of 0 (less than 10%). However, in NHA group, inflammation scores of 0 (less than 10%), 1 (10%-30%) and 2 (30%-50%) were observed in 2 (20%), 4 (40%) and 4 (40%) specimens, respectively (P<0.001). HTB was formed in all CEM specimens while it was developed in 2 specimens of NHA (20%; P<0.001). All CEM specimens showed normal pulp; only two cases in NHA group (20%) demonstrated uninflamed normal pulp. CEM cement was superior to NHA as a DPC agent in terms of HTB formation and pulp inflammation scores. It is a suitable material for the DPC of primary teeth.

Histological Evaluation of Single and Double-visit Direct Pulp Capping with Different Materials on Sound Human Premolars: A Randomized Controlled Clinical Trial.

The aim of this study was to evaluate the clinical and histological status of the pulp in sound human premolars after direct pulp capping (DPC) with four different DPC methods/materials. This study was conducted on eight volunteers who had to extract four first premolars due to orthodontic treatment. Subsequent to tooth isolation, standardized class I occlusal cavities were prepared and the buccal pulp horns were exposed. Then four different protocols of DPC were applied randomly: group A (control); calcium hydroxide lining paste (Dycal), group B; ProRoot MTA (standard double-visit method), group C; ProRoot MTA (single-visit method) and group D; calcium hydroxide injectable paste (Multi-Cal). The cavities were then restored and the patients were put on a six-week clinical follow-up and by the end of this period the teeth were extracted for histological evaluation. Data were analyzed with the Kruskal Wallis test and the level of significance was set at 0.05. In terms of clinical symptoms and formation of hard tissue bridge (HTB), no significant differences were found between groups A, B and C (P>0.05); however, group D's results were significantly different as they exhibited minimal HTB formation and excessive sensitivity (P<0.05). Inflammation was significantly lower in group B (P>0.05). Application of MTA during a single-visit protocol of DPC was clinically and histologically as successful as the standard double-visit method but the routine use of Multi-Cal as pulp capping material is questionable and should be reconsidered.

Extraperitoneally Ruptured, Everted, and Prolapsed Bladder: A Very Rare Complication of Pelvic Injury.

Traumatic rupture of the bladder with eversion and protrusion via the perineum is a rare complication of pelvic injury. We present a 36-year-old lady who sustained severe pelvic injury with a bleeding right-sided deep perineal laceration. She had closed reduction of pelvic fracture with pelvic banding and primary closure of perineal laceration at a private hospital. She subsequently had dehiscence of repaired perineal laceration with protrusion of fleshy mass from vulva and leakage of urine per perineum five weeks later. Examination revealed a fleshy mucosa-like mass protruding anteriorly with a bridge of tissue between it and right anterolateral vaginal wall. Upward pressure on this mass revealed the bladder neck and ureteric orifices. She had perineal and pelvic exploration with findings of prolapsed, completely everted bladder wall through a transverse anterior bladder wall rent via the perineum, and an unstable B1 pelvic disruption. She had repair of the ruptured, everted, and prolapsed bladder, double-plate and screw fixation of disrupted pelvis and repair of the pelvic/perineal defect. She commenced physiotherapy and ambulation a week after surgery. Patient now walks normally and is continent of urine. We conclude that the intrinsic urethral continent mechanism plays a significant role in maintaining continence in females.

Mesh implants: An overview of crucial mesh parameters.

Hernia repair is one of the most frequently performed surgical interventions that use mesh implants. This article evaluates crucial mesh parameters to facilitate selection of the most appropriate mesh implant, considering raw materials, mesh composition, structure parameters and mechanical parameters. A literature review was performed using the PubMed database. The most important mesh parameters in the selection of a mesh implant are the raw material, structural parameters and mechanical parameters, which should match the physiological conditions. The structural parameters, especially the porosity, are the most important predictors of the biocompatibility performance of synthetic meshes. Meshes with large pores exhibit less inflammatory infiltrate, connective tissue and scar bridging, which allows increased soft tissue ingrowth. The raw material and combination of raw materials of the used mesh, including potential coatings and textile design, strongly impact the inflammatory reaction to the mesh. Synthetic meshes made from innovative polymers combined with surface coating have been demonstrated to exhibit advantageous behavior in specialized fields. Monofilament, large-pore synthetic meshes exhibit advantages. The value of mesh classification based on mesh weight seems to be overestimated. Mechanical properties of meshes, such as anisotropy/isotropy, elasticity and tensile strength, are crucial parameters for predicting mesh performance after implantation.

Sensory regeneration in dorsal root avulsion.

Brachial as well as lumbosacral plexus avulsion injuries are usually caused by high kinetic traumas, such as car-pedestrian, car and motorcycle accidents or falls from great heights. Traction forces affecting the head and shoulders or extremities pull the spinal nerve sleeves away from the spinal cord and rupture the postganglionic spinal root from the cord. In so called central avulsion injuries, the spinal root is avulsed at the interface between the central and peripheral nervous system (CNS and PNS). This results not only in the disconnection of the root from the cord but also in a longitudinal spinal cord injury. The complexity of the injury leads to degeneration of the spinal root and a marked inflammatory response of the spinal cord followed by the formation of a glial scar (Kachramanoglou et al., 2011).

Light and electron microscopic study of placenta in pre-eclampsia: a trial to define underlying changes and its clinical impact

Objectives The aim of this study was to evaluate histological changes of placental villi and blood vessels in pregnancy complicated by pre-eclampsia (PE) and their relation with clinical data. Patients and methods The study included 100 pregnant women developing PE at any time during pregnancy (PE group) and 100 pregnant women free of PE (control group). Collected data included age, gestational age, manifestations and severity of PE, neonatal birth weight (BW), and placental weight (PW). Placental tissue was obtained for light and electron microscopic examination. Results BW and PW showed a significant negative correlation with maternal BMI and the presence and severity of PE. Gestational age and development of PE were significant predictors for low PW, which is a significant predictor for low BW. Placentas of the PE group showed aggregation of syncytiotrophoblast cells, hyaline degeneration of connective tissue core, and endothelial lining of stem blood vessel; villous core was devoid of fetal blood vessel. Diffuse fibrous tissue formation, hypertrophic musculosa of stem blood vessel up to endarteritis obliterans and placental tissue bridges crossing intervillous spaces and villous arborization formed only of connective tissue with no cellular elements were observed. Electron microscopy confirmed these findings and showed attenuated blood vessels and excessive villous arborization covered with fibrin-like material. Conclusion Development of placental endarteritis obliterans with diminution of placental growth and proper invasion may underlie development of PE. Reduced PW is a reflection of this histological affection and is negatively correlated with severity of PE. Early PE is associated with more severe clinical manifestation and aggressive histological changes.

Laser-assisted mini-capsulotomy: a new technique for intumescent white cataracts.

To describe a new two-step femtosecond laser-assisted technique for intumescent white cataracts. In 6 eyes with intumescent white cataracts, a laser-assisted mini-capsulotomy was performed first to release the intralenticular pressure. In the next step, the fluid milky lens material was removed from the anterior chamber before the eyes were re-docked to the laser system and a second larger anterior capsulotomy (4.5-mm diameter) was performed. Finally, the cataractous lens material was removed followed by intraocular lens implantation in the capsular bag. In all cases, the laser system was able to identify and cut the anterior capsule without complications. Small residual tissue bridges were recognized after laser-assisted mini-capsulotomy in 2 eyes and solved with the dimple-down maneuver. The second, larger capsulotomy demonstrated satisfactory quality and a 360° overlap on the intraocular lens' optic was achieved in all cases. This novel technique for intumescent white cataracts using a two-step laser-assisted mini-capsulotomy has the potential to avoid complications.

Dentinogenic Responses after Direct Pulp Capping of Miniature Swine Teeth with Biodentine

IntroductionThe aim of this study was to evaluate pulpal responses after experimental direct pulp capping of mechanically exposed teeth with a new calcium silicate–based dentin replacement material. MethodsThirty-four anterior and posterior teeth of 3 miniature swine were used. Class V or I cavities were prepared on the buccal or occlusal surfaces, respectively. Pulpal exposures were further performed using a round carbide bur 0.8 mm in diameter. Exposures were treated with white MTA Angelus (Angelus, Londrina, PR, Brazil) or Biodentine (Septodont, Saint Maur des Fosses, France), and the cavities were further restored with Biodentine. The pulpal tissue responses were histologically assessed at postoperative periods of 3 and 8 weeks. Data were statistically analyzed using the Kruskal Wallis and the Mann-Whitney U tests. ResultsInflammatory infiltration or pulp tissue necrosis was not found in any of the specimens. All teeth showed mineralized matrix formation in the form of a complete hard tissue bridge composed of osteodentin or osteodentin followed by a discontinuous or continuous reparative dentin zone. A significantly higher thickness of the hard tissue bridge was found in the group of teeth treated with Biodentine at both 3 and 8 weeks. A number of teeth, which were under root development at the onset of the experimental procedures, exhibited ectopic pulp calcification. ConclusionsThe application of both calcium silicate–based materials in direct contact with the mechanically exposed pulp of healthy miniature swine teeth led to pulp repair with complete hard tissue bridge formation. The thickness of hard tissue bridges was significantly higher after pulp capping with Biodentine.

Effects of sodium hypoclorite as disinfectant material previous to pulpotomies in primary teeth.

Sodium hypochlorite (NaOCl) can be used to promote healing vital pulpotomies as an antibacterial agent. The aim of the present study was to histologically analyze the pulpal response of human primary teeth pulp following calcium hydroxide (CH) and mineral trioxide aggregate (MTA) pulpotomies with and without 5% NaOCl. One hundred twenty-eight primary molars were randomly divided into two main groups according to pulpotomy material (CH/MTA) and into two subgroups according to selected cleansing agent (NaOCl/physiologic saline) used in the pulpotomy procedure. Thirty-four successfully treated teeth whose successor roots had completed formation of at least two thirds of their lengths were extracted for histological evaluation. Fisher's exact test, Pearson's Chi-square test, and Mann-Whitney U test with Bonferroni correction were used for statistical analysis. No significant differences in any of the tested parameters were observed between the NaOCl and physiologic saline subgroups of either the CH or MTA groups. Pulpal inflammation was significantly higher in the CH-treated teeth as compared with the MTA-treated teeth, whereas hard tissue bridge formation was significantly higher in the MTA-treated teeth as compared with the CH-treated teeth but regardless of cleansing agent (p < 0.025). The use of NaOCl does not affect the success of CH or MTA pulpotomies. Regardless of cleansing agent, MTA was found to be superior to CH. The proper medicament selection is more important than the choice of cleaning agent in vital pulpotomies.

Nanoscale helium ion microscopic analysis of collagen fibrillar changes following femtosecond laser dissection of human cornea.

Over the last decade, femtosecond lasers have emerged as an important tool to perform accurate and fine dissections with minimal collateral damage in biological tissue. The most common surgical procedure in medicine utilizing femtosecond laser is LASIK. During the femtosecond laser dissection process, the corneal collagen fibers inevitably undergo biomechanical and thermal changes on a sub-micro- or even a nanoscale level, which can potentially lead to post-surgical complications. In this study, we utilized helium ion microscopy, complemented with transmission electron microscopy to examine the femtosecond laser-induced collagen fibrillar damage in ex vivo human corneas. We found that the biomechanical damage induced by laser etching, generation of tissue bridges, and expansion of cavitation bubble and its subsequent collapse, created distortion to the surrounding collagen lamellae. Femtosecond laser-induced thermal damage was characterized by collapsed collagen lamellae, loss of collagen banding, collagen coiling, and presence of spherical debris. Our findings have shown the ability of helium ion microscopy to provide high resolution images with unprecedented detail of nanoscale fibrillar morphological changes in order to assess a tissue damage, which could not be resolved by conventional scanning electron microscopy previously. This imaging technology has also given us a better understanding of the tissue-laser interactions in a nano-structural manner and their possible effects on post-operative wound recovery.

A re-assessment of long distance growth and connectivity of neural stem cells after severe spinal cord injury

As part of the NIH “Facilities of Research Excellence—Spinal Cord Injury” project to support independent replication, we repeated key parts of a study reporting robust engraftment of neural stem cells (NSCs) treated with growth factors after complete spinal cord transection in rats. Rats (n=20) received complete transections at thoracic level 3 (T3) and 2weeks later received NSC transplants in a fibrin matrix with a growth factor cocktail using 2 different transplantation methods (with and without removal of scar tissue). Control rats (n=9) received transections only. Hindlimb locomotor function was assessed with the BBB scale. Nine weeks post injury, reticulospinal tract axons were traced in 6 rats by injecting BDA into the reticular formation. Transplants grew to fill the lesion cavity in most rats although grafts made with scar tissue removal had large central cavities. Grafts blended extensively with host tissue obliterating the astroglial boundary at the cut ends, but in most cases there was a well-defined partition within the graft that separated rostral and caudal parts of the graft. In some cases, the partition contained non-neuronal scar tissue. There was extensive outgrowth of GFP labeled axons from the graft, but there was minimal ingrowth of host axons into the graft revealed by tract tracing and immunocytochemistry for 5HT. There were no statistically significant differences between transplant and control groups in the degree of locomotor recovery. Our results confirm the previous report that NSC transplants can fill lesion cavities and robustly extend axons, but reveal that most grafts do not create a continuous bridge of neural tissue between rostral and caudal segments.

Comparison of Pulpal Responses to Pulpotomy and Pulp Capping with Biodentine and Mineral Trioxide Aggregate in Dogs

IntroductionThis study evaluated the pulpal and periapical responses of dogs' teeth after pulpotomy and pulp capping with a new tricalcium silicate–based cement (Biodentine) when compared with mineral trioxide aggregate (MTA) by radiographic, histopathologic, and histomicrobiological analyses. MethodsSixty roots (30 teeth) of dogs were divided into 2 groups, Biodentine (n = 36 roots) and ProRoot MTA (control, n = 24 roots). Animals were killed after 120 days, and the teeth were subjected to histotechnical processing (hematoxylin-eosin and Brown and Brenn staining). Qualitative and quantitative histopathologic data were analyzed by Fisher exact and Mann-Whitney tests (α = 0.05). ResultsRadiographically, mineralized tissue bridge formation was observed in more specimens treated with Biodentine (96.8%) than with MTA (72.2%) (P = .02). Integrity of the lamina dura and absence of periapical bone rarefaction and root resorption (external and internal) were observed in all specimens. Histopathologic and histomicrobiological analyses revealed mineralized tissue bridge formation, pulpal vitality, odontoblast layer integrity, preserved periodontal ligament, and absence of bone or root resorption and microorganisms in both groups. Although the bridges formed at the amputation site had similar morphology, they were significantly thicker in the Biodentine group (P < .0001). Comparison between the radiographic and histopathologic results showed that radiographic visualization of more bridges in the Biodentine group was related to bridge thickness because radiographic diagnosis was flawed for bridges with thickness less than 0.5 mm. Fluorescence microscopy improved the visualization of bridge structure. ConclusionsBiodentine presented tissue compatibility and allowed for mineralized tissue bridge formation after pulpotomy in all specimens with similar morphology and integrity to those formed with use of MTA. Periapical radiographs failed in detecting mineralized tissue bridges with thickness less than 0.5 mm.

Comparison of pulp response to mineral trioxide aggregate and a bioceramic paste in partial pulpotomy of sound human premolars: a randomized controlled trial

This randomized clinical trial evaluated clinical sign/symptoms as well as histological pulp reactions in terms of inflammation and mineralized bridge formation after partial pulpotomy of sound human premolars and placement of a bioceramic paste (iRoot BP) or tooth-colored ProRoot MTA as pulp-covering biomaterials. Twenty-four human sound premolars were randomly allocated into two experimental groups (n = 12) treated either with iRoot BP or MTA subsequent to partial pulpotomy. Six weeks after treatment, clinical sign/symptoms and radiographic changes were evaluated. The teeth were then extracted and examined histologically for inflammatory status of the pulp, formation of hard tissue bridge and appearance of the bridge. In terms of pulp inflammation and dentinal bridge formation, the Mann-Whitney U, and for clinical signs, the chi-square test was used (α = 0.05). In terms of pulp inflammation, formation of hard tissue bridge and its appearance, the differences between the two experimental groups were not significant. However, clinical sensitivity to cold was significantly less for teeth treated with MTA (P < 0.05). All cases had formed a hard tissue bridge, and none of the specimens in either group had pulpal necrosis. When treating teeth with healthy pulps, the response to partial pulpotomy treatment with both MTA and iRoot BP was favourable. However, pulps covered with iRoot BP were more sensitive to cold stimuli.

Transplanting neural progenitors to build a neuronal relay across the injured spinal cord.

Cellular transplantation for repair of spinal cord injury is a promising therapeutic strategy that includes the use of a variety of neural and non-neural cells isolated or derived from embryonic and adult tissue as well as embryonic stem cells and induced pluripotent stem cells. In particular, transplants of neural progenitor cells (NPCs) have been shown to limit secondary injury and scar formation and create a permissive environment in the injured spinal cord through the provision of neurotrophic molecules and growth supporting matrices that promote growth of injured host axons. Importantly, transplants of NPC are unique in their potential to replace lost neural cells – including neurons, astrocytes, and oligodendrocytes – critical for reconstruction of the normal microenvironment of the spinal cord and restoration of connectivity and function. Different NPC preparations have been used for transplantation experiments in multiple, diverse models of SCI, ranging from the classical work with fetal spinal cord (FSC) that defined the optimal age for donor tissue and its capacity to generate neural cells (Reier et al., 1983; Reier et al., 1986), to studies that demonstrated the formation of a neuronal relay by NPC transplants across the injured spinal cord to reconnect the interrupted sensory system (Bonner et al., 2011). At the developmental stage of embryonic day (E)13.5–14 the FSC is composed primarily of neuronal restricted progenitors (NRP) and glial restricted progenitors (GRP), but also contains a small number of immature neural stem cells, neurons, endothelial cells and fibroblasts (Kalyani et al., 1998; Cai et al., 2002; Lepore and Fischer, 2005; Medalha et al., 2014). While grafts of acutely isolated FSC contain all of these cell subpopulations, the process of isolating and culturing of NRP and GRP from FSC, particularly by adherent, sub-confluent culture on a poly-L-lysine/laminin substrate generates pure, defined, and reproducible populations of progenitors (Cai et al., 2002) for cryopreservation or transplantation experiments. NRP and GRP, in contrast to multipotent NSC have a capacity for self-renewal and a restricted differentiation potential, as they are committed to neuronal and glial phenotypes, respectively (Han et al., 2002; Lepore and Fischer, 2005). The injured spinal cord, however, presents a variety of impediments not only to the regeneration of injured host axons in the form of chondroitin sulfated proteoglycans (CSPG) and myelin-associated byproducts, but also significantly limits the survival and differentiation of graft-derived neurons (Cao et al., 2002; Lepore and Fischer, 2005).

English

The thyroid gland is brownish-red and highly vascular gland which is placed anteriorly in the neck at the level of fifth cervical to the first thoracic vertebrae and is covered by the pre- tracheal layer of the deep cervical fascia. It has two lateral lobes which are connected by a narrow median isthmus giving an 'H' shaped appearance to the gland. Congenital malformations and morphological variations of the thyroid gland are commonly reported in literature which has numerous clinical and surgical implications. In this case absence of isthmus was observed during routine dissection of a 60 yrs old male cadaver. The lateral lobes were positioned normally and a pyramidal lobe attached to the left lobe was seen. Moreover levator glandulae thyroideae extending from the hyoid bone to the apex of the pyramidal lobe was also observed. Agenesis of isthmus or presence of pyramidal lobe usually has no impact on thyroid functions and can be diagnosed by scintigraphy, ultrasonography, CT scan and MRI. However if the diagnoses is made during routine imaging or accidently, the patient must be thoroughly screened for other associated thyroid anomalies like autonomous thyroid nodule, thyroiditis, primary carcinoma, infiltrative diseases like amyloidoses etc. INTRODUCTION: The thyroid gland, brownish-red and highly vascular, is a palpable endocrine gland placed anteriorly in the neck and its position extends from the fifth cervical to the first thoracic vertebrae. It is covered by the pre-tracheal layer of deep cervical fascia. The two lobes are connected by a narrow median isthmus. The normal size of each lobe of the thyroid gland has been described to be 5 cm long, its greatest transverse and antero-posterior extent being 3 cm and 2 cm respectively. The isthmus measures about 1.25 cm transversely as well as vertically and is usually placed anterior to the second and third tracheal cartilages1. The anomalies of the development of the thyroid gland distort the morphology of the gland, and may cause clinical functional disorders and various thyroid illnesses 2 . Besides, such anomalies can pose diagnostic and surgical challenges in addition to non-invasive and invasive airway management during emergency and surgical interventions3. The incidence of isthmus agenesis varies from 5-10%4. This absence can be explained as an anomaly of embryological development and can be associated with other types of dys- organogenesis, such as the absence of a lobe or the presence of ectopic thyroid tissue. Phylo- genetically, in some species in which the thyroid follicles are organized in a gland, this gland can acquire a bi-lobed shape, in which the lobes join together in front of the upper part of the trachea by an isthmus or bridge of thyroid tissue. The isthmus may be missing, as happens in amphibians, birds and among the mammals, in the monotrema, certain marsupials, cetaceans, carnivores and rodents.