A prospective study of magnetic resonance imaging patterns of central nervous system infections in pediatric age group and young adults and their clinico-biochemical correlation

Background:

Infections of the central nervous system (CNS) are common and routinely encountered. Our aim was to evaluate the neuroimaging features of the various infections of the CNS so as to differentiate them from tumoral, vascular, and other entities that warrant a different line of therapy.

Aims:

Our aim was to analyze the biochemical and magnetic resonance imaging (MRI) features in CNS infections.

Settings and Design:

This was a longitudinal, prospective study over a period of 1½ years.

Subjects and Methods:

We studied cerebrospinal fluid (CSF) findings and MRI patterns in 27 patients of 0–20 years age group with clinical features of CNS infections. MRI was performed on MAGNETOM Avanto 18 Channel 1.5 Tesla MR machine by Siemens India Ltd. The MRI protocol consisted of diffusion-weighted and apparent diffusion coefficient imaging, turbo spin echo T2-weighted, spin echo T1-weighted, fluid-attenuated inversion recovery (FLAIR), and gradient-echo in axial, FLAIR in coronal, and T2-weighted in sagittal plane. Contrast-enhanced T1-weighted sequence and MR spectroscopy were done whenever indicated.

Results and Conclusions:

We found that most of the children belong to 1–10 years age group. Fungal infections were uncommon, mean CSF adenosine deaminase values specific for tuberculosis and mean CSF glucose-lowered in pyogenic. Hemorrhagic involvement of thalamus with/without basal ganglia and brainstem involvement may indicate Japanese encephalitis or dengue encephalitis. Diffusion restriction or hemorrhage in not expected in the brainstem afflicted lesions of rabies. Congenital cytomegalovirus can cause cortical malformations. T1 hyperintensities with diffusion restriction may represent viral encephalitis. Lesions of acute disseminated encephalomyelitis (ADEM) may mimic viral encephalitis. Leptomeningeal enhancement is predominant in pyogenic meningitis. Basilar meningitis in the presence of tuberculomas is highly sensitive and specific for tuberculosis.

Nerve growth factor injected into the gastric ulcer base incorporates into endothelial, neuronal, glial and epithelial cells: implications for angiogenesis, mucosal regeneration and ulcer healing

A previous study has demonstrated that locally administered growth factors such as epidermal growth factor, basic fibroblast growth factor and hepatocyte growth factor can accelerate healing of experimental gastric ulcers in rats. That study indicates that locally administered growth factors can exert potent biological effects resulting in enhanced gastric ulcers healing. However, the fate of injected growth factors, their retention and localization to specific cellular compartments have not been examined. In our preliminary study, we demonstrated that local injection of nerve growth factor to the base of experimental gastric ulcers dramatically accelerates ulcer healing, increases angiogenesis - new blood vessel formation, and improves the quality of vascular and epithelial regeneration. Before embarking on larger, definitive and time sequence studies, we wished to determine whether locally injected nerve growth factor is retained in gastric ulcer's tissues and taken up by specific cells during gastric ulcer healing. Gastric ulcers were induced in anesthetized rats by local application of acetic acid using standard methods; and, 60 min later fluorescein isothiocyanate-labeled nerve growth factor was injected locally to the ulcer base. Rats were euthanized 2, 5 and 10 days later. Gastric specimens were obtained and processed for histology. Unstained paraffin sections were examined under a fluorescence microscope, and the incorporation of fluorescein isothiocyanate-labeled nerve growth factor into various gastric tissue cells was determined and quantified. In addition, we performed immunostaining for S100β protein that is expressed in neural components. Five and ten days after ulcer induction labeled nerve growth factor (injected to the gastric ulcer base) was incorporated into endothelial cells of blood vessels, neuronal, glial and epithelial cells, myofibroblasts and muscle cells. This study demonstrates for the first time that during gastric ulcer healing locally administered exogenous nerve growth factor is retained in gastric tissue and is taken up by endothelial, neural, muscle and epithelial cells. This is likely the basis for the therapeutic action of locally administered nerve growth factor and its stimulation of angiogenesis, tissue regeneration and gastric ulcer healing.

Bilateral optic nerve infarction in rhino-cerebral mucormycosis: A rare magnetic resonance imaging finding

Mucormycosis is an emerging disease in diabetes and immunocompromised patients. Rhino-orbito-cerebral mucormycosis is one of the common forms of the disease. Mucormycosis leading to ischemic optic neuropathy is a rare complication. The role of magnetic resonance imaging (MRI) in the diagnosis of ischemic optic neuropathy is limited and uncommonly reported. We report an unusual case of mucormycosis in which MRI revealed bilateral optic nerve infarction, in addition to perineural extension of the fungus along the trigeminal nerve, another uncommon imaging finding.

The nano-epsilon dot method for strain rate viscoelastic characterisation of soft biomaterials by spherical nano-indentation

Nano-indentation is widely used for probing the micromechanical properties of materials. Based on the indentation of surfaces using probes with a well-defined geometry, the elastic and viscoelastic constants of materials can be determined by relating indenter geometry and measured load and displacement to parameters which represent stress and deformation. Here we describe a method to derive the viscoelastic properties of soft hydrated materials at the micro-scale using constant strain rates and stress-free initial conditions. Using a new self-consistent definition of indentation stress and strain and corresponding unique depth-independent expression for indentation strain rate, the epsilon dot method, which is suitable for bulk compression testing, is transformed to nano-indentation. We demonstrate how two materials can be tested with a displacement controlled commercial nano-indentor using the nano-espilon dot method (nano-ε̇M) to give values of instantaneous and equilibrium elastic moduli and time constants with high precision. As samples are tested in stress-free initial conditions, the nano-ε̇M could be useful for characterising the micro-mechanical behaviour of soft materials such as hydrogels and biological tissues at cell length scales.

Expression of nerve growth factor, its TrkA receptor, and several neuropeptides in porcine esophagus. Implications for interactions between neural, vascular and epithelial components of the esophagus

This study was aimed to determine the expression and localization of nerve growth factor (NGF) and several neural peptides in porcine esophagus. Transmural esophageal specimens were obtained from euthanized pigs.

STUDIES

1) histologic evaluation, 2) expressions of NGF and its tropomyosin receptor kinase A (TrkA) receptor, calcitonin generelated peptide (CGRP), neuronal nitric oxide synthase (nNOS), and neuronal enolase using immunostaining and quantification of signal distribution and intensity. Immunostaining for NGF, CGRP, nNOS and neuronal specific enolase (NSE) showed their strong and differential expression and localization in the neuronal network. NGF was strongly expressed in the majority of neurons and nerves, distribution of TrkA was complementary; its signal was 1.5-fold weaker P < 0.001 than NGF). Quantitatively the signal intensity was: CGRP > nNOS > NGF > NES > TrkA. In addition to neural structures, nNOS, NGF and TrkA were expressed in keratinocyte progenitor cells of esophageal mucosa and in endothelial cells of blood vessels. We conclude that a strong expression of NGF in majority of esophageal neurons and nerves indicates important, but previously unrecognized regulatory roles in the esophagus; 2) This study showed expression of NGF and some of the neuropeptides in neural elements, keratinocyte progenitor cells and endothelial cells of blood vessels, which indicates local interactions between neural, epithelial and endothelial cells.

Profile analysis of hepatic porcine and murine brain tissue slices obtained with a vibratome

This study is aimed at characterizing soft tissue slices using a vibratome. In particular, the effect of two sectioning parameters (i.e., step size and sectioning speed) on resultant slice thickness was investigated for fresh porcine liver as well as for paraformaldehyde-fixed (PFA-fixed) and fresh murine brain. A simple framework for embedding, sectioning and imaging the slices was established to derive their thickness, which was evaluated through a purposely developed graphical user interface. Sectioning speed and step size had little effect on the thickness of fresh liver slices. Conversely, the thickness of PFA-fixed murine brain slices was found to be dependent on the step size, but not on the sectioning speed. In view of these results, fresh brain tissue was sliced varying the step size only, which was found to have a significant effect on resultant slice thickness. Although precision-cut slices (i.e., with regular thickness) were obtained for all the tissues, slice accuracy (defined as the match between the nominal step size chosen and the actual slice thickness obtained) was found to increase with tissue stiffness from fresh liver to PFA-fixed brain. This quantitative investigation can be very helpful for establishing the most suitable slicing setup for a given tissue.

Abdominal splenosis mimicking peritoneal deposits - A case report

Splenosis is a benign condition among patients with a history of splenic trauma or surgery. Most cases of splenosis are intra abdominal due to direct seeding of surrounding structures, although these heterotopic rests may occur almost anywhere in the body, and its diffuse nature may raise the suspicion of metastatic cancer. The increased prevalence of abdominal trauma due to road accidents and the growing armamentarium of available imaging modalities suggest that abdominal splenosis may be expected more often than ever. We, in this article emphasize the crucial role of taking a thorough patient's medical history concerning splenic trauma in the past and the use of novel non invasive diagnostics modalities that allow accurate diagnosis.

Sphyga: a multiparameter open source tool for fabricating smart and tunable hydrogel microbeads

Hydrogel microbeads are used in many biological applications, particularly for cell, protein or drug encapsulation. Although there are several methods for fabricating microbeads with controlled shapes and dimensions, many are limited to a small range of materials or sizes. We describe a compact open source tool-the spherical hydrogel generator (Sphyga)-for the fabrication of highly reproducible hydrogel based microbeads with predictable shapes and diameters ranging from 100 to 2000 µm. The unique feature of the system is the ability to modulate multiple parameters independently, so as to create a wide range of working conditions for fabricating tailored microbeads. Hence, by combining the different fabrication parameters, hydrogel beads with chosen shapes, sizes and materials can be generated with Sphyga. A multiparameter working-window was obtained by fixing the concentration of the base material, alginate, and varying the viscosity of the solution along with Sphyga's fabrication parameters (needle size, external air pressure, and material outflow). To validate the multiparameter working window, components such as proteins, cells, dyes and nanoparticles were also used to fabricate composite microbeads. The results show that the architecture of hydrogel microbeads can be engineered by considering the viscosity of the initial solution, which depends principally on the pH and composition of alginate solution. Coupled with Sphyga's multiple working parameters, material viscosity can then be used to tune hydrogel domains and thereby generate complex biologically relevant microenvironments for many biomedical applications.

Aging impairs transcriptional regulation of vascular endothelial growth factor in human microvascular endothelial cells: implications for angiogenesis and cell survival

In some tissues, aging impairs angiogenesis and reduces expression of vascular endothelial growth factor A (VEGF), a fundamental regulator of angiogenesis. We previously examined angiogenesis in aging and young gastric mucosa in vivo and in vitro and showed that an imbalance between expressions of VEGF (pro-angiogenic factor) and endostatin (anti-angiogenic protein) results in an aging-related impairment of angiogenesis in rats. However, the human relevance of these findings, and whether these mechanisms apply to endothelial cells derived from other tissues, is not clear. Since P-STAT3 and P-CREB are transcription factors that, in association with HIF-1α, can activate VEGF gene expression in some cells (e.g., liver cancer cells, vascular smooth muscle cells), we examined the expression of these two proteins in human dermal microvascular endothelial cells (HMVECs) derived from aging and neonatal individuals. We examined and quantified in vitro angiogenesis, expression of VEGF, P-STAT3, P-CREB and importin-α in HMVECs isolated from neonates (neonatal) and a 66 year old subject (aging). We also examined the effects of treatment with exogenous VEGF and endostatin on in vitro angiogenesis in these cells. Endothelial cells isolated from aging individuals had impaired angiogenesis (vs. neonatal endothelial cells) and reduced expression of VEGF mRNA and protein. Aged HMVECs also had reduced importin-α expression, and reduced expression and nuclear translocation of P-STAT3 and P-CREB. Reduced VEGF gene expression in aged HMVECs strongly correlated with the decreased levels of P-STAT3, P-CREB and importin-α in these cells. Our study clearly demonstrates that endothelial cells from aging individuals have impaired angiogenesis and reduced expression of VEGF likely due to impaired nuclear transport of P-STAT3 and P-CREB transcription factors in these cells.

Strain rate viscoelastic analysis of soft and highly hydrated biomaterials

Measuring the viscoelastic behavior of highly hydrated biological materials is challenging because of their intrinsic softness and labile nature. In these materials, it is difficult to avoid prestress and therefore to establish precise initial stress and strain conditions for lumped parameter estimation using creep or stress-relaxation (SR) tests. We describe a method ( ɛ˙M or epsilon dot method) for deriving the viscoelastic parameters of soft hydrated biomaterials which avoids prestress and can be used to rapidly test degradable samples. Standard mechanical tests are first performed compressing samples using different strain rates. The dataset obtained is then analyzed to mathematically derive the material's viscoelastic parameters. In this work a stable elastomer, polydimethylsiloxane, and a labile hydrogel, gelatin, were first tested using the ɛ˙M, in parallel SR was used to compare lumped parameter estimation. After demonstrating that the elastic parameters are equivalent and that the estimation of short-time constants is more precise using the proposed method, the viscoelastic behavior of porcine liver was investigated using this approach. The results show that the constitutive parameters of hepatic tissue can be quickly quantified without the application of any prestress and before the onset of time-dependent degradation phenomena.

The safety and efficacy of intracoronary nitrite infusion during acute myocardial infarction (NITRITE-AMI): study protocol of a randomised controlled trial

INTRODUCTION

Acute myocardial infarction (AMI) is a major cause of death and disability in the UK and worldwide. Presently, timely and effective reperfusion with primary percutaneous coronary intervention (PPCI) remains the most effective treatment strategy for limiting infarct size, preserving left ventricular ejection fraction (LVEF) and improving clinical outcomes. However, the process of reperfusion can itself induce cardiomyocyte death, known as myocardial reperfusion injury, for which there is currently no effective therapy. Extensive preclinical evidence exists to suggest that sodium nitrite (as a source of endogenous nitric oxide) is an effective therapeutic strategy for preventing myocardial reperfusion injury. The purpose of NITRITE-AMI is to test whether sodium nitrite reduces reperfusion injury and subsequent infarct size in patients undergoing PPCI for MI.

METHODS AND DESIGN

NITRITE-AMI is a double-blind, randomised, single-centre, placebo-controlled trial to determine whether intracoronary nitrite injection reduces infarct size in patients with myocardial infarction undergoing primary angioplasty. The study will enrol 80 patients presenting with ST-elevation myocardial infarction. Patients will be randomised to receive either a bolus of intracoronary sodium nitrite or placebo (sodium chloride) at the time of PPCI. The primary outcome is infarct size assessed by creatine kinase area under the curve (AUC) over 48 h. Secondary endpoints include troponin T AUC and infarct size, LV dimensions and myocardial salvage index assessed by cardiac MR (CMR), markers of platelet reactivity and inflammation, the safety and tolerability of intracoronary nitrite, and 1 year major adverse cardiac events.

ETHICS AND DISSEMINATION

The study is approved by the local ethics committee (NRES Committee London West London: 11/LO/1500) and by the Medicines and Healthcare Products Regulatory Agency (MHRA) (EudraCT nr. 2010-022460-12). The results of the trial will be published according to the CONSORT statement and will be presented at conferences and reported in peer-reviewed journals.

TRIAL REGISTRATION

United Kingdom Clinical Research Network (Study ID 12117), http://clinicaltrials.gov (NCT01584453) and Current Controlled Trials (ISRCTN:38736987).

In vivo visualization of epidermal growth factor receptor and survivin expression in porcine pancreas using endoscopic ultrasound guided fine needle imaging with confocal laser-induced endomicroscopy

The aims of this pilot study were to establish a principle of molecular imaging of the pancreas and determine in vivo expression of epidermal growth factor receptor (EGF-R) and survivin using a novel endoscopic ultrasound-guided fine needle imaging (EUS-FNI) technique, which incorporates needle based confocal laser-induced endomicroscopy (nCLE) after intrapancreatic injection of FTIC-labeled antibodies. Studies were performed in anesthetized pigs. FITC-labeled specific antibodies against EGF-R and survivin were injected into the tail and neck of the pancreas using a 19 gauge needle introduced under EUS guidance. Thirty minutes later, nCLE was performed using a prototype needle-based confocal laser-induced endomicroscopy probe (Cellvizio AQ-Flex-19, Mauna Kea Technologies, Paris, France) to determine cellular and tissue localization of EGF-R and survivin in the pancreas. Then pigs were euthanized and specimens of pancreas from areas injected with antibodies were obtained for histologic examination under epifluorescence microscope.

RESULTS

EUS-guided nCLE enabled visualization of EGF-R and survivin in pancreatic tissue. Expression of EGF-R and survivin in pancreas was confirmed by histology. EGF-R immunoreactivity was localized to majority of duct-lining cells and to the surface and cytoplasm of many acinar cells. Survivin was localized mainly to the acinar cells. This study demonstrated the feasibility of in vivo, real time visualization of EGF-R and survivin in the pancreas by local injection of FITC-labeled antibodies via EUS-guided fine needle injection, followed by EUS-guided needle based confocal laser-induced endomicroscopy.

Aicardi syndrome

Aicardi syndrome is a rare neurodevelopmental disease characterised by congenital chorioretinal lacunae, corpus callosum dysgenesis, seizures, polymicrogyria, cerebral callosum, chorioretinopathy and electroencephalogram abnormality. We present a case of Aicardi syndrome with callosal hypogenesis in a 4.5-month-old baby who presented with infantile spasms. Ophthalmoscopy revealed chorioretinal lacunae. The clinical and magnetic resonance imaging features were diagnostic of Aicardi syndrome.

Molecular imaging of epidermal growth factor-receptor and survivin in vivo in porcine esophageal and gastric mucosae using probe-based confocal laser-induced endomicroscopy: proof of concept

Confocal laser-induced endomicroscopy (CLE) enables in vivo, real time visualization of the subsurface cells and tissue structures in gastrointestinal mucosa at a subcellular resolution of ≈1000x magnification. The aims of this pilot study were to establish a principle of molecular imaging and determine in vivo expression of epidermal growth factor receptor (EGF-R) and survivin in porcine esophageal and gastric mucosa using probe-based CLE (pCLE) and topically applied FITC-labeled antibodies. Studies were performed in anesthetized pigs. During endoscopy FITC-labeled antibodies against EGF-R and survivin were either sprayed onto esophageal and gastric mucosa in preselected areas or administered via submucosal injection. Thirty minutes later pCLE was performed using a through-the-scope probe (GastroFlex UHD, Cellvizio, Mauna Kea Technologies, Paris, France) to determine cellular and tissue localization of EGF-R and survivin. Then the pigs were euthanized and esophageal and gastric walls from the areas sprayed or injected with antibodies were collected for histologic examination under epifluorescence microscopy.

RESULTS

CLE enabled visualization of EGF-R and survivin in esophageal and gastric mucosa and this was confirmed by histology. In the esophagus both EGF-R and survivin were localized predominantly to the keratinocyte progenitor cells. In the stomach, EGF-R was localized to progenitor zone cells and some epithelial cells. Localization of survivin was similar, but involved more surface epithelial cells. This study demonstrated feasibility of using CLE and topical administration of FITC labeled antibodies for in vivo localization of EGF-R and survivin in esophageal and gastric mucosa.

Endothelial cell function on 2D and 3D micro-fabricated polymer scaffolds: applications in cardiovascular tissue engineering

Polymeric structures of a polylactide-polycaprolactone blend were micro-fabricated using the Pressure Assisted Microsyringe (PAM) system. Human umbilical vein endothelial cells were cultured on the scaffolds, and apoptosis, cell adhesion, proliferation and metabolism were evaluated. In addition, more specific indicators of endothelial cell function, namely nitric oxide and endothelin production, were also assessed. Thin films of the blend, as well as gelatine-coated glass slides (as controls) were used. The results show that as far as adhesion, apoptosis and metabolism are concerned, the scaffolds do not interfere with cell function compared with gelatin controls. However, the nitric oxide/endothelin ratio was higher than that observed on the gelatin films, suggesting that the scaffolds could be used for engineering small diameter blood vessels without risk of occlusion.

Colonic mucosal biopsies obtained during confocal endomicroscopy are pre-stained with fluorescein in vivo and are suitable for histologic evaluation

BACKGROUND AND STUDY AIMS

Confocal laser endomicroscopy (CLE) with intravenous infusion of fluorescein allows noninvasive, real-time in vivo visualization of gastrointestinal mucosa at ~ × 1000 magnification ("virtual biopsy"). Conventional biopsies obtained during these procedures serve as the reference and established diagnostic standard. The aim of the present study was to assess whether the standard histologic biopsies that are obtained during CLE retain fluorescein in the tissues and allow the visualization of mucosal structures without any additional staining.

PATIENTS AND METHODS

CLE optical imaging of the mucosa was performed in 16 patients who were undergoing CLE colonoscopy. Standard conventional biopsies were also obtained from both normal colonic mucosa and colonic polyps. De-paraffinized mucosal sections were examined under a fluorescence microscope for the presence and distribution of fluorescein, and then underwent immunostaining for expression of vascular endothelial growth factor (VEGF).

RESULTS

Standard mucosal biopsy sections from patients undergoing CLE displayed a strong fluorescence and showed well-delineated mucosal structures. In colonic adenomas, there was a 4.6-fold increased vascular permeability compared with normal mucosa (P<0.001), indicated by fluorescein leakage to the extravascular space. Immunostaining demonstrated an aberrantly increased expression of VEGF in the epithelium of colonic adenomas but not in the epithelium of normal mucosa or hyperplastic polyps.

CONCLUSIONS

This study shows for the first time that standard colonic biopsies obtained during CLE retain fluorescein, show excellent delineation of mucosal structures without additional staining, allow the evaluation of mucosal microvasculature and vascular permeability, and are suitable for immunostaining.

Critical role of hypoxia sensor--HIF-1α in VEGF gene activation. Implications for angiogenesis and tissue injury healing

Vascular injury of esophageal and gastrointestinal mucosa caused by injurious and ulcerogenic factors leads to the cessation of blood flow, ischemia, and hypoxia and tissue necrosis in form of erosions or ulcers. The re-establishment of blood vessels through the process of angiogenesis--formation of new blood vessels--is critical for healing of tissue injury because is essential for delivery of oxygen and nutrients to the healing site. Hypoxia increases expression of hypoxia inducible factor (HIF-1), which serves as hypoxia sensor and activates compensatory and adaptive mechanisms. However, the molecular mechanisms and the role of HIF-1α in hypoxia-driven cellular and molecular events of angiogenesis in gastrointestinal injury healing have not been fully explored. The review discusses the novel molecular mechanisms of angiogenesis in gastric and esophageal mucosa with focus on HIF1α and VEGF interactions during healing of gastric mucosal injury and esophageal ulcers. HIF-1α is upregulated by gastric mucosal injury and esophageal ulcers; this upregulation correlates with VEGF gene activation and initiation of angiogenesis. The non-steroidal anti-inflammatory drugs (NSAIDs) interfere with hypoxia-induced HIF-1α accumulation, VEGF gene activation and angiogenesis through upregulation of von Hippel- Lindau (VHL) tumor suppressor, which activates degradation of HIF-1α protein. HIF-1α is a transcription factor that under hypoxic conditions, accumulates in endothelial cells and can bind to VEGF gene promoter and induce VEGF gene expression. In order to activate the VEGF gene, HIF-1α must be transported to the nucleus. Recent evidence implicates importins as key mechanism in this process.

Molecular mechanisms of epithelial regeneration and neovascularization during healing of gastric and esophageal ulcers

In this paper we reviewed and updated current views on the cellular and molecular mechanisms of gastric and esophageal ulcer healing. Gastric ulcer healing encompasses inflammation, cell proliferation, epithelial regeneration, gland reconstruction, formation of granulation tissue, neovascularization (new blood vessel formation), interactions between various cells and the matrix and tissue remodeling, resulting in scar formation. All these events are controlled by the cytokines and growth factors, GI hormones including gastrin, CCK, and orexigenic peptides such as ghrelin, orexin-A and obestatin as well as Cox2 generated prostaglandins. These growth factors and hormones trigger cell proliferation, migration, and survival utilizing Ras, MAPK, PI-3K/AKT, PLC-γ and Rho/Rac/actin signaling pathways. Hypoxia triggers activation of some of these genes (e.g., VEGF) via hypoxia inducible factor (HIF). Growth factors: EGF, HGF, IGF-1, their receptors and Cox2 are important for epithelial cell proliferation, migration, re-epithelialization and regeneration of gastric glands during gastric ulcer healing. Serum response factor (SRF) is also essential for re-epithelialization and muscle restoration. VEGF, bFGF, angiopoietins, nitric oxide, endothelin, prostaglandins and metalloproteinases are important for angiogenesis, vascular remodeling and mucosal regeneration within gastric ulcer scar. SRF is critical limiting factor for VEGF-induced angiogenesis. Esophageal ulcer healing follows similar pattern to gastric ulcer, but KGF and its receptor are the key players in regeneration of the epithelium. In addition to local mucosal cells from viable mucosa bordering necrosis, circulating bone marrow derived stem and progenitor cells are potentially important for ulcer healing, contributing to the regeneration of epithelial and connective tissue components and neovascularization.