骨髓间充质干细胞与复合I型胶原和骨形态发生蛋白2的聚乳酸乙醇酸构建组织工程骨

目的探讨骨髓间充质干细胞(BMSC)体外分离培养后种植到复合Ⅰ型胶原和重组人类骨形态发生蛋白2(rhBMP-2)的聚乳酸乙醇酸(PLGA)生物支架上,构建组织工程骨的可行性.方法密度梯度离心法提取分离BMSC,倒置显微镜观察细胞形态,流式细胞分析法对细胞表面抗原进行鉴定.相分离法制备多孔三维PLGA生物支架,支架材料上复合Ⅰ型胶原和rhBMP-2,扫描电镜观察其超微结构.将第3代的BMSC接种于复合支架上,扫描电镜观察材料的细胞黏附性,将培养6 h 后的细胞-支架复合体植入SD大鼠肌袋内,于2个月后取材进行HE染色,观察其构建组织工程骨的情况.结果 BMSC可在体外分离扩增,表达CD29、CD44,不表达CD34和CD45.制备的PLGA支架孔隙率为90%,平均孔径为100 μm,与BMSC有较好的黏附性.2个月后动物体内细胞-支架复合体的大体观察和HE染色显示,BMSC种植到复合Ⅰ型胶原和rhBMP-2的PLGA生物支架上可构建骨组织.结论 BMSC可在体外长期、稳定培养,是理想的组织工程种子细胞.PLGA与干细胞有较好的黏附性,可用来做组织工程生物材料.BMSC种植到复合Ⅰ型胶原和rhBMP-2的PLGA生物支架上后,在动物体内可构建组织工程骨.     

腺病毒介导的人骨形态发生蛋白2基因转染骨髓间充质干细胞

背景：骨髓间充质干细胞作为骨、软骨创伤缺损及退变修复的种子细胞越来越受到关注。 目的：分析人骨形态发生蛋白2基因转染对白色封闭群大鼠(SD大鼠)骨髓间充质干细胞的影响。 方法：分离纯化SD大鼠骨髓间充质干细胞并体外扩增,通过腺病毒载体介导人骨形态发生蛋白2基因转染骨髓间充质干细胞,分别通过荧光显微镜观察荧光表达情况及蛋白质水平来测定转染后人骨形态发生蛋白2的表达,碱性磷酸酶定量测定鉴定成骨活性及MTT法评估人骨形态发生蛋白2转染对骨髓间充质干细胞的影响。 结果与结论：从SD大鼠骨髓提取物中分离培养的细胞形态为梭形,呈铺路石状、漩涡状生长,经流式细胞仪检测及多项分化能力鉴定符合骨髓间充质干细胞的特征;经转染人骨形态发生蛋白2基因后,骨髓间充质干细胞表达人骨形态发生蛋白2、碱性磷酸酶;MTT法检测转染人骨形态发生蛋白2基因后,骨髓间充质干细胞增殖能力明显增强(P < 0.05)。说明人骨形态发生蛋白2基因转染骨髓间充质干细胞后可以持续、高效表达人骨形态发生蛋白2和碱性磷酸酶,在体外明显促进骨髓间充质干细胞的增殖。     

携载rhBMP-2微球的新型复合人工骨的制备及生物相容性研究

目的制备一种具有良好生物相容性、降解性和成骨活性、可注射的自凝固新型骨修复材料。方法采用复乳溶剂挥发方法制备携载rhBMP-2的聚乳酸与聚乙醇酸共聚物（PLGA）微球，并将其与rhBMP-2／磷酸钙骨水泥（CPC）复合，制备出rhBMP-2／PLGA微球／CPC复合人工骨。探讨材料特性包括形貌和体外rhBMP-2释放速度，采用体外细胞培养的方法测定复合材料的细胞黏附能力及其浸提液对于人骨髓基质干细胞（MSCs）增殖和成骨分化的影响。结果与单纯rhBMP-2／CPC材料相比较，复合材料rhBMP-2体外释药明显提高。材料与MSCs可良好黏附并使其增殖。体外培养时材料不同时间的浸提液对MSCs细胞的增殖具有促进作用，对于细胞成骨分化的影响与单纯CPC无明显差别。结论rhBMP-2／PLGA微球／磷酸钙骨水泥新型复合人工骨具有良好的生物相容性和活性因子缓释功能，是一种有良好应用前景的骨修复材料。     

骨髓间充质干细胞在骨形态发生蛋白2/注射式硫酸钙载体上的成骨

背景：将生长因子复合到支架上构建复合材料可同时具备骨诱导和骨传导作用。 目的：观察骨形态发生蛋白2/注射式硫酸钙复合载体对大鼠骨髓间充质干细胞体外诱导成骨的影响。 方法：取生长状态良好的第2代SD大鼠骨髓间充质干细胞悬液,分3组培养：实验组将细胞悬液滴加到骨形态发生蛋白2/注射式硫酸钙复合材料表面,对照组在细胞悬液中加入骨形态发生蛋白2,空白对照组正常培养。 结果与结论：3组细胞随培养时间延长逐渐增多,实验组细胞数量最多,明显多于对照组及空白对照组(P < 0.05)。实验组培养不同时间点碱性磷酸酶活性高于对照组及空白对照组(P < 0.05)。体外实验显示骨形态发生蛋白2/注射式硫酸钙复合载体可促进骨髓间充质干细胞向成骨细胞分化。     

生物玻璃活性陶瓷复合人骨形态发生蛋白2基因修饰骨髓间充质干细胞修复颅骨缺损

背景:目前已有将体外培养的骨髓来源间充质细胞与支架复合后修复骨缺损的临床报道,但是由于该类复合材料中缺乏骨生长因子作用,其原位的成骨作用并不十分理想。目的:观察人骨形态发生蛋白2基因修饰的骨髓间充质干细胞与生物活性玻璃陶瓷复合材料在修复兔颅骨缺损中的原位成骨作用。方法:复苏冻存的人骨形态发生蛋白2基因修饰的骨髓间充质干细胞,与生物活性玻璃陶瓷复合培养获得人工植骨材料;制备兔双侧颅骨全层骨缺损模型,实验组将人工植骨材料植入骨缺损区,并设置空白质粒转染的骨髓间充质干细胞+生物活性玻璃陶瓷、骨髓间充质干细胞+生物活性玻璃陶瓷、空白组作对照,术后第4,8,12周对植骨区进行大体观察、X射线摄片、组织化学检测和生物化学检测。结果与结论:转染人骨形态发生蛋白2的骨髓间充质干细胞与生物活性玻璃陶瓷复合培养的人工植骨材料植入后第4周,骨缺损外周骨质与复合材料之间大部分被高密度阴影充填;第12周,完全被高密度阴影充填;第8周,骨小梁大部分相连成片;第12周,骨小梁粗大,骨髓再生。生物化学检测结果与组织化学检测结果一致,并且成骨效果及成骨活性明显优于对照组。说明携带人骨形态发生蛋白2基因的骨髓间充质干细胞与生物活性玻璃陶瓷复合构成的人工植骨材料基本符合骨组织工程学的要求,在骨缺损区原位具有良好的成骨作用。     

体外构建腺病毒介导骨形态发生蛋白2基因转染骨髓间充质干细胞复合纳米羟基磷灰石的植骨材料

背景:随着组织工程和基因工程技术迅速发展,基因增强的组织工程骨为临床治疗骨缺损带来美好的前景。目的:观察经腺病毒介导的人骨形态发生蛋白2表达载体(Ad-BMP-2)转染后的兔骨髓间充质干细胞在纳米羟基磷灰石植骨材料上的黏附、增殖及骨形态发生蛋白2的表达情况。方法:用Ad-BMP-2转染兔骨髓间充质干细胞,免疫组化、蛋白印迹法检测转染后细胞内骨形态发生蛋白2的表达情况。将转染48h的细胞均匀接种到纳米羟基磷灰石植骨材料上,扫描电镜观察细胞黏附状况,并采用MTT比色法测定骨髓间充质干细胞的增殖情况;消化收集黏附植骨材料上第3,5,7天的细胞,蛋白印迹检测黏附材料上细胞骨形态发生蛋白2的表达。结果与结论:转染后,骨髓间充质干细胞内骨形态发生蛋白2有高表达;扫描电镜见转染细胞在纳米羟基磷灰石材料孔隙周围及孔隙内黏附生长良好并大量增殖,MTT分析结果显示,纳米羟基磷灰石对骨髓间充质干细胞的体外增殖无抑制作用,复合后骨形态发生蛋白2有较高表达。结果表明经Ad-BMP-2转染后的骨髓间充质干细胞与纳米羟基磷灰石植骨材料生物相容性好,细胞在材料上能稳定长效地分泌骨形态发生蛋白2。     

完全脱钙骨基质与骨髓间充质干细胞体外诱导构建组织工程纤维软骨

背景:含有骨形态发生蛋白的完全脱钙骨基质可使骨髓间充质干细胞向软骨细胞分化并维持其软骨细胞的特性,在软骨发生过程中发挥重要作用.目的:将骨髓间充质干细胞与完全脱钙骨基质在体外诱导培养成纤维软骨组织以及观察培养体系与支架材料对细胞凋亡的影响.方法:采用全骨髓培养法分离培养猪骨髓间充质干细胞,取第1代骨髓间充质干细胞均匀接...     

骨形态发生蛋白2/注射式硫酸钙缓释载体的生物相容性

背景：目前硫酸钙主要被作为抗生素载体和成骨因子载体。 目的：观察骨形态发生蛋白2/注射式硫酸钙缓释系统的体外缓释效果及与种子细胞的生物相容性。 方法：制备骨形态发生蛋白2/注射式硫酸钙缓释系统,检测其体外释放性能。将SD大鼠骨髓间充质干细胞经体外诱导培养、扩增后,种植于骨形态发生蛋白2/注射式硫酸钙缓释载体和单纯的注射式硫酸钙支架上行体外培养。 结果与结论：骨形态发生蛋白2/注射式硫酸钙缓释支架具有缓释骨形态发生蛋白2的效果,持续时间可达31 d。骨形态发生蛋白2/注射式硫酸钙缓释支架与大鼠骨髓间充质干细胞具有优良的生物相容性,并且相同时间点支架上的细胞黏附率、细胞数量及细胞碱性磷酸酶活性均明显高于注射式硫酸钙支架;扫描电镜发现两组材料上均有细胞生长,骨形态发生蛋白2/注射式硫酸钙缓释支架上的细胞在支架表面和孔隙内生长良好,细胞突起接触融合,细胞密集区域可见细胞外基质形成,大量细胞包绕在材料表面;注射式硫酸钙支架上的细胞黏附数量较少,生长情况不及骨形态发生蛋白2/注射式硫酸钙缓释支架上的细胞。     

大鼠骨髓间充质干细胞与PLGA构建组织工程脂肪的实验研究

目的探讨采用聚乳酸一聚乙醇酸共聚物（PLGA）生物支架及骨髓间充质干细胞，构建组织工程化脂肪组织的可行性。方法将雄性大鼠骨髓间充质干细胞接种于PLGA支架上，成脂诱导培养1周，扫描电镜观察细胞在支架上的生长及黏附情况；同时，将细胞一支架复合体异体移植于雌性大鼠体内，观察其成脂情况，并使用原位杂交技术鉴定。结果在生物支架上大量成脂细胞呈簇状生长；1个月时可见脂肪组织形成，3个月时脂肪组织成熟。结论PLGA生物支架是一种理想的生物可降解支架，骨髓间充质干细胞接种于PLGA生物支架可用于组织工程化脂肪的研究。     

pIRES-骨形态发生蛋白2质粒转染大鼠骨髓间充质干细胞后的 持续表达

背景：重组人骨形态发生蛋白2已被广泛应用于骨组织工程治疗骨缺损或骨不连,但是直接应用外源性骨形态发生蛋白2修复骨缺损效果不理想。 目的：观察转染pIRES-骨形态发生蛋白2的大鼠骨髓间充质干细胞持续合成并分泌骨形态发生蛋白2的情况。 方法：全骨髓贴壁法分离培养大鼠骨髓间充质干细胞,脂质体介导下将真核表达质粒pIRES-骨形态发生蛋白2导入大鼠骨髓间充质干细胞。 结果与结论：ELISA结果显示,随着pIRES-骨形态发生蛋白2转染时间的延长,大鼠骨髓间充质干细胞分泌的骨形态发生蛋白2逐渐增多,至转染后10~12 d达高峰,转染后15 d,仍可见较多骨形态发生蛋白2的表达。说明转染pIRES-骨形态发生蛋白2的大鼠骨髓间充质干细胞可持续稳定分泌骨形态发生蛋白2。     

RhBMP-2 microspheres-loaded chitosan/collagen scaffold enhanced osseointegration: an experiment in dog

The purpose of this study is to develop a novel recombinant human bone morphogenetic protein-2 (rhBMP-2) sustained release scaffold for dental implant osseointegration, and to evaluate the effect of this scaffold on promoting bone formation. RhBMP-2 was encapsulated in the poly-D,L-lactide-co-glycolide (PLGA) biodegradable microspheres, which were subsequently dispersed in a chitosan/collagen composite scaffold. This rhBMP-2 microspheres-loaded scaffold (S-MB) was compared with a chitosan/collagen scaffold without microspheres that directly encapsulated rhBMP-2 (S-B) in vitro and in vivo. The microstructure of the new scaffold was examined with scanning electron microscopy. The release profile of rhBMP-2 in vitro was measured at interval periods. The effect of rhBMP-2 encapsulated scaffolds on enhancing bone formation through implantation in dogs' mandibles was identified by histological examination of the regenerated bone after 4 weeks of implantation. Due to PLGA microspheres being loaded, the S-MB exhibited lower values at porosity and swelling rate, as well as a higher effective release dose than that of the S-B. Bone density, bone-implant contact, and bone-fill values measured from dog experiments demonstrated that the S-MB induced bone regeneration more quickly and was timely substituted by new bone. It was concluded that this sustained carrier scaffold based on microspheres was more effective to induce implant osseointegration.     

The enhancement of osteogenesis by nano-fibrous scaffolds incorporating rhBMP-7 nanospheres

It is advantageous to incorporate controlled growth factor delivery into tissue engineering strategies. The objective of this study was to develop a three-dimensional (3D) porous tissue engineering scaffold with the capability of controlled releasing recombinant human bone morphogenetic protein-7 (rhBMP-7) for enhancement of bone regeneration. RhBMP-7 was first encapsulated into poly(lactic-co-glycolic acid) (PLGA) nanospheres (NS) with an average diameter of 300nm. Poly(l-lactic acid) (PLLA) scaffolds with interconnected macroporous and nano-fibrous architectures were prepared using a combined sugar sphere template leaching and phase separation technique. A post-seeding technique was then utilized to immobilize rhBMP-7 containing PLGA nanospheres onto prefabricated nano-fibrous PLLA scaffolds with well-maintained 3D structures. In vitro release kinetics indicated that nanosphere immobilized scaffold (NS-scaffold) could release rhBMP-7 in a temporally controlled manner, depending on the chemical and degradation properties of the NS which were immobilized onto the scaffold. In vivo, rhBMP-7 delivered from NS-scaffolds induced significant ectopic bone formation throughout the scaffold while passive adsorption of rhBMP-7 into the scaffold resulted in failure of bone induction due to either the loss of rhBMP-7 biological function or insufficient duration within the scaffold. We conclude that the interconnected macroporous architecture and the sustained, prolonged delivery of bioactive rhBMP-7 from NS immobilized nano-fibrous scaffolds actively induced new bone formation throughout the scaffold. The approach offers a new delivery method of BMPs and a novel scaffold design for bone regeneration.     

Repair of diaphyseal bone defects with calcitriol-loaded PLGA scaffolds and marrow stromal cells

Calcitriol (1,25(OH)2D3)-loaded porous poly(D,L-lactide-co-glycolide) (PLGA) scaffolds prepared by solvent casting/salt leaching method were used to repair a 1.5 cm diaphyseal segmental bone defect as a fully absorbable osteogenic biomaterial. The in vitro release of sulforhodamine B (SRB) from PLGA scaffold was measured using spectrophotometer, considering SRB as a model drug. The SRB released from SRB-incorporated PLGA scaffold during 3 months was with relatively low initial burst. The calcitriol-loaded PLGA scaffolds with or without marrow stromal cells (MSCs) were implanted in a critical-sized intercalated bone defect in rabbit femur. Defects were assessed by radiographs until 9 weeks. The bony union of the defect was observed only in the calcitriol-loaded groups. RT-PCR results indicated that MSCs, which were seeded into calcitriol-loaded scaffold, expressed an increased level of alkaline phosphatase, osteonectin, and type I collagen mRNA at day 10. After 2 and 4 weeks, the implanted scaffolds were evaluated by histology. New osteoid matrix and direct calcium deposits were more evident in calcitriol/PLGA/MSC group. Three-dimensional computed tomography and frontal tomographic images of repaired femur showed that normal femur anatomy had been restored with cortical bone with no implanted PLGA remnants at 20 weeks. It can be concluded that the porous calcitriol-loaded PLGA scaffold combined with MSCs may be a novel method for repairing the large loaded bone defect.     

The bioactivity of rhBMP-2 immobilized poly(lactide-co-glycolide) scaffolds

In this study, immobilization of rhBMP-2 on polylactone-type polymer scaffolds via plasma treatment was investigated. To introduce proper functional groups on the surface of poly(lactide-co-glycolide) (PLGA) matrix, PLGA films were treated under different atmospheres, such as oxygen, ammonia and carbon dioxide, respectively, and then incubated in rhBMP-2 solution of de-ionized water. The effect of various plasma-treated PLGA films on binding rhBMP-2 was investigated and compared. It was found that PLGA binding ability to rhBMP-2 was enhanced by carbon dioxide and oxygen plasma treatment, and the binding ability of the oxygen plasma-treated PLGA (OT-PLGA) to rhBMP-2 was the strongest after oxygen plasma treating for 10 min under a power of 50 W. The changes of surface chemistry and surface topography of PLGA matrix induced by oxygen plasma treatment played main roles in improving the PLGA binding ability to rhBMP-2. The stability of rhBMP-2 bound on OT-PLGA film was determined under a dynamic condition by a Parallel Plate Flow Chamber. The result showed that the rhBMP-2 had been immobilized on the OT-PLGA film. Mouse OCT-1 osteoblast-like cell as a model cell was cultured on the rhBMP-2 bound OT-PLGA (OT-PLGA/BMP) in vitro, which showed that the bound rhBMP-2 via oxygen plasma treatment was bioactive. Depending on hydrophilicity and rich polar O-containing groups of the OT-PLGA scaffold, different amount of rhBMP-2 could be evenly immobilized on the surface of the OT-PLGA scaffold. The immobilized rhBMP-2 had stimulated differentiation of OCT-1 cell and accelerated process of mineralization of OCT-1 cell in the scaffold. It revealed the rhBMP-2 immobilized PLGA scaffold had good cell affinity.     

The bone formation in vitro and mandibular defect repair using PLGA porous scaffolds

Highly porous scaffolds of poly(lactide-co-glycolide) (PLGA) were prepared by solution-casting/salt-leaching method. The in vitro degradation behavior of PLGA scaffold was investigated by measuring the change of normalized weight, water absorption, pH, and molecular weight during degradation period. Mesenchymal stem cells (MSCs) were seeded and cultured in three-dimensional PLGA scaffolds to fabricate in vitro tissue engineering bone, which was investigated by cell morphology, cell number and deposition of mineralized matrix. The proliferation of seeded MSCs and their differentiated function were demonstrated by experimental results. To compare the reconstructive functions of different groups, mandibular defect repair of rabbit was made with PLGA/MSCs tissue engineering bone, control PLGA scaffold, and blank group without scaffold. Histopathologic methods were used to estimate the reconstructive functions. The result suggests that it is feasible to regenerate bone tissue in vitro using PLGA foams with pore size ranging from 100-250 microm as scaffolding for the transplantation of MSCs, and the PLGA/MSCs tissue engineering bone can greatly promote cell growth and have better healing functions for mandibular defect repair. The defect can be completely recuperated after 3 months with PLGA/MSCs tissue engineering bone, and the contrastive experiments show that the defects could not be repaired with blank PLGA scaffold. PLGA/MSCs tissue engineering bone has great potential as appropriate replacement for successful repair of bone defect.     

Sustained release of ascorbate-2-phosphate and dexamethasone from porous PLGA scaffolds for bone tissue engineering using mesenchymal stem cells

The purpose of this research was to develop porous poly(D,L-lactide-co-glycolide) (PLGA) scaffolds from which ascorbate-2-phosphate (AsAP) and dexamethasone (Dex) are continuously released for a month for osteogenesis of mesenchymal stem cells for bone tissue engineering. Porous PLGA matrices containing AsAP and Dex were prepared by solvent casting/particulate leaching method. In vitro release and water uptake studies were performed in Dulbecco's phosphate buffered saline at 37 degrees C and 15 rpm. Drug loading and release rates were determined by high performance liquid chromatography. Release studies of Dex and AsAP showed that, after an initial burst release lasting 4 and 9 days, respectively, release rates followed zero order kinetics with high correlation coefficients at least until 35 days. Incorporation of AsAP into the scaffolds increased the release rates of Dex and AsAP, and the scaffold water uptake. When mesenchymal stem cells (MSCs) were cultured in the AsAP and Dex containing scaffolds in vitro, the amount of mineralization was significantly higher than in control scaffolds. In conclusion, AsAP and Dex were incorporated into porous PLGA scaffolds and continuously released over a month and osteogenesis of MSCs was increased by culture in these scaffolds.     

仿生活性人工软骨的体外构建及其异位成软骨分化实验研究

应用先进快速成形技术(RP)制备32枚粒度均匀(尺寸均为4mm×4mm×4mm)的聚乳酸-聚羟乙酸(PLGA)人工载体,该载体经I型胶原表面修饰后均分为A、B两组。A组载体复合人骨形态发生蛋白-2基因转染(rAAV-hBM P-2)的兔骨髓基质细胞(M SC s,2×104个细胞/枚);B组每枚载体复合等量、同代次、未基因转染M SC s。体外培养第5 d,从两组各取12枚细胞-载体复合物植入裸鼠皮下,术后30 d取材观察。结果发现rAAV-hBM P-2转染的M SC s成功表达目的基因。RP制备的PLGA载体具有良好的空间结构,大孔及材料表面微孔孔径分别为300μm和3~5μm。体外培养3~5 d,两组载体均复合生长着大量种子细胞。皮下埋植30 d,A组植入物形成较为典型的软骨细胞及基质,II型胶原蛋白表达阳性;同期B组植入物无软骨组织形成。A组聚酯材料面积百分率显著低于B组(P<0.01)。结果表明RP结合载体材料表面修饰,能制备出兼具理想孔隙结构和良好生物相容性的组织工程支架载体,该载体高效复合rAAV-hBM P-2转染的M SC s为组织工程软骨构建创造有利条件。     

Retention and activity of BMP-2 in hyaluronic acid-based scaffolds in vitro.

Bone morphogenetic protein-2 (BMP-2) delivered in a suitable implantable matrix has the potential to repair local skeletal defects by inducing new bone formation from undifferentiated pluripotent stem cells resident in host tissue. In this study, we examined in vitro the potential of a derivatized hyaluronic acid (Hyaff-11) scaffold as a delivery vehicle for recombinant human BMP-2 (rhBMP-2) in bone and cartilage repair therapies. Hyaff-11 scaffolds were fabricated using a phase inversion/particulate leaching method and soak-loaded with rhBMP-2. In vitro release kinetics of rhBMP-2, demonstrated using enzyme-linked immunosorbant assay and alkaline phosphatase (ALP) assay revealed a slow, sustained rhBMP-2 release during 28 days, with a cumulative release of 31.82% of the initial rhBMP-2 loaded. rhBMP-2 was released in bioactive form as demonstrated by ALP induction of pluripotent cell line, C3H10T1/2 (T1/2), down the osteoblast lineage when incubated with the release supernatants. rhBMP-2 retention in Hyaff-11 scaffolds was greater than that from collagen gels, which released most of the initially loaded rhBMP-2 by 14 days. rhBMP-2-loaded Hyaff-11 scaffolds were also seeded with T1/2 cells and evaluated at 3, 7, 14, and 28 days for viability and expression of osteoblast phenotype. Cells remained viable throughout the study and expressed a time- and dose-dependent ALP and osteocalcin expression in the rhBMP-2 groups. Based on these observations, Hyaff-11 scaffolds may be suitable delivery systems for rhBMP-2 in bone/cartilage repair because of their ability to retain rhBMP-2, release low levels of bioactive rhBMP-2 to the local environment in a sustained manner, and stimulate differentiation of pluripotent stem cells.     

Biodegradable composite scaffolds incorporating an intramedullary rod and delivering bone morphogenetic protein-2 for stabilization and bone regeneration in segmental long bone defects

In this study, a two-part bone tissue engineering scaffold was investigated. The scaffold consists of a solid poly(propylene fumarate) (PPF) intramedullary rod for mechanical support surrounded by a porous PPF sleeve for osseointegration and delivery of poly(dl-lactic-co-glycolic acid) (PLGA) microspheres with adsorbed recombinant human bone morphogenetic protein-2 (rhBMP-2). Scaffolds were implanted into critical size rat segmental femoral defects with internal fixation for 12 weeks. Bone formation was assessed throughout the study via radiography, and following euthanasia, via microcomputed tomography and histology. Mechanical stabilization was evaluated further via torsional testing. Experimental implant groups included the PPF rod alone and the rod with a porous PPF sleeve containing PLGA microspheres with 0, 2 or 8 μg of rhBMP-2 adsorbed onto their surface. Results showed that presence of the scaffold increased mechanical stabilization of the defect, as evidenced by the increased torsional stiffness of the femurs by the presence of a rod compared to the empty defect. Although the presence of a rod decreased bone formation, the presence of a sleeve combined with a low or high dose of rhBMP-2 increased the torsional stiffness to 2.06 ± 0.63 and 1.68 ± 0.56 N·mm, respectively, from 0.56 ± 0.24 N·mm for the rod alone. The results indicate that, while scaffolds may provide structural support to regenerating tissues and increase their mechanical properties, the presence of scaffolds within defects may hinder overall bone formation if they interfere with cellular processes.