Fetal vs adult mesenchymal stem cells achieve greater gene expression, but less osteoinduction

AIM: To investigate adenoviral transduction in mesenchymal stem cells(MSCs) and effects on stemness in vitro and function as a cell therapy in vivo.METHODS: Bone marrow-derived adult and fetal MSC were isolated from an equine source and expanded in monolayer tissue culture. Polyethylenimine(PEI)-mediated transfection of pc DNA3-e GFP or adenoviral transduction of green fluorescent protein(GFP) was evaluated in fetal MSCs. Adenoviral-mediated transduction was chosen for subsequent experiments. All experiments were carried out at least in triplicate unless otherwise noted. Outcome assessment was obtained by flow cytometry or immunohystochemistry and included transduction efficiency, cell viability, stemness(i.e., cell proliferation, osteogenic and chondrogenic cell differentiation), and quantification of GFP expression. Fetal and adult MSCs were then transduced with an adenoviral vector containing the gene for the bone morphogenic protein 2(BMP2). In vitro BMP2 expression was assessed by enzyme linked immunosorbent assay. In addition, MSC-mediated gene delivery of BMP2 was evaluated in vivo in an osteoinduction nude mouse quadriceps model. New bone formation was evaluated by microradiography and histology.RESULTS: PEI provided greater transfection and viability in fetal MSCs than other commercial chemical reagents. Adenoviral transduction efficiency was superior to PEI-mediated transfection of GFP in fetal MSCs(81.3% ± 1.3% vs 35.0% ± 1.6%, P < 0.05) and was similar in adult MSCs(78.1% ± 1.9%). Adenoviral transduction provided significantly greater expression of GFP in fetal than adult MSCs(7.4 ± 0.1 vs 4.4 ± 0.3 millions of mean fluorescence intensity units, P < 0.01) as well as significantly greater in vitro BMP2 expression(0.16 pg/cell-day vs 0.10 pg/cell-day, P < 0.01). Fraction of fetal MSC GFP positive cells decreased significantly faster than adult MSCs(1.15% ± 0.05% vs 11.4% ± 2.1% GFP positive at 2 wk post-transduction, P < 0.05). Cell proliferation and osteogenic differentiation in vitrowere not affected by Ad transduction in both fetal and adult MSCs, but fetal MSCs had reduced chondrogenic differentiation in vitro when compared to adult(P < 0.01). Chondrogenic differentiation was also significantly reduced in Ad-GFP transduced cells(P < 0.05). AdBMP2 transduced adult MSCs induced new bone formation in more thighs than Ad-BMP2 transduced fetal MSCs(83% vs 17% of the six treated thighs per group, P < 0.05) and resulted in increased femur midshaft diameter due to greater extent of periosteal new bone(1.57 ± 0.35 mm vs 1.27 ± 0.08 mm, P < 0.05).CONCLUSION: Fetal MSCs may be genetically manipulated ex vivo with adenoviral vectors. Nonetheless, the abbreviated expression of the exogenous gene may limit their applications in vivo.

Integrating Biodegradable 3-Dimensional-Printing into Tracheal Reconstruction

Background: Currently, there is no set standard treatment for long-segment tracheomalacia and stenosis. In this study we set out to explore the potential to create a tissue engineered, biodegradable and three-dimensionally (3D) printed tracheal ring as a first step towards bioengineering a long segment tracheal replacement. Method of Approach: A 3D-Computer aided design (CAD) model was produced with multiple channels to allow for cellular growth while mimicking the native anatomy. The design was optimized to allow for printability, cellular expansion, and integration and 3D printed using a modified commercial 3D printer. Results: The cells grown in the scaffold demonstrated a similar proliferation trend compared to control. Chondrocytes within the 3D printed ring retained their phenotypic properties and did not infer any significant change in flexibility, contour and strength to the scaffold. Conclusion: The combination of living cells and a 3D modeled patient specific graft may address some of the unmet clinical needs in the field of tracheal reconstruction. This proof of concept study represents a first step towards producing a 3D printed and tissue engineered long segment tracheal replacement graft for airway surgery.

A novel non-invasive method for predicting bone mineral density and fracture risk using demographic and anthropometric measures

Fractures are costly to treat and can significantly increase morbidity.Although dual-energy x-ray absorptiometry(DEXA)is used to screen at risk people with low bone mineral density(BMD),not all areas have access to one.We sought to create a readily accessible,inexpensive,high-throughput prediction tool for BMD that may identify people at risk of fracture for further evaluation.Anthropometric and demographic data were collected from 492 volunteers(♂275,♀217;[44-20]years;Body Mass Index(BMI)=[27.6-6.0]kg/m^(2))in addition to total body bone mineral content(BMC,kg)and BMD measurements of the spine,pelvis,arms,legs and total body.Multiple-linear-regression with step-wise removal was used to develop a two-step prediction model for BMC followed by BMC.Model selection was determined by the highest adjusted R2,lowest error of estimate,and lowest level of variance inflation(α=0.05).Height(HTcm),age(years),sex^(m=1,f=0),%body fat(%fat),fat free mass(FFMkg),fat mass(FMkg),leg length(LLcm),shoulder width(SHWDTHcm),trunk length(TRNKLcm),and pelvis width(PWDTHcm)were observed to be significant predictors in the following two-step model(p<0.05).Step1:BMC(kg)=(0.0063×HT)+(-0.0024×AGE)+(0.1712×SEX^(m=1,f=0))+(0.0314×FFM)+(0.001×FM)+(0.0089×SHWDTH)+(-0.0145×TRNKL)+(-0.0278×PWDTH)-0.5073;R^(2)=0.819,SE-0.301.Step2:Total body BMD(g/cm^(2))=(-0.0028×HT)+(-0.0437×SEX^(m=1,f=0))+(0.0008×%FAT)+(0.2970×BMC)+(-0.0023×LL)+(0.0023×SHWDTH)+(-0.0025×TRNKL)+(-0.0113×PWDTH)+1.379;R^(2)=0.89,SE-0.054.Similar models were also developed to predict leg,arm,spine,and pelvis BMD(R^(2)=0.796-0.864,p<0.05).The equations developed here represent promising tools for identifying individuals with low BMD at risk of fracture who would benefit from further evaluation,especially in the resource or time restricted setting.

Alendronate treatment does not inhibit bone formation within biphasic calcium phosphate ceramics in posterolateral spinal fusion： an experimental study in porcine model

Background Biphasic calcium phosphate （BCP） ceramics has a potential advantage as an osteoconductive matrix and has an optimal resorption rate for bone formation. Using BCP ceramics as a bone graft during spinal fusion requires osteogenesis within the material and subsequent bridging between adjacent vertebraes to provide long-term support. Bisphosphonates have been reported to prolong the process of bone healing. The influence of bisphosphonate treatment on bone formation within BCP ceramics in spinal fusion remains unknown. The aim of this study was to evaluate the influence of alendronate on BCP osteoaenesis in Dosterolateral spinal fusion.Methods Posterolateral spinal fusion with pedicle screw fixation was performed at the lumbar spine in twenty-two pigs. BCP ceramics were applied as a bone graft to obtain bone fusion between adjacent transverse processes. Eleven pigs in the treatment group received oral alendronate 10 mg/d for three months postoperatively. Eleven pigs in the control group did not receive treatment with alendronate. All animals underwent posterolateral spinal fusion with BCP ceramics. The fusion rate was evaluated three months after the operation.Results The fusion rates evaluated by X-ray were 27.3% in the treatment group and 20% in the control group. The fusion rates using histological evaluation were 18.2% in the treatment group and 20% in the control group. The mean volumes of fusion mass were （3.64±0.86） cm^3 in the treatment group and （4.26±0.63） cm^3 in the control group. No significant differences were found in either trabecular bone volume or residual BCP volume between treatment and control groups using histological evaluation. The new bone formation within BCP ceramics was greater in the area adjacent to transverse process （P 〈0.01）.Conclusion Oral alendronate with a dose of 10 mg daily do not inhibit bone formation within BCP ceramics or affect the fusion rate in posterolateral spinal fusion from porcine models.

Scaffolds for central nervous system tissue engineering

Traumatic injuries to the brain and spinal cord of the central nervous system （CNS） lead to severe and permanent neurological deficits and to date there is no universally accepted treatment. Owing to the profound impact, extensive studies have been carried out aiming at reducing inflammatory responses and overcoming the inhibitory environment in the CNS after injury so as to enhance regeneration. Artificial scaffolds may provide a suitable environment for axonal regeneration and functional recovery, and are of particular importance in cases in which the injury has resulted in a cavitary defect. In this review we discuss development of scaffolds for CNS tissue engineering, focusing on mechanism of CNS injuries, various biomaterials that have been used in studies, and current strategies for designing and fabricating scaffolds.