Fracture Healing In Rats Research Articles

Oxygen-free radicals impair fracture healing in rats.

We studied the effect of oxygen-free radicals on fracture healing. 30 male rats were divided into 2 groups: 15 rats were given saline 5 mL/kg i.p. (control group) and 15 were given zymosan 100 mg/kg i.p. to induce oxygen-free radicals through stimulation of NADPH oxidase in polymorphonuclear leucocytes. 1 hour later, the right forelimbs of the rats were broken by light manual compression. These treatments were given once a day until the fifth post-fracture day. All rats were killed on day 22, and histological sections of the radius and ulna were examined without knowledge of the treatment given. The administration of zymosan impaired the fracture healing and therefore oxygen-free radicals appear to play an important role in fracture healing.

Calcium-dependent neutral proteinase (calpain) in fracture healing in rats.

Calpain refers to Ca(2+)-dependent neutral cysteine proteinase, which originally was thought to be an intracellular proteinase but recently has been shown to function extracellularly as well. This report describes the immunohistochemical demonstration of calpain and biochemical changes in the amount of calpain during fracture healing in rats. The tibiae of 6-week-old Wistar rats were fractured, and calluses were obtained 5-28 days after fracture. A frozen section of the fracture callus was stained by the immunoperoxidase method with use of polyclonal antibodies of calpains I and II. Positive staining was noted with the anti-calpain II antibody in the perivascular areas, chondrocytes, and cartilage matrix in calluses at 5, 7, and 10 days. Less intense staining was seen in older calluses. The caseinolytic activity of calpain II reached its maximum on the 5th day, was high on the 7th and 10th days, and decreased rapidly thereafter. The quantity of calpain II was dependent on the process of fracture healing. It was concluded that calpain was working as one of the matrix proteinases in fracture callus.

The effects of growth hormone on fracture healing in rats: A histological description

Previous biomechanical studies have indicated that growth hormone has a stimulatory effect on fracture healing. This study was designed to give a histological description of the long-term effects of growth hormone on fracture healing in rats. Sixty-four female rats were divided into two groups and were given either biosynthetic human growth hormone (2.7 mg/kg body weight/day) or saline s.c. in two daily injections. This treatment was given for 20 days after a closed tibial fracture with medullary nailing had been performed. Five or six rats were killed from each group after 10, 20, 30, 40, 50, and 80 days of healing. The fracture site was embedded undecalcified in methylmethacrylate, cut into 8 μm thick, midfrontal sections, and investigated in a normal light microscope after staining with Masson Trichrome and in polarized light after staining with Sirius red. The results revealed that growth hormone had an initially stimulatory effect on external callus formation. However, the callus formed was loosely structured and was not removed by the normal modeling and remodeling process. The callus therefore persisted even after 80 days of healing. In contrast, after only 40 days the saline treated rats showed healing, with a resumption of the normal size and shape of the fractured tibial bone, leaving only a small amount of dense callus tissue. The study also revealed that the hemopoietic system was stimulated by growth hormone, with massive invasion of marrow cells into the external fracture callus. Bone marrow cells dominated the intratrabecular space in growth-hormone treated animals, even after 80 days of healing. On the basis of this study, it is concluded that although there is an initially stimulatory effect of growth hormone on callus formation, the callus formed during growth hormone treatment is abnormal with an extremely loose structure, and modeling and remodeling of this callus are delayed. It seems that the bone marrow ceils grow at the expense of the mineralized callus tissue, or that the normal architecture of the callus tissue is disrupted.

The role of hematoma and periosteal sealing for fracture healing in rats.

Bilateral closed femoral fractures were produced in two groups of rats. Reaming was made from the trochanteric area before fracture, and the fractures were stabilized by intramedullary pinning. In one (hematoma) group, both femurs were exposed subperiosteally at the midshaft prior to fracture. At one side, the hematoma was evacuated 30 min following fracture, at the other side the hematoma was left undisturbed. In the other (periosteal) group, the femur was exposed subperiosteally at one side, while the periosteum was left intact at the other side. The healing of the fractures was evaluated at 4 weeks. In the hematoma group, no differences were found in callus production, while bending moment and bending rigidity were greater at the side where the hematoma was not removed. No differences were found in fracture energy. In the periosteal group, marginal differences were found in the callus area. Bending moment, bending rigidity and fracture energy were greater at the side where the periosteum was left intact. A comparison of all four limbs, showed that the periosteal sealing was of particular importance for rapid healing.

The importance of the hematoma for fracture healing in rats.

In 3 groups of rats, bilateral femoral fractures were produced. The fracture hematoma was removed on one side after 30 min, 2 days and 4 days in the 3 groups, respectively. The fractures were mechanically tested at 4 weeks. When the fracture hematoma was removed early, callus production, bending moment, and fracture energy were decreased. Removal of the hematoma at Day 2 or 4 impaired fracture healing even more, as both bending moment, bending rigidity and fracture energy were greatly decreased compared to the control fractures. We conclude that the fracture hematoma favors healing; removal of the hematoma after some days is more harmful to healing than when the hematoma is removed in the initial phase.

Bone Fracture Healing using a Capacitatively Coupled Rffield

A new pulsed radio frequency electric field pattern evolved from bone studies was adopted to accelerate fracture healing in rats. The output of a specially designed signal generator was ca-pacitatively coupled to the fracture site using a pair of stainless steel electrodes. In a series of experiments performed on rats, fractures were induced in the femoral shafts and electrical stimulations were applied to one leg. Bone mass formed in the gap was estimated by measurement of the cortical thickness and by ultrasonic attenuation. We found that the stimulated side showed greater bone mass than the contralateral control. We suggest that. this device offers a simple and reliable method of acclerated healing, immediately after fracture.

骨折治癒過程における肥満細胞の動態

Kinetic changes in number and distribution of mast cells during fracture healing in rats were examined.A transverse fracture was made in the tibial shaft of rats (Wistar strain, male, 8w) by the original fracture production apparatus. The fractured leg was left unsplinted. Histological specimens including whole healing callus were obtained at various times after the fracture.Mast cells appeared in the old marrow near the internal callus 2 weeks after the fracture. At about 5 weeks, they appeared in the whole new marrow of the external callus where remodeling is in advance. At this time, degranulated mast cells were dominant. The number of mast cells gradually decreased in parallel with the decrescent bone resorption.These results suggest that mast cells play an important role in bone resorption during remodeling.

Inhibitory effects of tumor necrosis factor alpha on fracture healing in rats

Fracture healing, which involves a cascade of biological tissue responses, may be affected by various biochemical substances. One of these substances is tumor necrosis factor alpha (TNF). Studies were made on the effects of TNF on healing of fractured ribs of rats. Fracture healing was inhibited by daily administration of recombinant human TNF (400 μg/kg body weight per day, intraperitoneally) after fracture. The rate of union on day 20 was significantly lower in the TNF-treated group ( 4 18 , 22.2%) than in the control group ( 14 18 , 77.8%) ( p < 0.001 by Chi-square test). Histological examination showed that TNF inhibited cartilagenous callus formation. On day 10, cartilage was seen in the gap zone and under the periosteum in the control group, but no cartilage formation was observed in the gap zone in 9 of 12 specimens from the TNF-treated group. On day 20, the fracture ends were united by newly formed bone in the control group, but mature fibrous tissue was seen in the gap zone, and bony or cartilagenous union was not achieved in the TNF-treated group. These results show that TNF inhibits cartilage formation in the early phase of bone induction in fracture healing and suggest that this effect of TNF is due to its inhibition of differentiation of mesenchymal cells into chondroblasts.

Biochemical characterization of fracture callus proteoglycans.

The changes in proteoglycan molecules during the initial stages of fracture healing in rats were characterized. Following extraction of callus proteoglycan components with dissociative solvents, the components were purified in a cesium chloride density gradient. The recovered proteoglycans were characterized with respect to their molecular size distribution using gel filtration chromatography and a centrifugal transport methodology. During this early healing period, a decrease was observed in the relative proportion of the aggregate and in the hydrodynamic size and sedimentation coefficients of these molecules. While some molecular degradation could have occurred during the early stages of fracture healing, the dominant change of the proteoglycan molecules seemed to be disaggregation. No significant difference was observed in the proportion of aggregates reformed when exogenous hyaluronate and link glycoproteins were allowed to interact with the two corresponding monomer preparations. The molecular changes of the proteoglycan molecules seem to parallel those occurring during endochondral calcification of rat epiphyseal cartilage.

Mechanical effects of intramedullary acrylic cement on fracture healing in rats.

In one group of rats, the medullary cavity was reamed and bone cement was injected. In a control group, only reaming was performed. A closed fracture was then produced in the middle of the femur. At 40,60 and 90 days following operation the torsional moment, the elastic stiffness, the volume and the density of the callus tissue were evaluated. No differences were found between the two groups. It is concluded that acrylic bone cement in the medullary cavity does not impair the healing of non-immobilized fractures in young rats.

Proteoglycans synthesized in calluses at various stages of fracture healing in rats

The sequential cartilage and bone formation was observed in fracture calluses which were formed at fibula diaphysis of Sprague-Dawley rats. The proteoglycans synthesized in the calluses at different stages during fracture healing were labeled in vitro with [ 35S]sulfate and then analyzed by sucrose density gradient centrifugation. A heavy proteoglycan, in which chondroitin 4-sulfate accounted for approx. 90% of total radioactivity, was predominantly synthesized in addition to light, dermatan sulfate-containing proteoglycans in day-10 and day-20 calluses, when cartilaginous areas were predominant in these calluses. The synthesis of the heavy proteoglycan started around day 7, when chondrogenesis started locally in the callus, and ceased by day 30, when cartilage had been replaced by newly formed bone. The heavy proteoglycan had chemical and physical properties similar to those of the major proteoglycan synthesized by bone matrix-induced cartilages, but different from those of the major one synthesized by the epiphyseal cartilage of neonatal rats. These findings suggest that the sequential molecular transitions observed in fracture healing differ from those in the endochondral ossification of embryonic skeletal tissues but resemble those in bone matrix-induced bone formation.

Fracture Healing in Rats Exposed to Extremely Low-Frequency Electric Fields

Fibular osteotomies in rats were exposed to an extremely low frequency field for 14 days. By histologic evaluation it was found that the healing rate was retarded by the field. The effect (which was replicated) occurred at much lower power levels than are presently employed in electircal osteogenesis.

Effect of exogenous RNA and ultrasound on fracture healing in rats

Effect of exogenous RNA and ultrasound on fracture healing in rats

The effect of hyperbaric oxygen on fracture healing in rats.

The effect of hyperbaric oxygen on fracture healing in rats.

The Effect of Reduced Barometric Pressure on Fracture Healing in Rats

Fracture healing in a series of fractures of the fibula in Fischer rats was studied at a simulated altitude of 18,000 feet in both acclimatized and unacclimatized animals. The acclimatized animals healed their fractures as well as control animals did, but there was significant retardation of fracture healing in the unacclimatized animals, up to thirty and forty days.

Effect of vitamin D2 and fluoride on experimental bone fracture healing in rats.

Effect of vitamin D2 and fluoride on experimental bone fracture healing in rats.

Fracture Healing in Rats Treated with Aminoacetonitrile

Aminoacetonitrile administered to adult rats with experimental fractures induced the formation of a voluminous fibrocartilaginous callus which ossified well during the second week of fracture. This callus became very osteoporotic during the third week, and bone union usually did not occur. When aminoacetonitrile was administered only during the first week after fracture, callus slightly larger than that in the control animals developed with speedier bone union. In rats treated with l-triiodothyronine alone, fracture callus, apparently similar to that of the controls, developed. When l-triiodothyronine was administered simultaneously with aminoacetonitrile, fracture callus, smaller and better ossified than that in animals treated with amioacetonitrile alone, formed.