Pulsed electromagnetic fields increase growth factor release by nonunion cells

The mechanisms involved in pulsed electromagnetic field stimulation of nonunions are not known. Animal and cell culture models suggest endochondral ossification is stimulated by increasing cartilage mass and production of transforming growth factor-beta 1. For the current study, the effect of pulsed electromagnetic field stimulation on cells from human hypertrophic (n = 3) and atrophic (n = 4) nonunion tissues was examined. Cultures were placed between Helmholtz coils, and an electromagnetic field (4.5-ms bursts of 20 pulses repeating at 15 Hz) was applied to 1/2 of them 8 hours per day for 1, 2, or 4 days. There was a time-dependent increase in transforming growth factor-beta 1 in the conditioned media of treated hypertrophic nonunion cells by Day 2 and of atrophic nonunion cells by Day 4. There was no effect on cell number, [3H]-thymidine incorporation, alkaline phosphatase activity, collagen synthesis, or prostaglandin E2 and osteocalcin production. This indicates that human nonunion cells respond to pulsed electromagnetic fields in culture and that transforming growth factor-beta 1 production is an early event. The delayed response of hypertrophic and atrophic nonunion cells (> 24 hours) suggests that a cascade of regulatory events is stimulated, culminating in growth factor synthesis and release.     

Effects of pulsed electromagnetic field frequencies on the osteogenic differentiation of human mesenchymal stem cells

The purpose of this study was to evaluate the effect of different frequencies of pulsed electromagnetic fields on the osteogenic differentiation of human mesenchymal stem cells. Third-generation human mesenchymal stem cells were irradiated with different frequencies of pulsed electromagnetic fields, including 5, 25, 50, 75, 100, and 150 Hz, with a field intensity of 1.1 mT, for 30 minutes per day for 21 days. Changes in human mesenchymal stem cell morphology were observed using phase contrast microscopy. Alkaline phosphatase activity and osteocalcin expression were also determined to evaluate human mesenchymal stem cell osteogenic differentiation.Different effects were observed on human mesenchymal stem cell osteoblast induction following exposure to different pulsed electromagnetic field frequencies. Levels of human mesenchymal stem cell differentiation increased when the pulsed electromagnetic field frequency was increased from 5 hz to 50 hz, but the effect was weaker when the pulsed electromagnetic field frequency was increased from 50 Hz to 150 hz. The most significant effect on human mesenchymal stem cell differentiation was observed at of 50 hz.The results of the current study show that pulsed electromagnetic field frequency is an important factor with regard to the induction of human mesenchymal stem cell differentiation. Furthermore, a pulsed electromagnetic field frequency of 50 Hz was the most effective at inducing human mesenchymal stem cell osteoblast differentiation in vitro.     

Maturation state determines the response of osteogenic cells to surface roughness and 1,25-dihydroxyvitamin D3.

In this study we assessed whether osteogenic cells respond in a differential manner to changes in surface roughness depending on their maturation state. Previous studies using MG63 osteoblast-like cells, hypothesized to be at a relatively immature maturation state, showed that proliferation was inhibited and differentiation (osteocalcin production) was stimulated by culture on titanium (Ti) surfaces of increasing roughness. This effect was further enhanced by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. In the present study, we examined the response of three additional cell lines at three different maturation states: fetal rat calvarial (FRC) cells (a mixture of multipotent mesenchymal cells, osteoprogenitor cells, and early committed osteoblasts), OCT-1 cells (well-differentiated secretory osteoblast-like cells isolated from calvaria), and MLO-Y4 cells (osteocyte-like cells). Both OCT-1 and MLO-Y4 cells were derived from transgenic mice transformed with the SV40 large T-antigen driven by the osteocalcin promoter. Cells were cultured on Ti disks with three different average surface roughnesses (Ra): PT, 0.5 microm; SLA, 4.1 microm; and TPS, 4.9 microm. When cultures reached confluence on plastic, vehicle or 10(-7) M or 10(-8) M 1,25(OH)2D3 was added for 24 h to all of the cultures. At harvest, cell number, alkaline phosphatase-specific activity, and production of osteocalcin, transforming growth factor beta1 (TGF-beta1) and prostaglandin E2 (PGE2) were measured. Cell behavior was sensitive to surface roughness and depended on the maturation state of the cell line. Fetal rat calvarial (FRC) cell number and alkaline phosphatase-specific activity were decreased, whereas production of osteocalcin, TGF-beta1, and PGE2 were increased with increasing surface roughness. Addition of 1,25(OH)2D3 to the cultures further augmented the effect of roughness for all parameters in a dose-dependent manner; only TGF-beta1 production on plastic and PT was unaffected by 1,25(OH)2D3. OCT-1 cell number and alkaline phosphatase (SLA > TPS) were decreased and production of PGE2, osteocalcin, and TGF-beta1 were increased on SLA and TPS. Response to 1,25(OH)2D3 varied with the parameter being measured. Addition of the hormone to the cultures had no effect on cell number or TGF-beta1 production on any surface, while alkaline phosphatase was stimulated on SLA and TPS; osteocalcin production was increased on all Ti surfaces but not on plastic; and PGE2 was decreased on plastic and PT, but unaffected on SLA and TPS. In MLO-Y4 cultures, cell number was decreased on SLA and TPS; alkaline phosphatase was unaffected by increasing surface roughness; and production of osteocalcin, TGF-beta1, and PGE2 were increased on SLA and TPS. Although 1,25(OH)2D3 had no effect on cell number, alkaline phosphatase, or production of TGF-beta1 or PGE2 on any surface, the production of osteocalcin was stimulated by 1,25(OH)2D3 on SLA and TPS. These results indicate that surface roughness promotes osteogenic differentiation of less mature cells, enhancing their responsiveness to 1,25(OH)2D3. As cells become more mature, they exhibit a reduced sensitivity to their substrate but even the terminally differentiated osteocyte is affected by changes in surface roughness.     

Modulation of osteogenesis in human mesenchymal stem cells by specific pulsed electromagnetic field stimulation

Human mesenchymal stem cells (hMSCs) are a promising candidate cell type for regenerative medicine and tissue engineering applications by virtue of their capacity for self‐renewal and multipotent differentiation. Our intent was to characterize the effect of pulsed electromagnetic fields (PEMFs) on the proliferation and osteogenic differentiation of hMSCs in vitro. hMSCs isolated from the bone marrow of adult patients were cultured with osteogenic medium for up to 28 days and exposed to daily PEMF stimulation with single, narrow 300 µs quasi‐rectangular pulses with a repetition rate of 7.5 Hz. Relatively greater cell numbers were observed at late stages of osteogenic culture with PEMF exposure. The production of alkaline phosphatase (ALP), an early marker of osteogenesis, was significantly enhanced at day 7 with PEMF treatment in both basal and osteogenic cultures as compared to untreated controls. Furthermore, the expressions of other early osteogenic genes, including Runx2/Cbfa1 and ALP, were also partially modulated by PEMF exposure, indicating that osteogenesis in hMSCs was associated with the specific PEMF stimulation. Based on ALP and alizarin red S staining, the accumulation of ALP protein produced by the hMSCs as well as calcium deposits reached their highest levels at day 28. Our results indicate that extremely low‐frequency PEMF stimulation may play a modulating role in hMSC osteogenesis. Taken together, these findings provide insights on the development of PEMF as an effective technology for regenerative medicine. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res     

Low intensity pulsed ultrasound stimulates osteogenic activity of human periosteal cells

The effect of low intensity pulsed ultrasound on human periosteal cells was investigated. Normal human periosteum was obtained to culture the periosteal cells. After characterization, cultures of periosteal cells at Days 2 and 4 were treated with ultrasound for 5, 10, and 20 minutes respectively. Assessments were done to assess total number of viable cells, cell proliferation, alkaline phosphatase activity, osteocalcin secretion, vascular endothelial growth factor expression, and calcium nodule formation. With the cells not treated with ultrasound as the control, the results showed that ultrasound did not affect the total number of viable cells. It stimulated cell proliferation at the early phase of cell culture. The activity of alkaline phosphatase was increased significantly in the culture at Day 4. A similar effect was seen with osteocalcin secretion and the responses were dose-dependent. The vascular endothelial growth factor secretion increased in Day 2 and Day 4 cultures with the dose-dependent effect. Formation of calcium nodules was significantly higher with ultrasound treatment. We think that low intensity pulsed ultrasound stimulated periosteal cell proliferation and differentiation toward osteogenic lineage. The dose-dependent effect on osteogenic activities may modify the existing treatment regimen. Ultrasound treatment should be started from the beginning of fracture healing.     

Pulsed electromagnetic fields enhance BMP‐2 dependent osteoblastic differentiation of human mesenchymal stem cells

Mesenchymal stem cells (MSCs) express an osteoblastic phenotype when treated with BMP‐2, and BMP‐2 is used clinically to induce bone formation although high doses are required. Pulsed electromagnetic fields (PEMF) also promote osteogenesis in vivo, in part through direct action on osteoblasts. We tested the hypothesis that PEMF enhances osteogenesis of MSCs in the presence of an inductive stimulus like BMP‐2. Confluent cultures of human MSCs were grown on calcium phosphate disks and were treated with osteogenic media (OM), OM containing 40 ng/mL rhBMP‐2, OM + PEMF (8 h/day), or OM + BMP‐2 + PEMF. MSCs demonstrated minor increases in alkaline phosphatase (ALP) during 24 days in culture and no change in osteocalcin. OM increased ALP and osteocalcin by day 6, but PEMF had no additional effect at any time. BMP‐2 was stimulatory over OM, and PEMF + BMP‐2 synergistically increased ALP and osteocalcin. PEMF also enhanced the effects of BMP‐2 on PGE2, latent and active TGF‐β1, and osteoprotegerin. Effects of PEMF on BMP‐2–treated cells were greatest at days 12 to 20. These results demonstrate that PEMF enhances osteogenic effects of BMP‐2 on MSCs cultured on calcium phosphate substrates, suggesting that PEMF will improve MSC response to BMP‐2 in vivo in a bone environment. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1250–1255, 2008     

Multilineage differentiation of adult human bone marrow progenitor cells transduced with human papilloma virus type 16 E6/E7 genes

We have established a new adult human bone marrow-derived cell line hMPC 32F, stably transduced with human papilloma virus type 16 E6/E7 genes, that displays mesenchymal multilineage differentiation ability in vitro. The hMPC 32F cells exhibited a population doubling time of 22 h and have been maintained in culture for about 20 passages. When cultured in conditions promoting osteogenic, adipogenic, or chondrogenic differentiation, hMPC 32F cells expressed mature differentiated phenotypes. These include (1) osteoblastic phenotype characterized by upregulated alkaline phosphatase (ALP) expression and extracellular matrix mineralization, (2) adipocytic phenotype with the presence of intracellular lipid droplets, and (3) chondrocytic phenotype of round cells surrounded by a sulfated proteoglycan-rich matrix. In addition, the hMPC 32F cells expressed differentiation lineage-specific genes, as detected by RT-PCR. Furthermore, osteogenic and adipogenic cultures responded to regulatory factors such as transforming growth factor-beta1 (TGF-beta1) and 1alpha, 25-dihydroxyvitamin D3 (1,25(OH)2D3). Thus, continuous treatment of osteogenic cultures for 2 weeks with TGF-beta1 decreased ALP activity and mRNA expression and inhibited osteocalcin mRNA expression and matrix mineralization, whereas l,25(OH)2D3 had an additive, stimulatory effect. In adipogenic cultures, treatment with TGF-beta1 for 2 weeks markedly inhibited adipogenesis whereas 1,25(OH)2D3 had no obvious effect. Finally, clonal analysis of hMPC 32F cells revealed a high percentage of multipotent clones, although clones of more restricted differentiation potential were also present. These characteristics of the hMPC 32F cell line suggest their pluripotent, progenitor, and nontransformed nature and indicate their potential application for studying the mechanisms governing developmental potential of adult human bone marrow mesenchymal progenitor cells.     

Induction of human osteoprogenitor chemotaxis, proliferation, differentiation, and bone formation by osteoblast stimulating factor-1/pleiotrophin: osteoconductive biomimetic scaffolds for tissue engineering.

The process of bone growth, regeneration, and remodeling is mediated, in part, by the immediate cell-matrix environment. Osteoblast stimulating factor-1 (OSF-1), more commonly known as pleiotrophin (PTN), is an extracellular matrix-associated protein, present in matrices, which act as targets for the deposition of new bone. However, the actions of PTN on human bone progenitor cells remain unknown. We examined the effects of PTN on primary human bone marrow stromal cells chemotaxis, differentiation, and colony formation (colony forming unit-fibroblastic) in vitro, and in particular, growth and differentiation on three-dimensional biodegradable porous scaffolds adsorbed with PTN in vivo. Primary human bone marrow cells were cultured on tissue culture plastic or poly(DL-lactic acid-co-glycolic acid) (PLGA; 75:25) porous scaffolds with or without addition of recombinant human PTN (1 pg-50 ng/ml) in basal and osteogenic conditions. Negligible cellular growth was observed on PLGA scaffold alone, generated using a super-critical fluid mixing method. PTN (50 microg/ml) was chemotactic to human osteoprogenitors and stimulated total colony formation, alkaline phosphatase-positive colony formation, and alkaline phosphatase-specific activity at concentrations as low as 10 pg/ml compared with control cultures. The effects were time-dependent. On three-dimensional scaffolds adsorbed with PTN, alkaline phosphatase activity, type I collagen formation, and synthesis of cbfa-1, osteocalcin, and PTN were observed by immunocytochemistry and PTN expression by in situ hybridization. PTN-adsorbed constructs showed morphologic evidence of new bone matrix and cartilage formation after subcutaneous implantation as well as within diffusion chambers implanted into athymic mice. In summary, PTN has the ability to promote adhesion, migration, expansion, and differentiation of human osteoprogenitor cells, and these results indicate the potential to develop protocols for de novo bone formation for skeletal repair that exploit cell-matrix interactions.     

Differentiation of osteoid-producing cellsin vitro: Possible evidence for the requirement of a microenvironment

Summary Periostea were dissected from 17-day-old chicken embryo calvariae, placed on millipore filters, and cultured on fluid media containing serum or on serum and plasma containing “plasma clots,” in three ways: 1) with the osteogenic layer facing the filter, 2) with the osteogenic layer away from the filter, 3) folded such that the osteogenic layer was in apposition with itself within the fold. The cultures were studied histologically as well as biochemically. Periostea that were cultured folded showed differentiation of osteoblastlike cells after 2 days, and production of osteoid at day 4. Tissues cultured with the osteogenic layer away from the filter demonstrated similar osteoblastic differentiation and osteoid production. Both types of cultures exhibited an increase in histochemically detectable alkaline phosphatase activity over the 4 day culture period that was associated with osteoblasts and the osteogenic area. Periostea cultured with the osteogenic layer facing the filter produced no osteoid. In these cultures, histochemically detectable alkaline phosphatase activity decreased and virtually disappeared over the 4 day culture period. The possibility that the creation of a suitable micro-environment is required for osteodifferentiation in this culture system is discussed.     

不同年龄人骨髓间充质干细胞体外增殖及成骨分化的研究

目的 :观测年龄对人骨髓间充质干细胞 (humanmesenchymalstemcells ,hMSCs)体外增殖、成骨分化的影响。方法 :使用密度梯度离心法分离不同年龄人骨髓MSCs进行培养 ,保留贴壁细胞传代 ,观察细胞生长情况 ,检测其增殖活性、碱性磷酸酶活性 (ALP)、诱导后骨钙素定量测定。结果 :低龄hMSCs较高龄hMSCs体外生长快、MTT、ALP及骨钙素浓度高。结论 :hMSCs的增殖和成骨分化的能力和活性随着年龄的增加而降低。     

Pulsed electromagnetic fields in the treatment of nonunion

Background

Clinical application of electric stimulation and electromagnetic field stimulation include the treatment of delayed union and nonunion. In the literature success rates up to 90% are reported for the treatment of delayed union and nonunion with pulsed electromagnetic stimulation. We report our experience with pulsed electromagnetic stimulation in the treatment of nonunion.

Methods

All patients treated with pulsed electromagnetic stimulation for a nonunion between January 1996 and January 2000 were included.

Results

A total of 93 patients were included. One group was treated for long bone fractures (LBF) (64 patients). The other group consisted of patients treated for non long bone fractures (NLBF). We evaluated our findings according to clinical and radiographic criteria. The success rate of our treatment of a nonunion with pulsed electromagnetic field was 76% for the LBF group and 79% for the NLBF group.

Conclusion

Pulsed electromagnetic field stimulation of a nonunion showed to be an effective treatment in our study.     

Stimulation of osteogenic differentiation in human osteoprogenitor cells by pulsed electromagnetic fields: an in vitro study

Background  

Although pulsed electromagnetic field (PEMF) stimulation may be clinically beneficial during fracture healing and for a wide range of bone disorders, there is still debate on its working mechanism. Mesenchymal stem cells are likely mediators facilitating the observed clinical effects of PEMF. Here, we performed in vitro experiments to investigate the effect of PEMF stimulation on human bone marrow-derived stromal cell (BMSC) metabolism and, specifically, whether PEMF can stimulate their osteogenic differentiation.     

Shock wave application enhances pertussis toxin protein-sensitive bone formation of segmental femoral defect in rats.

Extracorporeal shock waves (ESWs) elicit a dose-dependent effect on the healing of segmental femoral defects in rats. After ESW treatment, the segmental defect underwent progressive mesenchymal aggregation, endochondral ossification, and hard callus formation. Along with the intensive bone formation, there was a persistent increase in TGF-beta1 and BMP-2 expression. Pretreatment with pertussis toxin reduced ESW-promoted callus formation and gap healing, which presumably suggests that Gi proteins mediate osteogenic signaling. INTRODUCTION: Extracorporeal shock waves (ESWs) have previously been used to promote bone repair. In our previous report, we found that ESWs promoted osteogenic differentiation of mesenchymal cells through membrane perturbation and activation of Ras protein. In this report, we show that ESWs elicit a dose-dependent effect on the healing of segmental defects and that Gi proteins play an important role in mediating ESW stimulation. MATERIALS AND METHODS: Rats with segmental femoral defects were subjected to ESW treatment at different energy flux densities (EFD) and impulses. Bone mass (mineral density and calcium content), osteogenic activities (bone alkaline phosphatase activity and osteocalcin content), and immunohistochemistry were assessed. RESULTS: An optimal ESW energy (500 impulses at 0.16 mJ/mm2 EFD) stimulated complete bone healing without complications. ESW-augmented healing was characterized by significant increases (p < 0.01) in callus size, bone mineral density, and bone tissue formation. With exposure to ESW, alkaline phosphatase activity and osteocalcin production in calluses were found to be significantly enhanced (p < 0.05). After ESW treatment, the histological changes we noted included progressive mesenchymal aggregation, endochondral ossification, and hard callus formation. Intensive bone formation was associated with a persistent increase in transforming growth factor-beta 1 (TGF-beta1) and bone morphogenetic protein-2 (BMP-2) expression, suggesting both growth factors were active in ESW-promoted bone formation. We also found that pertussis toxin, an inhibitor of membrane-bound Gi proteins, significantly reduced (p < 0.01) ESW promotion of callus formation and fracture healing. CONCLUSION: ESW treatments enhanced bone formation and the healing of segmental femoral defects in rats. It also seems likely that TGF-beta1 and BMP-2 are important osteogenic factors for ESW promotion of fracture healing, presumably through Gi protein-mediated osteogenic signaling.     

Insulin like growth factor I hormonal regulation by growth hormone and by 1,25(OH)2D3 and activity on human osteoblast-like cells in short-term cultures

IGF-1 has been shown to be locally produced in several tissues and to play a role in the regulation of cellular activity. We have investigated its production in short-term cultures of human bone derived cells, and the regulation of this production by growth hormone (GH) and by 1,25 dihydroxyvitamin D3 (1,25(OH)2D3). Bone cells obtained from surgical bone biopsies produced and secreted IGF-1 in their culture media. In four days cultures of bone-derived cells recombinant human r-IGF-1 at 20 ng/mL increased the alkaline phosphatase activity and the osteocalcin (bone gla protein) secretion, two specific markers of bone formation. This stimulation occurred only in the presence of 1,25(OH)2D3. Human bone cells exposed to GH increased their alkaline phosphatase activity, but no osteocalcin was detectable. However, in the presence of 1,25(OH)2D3 (1 nM), GH in concentrations of 8 to 40 nM increased by 30-50% the alkaline phosphatase activity and by 50 to 100% the osteocalcin secretion of human bone cells. At the same concentrations, GH also increased by 140% endogenous IGF-1 levels in cell culture supernatants, 1,25(OH)2D3 (10 nM) also increased time- and dose-dependently, IGF-1 levels in human bone cell supernatants, and stimulated dose-dependently alkaline phosphatase activity and osteocalcin secretion. It is therefore suggested that by regulating local production of growth factors such as IGF-1, GH and 1,25(OH)2D3 may modulate the metabolism of human bone cells.     

人羊膜间充质细胞向成骨细胞诱导分化的实验研究

目的 观察人羊膜间充质细胞(human amnion mesenchymal cells,hAMCs)体外诱导向成骨细胞分化,为骨组织工程提供种子细胞。方法 从剖宫产后废弃的人羊膜组织分离培养hAMCs,经成骨细胞诱导条件培养基诱导后,对细胞形态特征、碱性磷酸酶、骨桥素、骨钙素表达以及I型胶原分泌进行观察和检测。结果 原代培养的hAMCs形态呈长梭形或不规则形,呈均匀分布生长,传代后细胞体积略变大,约5～7d传代1次。经成骨细胞诱导培养15d后,hAMCs碱性磷酸酶、骨钙素、骨桥素的表达呈阳性,并且检测有I型胶原分泌。结论 hAMCs易于体外分离培养及扩增,体外成骨细胞定向诱导的hAMCs具有典型的成骨细胞的形态和功能性特征,是良好的骨组织工程种子细胞。     

探讨电磁场影响骨髓间充质干细胞增殖分化的时间依赖性

目的 探究正弦波电磁场诱导大鼠骨髓间充质干细胞(BMSCs)成骨方向分化、促进其增殖的时间依赖性.方法 用差速贴壁法分离培养(bone marrow-derived mesenchymal stem cells,BMSCs),取用生长状态良好的第三代细胞进行实验.将细胞按照1×105个/孔接种于3.5 cm细胞培养皿中...     

Time-varying magnetic fields: effects of orientation on chondrocyte proliferation

The purpose of this study was to determine the effect of orientation of pulsed electromagnetic fields (PEMFs) on cellular proliferation and extracellular matrix synthesis. Bovine articular chondrocytes were cultured in PEMFs (repetitive pulse at 72 Hz) generated using Helmholtz coils oriented either parallel (horizontal) or perpendicular (vertical) to the plane of cell adhesion. Dissipation of signal energy in the form of heat increased the temperature of the PEMF coils by 2 degrees C and the tissue culture medium by 1 degree C. Therefore, control coils, which emitted no PEMFs, were heated to the temperature of PEMF coils by circulating water. Chondrocytes were cultured in 16-mm-well culture plates, and the data for individual wells were pooled as triplicates. Although not observed by microscopic examination of individual wells, positionally dependent electric field effects may be minimized by this approach. PEMFs generated by coils oriented vertically significantly decreased chondrocyte proliferation. The effect was dependent on the concentration of serum in the culture media. At 3% serum concentration, the total cell number attained after 10 days of culture was reduced by 50% in stimulated cultures when compared with controls. At 5% serum concentration, there was no effect. PEMFs applied by coils oriented horizontally did not alter proliferation of articular chondrocytes. PEMFs had no effect on synthesis of extracellular matrix by chondrocytes plated at high density, irrespective of orientation.