FGFR 3 is one of a family of four high affinity receptors for FGF ligands. Activating mutations in FGFR 3 result in skeletal dysplasias that vary in severity from undetectable to neonatal lethal. Mice with congenital deficiency of FGFR3 develop severe kyphosis and skeletal overgrowth. FGFR3 is also expressed in calvarial pre-osteoblasts, osteoblast and articular chondrocytes, although it biological role in these cells remains undefined. By changing the genetic background of the Fgfr3-/- mice we were able to extend their lifespan and examine its impact on post-natal skeletal growth. To investigate the implication of FGFR 3 in post-natal cartilage and bone metabolism we used a combination of imaging, classic histology, molecular biology and biomechanical testing. The results demonstrated that the synovial joints of young adult Fgfr3-/- mice revealed a progressive deterioration, loss of the joint space width and changes in the subchondral bone. These alterations were accompanied by an increase of cartilage matrix degradation. Increased aggrecan and collagen type II degradation products, generated by MMPs were detected with DIAPEN and COL2-3/4C antibodies. Increased collagen type X, cellular hypertrophy and loss of proteoglycan at the articular surface were also demonstrated. A novel micro-mechanical indentation protocol revealed that the humeral heads of Fgfr3-/- mice were less stiff than those of wild type littermates. On the other hand, young adult Fgfr3-/- mice are osteopenic due to reduced cortical bone thickness and defective trabecular bone mineralization. The reduction in mineralized bone and lack of trabecular connectivity observed by micro-computed tomography were confirmed by histological and histomorphometric analyses, which revealed a significant decrease in calcein labeling of mineralizing surfaces and a significant increase in osteoid in the long bones of 4-month-old Fgfr3-/- mice. Primary cultures of adherent bone marrow-derived cells from Fgfr3-/- mice expressed markers of differentiated osteoblasts but developed fewer mineralized nodules than Fgfr3+/+ cultures of the same age. These data point to a major role for FGFR3 signaling in development and homeostatic maintenance of cartilage and bone post-natally and identify FGFR3 as a potential target for intervention in degenerative disorders of cartilage, osteopenia and those associated with defective bone mineralization.

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INTRODUÇÃO e OBJETIVO: A osteoartrite (OA) embora frequente tem patogênese incerta em humanos. Descrevemos modelo experimental original de OA em cães, analisando em dois tempos diferentes as consequências da Ruptura Espontânea do Ligamento Cruzado Cranial (RLCCr). MÉTODOS: Vinte animais machos com menos de 5 anos ( 20 a 45 Kg) com RLCCr submetidos à artrotomia para estabilização articular tiveram fragmentos articulares removidos para análise. O grupo RLCCr < 20 (10 animais) foi operado antes dos vinte dias e o grupo > 20 (10 animais) após 20 dias do início da lesão. Sete animais com OA pré-existente (OA) que morreram por quaisquer motivos e 7 animais normais (NC) provenientes do C.C.Z., serviram de grupos controles. Os animais foram avaliados clinica e radiologicamente. Foi colhido líquido sinovial dos animais operados e de outros 20 cães controles submetidos às cirurgias por diferentes causas. Para estudo morfológico, os fragmentos de cartilagens foram corados com H&E e Picrossirius. A gravidade do escore histológico da OA foi quantificada através da coloração com Safranina O. Analisou-se citocinas próinflamatórias (IL-6, TNF-alfa) e a quimiocina CCL2/MCP-1 nos líquidos sinoviais. RESULTADOS: Todos os cães tinham o teste de movimento da gaveta e exame de compressão da mesa tibial positivos. Achados radiográficos correlacionaram-se com maior tempo de RLCCr. Cartilagem articular de animais normais (NC) exibiram superfície preservada, disposição ordenada dos condrócitos e integridade da rede de colágeno. Exames histológicos em animais do grupo RLCCr < 20 mostraram irregularidades na superfície articular, diminuição no número de condrócitos e remodelamento de fibras de colágeno. No grupo > 20, observou-se osteófitos e irregularidades evidentes nas superfícies articulares. A gravidade do escore de acometimento histológico traduziu-se por intensa diminuição celular na superfície articular, com presença de clusters de condrócitos na região intermediária da cartilagem e total desorganização da rede de fibras de colágeno. A quimiocina CCL2/MCP-1 esteve aumentada no grupo com menos de 20 dias de lesão, enquanto a IL-6 foi mais expressiva nos animais operados tardiamente. CONCLUSÃO: O modelo experimental espontâneo de OA canino, estudado em dois tempos, é um instrumento original e útil para estudo da patogênese da osteoartrite, além de ter o mérito de preservar a integridade física dos animais de laboratório / INTRODUCTION and OBJECTIVE: Osteoarthritis (OA) is a frequent and severe rheumatic disease of unknown pathogenesis. We described an original experimental model of OA, analyzing the consequences of spontaneous cranial cruciate ligament rupture (RLCCr), occurred at two different times. METHOD: Twenty male animals, younger than 5 years old (20 to 45kg) with RLCCr were submitted to arthrotomy for articular stability and had cartilage fragments removed for analysis. The Group RLCCR < 20 (10 animals) was operated before 20 days and Group RLCCR > 20 (10 animals) after 20 days of beginning of lesion. Seven animals with pre-existent OA which died without any reason, and 7 normal animals (NC) from Service of Zoonosis Control were the control groups. The animals were submitted to clinical and radiological evaluations. Synovial fluid were collected from operated dogs and from another 20 control animals, submitted for surgical procedures for any reason. For the morphological study, the cartilage fragments were stained with H&E and Picrossirus. The score for OA severity was quantified using Safranin-O staining. Inflammatory cytokines (IL-6 and TNF alfa) and chemiokine CCL2/MCP-1 were measured in sinovial fluid. RESULTS: At physical examination, all the dogs had positive drawer and the tibial plateau compression tests. Knee Radiographic data showed that narrowing of joint space, osteophytes and erosions were more prominent in Group RLCCr> 20 animals. Articular cartilage of normal animals (NC) revealed preserved cartilage surface, organized disposition of chondrocytes and integrity of collagen net. Histological exams done in animals from Group RLLCr > 20 showed irregularities on articular surface, reduction of the number of chondrocytes and collagen fibers remodeling. Animals from Group RLCCR > 20 exhibited deep fibrillations, presence of chondrocytes clusters at intermediate area of cartilage, osteophytes and and total disorganization of the collagen fibers net. Chemiokine CCL2/MCP-1 was found overexpressed in dogs operated less than 20 days, while IL-6 was increased in late surgical group. CONCLUSION: The spontaneous model of canine RLCCr, studied at two distinct times, is an original and useful tool to understand pathogenesis of OA. Furthermore, the procedure preserves the animal integrity, becoming an Ethical laboratorial procedure

INTRODUÇÃO e OBJETIVO: A osteoartrite (OA) embora frequente tem patogênese incerta em humanos. Descrevemos modelo experimental original de OA em cães, analisando em dois tempos diferentes as consequências da Ruptura Espontânea do Ligamento Cruzado Cranial (RLCCr). MÉTODOS: Vinte animais machos com menos de 5 anos ( 20 a 45 Kg) com RLCCr submetidos à artrotomia para estabilização articular tiveram fragmentos articulares removidos para análise. O grupo RLCCr < 20 (10 animais) foi operado antes dos vinte dias e o grupo > 20 (10 animais) após 20 dias do início da lesão. Sete animais com OA pré-existente (OA) que morreram por quaisquer motivos e 7 animais normais (NC) provenientes do C.C.Z., serviram de grupos controles. Os animais foram avaliados clinica e radiologicamente. Foi colhido líquido sinovial dos animais operados e de outros 20 cães controles submetidos às cirurgias por diferentes causas. Para estudo morfológico, os fragmentos de cartilagens foram corados com H&E e Picrossirius. A gravidade do escore histológico da OA foi quantificada através da coloração com Safranina O. Analisou-se citocinas próinflamatórias (IL-6, TNF-alfa) e a quimiocina CCL2/MCP-1 nos líquidos sinoviais. RESULTADOS: Todos os cães tinham o teste de movimento da gaveta e exame de compressão da mesa tibial positivos. Achados radiográficos correlacionaram-se com maior tempo de RLCCr. Cartilagem articular de animais normais (NC) exibiram superfície preservada, disposição ordenada dos condrócitos e integridade da rede de colágeno. Exames histológicos em animais do grupo RLCCr < 20 mostraram irregularidades na superfície articular, diminuição no número de condrócitos e remodelamento de fibras de colágeno. No grupo > 20, observou-se osteófitos e irregularidades evidentes nas superfícies articulares. A gravidade do escore de acometimento histológico traduziu-se por intensa diminuição celular na superfície articular, com presença de clusters de condrócitos na região intermediária da cartilagem e total desorganização da rede de fibras de colágeno. A quimiocina CCL2/MCP-1 esteve aumentada no grupo com menos de 20 dias de lesão, enquanto a IL-6 foi mais expressiva nos animais operados tardiamente. CONCLUSÃO: O modelo experimental espontâneo de OA canino, estudado em dois tempos, é um instrumento original e útil para estudo da patogênese da osteoartrite, além de ter o mérito de preservar a integridade física dos animais de laboratório / INTRODUCTION and OBJECTIVE: Osteoarthritis (OA) is a frequent and severe rheumatic disease of unknown pathogenesis. We described an original experimental model of OA, analyzing the consequences of spontaneous cranial cruciate ligament rupture (RLCCr), occurred at two different times. METHOD: Twenty male animals, younger than 5 years old (20 to 45kg) with RLCCr were submitted to arthrotomy for articular stability and had cartilage fragments removed for analysis. The Group RLCCR < 20 (10 animals) was operated before 20 days and Group RLCCR > 20 (10 animals) after 20 days of beginning of lesion. Seven animals with pre-existent OA which died without any reason, and 7 normal animals (NC) from Service of Zoonosis Control were the control groups. The animals were submitted to clinical and radiological evaluations. Synovial fluid were collected from operated dogs and from another 20 control animals, submitted for surgical procedures for any reason. For the morphological study, the cartilage fragments were stained with H&E and Picrossirus. The score for OA severity was quantified using Safranin-O staining. Inflammatory cytokines (IL-6 and TNF alfa) and chemiokine CCL2/MCP-1 were measured in sinovial fluid. RESULTS: At physical examination, all the dogs had positive drawer and the tibial plateau compression tests. Knee Radiographic data showed that narrowing of joint space, osteophytes and erosions were more prominent in Group RLCCr> 20 animals. Articular cartilage of normal animals (NC) revealed preserved cartilage surface, organized disposition of chondrocytes and integrity of collagen net. Histological exams done in animals from Group RLLCr > 20 showed irregularities on articular surface, reduction of the number of chondrocytes and collagen fibers remodeling. Animals from Group RLCCR > 20 exhibited deep fibrillations, presence of chondrocytes clusters at intermediate area of cartilage, osteophytes and and total disorganization of the collagen fibers net. Chemiokine CCL2/MCP-1 was found overexpressed in dogs operated less than 20 days, while IL-6 was increased in late surgical group. CONCLUSION: The spontaneous model of canine RLCCr, studied at two distinct times, is an original and useful tool to understand pathogenesis of OA. Furthermore, the procedure preserves the animal integrity, becoming an Ethical laboratorial procedure