Bone grafts cultured with bone marrow stromal cells for the repair of critical bone defects: an experimental study in mice

Tissue engineering of autologous bone combined with osteoprogenitor cells is a suitable strategy for filling large bone defects. The aim of this study was to evaluate the osteogenicity of a xenogenic bone graft cultured with allogenic bone marrow stromal cells (BMSC) in a mouse critical size craniotomy. Bovine trabecular bone grafts were made free of bone marrow cells or debris and were delipidated. BMSC were harvested from C57BL/6-Tg(ACTbEGFP)1Osb/J mice (GFP+ cells) and were cultured 14 days on bone grafts in control or osteogenic medium. Engineered grafts were implanted in calvarial defect in C57BL/6 mice. Four groups were studied: graft with BMSC differentiated in osteoblasts (G-Ob), graft with BMSC (G-BMSC), graft without cells (G) and no graft. Calvariae were studied 2 and 8 weeks after implantation by radiographic and histomorphometric analyses. G group: the bone ingrowth was limited to the edges of the defect. The center of the graft was filled by a fibrovascular connective tissue. G-BMSC or G-Ob groups: bone formation occurred early in the center of the defect and did not increase between 2 and 8 weeks; the newly formed woven bone was partially replaced by lamellar bone. The preoperative osteoblastic differentiation of BMSC did not allow faster and better bone regeneration. After 2 weeks, GFP+ cells were observed around the grafted bone but no GFP+ osteocyte was present in the newly formed bone. No GFP+ cell was noted after 8 weeks. However, pre-implantation culture of the biomaterial with allogenic BMSC greatly enhanced the bone regeneration.     

Assessment of the effect of a biphasic ceramic on bone response in a rat calvarial defect model

Calcium phosphate ceramics are being extensively used for orthopedic, periodontal, and dental applications. This study aimed to assess the effect of a biphasic ceramic such as Ceraform on the osteogenesis in a rat calvarial defect model. 20 Wistar rats were enrolled in the study. Two symmetrical, circular, and 5-mm-wide full thickness defects were created in the parietal bones of each animal. The left defect was left empty as a control and the right defect was filled with the particular implant material. Animals were divided into two groups, and 10 animals were sacrificed at month 3 and the rest were sacrificed at month 6. The calvarial specimens were harvested for histological examinations. Defect area samples were stained with hematoxylin-eosin and Masson Thrichrom. A semiquantitative method was used to quantify the bone regeneration. The defects were mostly filled with fibrous connective tissue (3-6 months) in the control site. A loose, fibrovascular tissue was observed at the side of ceraform implantation at month 3. By 6 month, a dense collagenous tissue was observed at the same area. Multinuclear giant cells (MNGC) were detected around the implant bed at month 3 and month 6. No necrosis, tumorigenesis, or infection was observed at the implantation site at any time. There was no statistically meaningful difference regarding bone regeneration between the two defects at each observation period (p>0.05). This study showed that Ceraform is biocompatible. However, this study indicates that biphasic ceramic do not offer any advantage over hydroxyapatite ceramics. It was also revealed that it had no effects on bone regeneration and that it seemed to be a space maintainer.     

Spinal cord grafts in oculo: survival,growth, histological organization and electrophysiological characteristics

Summary Fetal spinal cord tissue was grafted to the anterior chamber of the eye of adult recipients. Transverse segments from the cervical and high thoracic levels were divided in halves which were grafted directly or further divided into ventral horn and dorsal horn parts before grafting. Survival and intraocular growth was monitored through the cornea. Grafts from E14 to E16 grew to final sizes several times the initial size. The final size of E17 grafts was approximately similar to the initial size, while the final size of E18 and E19 grafts was considerably smaller than the size at grafting. All grafts were well vascularized from the host iris. Grafts from younger donors contained several neurons typical of spinal cord including alpha-motoneuron-type cells. Cells were found in clusters in gray matter areas surrounded by white matter. Extracellular recording revealed many spontaneously active cells. Several had high sustained discharge (10–25 Hz) and large amplitudes. Many cells could be excited by stimulation of the graft surface via activation of local afferents. It is concluded that the capacity of fetal spinal cord tissue to survive grafting to the eye chamber is inversely related to the donor age. Before E17, large grafts retaining several morphological and electrophysiological characteristics of spinal cord are obtained. The intraocular spinal cord graft provides a useful model for studies of spinal cord development and, using co-grafting techniques, a model for spinal cord regeneration and functional connectivity.     

兔股骨髁临界性骨缺损动物模型制备及临界骨缺损值

文题释义：临界性骨缺损：首先定义为自然状况下骨缺损不进行任何处理无法自愈的最短的骨缺损尺寸。随后考虑到观察实验动物完整的生命周期是非常困难的,将临界性骨缺损值定义为在实验期间物种不能自行愈合的最短骨缺损尺寸。 动物模型：是在医学研究中建立的模拟人类疾病表现的动物,骨组织工程中建立临床相关的测试动物模型来研究材料的生物相容性、降解、力学性能以及与宿主组织的相互作用,是体外实验和人体临床试验之间的关键一步。 背景：兔股骨远端骨缺损模型被研究者们广泛用于骨缺损替代骨组织工程材料的测试,但对于兔股骨髁圆柱形骨缺损模型的大小文献报道不一,直径分布在5-9 mm,深度8-12 mm,目前尚无统一的标准。 目的：建立兔股骨髁不同尺寸骨缺损模型,确定兔股骨髁临界性骨缺损尺寸。 方法：6月龄雄性新西兰白兔18只,随机分为3组,每组各6只,分别建立骨缺损模型,骨缺损直径依次为5,6,7 mm,深度均为10 mm,双侧手术,共计12侧。分别于术后第1天及术后第4,8,12周行CT扫描及三维重建,CT-Hedberg评分评价骨缺损愈合情况;于术后12周处死新西兰白兔,取出股骨髁缺损样本,通过大体观察和苏木精-伊红染色分析缺损区愈合情况。实验方案经徐州医科大学实验动物道德伦理委员会批准。 结果与结论：①术后所有兔均存活,术后12周大体观察示：直径5 mm组缺损由新生骨组织充填,股骨髁塑形良好,骨缺损基本完全修复;直径6 mm组、直径7 mm组骨缺损区可见明显凹陷,新生骨组织较少,骨缺损未修复;②CT图像示：术后第4,8周,直径5 mm组缺损区逐渐减小,断端桥接;直径6 mm、直径7 mm组缺损区仅周边有少量新生骨长入,缺损面积较前稍减小;术后第12周可见直径5 mm组皮质骨结构完整、连续,骨缺损基本完全修复;直径6 mm组骨缺损部分修复;直径7 mm组缺损未修复,仍可见明显缺损空腔存在;③CT-Hedberg评分显示,术后各时间点直径6 mm组评分显著低于直径5 mm组(P < 0.05);与直径7 mm组比较差异无显著性意义(P > 0.05);④组织学结果示：术后12周直径5 mm组缺损区出现排列不规则的骨小梁结构,并可见大量新生骨组织填充,其他2组在骨缺损周边可见部分新生骨小梁存在,但缺损区新生骨组织填充较少;⑤结果说明,在12周的实验观察期内,在缺损深度同为10 mm的条件下,直径>6 mm的股骨髁缺损未能自行愈合,而直径<6 mm的股骨髁缺损基本完全修复。此结果符合临界骨缺损的标准,故直径6 mm可作为兔股骨髁临界骨缺损值。 ORCID: 0000-0002-1257-965X(徐石庄) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Quantifying cardiac‐induced brain tissue expansion using DENSE

Brain tissue undergoes viscoelastic deformation and volumetric strain as it expands over the cardiac cycle due to blood volume changes within the underlying microvasculature. Volumetric strain measurements may therefore provide insights into small vessel function and tissue viscoelastic properties. Displacement encoding via stimulated echoes (DENSE) is an MRI technique that can quantify the submillimetre displacements associated with brain tissue motion. Despite previous studies reporting brain tissue displacements using DENSE and other MRI techniques, a complete picture of brain tissue volumetric strain over the cardiac cycle has not yet been obtained. To address this need we implemented 3D cine‐DENSE at 7 T and 3 T to investigate the feasibility of measuring cardiac‐induced volumetric strain as a marker for small vessel blood volume changes. Volumetric strain over the entire cardiac cycle was computed for the whole brain and for grey and white matter tissue separately in six healthy human subjects. Signal‐to‐noise ratio (SNR) measurements were used to determine the voxel‐wise volumetric strain noise. Mean peak whole brain volumetric strain at 7 T (mean ± SD) was (4.5 ± 1.0) × 10^?4 (corresponding to a volume expansion of 0.48 ± 0.1 mL), which is in agreement with literature values for cerebrospinal fluid that is displaced into the spinal canal to maintain a stable intracranial pressure. The peak volumetric strain ratio of grey to white matter was 4.4 ± 2.8, reflecting blood volume and tissue stiffness differences between these tissue types. The mean peak volumetric strains of grey and white matter tissue were found to be significantly different (p < 0.001). The mean SNR at 7 T and 3 T of the DENSE measurements was 22.0 ± 7.3 and 7.0 ± 2.8 respectively, which currently limits a voxel‐wise strain analysis at both field strengths. We demonstrate that tissue specific quantification of volumetric strain is feasible with DENSE. This metric holds potential for studying blood volume pulsations in the ageing brain in healthy and diseased states.     

Acellular bovine pericardia with distinct porous structures fixed with genipin as an extracellular matrix

A cell extraction process was employed to remove the cellular components from bovine pericardia. Various porous structures of the acellular tissues were then created, using acetic acid and collagenase, and subsequently fixed with genipin. The biological response and tissue regeneration pattern for each studied group were evaluated in a growing rat model. One month postoperatively, fibroblasts, neoconnective tissue fibrils, and neocapillaries were observed in the acellular, acetic acid-treated, and collagenase-treated tissues to fill the pores within the implanted samples, indicating that these tissue samples were being regenerated. The neoconnective tissue fibrils were identified to be neocollagen fibrils and neoglycosaminoglycans. On the other hand, no tissue regeneration was observed in the cellular tissue throughout the entire course of the study; tissue regeneration was limited to the outer most layer of the acellular tissue. In contrast, the areas of tissue regeneration in the acetic acid-treated and collagenase-treated tissues were expanded with increasing duration of implantation. However, 1 year postoperatively there were still numerous inflammatory cells observed in the acetic acid-treated tissue, whereas inflammatory cells in the collagenase-treated tissue had almost disappeared. These results indicated that tissue regeneration patterns within acellular tissues were significantly affected by their porous structures.     

幼龄兔及成年兔桡骨骨缺损模型中骨缺损大小的对比研究

目的 探讨不同月龄新西兰兔建立桡骨骨缺损模型时骨缺损大小的选择。方法 选取3月龄(幼龄兔)及6月龄(成年兔)健康雄性新西兰兔各20只,根据兔龄分为A组(3月龄)和B组(6月龄),每组兔前肢采用数字表法随机分为2亚组制备桡骨骨缺损模型,每组20侧。其中A1组、B1组桡骨骨缺损长度为15 mm,A2组、B2组骨缺损长度为20 mm。分别于模型制备术后第4、8、12周行X线检查,并应用X线Lane-Sandhu评分标准评估骨愈合情况。术后12周处死所有实验动物,取桡骨标本进行大体及组织学观察,分析骨愈合情况。结果 制备骨缺损模型术后,所有实验兔均存活。X线检查显示:术后第8周A1组骨缺损基本愈合,至第12周新生骨塑形完全,与正常桡骨形态类似;其余3组至第12周骨缺损均未完全修复,断端及邻近尺侧有少量新骨生成,髓腔封闭。术后各时间点X线Lane-Sandhu评分结果示:组内比较,A1组评分均高于A2组,差异均有统计学意义(P值均<0.05);B1组与B2组评分比较,差异均无统计学意义(P值均>0.05)。组间缺损尺寸相同的亚组间比较:A1组、A2组评分分别高于B1组、B2组,差异均有统计学意义(P值均<0.05)。术后12周标本大体观察显示:A1组断端形成骨性桥接,新生骨塑形良好,其余3组断端髓腔封闭,缺损区由纤维组织填充。组织学结果示A1组修复完全,新生骨骨板排列规则;其余3组缺损空腔可见纤维组织填充。结论 兔龄和骨缺损大小对于术后骨缺损愈合情况有重要影响,在构建兔桡骨骨缺损模型的动物实验中,幼龄兔(3月龄)骨缺损长度宜选择20 mm,成年兔(6月龄)宜选择15 mm。     

Bone regeneration and infiltration of an anisotropic composite scaffold: an experimental study of rabbit cranial defect repair

Tissue formation on scaffold outer edges after implantation may restrict cell infiltration and mass transfer to/from the scaffold center due to insufficient interconnectivity, leading to incidence of a necrotic core. Herein, a nano-hydroxyapatite/polyamide66 (n-HA/PA66) anisotropic scaffold with axially aligned channels was prepared with the aim to enhance pore interconnectivity. Bone tissue regeneration and infiltration inside of scaffold were assessed by rabbit cranial defect repair experiments. The amount of newly formed bone inside of anisotropic scaffold was much higher than isotropic scaffold, e.g., after 12 weeks, the new bone volume in the inner pores was greater in the anisotropic scaffolds (>50%) than the isotropic scaffolds (<30%). The results suggested that anisotropic scaffolds could accelerate the inducement of bone ingrowth into the inner pores in the non-load-bearing bone defects compared to isotropic scaffolds. Thus, anisotropic scaffolds hold promise for the application in bone tissue engineering.     

Gene and transgenics nomenclature for the laboratory axolotl—Ambystoma mexicanum

The laboratory axolotl (Ambystoma mexicanum) is widely used in biological research. Recent advancements in genetic and molecular toolkits are greatly accelerating the work using axolotl, especially in the area of tissue regeneration. At this juncture, there is a critical need to establish gene and transgenic nomenclature to ensure uniformity in axolotl research. Here, we propose guidelines for genetic nomenclature when working with the axolotl.     

Effect of perforations in burr hole covers on cranial bone regeneration in rabbits

The reconstruction of bone defects is a significant problem in cranio-maxillofacial surgery. In an effort to avoid the known disadvantages of autogenous bone grafting, alternatives have been investigated. Bone substitute materials, degradable or nondegradable, aim at facilitating bone regeneration, while they take over load-bearing functions for a period of time. In this study, the healing of cranial defects in rabbits was assessed using polylactide guiding covers with and without perforations. Bilateral circular cranial defects were produced in 16 New Zealand white rabbits. The defects were covered with extruded and laser cut polylactide burr hole covers, each animal receiving a perforated burr hole cover on one side and a nonperforated one on the contralateral side. Bone seeking fluorochromes were administered at regular intervals. After an observation period of 8 weeks the amount of bone regeneration in the area of the defects was quantified from contact radiographs, and the dynamics of bone formation were assessed by fluorescence microscopy. Stained sections were used to analyze morphologic differences. No signs of adverse tissue reactions or osteolysis were observed. A bone-guiding function was observed for both covers with or without perforations. Intracranial tissue herniation into the defect hindered the regeneration process. Wide intraindividual and interindividual variation became apparent and average defect filling was only 40% within the 8-week observation period. In this model the perforated covers offered no advantage over nonperforated covers. It can be concluded from this study, that the use of external burr hole covers alone does not guarantee a full thickness regeneration of the cranial defect, but it provides a guiding function for promotion of structured bone regeneration.     

Repair and Reconstruction of a Resected Tumor Defect Using a Composite of Tissue Flap�CNanotherapeutic�CSilk Fibroin and Chitosan Scaffold

A multifaceted strategy using a composite of anti-cancer nanotherapeutic and natural biomaterials silk fibroin (SF) and chitosan (CS) blend scaffolds was investigated for the treatment of a tissue defect post-tumor resection by providing local release of the therapeutic and filling of the defect site with the regenerative bioscaffolds. The scaffold-emodin nanoparticle composites were fabricated and characterized for drug entrapment and release, mechanical strength, and efficacy against GILM2 breast cancer cells in vitro and in vivo in a rat tumor model. Emodin nanoparticles were embedded in SF and SFCS scaffolds and the amount of emodin entrapment was a function of the scaffold composition and emodin loading concentration. In vitro, there was a burst release of emodin from all scaffolds during the first 2?days though it was detected even after 24?days. Increase in emodin concentration in the scaffolds decreased the overall elastic modulus and ultimate tensile strength of the scaffolds. After 6?weeks of in vivo implantation, the cell density (p?相似文献   

Reparative Osteogenesis during Transplantation of Mesenchymal Stem Cells

Reparative osteogenesis was studied after xenotransplantation of suspension cell graft from human mesenchymal stem cells. A model of experimental damage to rat femoral diaphysis was developed. The state of animals was satisfactory and non-depressed in the early and late postoperation period. We revealed no local pathological reactions and complications. Administration of mesenchymal stem cells into the area of bone defect accelerated and improved regeneration. Unilateral transplantation of the cell graft stimulated regeneration in the contralateral limb due to acceleration of bone tissue maturation. On day 90 after treatment the bone regenerate was completely developed in the area of defect in animals of various groups. The newly formed bone tissue was well integrated into the bone organ. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 7, pp. 109–113, July, 2005     

聚乳酸膜管复合钙磷陶瓷引导性骨再生的实验研究

目的：采用可降解的生物活怀材料钙磷陶瓷人工骨置于膜管内、骨断端间。观察其引导性骨再生的效果,探讨机理。方法：选用新西兰成年大白兔３０只,平均体重２．５ｋｇ。按体重分成５组,每组６只,以双前肢为对象,采用标准的骨缺损模型,１２个对象随机分到Ｍ＋ＴＣＰ处理,对侧为对照侧。术后１、３、６、９、１２周进行大体、组织和影像学观察分析。结果 随时间全部动物骨缺损处有连续性骨痂通过缺损处。钙磷陶瓷逐渐吸收,组织     

组织工程骨-软骨复合组织修复兔膝关节部分缺损的实验研*

目的制备具备关节解剖形态的组织工程骨软骨,行原位移植修复兔关节大面积缺损,探讨组织再生方式及特点,为进一步研究提供研究基础。方法以兔耳原代软骨细胞和第三代成骨诱导的骨髓间充质干细胞为种子细胞,制备具有解剖形态的明胶-硫酸软骨素-透明质酸钠-明胶-陶瓷化骨软骨支架。分为复合细胞组﹙A﹚,无细胞组﹙B﹚和不修复组﹙C﹚。进行体内原位移植,术后不同时间进行HE染色,免疫组化染色及PCR检测。结果复合细胞组与其他两组相比,该组伴随支架吸收同时可以形成大量细胞外基质。而随着体内植入时间延长,不同组别间则出现了明显区别,从HE及免疫组化染色结果观察复合细胞组越来越具备正常骨-软骨组织学表现,而无细胞支架组则表现为纤维化改变。结论修复大面积的骨-软骨组织缺损,需要采用支架复合细胞的方式,单纯采用支架其修复效果是不可靠的。     

Biochemical and biomechanical evaluation of human pericardial membrane and demineralized bone matrix in rabbit calvarial defects

Regaining adequate bone strength, in bone loss, is one of the main purposes for new bone regeneration in bone tissue engineering. Biomechanical hardness test can be one approach to assay bone consistency in new bone formation. In addition, following up the serum alkaline phosphatase (ALP) alterations may help us in order to evaluate bone formation activity. In the current research, two groups of five male white New Zealand rabbits were studied. Two defects, 8 mm in diameter each, were made in each rabbit calvarium, one defect was filled with either human pericardial collagen (HPM) or demineralized bone matrix (DBM), and the other one was left empty as control. Every 10 days post-surgery, the serum ALP level was assessed, for 60 days. After performing euthanasia on day 60, the specimens were sent for biomechanical hardness test. The results for the DBM containing group were better than the HPM containing group in both biomechanical and biochemical tests. However, they were not statistically significant (p?>?0.05). In the biomechanical test, all the experimental groups, in both DBM and HPM, had significantly more hardness than the control (p?<?0.05). DBM is a current and well-known graft used in bone regeneration. Since, there was no significant difference between HPM and DBM on one hand, and the superiority of the HPM experimental group in the biomechanical test to the control on the other hand, HPM might be considered as a suitable graft in bone repair leading to acceptable bone strength.     

Assessment of biocompatibility and initial evaluation of genipin cross-linked elastin-like polypeptides in the treatment of an osteochondral knee defect in rabbits

Polypeptides based on the alternating hydrophobic and cross-linking domain structure of human elastin are capable of undergoing self-assembly to produce polymeric matrices with unique biological and mechanical properties. Here, we test the initial feasibility of using a genipin cross-linked elastin-based material as an acellular plug in the treatment of an osteochondral defect in the rabbit knee. Full-thickness defects in the weight-bearing surface of the medial femoral condyle in 18 New Zealand White rabbits were surgically produced and press fitted with cylindrical pads composed of genipin cross-linked elastin-like polypeptides, with identical wounds in the opposite knee left untreated as controls. The biocompatibility of the material, overall wound healing and regeneration of subchondral tissue was assessed at 2, 4 and 6 weeks by histological evaluation, synovial fluid analysis and microcomputerized tomography scanning. Histological analysis revealed the regeneration of subchondral bone at the periphery of the material, with evidence of hyaline-like overgrowth across the apical surface in 11/16 cases. Pads developed tight contacts with host tissue and appeared completely biocompatible, with no evidence of localized immune response or increased inflammation compared to controls. The material was stable to 6 weeks, with an aggregate elastic modulus calculated at ～470 kPa when tested under confined compression. Further studies are required to assess material degradation over time and long-term replacement with repair tissue.     

Brain atrophy and cognition: Interaction with cerebrovascular pathology?

We examined the interaction of brain atrophy and white matter lesions (WML) with cognitive functioning in 605 patients (mean age, 58 ± 10; 76% men) with atherosclerotic disease from the Second Manifestations of ARTerial disease-MR substudy (SMART-MR study). Automated brain segmentation was used to quantify volumes of brain tissue, cerebrospinal fluid, and WML on MRI. Total brain, ventricular, and cortical gray matter volume were divided by intracranial volume (ICV). Neuropsychological tests assessing executive functioning and memory performance were performed and composite scores were calculated. We observed that smaller total brain volume, larger ventricular volume, and smaller cortical gray matter volume (all as % of ICV) were associated with worse executive performance and that this association became stronger with presence of brain infarcts or severe WML volume (P-values for interaction <0.05). No interaction between measures of brain volume and cerebrovascular pathology on memory performance was observed. Our findings suggest that patients with cerebrovascular pathology on MRI may be more vulnerable to impairment in executive functioning related to global as well as focal brain atrophy.     

A synthetic oxygen carrier in fibrin matrices promotes sciatic nerve regeneration in rats

Tissue-engineering nerve conduits have been studied for a long time in bridging large nerve defects. However, the low oxygen availability within the nerve conduits, which results in death of migratory Schwann cells (SC) or loss of the newly formed tissue’s function, is still an obstacle for axonal regeneration. Thus, it was hypothesized that an oxygen-enriched conduit would enhance axonal regeneration and functional recovery in vivo. To address this issue, perfluorotributylamine (PFTBA) enriched fibrin hydrogel was prepared and injected into collagen–chitosan conduits. The conduit containing PFTBA-enriched fibrin hydrogel was then used to bridge a 12-mm sciatic nerve defect in rats. The control rats were bridged with collagen–chitosan conduits filled with fibrin matrices without PFTBA. It was found that axonal regeneration and functional recovery in the combined PFTBA group were significantly higher than those in the control group without PFTBA. Further investigations showed that the mRNA and protein levels of S-100, brain-derived neurotrophic factor and nerve growth factor were enhanced by PFTBA at 1 and 3 weeks after surgery. However, the mRNA and protein levels of vascular endothelial growth factor were in a similar range between the combined PFTBA group and the control group without PFTBA. In addition, immunohistochemical results showed that the morphological appearances of regenerated nerve and survival of SC were enhanced by PFTBA at 4 and 12 weeks after surgery. In conclusion, PFTBA-enriched nerve conduit is capable of enhancing axonal regeneration, which provides a new avenue for achieving better functional recovery in the treatment of nerve defect.     

Reconstruction of critical size calvarial bone defects in rabbits with glass-fiber-reinforced composite with bioactive glass granule coating

The aim of this study was to evaluate glass-fiber-reinforced composite as a bone reconstruction material in the critical size defects in rabbit calvarial bones. The bone defect healing process and inflammatory reactions were evaluated histologically at 4 and 12 weeks postoperatively. Possible neuropathological effects on brain tissue were evaluated. The release of residual monomers from the fiber-reinforced composite (FRC) was analyzed by high performance liquid chromatograph (HPLC). RESULTS: At 4 weeks postoperatively, fibrous connective tissue ingrowth to implant structures was seen. Healing had started as new bone formation from defect margins, as well as woven bone islets in the middle of the defect. Woven bone was also seen inside the implant. Inflammation reaction was slight. At 12 weeks, part of the new bone had matured to lamellar-type, and inflammation reaction was slight to moderate. Control defects had healed by fibrous connective tissue. Histological examinations of the brain revealed no obvious damage to brain morphology. In HPLC analysis, the release of residual 1,4-butanedioldimethacrylate and methylmethacrylate from polymerized FRC was low. CONCLUSIONS: This FRC-implant was shown to promote the healing process of critical size calvarial bone defect in rabbits. After some modifications to the material properties, this type of implant has the potential to become an alternative for the reconstruction of bone defects in the head and neck area in the future.     

Use of osteogenic bone-marrow precursor cells for reparative osteogenesis in the mandible of experimental animals

Using a model of “bony tissue tunnel defect” produced by the removal of a mandibular incisor in rats, it was found that closing the defect with a bioprosthesis prevented the washing out of osteogenic bone marrow precursor cells, which serve as a substrate for reparative osteogenesis, from the mandibular spongy bone. The reparative process was strongly stimulated if the bioprosthesis contained estrone; in this case, the time required for the tooth socket to be filled with osteogenic tissue was shortened by half. When no bone marrow elements were present in the socket, it was filled with fibrotic connective tissue, the number of bone marrow elements in spongy bone cavities was small, and the mandibular osteogenic tissue underwent atrophy. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 1, pp. 72–75, January, 1995