Polypeptide Growth Factors Research Articles

Small Molecules Dorsomorphin and LDN-193189 Inhibit Myostatin/GDF8 Signaling and Promote Functional Myoblast Differentiation

GDF8, or myostatin, is a member of the TGF-β superfamily of secreted polypeptide growth factors. GDF8 is a potent negative regulator of myogenesis both in vivo and in vitro. We found that GDF8 signaling was inhibited by the small molecule ATP competitive inhibitors dorsomorphin and LDN-193189. These compounds were previously shown to be potent inhibitors of BMP signaling by binding to the BMP type I receptors ALK1/2/3/6. We present the crystal structure of the type II receptor ActRIIA with dorsomorphin and demonstrate that dorsomorphin or LDN-193189 target GDF8 induced Smad2/3 signaling and repression of myogenic transcription factors. As a result, both inhibitors rescued myogenesis in myoblasts treated with GDF8. As revealed by quantitative live cell microscopy, treatment with dorsomorphin or LDN-193189 promoted the contractile activity of myotubular networks in vitro. We therefore suggest these inhibitors as suitable tools to promote functional myogenesis.

Insulin-like growth factor and epidermal growth factor signaling in breast cancer cell growth: focus on endocrine resistant disease.

Breast cancer is the most common type of cancer for women worldwide with a lifetime risk amounting to a staggering total of 10%. It is well established that the endogenous synthesis of insulin-like growth factor (IGF) and epidermal growth factor (EGF) polypeptide growth factors are closely correlated to malignant transformation and all the steps of the breast cancer metastatic cascade. Numerous studies have demonstrated that both estrogens and growth factors stimulate the proliferation of steroid-dependent tumor cells, and that the interaction between these signaling pathways occurs at several levels. Importantly, the majority of breast cancer cases are estrogen receptor- (ER-) positive which have a more favorable prognosis and pattern of recurrence with endocrine therapy being the backbone of treatment. Unfortunately, the majority of patients progress to endocrine therapy resistant disease (acquired resistance) whereas a proportion of patients may fail to respond to initial therapy (de novo resistance). The IGF-I and EGF downstream signaling pathways are closely involved in the process of progression to therapy resistant disease. Modifications in the bioavailability of these growth factors contribute critically to disease progression. In the present review therefore, we will discuss in depth how IGF and EGF signaling participate in breast cancer pathogenesis and progression to endocrine resistant disease.

Expression of Fgf23 in activated dendritic cells and macrophages in response to immunological stimuli in mice.

Fibroblast growth factors (Fgfs) are polypeptide growth factors with diverse biological activities. While several studies have revealed that Fgf23 plays important roles in the regulation of phosphate and vitamin D metabolism, the additional physiological roles of Fgf23 remain unclear. Although it is believed that osteoblasts/osteocytes are the main sources of Fgf23, we previously found that Fgf23 mRNA is also expressed in the mouse thymus, suggesting that it might be involved in the immune system. In this study we examined the potential roles of Fgf23 in immunological responses. Mouse serum Fgf23 levels were significantly increased following inoculation with Escherichia coli or Staphylococcus aureus or intraperitoneal injection of lipopolysaccharide. We also identified activated dendritic cells and macrophages that potentially contributed to increased serum Fgf23 levels. Nuclear factor-kappa B (NF-κB) signaling was essential for the induction of Fgf23 expression in dendritic cells in response to immunological stimuli. Moreover, we examined the effects of recombinant Fgf23 protein on immune cells in vitro. Fgfr1c, a potential receptor for Fgf23, was abundantly expressed in macrophages, suggesting that Fgf23 might be involved in signal transduction in these cells. Our data suggest that Fgf23 potentially increases the number in macrophages and induces expression of tumor necrosis factor-α (TNF-α), a proinflammatory cytokine. Collectively, these data suggest that Fgf23 might be intimately involved in inflammatory processes.

Protein Expression of theBombyx mori DecapentaplegicGene using the Baculovirus Expression Vector System

The Bombyx mori decapentaplegic gene is one of the conserved genes in vertebrate and invertebrates. The TGF-β superfamily contains conserved polypeptide growth factors that play important roles in different cellular processes such as proliferation, apoptosis, differentiation and cell-fate determination. The B. mori dpp gene shares genetic homology with hBMPs and Drosophila dpp. Until now, only few studies have been conducted to examine the functions of B. mori dpp; and hence, its function is not yet well understood. In this study, the baculovirus expression vector system (BEVS) was used for expression of the recombinant B. mori dpp protein and in which the recombinant baculovirus is recovered in the host Sf9 cells. The selected pure recombinant baculovirus containing B. mori dpp gene (rBV-egfp-Bm dpp) was used to increase the effective protein purification by using His-tag extraction strategy. After selection of recombinant baculovirus, recombinant B. mori dpp proteins were extracted from the re-infected cells with pure rBV-egfp-Bm dpp. Herein, we summarize the efficient expression and purification of B. mori dpp proteins from the insect cells using the BEVS. This recombinant protein could be suitable for functional test and various application studies.

Fibroblast growth factors and their role in disease and therapy

Fibroblast growth factors (FGFs) make up a large family of multifunctional polypeptide growth factors of which there are 22 distinct members. The FGF family shows a high affinity for heparin and also interacts with FGF receptors. FGF can be classified into subgroups according to structures, biochemical properties, and expression. Members of FGF family have been identified in a variety of organisms, and they play a significant role in many cellular processes including mitogenesis differentiation, migration, and cell survival. However, it also has the potentiality to induce oral neoplasms, and various FGFs can be used for therapeutic purpose as well. This review discusses the basic mechanism for FGF action, and their receptors, various functions of FGFs in normal development, their role in cancer formation along with oral diseases and treatment.

Alteration in messenger RNA neurotrophin 4 and tyrosine kinase receptors B expression levels following spinal cord injury.

Neurotrophins as polypeptide growth factors have important roles during nervous system development and are involved in neuronal differentiation and survival and spinal cord reorganization. Neurotrophins have been recognized as factors which are involved in the development of damaged axons and increase the axon growth ability and neuroplasticity. Spinal cord injury (SCI) is associated with numerous physiological damages, leading to neuron death, axon extended destruction healthy and intact neurons demyelination, inflammation, cell death and severe motor/sensory defects. The aim of this study was to investigate the alteration in messenger RNA neurotrophin 4 and tyrosine kinase receptors B expression levels following SCI. In this research, to know expression level alterations of neurotrophin 4 mRNA and its receptor Trk- B at 6 hours and 1, 3, 7 and 10 days after SCI, we developed competitive RT-qPCR. mRNA was extracted from T9 injury site (epicenter, rostral and caudal to the epicenter) and reversed to cDNA. The results showed that the expression of these genes changed after SCI. The NT4 mRNA expression level in the rostral to the epicenter decreased after enhancement in the 1st 6 hours. At the epicenter and in the caudal to the epicenter, it decreased. mRNA expression level of Trk-B decreased after an increase in the initial hours in all the areas. The present results showed that NT4 and Trk-B are expressed temporary and spatially following SCI and the adjustment of these neurotrophins rate in SCI may provide therapeutic benefits.

Recent Trends in Non-Surgical Periodontal Care for the General Dentist - A Review

The management of periodontal defects has been an ongoing challenge in clinical periodontics. In the recent past, attention has been focused more on regenerative and reconstructive therapies i.e. bone grafts, guided tissue regeneration, root conditioning, polypeptide growth factors, rather than on respective therapies. These therapeutic measures are shown to be limited in the predictability of healing and regenerative response in the modem clinical practice because oral environment presents several complicating factors that border regeneration. The 21st century appears to represent a time in history when there is a convergence between clinical dentistry and medicine, human genetics, developmental and molecular biology, biotechnology, bioengineering, and bioinformatics, resulting in the emergence of novel regenerative therapeutic approaches and focusing mainly on non surgical modalities. The purpose of this article is to provide a review of the various non surgical therapies in use today. Future direction in this ever-changing field is also discussed. Techniques currently in use are reviewed and evaluated. They include Probiotics, Ozone therapy, Photodynamic therapy, Gene therapy, RNA interference, Nanotechnology, Perioprotect, TIPS & BOST. DOI: http://dx.doi.org/10.3329/bjdre.v4i2.20254 Bangladesh Journal of Dental Research and Education Vol.4(2) 2014: 78-82

Platelet-derived Growth Factors and Receptors in Canine Lymphoma

Platelet-derived growth factors (PDGFs) belong to a family of polypeptide growth factors that signal through cell surface tyrosine kinase receptors to stimulate growth, proliferation and differentiation. Platelet-derived growth factor receptors (PDGFRs) are also considered important targets for specific kinase inhibitors in the treatment of several human tumours. The aim of this study was to investigate the role of PDGF-A, PDGF-B, PDGFR-α and PDGFR-β in canine lymphoma by determining gene and protein expression in lymph nodes of dogs with diffuse large B-cell lymphoma (DLBCL), peripheral T-cell lymphoma (PTCL), T-lymphoblastic lymphoma (T-LBL) and in healthy control dogs. One lymph node was also studied at the end of therapy in a subset of dogs in remission for DLBCL. In controls, PDGF-A, PDGFR-α and PDGFR-β mRNA levels were significantly higher than in DLBCLs, PTCLs and T-LBLs. However, PDGFR-α and PDGFR-β were minimally expressed by lymphocytes and plasma cells in normal lymph nodes as determined by immunohistochemistry, while neoplastic B and T cells showed the highest score (P <0.05). This discordant result may be compatible with the constitutive expression of these molecules by endothelial cells and fibroblasts in normal lymph nodes, thereby influencing gene expression results. Furthermore, these cells were not included in the immunohistochemical analysis. Similarly, dogs with DLBCL that were in remission at the end of therapy showed significantly higher gene expression of PDGFs and receptors than at the time of diagnosis and with an opposite trend to the protein assay. PDGF-B protein and mRNA were overexpressed in PTCLs and T-LBLs when compared with DLBCLs and controls (P <0.05). Additionally, there was a correlation between protein expression of PDGF-B and both PDGFRs in PTCLs and T-LBLs, suggesting an autocrine or paracrine loop in the aetiology of aggressive canine T-cell lymphomas. These data provide a rationale for the use of PDGFR antagonists in the therapy of aggressive T-cell lymphomas, but not in DLBCLs.

Oncomodulin/truncated protamine-mediated Nogo-66 receptor small interference RNA delivery promotes axon regeneration in retinal ganglion cells.

The optic nerve often suffers regenerative failure after injury, leading to serious visual impairment such as glaucoma. The main inhibitory factors, including Nogo-A, oligodendrocyte myelin glycoprotein, and myelin-associated glycoprotein, exert their inhibitory effects on axonal growth through the same receptor, the Nogo-66 receptor (NgR). Oncomodulin (OM), a calcium-binding protein with a molecular weight of an ∼12 kDa, which is secreted from activated macrophages, has been demonstrated to have high and specific affinity for retinal ganglion cells (RGC) and promote greater axonal regeneration than other known polypeptide growth factors. Protamine has been reported to effectively deliver small interference RNA (siRNA) into cells. Accordingly, a fusion protein of OM and truncated protamine (tp) may be used as a vehicle for the delivery of NgR siRNA into RGC for gene therapy. To test this hypothesis, we constructed OM and tp fusion protein (OM/tp) expression vectors. Using the indirect immunofluorescence labeling method, OM/tp fusion proteins were found to have a high affinity for RGC. The gel shift assay showed that the OM/tp fusion proteins retained the capacity to bind to DNA. Using OM/tp fusion proteins as a delivery tool, the siRNA of NgR was effectively transfected into cells and significantly down-regulated NgR expression levels. More importantly, OM/tp-NgR siRNA dramatically promoted axonal growth of RGC compared with the application of OM/tp recombinant protein or NgR siRNA alone in vitro. In addition, OM/tp-NgR siRNA highly elevated intracellular cyclic adenosine monophosphate (cAMP) levels and inhibited activation of the Ras homolog gene family, member A (RhoA). Taken together, our data demonstrated that the recombinant OM/tp fusion proteins retained the functions of both OM and tp, and that OM/tp-NgR siRNA might potentially be used for the treatment of optic nerve injury.

Induction of serpinb1a by PACAP or NGF is required for PC12 cells survival after serum withdrawal.

PC12 cells are used to study the signaling mechanisms underlying the neurotrophic and neuroprotective activities of pituitary adenylate cyclase-activating polypeptide (PACAP) and nerve growth factor (NGF). Previous microarray experiments indicated that serpinb1a was the most induced gene after 6 h of treatment with PACAP or NGF. This study confirmed that serpinb1a is strongly activated by PACAP and NGF in a time-dependent manner with a maximum induction (~ 50-fold over control) observed after 6 h of treatment. Co-incubation with PACAP and NGF resulted in a synergistic up-regulation of serpinb1a expression (200-fold over control), suggesting that PACAP and NGF act through complementary mechanisms. Consistently, PACAP-induced serpinb1a expression was not blocked by TrkA receptor inhibition. Nevertheless, the stimulation of serpinb1a expression by PACAP and NGF was significantly reduced in the presence of extracellular signal-regulated kinase, calcineurin, protein kinase A, p38, and PI3K inhibitors, indicating that the two trophic factors share some common pathways in the regulation of serpinb1a. Finally, functional investigations conducted with siRNA revealed that serpinb1a is not involved in the effects of PACAP and NGF on PC12 cell neuritogenesis, proliferation or body cell volume but mediates their ability to block caspases 3/7 activity and to promote PC12 cell survival.

Epidermal growth factor induces platelet-activating factor production through receptors transactivation and cytosolic phospholipase A2 in ovarian cancer cells

BackgroundAmong the pro-inflammatory lipid mediators, platelet-activating factor (PAF) is a major primary and secondary messenger that binds to the PAF-receptor (PAFR). Epidermal growth factor (EGF) is a polypeptide growth factor that binds to the EGF-receptor (EGFR). Evidence suggests that both PAF and EGF play a significant role in oncogenic transformation, tumor growth, neoangiogenesis and metastasis, including ovarian cancer. PAF has the potential to transactivate EGFR in ovarian cancer cells. This study explores the mechanisms involved in EGF-induced PAF production.MethodsThe effect of EGF on PAF production in ovarian cancer cells was observed using enzyme-linked immunosorbent assay. The receptors transactivation and the role of cytosolic phospholipase A2 (cPLA2) in modulating PAF production induced by EGF was assessed using pharmacological inhibitors, si-RNA knockdown, targeted gene overexpression and immunocytochemistry. The signaling pathways invovled in PAF production induced by EGF in ovarian cancer cells were assessed.ResultsWe demonstrate that EGF increases the production of PAF in CAOV3 and SKOV3 ovarian cancer cell lines. EGF induces the transactivation of PAFR, which can be blocked by an EGFR inhibitor. Inhibition of EGFR and/or PAFR blocks PAF production in response to EGF. EGF-induced PAF production involves the phosphorylation of extracellular-regulated protein kinase (ERK) and cytosolic phospholipase A2 (cPLA2). A cPLA2 inhibitor blocks EGF-induced PAF production as well as si-cPLA2, while overexpression of cPLA2 increases PAF production.ConclusionsThese results indicate that EGF stimulates PAF production in ovarian cancer cells in a manner that requires cPLA2. We have also determined that crosstalk can occur bidirectionally between EGFR and PAFR, suggesting that EGF-induced PAF production could result in positive feedback that acts on the PAF-receptor to promote ovarian cancer progression.

An Investigation of the Relationship between Pelvic Pain and Density of Nerve Fibers in Peritoneal Lesions of Endometriosis

Purpose Endometriosis is a gynecological disease often characterized by severe pelvic pain, including perimenstrual and intermenstrual pain and dyspareunia. Sensory nerve fibers within peritoneal lesions have previously been shown to contribute to generation of pain in endometriosis; however, their association with different types of pelvic pain is currently uncertain. Methods Peritoneal endometriotic lesions (n = 30) were sectioned and stained immunohistochemically with protein gene product 9.5 (PGP 9.5; pan-neuronal marker), neuropeptide Y (NPY; sympathetic), vasoactive intestinal polypeptide (VIP; parasympathetic), substance P (SP; sensory) and nerve growth factor (NGF) to identify nerve fibers and neurotrophin levels. Densities were assessed within stroma of the lesions and in the adjacent peritoneum. Pelvic pain scores were obtained using a visual analogue scale (VAS), and correlation analysis was performed. Results Increased density of nerve fibers was observed within the stroma of lesions. NGF expression was significantly increased in glandular epithelium, compared with stromal regions (p = 0.026) and correlated inversely with menstrual pain scores (p = 0.05). Sympathetic nerve fiber density (NPY) in stroma showed a significant positive correlation with intensity of menstrual pain (p = 0.04). Parasympathetic nerve fiber density (VIP) also showed a strong trend toward a positive correlation with menstrual pain intensity (p = 0.056). Conclusions There is increased neurogenesis in the stromal region. Innervation of lesions correlates to intensity of menstrual pain. NGF in glandular epithelium may promote growth of nerve fibers into the core of lesions; however, the inverse correlation between NGF expression in glandular epithelium and menstrual pain indicates that mechanisms of pain generation in endometriosis are complex.

Cell signalling molecules

All periodontal cells are capable of expressing a broad range of gene products, including matrix proteins, proteases involved in tissue remodeling (such as collagenases) and cytokines. Mesenchymal cells in the periodontal connective tissues encounter a complex array of stimuli that include soluble agents (such as polypeptide growth factors, cytokines, neuropeptide and chemotherapeutic agents), insoluble extracellular matrix proteins and other cells. The mechanisms that permit cells to respond to extracellular stimuli are essential for normal growth and function. Characterization of how these pathways are up-regulated or down-regulated in response to other agents may eventually allow the predictability of periodontal regeneration to be enhanced. The current review aims to provide a comprehensive overview to the various cell signaling pathways and molecules that mediate the periodontal disease process and can serve as a target for periodontal therapy.

BMP growth factor signaling in a biomechanical context

Bone Morphogenetic Proteins (BMPs) are members of the transforming growth factor-β superfamily of secreted polypeptide growth factors and are important regulators in a multitude of cellular processes. To ensure the precise and balanced propagation of their pleiotropic signaling responses, BMPs and their corresponding signaling pathways are subject to tight control. A large variety of regulatory mechanisms throughout different biological levels combines into a complex network and provides the basis for physiological BMP function. This regulatory network not only includes biochemical factors but also mechanical cues. Both BMP signaling and mechanotransduction pathways are tightly interconnected and represent an elaborate signaling network active during development but also during organ homeostasis. Moreover, its dysregulation is associated with a number of human pathologies. A more detailed understanding of this crosstalk in respect to molecular interactions will be indispensable in the future, in particular to understand BMP-related diseases as well as with regard to an efficient clinical application of BMP ligands.

High Yield Production of a Soluble Human Interleukin-3 Variant from E. coli with Wild-Type Bioactivity and Improved Radiolabeling Properties

Human interleukin-3 (hIL-3) is a polypeptide growth factor that regulates the proliferation, differentiation, survival and function of hematopoietic progenitors and many mature blood cell lineages. Although recombinant hIL-3 is a widely used laboratory reagent in hematology, standard methods for its preparation, including those employed by commercial suppliers, remain arduous owing to a reliance on refolding insoluble protein expressed in E. coli. In addition, wild-type hIL-3 is a poor substrate for radio-iodination, which has been a long-standing hindrance to its use in receptor binding assays. To overcome these problems, we developed a method for expression of hIL-3 in E. coli as a soluble protein, with typical yields of >3mg of purified hIL-3 per litre of shaking microbial culture. Additionally, we introduced a non-native tyrosine residue into our hIL-3 analog, which allowed radio-iodination to high specific activities for receptor binding studies whilst not compromising bioactivity. The method presented herein provides a cost-effective and convenient route to milligram quantities of a hIL-3 analog with wild-type bioactivity that, unlike wild-type hIL‑3, can be efficiently radio-iodinated for receptor binding studies.

Fibroblast Growth Factor (FGF): A Review

AbstractIn order for periodontal regeneration to occur, progenitor cells must migrate to the denuded root surface, attach to it, proliferate and mature into an organized and functional fibrous attachment apparatus. Significant advances have been made during the last decade in understanding the factors controlling the migration, attachment and proliferation of cells. A group of naturally occurring molecules known as polypeptide growth factors in conjunction with certain matrix proteins, are key regulators of these biological events. Of these, the fibroblast growth factors (FGFs) appear to have an important role in periodontal wound healing. The purpose of this review is to summarize current information on these growth factors with emphasis on their potential implications in periodontal wound healing and regeneration.

Astrocyte-Specific Overexpression of Insulin-Like Growth Factor-1 Protects Hippocampal Neurons and Reduces Behavioral Deficits following Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) survivors often suffer from long-lasting cognitive impairment that stems from hippocampal injury. Systemic administration of insulin-like growth factor-1 (IGF-1), a polypeptide growth factor known to play vital roles in neuronal survival, has been shown to attenuate posttraumatic cognitive and motor dysfunction. However, its neuroprotective effects in TBI have not been examined. To this end, moderate or severe contusion brain injury was induced in mice with conditional (postnatal) overexpression of IGF-1 using the controlled cortical impact (CCI) injury model. CCI brain injury produces robust reactive astrocytosis in regions of neuronal damage such as the hippocampus. We exploited this regional astrocytosis by linking expression of hIGF-1 to the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter, effectively targeting IGF-1 delivery to vulnerable neurons. Following brain injury, IGF-1Tg mice exhibited a progressive increase in hippocampal IGF-1 levels which was coupled with enhanced hippocampal reactive astrocytosis and significantly greater GFAP levels relative to WT mice. IGF-1 overexpression stimulated Akt phosphorylation and reduced acute (1 and 3d) hippocampal neurodegeneration, culminating in greater neuron survival at 10d after CCI injury. Hippocampal neuroprotection achieved by IGF-1 overexpression was accompanied by improved motor and cognitive function in brain-injured mice. These data provide strong support for the therapeutic efficacy of increased brain levels of IGF-1 in the setting of TBI.

Proteomic analysis of NGF-induced transdifferentiation of adrenal medullary cells

Nerve growth factor (NGF) is a polypeptide growth factor with specific trophic function in nerve cells and was initially investigated for its role as a key player in the regulation of peripheral innervations. The aim of this study was to examine the NGF-induced transdifferentiation of adrenal medullary cells, and to screen the major candidate differentially expressed proteins involved in the transdifferentiation. NGF was used to treat primary cultures of neonatal calf adrenal medullary cells and the effects of transdifferentiation were determined in association with cellular morphology, ultrastructure and changes in endocrine function. Differentially expressed proteins were screened and identified through two-dimensional gel electrophoresis and mass spectrometry. The protein spots showing differential expression were verified by western blot analysis. We observed neurite outgrowth in the adrenal medullary cells treated with NGF under a phase contrast microscope. Ultrastructure analysis revealed that there were rich drumstick-like and villiform processes on the cell membranes and vesicles were formed near the cell membranes. The cytoplasm was rich in mitochondria and the secretion of epinephrine was decreased. Two-dimensional gel electrophoresis revealed that among the differentially expressed proteins, 48 protein spots showed an upregulated expression and 37 protein spots showed a downregulated expression, and no 'all-or-none' spots with significant differences in expression were found. Fourteen protein spots with an upregulated expression and 6 with a downregulated expression were randomly selected for identification by mass spectrometry. Western blot analysis revealed that ras homologus oncogene (Rho) GDP dissociation inhibitor α (RhoGDIα) protein expression was significantly downregulated and peripherin protein expression was significantly upregulated. In brief, our data demonstrate that NGF can induce the differentiation of adrenal medullary cells into neurons, and that RhoGDIα and peripherin may play important roles in this process.

Aptamers and Their Potential to Selectively Target Aspects of EGF, Wnt/β-Catenin and TGFβ–Smad Family Signaling

The smooth identification and low-cost production of highly specific agents that interfere with signaling cascades by targeting an active domain in surface receptors, cytoplasmic and nuclear effector proteins, remain important challenges in biomedical research. We propose that peptide aptamers can provide a very useful and new alternative for interfering with protein–protein interactions in intracellular signal transduction cascades, including those emanating from activated receptors for growth factors. By their targeting of short, linear motif type of interactions, peptide aptamers have joined nucleic acid aptamers for use in signaling studies because of their ease of production, their stability, their high specificity and affinity for individual target proteins, and their use in high-throughput screening protocols. Furthermore, they are entering clinical trials for treatment of several complex, pathological conditions. Here, we present a brief survey of the use of aptamers in signaling pathways, in particular of polypeptide growth factors, starting with the published as well as potential applications of aptamers targeting Epidermal Growth Factor Receptor signaling. We then discuss the opportunities for using aptamers in other complex pathways, including Wnt/β-catenin, and focus on Transforming Growth Factor-β/Smad family signaling.

Growth factor transgenes interactively regulate articular chondrocytes

Adult articular chondrocytes lack an effective repair response to correct damage from injury or osteoarthritis. Polypeptide growth factors that stimulate articular chondrocyte proliferation and cartilage matrix synthesis may augment this response. Gene transfer is a promising approach to delivering such factors. Multiple growth factor genes regulate these cell functions, but multiple growth factor gene transfer remains unexplored. We tested the hypothesis that multiple growth factor gene transfer selectively modulates articular chondrocyte proliferation and matrix synthesis. We tested the hypothesis by delivering combinations of the transgenes encoding insulin-like growth factor I (IGF-I), fibroblast growth factor-2 (FGF-2), transforming growth factor beta1 (TGF-β1), bone morphogenetic protein-2 (BMP-2), and bone morphogenetic protien-7 (BMP-7) to articular chondrocytes and measured changes in the production of DNA, glycosaminoglycan, and collagen. The transgenes differentially regulated all these chondrocyte activities. In concert, the transgenes interacted to generate widely divergent responses from the cells. These interactions ranged from inhibitory to synergistic. The transgene pair encoding IGF-I and FGF-2 maximized cell proliferation. The three-transgene group encoding IGF-I, BMP-2, and BMP-7 maximized matrix production and also optimized the balance between cell proliferation and matrix production. These data demonstrate an approach to articular chondrocyte regulation that may be tailored to stimulate specific cell functions, and suggest that certain growth factor gene combinations have potential value for cell-based articular cartilage repair.