In Vitro and In Vivo (Rabbit, Guinea Pig, Mouse) Properties of a Novel Resorbable Polymer and Allogenic Bone Composite for Guided Bone Regeneration and Orthopedic Implants.

INTRODUCTION: Currently, there is no bone fixation material that could be fully replaced by the competent recipient bone. The creeping substitution of the bone graft by the recipient bone is the result of its unique potential related to the presence of bone morphogenetic proteins (BMPs). However, the size of the human bone limits the use of allogenic implants for surgical (orthopedic) fixation. The aim of this project was to develop a novel composite material for guided bone regeneration, consisting of human bone powder obtained from a tissue bank and a resorbable polymer (13 wt% of bone powder in a medical poly-l-lactide polymer). Such a biomaterial could possess osteoinductive properties and be used to manufacture bone fixation implants of different shapes and sizes. MATERIALS AND METHODS: The samples were obtained by tape casting and foils pressing, and subsequently radiation sterilized with a dose of 35 kGy. Two cell lines-normal mouse embryo fibroblasts (Balb 3T3/c) and human fetal osteoblasts (hFOB 1.19)-were cultured with the extracts of the biomaterials (MTT assay) or in indirect contact with the evaluated biomaterials (agar diffusion method). In addition, cell viability was evaluated after 5 days of incubation with biomaterial using ThinCert tissue culture inserts. Then, the following in vivo examinations were conducted: acute systemic toxicity, skin irritation and sensitization, and local effects after implantation. RESULTS: The evaluated composite material showed a high degree of cytocompatibility and biocompatibility according to the International Standards. CONCLUSIONS: The preclinical evaluation we performed on the new, polylactide-based allogenic biomaterial opens up possibilities to patent pending and advanced in vivo testing.

The influence of steroids on vascular tension of isolated superficial veins of the nose and face during the estrous cycle of gilts.

The arrangement of the superficial facial veins enables blood flow from the nasal cavity into the peripheral circulation by two pathways: through the frontal vein into the cavernous sinus and through the facial vein into the external jugular vein. The current study was designed to determine whether estradiol and progesterone affect the vascular tone of the superficial veins of the nose and face in cycling gilts (Sus scrofa f. domestica) and to analyze the immunolocalization of progesterone receptors and estradiol receptors in these veins. The influence of hormones on vascular tension differed depending on the type of vessel and the phase of the estrous cycle. Estradiol decreased vascular tension in the nasal vein during the follicular phase (P<0.05) and increased tension in the frontal vein during the luteal phase (P<0.05). Progesterone increased the vascular tension of the frontal vein (P<0.05) and decreased the tension of the other veins (P<0.05) in both phases of the cycle. Expression of estradiol receptor beta but not of progesterone receptor was observed in the superficial veins of the nose and face. In conclusion, the effect of ovarian steroid hormones on the vascular tension of the superficial veins of the nose and face in female pigs as well as the reactivity of these veins to steroid boar pheromones can affect the blood supply from the nasal cavity to the venous cavernous sinus. We propose that the ovarian steroid hormones that modulate the vascular tension of the nasal and facial veins may also influence the action of boar pheromones absorbed into the nasal mucosa in gilts and may reach the brain via local destination transfer.

The effect of intravaginal application of estradiol and progesterone on porcine embryo development.

This study was designed to check whether intravaginal application of estradiol and progesterone on chosen days of early pregnancy affects the development and survival of porcine embryos. Crossbred gilts were assigned to control (C-1 and C-2) or experimental (T-1 and T-2) groups. Systemic blood samples were collected in groups C-1 and T-1 on days 3-18 of pregnancy. Gilts of control groups were supplied on days 2-6 and 12-17 of pregnancy with intravaginal cocoa butter suppositories. Gilts of experimental groups were intravaginally supplied on days 2-6 of pregnancy with estradiol (0.2 mg) to improve uterine blood supply and on days 12-17 of pregnancy gilts were supplied with progesterone (0.25 mg) to stimulate the secretory function of the endometrium during the periimplantation period. Systemic concentration of progesterone was elevated on days 3-6 and of estradiol on days 4, 5 and 10 of pregnancy in the experimental groups in comparison with the control gilts. The weight of the ovary and number of corpora lutea were similar in the control and experimental groups, but the number of follicles over 3 mm in diameter was higher in the experimental groups than in control (P < 0.01) on day 30 of pregnancy. The mean ovulation rate, total number of embryos and rate of embryo survival on day 30 of pregnancy were similar in the control and experimental groups. However, the weight, crown-rump length and width of embryos were greater in the experimental groups than in control (P < 0.001). The results demonstrated that the intravaginal application of estradiol and progesterone on precisely chosen days of early pregnancy stimulated embryo development. This study demonstrated that the timing of hormone administration must comply with the physiological effect of estradiol and progesterone on uterine blood supply to ensure embryo development and survival.

Retrograde transfer of steroid hormones to the ovary in luteal and follicular phases of porcine oestrous cycle in vivo.

The efficiency of the retrograde transfer of steroid ovarian hormones from the ovarian effluent into blood supplying the ovary and the rate of its back transport to the ovary were determined for the first time in in vivo conditions. Sexually mature gilts (n = 25) were used in the physiological study. The concentration of oestradiol and progesterone in blood collected from the ovarian artery was higher in both the follicular phase (by 87.9 +/- 2.9% and 150.0 +/- 4.8%, respectively, P < 0.001) and the luteal phase (by 82.1 +/- 3.9% and 77.7 +/- 2.7%, respectively, P < 0.001) than in systemic blood reaching the initial part of the ovarian artery. The high efficiency of the retrograde transfer was not dependent on the concentration of hormones in the ovarian venous blood. However, the efficiency and rate of the retrograde transfer differed between phases of the oestrous cycle. We suggest that such effective retrograde transfer of ovarian hormones must affect the secretory function of the ovary.

Retrograde transfer of ovarian steroid hormones to the ovary in the porcine periovarian vascular complex.

The aim of the present study was to investigate the mechanism of the retrograde transfer of ovarian steroid hormones from the ovarian lymphatic and venous effluent to the arterial blood supplying the ovary. In the first experiment, reproductive organs were collected from gilts in the luteal (n = 10) and follicular (n = 10) phase of the oestrous cycle. The ovary with the mesovarium was isolated and perfused through the ovarian artery with warmed, oxygenated autologous blood. The concentrations of progesterone and oestradiol in ovarian arterial blood increased on passing through the ovarian artery to the ovary, in the luteal phase, from 20.3 +/- 2.1 to 31.4 +/- 3.9 ng ml(-1) (P < 0.001) and from 6.2 +/- 0.8 to 11.4 +/- 1.4 pg ml(-1) (P < 0.001), respectively, and in the follicular phase, from 1.2 +/- 0.2 to 2.2 +/- 0.4 ng ml(-1) (P < 0.001) and from 8.2 +/- 1.8 to 13.2 +/- 2.3 pg ml(-1) (P < 0.001), respectively. Approximately 17.5 +/- 3.9 % of the progesterone and 12.6 +/- 1.7 % of the oestradiol found in the ovarian venous effluent was retrogradely transferred from the ovarian venous blood to the ovary in the luteal phase. In the follicular phase, these values were 10.1 +/- 2.0 % and 8.6 +/- 1.4 %, respectively. The efficiency of retrograde transfer of oestradiol and the rate of retrograde transfer of progesterone differed between phases of the oestrous cycle (P < 0.05 and P < 0.0001, respectively). A direct relationship between the concentration of the steroids in the venous effluent and the efficiency and rate of the retrograde transfer to the ovary was not found. In the second experiment (luteal phase, n = 10; follicular phase, n = 5), the concentration of progesterone and oestradiol increased in both ovarian arterial blood (P < 0.0001) and in the venous effluent (P < 0.0001) after administration of the steroids into the lymphatic vessels of the isolated mesovarium with separated ovary. In the third experiment (follicular phase, n = 5), with the mesovarium isolated after the ovary was removed and ovarian venous blood flowing out under the force of gravity (without the blood pressure in the ovarian vein), it was demonstrated that the veno-venous network covering the branches of the ovarian artery was supplied with the blood flowing out from the mesovarian tissue and that the filling of the veno-venous network was dependent on the blood pressure in the ovarian artery. We conclude that the effective retrograde transfer of steroid hormones from ovarian venous and lymphatic effluent to the ovary is accomplished not only by the classical counter-current exchange mechanism, but also as a result of complex processes that may be dependent on a specific part of the circulation of the blood and lymph in the periovarian vascular complex of the mesovarium.

Interaction between carbon composites and bone after intrabone implantation.

Candidate carbon fiber reinforced carbon (CFRC) porous implant materials were evaluated for tissue compatibility in a rat model. Six different CFRCs of constant pore size (about 30 microm) were fabricated that had 9, 12, and 17% porosity with 2-nm3 matrix crystallites and 6, 12, and 20% at 25 nm3. They were implanted as femoral transverse diaphyseal pins that were 1.5 mm in diameter. At 5 and 45 weeks, implant and bone histologic specimens were evaluated histologically and by a scanning electron microscope and an electron microprobe. Also, regional lymph nodes and spleens were examined. By 45 weeks, direct implant-bone contact was observed over most of the interface in most specimens. At the implant surface, there was partial replacement of CFRC with host tissue. However, the microprobe showed that the implant-bone interface was chemically abrupt with no cross-diffusion of ionic species. Besides the surface effects, there was partial filling of the implant pores with tissue, including bone organized de novo deep within. This was observed histologically and confirmed by microprobe. Lymph nodes and spleens were histologically normal, and no carbon particles were found. None of the results were influenced by porosity or matrix crystallite size over the ranges studied. In summary, these porous CFRCs are partially degraded when in contact with bone and appear substantially tissue compatible. They may be useful as scaffolds for regrowth of bone.

Experimental study of mechanical properties of composite carbon screws.

Carbon-carbon composite was used to manufacture carbon screws as possible material for osteosynthesis. The mechanical properties were optimized including the fibre orientation in the composite volume, the effect of the size of the thread and the thread shape. The mechanical properties of the carbon screws were compared with conventional OSTEO steel cortical screws. Two types of carbon specimens were used, varying in fibre orientation along the screw axis. The mechanical properties of the carbon screws including the failure force for one thread and the critical shear stress were determined. The force destroying the connection of the carbon screw with bone was determined. The holding capacity of the carbon screw was compared to the steel screw. The extraction tests demonstrated 50% less holding force than the OSTEO steel screw.

Static and dynamic fatigue properties of carbon ligament prosthesis.

The aim of the present paper was to characterize the static and dynamic mechanical properties of carbon braids used in medicine as prostheses of ligaments and tendons. A computing system (PC software) was used to register and analyze the data of mechanical tests. Tensile static tests (creep testing) were utilized to determine the failure-free value of static force. Fatigue dynamic properties of carbon braids in tensile-tensile cyclic tests including the effect of simulated body conditions were analyzed. The braids were immersed in isotonic solution at 37 degrees C. Fatigue life was markedly lowered in air in comparison with simulated body conditions. For a given value of maximum cyclic force, decreasing the minimum/maximum force ratio decreased the number of cycles to failure. The mechanical approach of fatigue behavior based on approximately maximum fatigue force and number of cycles to failure by analytical expression was given. Energy dissipation due to the hysteresis loop was considered.

[The possibility of using carbon material in surgery of joints]. / Mozliwosci zastosowania materialów weglowych w chirurgii narzadu ruchu.

The experiments consisting in replacement of a dissected anterior cruciate ligament of the knee in rabbits with a bundle of parallel carbon fibers and a braided carbon covered with animal collagen lyophilized dura mater have been performed. Similar experiments have been performed on dogs. The lateral ligaments of the knee were also restored, longitudinally cut menisci and the Achilles tendon were sutured. The produced carbon plate and metal screws were used to fix bone fracture. The positive results of the experiments on animals with the use of carbon fibers of Polish make have proved the possibility of their employment for periarticular ligament reconstruction, suturing, Achilles tendon injuries and juxta capsular meniscus rupture. The union of bone fracture with a composite carbon plate has shown the superiority of "carbon" osteosynthesis over "metal" one. It is believed that carbon materials will be used clinically more widely.