Local Factor Production Research Articles

Pathogenesis of IgA nephropathy

Since its first description in 1968, IgA nephropathy has remained the most common form of idiopathic glomerulonephritis leading to chronic kidney disease in developed countries. The exact pathogenesis of IgA nephropathy is still not well defined. Current data implicate an important genetic factor, especially in promoting the overproduction of an aberrant form of IgA1. The immunochemical aberrancy of IgA nephropathy is characterized by the undergalactosylation of O-glycans in the hinge region of IgA1. However, such aberrant glycosylation alone does not cause renal injury. The next stage of disease development requires the formation of glycan-specific IgG and IgA antibodies that recognize the undergalactosylated IgA1 molecule. These antibodies often have reactivity against antigens from extrinsic microorganisms and might arise from recurrent mucosal infection. B cells that respond to mucosal infections, particularly tonsillitis, might produce the nephritogenic IgA1 molecule. With increased immune-complex formation and decreased clearance owing to reduced uptake by the liver, IgA1 binds to the glomerular mesangium via an as yet unidentified receptor. Glomerular IgA1 deposits trigger the local production of cytokines and growth factors, leading to the activation of mesangial cells and the complement system. Emerging data suggest that mesangial-derived mediators following glomerular deposition of IgA1 lead to podocyte and tubulointerstitial injury via mesangio-podocytic-tubular crosstalk. This Review summarizes the latest findings in the pathogenesis of IgA nephropathy.

Skeletal involvement in the pathogenesis and outcomes of rheumatoid arthritis and osteoarthritis

Bone remodeling is a frequently observed phenomenon in musculoskeletal diseases such as rheumatoid arthritis (RA) and osteoarthritis (OA). The level of imbalance between bone resorption/deposition is responsible for the morphological changes osteopenia/bone erosion/osteosclerosis observed in these arthritic conditions. In RA, increased osteoclastic activity is responsible for the development of focal osteopenia/erosion and systemic osteoporosis. The increased osteoclast activity in RA has been demonstrated to be linked to a dysregulation of pathways including cell-cell interactions, cytokines, and the receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL) system. Recent studies have shown that joint erosion in RA is linked to a decrease in long-term physical function. Under OA conditions, the subchondral bone is the site of numerous dynamic morphological changes. These changes are associated with a number of local abnormal biochemical pathways related to the altered metabolism of osteoblasts and osteoclasts. At the early stages of the disease process, increased bone loss and resorption is observed with subchondral bone associated with local production of catabolic factors including cathepsin K and MMP-13. Moreover, OA osteoblasts present an abnormal phenotype resulting in increased production of growth hormones and catabolic factors. In addition, factors such as osteoprotegerin (OPG) and RANKL have been found to be expressed and modulated over time in human OA subchondral bone. Their synthesis varies from being reduced in early OA to being increased in the late stages of the disease. This finding may explain that in the early stages of OA, bone remodeling favors resorption and in the more advanced stages of the disease, bone formation is predominant. Magnetic resonance imaging (MRI) studies in knee OA patients have shown that the subchondral bone is frequently the site of signal alterations-bone marrow lesions (BML) - indicative of a great variety of morphological changes. BML and cartilage loss have been linked in several studies. Moreover, studies have identified, in OA patients, a number of risk factors for total knee replacement including BMLs. The paradigms regarding the role of bone lesions in arthritic diseases raise a number of important questions. A comprehensive understanding of the factors that contribute to these changes will provide us with better knowledge of the pathophysiology of the diseases and the role of these structural alterations in patient symptoms and prognosis, as well as guiding the development of new therapeutic strategies.

Human Amniotic Fluid Stem Cell Preconditioning Improves Their Regenerative Potential

Human amniotic fluid stem (hAFS) cells, a novel class of broadly multipotent stem cells that share characteristics of both embryonic and adult stem cells, have been regarded as promising candidate for cell therapy. Taking advantage by the well-established murine model of acute kidney injury (AKI), we studied the proregenerative effect of hAFS cells in immunodeficient mice injected with the nephrotoxic drug cisplatin. Infusion of hAFS cells in cisplatin mice improved renal function and limited tubular damage, although not to control level, and prolonged animal survival. Human AFS cells engrafted injured kidney predominantly in peritubular region without acquiring tubular epithelial markers. Human AFS cells exerted antiapoptotic effect, activated Akt, and stimulated proliferation of tubular cells possibly via local release of factors, including interleukin-6, vascular endothelial growth factor, and stromal cell-derived factor-1, which we documented in vitro to be produced by hAFS cells. The therapeutic potential of hAFS cells was enhanced by cell pretreatment with glial cell line-derived neurotrophic factor (GDNF), which markedly ameliorated renal function and tubular injury by increasing stem cell homing to the tubulointerstitial compartment. By in vitro studies, GDNF increased hAFS cell production of growth factors, motility, and expression of receptors involved in cell homing and survival. These findings indicate that hAFS cells can promote functional recovery and contribute to renal regeneration in AKI mice via local production of mitogenic and prosurvival factors. The effects of hAFS cells can be remarkably enhanced by GDNF preconditioning.

Effects of structural properties of electrospun TiO 2 nanofiber meshes on their osteogenic potential

Ideal outcomes in the field of tissue engineering and regenerative medicine involve biomaterials that can enhance cell differentiation and production of local factors for natural tissue regeneration without the use of systemic drugs. Biomaterials typically used in tissue engineering applications include polymeric scaffolds that mimic the three-dimensional structural environment of the native tissue, but these are often functionalized with proteins or small peptides to improve their biological performance. For bone applications, titanium implants, or more appropriately the TiO 2 passive oxide layer formed on their surface, have been shown to enhance osteoblast differentiation in vitro and to promote osseointegration in vivo. In this study we evaluated the effect on osteoblast differentiation of pure TiO 2 nanofiber meshes with different surface microroughness and nanofiber diameters, prepared by the electrospinning method. MG63 cells were seeded on TiO 2 meshes, and cell number, differentiation markers and local factor production were analyzed. The results showed that cells grew throughout the entire surfaces and with similar morphology in all groups. Cell number was sensitive to surface microroughness, whereas cell differentiation and local factor production was regulated by both surface roughness and nanofiber diameter. These results indicate that scaffold structural cues alone can be used to drive cell differentiation and create an osteogenic environment without the use of exogenous factors.

감국(Chrysanthemum indicum L.) 추출물이 MC3T3-E1 조골세포의 증식 및 분화에 미치는 영향

Chrysanthemum indicum L. (Asteraceae) is a common traditional herbal medicine used for the treatment of inflammation, hypertension, and respiratory diseases due to its strong antagonistic function against inflammatory cytokines. In this study, the effects of Chrysanthemum indicum L. extract (CIE) on the function of osteoblastic MC3T3-E1 cells and the production of local factors in osteoblasts were investigated. CIE (100 ) significantly increased the growth of MC3T3-E1 cells and caused a significant elevation of alkaline phosphatase (ALP) activity, and the deposition of collagen and calcium in the cells (p tamoxifen, suggesting that CIE`s effect might be partly involved in estrogen-related activities. These results indicate that the enhancement of osteoblast functionality by CIE may prevent osteoporosis and inflammatory bone diseases.

Annulus Fibrosus Cells Interact with Neuron-like Cells to Modulate Production of Growth Factors and Cytokines in Symptomatic Disc Degeneration

Under normal conditions, the outer layers of the AF are innervated by sensory nerve endings from thedorsal root ganglion, whereas in patients with discogenic low back pain, sensory nerve endings and blood vessels are frequently observed in the inner layer of the AF and the nucleus pulposus (NP). Such nerve ingrowth and neovascularization is thought to be one of the major sources of discogenic low back pain and can occur as a consequence of the local production of angiogenic and neuronogenic factors in annular injury.

Growth factors and myometrium: biological effects in uterine fibroid and possible clinical implications

Growth factors are proteins secreted by a number of cell types that are capable of modulating cellular growth, proliferation and cellular differentiation. It is well accepted that uterine cellular events such as proliferation and differentiation are regulated by sex steroids and their actions in target tissues are mediated by local production of growth factors acting through paracrine and/or autocrine mechanisms. Myometrial mass is ultimately modified in pregnancy as well as in tumour conditions such as leiomyoma and leiomyosarcoma. Leiomyomas, also known as fibroids, are benign tumours of the uterus, considered to be one of the most frequent causes of infertility in reproductive years in women. For this review, we searched the database MEDLINE and Google Scholar for articles with content related to growth factors acting on myometrium; the findings are hereby reviewed and discussed. Different growth factors such as epidermal growth factor (EGF), transforming growth factor-α (TGF-α), heparin-binding EGF (HB-EGF), acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF) and TGF-β perform actions in myometrium and in leiomyomas. In addition to these growth factors, activin and myostatin have been recently identified in myometrium and leiomyoma. Growth factors play an important role in the mechanisms involved in myometrial patho-physiology.

Growth factors for periodontal regeneration

Periodontal tissue repair and regeneration are regulated by the local production of growth factors. However, naturally produced growth factors may not be sufficient to optimally stimulate periodontal regeneration. Exogenous growth factors can be used to supplement natural growth factors in wound healing. The authors focus on describing the mechanisms of five growth factors in periodontal regeneration: platelet-derived growth factor; fibroblast growth factor; transforming growth factor-beta; insulinlike growth factor; and bone morphogenetic protein. The objective is to encourage strategies to exploit growth factors in the stimulation of cells in periodontal regeneration, which should result from continued in vivo animal studies.

Abstract 1419: Role of p70S6K in breast cancer recurrence

Abstract In Early Breast Cancer (EBC) a single dose of intraoperative radiotherapy with TARGIT (Targeted Intraoperative RadioTherapy) protocol is as effective as the standard therapy in the control of local recurrences (Vaidya et al. Lancet, 376: 91-102, 2010). We recently demonstrated that TARGIT treatment affects the tumor microenvironment, after breast conserving surgery, by altering the local production of several growth factors and cytokines. Eventually, these changes in the proteomic profile, result in a lower activation of the p70S6K pathway in breast cancer cells (Belletti et al. CCR, 14: 1325-32, 2008). To dissect the role of p70S6K in breast cancer cells proliferation, motility and invasion, we generated genetically modified human breast cancer cell lines expressing specific shRNA or carrying a dominant negative form of p70S6K (p70KR) and tested their ability to grow and migrate, first in vitro then in vivo. Growth curve experiments on MDA MB 231 and MDA MB 453 mammary carcinoma cells, demonstrated that expression of the p70KR mutant slightly reduced the growth rate of these cells. The same cells have been also characterized for their ability to migrate in 2D- and 3D-contexts, in response to the wound fluids harvested from EBC patients as chemoattractants, showing that p70KR reduced their ability to invade. Next, we moved to an in vivo model to evaluate more in detail the involvement of p70S6K in the local recurrence of breast cancer. To this aim, parental or p70S6K genetically modified breast cancer cells have been injected in female nude mice mammary fat pads. Two weeks later, the tumor was removed by surgical excision and the mice observed for the appearance of recurrences. Macroscopic and histo-pathological examination of the primary tumors revealed that despite formation of similar masses, only tumors derived from parental cells displayed lymph-vascular invasion. More importantly, only mammary pads injected with parental cells developed recurrent disease and, at pathological analysis, displayed nodal metastasis. Altogether these data highlight a crucial function of p70S6K in the formation of local recurrence in breast cancers, and support the hypothesis that, in EBC patients, an anti-p70S6K specific therapy may be useful for the prevention of local recurrences. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1419. doi:10.1158/1538-7445.AM2011-1419

Ascorbic acid regulates osterix expression in osteoblasts by activation of prolyl hydroxylase and ubiquitination-mediated proteosomal degradation pathway

Mouse genetic studies reveal that ascorbic acid (AA) is essential for osteoblast (OB) differentiation and that osterix (Osx) was a key downstream target of AA action in OBs. To determine the molecular pathways for AA regulation of Osx expression, we evaluated if AA regulates Osx expression by regulating production and/or actions of local growth factors and extracellular matrix (ECM) proteins. Inhibition of actions of IGFs by inhibitory IGFBP-4, BMPs by noggin, and ECM-mediated integrin signaling by RGD did not block AA effects on Osx expression in OBs. Furthermore, blockade of components of MAPK signaling pathway had no effect on AA-induced Osx expression. Because AA is required for prolyl hydroxylase domain (PHD) activity and because PHD-induced prolyl-hydroxylation targets proteins to proteosomal degradation, we next tested if AA effect on Osx expression involves activation of PHD to hydroxylate and induce ubiquitin-proteosome-mediated degradation of transcriptional repressor(s) of Osx gene. Treatment of OBs with dimethyloxallyl glycine and ethyl 3, 4-dihydroxybenzoate, known inhibitors of PHD, completely blocked AA effect on Osx expression and OB differentiation. Knockdown of PHD2 expression by Lentivirus-mediated shRNA abolished AA-induced Osx induction and alkaline phosphatase activity. Furthermore, treatment of OBs with MG115, inhibitor of proteosomal degradation, completely blocked AA effects on Osx expression. Based on these data, we conclude that AA effect on Osx expression is mediated via a novel mechanism that involves PHD2 and proteosomal degradation of a yet to be identified transcriptional repressor that is independent of BMP, IGF-I, or integrin-mediated signaling in mouse OBs.

The effects of combined micron-/submicron-scale surface roughness and nanoscale features on cell proliferation and differentiation

Titanium (Ti) osseointegration is critical for the success of dental and orthopedic implants. Previous studies have shown that surface roughness at the micro- and submicro-scales promotes osseointegration by enhancing osteoblast differentiation and local factor production. Only relatively recently have the effects of nanoscale roughness on cell response been considered. The aim of the present study was to develop a simple and scalable surface modification treatment that introduces nanoscale features to the surfaces of Ti substrates without greatly affecting other surface features, and to determine the effects of such superimposed nano-features on the differentiation and local factor production of osteoblasts. A simple oxidation treatment was developed for generating controlled nanoscale topographies on Ti surfaces, while retaining the starting micro-/submicro-scale roughness. Such nano-modified surfaces also possessed similar elemental compositions, and exhibited similar contact angles, as the original surfaces, but possessed a different surface crystal structure. MG63 cells were seeded on machined (PT), nano-modified PT (NMPT), sandblasted/acid-etched (SLA), and nano-modified SLA (NMSLA) Ti disks. The results suggested that the introduction of such nanoscale structures in combination with micro-/submicro-scale roughness improves osteoblast differentiation and local factor production, which, in turn, indicates the potential for improved implant osseointegration in vivo.

Signals mediating skeletal muscle remodeling by resistance exercise: PI3-kinase independent activation of mTORC1

For over 10 years, we have known that the activation of the mammalian target of rapamycin complex 1 (mTORC1) has correlated with the increase in skeletal muscle size and strength that occurs following resistance exercise. Initial cell culture and rodent models of muscle growth demonstrated that the activation of mTORC1 is common to hypertrophy induced by growth factors and increased loading. The further observation that high loads increased the local production of growth factors led to the paradigm that resistance exercise stimulates the autocrine production of factors that act on membrane receptors to activate mTORC1, and this results in skeletal muscle hypertrophy. Over the last few years, there has been a paradigm shift. From both human and rodent studies, it has become clear that the phenotypic and molecular responses to resistance exercise occur in a growth factor-independent manner. Although the mechanism of load-induced mTORC1 activation remains to be determined, it is clear that it does not require classical growth factor signaling.

Sex dependent regulation of osteoblast response to implant surface properties by systemic hormones

BackgroundOsseointegration depends on the implant surface, bone quality and the local and systemic host environment, which can differ in male and female patients. This study was undertaken in order to determine if male and female cells respond differently to titanium surfaces that have micron-scale roughness and if interactions of calciotropic hormones [1α,25(OH)2D3 and 17β-oestradiol (E2)] and microstructured surfaces on osteoblasts are sex dependent.MethodsOsteoblasts from 6-week old Sprague-Dawley rats were cultured on tissue culture polystyrene (TCPS) or on titanium (Ti) disks with two different surface topographies, a smooth pretreated (PT) surface and a coarse grit-blasted/acid-etched (SLA) surface, and treated with 1α,25(OH)2D3, E2, or E2 conjugated to bovine serum albumin (E2-BSA).ResultsMale and female cells responded similarly to Ti microstructure with respect to cell number and levels of osteocalcin, transforming growth factor-β1, osteoprotegerin and prostaglandin E2 in their conditioned media, exhibiting a more differentiated phenotype on SLA than on PT or TCPS. E2 and E2-BSA increased differentiation and local factor production, an effect that was microstructure dependent and found only in female osteoblasts. 1α,25(OH)2D3 increased osteoblast differentiation and local factor production in female and male cells, but the effect was more robust in male cells.ConclusionsMale and female rat osteoblasts respond similarly to surface microstructure but exhibit sexual dimorphism in substrate-dependent responses to systemic hormones. Oestrogen affected only female cells while 1α,25(OH)2D3 had a greater effect on male cells. These results suggest that successful osseointegration in males and females may depend on the implant surface design and correct levels of calciotropic hormones.

The dependence of MG63 osteoblast responses to (meth)acrylate-based networks on chemical structure and stiffness

The cell response to an implant is regulated by the implant’s surface properties including topography and chemistry, but less is known about how the mechanical properties affect cell behavior. The objective of this study was to evaluate how the surface stiffness and chemistry of acrylate-based copolymer networks affect the in vitro response of human MG63 pre-osteoblast cells. Networks comprised of poly(ethylene glycol) dimethacrylate (PEGDMA; Mn ∼750) and diethylene glycol dimethacrylate (DEGDMA) were photopolymerized at different concentrations to produce three compositions with moduli ranging from 850 to 60 MPa. To further decouple chemistry and stiffness, three networks comprised of 2-hydroxyethyl methacrylate (2HEMA) and PEGDMA or DEGDMA were also designed that exhibited a range of moduli similar to the PEGDMA–DEGDMA networks. MG63 cells were cultured on each surface and tissue culture polystyrene (TCPS), and the effect of copolymer composition on cell number, osteogenic markers (alkaline phosphatase specific activity and osteocalcin), and local growth factor production (OPG, TGF-β1, and VEGF-A) were assessed. Cells exhibited a more differentiated phenotype on the PEGDMA–DEGDMA copolymers compared to the 2HEMA–PEGDMA copolymers. On the PEGDMA–DEGDMA system, cells exhibited a more differentiated phenotype on the stiffest surface indicated by elevated osteocalcin compared with TCPS. Conversely, cells on 2HEMA–PEGDMA copolymers became more differentiated on the less stiff 2HEMA surface. Growth factors were regulated in a differential manner. These results indicate that copolymer chemistry is the primary regulator of osteoblast differentiation, and the effect of stiffness is secondary to the surface chemistry.

Epidermal T Cells and Wound Healing

The murine epidermis contains resident T cells that express a canonical gammadelta TCR. These cells arise from fetal thymic precursors and use a TCR that is restricted to the skin in adult animals. These cells assume a dendritic morphology in normal skin and constitutively produce low levels of cytokines that contribute to epidermal homeostasis. When skin is wounded, an unknown Ag is expressed on damaged keratinocytes. Neighboring gammadelta T cells then round up and contribute to wound healing by local production of epithelial growth factors and inflammatory cytokines. In the absence of skin gammadelta T cells, wound healing is impaired. Similarly, epidermal T cells from patients with healing wounds are activated and secreting growth factors. Patients with nonhealing wounds have a defective epidermal T cell response. Information gained on the role of epidermal-resident T cells in the mouse may provide information for development of new therapeutic approaches to wound healing.

Maternal deprivation induces a rapid decline in circulating leptin levels and sexually dimorphic modifications in hypothalamic trophic factors and cell turnover

Pathological outcomes, including metabolic and endocrine disturbances, of maternal deprivation (MD) in Wistar rats depend on gender and the timing of deprivation during development. We analyzed the effect of MD between postnatal days 9 and 10, a critical period in hypothalamic development, on circulating hormones and local production of trophic factors involved in this process, as well as on markers of cell turnover and maturation. Males and females were studied 12 and 24 h after MD and 12 h (MD36) after returning the dam to her pups. Circulating corticosterone levels were increased and glucose and leptin levels decreased throughout the study in both sexes. Hypothalamic mRNA levels of leptin receptor increased significantly at MD24 in both sexes, normalizing in females at MD36, but not in males. In male rats insulin-like growth factor mRNA levels were significantly decreased at MD24 and brain derived neurotrophic factor mRNA levels decreased at MD12 and MD24, with both trophic factors unaffected in females. In males cell proliferation was significantly decreased at MD36, as were the glial structural proteins, glial fibrillary acidic protein and vimentin. In females, nestin levels decreased significantly at MD24. These results indicate that MD differently affects trophic factors and cell-turnover in the hypothalamus of males and females, which may underlie the sex differences seen in the endocrine and metabolic outcome.

Deletion of Tumor Necrosis Factor-α Receptor 1 (TNFR1) Protects against Diet-induced Obesity by Means of Increased Thermogenesis

In diet-induced obesity, hypothalamic and systemic inflammatory factors trigger intracellular mechanisms that lead to resistance to the main adipostatic hormones, leptin and insulin. Tumor necrosis factor-alpha (TNF-alpha) is one of the main inflammatory factors produced during this process and its mechanistic role as an inducer of leptin and insulin resistance has been widely investigated. Most of TNF-alpha inflammatory signals are delivered by TNF receptor 1 (R1); however, the role played by this receptor in the context of obesity-associated inflammation is not completely known. Here, we show that TNFR1 knock-out (TNFR1 KO) mice are protected from diet-induced obesity due to increased thermogenesis. Under standard rodent chow or a high-fat diet, TNFR1 KO gain significantly less body mass despite increased caloric intake. Visceral adiposity and mean adipocyte diameter are reduced and blood concentrations of insulin and leptin are lower. Protection from hypothalamic leptin resistance is evidenced by increased leptin-induced suppression of food intake and preserved activation of leptin signal transduction through JAK2, STAT3, and FOXO1. Under the high-fat diet, TNFR1 KO mice present a significantly increased expression of the thermogenesis-related neurotransmitter, TRH. Further evidence of increased thermogenesis includes increased O(2) consumption in respirometry measurements, increased expressions of UCP1 and UCP3 in brown adipose tissue and skeletal muscle, respectively, and increased O(2) consumption by isolated skeletal muscle fiber mitochondria. This demonstrates that TNF-alpha signaling through TNFR1 is an important mechanism involved in obesity-associated defective thermogenesis.

Pulsed electromagnetic fields stimulation affects BMD and local factor production of rats with disuse osteoporosis

Pulsed electromagnetic fields (PEMF) have been used widely to treat nonunion fractures and related problems in bone healing, as a biological and physical method. With the use of Helmholtz coils and PEMF stimulators to generate uniform time-varying electromagnetic fields, the effects of extremely low frequency electromagnetic fields on bone mineral density (BMD) and local factor production in disuse osteoporosis (DOP) rats were investigated. Eighty 4-month-old female Sprague Dawley (SD) rats were randomly divided into intact (INT) group, DOP group, calcitonin-treated (CT) group, and PEMF stimulation group. The right hindlimbs of all the rats were immobilized by tibia-tail fixation except for those rats in the INT group. Rats in the CT group were injected with calcitonin (2 IU/kg, i.p., once a day) and rats in the PEMF group were irradiated with PEMF immediately postoperative. The BMD, serum transforming growth factor-beta 1 (TGF-beta1), and interleukin-6 (IL-6) concentration of the proximal femur were measured 1, 2, 4, and 8 weeks after treatment. Compared with the CT and DOP groups, the BMD and serum TGF-beta1 concentration in the PEMF group increased significantly after 8 weeks. The IL-6 concentration in the DOP group was elevated significantly after operation. The PEMF group showed significantly lower IL-6 level than the DOP group. The results found demonstrate that PEMF stimulation can efficiently suppress bone mass loss. We, therefore, conclude that PEMF may affect bone remodeling process through promoting TGF-beta1 secretion and inhibiting IL-6 expression.

Stimulation of osteoblastic differentiation and inhibition of interleukin‐6 and nitric oxide in MC3T3‐E1 cells by pomegranate ethanol extract

In this experiment, we studied the effects of pomegranate fruit extract (PE) on the function of osteoblastic MC3T3-E1 cells and the production of local factors in osteoblasts. PE (16 approximately 250 microg/ml) significantly increased the growth of MC3T3-E1 cells (P < 0.05). Moreover, PE (50 microg/ml) caused a significant elevation of alkaline phosphatase (ALP) activity and collagen content in the cells. We then examined the effect of PE on the TNF-alpha-induced production of interleukin-6 (IL-6) and nitric oxide (NO) in osteoblasts. Treatment with PE (10 approximately 50 microg/ml) decreased the TNF-alpha (10(-10) M)-induced production of IL-6 and NO in osteoblasts.

Arachidonic Acid and Prostaglandin E2 Influence Human Osteoblast (MG63) Response to Titanium Surface Roughness

Prior studies have shown that implant surface roughness affects osteoblast proliferation, differentiation, matrix synthesis, and local factor production. Further, cell response is modulated by systemic factors, such as 1,25(OH)2D3 and estrogen as well as mechanical forces. Based on the fact that peri-implant bone healing occurs in a site containing elevated amounts of prostaglandin E2 (PGE2), the hypothesis of the current study is that PGE2 and arachidonic acid (AA), the substrate used by cyclooxygenase to form PGE2, influence osteoblast response to implant surface roughness. To test this hypothesis, 4 different types of commercially pure titanium (cpTi) disks with surfaces of varying roughness (smooth Ti, R(a) 0.30 microm; smooth and acid etched Ti [SAE Ti], R(a) 0.40 microm; rough Ti, R(a) 4.3 microm; rough and acid etched Ti [RAE Ti], R(a) 4.15 (microm) were prepared. MG63 osteoblasts were seeded onto the surfaces, cultured to confluence, and then treated for the last 24 hours of culture with AA (0, 0.1, 1, and 10 nM), PGE2 (0, 1, 10, 25, and 100 nM), or the general cyclooxygenase inhibitor indomethacin (0 or 100 nM). At harvest, the effect of treatment on cell proliferation was assessed by measuring cell number and [3H]-thymidine incorporation, and the effect on cell differentiation was determined by measuring alkaline phosphatase (ALP) specific activity. The effect of AA and PGE2 on cell number was somewhat variable but showed a general decrease on plastic and smooth surfaces and an increase on rough surfaces. In contrast, [3H]-thymidine incorporation was uniformly decreased with treatment on all surfaces. ALP demonstrated the most prominent effect of treatment. On smooth surfaces, AA and PGE2 dose-dependently increased ALP, while on rough surfaces, treatment dose-dependently decreased enzyme specific activity. Indomethacin treatment had either no effect or a slightly inhibitory effect on [3H]-thymidine incorporation on all surfaces. In contrast, indomethacin inhibited ALP on smooth surfaces and stimulated ALP on rough. Taken together, the results indicate that both AA and PGE2 influence osteoblast response by promoting osteoblast differentiation on smooth surfaces, while inhibiting it on rough surfaces. Because implants with rough surfaces are acknowledged to be superior to those with smooth surfaces, these results suggest that use of nonsterioidal anti-inflammatory drugs to block PGE2 production and reduce inflammation may be beneficial in the postoperative period after implant placement. They also indicate that manipulation of the AA metabolic pathway may offer a new therapeutic approach for modulating bone healing after implant placement. Because peri-implant healing takes place in a complex cellular environment quite different from the one used in the present study, additional work will be necessary to substantiate these possibilities.