Efeitos da nanopartícula de ácido poli lático-co-glicólico (PLGA) associada ao cloridrato de metformina na doença periodontal em ratos diabéticos / Effects of polylactic-co-glycolic acid (PLGA) nanoparticle associated with metformin hydrochloride on periodontal disease in diabetic rats

Existe uma associação entre diabetes e a periodontite, e a Metformina (MET) além de controlar os níveis glicêmicos, tem apresentado efeitos antiinflamatórios e na diminuição da perda óssea periodontal. Ao se veicular a MET a um sistema de nanopartículas pode-se apresentar a vantagem de aumento da eficácia terapêutica. Objetivos: esse estudo consistiu na avaliação dos efeitos antiinflamatórios, perda óssea e disponibilidade in vitro/in vivo de uma nanopartícula de ácido poli lático-co-glicólico (PLGA) associada à MET em um modelo de periodontite induzida por ligadura. Materiais e métodos: o PLGA carreado com diferentes doses da MET foi caracterizado pelo seu diâmetro médio, tamanho da partícula, índice de polidispensão e eficiência de aprisionamento. Foram utilizados ratos machos da linhagem Wistar, divididos aleatoriamente, em grupos controles e experimentais com diferentes doses de MET associadas ou não ao PLGA, os quais receberam diferentes tratamentos. Amostras de maxilas e tecidos gengivais foram utilizadas para avaliação de perda óssea e inflamação, por meio da microtomografia computadorizada, histopatológico, imunohistoquímica, análise de citocinas inflamatórias e expressão gênica de proteínas por RT-PCR quantitativo. Para o ensaio de liberação in vitro, utilizou-se o dispositivo de células de difusão vertical de Franz estáticas. Para a disponibilidade in vivo, as amostras de sangue foram coletadas em diferentes intervalos de tempo e analisadas por cromatografia líquida de alta eficiência acoplado a espectrometria de massas (HPLC-MS/MS). Resultados: o diâmetro médio das nanopartículas de PLGA carreadas com MET estava em um intervalo de 457,1 ± 48,9 nm (p <0,05) com um índice de polidispersidade de 0,285 (p <0,05), potencial Z de 8,16 ± 1,1 mV (p <0,01) e eficiência de aprisionamento (EE) de 66,7 ± 3,73. O tratamento com a MET 10 mg / kg + PLGA mostrou uma baixa concentração de células inflamatórias, fraca imunomarcação para RANKL, Catepsina K, OPG e osteocalcina. Diminuição dos níveis de IL-1ß e TNF-α (p <0,05), aumento da expressão gênica do AMPK (p <0,05) e diminuição do NF-κB p65, HMGB1 e TAK-1 (p <0,05). O 10 mg/kg MET + PLGA foi liberado no ensaio in vitro sugerindo um modelo cinético de difusão parabólica com um perfil de liberação que atinge 50% de seu conteúdo em 2h e permanece em liberação constante em torno de 60% até o final de 6h. O ensaio in vivo mostrou o volume aparente de distribuição Vz/F (10 mg/kg MET + PLGA, 46,31 mL/kg vs. 100 mg/kg MET + PLGA, 28,8 mL/kg) e o tempo médio de residência MRTinf (PLGA + MET 10 mg /kg, 37,66h vs. MET 100 mg/kg, 3,34h). Conclusão: o PLGA carreado com MET diminuiu a inflamação e a perda óssea na periodontite em ratos diabéticos. O 10 mg/kg MET + PLGA teve uma taxa de eliminação mais lenta em comparação com o MET 100 mg/kg. A formulação modifica os parâmetros farmacocinéticos, como volume de distribuição aparente e tempo médio de residência (AU).

There is an association between diabetes and periodontitis, and Metformin (MET) in addition to controlling glycemic levels, has shown anti-inflammatory effects and decreased periodontal bone loss. By transferring MET to a nanoparticle system, the advantage of increasing therapeutic efficacy can be presented. Objectives: this study consisted of evaluating the antiinflammatory effects, bone loss and in vitro/in vivo availability of a polylactic-co-glycolic acid (PLGA) nanoparticle associated with MET in a ligature-induced periodontitis model. Materials and methods: PLGA loaded with different doses of MET was characterized by its mean diameter, particle size, polydispension index and entrapment efficiency. Male Wistar rats were used, randomly divided into control and experimental groups with different doses of MET associated or not with PLGA, which received different treatments. Samples of jaws and gingival tissues were used to assess bone loss and inflammation, using computed microtomography, histopathology, immunohistochemistry, analysis of inflammatory cytokines and gene expression of proteins by quantitative RT-PCR. For the in vitro release assay, the static Franz vertical diffusion cell device was used. For in vivo availability, blood samples were collected at different time intervals and analyzed by high performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS). Results: the mean diameter of MET-loaded PLGA nanoparticles was in the range of 457.1 ± 48.9 nm (p <0.05) with a polydispersity index of 0.285 (p <0.05), Z potential of 8.16 ± 1.1 mV (p <0.01) and trapping efficiency (EE) of 66.7 ± 3.73. Treatment with MET 10 mg/kg + PLGA showed a low concentration of inflammatory cells, weak immunostaining for RANKL, Cathepsin K, OPG and osteocalcin. Decreased IL-1ß and TNF-α levels (p <0.05), increased AMPK gene expression (p <0.05) and decreased NF-κB p65, HMGB1 and TAK-1 (p <0. 05). The 10 mg/kg MET + PLGA was released in the in vitro assay suggesting a kinetic model of parabolic diffusion with a release profile that reaches 50% of its content in 2h and remains in constant release around 60% until the end of 6h . The in vivo assay showed the apparent volume of distribution Vz/F (10 mg/kg MET + PLGA, 46.31 mL/kg vs. 100 mg/kg MET + PLGA, 28.8 mL/kg) and the mean MRTinf residency (PLGA + MET 10 mg/kg, 37.66h vs. MET 100 mg/kg, 3.34h). Conclusion: MET-loaded PLGA decreased inflammation and bone loss in periodontitis in diabetic rats. 10 mg/kg MET + PLGA had a slower rate of elimination compared to 100 mg/kg MET. The formulation modifies pharmacokinetic parameters such as apparent volume of distribution and mean residence time (AU).

Efecto angiogénico comparado del celecoxib microencapsulado en PLGA v/s no encapsulado en un ensayo in vivo de angiogénesis / Comparative angiogenic effect of microencapsulated celecoxib in PLGA v/s non-encapsulated in an in vivo angiogenesis assay

RESUMEN: La angiogénesis es el proceso de formación de vasos sanguíneos a partir de otros formados previamente. Existen varios factores que están involucrados en el proceso, así como agentes capaces de modular distintas etapas de esta. Si bien, se ha observado que Celecoxib es capaz de inhibir la angiogénesis en distintos modelos, aún no se ha observado la potencial capacidad antiangiogénica de este agente cuando es microencapsulado en PLGA. Se incubaron huevos fertilizados y a las 48 horas se dividieron en 4 grupos para ser instilados con PBS (control), PLGA, Celecoxib 1000 ppm o Celecoxib 1000 ppm + PLGA. Se realizó un conteo de los vasos sanguíneos a las 48, 72 y 96 horas post aplicación de la solución a estudiar. Los resultados muestran que tanto Celecoxib como Celecoxib+PLGA reducen los vasos sanguíneos, manteniendo el mismo efecto a las 48, 72 y 96 horas y no existen diferencias significativas entre los dos tratamientos. Esto podría ser explicado por la concentración de Celecoxib usada o el margen de tiempo analizado, pudiendo encontrarse diferencias posteriores a este rango de tiempo o con concentraciones distintas.

SUMMARY: Angiogenesis is the process of blood vessel formation from previously formed ones. There are several factors involved in the process, as well as agents capable of modulating different stages of it. Although, it has been observed that Celecoxib is capable of inhibiting angiogenesis in different models, the potential antiangiogenic capacity of this agent has not yet been observed when it is microencapsulated in PLGA. Fertilized eggs were incubated and at 48 hours they were divided into 4 groups to be instilled with PBS (control), PLGA, Celecoxib 1000ppm or Celecoxib 1000 ppm + PLGA. A blood vessel count was performed at 48, 72 and 96 hours after application of the solution to be studied. The results show that both Celecoxib and Celecoxib + PLGA reduce blood vessels, maintaining the same effect at 48, 72 and 96 hours and there are no significant differences between the two treatments. This could be explained by the concentration of Celecoxib used or the time frame analyzed, being able to find differences after this time range or with different concentrations.

Comparison of two different biomaterials in the bone regeneration (15, 30 and 60 days) of critical defects in rats

ABSTRACT Purpose To evaluate and compare two types of different scaffolds in critical bone defects in rats. Methods Seventy male Wistar rats (280 ± 20 grams) divided into three groups: control group (CG), untreated animals; biomaterial group 1 (BG1), animals that received the scaffold implanted hydroxyapatite (HA)/poly(lactic-co-glycolic) acid (PLGA); and biomaterial group 2 (BG2), animals that received the scaffolds HA/PLGA/Bleed. The critical bone defect was induced in the medial region of the skull calotte with the aid of an 8-mm-diameter trephine drill. The biomaterial was implanted in the form of 1.5 mm thick scaffolds, and samples were collected after 15, 30 and 60 days. Non-parametric Mann-Whitney test was used, with the significance level of 5% (p ≤ 0.05). Results Histology revealed morphological and structural differences of the neoformed tissue between the experimental groups. Collagen-1 (Col-1) findings are consistent with the histological ones, in which BG2 presented the highest amount of fibers in its tissue matrix in all evaluated periods. In contrast, the results of receptor activator of nuclear factor kappa-Β ligand (Rank-L) immunoexpression were higher in BG2 in the periods of 30 and 60 days, indicating an increase of the degradation of the biomaterial and the remodeling activity of the bone. Conclusions The properties of the HA/PLGA/Bleed scaffold were superior when compared to the scaffold composed only by HA/PLGA.

VPA/PLGA microfibers produced by coaxial electrospinning for the treatment of central nervous system injury

The central nervous system shows limited regenerative capacity after injury. Spinal cord injury (SCI) is a devastating traumatic injury resulting in loss of sensory, motor, and autonomic function distal from the level of injury. An appropriate combination of biomaterials and bioactive substances is currently thought to be a promising approach to treat this condition. Systemic administration of valproic acid (VPA) has been previously shown to promote functional recovery in animal models of SCI. In this study, VPA was encapsulated in poly(lactic-co-glycolic acid) (PLGA) microfibers by the coaxial electrospinning technique. Fibers showed continuous and cylindrical morphology, randomly oriented fibers, and compatible morphological and mechanical characteristics for application in SCI. Drug-release analysis indicated a rapid release of VPA during the first day of the in vitro test. The coaxial fibers containing VPA supported adhesion, viability, and proliferation of PC12 cells. In addition, the VPA/PLGA microfibers induced the reduction of PC12 cell viability, as has already been described in the literature. The biomaterials were implanted in rats after SCI. The groups that received the implants did not show increased functional recovery or tissue regeneration compared to the control. These results indicated the cytocompatibility of the VPA/PLGA core-shell microfibers and that it may be a promising approach to treat SCI when combined with other strategies.

Avaliação da combinação de poli (ácido láctico-co-glicólico) e poli-isopreno (Cellprene®): estudo histológico em ratos / Evaluation of the combination of poly (Lactic-Co-Glycolic Acid) and polyisoprene (Cellprene®) materials: histological study in rats

Resumo Introdução A quantidade e qualidade óssea na implantodontia é um fator de alta relevância quando se tem por objetivo instalar implantes e reabilitar pacientes. No entanto, essa disponibilidade é comprometida na maioria dos casos, havendo a necessidade da busca de novos biomateriais, membranas e substâncias para uma regeneração mais favorável. Objetivo: O objetivo deste estudo foi avaliar a resposta da neoformação óssea em defeitos críticos em calvárias de ratos utilizando scaffolds de fibras de blenda polimérica a partir de poli (ácido láctico-co-glicólico) e poli-isopreno (Cellprene®). O projeto foi aprovado pelo Comitê de Ética em Experimentação Animal. Material e método Neste estudo, foram utilizados 36 ratos (Rattus Norvegicus), variação albinus, Holtzman, adultos. Os animais foram submetidos à tricotomia na região da calota craniana e à confecção de defeitos ósseos circulares bilaterais com 5 mm de diâmetro. Os animais foram divididos em três grupos: GC - defeito sem colocação de biomaterial; GCol - scaffolds de colágeno (Bio-Gide, da empresa Geistlich Pharma Ag - Biomaterials); GPoli - scaffolds de fibras de blenda polimérica a partir de poli (ácido láctico-co-glicólico - Cellprene®). Cada grupo foi avaliado em quatro períodos experimentais (7, 15, 30 e 60 dias). Após esses períodos, os animais foram sacrificados, e as peças passaram por tramitação laboratorial de rotina e inclusão em parafina. Foram obtidos cortes semisseriados e corados pela técnica de hematoxilina e eosina para análise histométrica e histológica. Foi executada análise histométrica para avaliar a composição do tecido ósseo reparado (% osso). Os dados obtidos foram analisados estatisticamente com nível de significância de 95%. Resultado Foi verificado que o GCol apresentou maior preenchimento do defeito nos períodos de 30 e 60 dias em comparação aos GC e GPoli. Conclusão Os scaffolds de fibras de blenda polimérica a partir de poli (ácido láctico-co-glicólico) e poli-isopreno (Cellprene®) não apresentaram vantagens quando utilizados em defeitos críticos.

Abstract Introduction The bone quantity and quality in implant dentistry is a highly relevant factor when it aims the use of implants and rehabilitation in patients. However, this availability is compromised in most cases, with the need to research new biomaterials, membranes and substances for more favorable regeneration. Objective: The aim of this study was to evaluate the response of bone neoformation in critical defects in rat calvaries using polymeric blend fiber scaffolds from Poly (Lactic-Co-Glycolic Acid) and Polyisoprene (Cellprene®). The project was approved by the Animal Experimentation Ethics Committee. Material and method In this study 36 rats (Rattus Norvegicus), variation albinus, Holtzman, adults were used. The animals had trichotomy in the region of the skull and the confection of bilateral circular bone defects with a diameter of 5 mm. The animals were divided into 3 groups: Group GC - defect without biomaterial placement, Group GCol - collagen scaffolds (Bio-Gide, from Geistlich Pharma Ag - Biomaterials), Group GPoli - polymeric blend fiber scaffolds from Poly (Lactic-Co-Glycolic Acid)-Polyisoprene. Each group was evaluated in 4 experimental periods (7, 15, 30 and 60 days). After these periods the animals were sacrificed and the pieces underwent routine laboratory procedures and paraffin embedding. Semi-serial sections were obtained and stained by hematoxylin and eosin technique for histometric and histological analysis. Histometric analysis was performed to evaluate the composition of repaired bone tissue (% Bone). The data obtained were statistically analyzed with a significance level of 95%. Result It was found that the GCol group presented greater defect filling in the 30 and 60 days periods compared to the GC and GPoli groups. Conclusion Polymer blend fiber scaffolds from Poly (Lactic-Co-Glycolic Acid) and Polyisoprene (Cellprene®) did not have advantages when used in critical defects.

In vitro and in vivo biocompatibility of reoss® in powder and putty configurations

Article This study evaluated comparatively two configurations (powder and putty) of a composite biomaterial based on PLGA (Poly(lactide-co-glycolide)/nanoescale hydroxyapatite (ReOss®, Intra-Lock International) through microscopic morphology, in vitro cytotoxicity, biocompatibility and in vivo response as a bone substitute. SEM and EDS characterized the biomaterials before/after grafting. Cytocompatibility was assessed with murine pre-osteoblasts. Osteoconductivity and biocompatibility were evaluated in White New Zealand rabbits. Both configurations were implanted in the calvaria of eighteen animals in non-critical size defects, with blood clot as the control group. After 30, 60 and 90 days, the animals were euthanized and the fragments containing the biomaterials and controls were harvested. Bone blocks were embedded in paraffin (n=15) aiming at histological and histomorphometric analysis, and in resin (n=3) aiming at SEM and EDS. Before implantation, the putty configuration showed both a porous and a fibrous morphological phase. Powder revealed porous particles with variable granulometry. EDS showed calcium, carbon, and oxygen in putty configuration, while powder also showed phosphorus. After implantation EDS revealed calcium, carbon, and oxygen in both configurations. The materials were considered cytotoxic by the XTT test. Histological analysis showed new bone formation and no inflammatory reaction at implant sites. However, the histomorphometric analysis indicated that the amount of newly formed bone was not statistically different between experimental groups. Although both materials presented in vitro cytotoxicity, they were biocompatible and osteoconductive. The configuration of ReOss® affected morphological characteristics and the in vitro cytocompatibility but did not impact on the in vivo biological response, as measured by the present model.

Resumo Este estudo avaliou comparativamente duas configurações (pó e massa) de um biomaterial composto com base de PLGA (Poli(láctico-co-glicólico)/hidroxiapatita em nanoescala (ReOss®, Intra-Lock International) através da morfologia microscópica, citotoxicidade in vitro, biocompatibilidade e resposta in vivo como substituto ósseo. MEV e EDS caracterizaram os biomateriais antes/após o enxerto. A citocompatibilidade foi avaliada em pré-osteoblastos murinos. A osteocondutividade e a biocompatibilidade foram avaliadas em coelhos Branco da Nova Zelândia. Ambas as configurações foram implantadas na calvária de dezoito animais em defeitos não-críticos, com coágulo sanguíneo como grupo controle. Após 30, 60 e 90 dias, os animais foram eutanasiados e os fragmentos contendo os biomateriais e controles coletados. Blocos ósseos foram embebidos em parafina (n=15) destinados às análises histológica e histomorfométrica, e em resina (n=3) destinadas à MEV e EDS. Antes da implantação, a configuração massa mostrou ambas fases morfológicas porosa e fibrosa. O pó revelou partículas porosas com granulometria variável. EDS mostrou cálcio, carbono e oxigênio na configuração massa, enquanto o pó mostrou também fósforo. Após a implantação a EDS revelou cálcio, carbono e oxigênio em ambas configurações. Os materiais foram considerados citotóxicos pelo teste XTT. A análise histológica mostrou nova formação óssea e nenhuma reação inflamatória nos sítios de implante. Entretanto, a análise histomorfométrica indicou que a quantidade de osso neoformado não foi estatisticamente diferente entre os grupos experimentais. Embora ambos os materiais tenham apresentado citotoxicidade in vitro, foram biocompatíveis e osteocondutores. A configuração do ReOss® afetou as características morfológicas e a citocompatibilidade in vitro, porém não impactou a resposta biológica in vivo, como medido pelo presente modelo.

Efeito de diferentes doses de laser de baixa intensidade em células-tronco dentais cultivadas sobre arcabouços de ácido polilático / Effect of different doses of low intensity laser on dental stem cells cultured on polylactic acid scaffolds

As células-tronco mesenquimais dentais (dMSC) têm sido amplamente utilizadas na engenharia tecidual por sua capacidade de auto-renovação e potencial multilinhagem. Dentre as dMSCs, as células-tronco da polpa do dente decíduo esfoliado (SHEDs) destacam-se pela facilidade de coleta, capacidade proliferativa e tempo sobrevivência. O objetivo do estudo foi avaliar, através de experimentos in vitro, o efeito de diferentes doses do laser de baixa intensidade (LBI) na atividade biológica de SHEDs cultivadas sobre arcabouços de ácido polilático (PLA). Células previamente isoladas e caracterizadas foram cultivadas sobre filmes de PLA e foram irradiadas ou não (controle) com um laser diodo InGaAlP (660 nm, 30 mW, modo de ação contínuo) em um screening de doses (1, 4, 7.5, 15, 22.5 e 30 J/cm²). A proliferação e viabilidade celular foram analisadas nos intervalos de 24, 48 e 72 h, através dos ensaios do Alamar Blue e Live/Dead. A morfologia celular foi avaliada por MEV no intervalo de 72h. A avaliação do estresse oxidativo foi realizada através das dosagens de malondialdeído (MDA) e glutationa (GSH). Densidades de energia de 1 J/cm² e 4 J/cm² promoveram um efeito estimulador da proliferação celular nos três intervalos de tempo quando comparados ao grupo controle e aos demais grupos irradiados. Por outro lado, doses elevadas de irradiação (22.5 e 30 J/cm²) promoveram redução significativa das células. Verificou-se que a viabilidade celular foi afetada ao longo do experimento nos grupos L22.5 e L30, que apresentaram maior quantidade de células mortas no intervalo de 72h. Na análise por MEV evidenciou-se uma maior densidade celular nos grupos L1 e L4, contrapondo-se às SHEDs arranjadas mais dispersamente nos grupos L22.5 e L30. Em relação ao estresse oxidativo, nos grupos L1 e L4 houve elevação dos níveis de GSH e redução do MDA, de modo contrário, nos grupos L22.5 e L30 houve redução dos níveis de GSH e elevação do MDA. Conclui-se que doses baixas de LBI (1 e 4 J/cm²) promovem proliferação e tem efeito citoprotetor em SHEDs cultivadas sobre arcabouços de PLA, enquanto doses elevadas (22.5 e 30J/cm²) tem ação citotóxica e reduzindo a viabilidade e proliferação destas células (AU).

Dental mesenchymal stem cells (dMSCs) have been widely used in tissue engineering for their capacity for self-renewal and multi-lineage potential. Among the dMSCs, the stem cells from human exfoliated deciduous teeth (SHEDs) are highlighted for their ease of collection, proliferative capacity and survival time. The aim of the study was to evaluate, through in vitro experiments, the effect of different doses of low intensity laser (LLLI) on the biological activity of SHEDs cultured on polylactic acid (PLA) scaffolds. Pre-isolated and characterized cells were cultured on PLA films and irradiated or not (control) with an InGaAlP diode laser (660 nm, 30 mW, continuous action mode) in a dose screening (1, 4, 7.5, 15, 22.5 and 30 J/cm²). Cell proliferation and viability were analyzed at 24, 48 and 72 hr using the Alamar Blue and Live/Dead assays. Cell morphology was evaluated by SEM at 72 h. The evaluation of oxidative stress was performed through the dosages of malondialdehyde (MDA) and glutathione (GSH). Energy densities of 1 J/cm² and 4 J/cm² promoted cell proliferation in all intervals when compared to the control group and the other irradiated groups. Contrarily, high doses of irradiation (22.5 and 30 J/cm²) promoted significant negative effect on cell proliferation. It was verified that cell viability was affected throughout the experiment in groups L22.5 and L30, which presented a higher number of dead cells in the interval of 72h. The SEM analysis showed a greater cell density in L1 and L4 groups, opposing the SHEDs arranged more sparsely in L22.5 and L30 groups. Regarding to oxidative stress, in L1 and L4 groups there was elevation of GSH levels and reduction of MDA, showing a cytoprotective effect of these doses. Conversely, in groups L22.5 and L30 there was a reduction of GSH levels and elevation of MDA, corroborating with the results of the aforementioned assays. It is concluded that low doses of LLLI (1 and 4 J/cm²) promote proliferation of SHEDs on PLA scaffolds, while high doses (22.5 and 30 J/cm²) promote cytotoxic and anti-proliferative action in these cells (AU).

Hepatic toxicity caused by PLGA-microspheres containing usnic acid from the lichen C ladonia substellata (AHTI) during pregnancy in Wistar rats

ABSTRACT This study aimed to evaluate the teratogenic and hepatotoxic potential of the usnic acid encapsulated into PLGA-microspheres. In total, 12 female Wistar rats in pregnancy were randomly distributed in the control group (n= 6) that received 1.0 mL of physiological solution and treatment group (n= 6) that received 25 mg/kg of encapsulated usnic acid by oral administration. All females were euthanized at day 20 of pregnancy and their fetuses were removed and analyzed. During the pregnancy was observed a reduction in weight gain. There was no difference in serum transaminases levels analyzed as well as any difference in liver weight in both groups. The histomorphometric analysis of the liver from the treatment group revealed an increase in number of hepatocytes and a decrease in nuclear area of these cells. Moreover, no alteration was observed in cell area of hepatocytes or number of Kupffer cells. The fetuses had an increase in total number of hepatocytes and a reduction in the amount of megakaryocytes. These results show the hepatotoxic potential of usnic acid during pregnancy. However, its toxicity can be minimized by encapsulation in microspheres.

Morphometric and Histopathologic Changes in Skeletal Muscle Induced for Injectable PLGA Microparticles / Cambios Morfométricos e Histopatológicos en el Músculo Esquelético Inducidos por Microparticulas de PLGA Inyectables

The administration of microencapsulated drug in a matrix acid poly(lactic-co-glycolic acid) (PLGA) by intramuscular (IM) in humans has been approved by the FDA for various applications though it is not clear what effect they have on the morphological parameters of muscle tissue. The aim of this study was to analyze the morphological changes in the skeletal muscle tissue with their use. We used 12 adult female Sprague Dawley rats (Rattus novergicus) that were injected into their right gastrocnemius muscle belly with: sterile vehicle solution (G1, n = 4), 0.5 mg PLGA microparticle (G2, n = 4) and 0.75 mg PLGA microparticle (G3, n = 4), both dissolved in a sterile vehicle solution. At 14 days post injection the number and diameter of muscle fibers, the level of inflammation and histology appearance in terms of organization of muscle fibers, cellular distribution, tissue morphology and the presence of polymer waste were determined and the results between the groups compared. The administration of the compound in a single dose did not alter the morphometric parameters (number and diameter of muscle fibers) despite generating a mild inflammation in the tissue associated with the presence of polymeric residues, suggesting that the PLGA microparticles were well tolerated by the muscle tissue at concentrations tested (0.5 and 0.75 mg).

La administración de fármacos encapsulados en micropartículas de ácido poli-láctico/glicólico (PLGA) por vía intramuscular (IM) ha sido aprobada por FDA para su uso en seres humanos con variadas aplicaciones, no estando claro el efecto que tienen sobre los parámetros morfológicos del tejido muscular. El objetivo de este estudio fue analizar los cambios morfológicos en el tejido muscular esquelético. Se utilizaron 12 ratas (Rattus novergicus) hembras de la cepa Sprague Dawley, las cuales fueron inyectadas en el vientre del músculo gastrocnemio derecho con: solución vehículo estéril (G1, n=4) y con micropartículas 0,5 mg (G2, n=4) y 0,75 mg de PLGA (G3, n=4) ambas disueltas en solución vehículo estéril. A los 14 días post inyección se determinó el número y diámetro de fibras musculares, el nivel de inflamación y el aspecto histológico en términos de organización de fibras musculares, así como la distribución y morfología celular del tejido conjuntivo y presencia de residuos poliméricos, comparándose los resultados entre los grupos de estudio. La administración del compuesto en una sola dosis no modificó los parámetros morfométricos (número y diámetro de las fibras musculares), a pesar de generar una inflamación leve en el tejido, asociado a la presencia de residuos poliméricos, lo que sugiere que microesferas de PLGA son bien toleradas por el tejido muscular en las concentraciones probadas (0,5 and 0,75 mg).

Implantes intra-ósseos de material à base de ácido poliláctico em mandíbula de coelhos. Estudo histológico / The use of polylactic acid implants in surgical defects of rabbits mandibles. Histological analysis

Materiais biodegradáveis usados em cirurgia óssea têm sido pesquisados há mais de três décadas. Os implantes biodegradáveis mais comumente testados são os ácidos polilácticos e sua biocompatibilidade é considerada de excelência. Outros estudos demonstraram apenasbiodegradação parcial que resultou em respostas teciduais de processos inflamatórios em longo prazo. Objetivo: o presente estudo tem a finalidade de avaliar histologicamente o comportamento de um material a base de ácido poliláctico após sua implantação em cavidades ósseas em mandíbulade coelhos. Material e método: a amostra foi constituída de 16 coelhos adultos que foram divididos em dois grupos. Grupo I: cavidades ósseas cirúrgicas preenchidas com material à base de ácidopoliláctico que foi utilizado como grupo teste; e Grupo II; cavidades ósseas cirúrgicas preenchidas com coágulo sangüíneo, perfazendo o grupo controle. Após 15, 30, 60 e 90 dias, os animais foramsacrificados e as mandíbulas processadas segundo rotina laboratorial histológica para coloração em H.E. Resultado: aos 15 dias, o material encontra-se com reação inflamatória intensa e iníciode formação de cápsula fibrosa. Aos 30 dias o material permanece na cavidade e observa-se início de formação óssea advinda da parede da cavidade. Aos 60 dias, ausência de infiltrado inflamatórioe presença de osso neoformado ao redor do implante. Aos 90 dias, o osso neoformado apresenta aspecto organizado e mais maduro. Conclusão: o material à base de ácido poliláctico implantadomostrou-se biocompatível, sendo bem aceito pelo tecido ósseo adjacente ao implante. Porém não sofreu processo de degradação ou reabsorção nos períodos avaliados.

The biodegradable materials used in bone surgery have been researched for more than three decades. The most commonly tested bioresorbable implants are the polylactic acids which present excellent biocompatibility. On the other hand, some studies showed only partial degradation and variable long-term tissue reactions. Objective: This study evaluated the histological behavior of a polylactic acid-based material after implantation into extensive and deep surgical cavities in rabbit mandibles. Material and method: Sixteen adult rabbits were used in this study. Ineach animal a surgical cavity was prepared in the mandible. The sixteen rabbits were divided into two groups: Group I- surgical cavities filled with polylactic acid material and, Group II- surgical cavities filled with blood clot as controls. After fifteen, thirty, sixty and ninety days the animalswere sacrificed and the mandibles were dissected for histological processing and analysis. Results: After 15 days, the implant showed inflammatory reaction and capsule formation. After 30 days,the material remained in the surgical cavity without degradation and beginning of bone formation was observed. At sixty days, the inflammatory process was absent and the material was surroundedby bone. At 90 days, lamellar bone was formed. Conclusion: The polydactyl acid implants were biocompatible and well accepted by the adjacent bone. However, with ninety days the materialstill remained in the surgical cavity without degradation.