Association between Body Mass Index and Medication-Overuse Headache among Individuals with Migraine: A Cross-Sectional Study.

INTRODUCTION: Medication-overuse headache (MOH) is a secondary chronic headache disorder that occurs in individuals with a pre-existing primary headache disorder, particularly migraine disorder. Obesity is often combined with chronic daily headaches and is considered a risk factor for the transformation of episodic headaches into chronic headaches. However, the association between obesity and MOH among individuals with migraine has rarely been studied. The present study explored the association between body mass index (BMI) and MOH in people living with migraine. METHODS: This cross-sectional study is a secondary analysis of data from the Survey of Fibromyalgia Comorbidity with Headache study. Migraine and MOH were diagnosed using the criteria of the International Classification of Headache Disorders, 3rd Edition. BMI (kg/m2) is calculated by dividing the weight (kg) by the square of the height (m). Multivariable logistic regression analysis was used to evaluate the association between BMI and MOH. RESULTS: A total of 2,251 individuals with migraine were included, of whom 8.7% (195/2,251) had a concomitant MOH. Multivariable logistic regression analysis, adjusted for age, sex, education level, headache duration, pain intensity, headache family history, chronic migraine, depression, anxiety, insomnia, and fibromyalgia, demonstrated there was an association between BMI (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.11; p = 0.031) and MOH. The results remained when the BMI was transformed into a category. Compared to individuals with Q2 (18.5 kg/m2 ≤ BMI ≤23.9 kg/m2), those with Q4 (BMI ≥28 kg/m2) had an adjusted OR for MOH of 1.81 (95% CI, 1.04-3.17; p = 0.037). In the subgroup analyses, BMI was associated with MOH among aged more than 50 years (OR, 1.13; 95%, 1.03-1.24), less than high school (OR, 1.08; 95%, 1.01-1.15), without depression (OR, 1.06; 95%, 1.01-1.12), and without anxiety (OR, 1.06; 95%, 1.01-1.12). An association between BMI and MOH was found in a sensitivity analysis that BMI was classified into four categories according to the World Health Organization guidelines. CONCLUSION: In this cross-sectional study, BMI was associated with MOH in Chinese individuals with migraine.

Status of diagnosis and preventative treatment for primary headache disorders: real-world data of unmet needs in China.

BACKGROUND: Headache disorders are widely prevalent and pose a considerable economic burden on individuals and society. Globally, misdiagnosis and inadequate treatment of primary headache disorders remain significant challenges, impeding the effective management of such conditions. Despite advancements in headache management over the last decade, a need for comprehensive evaluations of the status of primary headache disorders in China regarding diagnosis and preventative treatments persists. METHODS: In the present study, we analyzed the established queries in the Survey of Fibromyalgia Comorbidity with Headache (SEARCH), focusing on previous diagnoses and preventative treatment regimens for primary headache disorders. This cross-sectional study encompassed adults diagnosed with primary headache disorders who sought treatment at 23 hospitals across China between September 2020 to May 2021. RESULTS: The study comprised 2,868 participants who were systematically examined. Migraine and tension-type headaches (TTH) constituted a majority of the primary headache disorders, accounting for 74.1% (2,124/2,868) and 23.3% (668/2,868) of the participants, respectively. Medication overuse headache (MOH) affected 8.1% (231/2,868) of individuals with primary headache disorders. Over half of the individuals with primary headache disorders (56.6%, 1,624/2,868) remained undiagnosed. The previously correct diagnosis rates for migraine, TTH, TACs, and MOH were 27.3% (580/2,124), 8.1% (54/668), 23.2% (13/56), and 3.5% (8/231), respectively. The misdiagnosis of "Nervous headache" was found to be the most prevalent among individuals with migraine (9.9%, 211/2,124), TTH (10.0%, 67/668), trigeminal autonomic cephalalgias (TACs) (17.9%, 10/56), and other primary headache disorders (10.0%, 2/20) respectively. Only a minor proportion of individuals with migraine (16.5%, 77/468) and TTH (4.7%, 2/43) had received preventive medication before participating in the study. CONCLUSIONS: While there has been progress made in the rate of correct diagnosis of primary headache disorders in China compared to a decade ago, the prevalence of misdiagnosis and inadequate treatment of primary headaches remains a veritable issue. As such, focused efforts are essential to augment the diagnosis and preventive treatment measures related to primary headache disorders in the future.

Mitochondria Transplantation from Stem Cells for Mitigating Sarcopenia.

Sarcopenia is defined as the age-related loss of muscle mass and function that can lead to prolonged hospital stays and decreased independence. It is a significant health and financial burden for individuals, families, and society as a whole. The accumulation of damaged mitochondria in skeletal muscle contributes to the degeneration of muscles with age. Currently, the treatment of sarcopenia is limited to improving nutrition and physical activity. Studying effective methods to alleviate and treat sarcopenia to improve the quality of life and lifespan of older people is a growing area of interest in geriatric medicine. Therapies targeting mitochondria and restoring mitochondrial function are promising treatment strategies. This article provides an overview of stem cell transplantation for sarcopenia, including the mitochondrial delivery pathway and the protective role of stem cells. It also highlights recent advances in preclinical and clinical research on sarcopenia and presents a new treatment method involving stem cell-derived mitochondrial transplantation, outlining its advantages and challenges.

Increased iron deposition in nucleus accumbens associated with disease progression and chronicity in migraine.

BACKGROUND: Migraine is one of the world's most prevalent and disabling diseases. Despite huge advances in neuroimaging research, more valuable neuroimaging markers are still urgently needed to provide important insights into the brain mechanisms that underlie migraine symptoms. We therefore aim to investigate the regional iron deposition in subcortical nuclei of migraineurs as compared to controls and its association with migraine-related pathophysiological assessments. METHODS: A total of 200 migraineurs (56 chronic migraine [CM], 144 episodic migraine [EM]) and 41 matched controls were recruited. All subjects underwent MRI and clinical variables including frequency/duration of migraine, intensity of migraine, 6-item Headache Impact Test (HIT-6), Migraine Disability Assessment (MIDAS), and Pittsburgh Sleep Quality Index (PSQI) were recorded. Quantitative susceptibility mapping was employed to quantify the regional iron content in subcortical regions. Associations between clinical variables and regional iron deposition were studied as well. RESULTS: Increased iron deposition in the putamen, caudate, and nucleus accumbens (NAC) was observed in migraineurs more than controls. Meanwhile, patients with CM had a significantly higher volume of iron deposits compared to EM in multiple subcortical nuclei, especially in NAC. Volume of iron in NAC can be used to distinguish patients with CM from EM with a sensitivity of 85.45% and specificity of 71.53%. As the most valuable neuroimaging markers in all of the subcortical nuclei, higher iron deposition in NAC was significantly associated with disease progression, and higher HIT-6, MIDAS, and PSQI. CONCLUSIONS: These findings provide evidence that iron deposition in NAC may be a biomarker for migraine chronicity and migraine-related dysfunctions, thus may help to understand the underlying vascular and neural mechanisms of migraine. TRIAL REGISTRATION: ClinicalTrials.gov, number NCT04939922.

The prevalence and clinical features of fibromyalgia in Chinese hospital patients with primary headache: The survey of fibromyalgia comorbid with headache.

OBJECTIVE: The aims were to explore the prevalence and clinical features of fibromyalgia in Chinese hospital patients with primary headache. BACKGROUND: Studies done in non-Chinese populations suggest that around one-third of patients with primary headache have fibromyalgia, but data from mainland China are limited. Investigations into the prevalence and clinical features of fibromyalgia in Chinese patients with primary headache would improve our understanding of these two complex disease areas and help guide future clinical practice. METHODS: This cross-sectional study included adults with primary headache treated at 23 Chinese hospitals from September 2020 to May 2021. Fibromyalgia was diagnosed using the modified 2010 American College of Rheumatology criteria. Mood and insomnia were evaluated employing the Hospital Anxiety and Depression Scale and the Insomnia Severity Index. RESULTS: A total of 2782 participants were analyzed. The fibromyalgia prevalence was 6.0% (166/2782; 95% confidence interval: 5.1%, 6.8%). Compared to primary headache patients without combined fibromyalgia, patients with primary headache combined with fibromyalgia were more likely to be older (47.8 vs. 41.7 years), women (83.7% [139/166] vs. 72.8% [1904/2616]), less educated (65.1% [108/166] vs. 45.2% [1183/2616]), and with longer-duration headache (10.0 vs. 8.0 years). Such patients were more likely to exhibit comorbid depression (34.3% [57/166] vs. 9.9% [260/2616]), anxiety (16.3% [27/166] vs. 2.7% [70/2612]), and insomnia (58.4% [97/166] vs. 17.1% [447/2616]). Fibromyalgia was more prevalent in those with chronic (rather than episodic) migraine (11.1% [46/414] vs. 4.4% [72/1653], p < 0.001) and chronic (rather than episodic) tension-type headache (11.5% [27/235] vs. 4.6% [19/409], p = 0.001). Most fibromyalgia pain was in the shoulders, neck, and upper back. CONCLUSIONS: The prevalence of fibromyalgia in mainland Chinese patients with primary headache was 6.0%. Fibromyalgia was more common in those with chronic rather than episodic headache. The most common sites of fibromyalgia pain were the neck, shoulders, and back.

Stem cell-derived mitochondria transplantation: A promising therapy for mitochondrial encephalomyopathy.

Mitochondrial encephalomyopathies are disorders caused by mitochondrial and nuclear DNA mutations which affect the nervous and muscular systems. Current therapies for mitochondrial encephalomyopathies are inadequate and mostly palliative. However, stem cell-derived mitochondria transplantation has been demonstrated to play an key part in metabolic rescue, which offers great promise for mitochondrial encephalomyopathies. Here, we summarize the present status of stem cell therapy for mitochondrial encephalomyopathy and discuss mitochondrial transfer routes and the protection mechanisms of stem cells. We also identify and summarize future perspectives and challenges for the treatment of these intractable disorders based on the concept of mitochondrial transfer from stem cells.

A Case of Recurrent Painful Ophthalmoplegic Neuropathy.

Ophthalmoplegic migraine (OM) is characterized by recurrent episodes of headache with unilateral ophthalmoplegia due to paresis of cranial nerve III, IV, or VI. The recent revision to the International Headache Classification has reclassified it as recurrent painful ophthalmoplegic neuropathy (RPON). However, it is of note that the presentation of oculomotor nerve tumors may mimic RPON. Here, we report the case of a patient presenting with recurrent migraine and oculomotor palsy with several specific magnetic resonance imaging (MRI) findings. The patient was initially diagnosed with migraine 15 years ago, but since 10 years ago, his symptoms had evolved to include repeated oculomotor paralyzes. Before this attack, the patient did eventually recover completely each time after the initial episode. MRI performed during this attack revealed a nodular enhancing lesion described as schwannoma of the left oculomotor nerve, and on diffusion-weighted imaging (DWI), the nerve was isointense to the midbrain. The nodular enhancement became weaker, and the nerve's signal on DWI disappeared 3 months later as the patient's symptoms resolved mostly. This is the first case of RPON demonstrating an obvious change in signal of the affected nerve on DWI during the attack and remission.

Mesenchymal stem cells transfer mitochondria into cerebral microvasculature and promote recovery from ischemic stroke.

Mesenchymal stem cells can be used as a novel treatment of ischemic stroke, but their therapeutic effect and mechanism of action require further evaluation. Mitochondrial dysfunction has core functions in ischemia-reperfusion stroke injury. Our recent research has demonstrated that mesenchymal stem cells can transfer their functional mitochondria to injured endothelial cells via tunneling nanotubes in vitro, resulting in the rescue of aerobic respiration and protection of endothelial cells from apoptosis. Therefore, we presume that the mechanisms of mitochondrial protection may be involved in stem cell-mediated rescue of injured cerebral microvasculature and recovery from ischemic stroke. In this study, the middle cerebral artery occlusion and reperfusion surgery were conducted on rats, and mesenchymal stem cells were then engrafted into the injured cerebrovascular system. Our results showed that the host cells of injured cerebral microvasculature accepted the mitochondria transferred from the transplanted stem cells, thereby resulting in significantly improving in mitochondrial activity of injured microvasculature, enhancing angiogenesis, reducing infarct volume, and improving functional recovery. Our data provided the evidence that stem cells can rescue damaged cerebrovascular system in stroke through a mechanism not yet identified.

A fiber optoacoustic guide with augmented reality for precision breast-conserving surgery.

Lumpectomy, also called breast-conserving surgery, has become the standard surgical treatment for early-stage breast cancer. However, accurately locating the tumor during a lumpectomy, especially when the lesion is small and nonpalpable, is a challenge. Such difficulty can lead to either incomplete tumor removal or prolonged surgical time, which result in high re-operation rates (~25%) and increased surgical costs. Here, we report a fiber optoacoustic guide (FOG) with augmented reality (AR) for sub-millimeter tumor localization and intuitive surgical guidance with minimal interference. The FOG is preoperatively implanted in the tumor. Under external pulsed light excitation, the FOG omnidirectionally broadcasts acoustic waves through the optoacoustic effect by a specially designed nano-composite layer at its tip. By capturing the acoustic wave, three ultrasound sensors on the breast skin triangulate the FOG tip's position with 0.25-mm accuracy. An AR system with a tablet measures the coordinates of the ultrasound sensors and transforms the FOG tip's position into visual feedback with <1-mm accuracy, thus aiding surgeons in directly visualizing the tumor location and performing fast and accurate tumor removal. We further show the use of a head-mounted display to visualize the same information in the surgeons' first-person view and achieve hands-free guidance. Towards clinical application, a surgeon successfully deployed the FOG to excise a "pseudo tumor" in a female human cadaver. With the high-accuracy tumor localization by FOG and the intuitive surgical guidance by AR, the surgeon performed accurate and fast tumor removal, which will significantly reduce re-operation rates and shorten the surgery time.

Role of S-Palmitoylation by ZDHHC13 in Mitochondrial function and Metabolism in Liver.

Palmitoyltransferase (PAT) catalyses protein S-palmitoylation which adds 16-carbon palmitate to specific cysteines and contributes to various biological functions. We previously reported that in mice, deficiency of Zdhhc13, a member of the PAT family, causes severe phenotypes including amyloidosis, alopecia, and osteoporosis. Here, we show that Zdhhc13 deficiency results in abnormal liver function, lipid abnormalities, and hypermetabolism. To elucidate the molecular mechanisms underlying these disease phenotypes, we applied a site-specific quantitative approach integrating an alkylating resin-assisted capture and mass spectrometry-based label-free strategy for studying the liver S-palmitoylome. We identified 2,190 S-palmitoylated peptides corresponding to 883 S-palmitoylated proteins. After normalization using the membrane proteome with TMT10-plex labelling, 400 (31%) of S-palmitoylation sites on 254 proteins were down-regulated in Zdhhc13-deficient mice, representing potential ZDHHC13 substrates. Among these, lipid metabolism and mitochondrial dysfunction proteins were overrepresented. MCAT and CTNND1 were confirmed to be specific ZDHHC13 substrates. Furthermore, we found impaired mitochondrial function in hepatocytes of Zdhhc13-deficient mice and Zdhhc13-knockdown Hep1-6 cells. These results indicate that ZDHHC13 is an important regulator of mitochondrial activity. Collectively, our study allows for a systematic view of S-palmitoylation for identification of ZDHHC13 substrates and demonstrates the role of ZDHHC13 in mitochondrial function and metabolism in liver.

Protein Palmitoylation by ZDHHC13 Protects Skin against Microbial-Driven Dermatitis.

Atopic dermatitis is a complex chronic inflammatory skin disorder that results from intimate interactions among genetic predisposition, host environment, skin barrier defects, and immunological factors. However, a clear genetic roadmap leading to atopic dermatitis remains to be fully explored. From a genome-wide mutagenesis screen, deficiency of ZDHHC13, a palmitoylacyl transferase, has previously been associated with skin and multitissue inflammatory phenotypes. Here, we report that ZDHHC13 is required for skin barrier integrity and that deficiency of ZDHHC13 renders mice susceptible to environmental bacteria, resulting in persistent skin inflammation and an atopic dermatitis-like disease. This phenotype is ameliorated in a germ-free environment and is also attenuated by antibiotic treatment, but not by deletion of the Rag1 gene, suggesting that a microbial factor triggers inflammation rather than intrinsic adaptive immunity. Furthermore, skin from ZDHHC13-deficient mice has both elevated levels of IL-33 and type 2 innate lymphoid cells, reinforcing the role of innate immunity in the development of atopic dermatitis. In summary, our study suggests that loss of ZDHHC13 in skin impairs the integrity of multiple barrier functions and leads to a dermatitis lesion in response to microbial encounters.

Cyclic Alopecia and Abnormal Epidermal Cornification in Zdhhc13-Deficient Mice Reveal the Importance of Palmitoylation in Hair and Skin Differentiation.

Many biochemical pathways involved in hair and skin development have not been investigated. Here, we reported on the lesions and investigated the mechanism underlying hair and skin abnormalities in Zdhhc13(skc4) mice with a deficiency in DHHC13, a palmitoyl-acyl transferase encoded by Zdhhc13. Homozygous affected mice showed ragged and dilapidated cuticle of the hair shaft (CUH, a hair anchoring structure), poor hair anchoring ability, and premature hair loss at early telogen phase of the hair cycle, resulting in cyclic alopecia. Furthermore, the homozygous affected mice exhibited hyperproliferation of the epidermis, disturbed cornification, fragile cornified envelope (CE, a skin barrier structure), and impaired skin barrier function. Biochemical investigations revealed that cornifelin, which contains five palmitoylation sites at cysteine residues (C58, C59, C60, C95, and C101), was a specific substrate of DHHC13 and that it was absent in the CUH and CE structures of the affected mice. Furthermore, cornifelin levels were markedly reduced when two palmitoylated cysteines were replaced with serine (C95S and C101S). Taken together, our results suggest that DHHC13 is important for hair anchoring and skin barrier function and that cornifelin deficiency contributes to cyclic alopecia and skin abnormalities in Zdhhc13(skc4) mice.

Palmitoyl acyltransferase, Zdhhc13, facilitates bone mass acquisition by regulating postnatal epiphyseal development and endochondral ossification: a mouse model.

ZDHHC13 is a member of DHHC-containing palmitoyl acyltransferases (PATs) family of enzymes. It functions by post-translationally adding 16-carbon palmitate to proteins through a thioester linkage. We have previously shown that mice carrying a recessive Zdhhc13 nonsense mutation causing a Zdhcc13 deficiency develop alopecia, amyloidosis and osteoporosis. Our goal was to investigate the pathogenic mechanism of osteoporosis in the context of this mutation in mice. Body size, skeletal structure and trabecular bone were similar in Zdhhc13 WT and mutant mice at birth. Growth retardation and delayed secondary ossification center formation were first observed at day 10 and at 4 weeks of age, disorganization in growth plate structure and osteoporosis became evident in mutant mice. Serial microCT from 4-20 week-olds revealed that Zdhhc13 mutant mice had reduced bone mineral density. Through co-immunoprecipitation and acyl-biotin exchange, MT1-MMP was identified as a direct substrate of ZDHHC13. In cells, reduction of MT1-MMP palmitoylation affected its subcellular distribution and was associated with decreased VEGF and osteocalcin expression in chondrocytes and osteoblasts. In Zdhhc13 mutant mice epiphysis where MT1-MMP was under palmitoylated, VEGF in hypertrophic chondrocytes and osteocalcin at the cartilage-bone interface were reduced based on immunohistochemical analyses. Our results suggest that Zdhhc13 is a novel regulator of postnatal skeletal development and bone mass acquisition. To our knowledge, these are the first data to suggest that ZDHHC13-mediated MT1-MMP palmitoylation is a key modulator of bone homeostasis. These data may provide novel insights into the role of palmitoylation in the pathogenesis of human osteoporosis.

Mesenchymal stem cells rescue injured endothelial cells in an in vitro ischemia-reperfusion model via tunneling nanotube like structure-mediated mitochondrial transfer.

Mesenchymal stem cells can be used as a novel treatment of ischemic vascular disease; however, their therapeutic effect and mechanism of action require further evaluation. Mitochondrial dysfunction has core functions in ischemia-reperfusion injury of the microvascular network. A recent discovery has shown that intercellular communication using tunneling nanotubes can transfer mitochondria between adjacent cells. This study aimed to investigate the tunneling nanotube mechanisms that might be involved in stem cell-mediated mitochondrial rescue of injured vascular endothelial cells. Using laser scanning confocal microscopy, mitochondrial transfer via a tunneling nanotube-like structure was detected between mesenchymal stem cells and human umbilical vein endothelial cells. Oxygen glucose deprivation and reoxygenation were performed on human umbilical vein endothelial cells, which induced mitochondrial transfer through tunneling nanotube-like structures to become frequent and almost unidirectional from mesenchymal stem cells to injured endothelial cells, thereby resulting in the rescue of aerobic respiration and protection of endothelial cells from apoptosis. We found that the formation of tunneling nanotube-like structures might represent a defense and rescue mechanism through phosphatidylserines exposed on the surface of apoptotic endothelial cells and stem cell recognition. Our data provided evidence that stem cells can rescue damaged vascular endothelial cells through a mechanism that has not yet been identified.

MERRF/MELAS overlap syndrome due to the m.3291T>C mutation.

We report the case of a 19-year-old Chinese female harboring the m.3291T>C mutation in the MT-TL1 gene encoding the mitochondrial transfer RNA for leucine. She presented with a complex phenotype characterized by progressive cerebellar ataxia, frequent myoclonus seizures, recurrent stroke-like episodes, migraine-like headaches with nausea and vomiting, and elevated resting lactate blood level. It is known that the myoclonus epilepsy with ragged-red fibers (MERRF) is characterized by cerebellar ataxia and myoclonus epilepsy, while that the mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is characterized by recurrent stroke-like episodes, migraine-like headaches, and elevated resting lactate blood level. So the patient's clinical manifestations suggest the presence of a MERRF/MELAS overlap syndrome. Muscle biopsy of the patient showed the presence of numerous scattered ragged-red fibers, some cytochrome c oxidase-deficient fibers, and several strongly succinate dehygrogenase-reactive vessels, suggestive of a mitochondrial disorder. Direct sequencing of the complete mitochondrial genome of the proband revealed no mutations other than the T-to-C transition at nucleotide position 3291. Restriction fragment length polymorphism analysis of the proband and her family revealed maternal inheritance of the mutation in a heteroplasmic manner. The analysis of aerobic respiration and glycolysis demonstrated that the fibroblasts from the patient had mitochondrial dysfunction. Our results suggest that the m.3291T>C is pathogenic. This study is the first to describe the m.3291T>C mutation in association with the MERRF/MELAS overlap syndrome.

Mice with alopecia, osteoporosis, and systemic amyloidosis due to mutation in Zdhhc13, a gene coding for palmitoyl acyltransferase.

Protein palmitoylation has emerged as an important mechanism for regulating protein trafficking, stability, and protein-protein interactions; however, its relevance to disease processes is not clear. Using a genome-wide, phenotype driven N-ethyl-N-nitrosourea-mediated mutagenesis screen, we identified mice with failure to thrive, shortened life span, skin and hair abnormalities including alopecia, severe osteoporosis, and systemic amyloidosis (both AA and AL amyloids depositions). Whole-genome homozygosity mapping with 295 SNP markers and fine mapping with an additional 50 SNPs localized the disease gene to chromosome 7 between 53.9 and 56.3 Mb. A nonsense mutation (c.1273A>T) was located in exon 12 of the Zdhhc13 gene (Zinc finger, DHHC domain containing 13), a gene coding for palmitoyl transferase. The mutation predicted a truncated protein (R425X), and real-time PCR showed markedly reduced Zdhhc13 mRNA. A second gene trap allele of Zdhhc13 has the same phenotypes, suggesting that this is a loss of function allele. This is the first report that palmitoyl transferase deficiency causes a severe phenotype, and it establishes a direct link between protein palmitoylation and regulation of diverse physiologic functions where its absence can result in profound disease pathology. This mouse model can be used to investigate mechanisms where improper palmitoylation leads to disease processes and to understand molecular mechanisms underlying human alopecia, osteoporosis, and amyloidosis and many other neurodegenerative diseases caused by protein misfolding and amyloidosis.

The interactions between brain microvascular endothelial cells and mesenchymal stem cells under hypoxic conditions.

The purpose of the present study was to investigate the interactions between brain microvascular endothelial cells (BMEC) and mesenchymal stem cells (MSC) under hypoxic conditions. Primary cultured human bone marrow MSC and rat BMEC were isolated, cultured and identified. Vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) were detected in the conditioned media of BMEC and MSC under normal and hypoxic conditions using ELISA. MSC differentiation was analyzed using flow cytometry and fluorescence immunocytochemistry. Transendothelial electrical resistance (TEER) techniques were employed to measure changes in permeability across the BMEC monolayer. Under hypoxic conditions, the concentration of VEGF and MMP-9 in the conditioned media increased significantly, with greater levels in the MSC than the BMEC media. Primary MSC did not express vWF and Flk-1. MSC were co-cultured with BMEC under hypoxic conditions 5 days later. MSC expressing Flk-1 accounted for 23.64+/-2.50% (n=6, P<0.001) of the total number of cells. Interestingly, some Flk-1 positive cells began to coexpress vWF simultaneously. Under hypoxic conditions, MSC conditioned media significantly enhanced the proliferation and migration of BMEC. In addition, MSC decreased the TEER of the BMEC monolayer (lowest values: 50.5+/-2.6% of the original), which could partially be inhibited by both anti-VEGF antibody and MMP-9 inhibitor. These data indicate that under hypoxic conditions BMEC induce MSC to differentiate into endothelial cells, and MSC enhance the proliferation and migration of BMEC through paracrine functions, while simultaneously increasing the permeability of the BMEC monolayer.