Controlled release of NFkappaB decoy oligonucleotides from biodegradable polymer microparticles

The objective of this study was to evaluate a poly(DL-lactic-co-glycolic acid)/poly(ethylene glycol) (PLGA/PEG) delivery system for nuclear factor-kappa B (NFkappaB) decoy phosphorothioated oligonucleotides (ODNs). PLGA/PEG microparticles loaded with ODNs were fabricated with entrapment efficiencies up to 70%. The effects of PEG contents (0, 5, and l0 wt%), ODN loading densities (0.4, 4, and 40 microg/mg), and pH of the incubation medium (pH 5, 7.4. and 10) on ODN release kinetics from the PLGA/PEG microparticles were investigated in vitro for up to 28 days. The release profiles in pH 7.4 phosphate buffered saline (PBS) were characterized by an initial burst during the first 2 days, a linear release phase until day 18, and a final release phase for the rest of the period. Up to 85% of the ODNs were released after 28 days in pH 7.4 PBS regardless of the ODN loading density and PEG content. Higher ODN loading densities resulted in lower entrapment efficiencies and greater initial burst effects. The bulk degradation of PLGA was not significantly affected by the PEG content and ODN loading density, but significantly accelerated at acidic buffer pH. Under acidic and basic conditions, the aggregation of microparticles resulted in significantly lower cumulative mass of released ODNs than that released at neutral pH. The effects of pH were reduced by the incorporation of PEG into PLGA microparticles. Since the PLGA degradation products are acidic, PLGA/PEG microparticles might provide a better ODN delivery vehicle than PLGA microparticles. These results suggest that PLGA/PEG microparticles are useful as delivery vehicles for controlled release of ODNs and merit further investigation in cell culture and animal models of glioblastoma.     

Effects of transforming growth factor beta1 released from biodegradable polymer microparticles on marrow stromal osteoblasts cultured on poly(propylene fumarate) substrates

Recombinant human transforming growth factor beta1 (TGF-beta1) was incorporated into microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) to create a delivery vehicle for the growth factor. The entrapment efficiency of TGF-beta1 in the microparticles containing 5% PEG was 40.3 +/- 1.2% for a TGF-beta1 loading density of 6.0 ng/1 mg of microparticles. For the same loading, 17.9 +/- 0.6 and 32.1 +/- 2.5% of the loaded TGF-beta1 was released after 1 and 8 days, respectively, followed by a plateau for the remaining 3 weeks. Rat marrow stromal cells showed a dose response to TGF-beta1 released from the microparticles similar to that of added TGF-beta1, indicating the activity of TGF-beta1 was retained during microparticle fabrication and after TGF-beta1 release. An optimal TGF-beta1 dosage of 1.0 ng/mL was determined through a 3-day dose response study for maximal alkaline phosphatase (ALP) activity. The TGF-beta1 released from the microparticles loaded with 6.0 ng TGF-beta1/1 mg of microparticles for the optimal dosage of TGF-beta1 enhanced the proliferation and osteoblastic differentiation of marrow stromal cells cultured on poly(propylene fumarate) substrates. The cells showed significantly increased total cell number, ALP activity, and osteocalcin production with values reaching 138,700 +/- 3300 cells/cm(2), 22.8 +/- 1.5 x 10(-7) micromol/min/cell, and 15.9 +/- 1.5 x 10(-6) ng/cell, respectively, after 21 days as compared to cells cultured under control conditions without TGF-beta1. These results suggest that controlled release of TGF-beta1 from the PLGA/PEG blend microparticles may find applications in modulating cellular response during bone healing at a skeletal defect site.     

Controlled release of bioactive transforming growth factor beta-1 from fibrin gels in vitro

This study analyzed the ability of fibrin gels to deliver added recombinant transforming growth factor beta-1 (TGF-beta1) in a controlled manner and biologically active form. First, the effects of the amount of TGF-beta1 on the release kinetics were analyzed using a single fibrin gel formulation (fibrinogen complex (FC) at 25 mg/mL, thrombin at 2 IU/mL). Then, the effects of FC and thrombin concentrations were analyzed. Finally, to test the biological activity of the released TGF-beta1 from the gels, medium supernatants taken from gels at day 3 were used as culture medium for human mesenchymal stem cell (HMSC) monolayers. Cell proliferation was analyzed after staining with calcein dye, and changes in cell morphology were observed under fluorescence microscopy at days 1, 4, and 7. At day 7, HMSC chondrogenic differentiation was assessed by Alcian Blue staining and osteogenic differentiation by alkaline phosphatase activity and Alizarin Red staining. Results showed that TGF-beta1 added to fibrin gels was gradually released from the gels and increased with the amount of TGF-beta1 initially seeded, with a total of approximately 50% of the initial amount released by day 10 (with gels containing 25 mg/mL of FC and 2 IU/mL of thrombin). The release was lower with increasing FC concentrations, suggesting a binding affinity of TGF-beta1 with the FC component. Varying the thrombin concentration had a lesser effect. HMSC monolayers cultured with medium supernatants collected from gels at day 3 and containing released TGF-beta1 showed a change in morphology (squared to polygonal), lower cell proliferation, positive Alcian Blue staining but low levels of osteogenic differentiation markers. These results demonstrated that released TGF-beta1 was still bioactive and tended to induce mainly chondrogenic differentiation of the HMSC. Overall, the present study demonstrated that fibrin gels could be used as a carrier matrix for controlled release of bioactive TGF-beta1 by adjusting the concentrations of FC and thrombin in the gels.     

Effect of transforming growth factor beta 1 on neonatal rat latent transforming growth factor beta binding protein 2 in cardiomyocytes

目的 探讨转化生长因子β1 (TGF-β1)在诱导心肌细胞表达转化生长因子结合蛋白2(LTBP2)中的作用及信号传导通路.方法 培养乳鼠心肌细胞;实时定量聚合酶链式反应、蛋白质印迹和免疫细胞化学方法检测不同时间和不同浓度的TGF-β1对大鼠乳鼠心肌细胞LTBP2基因及蛋白表达的影响;用TGF-β1相关信号通路阻断剂探讨TGF-β1调节LTBP2表达改变的信号传导机制.结果 LTBP2基因表达随着TGF-β1浓度增加(0、2、5及10 μg/L)而明显升高,在5μg/L时刺激最强(P＜0.05);5μg/L的TGF-β1刺激下心肌细胞内LTBP2基因和蛋白表达的升高呈时间依赖性,均在12 h最高,24 h开始呈下降趋势(P＜0.05或P＜0.01);免疫细胞化学结果显示TGF-β1明显升高LTBP2的表达.信号传导通路研究显示TGF-β1在心肌细胞内主要通过ERK信号通路和PI3K信号通路诱导LTBP2的表达.结论TGF-β1在乳鼠心肌细胞内通过ERK信号通路和PI3K信号通路上调LTBP2的表达.     

转化生长因子β1对乳鼠心肌细胞转化生长因子结合蛋白2表达的影响

 目的：探讨转化生长因子β1（TGF-β1）在诱导心肌细胞表达转化生长因子结合蛋白2（LTBP2）中的作用及信号传导通路。 方法：培养乳鼠心肌细胞;实时定量聚合酶链式反应（Real-time PCR）、蛋白质印迹和免疫细胞化学方法检测不同时间和不同浓度的TGF-β1对大鼠乳鼠心肌细胞LTBP2基因及蛋白表达的影响;用TGF-β1相关信号通路阻断剂探讨TGF-β1调节LTBP2表达改变的信号传导机制。 结果：LTBP2基因表达随着TGF-β1浓度增加（0、2、5、10 ng/mL）而明显升高,在5 ng/mL时刺激最强（P < 0.05）;5 ng/mL的TGF-β1刺激下心肌细胞内LTBP2基因和蛋白表达的升高呈时间依赖性,均在12 h最高,24 h开始呈下降趋势（P < 0.05或P<0.01）;免疫细胞化学结果显示TGF-β1明显升高LTBP2的表达。信号传导通路研究显示TGF-β1在心肌细胞内主要通过ERK信号通路和PI3K信号通路诱导LTBP2的表达。 结论：TGF-β1在乳鼠心肌细胞内通过ERK信号通路和PI3K信号通路上调LTBP2的表达。     

Effect of experimental parameters on the in vitro release kinetics of transforming growth factor beta1 from coral particles.

Coral bone graft substitutes have been supplemented in the past with growth factors to further enhance bone regeneration in defects. Little is known, however, on the dynamics of protein release from coral. Coral particles were studied for their ability to release transforming growth factor beta 1 (TGF-beta1) in vitro, under different adsorption conditions. Adsorption of TGF-beta1 (0.05 microg/mL) on coral particles (<80 microm or 300-450 microm) after 24 h of incubation was high, regardless of conditions. TGF-beta1 release kinetics in an artificial bone fluid followed a specific profile: an initial 1-h protein burst, followed by a decreasing release during the next 24 h at which time the release increased again to reach a constant rate until the end of the 2-week study. The protein release rate appeared mainly to depend upon the diffusion of TGF-beta1. TGF-beta1 release from coral particles was enhanced in the presence of bovine serum albumin (BSA) compared to the release in the presence of gelatin, and was dependent on the pH of adsorption. The highest total TGF-beta1 release was obtained when adsorption occurred with BSA at pH 7.4 (82 +/- 3%), while the lowest release was observed when adsorption was done in the presence of gelatin at pH 11 (38 +/- 1%). TGF-beta1 release was also found to vary with particle size, higher release being obtained with the smaller particles. These results suggest that coral particles could be used as a delivery system for growth factors, and that the release rate may be modulated through modification of the adsorption conditions and coral particle size.     

Tailored delivery of active keratinocyte growth factor from biodegradable polymer formulations

We report the results of a high throughput screening campaign that is aimed to develop a biodegradable polymer-based formulation to deliver active keratinocyte growth factor (KGF) and provide a means to tune the KGF delivery rate. A statistical design strategy was used to prepare and screen a series of polymer blends that were composed of poly(lactic acid) (PLA), poly(glycolic acid) (PGA), and the surfactant sodium bis(ethylhexyl)sulfosuccinate (Aerosol-OT, AOT). Chloroform was the solvent. Our high throughput screening method used a two-tiered assessment strategy. At Level 1, we identified "lead" KFG-loaded formulations that exhibited KGF emission spectra that were the most similar to the native KGF spectrum recorded in buffer. At Level 2, we used steady-state emission and a homogeneous polarization immunoassay strategy to determine the concentration of total and active KGF, respectively, liberated from the lead formulations during biodegradation. After preparing and screening 2500 formulations, we identified several viable, lead formulations. An analysis of the data showed that the combination of PLA, PGA, and AOT were important to yield a high fraction of active KGF upon release from the formulation; no combination of any two together produced an effect as good as the ternary formulation. The optimum formulations that yielded the highest fraction of active KGF upon release had the following general features: PLA/PGA (w/w) near unity, AOT loading of 100-200 mM, water/AOT mole ratio of 10-20, and a pH between 6 and 8. PLA alone cast from chloroform delivered KGF, but that KGF did not bind to anti-KGF antibodies (i.e., it was inactive). We can tune the KGF release kinetics by more than two orders of magnitude while maintaining the KGF activity upon liberation from the formulation by adjusting the PLA molecular weight.     

转化生长因子β1在兔房水中的浓度变化

背景：转化生长因子β1可参与角膜损伤后的修复。 目的：观察转化生长因子β1滴眼液滴眼后房水中的浓度变化规律。 方法：将新西兰大白兔随机分为5组,分别给予PBS和质量浓度为0.5,1.0,2.0,4.0 mg/L的转化生长因子β1滴眼液滴右眼。 结果与结论：通过裂隙灯观察兔角膜和结膜结构,各组兔眼均无结膜分泌物、球结膜充血、角膜水肿增厚、角膜后沉着物、前房炎性反应及晶状体混浊改变。ELISA检测结果显示,与PBS组比较,质量浓度2.0和4.0 mg/L转化生长因子β1滴眼液能有效提高兔眼房水中转化生长因子β1的质量浓度(P < 0.01),角膜穿透性良好,在房水中可以达到有效的治疗浓度。     

Retention of transforming growth factor beta1 using functionalized dextran-based hydrogels

Functionalized dextrans (FD) are anionic water-soluble polymers bearing carboxylate, benzylamide and sulfate groups, which exhibit binding capacity to transforming growth factor-beta1 (TGF-beta1). In this paper, we have investigated the ability of dextran-based hydrogels containing FD, to bind and release recombinant human TGF-beta1. Hydrogels were prepared by chemical crosslink native dextran and FD with sodium trimetaphosphate in 1m NaOH at 50 degrees C. A wide range of hydrogels were prepared as particles ranging of 1-1.6mm of diameter and characterized with various amounts of FD and with different crosslinker feeding ratios (CFR). Dried particles were soaked with recombinant human transforming growth factor-beta1 (rhTGF-beta1) to determine their capacity to deliver the growth factor. Results indicated that the in vitro kinetics releases of rhTGF-beta1 were related to FD and CFR. Retention capacity of rhTGF-beta1 increases with an increase of negative charges of the matrices brought by both phosphate linkages and FD as demonstrated by an additional release of growth factor in high ionic strength solution. Highly crosslinked hydrogels that contained the highest amount of FD (18% (w/w)) retained up to 88% of rhTGF-beta1. Bioactivity of released growth factor was confirmed in a cell assay. These functionalized hydrogels may have important uses for the stabilization and the protection of rhTGF-beta1 as entrapment systems and could be applied to other proteins of clinical interest.     

Controlled release of nerve growth factor from fibrin gel

Nerve growth factor (NGF) is known to promote the axonal regeneration in injured nerve system. Delivery of NGF for a long period in a controlled manner may enhance the regeneration efficacy. In this study, we investigated whether NGF can be released from fibrin gel for a long period in a controlled manner. We also investigated whether sustained delivery of NGF using fibrin gel can enhance the efficacy of NGF in vitro. The addition of heparin to fibrin gel decreased the rate of NGF release from the fibrin gel. As the concentrations of thrombin and fibrinogen in fibrin gel increased, the NGF release rate decreased significantly, and the initial release burst decreased. NGF was released for up to 14 days in vitro. The bioactivity of NGF released from fibrin gel was assessed by morphological changes of pheochromocytoma (PC12) cells cultured in the presence of NGF-containing fibrin gel. NGF released from fibrin gel exhibited significantly higher degrees of PC12 cell viability and differentiation than NGF added in a free form daily into the culture medium. This study demonstrates that fibrin gel can release NGF in a sustained, controlled manner and in a bioactive form.     

Intra-articular controlled release of anti-inflammatory siRNA with biodegradable polymer microparticles ameliorates temporomandibular joint inflammation

We investigated the in vivo therapeutic efficacy of an intra-articular controlled release system consisting of biodegradable poly(dl-lactic-co-glycolic acid) (PLGA) microparticles (MPs) encapsulating anti-inflammatory small interfering RNA (siRNA), together with branched poly(ethylenimine) (PEI) as a transfecting agent, in a rat model of painful temporomandibular joint (TMJ) inflammation. The in vivo effects of PLGA MP dose and siRNA-PEI polyplex delivery were examined via non-invasive meal pattern analysis and by quantifying the protein level of the siRNA target as well as of several downstream inflammatory cytokines. Controlled release of siRNA-PEI from PLGA MPs significantly reduced inflammation-induced changes in meal patterns compared to untreated rats with inflamed TMJs. These changes correlated to decreases in tissue-level protein expression of the siRNA target to 20-50% of the amount present in the corresponding control groups. Similar reductions were also observed in the expression of downstream inflammatory cytokines, e.g. interleukin-6, whose tissue levels in the siRNA-PEI PLGA MP groups were 50% of the values for the corresponding controls. This intra-articular sustained release system has significant implications for the treatment of severe TMJ pain, and also has the potential to be readily adapted and applied to mitigate painful, chronic inflammation in a variety of conditions.     

Controlled release of bioactive TGF-beta 1 from microspheres embedded within biodegradable hydrogels

Transforming growth factor-beta1 (TGF-beta1) is of great relevance to cartilage development and regeneration. A delivery system for controlled release of growth factors such as TGF-beta1 may be therapeutic for cartilage repair. We have encapsulated TGF-beta1 into poly(DL-lactide-co-glycolide) (PLGA) microspheres, and subsequently incorporated the microspheres into biodegradable hydrogels. The hydrogels are poly(ethylene glycol) based, and the degradation rate of the hydrogels is controlled by the non-toxic cross-linking reagent, genipin. Release kinetics of TGF-beta1 were assessed using ELISA and the bioactivity of the released TGF-beta1 was evaluated using a mink lung cell growth inhibition assay. The controlled release of TGF-beta1 encapsulated within microspheres embedded in scaffolds is better controlled when compared to delivery from microspheres alone. ELISA results indicated that TGF-beta1 was released over 21 days from the delivery system, and the burst release was decreased when the microspheres were embedded in the hydrogels. The concentration of TGF-beta1 released from the gels can be controlled by both the mass of microspheres embedded in the gel, and by the concentration of genipin. Additionally, the scaffold permits containment and conformation of the spheres to the defect shape. Based on these in vitro observations, we predict that we can develop a microsphere-loaded hydrogel for controlled release of TGF-beta1 to a cartilage wound site.     

Inhibition of myofibroblast apoptosis by transforming growth factor beta(1)

Fibroblast differentiation to the myofibroblast phenotype is associated with alpha-smooth-muscle actin (alpha-SMA) expression and regulated by cytokines. Among these, transforming growth factor (TGF)-beta(1) and interleukin (IL)-1beta can stimulate and inhibit myofibroblast differentiation, respectively. IL-1beta inhibits alpha-SMA expression by inducing apoptosis selectively in myofibroblasts via induction of nitric oxide synthase (inducible nitric oxide synthase [iNOS]). Because TGF-beta is known to inhibit iNOS expression, this study was undertaken to see if this cytokine can protect against IL-1beta-induced myofibroblast apoptosis. Rat lung fibroblasts were treated with IL-1beta and/or TGF-beta(1) and examined for expression of alpha-SMA, iNOS, and the apoptotic regulatory proteins bax and bcl-2. The results show that TGF-beta(1) caused a virtually complete suppression of IL-1beta-induced iNOS expression while preventing the decline in alpha-SMA expression or the myofibroblast subpopulation. TGF-beta(1) treatment also completely suppressed the IL-1beta-induced apoptosis in myofibroblasts. IL-1beta-induced apoptosis was associated with a significant decline in expression of the antiapoptotic protein bcl-2, which was prevented by concomitant TGF-beta(1) treatment. The level of the proapoptotic protein bax, however, was not significantly altered by either cytokine. These data suggest that TGF-beta(1) inhibits IL-1beta-induced apoptosis in myofibroblasts by at least two mechanisms, namely, the suppression of iNOS expression and the prevention of a decline in bcl-2 expression. Thus, TGF-beta(1) may be additionally important in fibrosis by virtue of this novel ability to promote myofibroblast survival by preventing the myofibroblast from undergoing apoptosis.     

TGF-β1及TGF βR Ⅱ mRNA在子痫前期患者胎盘组织中的表达及意义

目的检测胎盘组织中TGF-β1(transform ing growth factor-beta1,TGF-β1)及其受体TGFβRⅡ(TGF-beta receptorⅡ)的表达,探求TGF-β1在子痫前期发病中的作用。方法用半定量逆转录聚合酶链反应(RT-PCR)技术对10例正常妊娠组和26例子痫前期组(包括12例轻度和14例重度)胎盘组织中TGF-β1、TGFβRⅡmRNA的表达水平进行检测,并通过紫外凝胶图像分析进行定量分析。结果重度子痫前期组TGF-β1和TGFβRⅡmRNA的表达量均升高,与轻度子痫前期组及正常妊娠组相比有明显意义(P<0.05)。结论TGF-β1、TGFβRⅡ在转录水平就已经上调,它们的异常表达它们可能与子痫前期的发病有着重大的关系。     

Expression of transforming growth factor beta 1 (TGF beta 1) and angiogenesis in broncho-pulmonary carcinoids

TGF beta 1 commonly produced by normal and neoplastic human cells, has capacity to regulate new blood vessel formation, to establish and maintain the vessel wall integrity; was found to have some significance in the lung cancer prognosis. Tumour angiogenesis is an important factor for tumour growth and metastasis. The purpose of this study was to find, if the immunoexpression of TGF beta 1 has any significance in determination of the histologic subtypes of carcinoids?; to find, if TGF beta 1 has any role and relation to carcinoids angiogenesis?; and to explore TGF beta 1 expression and angiogenesis with respect to metastatic potential of carcinoids. The study was performed on 48 resected broncho-pulmonary carcinoids: 35 typical (TC) and 13 atypical (AC), classified according to the WHO. Semiquantitative analysis for TGF beta 1 was performed. Sections stained using monoclonal antibody against TGF beta 1 were scored in scale from 0 to 4, according to the percentage of positively stained cells (pc) plus percentage of positively stained stroma (ps). The microvessels stained with CD34 monoclonal antibody, were counted in 0.75 mm2 field (microvessel density--MD), using the computerised image analysis system SAMBA 2005 (the morphometric software). The histologic subtype of carcinoids was related to age of the pts (AC occurred in older pts than TC, p = 0.027), to the tumour size (AC were larger than TC: respectively--3.25 cm and 2.4 cm, p = 0.009). Lymph node metastases were significantly more frequent in AC than in TC (38% vs 13%, p = 0.025). 85% carcinoids showed TGF beta 1 expression with various intensity, mainly in the stroma. There was no significant correlation between TGF beta 1 expression and tumour size, the histologic subtype nor the lymph node metastases. The angiogenesis expressed as MD, was not related to histology, nor to the presence of lymph node metastases. There was no correlation between TGF beta 1 expression and angiogenesis. Shown in our study, lack of relation between TGF beta 1 expression and angiogenesis, could support some of the published data indicating indirect action of TGF beta 1 on the angiogenesis. The rich vascularity found in carcinoids morphology could result from TGF beta 1, commonly expressed by the tumoural stroma. The angiogenesis nor TGF beta 1 expression do not determinate the carcinoids histology.     

Endothelial cells synthesize basic fibroblast growth factor and transforming growth factor beta

Endothelial cells, including human umbilical vein endothelial cells (HUVEC), bovine aortic endothelial cells (BAEC), and bovine capillary endothelial cells (BCEC) in culture synthesize basic fibroblast growth factor (bFGF) and transforming growth factor type beta (TGF-beta). Basic FGF was cell-associated and synthesis was demonstrated by (i) the presence of bFGF mRNA species, (ii) binding to heparin-Sepharose and elution at 1.5 M NaCl, (iii) cross-reactivity with anti-bFGF antibodies when analyzed by electrophoretic blotting, and (iv) biological activity. Basic FGF was found in cell lysates at 2.3 ng/10(6) cells in HUVEC, 2.0 ng/10(6) cells in BCEC, and 13 ng/10(6) cells in BAEC. TGF-beta was secreted into media, and synthesis was demonstrated by (i) presence of TGF-beta mRNA species, (ii) cross-reactivity with anti-TGF-beta antibodies when analyzed by immunoprecipitation, (iii) competitive binding with authentic human platelet-derived TGF-beta that was blocked by TGF-beta specific blocking antibodies, and (iv) inhibition of [3H]TdR incorporation in CCl-64 cells. TGF-beta was secreted in an inactive form and required acid activation for detection. HUVEC synthesized 2.0 ng TGF-beta/10(6) cells per 12 hr; BCEC, 3.5 ng; and BAEC, 3.5 ng. HUVEC proliferation was not affected by treatment with exogenous TGF-beta, while BCEC proliferation was decreased by treatment with TGF-beta. Vascular endothelium is thus a source for these two potent multifunctional regulatory molecules, both of which may affect the growth of endothelium and neighboring fibroblasts, smooth muscle cells and white blood cells. The activation or release of these factors by endothelium may be a precipitating event in important cellular processes such as wound healing, organogenesis, and angiogenesis.     

Release of bioactive transforming growth factor beta(3) from microtextured polymer surfaces in vitro and in vivo

Transforming growth factor beta(3) (TGF-beta(3)) has been under investigation with the objective of improving wound healing. Yet, little experimental knowledge exists about applications of TGF-beta(3) in implantology and tissue engineering. The aims of this study were to determine the release kinetics and bioactivity of TGF-beta(3) released from microtextured silicone and poly-L-lactic acid (PLA) surfaces in vitro and in vivo. We loaded surfaces with 100 ng of TGF-beta(3). An in vitro assay showed that TGF-beta(3) was released in a burstlike manner. Released TGF-beta(3) was capable of inhibiting the proliferation of mink lung epithelial cells, indicating that released TGF-beta(3) had remained at least partly active. Subsequently, an in vivo experiment (1 h-3 days) was performed with implants loaded with TGF-beta(3). In cryosections, TGF-beta(3) activity was assessed by an in situ bioassay. We found that active TGF-beta(3) was released for up to 24 h. Furthermore, released TGF-beta(3) could be detected up to 320 microm from the implant. On the basis of these observations, we conclude that TGF-beta(3) loaded onto microtextured polymer membranes remains functional when released in vitro and in vivo and, therefore, may represent an alternative for introducing a growth factor into a wound to achieve long-term and long-range biological effects.     

Regulation and regulatory activities of transforming growth factor beta

Transforming growth factor beta (TGF beta) is unique among growth factors in its potent and widespread actions. Almost every cell in the body has been shown to make some form of TGF beta, and almost every cell has receptors for TGF beta. Therefore, it becomes apparent that this growth factor must be tightly regulated to prevent disease. The mechanisms of regulation of TGF beta are extensive and complex. One set of mechanisms centers around the fact that TGF beta is produced in a latent form that must be activated to produce biologically active TGF beta. These mechanisms include the latency of the molecule, the production of various latent forms, its targeting to cells for activation or to matrix for storage, and the means of activation of the latent forms. The TGF beta isoforms and the types, affinity, and signaling functions of its receptors also add complexity to the regulation of the effects of TGF beta. Active TGF beta regulates numerous processes in the body. TGF beta has three major biological effects: growth inhibition, stimulation of extracellular matrix formation, and immunosuppression. The means by which TGF beta regulates the expression of the numerous genes on which it has effects are complex and more information is needed. The means by which TGF beta regulates gene expression and the means by which the actions of TGF beta are regulated are addressed in this review.