Discovery of ultrafast spontaneous spin switching in an antiferromagnet by femtosecond noise correlation spectroscopy.

Owing to their high magnon frequencies, antiferromagnets are key materials for future high-speed spintronics. Picosecond switching of antiferromagnetic spin systems has been viewed a milestone for decades and pursued only by using ultrafast external perturbations. Here, we show that picosecond spin switching occurs spontaneously due to thermal fluctuations in the antiferromagnetic orthoferrite Sm0.7Er0.3FeO3. By analysing the correlation between the pulse-to-pulse polarisation fluctuations of two femtosecond optical probes, we extract the autocorrelation of incoherent magnon fluctuations. We observe a strong enhancement of the magnon fluctuation amplitude and the coherence time around the critical temperature of the spin reorientation transition. The spectrum shows two distinct features, one corresponding to the quasi-ferromagnetic mode and another one which has not been previously reported in pump-probe experiments. Comparison to a stochastic spin dynamics simulation reveals this new mode as smoking gun of ultrafast spontaneous spin switching within the double-well anisotropy potential.

Methylation subgroup and molecular heterogeneity is a hallmark of glioblastoma: implications for biopsy targeting, classification and therapy.

BACKGROUND: Intratumoral heterogeneity at the cellular and molecular level is a hallmark of glioblastoma (GB) that contributes to treatment resistance and poor clinical outcome. Little is known regarding epigenetic heterogeneity and intratumoral phylogeny and their implication for molecular classification and targeted therapies. PATIENTS AND METHODS: Multiple tissue biopsies (238 in total) were sampled from 56 newly-diagnosed, treatment-naive GB patients from a prospective in-house cohort and publicly available data and profiled for DNA methylation using the Illumina MethylationEPIC array. Methylation-based classification using the glioma classifier developed by Ceccarelli et al. and estimation of the MGMT promoter methylation status via the MGMT-STP27 model were carried out. In addition, copy number variations (CNVs) and phylogeny were analyzed. RESULTS: Almost half of the patients (22/56, 39%) harbored tumors composed of heterogeneous methylation subtypes. We found two predominant subtype combinations: classic-/mesenchymal-like, and mesenchymal-/pilocytic astrocytoma-like. Nine patients (16%) had tumors composed of subvolumes with and without MGMT promoter methylation, whereas 20 patients (36%) were homogeneously methylated, and 27 patients (48%) were homogeneously unmethylated. CNV analysis revealed high variations in many genes, including CDKN2A/B, EGFR, and PTEN. Phylogenetic analysis correspondingly showed a general pattern of CDKN2A/B loss and gain of EGFR, PDGFRA, and CDK4 during early stages of tumor development. CONCLUSIONS: (Epi)genetic intratumoral heterogeneity is a hallmark of GB, both at DNA methylation and CNV level. This intratumoral heterogeneity is of utmost importance for molecular classification as well as for defining therapeutic targets in this disease, as single biopsies might underestimate the true molecular diversity in a tumor.

Infection rate and complications after 621 transperineal MRI-TRUS fusion biopsies in local anesthesia without standard antibiotic prophylaxis.

PURPOSE: The aim of this study was to assess the post biopsy infection rate, feasibility and prostate cancer (PCa) detection rate (CDR) by performing transperineal MRI-TRUS fusion biopsy of the prostate (TPBx) under local anesthesia (LA) without antibiotic prophylaxis (AP). METHODS: We prospectively screened 766 men with suspicious lesions on mpMRI, an elevated PSA level or a suspect digital examination undergoing MRI-TRUS-TPBx in LA, from May 2019 to July 2020. Patients with the need for antibiotic prophylaxis or without a PI-RADS target lesion were excluded from final analyses. We reported CDR, perioperative pain (0-10) and postoperative complications. PCa with an ISUP grade ≥ 2 was classified as clinically significant PCa (csPCa). RESULTS: We included 621 patients with a median age of 68 years (IQR 62-74), a PSA of 6.43 ng/mL (IQR 4.72-9.91) and a prostate volume of 45 cc (IQR 32-64). In median, 4 targeted (TB) (IQR 3-4) and 6 (IQR 5-7) systematic biopsies (SB) detected in combination overall 416 (67%) PCa and 324 (52%) csPCa. Overall CDR of TB for PI-RADS 3, 4 and 5 was 26%, 65% and 84%, respectively. Patients reported a median perioperative pain level of 2 (IQR 1-3). Four patients (0.6%) developed a post biopsy infection, one experienced urosepsis. CONCLUSION: Our results demonstrate that transperineal MRI-TRUS fusion-guided prostate biopsy under LA without AP is feasible, safe and well tolerated.

[Initial results of perineal MRI/ultrasound fusion biopsies under local anesthesia without standard perioperative antibiotic prophylaxis]. / Etablierung der perinealen MRT­/Ultraschallfusionsbiopsien in Lokalanästhesie ohne standardmäßige, perioperative Antibiotikaprophylaxe.

The perineal approach for prostate biopsy (PB) is a sterile alternative to conventional transrectal PB. Targeted local anesthesia allows perineal prostate biopsy (pPB) to be performed without general anesthesia. This paper presents the first results after establishing perineal MRI/ultrasound fusion biopsy (pFB) under local anesthesia without standard perioperative antibiotic prophylaxis. For this purpose, 144 patients were included in the study after pFB at the Vivantes Klinikum am Urban. No peri-interventional antibiotic prophylaxis was applied. Peri- and postoperatively, the pain sensation, measured using an analogue pain scale from 0-10, and complications were recorded. The median patient age was 68 and the median prostate-specific antigen (PSA) value 7.07 ng/ml. In all, 49% of the patients received primary PB. The overall detection rate for prostate cancer (PCa) was 71% and for PI-RADS 3, 4 and 5 was 44, 71 and 92%, respectively. The median pain sensation during biopsy was 2. Furthermore, 63% of patients with a transrectal prebiopsy considered this to be more painful and another 20% expressed similar pain levels. Only 1 patient developed a febrile urinary tract infection. The pFB of the prostate under local anesthesia without antibiotic, perioperative prophylaxis is a suitable alternative to the transrectal PB with regard to the detection rate of PCa, the side effect profile and the subjective pain perception of the patients during the intervention.

Toward genome editing in X-linked RP-development of a mouse model with specific treatment relevant features.

Genome editing represents a powerful tool to treat inherited disorders. Highly specific endonucleases induce a DNA double strand break near the mutant site, which is subsequently repaired by cellular DNA repair mechanisms that involve the presence of a wild type template DNA. In vivo applications of this strategy are still rare, in part due to the absence of appropriate animal models carrying human disease mutations and knowledge of the efficient targeting of endonucleases. Here we report the generation and characterization of a new mouse model for X-linked retinitis pigmentosa (XLRP) carrying a point mutation in the mutational hotspot exon ORF15 of the RPGR gene as well as a recognition site for the homing endonuclease I-SceI. Presence of the genomic modifications was verified at the RNA and protein levels. The mutant protein was observed at low levels. Optical coherence tomography studies revealed a slowly progressive retinal degeneration with photoreceptor loss starting at 9 months of age, paralleling the onset of functional deficits as seen in the electroretinogram. Early changes to the outer retinal bands can be used as biomarker during treatment applications. We further show for the first time efficient targeting using the I-SceI enzyme at the genomic locus in a proof of concept in photoreceptors following adeno-associated virus mediated gene transfer in vivo. Taken together, our studies not only provide a human-XLRP disease model but also act as a platform to design genome editing technology for retinal degenerative diseases using the currently available endonucleases.

Evaluation of radiation-related invasion in primary patient-derived glioma cells and validation with established cell lines: impact of different radiation qualities with differing LET.

PURPOSE: Glioblastoma multiforme (GBM) is the most common primary brain tumor and has a very poor overall prognosis. Multimodal treatment is still inefficient and one main reason is the invasive nature of GBM cells, enabling the tumor cells to escape from the treatment area causing tumor progression. This experimental study describes the effect of low- and high-LET irradiation on the invasion of primary GBM cells with a validation in established cell systems. METHODS: Seven patient derived primary GBM as well as three established cell lines (LN229, LN18 and U87) were used in this study. Invasion was investigated using Matrigel® coated transwell chambers. Irradiation was performed with low- (X-ray) and high-LET (alpha particles) radiation. The colony formation assay was chosen to determine the corresponding alpha particle dose equivalent to the X-ray dose. RESULTS: 4 Gy X-ray irradiation increased the invasive potential of six patient derived GBM cells as well as two of the established lines. In contrast, alpha particle irradiation with an equivalent dose of 1.3 Gy did not show any effect on the invasive behavior. The findings were validated with established cell lines. CONCLUSION: Our results show that in contrast to low-LET irradiation high-LET irradiation does not enhance the invasion of established and primary glioblastoma cell lines. We therefore suggest that high-LET irradiation could become an alternative treatment option. To fully exploit the benefits of high-LET irradiation concerning the invasion of GBM further molecular studies should be performed.

Serum periostin levels in early in pregnancy are significantly altered in women with miscarriage.

BACKGROUND: Miscarriage is a common complication in pregnancy and there is still a lack of biomarkers usable in asymptomatic patients before the event occurs. Periostin (PER), whose levels rise particularly during injury or inflammation, has been shown to play an important local role in implantation and early embryonic development. As PER has been described as a biomarker in various medical conditions we intended to evaluate if changes in PER serum levels may help to identify women at risk for spontaneous abortion in the first trimester. METHODS: Women between 18 and 42 years without confounding comorbidities who conceived by IVF/ICSI and ovarian hyperstimulation were analysed in the study after informed consent. Maternal serum samples from 41 patients were assessed at the time of pregnancy testing (PT) and the following first ultrasound checkup (US). Patients were subsequently divided in two groups: (1) patients with subsequent miscarriage in the first trimester (n = 18) and (2) patients with ongoing pregnancy (n = 23), allowing for statistical analysis and investigating the change of PER levels per individual. PER levels were measured using enzyme-linked immunosorbent assay. Statistical analysis was performed using the Fisher exact and Student's t test. p ≤ 0.05 was considered to be significant. RESULTS: There was no significant difference concerning possible confounders between the two groups. We did not find any significant difference in PER levels at the time point of PT or US. By investigating the interindividual changes of PER between the two time points however, we observed that patients with a following miscarriage showed increasing levels of PER at the time point of PT compared to US in contrast to patients with an ongoing pregnancy who demonstrated a decrease in PER levels. These alterations were significant in the absolute as well as in the relative comparison. CONCLUSION: The relative expression of PER between PT and US is significantly altered in asymptomatic women with subsequent miscarriage compared to women with ongoing pregnancy. Therefore systemic PER levels might represent a potential promising biomarker for the assessment of pregnancy outcome. TRIAL REGISTRATION: Not applicable.

Incorporation studies of clickable ceramides in Jurkat cell plasma membranes.

The incorporation properties of ceramide analogues for click chemistry in Jurkat T cells were investigated. The analogues varied in the acyl chain length and the position of the functional group for click chemistry. Fluorescence microscopy studies including anisotropy and quenching experiments showed significant differences in the accessibility of the functional group indicating different incorporation properties into the plasma membrane.

Registration procedure for spatial correlation of physical energy deposition of particle irradiation and cellular response utilizing cell-fluorescent ion track hybrid detectors.

The hybrid technology cell-fluorescent ion track hybrid detector (Cell-Fit-HD) enables the investigation of radiation-related cellular events along single ion tracks on the subcellular scale in clinical ion beams. The Cell-Fit-HD comprises a fluorescent nuclear track detector (FNTD, the physical compartment), a device for individual particle detection and a substrate for viable cell-coating, i.e. the biological compartment. To date both compartments have been imaged sequentially in situ by confocal laser scanning microscopy (CLSM). This is yet in conflict with a functional read-out of the Cell-Fit-HD utilizing a fast live-cell imaging of the biological compartment with low phototoxicity on greater time scales. The read-out of the biological from the physical compartment was uncoupled. A read-out procedure was developed to image the cell layer by conventional widefield microscopy whereas the FNTD was imaged by CLSM. Point mapping registration of the confocal and widefield imaging data was performed. Non-fluorescent crystal defects (spinels) visible in both read-outs were used as control point pairs. The accuracy achieved was on the sub-µm scale. The read-out procedure by widefield microscopy does not impair the unique ability of spatial correlation by the Cell-Fit-HD. The uncoupling will enlarge the application potential of the hybrid technology significantly. The registration allows for an ultimate correlation of microscopic physical beam parameters and cell kinetics on greater time scales. The method reported herein will be instrumental for the introduction of a novel generation of compact detectors facilitating biodosimetric research towards high-throughput analysis.

[Interdisciplinary neuro-oncology: part 1: diagnostics and operative therapy of primary brain tumors]. / Interdisziplinäre Neuroonkologie : Teil 1: Diagnostik und operative Therapie primärer Gehirntumoren.

By combining the expertise of clinical neuroscience, the aim of neuro-oncology is to optimize diagnostic planning and therapy of primary brain tumors in an interdisciplinary setting together with radio-oncology and medical oncology. High-end imaging frequently allows brain tumors to be diagnosed preoperatively with respect to tumor entity and even tumor malignancy grade. Moreover, neuroimaging is indispensable for guidance of biopsy resection and monitoring of therapy. Surgical resection of intracranial lesions with preservation of neurological function is increasingly feasible. Tools to achieve this goal are, for example neuronavigation, functional magnetic resonance imaging (fMRI), tractography, intraoperative cortical stimulation and precise intraoperative definition of tumor margins by virtue of various techniques. In addition to classical histopathological diagnosis and tumor classification, modern neuropathology is supplemented by molecular characterization of brain tumors in order to provide clinicians with prognostic and predictive (of therapy) markers, such as codeletion of chromosomes 1p and 19q in anaplastic gliomas and O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation in glioblastomas. Although this is not yet individualized tumor therapy, the increasingly more detailed analysis of the molecular pathogenesis of an individual glioma will eventually lead to specific pharmacological blockade of disturbed intracellular pathways in individual patients. This article gives an overview of the state of the art of interdisciplinary neuro-oncology whereby part 1 deals with the diagnostics and surgical therapy of primary brain tumors and part 2 describes the medical therapy of primary brain tumors.

[Interdisciplinary neuro-oncology: part 2: systemic therapy of primary brain tumors]. / Interdisziplinäre Neuroonkologie : Teil 2: Systemtherapie primärer Gehirntumoren.

By combining the expertise of clinical neuroscience, the aim of neuro-oncology is to optimize diagnostic planning and therapy of primary brain tumors in an interdisciplinary setting together with radio-oncology and medical oncology. High-end imaging frequently allows brain tumors to be diagnosed preoperatively with respect to tumor entity and even tumor malignancy grade. Moreover, neuroimaging is indispensable for guidance of biopsy resection and monitoring of therapy. Surgical resection of intracranial lesions with preservation of neurological function has become dramatically more extensive. Tools to achieve this goal are, for example neuronavigation, functional magnetic resonance imaging (fMRI), tractography, intraoperative cortical stimulation and precise intraoperative definition of tumor margins by virtue of various techniques. In addition to classical histopathological diagnosis and tumor classification, modern neuropathology is supplemented by molecular characterization of brain tumors in order to provide clinicians with prognostic and predictive (of therapy) markers, such as codeletion of chromosomes 1p and 19q in anaplastic gliomas and O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation in glioblastomas. Although this is not yet individualized tumor therapy, the increasingly more detailed analysis of the molecular pathogenesis of an individual glioma will eventually lead to specific pharmacological blockade of disturbed intracellular pathways in individual patients. This article gives an overview of the state of the art of interdisciplinary neuro-oncology whereby part 1 deals with the diagnostics and surgical therapy of primary brain tumors and part 2 describes the medical therapy of primary brain tumors.

Aberrant Mer receptor tyrosine kinase expression contributes to leukemogenesis in acute myeloid leukemia.

Acute myeloid leukemia (AML) continues to be extremely difficult to treat successfully, and the unacceptably low overall survival rates mandate that we assess new potential therapies to ameliorate poor clinical response to conventional therapy. Abnormal tyrosine kinase activation in AML has been associated with poor prognosis and provides strategic targets for novel therapy development. We found that Mer receptor tyrosine kinase was over-expressed in a majority of pediatric (29/36, 80%) and adult (10/10, 100%) primary AML patient blasts at the time of diagnosis, and 100% of patient samples at the time of relapse. Mer was also found to be expressed in 12 of 14 AML cell lines (86%). In contrast, normal bone marrow myeloid precursors expressed little to no Mer. Following AML cell line stimulation with Gas6, a Mer ligand, we observed activation of prosurvival and proliferative signaling pathways, including phosphorylation of ERK1/2, p38, MSK1, CREB, ATF1, AKT and STAT6. To assess the phenotypic role of Mer in AML, two independent short-hairpin RNA (shRNA) constructs were used to decrease Mer expression in the AML cell lines Nomo-1 and Kasumi-1. Reduction of Mer protein levels significantly increased rates of myeloblast apoptosis two to threefold in response to serum starvation. Furthermore, myeloblasts with knocked-down Mer demonstrated decreased colony formation by 67-87%, relative to control cell lines (P<0.01). NOD-SCID-gamma mice transplanted with Nomo-1 myeloblasts with reduced levels of Mer had a significant prolongation in survival compared with mice transplanted with the parental or control cell lines (median survival 17 days in parental and control cell lines, versus 32-36 days in Mer knockdown cell lines, P<0.0001). These data suggest a role for Mer in acute myeloid leukemogenesis and indicate that targeted inhibition of Mer may be an effective therapeutic strategy in pediatric and adult AML.

Investigation of the mutagenic potential of cold atmospheric plasma at bactericidal dosages.

In the past few years, cold atmospheric plasma (CAP) has evolved into a new tool in the fight against nosocomial infections and antibiotic-resistant microorganisms. The products generated by the plasma-electrons, ions, reactive species and UV light-represent a 'lethal cocktail' for different kinds of pathogen, which opens up possible applications in hygiene and medicine. Nevertheless, to ensure the safe usage of CAP on skin (e.g., to treat wounds or skin diseases) several pre-clinical in vitro studies have to be performed before implementing clinical trials on humans. In the study presented here, inactivation experiments with Escherichia coli were carried out to identify the necessary plasma dosage for a 5 log reduction: with a small hand-held battery-operated CAP device, these disinfection properties were achieved after application during 30s. This and higher plasma dosages were then used to analyze the mutagenicity induced in V79 Chinese hamster cells-to furthermore define a 'safe application window'-with the HPRT (hypoxanthine-guanine phosphoribosyl transferase) mutation assay. The results show that a CAP treatment of up to 240 s and repeated treatments of 30s every 12h did not induce mutagenicity at the Hprt locus beyond naturally occurring spontaneous mutations.

Inhibition of MerTK increases chemosensitivity and decreases oncogenic potential in T-cell acute lymphoblastic leukemia.

Pediatric leukemia survival rates have improved dramatically over the past decades. However, current treatment protocols are still largely ineffective in cases of relapsed leukemia and are associated with a significant rate of chronic health conditions. Thus, there is a continued need for new therapeutic options. Here, we show that mer receptor tyrosine kinase (MerTK) was abnormally expressed in approximately one half of pediatric T-cell leukemia patient samples and T-cell acute lymphoblastic leukemia (T-ALL) cell lines. Stimulation of MerTK by the ligand Gas6 led to activation of the prosurvival proteins Erk 1/2 and Stat5, and MerTK-dependent activation of the STAT pathway in leukemia represents a novel finding. Furthermore, inhibition of MerTK expression increased the sensitivity of T-ALL cells to treatment with chemotherapeutic agents and decreased the oncogenic potential of the Jurkat T-ALL cell line in a methylcellulose colony-forming assay. Lastly, inhibition of MerTK expression significantly increased median survival in a xenograft mouse model of leukemia (30.5 days vs 60 days, P<0.0001). These results suggest that inhibition of MerTK is a promising therapeutic strategy for the treatment of leukemia and may allow for dose reduction of currently used chemotherapeutics resulting in decreased rates of therapy-associated toxicities.

Inhibition of NGF-induced neurite outgrowth of rat pheochromocytoma cells (PC12) following administration of dioxyamphetamine.

Amphetamine analogs are known to induce not only neurotoxicity at serotonergic axon terminals but also neocortical neuronal degeneration. However, a much less studied aspect involves the impact of amphetamine exposure on neuronal development. The present study investigated whether pretreatment of PC12 cells with dioxyamphetamine (DA) alters differentiation of PC12 cells by NGF and, if so, which components of the Ras/Raf/MEK/ERK pathway known to be involved in the differentiation response to NGF are particularly affected. Though exposure of PC12 cells to DA 1h prior to NGF treatment resulted in apopotosis, several PC12 cells survived. However, neurite outgrowth of these NGF-responsive cells was repressed. Immunoblots of whole cell extracts revealed a strong induction rather than inhibition of ERK phosphorylation up to 48h after DA/NGF treatment. Our results indicate that NGF-mediated neurite outgrowth was inhibited by pretreatment with DA, and this blockage of NGF-induced neuritogenesis was not due to an inhibition of ERK phosphorylation.

The novel gene MIA2 acts as a tumour suppressor in hepatocellular carcinoma.

BACKGROUND: Melanoma inhibitory activity 2 (MIA2) is a novel gene of the MIA gene family. The selective expression of MIA2 in hepatocytes is controlled by hepatocyte nuclear factor (HNF) 1 binding sites in the MIA2 promotor. In contrast, in most hepatocellular carcinomas (HCC) MIA2 expression is down-regulated or lost. AIM: In this study we examined the regulation and functional role of MIA2 in hepatocancerogenesis. METHODS AND RESULTS: In HCC cell lines and tissues HNF-1 expression was lower than in primary human hepatocytes (PHH) and corresponding non-tumorous tissue, respectively, and correlated significantly with the down-regulation of MIA2 expression. Re-expression of HNF-1 in HCC cells reinduced MIA2 in HCC cells to similar levels as found in PHH. Further, MIA2 was re-expressed in HCC cell lines by stable transfection, and the generated cell clones revealed a strongly reduced invasive potential and proliferation rate in vitro. In line with these findings treatment of HCC cells with recombinant MIA2 inhibited proliferation and invasion. In nude mice MIA2 re-expressing HCC cells grew significantly slower and revealed a less invasive growth pattern. Immunohistochemical analysis of a tissue microarray containing HCC and corresponding non-cancerous liver tissue of 85 patients confirmed reduced MIA2 expression in HCC. Furthermore, MIA2 negative HCC tissue showed a significantly higher Ki67 labelling index and loss of MIA2 expression correlated significantly with more advanced tumour stages. CONCLUSION: This study presents MIA2 as an inhibitor of HCC growth and invasion both in vitro and in vivo, and consequently, as a tumour suppressor of HCC. Further, our findings indicate a novel mechanism, how loss of HNF-1 expression in HCC affects tumorigenicity via down-regulation of MIA2.

[MRI of arthritis with the USPIO SH U 555 C: optimization of T1 enhancement]. / MRT der Arthritis mit dem USPIO SH U 555 C: Optimierung des T1-Enhancements.

PURPOSE: To optimize contrast agent dose and pulse sequence parameters in order to achieve a maximal T1 enhancement in arthritic knee joints with ultra small superparamagnetic iron oxides (USPIO)-enhanced MRI. MATERIALS AND METHODS: Antigen-mediated arthritis was induced in the right knee of nine Sprague Dawley rats. The arthritic knee joint as well as the contralateral normal knee were investigated in a 2 Tesla MR scanner before as well as in short intervals up to 2 h after USPIO injection, using T1-weighted gradient echo (GE) sequences. Three rats each received intravenous injections of the new USPIO SHU 555 C (SH U 555 C, Schering AG, Berlin) at doses of 40, 100 and 200 micromol Fe/kg. Pulse sequence parameters of the GE-sequence were optimized by varying flip angles (alpha) and echo times (TE). Changes in signal intensities (SI) of the arthritic knee and contralateral normal knee were quantified as DeltaSI (%) = /([SIpost - SIpre] / SIpre) x 100 %/ and compared with histopathology. RESULTS: Histology of the arthritic knees demonstrated a marked inflammatory proliferation of the synovium. The USPIO SH U 555 C caused a significant increase in signal intensity of the arthritic joints on T1-weighted MR images (p < 0.05). This effect was optimized using a flip angle of 60-70 degrees, a minimal TE and a dose of 200 micromol Fe/kg. Visually the contralateral normal knee did not show any USPIO enhancement. CONCLUSION: Inflammation can be depicted with marked T1 enhancement by the USPIO SH U 555 C using high contrast agent doses and optimized MR pulse sequence parameters.

Regulation of mesenchymal stem cell and chondrocyte differentiation by MIA.

Melanoma inhibitory activity (MIA), also referred to as cartilage-derived retinoic acid-sensitive protein (CD-RAP), an 11-kDa secreted protein, is mainly expressed in cartilaginous tissue during embryogenesis and adulthood. Currently, the function of MIA in cartilage tissue is not understood. Here, we describe that MIA acts as a chemotactic factor on the mesenchymal stem cell line C3H10T1/2, stimulating cell migration significantly at concentrations from 0.24 to 240 ng/ml, while inhibiting cell migration at higher doses of 2.4 microg/ml. When analyzing the role of MIA during differentiation processes, we show that MIA by itself is not capable to induce the differentiation of murine or human mesenchymal stem cells. However, MIA influences the action of bone morphogenetic protein (BMP)-2 and transforming growth factor (TGF)-beta 3 during mesenchymal stem cell differentiation, supporting the chondrogenic phenotype while inhibiting osteogenic differentiation. Quantitative RT-PCR analysis revealed the up-regulation of the cartilage markers MIA, collagen type II and aggrecan in human mesenchymal stem cell (HMSC) cultures differentiated in the presence of MIA and TGF-beta 3 or BMP-2 when compared to HMSC cultures differentiated in the presence of TGF-beta 3 or BMP-2 alone. Further, MIA down-regulates gene expression of osteopontin and osteocalcin in BMP-2 treated HMSC cultures inhibiting the osteogenic potential of BMP-2. In the case of human primary chondrocytes MIA stimulates extracellular matrix deposition, increasing the glycosaminoglycan content. Therefore, we postulate that MIA is an important regulator during chondrogenic differentiation and maintenance of cartilage.