Comparison between heparin-conjugated fibrin and collagen sponge as bone morphogenetic protein-2 carriers for bone regeneration

Bone morphogenetic protein-2 (BMP-2) is used to promote bone regeneration. However, the bone regeneration ability of BMP-2 relies heavily on the delivery vehicle. Previously, we have developed heparin-conjugated fibrin (HCF), a vehicle for long-term delivery of BMP-2 and demonstrated that long-term delivery of BMP-2 enhanced its osteogenic efficacy as compared to short-term delivery at an equivalent dose. The aim of this study was to compare the bone-forming ability of the BMP-2 delivered by HCF to that delivered by clinically utilized BMP-2 delivery vehicle collagen sponge. An in vitro release profile of BMP-2 showed that HCF released 80% of the loaded BMP-2 within 20 days, whereas collagen sponge released the same amount within the first 6 days. Moreover, the BMP-2 released from the HCF showed significantly higher alkaline phosphatase activity than the BMP-2 released from collagen sponge at 2 weeks in vitro. Various doses of BMP-2 were delivered with HCF or collagen sponge to mouse calvarial defects. Eight weeks after the treatment, bone regeneration was evaluated by computed tomography, histology, and histomorphometric analysis. The dose of BMP-2 delivered by HCF to achieve 100% bone formation in the defects was less than half of the BMP-2 dose delivered by collagen sponge to achieve a similar level of bone formation. Additionally, bone regenerated by the HCF-BMP-2 had higher bone density than bone regenerated by the collagen sponge-BMP-2. These data demonstrate that HCF as a BMP-2 delivery vehicle exerts better osteogenic ability of BMP-2 than collagen sponge, a clinically utilized delivery vehicle.

Effect of bovine type-I collagen-based films containing red propolis on dermal wound healing in rodent model / Efecto de películas a base de colágeno bovino tipo I que contienen propóleo rojo sobre la cicatrización de la herida cutánea en un modelo roedor

Propolis, an apitherapic product widely employed in natural medicine, presents various biological properties, such as bactericidal and anti-inflammatory activities, but only few reports have looked at the Brazilian red propolis variety. Collagen films have been employed to improve wound healing and some studies have investigated the effect of natural products incorporated into these films. Thus, the aim of this study was to analyze the effect of collagen-based films containing red propolis on wound healing. Therefore, wounds performed in the back of rats were dressed with collagen-based films (G2), and collagen-based films containing red propolis (G3); undressed worked as control (G1). After 3, 7 and 14 days the animals were euthanized, and the wounds were microscopically evaluated. In 7 days, G3 showed switch of the inflammatory profile from acute into chronic, increased plasma cells differentiation, replacement of Type-III for type-I collagen fibers, and better architectural organization of those fibers. Furthermore, a slight tendency for a better epithelization was verified in G3, but it was not statistically significant. Also in 7 days, the microvessels count was higher in G1 than in G2 (p=0.000) and G3 (p=0.001), but similar between the last groups (p=0,15), whereas the microvessels perimeter was higher in G1 than in G2 (p=0.000) and G3 (p=0.002), but equivalent in G2 and G3 (p=0.175) in 14 days. In conclusion, the incorporation of Brazilian red propolis into collagen-based films was able to improve wound healing, probably by modulating the dynamics of the inflammatory evolution and collagen deposition process.

El propóleo es un producto apiterápico ampliamente usado en medicina natural, que presenta diversas propiedades biológicas, como actividad bactericida y anti-inflamatoria, pero pocos informes han examinado la variedad brasileña del propóleo rojo. Películas de colágeno han sido empleadas para mejorar la cicatrización de heridas y en algunos estudios se ha investigado el efecto de los productos naturales incorporados en estas películas. Así el objetivo de este estudio fue analizar el efecto de las películas a base de colágeno que contienen propóleo rojo en la cicatrización de heridas. Heridas realizadas en el dorso de ratas fueron revestidas con películas a base de colágeno (G2) y con películas a base de colágeno con propóleo rojo (G3), heridas sin revestimiento fueron utilizadas como control (G1). Después de 3, 7 y 14 días, las heridas fueron evaluadas microscópicamente. A los 7 días G3 mostró un cambio del perfil de la respuesta inflamatoria de aguda a crónica, con aumento de la diferenciación de las células plasmáticas, sustitución de fibras de colágeno tipo III por tipo I con mejora de la organización arquitectónica de estas fibras. Además, una ligera tendencia a una mejor epitelización se verificó en G3, pero no fue estadísticamente significativa. También a los 7 días, el conteo de microvasos fue mayor en G1 que en G2 (p=0,000) y G3 (p=0,001), pero similar entre los últimos grupos (p=0,15), mientras que el perímetro de los microvasos fue mayor en G1 que en G2 (p=0,000) y G3 (p=0,002), pero equivalente en G2 y G3 (p=0,175) en 14 días. En conclusión, la incorporación de la variedad brasileña de propóleo rojo en películas a base de colágeno fue capaz de mejorar la cicatrización de la herida, probablemente por la modulación de la dinámica de la evolución inflamatoria y del proceso de depósito de colágeno.

Naturally supraorganized collagen increases axonal regeneration after tubulization repair

After axotomy, regeneration can be enhanced by bridging the transected nerve with a biocompatible tube, and the effect of trophic substances or molecules from the extracellular matrix can be investigated by filling the prosthesis. In this study, we assessed the importance of the molecular organization and aggregational state of collagen type I in axonal regeneration and guidance. Two types of collagen were used, namely, a collagen gel derived from bovine tendon that displays supraorganization after extrusion, and collagen from rat tail which does not self-organize under such conditions. Adult male Wistar rats were divided into four groups. In the first group (n=3), the polyethylene tube was filled with bovine collagen, while in the second (n=3), the prosthesis was filled with rat-derived collagen. In the third group (n=3), the tube was left empty, and the fourth group (n=3), consisted of unoperated rats. Six weeks after tubulization, the number of axons was significantly higher with bovine collagen than with rat collagen (7,661 ± 1,018 versus 4,110 ± 1,027, p<0.05), as was the degree of implant absorption. These results support the hypothesis that the use of extracellular matrix substances that self-assembly in an organized pattern can enhance nerve regeneration.