In vivo endochondral bone formation using a bone morphogenetic protein 2 adenoviral vector.

Bone morphogenetic proteins (BMPs) are polypeptides that induce ectopic bone formation in standard rat in vivo assay systems. Previous studies have demonstrated the clinical utility of these proteins in spinal fusion, fracture healing, and prosthetic joint stabilization. Gene therapy is also a theoretically attractive technique to express BMPs clinically, since long-term, regulatable gene expression and systemic delivery with tissue-specific expression may be possible in future. This study was performed to determine whether an adenoviral vector containing the BMP-2 gene can be used to express BMP-2 in vitro and promote endochondral bone formation in vivo. In vitro, U87 MG cells transduced per cell with 20 MOI of an adenoviral construct containing the BMP-2 gene under the control of the universal CMV promoter (Ad-BMP-2) showed positive antibody staining for the BMP-2 protein at posttransfection day 2. The synthesis and secretion of active BMP-2 into the conditioned medium of Ad-BMP-2-transduced 293 cells were confirmed by Western blot analysis and the induction of alkaline phosphatase activity in a W-20 stromal cell assay. In vivo, Sprague-Dawley rats and athymic nude rats were injected with Ad-BMP-2 in the thigh musculature and were sacrificed on day 3, 6, 9, 12, 16, 21, 60, and 110 for histological analysis. The Sprague-Dawley rats showed evidence of acute inflammation, without ectopic bone formation, at the injection sites. In the athymic nude rats, BMP-2 gene therapy induced mesenchymal stem cell chemotaxis and proliferation, with subsequent differentiation to chondrocytes. The chondrocytes secreted a cartilaginous matrix, which then mineralized and was replaced by mature bone. This study demonstrates that a BMP-2 adenoviral vector can be utilized to produce BMP-2 by striated muscle cells in athymic nude rats, leading to endochondral bone formation. However, in immunocompetent animals the endochondral response is attenuated, secondary to the massive immune response elicited by the first-generation adenoviral construct.

Morphologic analysis of BMP-9 gene therapy-induced osteogenesis.

The present study was performed to determine the histological, ultrastructural, and radiographic changes that occur over time at intramuscular BMP-9 gene therapy treatment sites. Several members of the bone morphogenetic protein (BMP) family have the potential to induce osteochondrogenesis when the protein is delivered to rodents, canines, rabbits, and nonhuman primates. Previous studies have also demonstrated that BMP gene therapy utilizing adenoviral vectors can also stimulate orthotopic and heterotopic bone formation in rodents and rabbits. Athymic nude and Sprague-Dawley rats were injected with Ad-BMP-9 or Ad-beta-Gal (3.75 x 10(9) particles) in their thigh musculature and light microscopic, electron microscopic, and computerized tomography analysis was performed 3, 6, 9, 12, 15, 18, 21, and 100 days later. To assess early mesenchymal cell proliferation, a bromodeoxyuridine (BrdU) immunohistochemical analysis was also performed 48, 60, and 72 hr postinjection in athymic nude rats. All animals demonstrated extensive endochondral bone formation at the Ad-BMP-9 treatment sites within 3 weeks. The Sprague-Dawley rats also exhibited a massive, acute inflammatory infiltrate during the first week. Proliferating mesenchymal stem cells were clearly evident as early as 2 days after treatment, which differentiated into small or hypertrophied chondrocytes during the next week. During the third week, the cartilaginous matrix mineralized and formed woven bone, which converted to lamellar bone by 3 months. No evidence of bone formation was demonstrated at the Ad-beta-Gal injection sites in the athymic nude or Sprague-Dawley rats. In addition, no cellular proliferation was seen at the Ad-beta-Gal treatment sites in the athymic nude animals as assessed by light microscopy and BrdU immunohistochemistry. The extensive bone formation induced by Ad-BMP-9 suggests that BMP gene therapy may have potential utility in the treatment of degenerative, rheumatic, or traumatic bone pathology.

Choline acetyltransferase- and substance P-like immunoreactive elements in fetal striatal grafts in the rat: a correlated light and electron microscopic study.

Fetal striatal neurons were transplanted into the ibotenic acid-lesioned rat striatum. Three months after transplantation, the graft tissue was processed for choline acetyltransferase- and substance P-like immunoreactivity and was subsequently examined at the light and electron microscopic levels. The study demonstrated that choline acetyltransferase- and substance P-like-immunoreactive neurons were homogenously present throughout fetal striatal grafts, although in decreased numbers compared with those in the normal rat striatum. The majority of the choline acetyltransferase-immunoreactive neurons had fusiform, oval, or polygonal somata with somatic diameters greater than 20 microns and contained deeply invaginated nuclei surrounded by copious cytoplasm. In addition, choline acetyltransferase-immunoreactive neurons with somatic diameters between 10 and 20 microns were also demonstrated. The grafts' substance P-like-immunoreactive neurons, which had somatic diameters between 10 and 25 microns and had oval or polygonal perikarya, could be classified into two types based on their ultrastructural characteristics. Type I neurons contained an unindented nucleus which was surrounded by a thin rim or moderate amount of cytoplasm, whereas Type II immunoreactive neurons contained an indented nucleus which was surrounded by copious cytoplasm. Choline acetyltransferase- and substance P-like-immunoreactive dendrites in the grafts' neuropil were contacted by multiple unlabeled axon terminals. In addition, choline acetyltransferase- and substance P-like-immunoreactive axon terminals forming symmetric contacts with unlabeled dendrites were present within the graft. The study demonstrated that many of the neuroanatomical features of choline acetyltransferase- and substance P-like-immunoreactive elements found in the normal rat striatum are present in mature fetal striatal grafts.

Fetal neostriatal transplants in the rat: a light and electron microscopic Golgi study.

Fetal striatal neurons were transplanted into the ibotenic acid lesioned rat striatum. Three months after transplantation the grafted tissue was Golgi-impregnated and examined at the light microscopic level to determine the morphological characteristics of the transplanted neurons. Golgi-impregnated neurons were then gold-toned and examined at the electron microscopic level. The transplanted neurons were classified by both somatic size and somatic and dendritic morphology, which demonstrated that at least seven distinct cell types are present in striatal grafts. Type I large neurons had aspinous somata, sparsely spined dendrites, and indented nuclei, whereas type II large neurons displayed somatic spines, sparsely spined dendrites, and indented nuclei. Type I medium neurons exhibited aspinous somata and proximal dendrites, heavily spined distal dendrites, and unindented nuclei. Type II medium neurons had somatic spines, sparsely spined dendrites, and indented nuclei. Type III medium neurons had aspinous somata, poorly branched and sparsely spined dendrites, and indented nuclei, while type IV medium neurons had aspinous somata, highly branched and sparsely spined dendrites, and indented nuclei. Type V medium neurons displayed aspinous somata, varicose dendrites, and indented nuclei. These results demonstrate that transplanted fetal striatal neurons differentiate into morphologically and ultrastructurally distinct striatal cell types.

Descriptive morphology of developing fetal neostriatal allografts in the rhesus monkey: a correlated light and electron microscopic Golgi study.

Primate fetal striatal neurons were transplanted into the ibotenic acid lesioned rhesus monkey striatum. Ten weeks after transplantation the monkeys were transcardially perfused and graft tissue was histologically stained. Golgi impregnated, and processed for electron microscopy. The monkeys received magnetic resonance imaging (MRI) scans before lesioning, after lesioning, and ten weeks after transplantation to noninvasively study the striatal grafts. The study demonstrated that fetal striatal grafts, measuring up to 0.4 x 0.8 cm, can survive for extended periods of time in the non-human primate. Hematoxylin-eosin stained sections of the transplant demonstrated that neuronal, glial, vascular, and lymphocytic cells were present in the graft. The majority of the neurons had somatic diameters between 8 and 20 microns and were characterized by nuclei containing multiple nucleoli. A few neurons within the graft had somatic diameters up to 40 microns. These larger neurons exhibited more mature cytoplasm containing a moderate amount of Nissl substance. Some of the blood vessels within the graft were surrounded by a large number of plasma cells, but there was no evidence of hemorrhage or necrosis. Bielschowsky staining and Golgi impregnation of the transplanted tissue demonstrated that there were neurons at various degrees of differentiation. Some of the neurons had varicose dendrites, growth cones, and filopodia, which are all characteristics of immature neurons, while others had a much more mature appearance, including a moderate number of dendritic spines. Some of these neurons had an appearance typical of differentiating "medium spiny" neurons of the normal striatum. Electron microscopic analysis of the transplanted tissue and individual Golgi-impregnated neurons within the transplant confirmed that there were developing neurons within the graft. These neurons had an increased nuclear-to-cytoplasmic ratio and had nuclei containing multiple nucleoli. The neuropil surrounding these neurons was loosely organized and contained large areas of extracellular space. The neuropil exhibited developing dendrites, numerous growth cones, and mature synapses. In summary, the study demonstrated that fetal striatal allografts can survive for up to three months in the rhesus monkey and undergo normal differentiation as assessed by Golgi impregnation and electron microscopy.

In vitro and in vivo transplantation of fetal rat brain cells following incubation with various anatomic tracing substances.

Implantation of fetal brain regional anlage into host brains ('brain transplantation') holds promise as a plausible treatment for certain human neurodegenerative disorders. Improvements in experimental brain transplantation techniques include: (1) utilization of brain cells in tissue culture as opposed to freshly prepared cell suspensions as a transplantation source, (2) prelabeling of fetal brain cells with inert, non-toxic tracer substances to allow subsequent (a) unequivocal identification of those cells as being fetally derived, and (b) anatomical and immunohistochemical identification of transplanted neurons, and (3) development of in vitro models for transplantation to allow physiological studies of connections formed between fetal neurons and host brain tissue. We examined the ability of brain cell suspensions derived from rat fetuses 15-17 gestational days old to accumulate and retain anatomic tracing substances, including Phaseolus vulgaris leucoagglutinin (PHA-L), rhodamine-labeled latex microspheres (RLM) and fluorogold (FG). All tracers were rapidly accumulated by fetal brain cells, but only PHA-L and RLM were retained following implantation into adult hosts or in tissue culture in vitro. PHA-L-labeled fetal brain cells transplanted in vivo showed morphological characteristics similar to fetal neurons kept in tissue culture in vitro. RLM- or PHA-L-labeled fetal brain cells can be co-cultured with rat brain slices maintained in long-term roller culture. This in vitro system will allow identification and physiological or immunohistochemical study of interactions between fetally derived and host brain neurons.

A method for utilizing biocytin to study retinofugal pathways at the light and electron microscopic levels.

Numerous methods have been utilized in the past to study the retinofugal pathway at both the light and electron microscopic levels. However, many of these techniques have technical drawbacks that make them difficult to use in electron microscopic studies. We present herein a method for utilizing the anterograde tracer biocytin to study the retinal pathways at both the light and electron microscopic levels. Biocytin is an especially useful tracer since it clearly labels very small axons and boutons in addition to the larger fibers. In addition, the synaptic ultrastructure is left intact and the technique can be utilized in numerous double-labeling neuroanatomical studies.

A horseradish peroxidase-light and electron microscopic study of immunoliposomes utilized for intracellular delivery to the rat striatum.

Liposomes can deliver plasmid DNA, viruses, antisense oligonucleotides, and pharmacological agents to the central nervous system. Conjugation of antibodies to liposomes increases delivery specificity. Immunoliposomes created with Thy 1.1 antibody have previously been shown to be effective for neuronal delivery. The intracellular delivery of these immunoliposomes is evaluated by light and electron microscopy. Thy 1.1 conjugated liposomes were loaded with horseradish peroxidase and stereotactically injected into rat striatum. On light microscopy, immunoliposomes were concentrated within 0.2 mm of the injection site 8 h following delivery but, 24 h post-operatively, had diffused more than 0.5 mm from the injection site. With transmission electron microscopy, immunoliposomes were observed entering numerous neurons and some astrocytes in a process distinct from the clathrin-coated pit mechanism. These findings suggest that Thy 1.1 immunoliposomes are effective for intracellular delivery in vivo and their endocytosis occurs independently of a coated pit process. The research has helped to elucidate alternative mechanisms for immunoliposomal delivery. A more fundamental understanding of these attributes is needed to achieve the therapeutic potential of immunoliposomes.

Elastase-induced saccular aneurysms in rabbits: comparison of geometric features with those of human aneurysms.

BACKGROUND AND PURPOSE: The development of more effective intracranial aneurysm therapy depends on the ability to test various intravascular occlusion devices and techniques in preclinical animal models. This requires the creation of experimental aneurysms, which, ideally, should mimic the size and geometric features of human intracranial aneurysms. The purpose of this study was to characterize the morphologic features of elastase-induced saccular aneurysms in rabbits to determine whether the morphology of such aneurysms mimics that of human intracranial aneurysms. METHODS: Elastase-induced saccular aneurysms were created in 40 New Zealand white rabbits. Intravenous digital subtraction angiography was performed 14 days after surgery. Relative to an external sizing device, the following dimensions were determined: aneurysm dome (height and width), aneurysm neck diameter, and parent artery diameter. Based on maximal diameter, aneurysms were categorized as small (2.0-4.9 mm), medium-sized (5.0-9.9 mm), or large (10-16 mm), and as narrow-necked (<4.0 mm neck width) or wide-necked (>4.0 mm neck width). Mean dome-neck ratio was calculated and compared with that of human aneurysms. RESULTS: All aneurysm cavities were angiographically patent. Widths of the cavities ranged from 2.5 to 7.1 mm (mean, 4.1 +/- 1.2 mm); heights ranged from 3.0 to 15.6 mm (mean, 8.8 +/- 2.6 mm). Three (7.5%) of 40 aneurysms were small, 20 (50%) were medium-sized, and 17 (42.5%) were large. Twenty-two (55%) of 40 aneurysms were small-necked, and 18 (45%) were wide-necked. Mean dome-neck ratio was 1.13 +/- 0.54. Mean parent artery diameter was 4.3 +/- 1.4 mm. CONCLUSION: Saccular aneurysms of sizes similar to that of human intracranial aneurysms were reliably created using a simple method of vessel ligation and elastase injury. Neck sizes varied with both large and small-necked aneurysms created.

Endovascular treatment of experimental aneurysms by use of biologically modified embolic devices: coil-mediated intraaneurysmal delivery of fibroblast tissue allografts.

BACKGROUND AND PURPOSE: Our long-term goal is to improve intraaneurysmal fibrosis after aneurysm embolization, by implanting exogenous fibroblasts, using platinum coils. For the current project, we tested two hypotheses: 1) that exogenous, fluorescence-labeled rabbit fibroblast allografts remained viable and proliferated within rabbit carotid arteries, and 2) that these fibroblast allografts could be reliably implanted into experimental aneurysms by use of platinum coils. METHODS: Part 1. New Zealand White rabbit synovial fibroblasts obtained from a commercial vender were labeled with a fluorescent membrane marker. The common carotid arteries of New Zealand White rabbits were surgically exposed, ligated proximally and distally, and entered with 22-g angiocatheters. Through the angiocatheter we injected either phosphate-buffered saline-containing fluorescence-labeled fibroblasts (treatment vessels) or saline only (control vessels). The wounds were closed, and the subjects were kept alive for various time points up to 2 weeks. After sacrifice, the carotid artery segments were resected, processed for frozen-section histologic examination, and evaluated using epifluorescent microscopy and hematoxylin and eosin staining. Cell viability and proliferation were determined by comparing the treatment versus control vessels. Part 2. A) Fluorescence-labeled cells were grown in culture on platinum coils, which were then exposed to systemic arterial flow in the rabbit thoracic aorta for various lengths of time up to 40 minutes. The coil segments were then examined using fluorescent microscopy and the presence and relative amount of cells remaining on the coil were documented. B) Experimental aneurysms in rabbits were embolized with control platinum coils (n = 9) and platinum coils bearing rabbit synovial fibroblasts that were grown onto the coils in culture prior to implantation (n = 9). Subjects were sacrificed 3, 7, and 14 days after coil implantation. Histologic samples were studied to assess the presence or absence of nucleated cells within and around coil winds in order to determine whether fibroblasts had been successfully implanted into aneurysms. Data were evaluated using the chi-square test for statistical significance. RESULTS: Part 1. Fluorescence-labeled cells were examined in the treatment carotid artery segments and results were recorded at all time intervals. The treatment vessel segments showed evidence of progressive cellular proliferation, leading to complete vessel fibrosis at 2 weeks. Conversely, control vessel segments were filled predominately with unorganized thrombus at each time interval. Part 2. A) Numerous labeled fibroblasts remained adherent to the coil despite prolonged exposure to systemic arterial flow. B) Fibroblasts were seen adjacent to or within the central lumen of coils in eight (88%) of nine aneurysms treated with cell-bearing coils. Nucleated cells were not present in any of the nine control coil subjects. This represented a statistically significant difference (P < .001). CONCLUSION: Fibroblast allografts remain viable and proliferate in the vascular space in rabbits. Furthermore, these same fibroblasts, after seeding onto platinum coils in culture, remain protected within the lumen of the coils and are retained within the coil lumen even after prolonged exposure to arterial blood flow. Coils can be used to deliver viable fibroblasts directly into experimental aneurysms successfully. These findings indicate that coil-mediated cell implantation is feasible and may be a potential method of increasing the biological activity of embolic coils.

The accessory optic system in the frog, Rana Pipiens: an electron microscopic study of the retinal afferents utilizing the anterograde tracer biocytin.

The retinal afferents to the basal optic nucleus in the frog, Rana Pipiens, were labeled anterogradely with biocytin and subsequently studied at the electron microscopic level. Labeled synaptic terminals in the nucleus varied in size from 0.5 microns to 2.0 microns and made symmetric synaptic contacts with large and small dendrites, although very rare axospinous and axosomatic contacts were also demonstrated.

Bone morphogenetic proteins and bone morphogenetic protein gene therapy in neurological surgery: a review.

OBJECTIVE: To review the uses of bone morphogenetic proteins (BMPs) and BMP gene therapy for the treatment of neurosurgical disorders. METHODS: Literature review. RESULTS: BMPs are members of the transforming growth factor beta superfamily, and they play an important role in the growth and development of numerous tissues, including bone, brain, and spinal cord. Although the majority of previous studies have focused on the regulatory functions of BMPs in the normal growth and differentiation of the skeletal system, BMPs also seem to be exquisitely involved in the regulation of cellular proliferation, survival, differentiation, apoptosis, and lineage commitment in the central nervous system. When specific BMPs are delivered on biological matrices, they have the capacity to induce bone, cartilage, ligament, and tendon at both heterotopic and orthotopic sites, suggesting that they may play a major role in the future treatment of spinal and craniofacial pathology. For example, recent studies have clearly demonstrated the usefulness of BMPs and BMP gene therapy for the induction of spinal arthrodesis in several animal models. In addition, several BMPs have been shown to have a neuroprotective effect in animal models of head injury, cerebral ischemia, and Parkinson's disease and may therefore have direct clinical applications for the treatment of central nervous system disorders. CONCLUSION: As the physiological activity of BMPs in the development and pathology of the central nervous system and spine are more fully elucidated, BMP therapeutics and gene therapy will probably have numerous applications in neurological surgery.

Partial pediculectomy in the treatment of lumbar spinal stenosis: technical note.

OBJECTIVE: We note an additional pathological condition associated with lumbar spinal stenosis that may be responsible for significant postoperative pain. Recognizing that nerve roots are stretched around hypertrophic pedicles in some cases of spinal stenosis, we have altered our surgical management of these cases to address what may be a previously unrecognized but significant anatomic pathological finding. SURGICAL TECHNIQUE: After ipsilateral posterior bony decompression of the spinal canal, the nerve root is examined as it courses around the pedicle. If the root appears stretched, the medial part of the pedicle is removed using first a diamond bit and then a curet. The nerve root is retracted and protected during this procedure. RESULTS: Inspection of the root after partial pediculectomy frequently reveals lateral movement of the root into space previously occupied by the pedicle. Anatomically, the nerve is better decompressed and free of obstruction. This technique adds little time to the overall duration of the operation. CONCLUSION: Anatomic evidence obtained through intraoperative examination and preoperative imaging techniques indicates that partial pediculectomy may play a role in the treatment of some cases of lumbar stenosis.

Systemic administration of the endothelin-A receptor antagonist TBC 11251 attenuates cerebral vasospasm after experimental subarachnoid hemorrhage: dose study and review of endothelin-based therapies in the literature on cerebral vasospasm.

OBJECTIVE: Increasing evidence implicates endothelin (ET)-1 in the pathophysiological development of cerebral vasospasm. This study examined the ability of TBC 11251 (TBC), a new ETA receptor antagonist, to prevent vasospasm in a rabbit model of subarachnoid hemorrhage (SAH). METHODS: Eighty-five New Zealand White rabbits were assigned to 1 of 10 groups. SAH was induced by injecting autologous blood into the cisterna magna. The treatment groups were as follows: 1) control (no SAH), 2) SAH alone, 3) SAH plus vehicle every 12 hours (BID), 4) SAH plus 5 mg/kg TBC BID, 5) SAH plus 10 mg/kg TBC BID, 6) SAH plus 20 mg/kg TBC BID, 7) SAH plus vehicle at 24 and 36 hours after SAH (24/36), 8) SAH plus 5 mg/kg TBC 24/36, 9) SAH plus 10 mg/kg TBC 24/36, and 10) SAH plus 20 mg/kg TBC 24/36. Animals were killed 48 hours after SAH, by perfusion-fixation, and then basilar arteries were histologically prepared and their cross-sectional areas were measured. RESULTS: The mean basilar artery cross-sectional area was constricted from 0.332 mm2 in the control group to 0.131 mm2 in the SAH alone group, 0.132 in the vehicle 24/36 group, and 0.125 in the vehicle BID group. All groups treated with TBC showed an increase in cross-sectional luminal basilar artery area, relative to the vehicle-treated groups. The 5 mg/kg TBC BID group exhibited a mean basilar artery area of 0.217 mm2, and the 10 mg/kg TBC BID group showed a mean basilar artery area of 0.240 mm2; both groups were statistically improved, compared with the vehicle-treated groups (P < 0.05). No side effects were seen, and there were no differences in the mean arterial pressures between drug- and vehicle-treated groups. CONCLUSION: These findings demonstrate that systemic administration of the ETA receptor antagonist TBC significantly attenuates cerebral vasospasm after SAH, thus providing additional support for the role of ET-1 in vasospasm.

Transforming growth factor beta-coated platinum coils for endovascular treatment of aneurysms: an animal study.

OBJECTIVE: To test the hypothesis that coating platinum coils with transforming growth factor beta (TGFbeta) would improve the cellular proliferation within experimental aneurysms relative to uncoated coils. MATERIALS AND METHODS: Elastase-induced saccular aneurysms were created in 12 New Zealand White rabbits. These aneurysms were embolized with platinum coils, either "control" (unmodified) coils or "test" (coated with TGFbeta) coils. Subjects were killed either 2 weeks (n = 3, control; n = 3, test) or 6 weeks (n = 3, control; n = 3, test) after embolization. Aneurysm tissue was embedded in plastic, sectioned, and stained with hematoxylin and eosin. The thickness of tissue covering the coils at the coil-lumen interface was measured by use of a digital microscope, and was compared between groups by use of the Student's t test (P < or = 0.05). RESULTS: Two-week implantation samples demonstrated mean thickness of tissue overlying TGFbeta-coated coils of 36+/-15 microm and mean thickness of overlying control coils of 3+/-5 microm, indicating significantly thicker tissue growth covering test versus control coils (P = 0.02). Six-week implantation samples demonstrated mean thickness of tissue overlying TGFbeta-coated coils of 86+/-74 microm versus mean thickness overlying control coils of 37+/-6 mu; this difference did not reach statistical significance (P = 0.30). Thickness of tissue covering TGFbeta-coated coils did not change significantly from 2 to 6 weeks (P = 0.31). Tissue thickness over control coils increased significantly between 2 and 6 weeks (P = 0.002). CONCLUSION: TGFbeta-coated platinum coils undergo earlier cellular coverage than standard platinum coils, but differences in coverage between coated and control coils are no longer present at later time points. These data suggest that improvements in intra-aneurysmal cellular proliferation resulting from coil modifications, although significant in the early postembolization phase, may dissipate over time.

Routine angiography after surgery for ruptured intracranial aneurysms: a cost versus benefit analysis.

PURPOSE: To assess the cost versus the benefit of routine cerebral angiography after surgery for ruptured aneurysms. METHODS: Decision tree and Markov analyses that used cohort simulation were conducted to determine the incremental cost:benefit ratio of routine postsurgical angiography. Input data for unexpected partially clipped and unclipped cerebral aneurysms were estimated from the literature for the following variables: frequency; annual rate of subsequent hemorrhage; morbidity and mortality rates of subsequent hemorrhage; efficacy and morbidity and mortality rates of subsequent surgery; and costs of subsequent surgery, angiography, subsequent hemorrhage of aneurysm, and rehabilitation. RESULTS; Baseline input variables resulted in an acceptable cost:benefit ratio for routine postsurgical angiography. However, essentially all of the benefit was derived from intervening in cases of unexpected unclipped aneurysms rather than partially clipped aneurysms. Isolated instances of angiography and subsequent surgery for unexpected partially clipped aneurysms yielded unacceptable cost:benefit ratios. Surgical costs had minimal effect on the analysis. CONCLUSIONS: When routine postsurgical angiography was performed primarily to diagnose and to subsequently operate on unexpected partially clipped aneurysms, the cost:benefit ratio was unacceptable. However, even low frequencies of unexpected unclipped aneurysms resulted in favorable cost:benefit ratios.

Molecular methods of enhancing lumbar spine fusion.

OBJECTIVE: An optimal method for spinal fusion would induce rapid growth of bone via an osteoconductive and osteoinductive implant. This study examines the spinal fusion enhancement potential of some osteoconductive and osteoinductive biomaterials. METHODS: Four similar canines received unilateral posterolateral fusions on the left side at T13-L1 and L4-L5 and on the right side at L2-L3 and L6-L7. The experiments were grouped as follows: Group A, autogenous bone harvested from the iliac crest; Group B, autogenous bone and collagen; Group C, no implant; and Group D, autogenous bone, collagen, and recombinant human bone morphogenetic protein-2. Radiographic assessment, three-dimensional computed tomographic volumetric analysis, and biomechanical testing were performed at each level. RESULTS: For Groups A and B, the fusions demonstrated moderate bone formation at 6 and 12 weeks postoperatively. Group D fusions exhibited earlier and more dramatic increases in volume and radiodensity and eventually were comparable in size to the vertebral bodies. Average fusion volumes computed from three-dimensional computed tomographic analysis were: Group A = 1.243 cc, Group B = 0.900 cc, Group C = 0.000 cc, and Group D = 6.668 cc (P = 0.003 compared to Group A). Group D exhibited flexion and extension biomechanical properties much greater than controls. The addition of recombinant human bone morphogenetic protein-2 consistently yielded the strongest fused segments and, on average, enhanced extension stiffness by 626% and flexion stiffness by 1120% over controls. CONCLUSION: The most advantageous spinal fusion implant matrix consisted of recombinant human bone morphogenetic protein-2, autogenous bone, and collagen. Future investigators, however, need to examine the appropriate quantities of the individual components and clarify the efficacy of the matrix for the various types of spinal fusion approaches.

Carotid artery revascularization following Crutchfield clamp placement. Report of two cases.

Several types of adjustable clamp have been widely utilized to gradually occlude the carotid artery for the treatment of various intracranial vascular lesions. A fairly large number of patients, many of whom have not been adequately followed, have these clamps still in place. The authors report two patients, initially treated with a Crutchfield clamp for an intracranial aneurysm, in whom carotid artery system revascularization occurred through the clamp many years later, leading to continued filling of the aneurysm. Recommendations are given on monitoring patients with Crutchfield clamps in order to minimize long-term complications.

Percutaneous spinal fusion using bone morphogenetic protein-2 gene therapy.

OBJECT: Gene therapy has many potential applications in neurosurgery. One application involves bone morphogenetic protein-2 (BMP-2), a low-molecular-weight glycoprotein that induces bone formation in vivo. Numerous studies have demonstrated that the BMP-2 protein can enhance spinal fusion. This study was undertaken to determine whether direct injection of an adenoviral construct containing the BMP-2 gene can be used for spinal fusion. METHODS: Twelve athymic nude rats were used in this study. Recombinant, replication-defective type 5 adenovirus with the cytomegalovirus (CMV) promoter and BMP-2 gene (Ad-BMP-2) was used. A second adenovirus constructed with the CMV promoter and beta-galactosidase (beta-gal) gene (Ad-beta-gal) was used as a control. In three groups (four rats each) 7.5 microl of virus (5x10(8) particles/microl) was injected percutaneously and paraspinally at the lumbosacral junction: Group 1 received Ad-BMP-2 bilaterally; Group 2 received Ad-BMP-2 on the right, Ad-beta-gal on the left; and Group 3 received Ad-beta-gal bilaterally. Computerized tomography (CT) scans of the lumbosacral spine were obtained at 3, 5, 8, and 12 weeks. At 12 weeks, the animals were killed and underwent histological inspection. Ectopic bone formation was observed both on three-dimensionally reconstructed CT scans and histological examination in all rats at sites treated with Ad-BMP-2. Histological analysis demonstrated bone at different stages of maturity adjacent to the spinous processes, laminae, and transverse processes. CONCLUSIONS: Results of this study clearly demonstrated that it is possible to produce in vivo endochondral bone formation by using direct adenoviral construct injection into the paraspinal musculature, which suggests that gene therapy may be useful for spinal fusion in the future.

Use of bone morphogenetic protein-9 gene therapy to induce spinal arthrodesis in the rodent.

OBJECT: Bone morphogenetic proteins (BMPs) have been shown to have significant osteoinductive activity in numerous in vitro and in vivo assay systems, and BMP-2 and BMP-7 are currently being evaluated in human clinical studies. In the spinal region, BMPs have been shown to promote spinal arthrodesis at a higher rate than autologous bone alone. The delivery of BMPs via direct or ex vivo gene therapy techniques is also currently being evaluated and has shown promise in several mammalian models. The present study was designed to evaluate the efficacy of the use of direct, percutaneous BMP-9 adenoviral gene therapy to promote spinal fusion in the rodent. METHODS: Each animal was injected with 7.5x10(8) pfu of a BMP-9 adenoviral vector in the lumbar paraspinal musculature and allowed to survive 16 weeks. Computerized tomography studies and histological analysis demonstrated massive bone induction at the injection sites, clearly leading to solid spinal arthrodesis, without evidence of pseudarthroses, nerve root compression, or systemic side effects. CONCLUSIONS: The results of this study strongly support the advancement of BMP gene therapy techniques toward clinical use.