Collagen-chitosan-hydroxyapatite composite scaffolds for bone repair in ovariectomized rats.

Lesions with bone loss may require autologous grafts, which are considered the gold standard; however, natural or synthetic biomaterials are alternatives that can be used in clinical situations that require support for bone neoformation. Collagen and hydroxyapatite have been used for bone repair based on the concept of biomimetics, which can be combined with chitosan, forming a scaffold for cell adhesion and growth. However, osteoporosis caused by gonadal hormone deficiency can thus compromise the expected results of the osseointegration of scaffolds. The aim of this study was to investigate the osteoregenerative capacity of collagen (Co)/chitosan (Ch)/hydroxyapatite (Ha) scaffolds in rats with hormone deficiency caused by experimental bilateral ovariectomy. Forty-two rats were divided into non-ovariectomized (NO) and ovariectomized (O) groups, divided into three subgroups: control (empty defect) and two subgroups receiving collagen/chitosan/hydroxyapatite scaffolds prepared using different methods of hydroxyapatite incorporation, in situ (CoChHa1) and ex situ (CoChHa2). The defect areas were submitted to macroscopic, radiological, and histomorphometric analysis. No inflammatory processes were found in the tibial defect area that would indicate immune rejection of the scaffolds, thus confirming the biocompatibility of the biomaterials. Bone formation starting from the margins of the bone defect were observed in all rats, with a greater volume in the NO groups, particularly the group receiving CoChHa2. Less bone formation was found in the O subgroups when compared to the NO. In conclusion, collagen/chitosan/hydroxyapatite scaffolds stimulate bone growth in vivo but abnormal conditions of bone fragility caused by gonadal hormone deficiency may have delayed the bone repair process.

Use of an anionic collagen matrix made from bovine intestinal serosa for in vivo repair of cranial defects.

Polymeric biomaterials composed of extracellular matrix components possess osteoconductive capacity that is essential for bone healing. The presence of collagen and the ability to undergo physicochemical modifications render these materials a suitable alternative in bone regenerative therapies. The objective of this study was to evaluate the osteogenic capacity of collagen-based matrices (native and anionic after alkaline hydrolysis) made from bovine intestinal serosa (MBIS). Twenty-five animals underwent surgery to create a cranial defect to be filled with native and anionic collagen matrixes, mmineralized and non mineralized. The animals were killed painlessly 6 weeks after surgery and samples of the wound area were submitted to routine histology and morphometric analysis. In the surgical area there was new bone formation projecting from the margins to the center of the defect. More marked bone neoformation occurred in the anionic matrices groups in such a way that permitted union of the opposite margins of the bone defect. The newly formed bone matrix exhibited good optical density of type I collagen fibers. Immunoexpression of osteocalcin by osteocytes was observed in the newly formed bone. Morphometric analysis showed a greater bone volume in the groups receiving the anionic matrices compared to the native membranes. Mineralization of the biomaterial did not increase its osteoregenerative capacity. In conclusion, the anionic matrix exhibits osteoregenerative capacity and is suitable for bone reconstruction therapies.

Osseointegration of hydroxyapatite implants in rat tibial defects with sciatic nerve injury / Oseointegración de implantes de hidroxiapatita en defectos tibiales de ratas con lesión del nervio ciático

Bone metabolism is influenced by different factors and muscle activity acts as a stimulator of bone plasticity. Conditions such as nerve injuries can compromise bone physiology due to muscle inactivity. Preview studies have shown that nerve damage reduces P substance and calcitonin gene-related peptides, also known as neuropeptides that may have a key role on bone healing. Therefore, this study evaluated the osseointegration of hydroxyapatite implants in tibial defects of rats submitted to unilateral sciatic nerve section. Twelve Wistar rats were divided into two groups (G1 and G2). In G1, the sciatic nerve was left intact and in G2 the left sciatic nerve was completely sectioned. An experimental tibial bone defect was then created in both groups and filled with hydroxyapatite granules. The animals were sacrificed 2 months after implantation and samples were submitted to macroscopic inspection and histological analysis. Good radiopacity of the hydroxyapatite granules and radiographic definition of the bone defect were noted. Histologic analysis revealed formation of new bone adjacent to the hydroxyapatite granules in G1 and, to a lesser extent, in G2 in which the proliferation of connective tissue predominated at the implant site. The formation of new bone stimulated by hydroxyapatite in bone defects can be expected even in animals with limb paralysis due to nerve injury; however, bone formation occurs at a slower speed in these animals and the volume of newly formed bone is lower.

El metabolismo óseo está influenciado por diferentes factores y la actividad muscular como un estimulador de la plasticidad ósea. Condiciones tales como lesiones nerviosas pueden comprometer la fisiología ósea debido a la inactividad muscular. Estudios previos han demostrado que el daño nervioso reduce la sustancia P y el péptido relacionado con el gen de la calcitonina, también conocidos como neuropéptidos que pueden tener un papel clave en la cicatrización ósea. Este estudio evaluó la oseointegración de los implantes de hidroxiapatita en defectos tibiales de ratas sometidas a la sección del nervio ciático unilateralmente. Doce ratas Wistar se dividieron en dos grupos (G1 y G2). En G1, el nervio ciático se dejó intacto y en el G2 el nervio ciático izquierdo fue completamente seccionado. Un defecto óseo tibial fue creado experimentalmente en ambos grupos y se rellenó con gránulos de hidroxiapatita. Los animales se sacrificaron 2 meses después de la implantación y las muestras fueron sometidas a inspección macroscópica y el análisis histológico. Se observó buena radiopacidad de los gránulos de hidroxiapatita y definición radiográfica del defecto óseo. El análisis histológico reveló neoformación ósea adyacente a los gránulos de hidroxiapatita en G1 y, en menor medida en G2, donde la proliferación de tejido conectivo predominó en el sitio de implante. La neoformación ósea estimulada por hidroxiapatita en defectos óseos se puede esperar incluso en animales con parálisis de los miembros producto de una lesión nerviosa; sin embargo, la formación de hueso se produce a menor velocidad en estos animales y su volumen es menor.

Use of a new fibrin sealant and laser irradiation in the repair of skull defects in rats.

This study evaluated the osteogenic capacity of a new fibrin sealant (FS) combined with bone graft and laser irradiation in the bone repair. Defects were created in the skull of 30 rats and filled with autogenous graft and FS derived from snake venom. Immediately after implantation, low-power laser was applied on the surgical site. The animals were divided in: control group with autogenous graft (G1), autogenous graft and laser 5 J/cm2 (G2), autogenous graft and laser 7 J/cm2 (G3), autogenous graft and FS (G4), autogenous graft, FS and laser 5 J/cm2 (G5), autogenous graft, FS and laser 7 J/cm2 (G6). The animals were sacrificed 6 weeks after implant. Results showed absence of inflammatory infiltrate in the bone defect. New bone formation occurred in all groups, but it was most intense in G6. Thus, the FS and laser 7 J/cm2 showed osteoconductive capacity and can be an interesting resource to be applied in surgery of bone reconstruction.