Volker Tronnier

Basic fibroblast growth factor: a potential new therapeutic tool for the treatment of hypertrophic and keloid scars.

Numerous tissue niches in the human body, such as skin, are now recognized to harbour adult stem cells. In this study, we analyze multipotent human dermis-derived progenitor cell populations, isolated and propagated from mechanically and enzymatically processed adult scalp skin. The populations encompass Nestin-positive and -negative cells, which may serve as a convenient and abundant source for various therapeutic applications in regenerative medicine. Here, we show that these cultures exhibit a strong tendency to differentiate into mesodermal derivatives, particularly myofibroblasts, when maintained in media containing serum. Since undesired and excessive myofibroblast formation is a frequent postsurgical complication, we sought culture conditions that would prevent myofibroblast formation. In particular, we analyzed the effect of growth factors, such as epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and platelet-derived growth factor AB (PDGF AB). Our results demonstrate that bFGF is a potent inhibitor of mesodermal differentiation, whereas PDFG AB favours myofibroblast formation and up-regulates expression of TGFbeta receptors I and II. This interesting discovery may help in the prevention and treatment of tissue fibrosis and in particular in the eradication of hypertrophic and keloid scars.

Imaging of brain and brain tumor specimens by time-resolved multiphoton excitation microscopy ex vivo.

Multiphoton excitation fluorescent microscopy is a laser-based technology that allows subcellular resolution of native tissues in situ. We have recently applied this technology to the structural and photochemical imaging of cultured glioma cells and experimental gliomas ex vivo. We demonstrated that high microanatomical definition of the tumor, invasion zone, and normal adjacent brain can be obtained down to single-cell resolution in unprocessed tissue blocks. In this study, we used multiphoton excitation and four-dimensional microscopy to generate fluorescence lifetime maps of the murine brain anatomy, experimental glioma tissue, and biopsy specimens of human glial tumors. In murine brain, cellular and noncellular elements of the normal anatomy were identified. Distinct excitation profiles and lifetimes of endogenous fluorophores were identified for specific brain regions. Intracranial grafts of human glioma cell lines in mouse brain were used to study the excitation profiles and fluorescence lifetimes of tumor cells and adjacent host brain. These studies demonstrated that normal brain and tumor could be distinguished on the basis of fluorescence intensity and fluorescence lifetime profiles. Human brain specimens and brain tumor biopsies were also analyzed by multiphoton microscopy, which demonstrated distinct excitation and lifetime profiles in glioma specimens and tumor-adjacent brain. This study demonstrates that multiphoton excitation of autofluorescence can distinguish tumor tissue and normal brain based on the intensity and lifetime of fluorescence. Further technical developments in this technology may provide a means for in situ tissue analysis, which might be used to detect residual tumor at the resection edge.

The role of postoperative radiotherapy for the treatment of gangliogliomas

Because of their rarity, no prospective studies have been performed regarding gangliogliomas. The optimal treatment regimen is unclear. In this study, the authors compared 4 therapies for local control (LC) and overall survival (OS) in patients with ganglioglioma.

High-frequency electrical stimulation suppresses cholinergic accumbens interneurons in acute rat brain slices through GABAB receptors

The nucleus accumbens is selected as a surgical target in deep brain stimulation for treating refractory obsessive‐compulsive disorder (OCD). One of the therapeutic benefits of this procedure is that the abnormal hyper‐functioning prefrontal cortex of patients with OCD is restored during stimulation. One hypothesis regarding the mechanism of deep brain stimulation is that the neuronal electrophysiological properties are directly altered by electrical stimulation; another hypothesis assumes that the stimulation induces selective neuron transmitter release, such as γ‐aminobutyric acid (GABA). In this study, we used multi‐electrode arrays with electrode size of 40 × 40 μm to record electrophysiological signals from the large nucleus accumbens neurons in acute rat brain slices while applying electrical stimulation simultaneously. We revealed that high‐frequency stimulation (HFS, 140 Hz) suppressed the spontaneous neuronal firing rate significantly, whereas low‐frequency stimulation (LFS, 10 Hz) did not. Both HFS and LFS have no effect on neuronal firing pattern or on neuronal oscillation synchrony. GABAB receptor antagonism reversed the HFS‐provoked neuronal inhibition, whereas GABAA receptor blockade failed to affect it. The recorded neurons were pharmacologically identified to be cholinergic interneurons. We propose that HFS has a direct suppressive effect on the identified accumbal acetylcholine (ACh) interneurons by enhancing GABA release in the stimulated region. Potentially, suppressed ACh interneurons decrease the disinhibiting function of medium‐sized spiny neurons in the striato‐thalamo‐cortical circuit. This finding might give an indication of the mechanism of the therapeutic effect of HFS in nucleus accumbens on restoring the abnormal hyperactive prefrontal cortex status in OCD.

Impact of percutaneous dilatational tracheostomy in brain injured patients

OBJECTIVEnTracheostomy is an established method in the airway management of critically ill patients with traumatic and non-traumatic brain injuries. High priority in the treatment of those patients is to protect vulnerable brain tissue. While bedside percutaneously dilatative tracheostomy (PDT) technique is increasingly used, there is disagreement about the harms of this intervention for the damaged brain. Therefore, discussions about the safety of tracheostomy in those patients must consider direct and indirect cerebral parameters.nnnMETHODSnWe examined a series of 289 tracheostomies regarding vital signs, respiratory and intracranial parameters in a retrospective study. Complications were recorded and risk factors for a complicated scenario statistically determined.nnnRESULTSnSevere complications were rare (1/289). Arterial hypotension occurred in 3 of 289 cases with a systolic blood pressure below 90mmHg. We had two patients (0.5%) with transient hypoxia, but 43 cases (15%) of severe hypercapnia during PDT. Invasive measurement of brain tissue oxygen tension (PBrO2) ruled out any cerebral hypoxia during the procedure in 39 available cases. Intracranial pressure (ICP) rose temporarily in 24% of the cases. Cerebral perfusion pressure (CPP) however remained unaffected. Surgery time and hypercapnia are capable risk factors for intraoperative ICP elevation. There is no significant difference in intraoperative ICP rises between disease entities.nnnCONCLUSIONnPDT is a safe procedure for the most common neurosurgical diseases, even for patients with respiratory insufficiency. Shortening surgical time seems to be the most important factor to avoid ICP increase.

An improved, standardised protocol for the isolation, enrichment and targeted neural differentiation of Nestin+ progenitors from adult human dermis

Please cite this paper as: An improved, standardised protocol for the isolation, enrichment and targeted neural differentiation of Nestin+ progenitors from adult human dermis. Experimental Dermatology 2010; 19: 549–555.

Coronal in vivo forward-imaging of rat brain morphology with an ultra-small optical coherence tomography fiber probe

A well-established navigation method is one of the key conditions for successful brain surgery: it should be accurate, safe and online operable. Recent research shows that optical coherence tomography (OCT) is a potential solution for this application by providing a high resolution and small probe dimension. In this study a fiber-based spectral-domain OCT system utilizing a super-luminescent-diode with the center wavelength of 840xa0nm providing 14.5 μm axial resolution was used. A composite 125xa0μm diameter detecting probe with a gradient index (GRIN) fiber fused to a single mode fiber was employed. Signals were reconstructed into grayscale images by horizontally aligning A-scans from the same trajectory with different depths. The reconstructed images can display brain morphology along the entire trajectory. For scans of typical white matter, the signals showed a higher reflection of light intensity with lower penetration depth as well as a steeper attenuation rate compared to the scans typical for gray matter. Micro-structures such as axon bundles (70 μm) in the caudate nucleus are visible in the reconstructed images. This study explores the potential of OCT to be a navigation modality in brain surgery.

Neuroanatomical changes extend beyond striatal atrophy in X-linked dystonia parkinsonism

BACKGROUNDnX-linked dystonia-parkinsonism (XDP) is an inherited neurodegenerative adult-onset basal ganglia model disease associated with severe striatal atrophy. Anatomical changes exceeding striatal pathology were not yet described in XDP. The present study aimed to assess the microstructure of white matter tracts in XDP using magnetic resonance tomography.nnnMETHODSnDiffusion-weighted imaging was done in 10 XDP patients, aged 42.2 years (SD 8.1), and 14 ethnicity and age-matched controls, aged 40.2 years (SD 6.4). Based on diffusion tensor images, mean diffusivity (MD) and fractional anisotropy (FA) maps were calculated.nnnRESULTSnExcept for in the occipital lobe, XDP patients showed generally increased MD values across the entire white matter. FA map analysis identified four significant clusters with controls showing higher FA values than XDP patients. Involved regions included the fornix, anterior thalamic radiation, corticospinal tract, and superior corona radiata bilaterally. In the fornix and the anterior thalamic radiation, the UPDRSIII total score showed a negative correlation with mean FA values at a trend level (tauxa0=xa0-0.40, pxa0=xa00.053). Volumetric analysis revealed significant gray matter volume loss of putamen (F(1,19)xa0=xa044.2, pxa0<xa00.001), caudate nucleus (F(1,19)xa0=xa054.3, pxa0<xa00.001), and pallidum (F(1,19)xa0=xa08.9, pxa0=xa00.007).nnnCONCLUSIONSnThe present study confirms striatal atrophy in XDP and provides evidence for a strong involvement of the white matter and the pallidum. This calls into question the previously held concept of exclusive striatal atrophy in this unique movement disorder. The spared occipital region may point towards a lack of anatomical connections with the atrophied striatum.

Clinical Significance of Invasive Motor Cortex Stimulation for Trigeminal Facial Neuropathic Pain Syndromes.

BACKGROUNDnInvasive neuromodulation of the cortical surface for various chronic pain syndromes has been performed for >20 years. The significance of motor cortex stimulation (MCS) in chronic trigeminal neuropathic pain (TNP) syndromes remains unclear. Different techniques are performed worldwide in regard to operative procedure, stimulation parameters, test trials, and implanted materials.nnnOBJECTIVEnTo present the clinical experiences of a single center with MCS, surgical approach, complications, and follow-up as a prospective, noncontrolled clinical trial.nnnMETHODSnThe implantation of epidural leads over the motor cortex was performed via a burr hole technique with neuronavigation and intraoperative neurostimulation. Special focus was placed on a standardized test trial with an external stimulation device and the implementation of a double-blinded or placebo test phase to identify false-positive responders.nnnRESULTSnA total of 36 patients with TNP were operated on, and MCS was performed. In 26 of the 36 patients (72%), a significant pain reduction from a mean of 8.11 to 4.58 (on the visual analog scale) during the test trial was achieved (P < .05). Six patients were identified as false-positive responders (17%). At the last available follow-up of 26 patients (mean, 5.6 years), active MCS led to a significant pain reduction compared with the preoperative pain ratings (mean visual analog scale score, 5.01; P < .05).nnnCONCLUSIONnMCS is an additional therapeutic option for patients with refractory chronic TNP, and significant long-term pain suppression can be achieved. Placebo or double-blinded testing is mandatory.nnnABBREVIATIONSnMCS, motor cortex stimulationNRS, numeric pain rating scaleTNP, trigeminal neuropathic or deafferentation painVAS, visual analog scale.

Biochemical mechanisms of pallidal deep brain stimulation in X-linked dystonia parkinsonism

OBJECTIVEnInvasive techniques such as in-vivo microdialysis provide the opportunity to directly assess neurotransmitter levels in subcortical brain areas.nnnMETHODSnFive male Filipino patients (mean age 42.4, range 34-52 years) with severe X-linked dystonia-parkinsonism underwent bilateral implantation of deep brain leads into the internal part of the globus pallidus (GPi). Intraoperative microdialysis and measurement of gamma aminobutyric acid and glutamate was performed in the GPi in three patients and globus pallidus externus (GPe) in two patients at baseline for 25/30 min and during 25/30 min of high-frequency GPi stimulation.nnnRESULTSnWhile the gamma-aminobutyric acid concentration increased in the GPi during high frequency stimulation (231 ± 102% in comparison to baseline values), a decrease was observed in the GPe (22 ± 10%). Extracellular glutamate levels largely remained unchanged.nnnCONCLUSIONSnPallidal microdialysis is a promising intraoperative monitoring tool to better understand pathophysiological implications in movement disorders and therapeutic mechanisms of high frequency stimulation. The increased inhibitory tone of GPi neurons and the subsequent thalamic inhibition could be one of the key mechanisms of GPi deep brain stimulation in dystonia. Such a mechanism may explain how competing (dystonic) movements can be suppressed in GPi/thalamic circuits in favour of desired motor programs.