Recombinant Silk Hydrogel as a Novel Dermal Filler Component: Preclinical Safety and Efficacy Studies of a New Class of Tissue Fillers.

BACKGROUND: Hyaluronic acid-based tissue fillers are commonly utilized in reconstructive surgery as well as for aesthetic augmentation. A new type of recombinant silk-based tissue filler might pose a beneficial alternative for surgeons and patients. OBJECTIVES: The aim of this study was to compare injectability, reshaping, tolerability, and postimplantation behavior of dermal filler preparations containing recombinant silk hydrogel with a commercially available hyaluronic acid filler in 2 different animal models. METHODS: Recombinant silk hydrogel as standalone preparation or as a mixture with commercial stabilized hyaluronic acid was tested in rodent and porcine animal models. The preparations were analyzed in detail and administered subdermally followed by clinical, volumetric, and histological monitoring of the subdermal depots over several months. RESULTS: Applicability, dosing, and tissue distribution of the filler preparations were facilitated in the presence of silk hydrogel. No clinical complications attributable to tissue filler application were recorded. State-of-the art methods, such as high-performance magnetic resonance imaging, were applied successfully to monitor the volumetric development of the filler depots in live animals. CONCLUSIONS: The preclinical data demonstrate the basic suitability of recombinant silk hydrogel as safe and convenient tissue filler ingredient. Due to its shear thinning properties, recombinant silk hydrogel has the potential for less painful application, comfortable aesthetic reshaping immediately after administration, and negligible postoperative discomfort.

High-dosage granulocyte colony stimulating factor treatment alters monocyte trafficking to the brain after experimental stroke.

Ischemic stroke elicits a prompt inflammatory response that is characterized by a well-timed recruitment of peripheral immune cells to the brain. Among these, monocytes play a particularly important, but multifaceted role and have been increasingly recognized to affect stroke outcome. Granulocyte colony stimulating factor (GCSF) is known for its immunosuppressive actions on mononuclear cells, but previous studies in the stroke field were mainly confined to its neuroprotective actions. Herein, we investigated whether GCSF affects post-stroke inflammation in a mouse model of focal brain ischemia by modulating monocyte responses. Treatment with GCSF was controlled by vehicle injection, sham surgery and naive animals. Despite a significant monocytosis, high-dosage GCSF reduced the number of brain-infiltrating monocytes/macrophages four days after stroke. Lower numbers of mononuclear phagocytes in the brain were associated with smaller cerebral edema and improved motor outcome after stroke. GCSF treatment over 72h, but not 24h diminished integrin expression on circulating Ly6C+ inflammatory monocytes. In vitro experiments further revealed that GCSF strongly promotes interleukin (IL)-10 secretion by activated mononuclear cells. Blockade of the IL-10 receptor partly reversed GCSF-induced downregulation of integrin surface expression. Overall, our results suggest that high-dosage GCSF mitigates monocyte infiltration after stroke, likely by attenuating integrin-mediated adhesion to the brain endothelium in an IL-10-dependent manner. Lower amounts of mononuclear cells in the brain translate to less severe brain edema and functional impairment and thus support a harmful role of Ly6C+ inflammatory monocytes in the acute stage of stroke.

Bone marrow cell transplantation time-dependently abolishes efficacy of granulocyte colony-stimulating factor after stroke in hypertensive rats.

BACKGROUND AND PURPOSE: We aimed to determine a possible synergistic effect of granulocyte colony-stimulating factor (G-CSF) and bone marrow-derived mononuclear cells (BM MNC) after stroke in spontaneously hypertensive rats. METHODS: Male spontaneously hypertensive rats were subjected to middle cerebral artery occlusion and randomly assigned to daily injection of 50 µg/kg G-CSF for 5 days starting 1 hour after stroke (groups 1, 2, and 3) with additional intravenous transplantation of 1.5×10E7 BM MNC per kilogram at 6 hours (group 2) or 48 hours (group 3) after stroke, or control treatment (group 4). Circulating leukocyte counts and functional deficits, infarct volume, and brain edema were repeatedly assessed in the first week and first month. RESULTS: G-CSF treatment led to a significant neutrophilia, to a reversal of postischemic depression of circulating leukocytes, and to a significantly improved functional recovery without affecting the infarct volume or brain edema. BM MNC cotransplantation was neutral after 6 hours, but reversed the functional effect of G-CSF after 48 hours. Short-term investigation of combined G-CSF and BM MNC treatment at 48 hours indicated splenic accumulation of granulocytes and transplanted cells, accompanied by a significant rise of granulocytes in the circulation and the ischemic brain. CONCLUSIONS: G-CSF improved functional recovery in spontaneously hypertensive rats, but this effect was abolished by cotransplantation of BM MNC after 48 hours. In the spleen, transplanted cells may hinder the clearance of granulocytes that were massively increased by G-CSF. Increased circulation and infiltration of granulocytes into the ischemic brain may be detrimental for stroke outcome.

Significance of p16 expression in head and neck cancer patients treated with radiotherapy and cetuximab.

BACKGROUND: HPV-infection, p16 positivity, and EGFR expression have been correlated with favorable responses of head and neck cancer patients treated with radiotherapy (RT) with or without chemotherapy. However, a possible correlation of HPV/p16 and EGFR status on the effect of RT in combination with cetuximab has not been sufficiently investigated. MATERIALS AND METHODS: We analyzed tumor samples for p16 and EGFR expression and correlated these variables with treatment outcome. Cox-proportional-hazard regression models were applied to compare the risk of death among patients stratified according to risk factors. Survival was estimated by the Kaplan-Meier method. Results were compared with an institutional historical control group treated without cetuximab and with published data. RESULTS: Expression of p16 was predominantly found in oropharyngeal squamous cell cancer patients (OPSCC; 36.6% positivity; 92% of all cases), while EGFR was expressed at high levels in all tumor subsites (82%). p16 expression was associated with improved overall survival in irradiated OPSCC patients (2-year overall survival of 80% in p16-positive vs. 33% overall survival in p16-negative patients). In a multivariable analysis covering all tumor sites, nodal stage (> N2a vs. ≤ N2a) and tumor site (OPSSC vs. non-OPSCC) had an impact on overall survival. CONCLUSION: Our results show that p16 positivity is associated with a favorable outcome in OPSCC patients treated with RT and cetuximab.

A novel customizable modular bioreactor system for whole-heart cultivation under controlled 3D biomechanical stimulation.

In the last decade, cardiovascular tissue engineering has made great progress developing new strategies for regenerative medicine applications. However, while tissue engineered heart valves are already entering the clinical routine, tissue engineered myocardial substitutes are still restrained to experimental approaches. In contrast to the heart valves, tissue engineered myocardium cannot be repopulated in vivo because of its biological complexity, requiring elaborate cultivation conditions ex vivo. Although new promising approaches-like the whole-heart decellularization concept-have entered the myocardial tissue engineering field, bioreactor technology needed for the generation of functional myocardial tissue still lags behind in the sense of user-friendly, flexible and low cost systems. Here, we present a novel customizable modular bioreactor system that can be used for whole-heart cultivation. Out of a commercially obtainable original equipment manufacturer platform we constructed a modular bioreactor system specifically aimed at the cultivation of decellularized whole-hearts through perfusion and controlled 3D biomechanical stimulation with a simple but highly flexible operation platform based on LabVIEW. The modular setup not only allows a wide range of variance regarding medium conditioning under controlled 3D myocardial stretching but can also easily be upgraded for e.g. electrophysiological monitoring or stimulation, allowing for a tailor-made low-cost myocardial bioreactor system.

Changes in T2 relaxation time after stroke reflect clearing processes.

BACKGROUND AND PURPOSE: CT and MR imaging techniques are frequently used for the diagnosis and progress monitoring of ischemic stroke in clinical practice and research. After stroke, both methods are characterized by a transient pseudo-normalized imaging signal, the so-called fogging phenomenon. This study evaluates potential pathophysiological changes associated with fogging, as well as its influence on the correct determination of the ischemic lesion in a rat stroke model. METHODS: Male spontaneously hypertensive rats were subjected to permanent middle cerebral artery occlusion. Ischemic lesion volume, brain edema and gray scale value spread within the ischemic lesion were determined on T2-weighted MR sequences at days 1, 4, 8, 11 and 29 after stroke onset, and compared with immunohistochemistry for astrogliosis, microglia/macrophage infiltration and angiogenesis. RESULTS: All animals showed MR fogging at days 4, 8 and 11 after stroke. The transient normalization of T2 signals occurred independently from the development of infarct volumes, but coincided well with the spatio-temporal occurrence of necrosis, angiogenesis and microglia/macrophage infiltration. CONCLUSIONS: Our results suggest that the fogging effect reflects the clearance of necrotic tissue within the ischemic lesion and is thus not relevant for the determination of the lesion volume.

Healing of late endoscopic changes in the rectum between 12 and 65 months after external beam radiotherapy.

PURPOSE: To evaluate the time course of late rectal mucosal changes after prostate cancer radiotherapy (RT). PATIENTS AND METHODS: A rectosigmoidoscopy was performed at 12, 24, and 65 months after RT in 20 patients. Rectal mucosal changes (telangiectasia, congested mucosa, ulceration, stricture, and necrosis) were scored and documented according to the Vienna Rectoscopy Score (VRS, score 0-3). RESULTS: VRS of 0 and 3, were found in 20% of patients (n = 4) and 5% of patients (n = 1), respectively at all time points. A shift of the VRS from 2 to 1 was found with incidence rates of 60% at 12 months and 20% at 65 months, which is equivalent to an improvement rate of 67%. Laser coagulation was required in 3 patients (15%) with rectal bleeding due to telangiectasia grade ≥2. CONCLUSION: Late rectal mucosal changes are frequent after pelvic RT. Generally only the incidence rates corresponding to the initial diagnosis of the complications, independent of subsequent recovery, are reported. The results reported in the present study show that complications often improve over time. Hence, the usual reports of complication rates overestimate the proportion of patients presenting with side effects of certain grades.

Body mass index and the risk of infections in institutionalised geriatric patients.

The objective was to examine the effect of BMI on the incidence of various infectious diseases in institutionalised, geriatric subjects. In a retrospective cohort study we analysed medical records of 619 patients aged 75 years and older (mean age 87.6 (sd 6.4) years) who were treated in a geriatric hospital in Vienna, Austria. The total incidence rate of infection in this population was 0.80 per person-year. The most frequent infections were urinary tract infections (0.30 per person-year), followed by infections of the lower respiratory tract (0.19 per person-year), diarrhoea (0.12 per person-year) and other infections (0.20 per person-year). Incidence risk ratios were obtained by a multiplicative Poisson regression model. There was a J-shaped curve in the incidence of infections recorded by BMI with a nadir at 27-28 kg/m2. Compared with the reference group with a BMI of 24-27.9 kg/m2, subjects with a lower BMI had a higher incidence rate of infections. The incidence risk ratios, adjusted for sex, age and chronic diseases, were 1.62 (95 % CI 1.21, 2.17) for those with a BMI of < 20 kg/m2 and 1.84 (95 % CI 1.40, 2.42) for those with a BMI of 20-23.9 kg/m2. However, also patients with a BMI of 28 kg/m2 and above had a higher incidence rate of infections, with an incidence risk ratio of 1.54 (95 % CI 1.07, 2.22). These results show that both underweight and obesity are associated with a higher risk of infections in institutionalised geriatric patients.

Imaging of glial cell morphology, SOD1 distribution and elemental composition in the brainstem and hippocampus of the ALS hSOD1G93A rat.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting motor and cognitive domains of the CNS. Mutations in the Cu,Zn-superoxide dismutase (SOD1) cause 20% of familial ALS and provoke formation of intracellular aggregates and copper and zinc unbinding, leading to glial activation and neurodegeneration. Therefore, we investigated glial cell morphology, intracellular SOD1 distribution, and elemental composition in the brainstem and hippocampus of the hSOD1G93A transgenic rat model of ALS. Immunostaining for astrocytes, microglia and SOD1 revealed glial proliferation and progressive tissue accumulation of SOD1 in both brain regions of ALS rats starting already at the presymptomatic stage. Glial cell morphology analysis in the brainstem of ALS rats revealed astrocyte activation occurring before disease symptoms onset, followed by activation of microglia. Hippocampal ALS astrocytes exhibited an identical reactive profile, while microglial morphology was unchanged. Additionally, ALS brainstem astrocytes demonstrated progressive SOD1 accumulation in the cell body and processes, while microglial SOD1 levels were reduced and its distribution limited to distal cell processes. In the hippocampus both glial cell types exhibited SOD1 accumulation in the cell body. X-ray fluorescence imaging revealed decreased P and increased Ca, Cl, K, Ni, Cu and Zn in the brainstem, and higher levels of Cl, Ni and Cu, but lower levels of Zn in the hippocampus of symptomatic ALS rats. These results bring new insights into the glial response during disease development and progression in motor as well as in non-motor CNS structures, and indicate disturbed tissue elemental homeostasis as a prominent hallmark of disease pathology.

Rheology of perfusates and fluid dynamical effects during whole organ decellularization: a perspective to individualize decellularization protocols for single organs.

The approach of whole organ decellularization is rapidly becoming more widespread within the tissue engineering community. Today it is well known that the effects of decellularization protocols may vary with the particular type of treated tissue. However, there are no methods known to individualize decellularization protocols while automatically ensuring a standard level of quality to minimize adverse effects on the resulting extracellular matrix. Here we follow this idea by introducing two novel components into the current practice. First, a non-invasive method for online monitoring of resulting fluid dynamical characteristics of the coronary system is demonstrated for application during the perfusion decellularization of whole hearts. Second, the observation of the underlying rheological characteristics of the perfusates is employed to detect ongoing progress and maturation of the decellularization process. Measured data were contrasted to the respective release of specific cellular components. We demonstrate rheological measurements to be capable of detecting cellular debris along with a discriminative capture of DNA and protein ratios. We demonstrate that this perfusate biomass is well correlated to the biomass loss in the extracellular matrix produced by decellularization. The appearance of biomass components in the perfusates could specifically reflect the appearance of fluid dynamical characteristics that we monitored during the decellularization process. As rheological measuring of perfusate samples can be done within minutes, without any time-consuming preparation steps, we predict this to be a promising novel analytic strategy to control decellularization protocols, in time, by the actual conditions of the processed organ.

Arterial Hypertension Aggravates Innate Immune Responses after Experimental Stroke.

Arterial hypertension is not only the leading risk factor for stroke, but also attributes to impaired recovery and poor outcome. The latter could be explained by hypertensive vascular remodeling that aggravates perfusion deficits and blood-brain barrier disruption. However, besides vascular changes, one could hypothesize that activation of the immune system due to pre-existing hypertension may negatively influence post-stroke inflammation and thus stroke outcome. To test this hypothesis, male adult spontaneously hypertensive rats (SHRs) and normotensive Wistar Kyoto rats (WKYs) were subjected to photothrombotic stroke. One and 3 days after stroke, infarct volume and functional deficits were evaluated by magnetic resonance imaging and behavioral tests. Expression levels of adhesion molecules and chemokines along with the post-stroke inflammatory response were analyzed by flow cytometry, quantitative real-time PCR and immunohistochemistry in rat brains 4 days after stroke. Although comparable at day 1, lesion volumes were significantly larger in SHR at day 3. The infarct volume showed a strong correlation with the amount of CD45 highly positive leukocytes present in the ischemic hemispheres. Functional deficits were comparable between SHR and WKY. Brain endothelial expression of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and P-selectin (CD62P) was neither increased by hypertension nor by stroke. However, in SHR, brain infiltrating myeloid leukocytes showed significantly higher surface expression of ICAM-1 which may augment leukocyte transmigration by leukocyte-leukocyte interactions. The expression of chemokines that primarily attract monocytes and granulocytes was significantly increased by stroke and, furthermore, by hypertension. Accordingly, ischemic hemispheres of SHR contain considerably higher numbers of monocytes, macrophages and granulocytes. Exacerbated brain inflammation in SHR may finally be responsible for larger infarct volumes. These findings provide an immunological explanation for the epidemiological observation that existing hypertension negatively affects stroke outcome and mortality.

Transplantation of cryopreserved human umbilical cord blood mononuclear cells does not induce sustained recovery after experimental stroke in spontaneously hypertensive rats.

Previous studies have highlighted the enormous potential of cell-based therapies for stroke not only to prevent ischemic brain damage, but also to amplify endogenous repair processes. Considering its widespread availability and low immunogenicity human umbilical cord blood (HUCB) is a particularly attractive stem cell source. Our goal was to investigate the neurorestorative potential of cryopreserved HUCB mononuclear cells (MNC) after permanent middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats (SHR). Human umbilical cord blood MNC or vehicle solution was administered intravenously 24 hours after MCAO. Experimental groups were as follows: (1) quantitative polymerase chain reaction (PCR) of host-derived growth factors up to 48 hours after stroke; (2) immunohistochemical analysis of astroglial scarring; (3) magnetic resonance imaging (MRI) and weekly behavioral tests for 2 months after stroke. Long-term functional outcome and lesion development on MRI were not beneficially influenced by HUCB MNC therapy. Furthermore, HUCB MNC treatment did not change local growth factor levels and glial scarring extent. In summary, we could not demonstrate neurorestorative properties of HUCB MNC after stroke in SHR. Our results advise caution regarding a prompt translation of cord blood therapy into clinical stroke trials as long as deepened knowledge about its precise modes of action is missing.

Continuous adenosine A2A receptor antagonism after focal cerebral ischemia in spontaneously hypertensive rats.

Antagonism of the adenosine A2A receptor (A2AR) has been shown to elicit substantial neuroprotective properties when given immediately after cerebral ischemia. We asked whether the continuous application of a selective A2AR antagonist within a clinically relevant time window will be a feasible and effective approach to treat focal cerebral ischemia. To answer this question, we subjected 20 male spontaneously hypertensive rats to permanent middle cerebral artery occlusion and randomized them equally to a verum and a control group. Two hours after stroke onset, the animals received a subcutaneous implantation of an osmotic minipump filled with 5 mg kg(-1) day(-1) 8-(3-chlorostyryl) caffeine (CSC) or vehicle solution. The serum level of CSC was measured twice a day for three consecutive days. The infarct volume was determined at days 1 and 3 using magnetic resonance imaging. We found the serum level of CSC showing a bell-shaped curve with its maximum at 36 h. The infarct volume was not affected by continuous CSC treatment. These results suggest that delayed and continuous CSC application was not sufficient to treat acute ischemic stroke, potentially due to unfavorable hepatic elimination and metabolization of the pharmaceutical.

Spontaneous white matter damage, cognitive decline and neuroinflammation in middle-aged hypertensive rats: an animal model of early-stage cerebral small vessel disease.

INTRODUCTION: Cerebral small vessel disease (cSVD) is one of the most prevalent neurological disorders. The progressive remodeling of brain microvessels due to arterial hypertension or other vascular risk factors causes subtle, but constant cognitive decline through to manifest dementia and substantially increases the risk for stroke. Preliminary evidence suggests the contribution of the immune system to disease initiation and progression, but a more detailed understanding is impaired by the unavailability of appropriate animal models. Here, we introduce the spontaneously hypertensive rat (SHR) as a model for early onset cSVD and unveiled substantial immune changes in conjunction with brain abnormalities that resemble clinical findings. RESULTS: In contrast to age-matched normotensive Wistar Kyoto (WKY) rats, male SHR exhibited non-spatial memory deficits. Magnetic resonance imaging showed brain atrophy and a reduction of white matter volumes in SHR. Histological analyses confirmed white matter demyelination and unveiled a circumscribed blood brain barrier dysfunction in conjunction with micro- and macrogliosis in deep cortical regions. Flow cytometry and histological analyses further revealed substantial disparities in cerebral CD45high leukocyte counts and distribution patterns between SHR and WKY. SHR showed lower counts of T cells in the choroid plexus and meningeal spaces as well as decreased interleukin-10 levels in the cerebrospinal fluid. On the other hand, both T and NK cells were significantly augmented in the SHR brain microvasculature. CONCLUSIONS: Our results indicate that SHR share behavioral and neuropathological characteristics with human cSVD patients and further undergird the relevance of immune responses for the initiation and progression of cSVD.

Decellularized whole heart for bioartificial heart.

Whole-organ decellularization has opened the gates to the creation of 3D extracellular matrix (ECM) templates that mimic nature's design to a degree that-as for today-is not reproducible with any synthetic materials. Here, we describe a whole-heart decellularization approach through software-controlled automated coronary perfusion with standard decellularization detergents, enabling us to create native ECM-derived 3D templates that preserve the basic anatomy, vascular network, and critical ECM characteristics of the native heart. Such a cardiac ECM platform directly derived from nature itself might help us to better understand and reproduce cardiac biology and may even lay the grounds for the construction of a bioartificial heart in the future.

Object-based analysis of astroglial reaction and astrocyte subtype morphology after ischemic brain injury.

The astrocytic response to ischemic brain injury is characterized by specific alterations of glial cell morphology and function. Various studies described both beneficial and detrimental aspects of activated astrocytes, suggesting the existence of different subtypes. We investigated this issue using a novel object-based approach to study characteristics of astrogliosis after stroke. Spontaneously hypertensive rats received permanent middle cerebral artery occlusion. After 96 h, brain specimens were removed, fixed and stained for GFAP, glutamine synthetase (GS), S100Beta and Musashi1 (Msh1). Three regions of interest were defined (contralateral hemisphere, ipsilateral remote zone and infarct border zone), and confocal stacks were acquired (n=5 biological with each n=4 technical replicates). The stacks were background-corrected and colocalization between the selected markers and GFAP was determined using an automated thresholding algorithm. The fluorescence and colocalization channels were then converted into 3D-objects using both intensity and volume as filters to ultimately determine the final volumes of marker expression and colocalization, as well as the morphological changes of astrocyte process arborisation. We found that both S100Beta and Msh1 determined the same GFAP-positive astroglial cell population albeit the cellular compartments differed. GFAP stained most of the astrocyte processes and is hence suitable for the analysis of qualitative characteristics of astrogliosis. Due to its peri-nuclear localization, Msh1 is appropriate to estimate the total number of astrocytes even in regions with severe reactive astrogliosis. GS expression in GFAP-positive astrocytes was high in the remote zone and low at the infarct border, indicating the existence of astrocyte subclasses.

A novel native derived coronary artery tissue-flap model.

Although tissue-engineering approaches have led to significant progress in the quest of finding a viable substitute for dysfunctional myocardium, the vascularization of such bioartificial constructs still remains a major challenge. Hence, there is a need for model systems that allow us to study and better understand cardiac and vascular biology to overcome current limitations. Therefore, in this study, in toto decellularized rat hearts with a patent vessel system were processed into standardized coronary artery tissue flaps adherent to the ascending aorta. Protein diffusivity analysis and blood perfusion of the coronary arteries showed proper sealing of the de-endothelialized vessels. Retrograde aortic perfusion allowed for selective seeding of the coronary artery system, while surface seeding of the tissue flaps allowed for additional controlled coculture with cardiac cells. The coronary artery tissue-flap model offers a patent and perfusable coronary vascular architecture with a preserved cardiac extracellular matrix, therefore mimicking nature's input to the highest possible degree. This offers the possibility to study re-endothelialization and endothelial function of different donor cell types and their interaction with cardiac cells in a standardized biologically derived cardiac in vitro model, while establishing a platform that could be used for in vitro drug testing and stem cell differentiation studies.

Neurovascular pathophysiology in cerebral ischemia, dementia and the ageing brain - current trends in basic, translational and clinical research.

The 7th International Symposium on Neuroprotection and Neurorepair was held from May 2nd to May 5th, 2012 in Potsdam, Germany. The symposium, which directly continues the successful Magdeburg meeting series, attracted over 330 colleagues from 29 countries to discuss recent findings and advances in the field. The focus of the 2012 symposium was widened from stroke and traumatic brain injury to neurodegenerative diseases, notably dementia, and more generally the ageing brain. Thereby, emphasis was given on neurovascular aspects of neurodegeneration and stroke including the blood-brain barrier, recent findings regarding the pathomechanism of Alzheimer's disease, and brain imaging approaches. In addition, neurobiochemical aspects of neuroprotection, the role of astrogliosis, the clinical progress of cell-based approaches as well as translational hurdles and opportunities were discussed in-depth. This review summarizes some of the most stimulating discussions and reports from the meeting.

Impact of age on the efficacy of bone marrow mononuclear cell transplantation in experimental stroke.

Bone marrow-derived mononuclear cells (BM MNC) have been effectively used to treat experimental stroke. Most of the preclinical trials have been performed in young and healthy laboratory animals, even though age and hypertension are major risk factors for stroke. To determine the influence of age on the properties of BM MNCs after cerebral ischemia, we compared the efficacy of aged and young BM MNC in an in vitro model of cerebral hypoxia and in an adapted in vivo model of stroke. Human BM MNCs were obtained from healthy young or aged donors and either co-cultured with rat hippocampal slices exposed to oxygen glucose deprivation (OGD), or transplanted intravenously 24 h after permanent middle cerebral artery occlusion in aged (18 months) spontaneously hypertensive rats (SHR). Efficacy was examined by quantification of hippocampal cell death, or respectively, by neurofunctional tests and MR investigations. Co-cultivation with young, but not with aged BM MNCs significantly reduced the hippocampal cell death after OGD. Transplantation of both young and old BM MNCs did not reduce functional deficits or ischemic lesion volume after stroke in aged SHR. These results suggest a significant impact of age on the therapeutic efficacy of BM MNCs after cerebral ischemia.