RESUMO
Naturally derived tendon scaffolds have the potential to improve the treatment of flexor tendon injuries. Seeded and unseeded tendon scaffolds were maintained in the presence or absence of physiologic strain for 7 days. After 7 days, the tensile properties and associated messenger RNA expression were compared. Seeded scaffolds maintained in the absence of strain had significantly lower tensile properties than unseeded tendons and fresh-frozen tendons. The loss of tensile properties was associated with elevated matrix metalloproteinase-2 and collagen III expression. Tensile properties of seeded scaffolds maintained in the presence of strain for 7 days after seeding did not differ from those of fresh-frozen tendons. This study demonstrates that the tensile properties of seeded, naturally derived tendon scaffolds will degrade rapidly in the absence of cyclic strain. Seeded scaffolds used for tendon reconstruction should be maintained under cyclic strain to maintain essential tensile properties.
Assuntos
Reatores Biológicos , RNA Mensageiro/biossíntese , Traumatismos dos Tendões/fisiopatologia , Tendões/patologia , Engenharia Tecidual/instrumentação , Alicerces Teciduais , Aloenxertos , Desenho de Equipamento , Humanos , Traumatismos dos Tendões/genética , Traumatismos dos Tendões/metabolismo , Tendões/fisiopatologia , Tendões/transplante , Resistência à TraçãoRESUMO
Age is an important predictor of neuromuscular recovery after peripheral nerve injury. Insulin-like growth factor 1 (IGF-1) is a potent neurotrophic factor that is known to decline with increasing age. The purpose of this study was to determine if locally delivered IGF-1 would improve nerve regeneration and neuromuscular recovery in aged animals. Young and aged rats underwent nerve transection and repair with either saline or IGF-1 continuously delivered to the site of the nerve repair. After 3 months, nerve regeneration and neuromuscular junction morphology were assessed. In both young and aged animals, IGF-1 significantly improved axon number, diameter, and density. IGF-1 also significantly increased myelination and Schwann cell activity and preserved the morphology of the postsynaptic neuromuscular junction (NMJ). These results show that aged regenerating nerve is sensitive to IGF-1 treatment.
Assuntos
Envelhecimento/efeitos dos fármacos , Fator de Crescimento Insulin-Like I/administração & dosagem , Regeneração Nervosa/efeitos dos fármacos , Nervo Tibial/efeitos dos fármacos , Nervo Tibial/lesões , Fatores Etários , Envelhecimento/fisiologia , Análise de Variância , Animais , Axônios/efeitos dos fármacos , Axônios/fisiologia , Proteína GAP-43/genética , Proteína GAP-43/metabolismo , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiologia , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Fibras Nervosas Mielinizadas/fisiologia , Regeneração Nervosa/fisiologia , Junção Neuromuscular/efeitos dos fármacos , Junção Neuromuscular/fisiologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células de Schwann/efeitos dos fármacos , Células de Schwann/fisiologiaRESUMO
BACKGROUND: Interactions between the peripheral nervous system and the healing skeleton are poorly understood. Various clinical observations suggest that the nervous system interacts with and promotes fracture-healing. The purpose of this study was to examine the effect of selective sensory denervation on fracture-healing. METHODS: Fifty-one Sprague-Dawley rats underwent unilateral placement of an intramedullary rod followed by creation of a standardized femoral fracture. One group of these rats underwent sensory denervation by means of a localized capsaicin injection, and the other did not. Subgroups were allocated for analysis of mRNA expression of collagen I and II and osteocalcin at three, seven, and fourteen days after the fracture. Additionally, histological examination was performed at four weeks; micro-computed tomography, at five weeks; and biomechanical testing, at six weeks. RESULTS: The sensory-denervated group had significantly less collagen-I upregulation than the sensory-intact group at three days after the fracture (difference in means, forty-four-fold [95% confidence interval = 22.7 to 65.5-fold]; p < 0.001) and significantly less collagen-II upregulation at seven days after the fracture (difference in means, ninefold [95% confidence interval = 4.3 to 13.8-fold]; p < 0.001). In the sensory-denervated group, the fracture callus had a significantly larger cross-sectional area (difference in means, 15.6 mm(2) [95% confidence interval = 0.78 to 30.5 mm(2)]; p = 0.043) and was less dense. Biomechanical testing revealed that sensory denervation significantly decreased the load to failure (difference in means, 28.7 N [95% confidence interval = 1.2 to 56.2 N]; p = 0.022). CONCLUSIONS: Sensory denervation negatively affects fracture-healing. These results offer insight into the nerve-bone interaction following injury.
