Melatonin protects Kir2.1 function in an oxidative stress-related model of aging neuroglia.

Melatonin is a pleiotropic biofactor and an effective antioxidant and free radical scavenger and, as such, can be protective in oxidative stress-related brain conditions including epilepsy and aging. To test the potential protective effect of melatonin on brain homeostasis and identify the corresponding molecular targets, we established a new model of oxidative stress-related aging neuroglia represented by U-87 MG cells exposed to D-galactose (D-Gal). This model was characterized by a substantial elevation of markers of oxidative stress, lipid peroxidation, and protein oxidation. The function of the inward rectifying K+ channel Kir2.1, which was identified as the main Kir channel endogenously expressed in these cells, was dramatically impaired. Kir2.1 was unlikely a direct target of oxidative stress, but the loss of function resulted from a reduction of protein abundance, with no alterations in transcript levels and trafficking to the cell surface. Importantly, melatonin reverted these changes. All findings, including the melatonin antioxidant effect, were reproduced in heterologous expression systems. We conclude that the glial Kir2.1 can be a target of oxidative stress and further suggest that inhibition of its function might alter the extracellular K+ buffering in the brain, therefore contributing to neuronal hyperexcitability and epileptogenesis during aging. Melatonin can play a protective role in this context.

Distinct ClC-6 and ClC-7 Cl- sensitivities provide insight into ClC-7's role in lysosomal Cl- homeostasis.

ClC-6 and ClC-7 are closely related, intracellular Cl- /H+ antiporters belonging to the CLC family of channels and transporters. They localize to acidic late endosomes and lysosomes and probably function in ionic homeostasis of these contiguous compartments. ClC-7 transport function requires association with the accessory protein Ostm1, whereas ClC-6 transport does not. To elucidate their roles in endo-lysosomes, we measured Cl- - and pH-dependences of over-expressed wild-type ClC-6 and ClC-7, as well as disease-associated mutants, using high-resolution recording protocols. Lowering extracellular Cl- (corresponding to luminal Cl- in endo-lysosomes) reduced ClC-6 currents, whereas it increased transport activity of ClC-7/Ostm1. Low extracellular Cl- activated ClC-7/Ostm 1 under acidic extracellular conditions, as well as under conditions of low intracellular chloride. Activation is conserved in ClC-7Y713C , a variant displaying disrupted PI(3,5)P2 inhibition. Detailed biophysical analysis of disease-associated ClC-6 and ClC-7 gain-of-function (GoF) variants, ClC-6Y553C and ClC-7Y713C , and the ClC-7Y577C and ClC-6Y781C correlates, identified additional functional nuances distinguishing ClC-6 and ClC-7. ClC-7Y577C recapitulated GoF produced by ClC-6Y553C . ClC-6Y781C displayed transport activation qualitatively similar to ClC-7Y713C , although current density did not differ from that of wild-type ClC-6. Finally, rClC-7R760Q , homologous to hClC-7R762Q , an osteopetrosis variant with fast gating kinetics, appeared indifferent to extracellular Cl- , identifying altered Cl- sensitivity as a plausible mechanism underlying disease. Collectively, the present studies underscore the distinct roles of ClC-6 and ClC-7 within the context of their respective localization to late endosomes and lysosomes. In particular, we suggest the atypical inhibition of ClC-7 by luminal Cl- serves to limit excessive intraluminal Cl- accumulation. KEY POINTS: ClC-6 and ClC-7 are late endosomal and lysosomal 2 Cl- /1 H+ exchangers, respectively. When targeted to the plasma membrane, both activate slowly at positive voltages. ClC-6 activity is decreased in low extracellular (i.e. luminal) chloride, whereas ClC-7 is activated by low luminal chloride, even at acidic pH. The functional gain-of-function phenotypes of the ClC-6 and ClC-7 disease mutations ClC-6Y553C and ClC-7Y715C are maintained when introduced in their respective homologues, ClC-7Y577C and ClC-6Y781C , with all mutations retaining chloride dependence of the respective wild type (WT). An osteopetrosis mutation of ClC-7 displaying fast gating kinetics (R762Q) was less sensitive to extracellular chloride compared to WT. The opposing substrate dependences of ClC-6 and ClC-7 Cl- / H+ exchangers point to non-overlapping physiological functions, leading us to propose that inhibition of ClC-7 by luminal chloride and protons serves to prevent osmotic stress imposed by hyper-accumulation of chloride.

IK Channel-Independent Effects of Clotrimazole and Senicapoc on Cancer Cells Viability and Migration.

Many studies highlighted the importance of the IK channel for the proliferation and the migration of different types of cancer cells, showing how IK blockers could slow down cancer growth. Based on these data, we wanted to characterize the effects of IK blockers on melanoma metastatic cells and to understand if such effects were exclusively IK-dependent. For this purpose, we employed two different blockers, namely clotrimazole and senicapoc, and two cell lines: metastatic melanoma WM266-4 and pancreatic cancer Panc-1, which is reported to have little or no IK expression. Clotrimazole and senicapoc induced a decrease in viability and the migration of both WM266-4 and Panc-1 cells irrespective of IK expression levels. Patch-clamp experiments on WM266-4 cells revealed Ca2+-dependent, IK-like, clotrimazole- and senicapoc-sensitive currents, which could not be detected in Panc-1 cells. Neither clotrimazole nor senicapoc altered the intracellular Ca2+ concentration. These results suggest that the effects of IK blockers on cancer cells are not strictly dependent on a robust presence of the channel in the plasma membrane, but they might be due to off-target effects on other cellular targets or to the blockade of IK channels localized in intracellular organelles.

Biophysical Aspects of Neurodegenerative and Neurodevelopmental Disorders Involving Endo-/Lysosomal CLC Cl-/H+ Antiporters.

Endosomes and lysosomes are intracellular vesicular organelles with important roles in cell functions such as protein homeostasis, clearance of extracellular material, and autophagy. Endolysosomes are characterized by an acidic luminal pH that is critical for proper function. Five members of the gene family of voltage-gated ChLoride Channels (CLC proteins) are localized to endolysosomal membranes, carrying out anion/proton exchange activity and thereby regulating pH and chloride concentration. Mutations in these vesicular CLCs cause global developmental delay, intellectual disability, various psychiatric conditions, lysosomal storage diseases, and neurodegeneration, resulting in severe pathologies or even death. Currently, there is no cure for any of these diseases. Here, we review the various diseases in which these proteins are involved and discuss the peculiar biophysical properties of the WT transporter and how these properties are altered in specific neurodegenerative and neurodevelopmental disorders.

Voltage-Gated Sodium Channel Dysfunctions in Neurological Disorders.

The pore-forming subunits (α subunits) of voltage-gated sodium channels (VGSC) are encoded in humans by a family of nine highly conserved genes. Among them, SCN1A, SCN2A, SCN3A, and SCN8A are primarily expressed in the central nervous system. The encoded proteins Nav1.1, Nav1.2, Nav1.3, and Nav1.6, respectively, are important players in the initiation and propagation of action potentials and in turn of the neural network activity. In the context of neurological diseases, mutations in the genes encoding Nav1.1, 1.2, 1.3 and 1.6 are responsible for many forms of genetic epilepsy and for Nav1.1 also of hemiplegic migraine. Several pharmacological therapeutic approaches targeting these channels are used or are under study. Mutations of genes encoding VGSCs are also involved in autism and in different types of even severe intellectual disability (ID). It is conceivable that in these conditions their dysfunction could indirectly cause a certain level of neurodegenerative processes; however, so far, these mechanisms have not been deeply investigated. Conversely, VGSCs seem to have a modulatory role in the most common neurodegenerative diseases such as Alzheimer's, where SCN8A expression has been shown to be negatively correlated with disease severity.

Molecular determinants underlying volume-regulated anion channel subunit-dependent oxidation sensitivity.

The volume-regulated anion channel (VRAC) is formed by LRRC8 subunits. Besides their role in the maintenance of cell homeostasis, VRACs are critically involved in oxidative stress mechanisms: reactive oxygen species directly modulate VRACs in a subunit-dependent manner. It was reported that LRRC8A-LRRC8E heteromeric channels are activated by oxidation, whereas LRRC8A-LRRC8C heteromers are inhibited. Here we adopted chimeric- as well as concatemeric-based strategies to identify residues responsible for the divergent effect of oxidants. We identified two cysteines in the first two leucine rich repeats of LRRC8E, C424 and C448, as the targets of oxidation. Oxidation likely results in the formation of a disulfide bond between the two cysteines, which in turn induces a conformational change leading to channel activation. Additionally, we found that LRRC8C inhibition is caused by oxidation of the first methionine. We thus identified crucial molecular elements involved in channel activation, which are conceivably relevant in determining physiological ROS effects. KEY POINTS: Volume-regulated anion channels (VRACs) are heterohexameric complexes composed of an essential LRRC8A subunit and a variable number of LRRC8B-E subunits. VRACs are directly regulated by oxidation, with LRRC8A-LRRC8E heteromers being potentiated and LRRC8A-LRRC8C heteromers being inhibited by oxidation. We identified two LRRC8E specific intracellular cysteines that form a disulfide bond upon oxidation leading to LRRC8A-LRRC8E potentiation. Inhibition of LRRC8A-LRRC8C heteromers is mediated by the oxidation of the start methionine, being additionally dependent on the identity of the LRR domain. Besides providing physiological insights concerning the outcome of reactive oxygen species modulation, the results point to key structural elements involved in VRAC activation.

BK Channel in the Physiology and in the Cancer of Pancreatic Duct: Impact and Reliability of BK Openers.

BK (KCa 1.1, Slo-1) is a K+ channel characterized by an allosteric regulation of the gating mechanism by Ca2+ binding and voltage, and a high unitary conductance. The channel is expressed in many different tissues, where it is involved in the regulation or the fine-tuning of many physiological processes. Among other organs, BK is expressed in the pancreatic duct, a part of the gland important for the correct ionic composition of the pancreatic juice. Unfortunately, the pancreatic duct is also the site where one of the deadliest cancer types, the pancreatic duct adenocarcinoma (PDAC), develops. In the past years, it has been reported that continuous exposure of cancer cells to BK openers can have a significant impact on cell viability as well as on the ability to proliferate and migrate. Here, we first summarize the main BK channel properties and its roles in pancreatic duct physiology. Then we focus on the potential role of BK as a pharmacological target in PDAC. Moreover, we discuss how results obtained when employing BK activators on cancer cells can, in some cases, be misleading.

Is Neuronal Fatigue the Cause of Migraine?

The pathological basis of migraine is not fully understood. Familial hemiplegic migraines (FHM) are monogenic forms of severe migraine, caused by mutations in genes encoding various neuronal and/or astrocytic ion transporting proteins. The leading hypothesis regarding the mechanism underlying migraine in FHM is that enhanced electrical excitability leads to increased extracellular potassium levels with subsequent cortical spreading depression. In this short commentary we would like to propose an additional mechanism distinct from enhanced electrical excitability per se. Rather, we propose that FHM mutations cause substantially increased energy expenditure of neurons for re-establishing ion gradients and/or for increased synaptic activity, a mechanism we call neuronal fatigue. Such a metabolic mechanism had been proposed earlier for common migraine and has received recent experimental evidence in particular for the case of FHM3. The hypothesis could be tested in future studies of FHM related models that would need to take metabolic parameters into account.

Ion Channel Involvement in Tumor Drug Resistance.

Over 90% of deaths in cancer patients are attributed to tumor drug resistance. Resistance to therapeutic agents can be due to an innate property of cancer cells or can be acquired during chemotherapy. In recent years, it has become increasingly clear that regulation of membrane ion channels is an important mechanism in the development of chemoresistance. Here, we review the contribution of ion channels in drug resistance of various types of cancers, evaluating their potential in clinical management. Several molecular mechanisms have been proposed, including evasion of apoptosis, cell cycle arrest, decreased drug accumulation in cancer cells, and activation of alternative escape pathways such as autophagy. Each of these mechanisms leads to a reduction of the therapeutic efficacy of administered drugs, causing more difficulty in cancer treatment. Thus, targeting ion channels might represent a good option for adjuvant therapies in order to counteract chemoresistance development.

The VRAC blocker DCPIB directly gates the BK channels and increases intracellular Ca2+ in melanoma and pancreatic duct adenocarcinoma cell lines.

BACKGROUND AND PURPOSE: The volume regulated anion channel (VRAC) is known to be involved in different aspects of cancer cell behaviour and response to therapies. For this reason, we investigated the effect of DCPIB, a presumably specific blocker of VRAC, in two types of cancer: pancreatic duct adenocarcinoma (PDAC) and melanoma. EXPERIMENTAL APPROACH: We used patch-clamp electrophysiology, supported by Ca2+ imaging, gene expression analysis, docking simulation and mutagenesis. We employed two PDAC lines (Panc-1 and MiaPaCa-2), as well as a primary (IGR39) and a metastatic (IGR37) melanoma line. KEY RESULTS: DCPIB markedly increased whole-cell currents in Panc-1, MiaPaca2 and IGR39, but not in IGR37 cells. The currents were mostly mediated by KCa 1.1 channels, commonly known as BK channels. We confirmed DCPIB activation of BK channels also in HEK293 cells transfected with α subunits of this channel. Further experiments showed that in IGR39, and to a smaller degree also in Panc-1 cells, DCPIB induced a rapid Ca2+ influx. This, in turn, indirectly potentiated BK channels and, in IGR39 cells, additionally activated other Ca2+ -dependent channels. However, Ca2+ influx was not required for activation of BK channels by DCPIB, as such activation involved the extracellular part of the protein and we have identified a residue crucial for binding. CONCLUSION AND IMPLICATIONS: DCPIB directly targeted BK channels and, also, acutely increased intracellular Ca2+ . Our findings extend the list of DCPIB effects that should be taken into consideration for future development of DCPIB-based modulators of ion channels and other membrane proteins.

NS-11021 Modulates Cancer-Associated Processes Independently of BK Channels in Melanoma and Pancreatic Duct Adenocarcinoma Cell Lines.

Potassium channels have emerged as regulators of carcinogenesis, thus introducing possible new therapeutic strategies in the fight against cancer. In particular, the large-conductance Ca2+-activated K+ channel, often referred to as BK channel, is involved in several cancer-associated processes. Here, we investigated the effects of different BK activators, NS-11021, NS-19504, and BMS-191011, in IGR39 (primary melanoma cell line) and Panc-1 (primary pancreatic duct carcinoma cell line), highly expressing the channel, and in IGR37 (metastatic melanoma cell line) that barely express BK. Our data showed that NS-11021 and NS-19504 potently activated BK channels in IGR39 and Panc-1 cells, while no effect on channel activation was detected in IGR37 cells. On the contrary, BK channel activator BMS-191011 was less effective. However, only NS-11021 showed significant effects in cancer-associated processes, such as cell survival, migration, and proliferation in these cancer cell lines. Moreover, NS-11021 led to an increase of intracellular Ca2+ concentration, independent of BK channel activation, thus complicating any interpretation of its role in the regulation of cancer-associated mechanisms. Overall, we conclude that the activation of the BK channel by itself is not sufficient to produce beneficial anti-cancer effects in the melanoma and PDAC cell lines examined. Importantly, our results raise an alarm flag regarding the use of presumably specific BK channel openers as anti-cancer agents.

Hyperexcitable interneurons trigger cortical spreading depression in an Scn1a migraine model.

Cortical spreading depression (CSD), a wave of depolarization followed by depression of cortical activity, is a pathophysiological process implicated in migraine with aura and various other brain pathologies, such as ischemic stroke and traumatic brain injury. To gain insight into the pathophysiology of CSD, we generated a mouse model for a severe monogenic subtype of migraine with aura, familial hemiplegic migraine type 3 (FHM3). FHM3 is caused by mutations in SCN1A, encoding the voltage-gated Na+ channel NaV1.1 predominantly expressed in inhibitory interneurons. Homozygous Scn1aL1649Q knock-in mice died prematurely, whereas heterozygous mice had a normal lifespan. Heterozygous Scn1aL1649Q knock-in mice compared with WT mice displayed a significantly enhanced susceptibility to CSD. We found L1649Q to cause a gain-of-function effect with an impaired Na+-channel inactivation and increased ramp Na+ currents leading to hyperactivity of fast-spiking inhibitory interneurons. Brain slice recordings using K+-sensitive electrodes revealed an increase in extracellular K+ in the early phase of CSD in heterozygous mice, likely representing the mechanistic link between interneuron hyperactivity and CSD initiation. The neuronal phenotype and premature death of homozygous Scn1aL1649Q knock-in mice was partially rescued by GS967, a blocker of persistent Na+ currents. Collectively, our findings identify interneuron hyperactivity as a mechanism to trigger CSD.

TRPM2 Oxidation Activates Two Distinct Potassium Channels in Melanoma Cells through Intracellular Calcium Increase.

Tumor microenvironments are often characterized by an increase in oxidative stress levels. We studied the response to oxidative stimulation in human primary (IGR39) or metastatic (IGR37) cell lines obtained from the same patient, performing patch-clamp recordings, intracellular calcium ([Ca2+]i) imaging, and RT-qPCR gene expression analysis. In IGR39 cells, chloramine-T (Chl-T) activated large K+ currents (KROS) that were partially sensitive to tetraethylammonium (TEA). A large fraction of KROS was inhibited by paxilline-a specific inhibitor of large-conductance Ca2+-activated BK channels. The TEA-insensitive component was inhibited by senicapoc-a specific inhibitor of the Ca2+-activated KCa3.1 channel. Both BK and KCa3.1 activation were mediated by an increase in [Ca2+]i induced by Chl-T. Both KROS and [Ca2+]i increase were inhibited by ACA and clotrimazole-two different inhibitors of the calcium-permeable TRPM2 channel. Surprisingly, IGR37 cells did not exhibit current increase upon the application of Chl-T. Expression analysis confirmed that the genes encoding BK, KCa3.1, and TRPM2 are much more expressed in IGR39 than in IGR37. The potassium currents and [Ca2+]i increase observed in response to the oxidizing agent strongly suggest that these three molecular entities play a major role in the progression of melanoma. Pharmacological targeting of either of these ion channels could be a new strategy to reduce the metastatic potential of melanoma cells, and could complement classical radio- or chemotherapeutic treatments.

Mechanisms of Activation of LRRC8 Volume Regulated Anion Channels.

Volume regulated anion channels (VRACs) are ubiquitously expressed in all vertebrate cells. Despite many years of research, the fundamental mechanisms underlying VRAC activation are not understood. The recent molecular identification of the LRRC8 genes underlying VRAC revealed that VRACs are formed by a hexameric assembly of members of the LRRC8 gene family. Knowing the genes underlying VRACs allowed the discovery of novel VRAC functions into cell volume regulation, and first structure function studies revealed important insight in channel activation mechanisms. The determination of cryo-EM structures of homomeric LRRC8A and LRRC8D complexes provide a framework for a rational approach to investigate biophysical mechanisms. We discuss several recent advances within the structural framework, and we critically review the literature on the main mechanisms proposed to be involved in VRAC activation, including low intracellular ionic strength, membrane unfolding, oxidation, phosphorylation and G-protein coupling.

Biophysical phenotyping of mesenchymal stem cells along the osteogenic differentiation pathway.

Mesenchymal stem cells represent an important resource, for bone regenerative medicine and therapeutic applications. This review focuses on new advancements and biophysical tools which exploit different physical and chemical markers of mesenchymal stem cell populations, to finely characterize phenotype changes along their osteogenic differentiation process. Special attention is paid to recently developed label-free methods, which allow monitoring cell populations with minimal invasiveness. Among them, quantitative phase imaging, suitable for single-cell morphometric analysis, and nanoindentation, functional to cellular biomechanics investigation. Moreover, the pool of ion channels expressed in cells during differentiation is discussed, with particular interest for calcium homoeostasis.Altogether, a biophysical perspective of osteogenesis is proposed, offering a valuable tool for the assessment of the cell stage, but also suggesting potential physiological links between apparently independent phenomena.

Epigallocatechin-3-gallate mobilizes intracellular Ca2+ in prostate cancer cells through combined Ca2+ entry and Ca2+-induced Ca2+ release.

AIMS: To elucidate the mechanism by which (-)-epigallocatechin-3-gallate (EGCG) mediates intracellular Ca2+ increase in androgen-independent prostate cancer (PCa) cells. MAIN METHODS: Following exposure to different doses of EGCG, viability of DU145 and PC3 PCa cells was evaluated by MTT assay and the intracellular Ca2+ dynamics by the fluorescent Ca2+ chelator Fura-2. The expression of different channels was investigated by qPCR analysis and sulfhydryl bonds by Ellman's assay. KEY FINDINGS: EGCG inhibited DU145 and PC3 proliferation with IC50 = 46 and 56 µM, respectively, and induced dose-dependent peaks of internal Ca2+ that were dependent on extracellular Ca2+. The expression of TRPC4 and TRPC6 channels was revealed by qPCR in PC3 cells, but lack of effect by modulators and blockers ruled out an exclusive role for these, as well as for voltage-dependent T-type Ca2+ channels. Application of dithiothreitol and catalase and sulfhydryl (SH) measurements showed that EGCG-induced Ca2+ rise depends on SH oxidation, while the effect of EGTA, dantrolene, and the PLC inhibitor U73122 suggested that EGCG-induced Ca2+ influx acts as a trigger for Ca2+-induced Ca2+ release, involving both ryanodine and IP3 receptors. Different from EGCG, ATP caused a rapid Ca2+ increase, which was independent of external Ca2+, but sensitive to U73122. SIGNIFICANCE: EGCG induces an internal Ca2+ increase in PCa cells by a multi-step mechanism. As dysregulation of cytosolic Ca2+ is directly linked to apoptosis in PCa cells, these data confirm the possibility of using EGCG as a synergistic adjuvant in combined therapies for recalcitrant malignancies like androgen-independent PCa.

Development of label-free biophysical markers in osteogenic maturation.

The spatial and temporal changes of morphological and mechanical properties of living cells reflect complex functionally-associated processes. Monitoring these modifications could provide a direct information on the cellular functional state. Here we present an integrated biophysical approach to the quantification of the morphological and mechanical phenotype of single cells along a maturation pathway. Specifically, quantitative phase microscopy and single cell biomechanical testing were applied to the characterization of the maturation of human foetal osteoblasts, demonstrating the ability to identify effective label-free biomarkers along this fundamental biological process.

Gain of function of sporadic/familial hemiplegic migraine-causing SCN1A mutations: Use of an optimized cDNA.

INTRODUCTION: Familial hemiplegic migraine 3 is an autosomal dominant headache disorder associated with aura and transient hemiparesis, caused by mutations of the neuronal voltage-gated sodium channel Nav1.1. While a gain-of function phenotype is generally assumed to underlie familial hemiplegic migraine, this has not been fully explored. Indeed, a major obstacle in studying in vitro neuronal sodium channels is the difficulty in propagating and mutagenizing expression plasmids containing their cDNAs. The aim of this work was to study the functional effect of two previously uncharacterized hemiplegic migraine causing mutations, Leu1670Trp (L1670W) and Phe1774Ser (F1774S). METHODS: A novel SCN1A containing-plasmid was designed in silico and synthesized, and migraine mutations were inserted in this background. Whole-cell patch clamp was performed to investigate the functional properties of mutant Nav1.1 transiently expressed in Human Embryonic Kidney 293 cells. RESULTS AND CONCLUSIONS: We generated an optimized Nav1.1 expression plasmid that was extremely simple to handle and used the novel plasmid to study the functional effects of two migraine mutations. We observed that L1670W, but not F1774S, reduced current density and that both mutations led to a dramatic increase in persistent sodium currents, a depolarizing shift of the steady state-inactivation voltage-dependence, and a faster recovery from inactivation. The results are consistent with a major gain-of function effect underlying familial hemiplegic migraine 3. Our optimization strategy will help to characterize in an efficient manner the effect in vitro of mutations of neuronal voltage-gated sodium channels.

The effect of pulsed electromagnetic field exposure on osteoinduction of human mesenchymal stem cells cultured on nano-TiO2 surfaces.

Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) are considered a great promise in the repair and regeneration of bone. Considerable efforts have been oriented towards uncovering the best strategy to promote stem cells osteogenic differentiation. In previous studies, hBM-MSCs exposed to physical stimuli such as pulsed electromagnetic fields (PEMFs) or directly seeded on nanostructured titanium surfaces (TiO2) were shown to improve their differentiation to osteoblasts in osteogenic condition. In the present study, the effect of a daily PEMF-exposure on osteogenic differentiation of hBM-MSCs seeded onto nanostructured TiO2 (with clusters under 100 nm of dimension) was investigated. TiO2-seeded cells were exposed to PEMF (magnetic field intensity: 2 mT; intensity of induced electric field: 5 mV; frequency: 75 Hz) and examined in terms of cell physiology modifications and osteogenic differentiation. Results showed that PEMF exposure affected TiO2-seeded cells osteogenesis by interfering with selective calcium-related osteogenic pathways, and greatly enhanced hBM-MSCs osteogenic features such as the expression of early/late osteogenic genes and protein production (e.g., ALP, COL-I, osteocalcin and osteopontin) and ALP activity. Finally, PEMF-treated cells resulted to secrete into conditioned media higher amounts of BMP-2, DCN and COL-I than untreated cell cultures. These findings confirm once more the osteoinductive potential of PEMF, suggesting that its combination with TiO2 nanostructured surface might be a great option in bone tissue engineering applications.