Enhancing effect of sodium butyrate on phosphatidylserine-liposome-induced macrophage polarization.

OBJECT: Phosphatidylserine-containing liposomes (PSLs) can mimic the immunomodulatory effects of apoptotic cells by binding to the phosphatidylserine receptors of macrophages. Sodium butyrate, an antiinflammatory short-chain fatty acid, is known to facilitate the M2 polarization of macrophages. This study aimed to investigate the effect of sodium butyrate on PSLs-induced macrophage polarization. METHODS: PSLs physical properties and cellular uptake tests, reverse transcription-quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, immunofluorescence staining, and flow cytometry analysis were performed to assess the polarization-related indicators of M1/M2 macrophages. RESULTS: The results showed that sodium butyrate did not affect the size and cellular uptake of PSLs. For M1 macrophage polarization, sodium butyrate significantly intensified the antiinflammatory function of PSLs, inhibiting LPS-induced proinflammatory genes expression, cytokines and enzyme release (tumor necrosis factor-alpha, interleukin (IL)-1ß, IL-6, and inducible nitric oxide synthase), as well as CD86 (M1 marker) expression. In addition to the enhancing effect of antiinflammation, sodium butyrate also promoted PSL-induced M2 macrophages polarization, especially elevated thymus and activation-regulated chemokine (TARC) and arginase-1 (Arg-1) enzyme levels which are involved in tissue repair. CONCLUSION: Sodium butyrate enhanced antiinflammatory properties and M2-polarization inducing effect of PSLs. Therefore, sodium butyrate may represent a novel approach to enhance PSL-induced macrophage polarization.

Modulation of Macrophage Polarization by Phospholipids on the Surface of Titanium.

Macrophage polarization has become increasingly important for the improvement of the biocompatibility of biomaterials. In this study, we coated Ti discs with phospholipids (phosphatidylserine/phosphatidylcholine [4:1 mole/mole]) by evaporating the solvent under vacuum, and observed the polarization of RAW 264.7 cells cultured on the discs. The coated discs were hydrated before cell culture was added. The shape of the hydrated phospholipids varied with the concentration of loaded phospholipids: a perforated layer (0.1 mM), tubules and spheres (1 mM), and spheres (10 mM). RAW 264.7 cells exhibited different morphologies, depending on the concentration of phospholipids. On the coated discs, the gene expression and protein release of TGF-ß1, VEGF, Arg-1, and TNF-α were downregulated, especially with 10 mM phospholipids. The stimulation of mRNA expression and the protein release of those genes by IL-4 and LPS were also disturbed on the phospholipid-coated discs. In conclusion, the polarization of RAW 264.7 cells was prevented by hydrated phospholipids on Ti discs.

Immunomodulation of Biomaterials by Controlling Macrophage Polarization.

Macrophages are key players in innate immune responses to foreign substances. They participate in the phagocytosis of biomaterial-derived particles, angiogenesis, recruitment of fibroblasts, and formation of granulation tissues. Most macrophage functions are achieved through the release of various cytokines and chemokines; the release profile of cytokines is dependent on the phenotype of macrophages, namely proinflammatory M1 or antiinflammatory M2. M1 and M2 macrophages coexist during an inflammatory phase, and the M1/M2 ratio is considered to be an important factor for wound-healing or tissue regeneration. This ratio depends on the chemical and physical properties of biomaterials. To obtain a favorable foreign body reaction to biomaterials, the phenotypes of the macrophages can be modulated by cytokines, antibodies, small chemicals, and microRNAs. Geometrical surface fabrication of biomaterials can also be used for modulating the phenotype of macrophages.

Streptococcus mutans sortase A inhibitory metabolites from the flowers of Sophora japonica.

A new maltol derivative (2) along with three known maltol derivative (1) and flavonol glycosides (3 and 4) were isolated from the dried flowers of Sophora japonica. Based upon the results of combined spectroscopic methods, the structure of new compound (2) was determined to be maltol-3-O-(4'-O-cis-p-coumaroyl-6'-O-(3-hydroxy-3-methylglutaroyl))-ß-glucopyranoside, an isomer of 1. These compounds strongly inhibited the action of sortase A (SrtA) from Streptococcus mutans, a primary etiologic agent of human dental caries. The onset and magnitude of inhibition of the saliva-induced aggregation in S. mutans treated with compound 2 (4×IC50) were comparable to the behavior of untreated srtA-deletion mutant.

Effects of dimethyloxalylglycine on wound healing of palatal mucosa in a rat model.

BACKGROUND: Rapid wound healing of oral soft tissue may reduce the opportunity of infection and discomfort of patients. Previous studies have demonstrated that enhancement of angiogenesis is an effective way to accelerate wound repair. In this study, to enhance angiogenesis and healing of palatal wounds, dimethyloxalylglycine (DMOG) was applied to a rat palatal wound model. DMOG is known to inhibit oxygen-dependent degradation of hypoxia inducible factor-1 alpha (HIF-1α), which can lead to up-regulation of angiogenesis markers, favoring wound repair. We also evaluated the effects of DMOG on cell migration and HIF-1α expression of rat palatal (RP) cells. Furthermore, mRNA and protein expression of vascular endothelial growth factor (VEGF) were analyzed in DMOG-treated RP cells. METHODS: Primary cultures of rat palatal (RP) cells were obtained from Sprague-Dawley (SD) rats. Effects of DMOG on cell viability and migration of RP cells were evaluated by using a formazan and culture insert, respectively. VEGF mRNA was observed by real-time PCR, and VEGF and HIF-1α proteins were detected by Western blotting. For the animal study, excisional wounds, 3 mm in diameter, were made at the central part of the palate of SD rats. DMOG with hyaluronic acid ointment was topically applied three times during 1 week, and then wound closures were quantitated photographically and histologically. RESULTS: DMOG was cytotoxic to RP cells at concentrations higher than 2 mM and did not affect cell migration at non-cytotoxic concentrations. mRNA and protein expression of VEGF were significantly stimulated by DMOG treatment. The protein level of HIF-1α was also stabilized in RP cells by DMOG. In the animal study, groups treated with 1 mg/ml DMOG showed an increase of rat palatal wound contractures. CONCLUSIONS: DMOG enhanced wound healing of rat palatal mucosa, which was likely due to the angiogenic effect of the agent.

Effects of vehicles on the physical properties and biocompatibility of premixed calcium silicate cements.

Premixed calcium silicate cements (pCSCs) contain vehicles which endow fluidity and viscosity to CSCs. This study aimed to investigate the effects of three vehicles, namely, polyethylene glycol (PEG), propylene glycol (PG), and dimethyl sulfoxide (DMSO), on the physicochemical properties and biocompatibility of pCSCs. The setting time, solubility, expansion rate, and mechanical strength of the pCSCs were evaluated, and the formation of calcium phosphate precipitates was assessed in phosphate-buffered saline (PBS). The effects of pCSC extracts on the osteogenic differentiation of mesenchymal stem cells (MSCs) were investigated. Finally, the tissue compatibility of pCSCs in rat femurs was observed. CSC containing PEG (CSC-PEG) exhibited higher solubility and setting time, and CSC-DMSO showed the highest expansion rate and mechanical strength. All pCSCs generated calcium phosphate precipitates. The extract of CSC-PG induced the highest expressions of osteogenic markers along with the greatest calcium deposites. When implanted in rat femurs, CSC-PEG was absorbed considerably, whereas CSC-PG remained relatively unaltered inside the femur.

Layered structure of sialoliths compared with tonsilloliths and antroliths.

Objectives: The aim of this study was to perform a comparative analysis of the ultrastructural and chemical composition of sialoliths, tonsilloliths, and antroliths and to describe their growth pattern. Materials and Methods: We obtained 19 specimens from 18 patients and classified the specimens into three groups: sialolith (A), tonsillolith (B), and antrolith (C). The peripheral, middle, and core regions of the specimens were examined in detail by histology, micro-computed tomography (micro- CT), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and transmission electron microscopy (TEM). Results: In the micro-CT, group A showed alternating radiodense and radiolucent layers, while group B had a homogeneous structure. Group C specimens revealed a compact homogeneous structure. Histopathologically, group A showed a laminated, teardrop-shaped, globular structure. Group B demonstrated degrees of immature calcification of organic and inorganic materials. In group C, the lesion was not encapsulated and showed a homogeneous lamellar bone structure. SEM revealed that group A showed distinct three layers: a peripheral multilayer zone, intermediate compact zone, and the central nidus area; groups B and C did not show these layers. The main elemental components of sialoliths were O, C, Ca, N, Cu, P, Zn, Si, Zr, F, Na, and Mg. In group B, a small amount of Fe was found in the peripheral region. Group C had a shorter component list: Ca, C, O, P, F, N, Si, Na, and Mg. TEM analysis of group A showed globular structures undergoing intra-vesicular calcification. In group B, bacteria were present in the middle layer. In the outer layer of the group C antrolith, an osteoblastic rimming was observed. Conclusion: Sialoliths had distinct three layers: a peripheral multilayer zone, an intermediate compact zone and the central nidus area, while the tonsillolith and antrolith specimens lacked distinct layers and a core.

Ultrastructural and immunohistochemical evaluation of hyperplastic soft tissues surrounding dental implants in fibular jaws.

In reconstructive surgery, complications post-fibula free flap (FFF) reconstruction, notably peri-implant hyperplasia, are significant yet understudied. This study analyzed peri-implant hyperplastic tissue surrounding FFF, alongside peri-implantitis and foreign body granulation (FBG) tissues from patients treated at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital. Using light microscopy, pseudoepitheliomatous hyperplasia, anucleate and pyknotic prickle cells, and excessive collagen deposition were observed in FFF hyperplastic tissue. Ultrastructural analyses revealed abnormal structures, including hemidesmosome dilation, bacterial invasion, and endoplasmic reticulum (ER) swelling. In immunohistochemical analysis, unfolded protein-response markers ATF6, PERK, XBP1, inflammatory marker NFκB, necroptosis marker MLKL, apoptosis marker GADD153, autophagy marker LC3, epithelial-mesenchymal transition, and angiogenesis markers were expressed variably in hyperplastic tissue surrounding FFF implants, peri-implantitis, and FBG tissues. NFκB expression was higher in peri-implantitis and FBG tissues compared to hyperplastic tissue surrounding FFF implants. PERK expression exceeded XBP1 significantly in FFF hyperplastic tissue, while expression levels of PERK, XBP1, and ATF6 were not significantly different in peri-implantitis and FBG tissues. These findings provide valuable insights into the interconnected roles of ER stress, necroptosis, apoptosis, and angiogenesis in the pathogenesis of oral pathologies, offering a foundation for innovative strategies in dental implant rehabilitation management and prevention.

Stimulating effects of quercetin and phenamil on differentiation of human dental pulp cells.

Dentin formation is preferred in the healing response of the pulp to pulp-capping agents during vital pulp therapy. Enhancement of the dentinogenic differentiation of dental pulp cells is thought to accelerate pulp repair. The aim of this study was to evaluate the dentinogenic activity of small molecules (three flavonoids and phenamil) that have been shown previously to induce osteoblast differentiation. Among the flavonoids (quercetin, genistein and baicalin), quercetin induced the highest alkaline phosphatase (ALP) activity of human dental pulp (HDP) cells. Phenamil, an amiloride derivative, elicited higher ALP activity than quercetin. However, increased expression of dentin sialophosphoprotein (DSPP) mRNA and mineral deposition were seen in cultures treated with quercetin compared with phenamil. This would seem to suggest that quercetin is the most dentinogenic agent among the tested chemicals. The increase in ALP activity in the quercetin-treated cells was not affected by ICI 182,780, an estrogen receptor inhibitor, and was partially blocked by PD98059, an extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor. This suggests that ERK1/2 is activated in the quercetin-induced differentiation of HDP cells without the mediation of estrogen receptors, which are known to be involved in osteoblast differentiation induced by quercetin.

Synergistic effects of arginine-glycine-aspartic acid and phosphatidylserine on the surface immunomodulation and osseointegration of titanium implants.

The control of macrophage polarization is important in bone tissue regeneration such as osseointegration. In this study, a coating method was developed to improve the osseointegration of titanium (Ti) implants by generating an immunomodulatory effect. The surface of the Ti discs was coated with a poly(lactide-co-glycolide)(PLGA) polymer, phosphatidylserine (PS), and arginine-glycine-aspartic acid (RGD) peptide conjugated phospholipid. In in vitro assay using mouse bone marrow-derived macrophages (BMDMs), the most significant expression of the M2 marker genes (Arg-1, YM-1, FIZZ1) and CD206, an M2 surface marker, was obtained with coatings containing 6 mol% RGD conjugates and phospholipids consisting of 50 mol% PS. The M2-inducing effect of RGD and PS was also verified in rat femurs where coated Ti rods were implanted. The RGD and PS coating significantly enhanced the osseointegration of the Ti implants. Moreover, a biomechanical push-out test showed that the RGD and PS coating increased the interfacial binding force between the bone and implants. These results indicate that PS and RGD can be applied to the solid surface of implantable biomedical devices to improve immunomodulation and tissue regeneration.

Identification of biological components for sialolith formation organized in circular multi-layers.

According to the previous studies of sialolithiasis reported so far, this study is aimed to identify the biological components of sialolith, which show different ultrastructures and chemical compositions from other stones, cholelith and urolith. Twenty-two specimens obtained from 20 patients were examined histologically, and analyzed with micro-CT, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). All sialoliths (n = 22) observed in this study showed a central nidus, which was filled with organoid matrix admixed with exosome vesicles, loose calcium apatite crystals, and many bacteria. The micro-CT and SEM observation clearly defined a single or multiple central nidus(es) encircled by highly calcified compact zone. The circular compact zone showed a band-like calcification, about 1-3 mm in thickness, and usually located between the central nidus and the peripheral multilayer zone. But some sialoliths (n = 5) showed severe erosion of compact zone by expanding multilayered zone depending on the level of calcification and inflammation in sialolith. By observing TEM images, many exosome vesicles and degraded cytoplasmic organelles were found in the central nidus, and some epithelial cells were also found in the calcified matrix of peripheral multilayer zone. Particularly, EDS analysis indicated the highest Ca/P ratio in the intermediate compact zone (1.77), and followed by the central nidus area (1.39) and the peripheral multilayer zone (0.87). Taken together, these data suggest that the central nidus containing many inflammatory exosomes and degraded cytoplasmic organelles has a potential to induce a band-like calcification of compact zone, and followed by the additional multilayer deposition of exfoliated salivary epithelial cells as well as salivary materials. Thereby, the calcium apatite-based sialolith is gradually growing in its volume size, and eventually obstructs the salivary flow and provides a site for the bacterial infection.

Effects of RGD-grafted phosphatidylserine-containing liposomes on the polarization of macrophages and bone tissue regeneration.

Phosphatidylserine-containing liposomes (PSLs) can mimic the anti-inflammatory effects of apoptotic cells by binding to the phosphatidylserine receptors of macrophages. MGF-E8, a bridge molecule between phosphatidylserine and macrophages, can promote M2 polarization by activating macrophage integrin with its arginine-glycine-aspartic acid (RGD) motif. In this study, to mimic MGF-E8, PSLs presenting RGD peptide (RGD-PSLs) were prepared, and their immunomodulatory effects on macrophages and the bone tissue regeneration of rat calvarial defects were investigated. RGD peptides enhanced the phagocytosis of PSLs by macrophages, especially when the PSLs contained 3% RGD. RGD-PSLs were also more effective than PSLs for the suppression of lipopolysaccharide-induced gene expression of proinflammatory cytokines (i.e., IL-1ß, IL-6, and TNF-α) as well as CD86 (M1 marker) expression. Furthermore, RGD promoted PSL-induced M2 polarization: 3%-RGD-PSLs significantly enhanced the mRNA expression of Arg-1, FIZZ1, and YM-1, as well as CD206 (M2 marker) expression. In a calvarial defect model, a significant increase in M2 with a decrease in M1 macrophages was observed with 3%-RGD-PSL treatment compared with the effects of PSLs alone. Finally, new bone formation was also accelerated by 3%-RGD-PSLs. Thus, these results suggest that the intensive immunomodulatory effect of RGD-PSLs led to the enhancement of bone tissue regeneration.

Reduction of fibrous encapsulation by polyethylene glycol-grafted liposomes containing phosphatidylserine.

Biomedical implants tend to induce fibrous encapsulation which can cause malfunction of devices and local discomfort of patients. The purpose of this study was to reduce foreign body-induced fibrous capsule formation by immunomodulation of macrophages. Polyethylene-glycol-grafted liposomes containing phosphatidylserine (PEG-PSLs) were used to modulate macrophages. Mixed cellulose ester (MCE) membranes coated with a PEG-PSLs-entrapped alginate-gelatin matrix were subcutaneously implanted into rats, and the thickness of the fibrous capsule around each MCE membrane was analyzed after four weeks. PEG-PSLs significantly reduced fibrous capsule thickness, while liposomes containing phosphatidylserine (PSLs) did not affect fibrosis. In in vitro assays, PEG-PSLs suppressed TGF-ß1 secretion and multinucleated giant cell (MGC) formation in IL-4-treated RAW 264.7, a murine macrophage cell line. Although PSLs inhibited MGC formation, they exerted no effect on the secretion of TGF- ß1, which is known to be an important factor in tissue fibrosis. Therefore, our results suggest that PEG-PSLs reduce fibrous capsule formation by mediating the suppression of TGF-ß1 secretion from macrophages.

Comparative Assessment of the Antioxidant Activities among the Extracts of Different Parts of Clausena lansium (Lour.) Skeels in Human Gingival Fibroblast Cells.

Clausena lansium (Lour.) Skeels (wampee) is an outstanding natural plant with medicinal properties. The aim of this study was to compare the cytoprotective effects of four parts of wampee under oxidative stress. The aqueous extracts of leaf, peel, pulp, and seed were tested for the proliferation effects on human gingival fibroblast (HGF) cells and the protective effects in the hydrogen peroxide-induced HGF model. Furthermore, the total glutathione assay and identification of rutin by high-performance liquid chromatography were carried out to attempt to determine whether the cytoprotective effects were related to the total glutathione (GSH) stability and rutin content. The results showed that all of the extracts had no cytotoxicity to HGF at tested concentrations ranging from 50 to 5000 µg/ml during 24 h, and the leaf, pulp, and seed extracts increased proliferation of HGF at relatively high concentrations. All the extracts except for the seed extract significantly decreased the production of reactive oxygen species, and the peel extracts exhibited the most effective antioxidant effect. The leaf extract had the highest anticytotoxicity and GSH stabilization effect in the HGF challenged with hydrogen peroxide. In addition, the relative content of rutin in peel and leaf extracts was higher than that in pulp and seed. The results of GSH assay and rutin identification suggest that different cellular protective effects among the four parts of wampee are partially related to the GSH stabilization and rutin content. These findings provide a scientific basis for the antioxidant effect-related biological activities of wampee extracts.

Effects of pentoxifylline and tocopherol on an osteoradionecrosis animal model.

PURPOSE: Osteoradionecrosis (ORN) is known to be a refractory disease in the oral and maxillofacial field. The purpose of this study was to examine the effects of pentoxifylline (PTX) and tocopherol (TP) on an ORN animal model focused on bone healing. MATERIALS AND METHODS: A total of 48 Sprague-Dawley rats were used: 40 received a single irradiation dose of 35 Gy on the left mandible, and eight were used as the nonirradiated control group. The rats received PTX (T1, C1), TP (T2, C2), a combination of PTX and TP (T3, C3), or normal saline (T4, C4). Three weeks after irradiation, the mandibular posterior teeth were extracted. The rats were sacrificed 4 weeks after extraction. RESULTS: In the T3 group, bone volume/tissue volume was 19.62 ± 16.03 (%), bone mineral density was as 0.31 ± 0.16 (g/cm3) in the micro-CT analysis, which were higher than that of other groups (p = 0.025, p = 0.012, respectively). In the histological analysis, bone regeneration was the most prominent in the T3 group. The ratio of empty lacunae was the highest in the T4 group, 68.77 ± 15.47 (%, p = 0.004). Immunohistochemistry showed that the expression of TNF-α was relatively lower in the T3 than in the T4 or T2 groups. The RT-qPCR showed the expression level of PECAM, VEGF-A, and osteocalcin was more than twofold as high as in the T3 group compared to the other groups. CONCLUSION: The combination of PTX and TP appears to promote angiogenesis and osteogenesis in a rat ORN model. Therefore, PTX and TP might be useful in the treatment and prevention of ORN.

Live cell imaging of the assembly, disassembly, and actin cable-dependent movement of endosomes and actin patches in the budding yeast, Saccharomyces cerevisiae.

Using FM4-64 to label endosomes and Abp1p-GFP or Sac6p-GFP to label actin patches, we find that (1) endosomes colocalize with actin patches as they assemble at the bud cortex; (2) endosomes colocalize with actin patches as they undergo linear, retrograde movement from buds toward mother cells; and (3) actin patches interact with and disassemble at FM4-64-labeled internal compartments. We also show that retrograde flow of actin cables mediates retrograde actin patch movement. An Arp2/3 complex mutation decreases the frequency of cortical, nonlinear actin patch movements, but has no effect on the velocity of linear, retrograde actin patch movement. Rather, linear actin patch movement occurs at the same velocity and direction as the movement of actin cables. Moreover, actin patches require actin cables for retrograde movements and colocalize with actin cables as they undergo retrograde movement. Our studies support a mechanism whereby actin cables serve as "conveyor belts" for retrograde movement and delivery of actin patches/endosomes to FM4-64-labeled internal compartments.

Influence of filler distribution on the color parameters of experimental resin composites.

OBJECTIVES: Simulating the optical properties of natural tooth would be the final goal for esthetic restorative materials. Filler distribution in resin composites determines the scattering in composite materials, which in turn would influence the color parameters such as lightness, chroma and hue. The objective of this study was to determine the influence of filler size and amount on the color parameters of experimental resin composites. METHOD: Color of 11 experimental resin composites with two different sized fillers (LG: 0.77 microm and SG: 0.50 microm) in 10-70 wt% was measured by a spectrophotometer. Color coordinates (CIE L*, a* and b*), chroma and hue angle were determined. Optical constants including scattering coefficient (S), absorption coefficient (K) and light reflectivity (RI) were calculated. To determine the influence of the amount of filler on the optical parameters, Pearson correlations between the amount of filler (%) and color parameters and optical constants were calculated. Correlations between the optical constants (S, K and RI) and color parameters were calculated (p<0.05). RESULTS: S value increased as the amount of filler increased. RI value generally increased as the amount of filler increased for LG filler group, and increased up to 40% filler for SG filler group. CIE L* value increased as the amount of filler increased in both of LG and SG filler groups. CIE L* value was highly correlated with S and RI values for both filler groups (r=0.961-0.974). CONCLUSION: Lightness was highly correlated with the amount of filler, S and RI values (r=0.932-0.974). But the correlation coefficients between the amount of filler and chroma/hue were moderate (r=0.406-0.827); therefore, pigmentation would be tried to simulate the color of resin composites to those of natural tooth. Optical properties of resin composites could be partly simulated to those of teeth by controlling the filler distribution.

Effects of phosphatidylserine-containing supported lipid bilayers on the polarization of macrophages.

Placement of dental implants initiates inflammatory foreign body response, in which macrophages play a central role and affect the subsequent tissue healing process such as bone formation. The purpose of this study was to fabricate phosphatidylserine (PS)-containing supported lipid bilayers (SLBs) on a titanium surface to regulate the polarization of macrophages, a critical factor that affects following tissue healing and regeneration. The fluorescent recovery after photobleaching images showed that the percentage of PS had a critical influence on the fluidity, and 20% PS had the highest fluidity. Furthermore, more expanded and elongated cells were observed in the SLB-coated groups. transforming growth factor-ß1 and vascular endothelial growth factor, the key cytokine markers of M2 macrophage polarization, were increased in the SLB-coated groups, especially in the 20% PS group. Consistently, cells cultured on the SLB-coated titanium exhibited the distribution of CD206+ , which is a M2 macrophage specific maker. The results of this study demonstrated M2 polarization of macrophages on PS-SLB-coated titanium discs, which suggests the application of PS-SLB as an immune-regulating coating material to improve tissue reactions to dental implants. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2625-2633, 2018.

Live cell imaging of mitochondrial movement along actin cables in budding yeast.

BACKGROUND: Mitochondrial inheritance is essential for cell division. In budding yeast, mitochondrial movement from mother to daughter requires (1) actin cables, F-actin bundles that undergo retrograde movement during elongation from buds into mother cells; (2) the mitochore, a mitochondrial protein complex implicated in linking mitochondria to actin cables; and (3) Arp2/3 complex-mediated force generation on mitochondria. RESULTS: We observed three new classes of mitochondrial motility: anterograde movement at velocities of 0.2-0.33 microm/s, retrograde movement at velocities of 0.26-0.51 microm/s, and no net anterograde or retrograde movement. In all cases, motile mitochondria were associated with actin cables undergoing retrograde flow at velocities of 0.18-0.62 microm/s. Destabilization of actin cables or mutations of the mitochore blocked all mitochondrial movements. In contrast, mutations in the Arp2/3 complex affected anterograde but not retrograde mitochondrial movements. CONCLUSIONS: Actin cables are required for movement of mitochondria, secretory vesicles, mRNA, and spindle alignment elements in yeast. We provide the first direct evidence that one of the proposed cargos use actin cables as tracks. In the case of mitochondrial inheritance, anterograde movement drives transfer of the organelle from mothers to buds, while retrograde movement contributes to retention of the organelle in mother cells. Interaction of mitochondria with actin cables is required for anterograde and retrograde movement. In contrast, force generation on mitochondria is required only for anterograde movement. Finally, we propose a novel mechanism in which actin cables serve as "conveyor belts" that drive retrograde organelle movement.