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| High Costs of Stem Cell Therapy: Will Stem Cell Firms Share More Risk?
March 24, 2010 at 6:59 PM
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| Stem cell therapies are likely to be quite costly because of high development expenses and potentially high usage, according to a new report from the University of California at Berkeley, which said that new "financial risk-sharing mechanisms" could be needed.
"The cost impact of the therapy is likely to be high, because of a therapy's high cost per patient, and the potentially large number of | | |
| Effect of myogenic stem cells on contractile properties of the repaired and unrepaired transected external anal sphincter in an animal model.
March 24, 2010 at 8:21 AM
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| | Effect of myogenic stem cells on contractile properties of the repaired and unrepaired transected external anal sphincter in an animal model. Obstet Gynecol. 2010 Apr;115(4):815-23 Authors: White AB, Keller PW, Acevedo JF, Word RA, Wai CY OBJECTIVE:: To estimate the effect of myogenic stem cells on contractile function of the external anal sphincter after transection with or without repair in an animal model. METHODS:: One hundred twenty virginal female rats were randomly assinged to repair (n=60) or no repair (n=60) after anal sphincter transection. Animals were further divided into two groups: 40-microliter injection at the transection site with either phosphate-buffered solution (control) or myogenic stem cells (3.2x10 cells). Animals were killed at 7, 21, or 90 days, and the anal sphincter complex dissected and analyzed for contractile function. RESULTS:: Contractile function of the external anal sphincter was severely impaired 7 days after sphincter transection with or without repair. Twitch tension, maximal tetanic contraction, and maximal contractile force in response to electrical field stimulation improved significantly with time after sphincter repair. Injection of myogenic stem cells in ! the anal sphincter at the time of repair resulted in superior contractile function at both 7 days and 90 days compared with controls. Interestingly, contractile function of the nonrepaired external anal sphincter did not improve with time with or without myogenic stem cells. Indicators of denervation (fatigue and twitch or tetany ratios) did not change among groups. CONCLUSION:: In this animal model, injection of myogenic stem cells at the time of external anal sphincter repair resulted in enhanced contractile function at 90 days compared with repair alone. Without repair, function of the external anal sphincter was not improved by stem cell therapy at any time point. These results suggest that addition of myogenic stem cells improves both acute and long-term function of the external anal sphincter after mechanical injury. PMID: 20308844 [PubMed - in process] | | |
| How to measure the effects of the intracoronary stem cell therapy?
March 24, 2010 at 8:21 AM
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| | How to measure the effects of the intracoronary stem cell therapy? Eur J Echocardiogr. 2010 Mar 22; Authors: Tendera M, Wojakowski W The results of clinical studies showed that there is a moderate increase in left ventricular (LV) ejection fraction (EF) at 4-6 months after stem cell therapy. So far, the endpoint of such trials was the change of LVEF and volumes measured by LV angiography or MRI; however, these parameters might not be optimal to assess the effects of BMC therapy. BOOST trial was one of the first studies addressing the effect of bone marrow cell transfer in patients with acute ST-elevation myocardial infarction. The results of 5-year follow-up were reported, showed no sustained effect on the LV systolic function in the whole group, but some beneficial effects on diastolic function were found. Other study showed using tissue-Doppler that after implantation of selected CD133+ and CD133-CD34+ bone marrow-derived cells in patients with history of anterior MI and severely reduced LVEF the indices of regional LV systolic function improved. Clinical significance of these findings remain! s to be established; however, the assessment of diastolic function and tissue-Doppler imaging might be valuable parameters in stem cell-based trials. PMID: 20308192 [PubMed - as supplied by publisher] | | |
| Basic Science and Clinical Application of Stem Cells in Veterinary Medicine.
March 24, 2010 at 6:25 AM
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| | Basic Science and Clinical Application of Stem Cells in Veterinary Medicine. Adv Biochem Eng Biotechnol. 2010 Mar 23; Authors: Ribitsch I, Burk J, Delling U, Geißler C, Gittel C, Jülke H, Brehm W Stem cells play an important role in veterinary medicine in different ways. Currently several stem cell therapies for animal patients are being developed and some, like the treatment of equine tendinopathies with mesenchymal stem cells (MSCs), have already successfully entered the market. Moreover, animal models are widely used to study the properties and potential of stem cells for possible future applications in human medicine. Therefore, in the young and emerging field of stem cell research, human and veterinary medicine are intrinsically tied to one another. Many of the pioneering innovations in the field of stem cell research are achieved by cooperating teams of human and veterinary medical scientists.Embryonic stem (ES) cell research, for instance, is mainly performed in animals. Key feature of ES cells is their potential to contribute to any tissue type of the body (Reed and Johnson, J Cell Physiol 215:329-336, 2008). ES cells are capable of self-renewal an! d thus have the inherent potential for exceptionally prolonged culture (up to 1-2 years). So far, ES cells have been recovered and maintained from non-human primate, mouse (Fortier, Vet Surg 34:415-423, 2005) and horse blastocysts (Guest and Allen, Stem Cells Dev 16:789-796, 2007). In addition, bovine ES cells have been grown in primary culture and there are several reports of ES cells derived from mink, rat, rabbit, chicken and pigs (Fortier, Vet Surg 34:415-423, 2005). However, clinical applications of ES cells are not possible yet, due to their in vivo teratogenic degeneration. The potential to form a teratoma consisting of tissues from all three germ lines even serves as a definitive in vivo test for ES cells.Stem cells obtained from any postnatal organism are defined as adult stem cells. Adult haematopoietic and MSCs, which can easily be recovered from extra embryonic or adult tissues, possess a more limited plasticity than their embryonic counterparts (Reed and Johnso! n, J Cell Physiol 215:329-336, 2008). It is believed that thes! e stem c ells serve as cell source to maintain tissue and organ mass during normal cell turnover in adult individuals. Therefore, the focus of attention in veterinary science is currently drawn to adult stem cells and their potential in regenerative medicine. Also experience gained from the treatment of animal patients provides valuable information for human medicine and serves as precursor to future stem cell use in human medicine.Compared to human medicine, haematopoietic stem cells only play a minor role in veterinary medicine because medical conditions requiring myeloablative chemotherapy followed by haematopoietic stem cell induced recovery of the immune system are relatively rare and usually not being treated for monetary as well as animal welfare reasons.In contrast, regenerative medicine utilising MSCs for the treatment of acute injuries as well as chronic disorders is gradually turning into clinical routine. Therefore, MSCs from either extra embryonic or adult tissues are in! the focus of attention in veterinary medicine and research. Hence the purpose of this chapter is to offer an overview on basic science and clinical application of MSCs in veterinary medicine. PMID: 20309674 [PubMed - as supplied by publisher] | | |
| Cascades of transcription regulation during liver regeneration.
March 24, 2010 at 6:25 AM
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| | Cascades of transcription regulation during liver regeneration. Int J Biochem Cell Biol. 2010 Mar 19; Authors: Kurinna S, Barton MC An increasing demand for new strategies in cancer prevention and regenerative medicine requires a better understanding of molecular mechanisms that control cell proliferation in tissue-specific manner. Regenerating liver is a unique model allowing use of biochemical, genetic, and engineering tools to uncover molecular mechanisms and improve treatment of hepatic cancers, liver failure, and fibrotic disease. Molecular mechanisms of liver regeneration involve extra- and intracellular factors to activate transcription of genes normally silenced in quiescent liver. While many upstream signaling pathways of the regenerating liver have been extensively studied, our knowledge of the downstream effectors, transcription factors (TFs), remains limited. This review describes consecutive engagement of pre-existing and de novo synthesized TFs, as cascades that regulate expression of growth-related and metabolic genes during liver regeneration after partial hepatectomy in mice. ! Several previously recognized regulators of regenerating liver are described in the light of recently identified co-activator and co-repressor complexes that interact with primary DNA-binding TFs. Published results of gene expression and chromatin immunoprecipitation analyses, as well as studies of transgenic mouse models, are used to emphasize new potential regulators of transcription during liver regeneration. Finally, a more detailed description of newly identified transcriptional regulators of liver regeneration illustrates the tightly regulated balance of proliferative and metabolic responses to partial hepatectomy. PMID: 20307684 [PubMed - as supplied by publisher] | | |
| Bio-Medical Materials and Engineering. Foreword.
March 24, 2010 at 6:25 AM
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| | Bio-Medical Materials and Engineering. Foreword. Biomed Mater Eng. 2009;19(4-5):269 Authors: Stoltz JF, Magdalou J, Netter P, de Isla N PMID: 20042792 [PubMed - indexed for MEDLINE] | | |
| Treatment of full-thickness chondral defects with hyalograft C in the knee: a prospective clinical case series with 2 to 7 years' follow-up.
March 24, 2010 at 6:25 AM
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| | Treatment of full-thickness chondral defects with hyalograft C in the knee: a prospective clinical case series with 2 to 7 years' follow-up. Am J Sports Med. 2009 Nov;37 Suppl 1:81S-87S Authors: Nehrer S, Dorotka R, Domayer S, Stelzeneder D, Kotz R BACKGROUND: Tissue engineering has become available for cartilage repair in clinical practice. HYPOTHESIS: The treatment of full-thickness chondral defects in the knee with a hyaluronan-based scaffold seeded with autologous chondrocytes provides stable improvement of clinical outcome up to 7 years. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Fifty-three patients with deep osteochondral defects in the knee were treated with Hyalograft C. The mean age at implantation was 32 +/- 12 years, the mean defect size was 4.4 +/- 1.9 cm(2), and the mean body mass index was 24.5 +/- 3.8 kg/m(2). Implantations were performed with miniarthrotomy or arthroscopy. The primary indications for implantation with Hyalograft C included young patients with a stable joint, normal knee alignment, and isolated chondral defects with otherwise healthy adjacent cartilage. The secondary indications were patients who did not meet the primary indication criteria or were salvage proc! edures. Forty-two patients with primary indications and 11 patients with secondary indications were evaluated. Outcome was evaluated with the International Cartilage Repair Society and International Knee Documentation Committee scales, the Lysholm score, the modified Cincinnati score, and with Kaplan-Meier survival analysis. Statistical analysis consisted of bivariate correlation analysis and unpaired, 2-tailed t tests. RESULTS: A highly significant increase (P <.001) in all knee scores was found in patients treated for the primary indications. Nine of 11 secondary indication cases underwent total knee arthroplasty due to persisting pain between 2 and 5 years after implantation. Graft failure occurred in 3 of 42 patients with primary indication between 6 months and 5 years after implantation. Kaplan-Meier survival demonstrated significantly different chances for survival between primary and secondary outcome and between simple, complex, and salvage cases, respectively (P! <.001). CONCLUSION: Hyalograft C autograft provides clinic! al impro vement in healthy young patients with single cartilage defects. Less complicated surgery and lower morbidity are considered advantages of the technique. The results of treatment with Hyalograft C as a salvage procedure or in patients with osteoarthritis are poor. PMID: 19861701 [PubMed - indexed for MEDLINE] | | |
| Treatment of symptomatic cartilage defects of the knee: characterized chondrocyte implantation results in better clinical outcome at 36 months in a randomized trial compared to microfracture.
March 24, 2010 at 6:25 AM
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| | Treatment of symptomatic cartilage defects of the knee: characterized chondrocyte implantation results in better clinical outcome at 36 months in a randomized trial compared to microfracture. Am J Sports Med. 2009 Nov;37 Suppl 1:10S-19S Authors: Saris DB, Vanlauwe J, Victor J, Almqvist KF, Verdonk R, Bellemans J, Luyten FP, BACKGROUND: Damaged articular cartilage has limited capacity for self-repair. Autologous chondrocyte implantation using a characterized cell therapy product results in significantly better early structural repair as compared with microfracture in patients with symptomatic joint surface defects of the femoral condyles of the knee. PURPOSE: To evaluate clinical outcome at 36 months after characterized chondrocyte implantation (CCI) versus microfracture (MF). STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: Patients aged 18 to 50 years with single International Cartilage Repair Society (ICRS) grade III/IV symptomatic cartilage defects of the femoral condyles were randomized to CCI (n = 57) or MF (n = 61). Clinical outcome was measured over 36 months by the Knee injury and Osteoarthritis Outcome Score (KOOS). Serial magnetic resonance imaging (MRI) scans were scored using the Magnetic resonance Observation of Cartilage Repair Tissue (MOCART) s! ystem and 9 additional items. Gene expression profile scores associated with ectopic cartilage formation were determined by RT-PCR. RESULTS: Baseline mean overall KOOS (+/-SE) was comparable between the CCI and MF groups (56.30 +/- 1.91 vs 59.46 +/- 1.98, respectively). Mean improvement (+/-SE) from baseline to 36 months in overall KOOS was greater in the CCI group than the MF group (21.25 +/- 3.60 vs 15.83 +/- 3.48, respectively), while in a mixed linear model analysis with time as a categorical variable, significant differences favoring CCI were shown in overall KOOS (P = .048) and the subdomains of Pain (P = .044) and QoL (P = .036). More CCI- than MF-treated patients were treatment responders (83% vs 62%, respectively). In patients with symptom onset of <2 years, the mean improvement (+/-SE) from baseline to 36 months in overall KOOS was greater with CCI than MF (24.98 +/- 4.34 vs 16.50 +/- 3.99, respectively) and even greater in patients with symptom onset of <3 ! years (26.08 +/- 4.10 vs 17.09 +/- 3.77, respectively). Charac! terized chondrocyte implantation patients with high (> or =2) versus low (<2) gene profile scores showed greater improvement from baseline in mean overall KOOS (+/-SE) at 36 months (28.91 +/- 5.69 vs 18.18 +/- 5.08, respectively). Subchondral bone reaction significantly worsened over time with MF compared with CCI (P <.05). CONCLUSION: Characterized chondrocyte implantation for the treatment of articular cartilage defects of the femoral condyles of the knee results in significantly better clinical outcome at 36 months in a randomized trial compared with MF. Time to treatment and chondrocyte quality were shown to affect outcome. PMID: 19846694 [PubMed - indexed for MEDLINE] | | |
| Evaluation of bone tunnel placement for suture augmentation of an injured anterior cruciate ligament: Effects on joint stability in a goat model.
March 24, 2010 at 6:18 AM
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| | Evaluation of bone tunnel placement for suture augmentation of an injured anterior cruciate ligament: Effects on joint stability in a goat model. J Orthop Res. 2010 Mar 22; Authors: Fisher MB, Jung HJ, McMahon PJ, Woo SL Use of novel tissue engineering approaches to heal an injured anterior cruciate ligament (ACL) requires suture repair and/or augmentation to provide joint stability. We evaluated the effects of the location of suture augmentation at the femur and tibia in terms of joint stability using a goat model. Eight goat stifle joints were tested with augmentation sutures placed in two femoral tunnel locations: (1) anterior to, or (2) through the ACL footprint, and two tibial tunnel locations: (1) medial to, or (2) medial and lateral to the footprint. Using a robotic/universal force-moment sensor testing system, the anterior tibial translation (ATT) and the corresponding in situ force carried by the sutures were obtained at 30 degrees , 60 degrees , and 90 degrees of flexion in response to external loads. No significant differences were found between augmentation groups due to tunnel location in terms of ATT or the in situ forces carried by the sutures at all flexion angles ! tested. Similar results were found under 5 N m of varus-valgus torque. Under a 67 N anterior tibial load, the ATT was restored to within 3 mm of the intact joint following suture augmentation (p > 0.05). Suture augmentation, when placed close to the ACL insertion, could be helpful in providing initial joint stability to aid ACL healing in the goat model. J. Orthop. Res. (c) 2010 Orthopaedic Research Society. PMID: 20309958 [PubMed - as supplied by publisher] | | |
| Mechanisms for osteogenic differentiation of human mesenchymal stem cells induced by fluid shear stress.
March 24, 2010 at 6:18 AM
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| | Mechanisms for osteogenic differentiation of human mesenchymal stem cells induced by fluid shear stress. Biomech Model Mechanobiol. 2010 Mar 23; Authors: Liu L, Yuan W, Wang J Mechanical stimuli can improve bone function by promoting the proliferation and differentiation of bone cells and osteoblasts. As precursors of osteoblasts, human mesenchymal stem cells (hMSCs) are sensitive to mechanical stimuli. In recent years, fluid shear stress (FSS) has been widely used as a method of mechanical stimulation in bone tissue engineering to induce the osteogenic differentiation of hMSCs. However, the mechanism of this differentiation is not completely clear. Several signaling pathways are involved in the mechanotransduction of hMSCs responding to FSS, such as MAPK, NO/cGMP/PKG and Ca(2+) signaling pathway. Here, we briefly review how hMSCs respond to fluid flow stimuli and focus on the signal molecules involved in this mechanotransduction. PMID: 20309603 [PubMed - as supplied by publisher] | | |
| In vitro studies of the ablation mechanism of periodontopathic bacteria and decontamination effect on periodontally diseased root surfaces by erbium:yttrium-aluminum-garnet laser.
March 24, 2010 at 6:18 AM
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| | In vitro studies of the ablation mechanism of periodontopathic bacteria and decontamination effect on periodontally diseased root surfaces by erbium:yttrium-aluminum-garnet laser. Lasers Med Sci. 2010 Mar 23; Authors: Akiyama F, Aoki A, Miura-Uchiyama M, Sasaki KM, Ichinose S, Umeda M, Ishikawa I, Izumi Y The erbium:yttrium-aluminum-garnet (Er:YAG) laser is now increasingly used in periodontal therapy. The purpose of this study was to investigate the effect of Er:YAG laser irradiation on the morphology of periodontopathic bacteria and to compare the bacterial elimination effect of the laser and the ultrasonic scaler on diseased root surfaces in vitro. Colonies of Porphyromonas gingivalis were exposed to a single-pulse Er:YAG laser at 40 mJ and were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Also, 20 pairs of periodontally diseased root surfaces with subgingival calculi of freshly extracted teeth were treated by Er:YAG laser scaling at 40 mJ/pulse (14.2 J/cm(2) per pulse) and 10 Hz with water spray or ultrasonic scaling, or were not treated. The efficiency of each treatment was determined as the area treated per second, and the treated surfaces were examined by SEM. The material scraped from the treated root surfaces w! as cultured in aerobic and anaerobic conditions, and the numbers of colony forming units (CFUs) were compared. SEM and TEM showed that the Er:YAG laser had easily ablated the bacterial colony, leaving an ablation spot with a crater and the surrounding affected area showing melted branch-like structures. The laser irradiation was as equally effective and efficient as the ultrasonic scaler in performing root surface debridement. The CFUs after laser treatment were significantly fewer than those after ultrasonic scaling in aerobic and anaerobic culture conditions. Er:YAG laser ablates periodontopathic bacteria with thermal vaporization, and its bacterial elimination effect on the diseased root surfaces appears to be superior to that of the ultrasonic scaler. PMID: 20309597 [PubMed - as supplied by publisher] | | |
| Marrying click chemistry with polymerization: expanding the scope of polymeric materials.
March 24, 2010 at 6:18 AM
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| | Marrying click chemistry with polymerization: expanding the scope of polymeric materials. Chem Soc Rev. 2010 Apr 22;39(4):1338-54 Authors: Golas PL, Matyjaszewski K Click chemistry constitutes a class of reactions broadly characterized by efficiency, selectivity, and tolerance to a variety of solvents and functional groups. By far the most widely utilized of these efficient transformation reactions is the Cu(I)-catalyzed azide-alkyne cycloaddition. This reaction has been creatively employed to facilitate the preparation of complex macromolecules, such as multiblock copolymers, shell or core cross-linked micelles, and dendrimers. This critical review highlights the application of click chemistry, in particular the Cu(I)-catalyzed azide-alkyne cycloaddition, to the synthesis of a wide variety of new materials with possible uses as drug delivery agents, tissue engineering scaffolds, and dispersible nanomaterials (83 references). PMID: 20309490 [PubMed - in process] | | |
| Biphasic calcium sulfate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications: in vitro study.
March 24, 2010 at 6:18 AM
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| | Biphasic calcium sulfate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications: in vitro study. Biomed Mater. 2010 Mar 22;5(2):25006 Authors: Vlad MD, Valle LJ, Poeată I, López J, Torres R, Barracó M, Fernández E In this study, the cytocompatibility of new 'iron-modified/alpha-tricalcium phosphate (IM/alpha-TCP) and calcium sulfate dihydrate (CSD)' bone cement (IM/alpha-TCP/CSD-BC) intended for spinal applications has been approached. The objective was to investigate by direct-contact osteoblast-like cell cultures (from 1 to 14 days) the in vitro cell adhesion, proliferation, morphology and cytoskeleton organization of MG-63 cells seeded onto the new cements. The results were as follows: (a) quantitative MTT-assay and scanning electron microscopy (SEM) showed that cell adhesion, proliferation and viability were not affected with time by the presence of iron in the cements; (b) double immunofluorescent labeling of F-actin and alpha-tubulin showed a dynamic interaction between the cell and its porous substrates sustaining the locomotion phenomenon on the cements' surface, which favored the colonization, and confirming the biocompatibility of the experimental cements; (c) SEM! -cell morphology and cytoskeleton observations also evidenced that MG-63 cells were able to adhere, to spread and to attain normal morphology on the new IM/alpha-TCP/CSD-BC which offered favorable substratum properties for osteoblast-like cells proliferation and differentiation in vitro. The results showed that these new iron-modified cement-like biomaterials have cytocompatible features of interest not only as possible spinal cancellous bone replacement biomaterial but also as bone tissue engineering scaffolds. PMID: 20308776 [PubMed - as supplied by publisher] | | |
| Biomimetic hydroxyapatite-containing composite nanofibrous substrates for bone tissue engineering.
March 24, 2010 at 6:18 AM
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| | Biomimetic hydroxyapatite-containing composite nanofibrous substrates for bone tissue engineering. Philos Transact A Math Phys Eng Sci. 2010 Apr 28;368(1917):2065-81 Authors: Venugopal J, Prabhakaran MP, Zhang Y, Low S, Choon AT, Ramakrishna S The fracture of bones and large bone defects owing to various traumas or natural ageing is a typical type of tissue malfunction. Surgical treatment frequently requires implantation of a temporary or permanent prosthesis, which is still a challenge for orthopaedic surgeons, especially in the case of large bone defects. Mimicking nanotopography of natural extracellular matrix (ECM) is advantageous for the successful regeneration of damaged tissues or organs. Electrospun nanofibre-based synthetic and natural polymer scaffolds are being explored as a scaffold similar to natural ECM for tissue engineering applications. Nanostructured materials are smaller in size falling, in the 1-100 nm range, and have specific properties and functions related to the size of the natural materials (e.g. hydroxyapatite (HA)). The development of nanofibres with nano-HA has enhanced the scope of fabricating scaffolds to mimic the architecture of natural bone tissue. Nanofibrous substrates! supporting adhesion, proliferation, differentiation of cells and HA induce the cells to secrete ECM for mineralization to form bone in bone tissue engineering. Our laboratory (NUSNNI, NUS) has been fabricating a variety of synthetic and natural polymer-based nanofibrous substrates and synthesizing HA for blending and spraying on nanofibres for generating artificial ECM for bone tissue regeneration. The present review is intended to direct the reader's attention to the important subjects of synthetic and natural polymers with HA for bone tissue engineering. PMID: 20308115 [PubMed - in process] | | |
| Novel synthesis strategies for natural polymer and composite biomaterials as potential scaffolds for tissue engineering.
March 24, 2010 at 6:18 AM
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| | Novel synthesis strategies for natural polymer and composite biomaterials as potential scaffolds for tissue engineering. Philos Transact A Math Phys Eng Sci. 2010 Apr 28;368(1917):1981-97 Authors: Ko HF, Sfeir C, Kumta PN Recent developments in tissue engineering approaches frequently revolve around the use of three-dimensional scaffolds to function as the template for cellular activities to repair, rebuild and regenerate damaged or lost tissues. While there are several biomaterials to select as three-dimensional scaffolds, it is generally agreed that a biomaterial to be used in tissue engineering needs to possess certain material characteristics such as biocompatibility, suitable surface chemistry, interconnected porosity, desired mechanical properties and biodegradability. The use of naturally derived polymers as three-dimensional scaffolds has been gaining widespread attention owing to their favourable attributes of biocompatibility, low cost and ease of processing. This paper discusses the synthesis of various polysaccharide-based, naturally derived polymers, and the potential of using these biomaterials to serve as tissue engineering three-dimensional scaffolds is also evaluat! ed. In this study, naturally derived polymers, specifically cellulose, chitosan, alginate and agarose, and their composites, are examined. Single-component scaffolds of plain cellulose, plain chitosan and plain alginate as well as composite scaffolds of cellulose-alginate, cellulose-agarose, cellulose-chitosan, chitosan-alginate and chitosan-agarose are synthesized, and their suitability as tissue engineering scaffolds is assessed. It is shown that naturally derived polymers in the form of hydrogels can be synthesized, and the lyophilization technique is used to synthesize various composites comprising these natural polymers. The composite scaffolds appear to be sponge-like after lyophilization. Scanning electron microscopy is used to demonstrate the formation of an interconnected porous network within the polymeric scaffold following lyophilization. It is also established that HeLa cells attach and proliferate well on scaffolds of cellulose, chitosan or alginate. The synth! esis protocols reported in this study can therefore be used to! manufac ture naturally derived polymer-based scaffolds as potential biomaterials for various tissue engineering applications. PMID: 20308112 [PubMed - in process] | | |
| The role of disc-type crystal shape for micromechanical predictions of elasticity and strength of hydroxyapatite biomaterials.
March 24, 2010 at 6:18 AM
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| | The role of disc-type crystal shape for micromechanical predictions of elasticity and strength of hydroxyapatite biomaterials. Philos Transact A Math Phys Eng Sci. 2010 Apr 28;368(1917):1913-35 Authors: Fritsch A, Hellmich C, Dormieux L The successful design of ceramic bone biomaterials is challenged by two competing requirements: on the one hand, such materials need to be stiff and strong, which would suggest a low porosity (of pore sizes in the 10-100 mum range) to be targeted; on the other hand, bone biomaterials need to be bioactive (in particular vascularized), which suggests a high porosity of such materials. Conclusively, reliable information on how porosity drives the stiffness and strength properties of ceramic bone biomaterials (tissue engineering scaffolds) is of great interest. In this context, mathematical models are increasingly being introduced into the field. Recently, self-consistent continuum micromechanics formulations have turned out as expressedly efficient and reliable tools to predict hydroxyapatite biomaterials' stiffness and strength, as a function of the biomaterial-specific porosity, and of the 'universal' properties of the individual hydroxyapatite crystals: their stif! fness, strength and shape. However, the precise crystal shape can be suitably approximated by specific ellipsoidal shapes: while it was shown earlier that spherical shapes do not lead to satisfactory results, and that acicular shapes are an appropriate choice, we here concentrate on disc-type crystal shape as, besides needles, plates are often reported in micrographs of hydroxyapatite biomaterials. Disc-based model predictions of a substantial set of experimental data on stiffness and strength of hydroxyapatite biomaterials almost attain the quality of the very satisfactory needle-based models. This suggests that, as long as the crystal shape is clearly non-spherical, its precise shape is of secondary importance if stiffness and strength of hydroxyapatite biomaterials are predicted on the basis of continuum micromechanics, from their micromorphology and porosity. PMID: 20308109 [PubMed - in process] | | |
| Vascular tissue engineering by computer-aided laser micromachining.
March 24, 2010 at 6:18 AM
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| | Vascular tissue engineering by computer-aided laser micromachining. Philos Transact A Math Phys Eng Sci. 2010 Apr 28;368(1917):1891-912 Authors: Doraiswamy A, Narayan RJ Many conventional technologies for fabricating tissue engineering scaffolds are not suitable for fabricating scaffolds with patient-specific attributes. For example, many conventional technologies for fabricating tissue engineering scaffolds do not provide control over overall scaffold geometry or over cell position within the scaffold. In this study, the use of computer-aided laser micromachining to create scaffolds for vascular tissue networks was investigated. Computer-aided laser micromachining was used to construct patterned surfaces in agarose or in silicon, which were used for differential adherence and growth of cells into vascular tissue networks. Concentric three-ring structures were fabricated on agarose hydrogel substrates, in which the inner ring contained human aortic endothelial cells, the middle ring contained HA587 human elastin and the outer ring contained human aortic vascular smooth muscle cells. Basement membrane matrix containing vascular end! othelial growth factor and heparin was to promote proliferation of human aortic endothelial cells within the vascular tissue networks. Computer-aided laser micromachining provides a unique approach to fabricate small-diameter blood vessels for bypass surgery as well as other artificial tissues with complex geometries. PMID: 20308108 [PubMed - in process] | | |
| Building off-the-shelf tissue-engineered composites.
March 24, 2010 at 6:18 AM
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| | Building off-the-shelf tissue-engineered composites. Philos Transact A Math Phys Eng Sci. 2010 Apr 28;368(1917):1839-62 Authors: Burg T, Cass CA, Groff R, Pepper M, Burg KJ Rapid advances in technology have created the realistic possibility of personalized medicine. In 2000, Time magazine listed tissue engineering as one of the 'hottest 10 career choices'. However, in the past decade, only a handful of tissue-engineered products were translated to the clinical market and none were financially viable. The reality of complex business planning and the high-investment, high-technology environment was not apparent, and the promise of tissue engineering was overstated. In the meantime, biologists were steadily applying three-dimensional benchtop tissue-culture systems for cellular research, but the systems were gelatinous and thus limited in their ability to facilitate the development of complex tissues. Now, the bioengineering literature has seen an emergence of literature describing biofabrication of tissues and organs. However, if one looks closely, again, the viable products appear distant. 'Rapid' prototyping to reproduce the intricat! e patterns of whole organs using large volumes of cellular components faces daunting challenges. Homogenous forms are being labelled 'tissues', but, in fact, do not represent the heterogeneous structure of the native biological system. In 2003, we disclosed the concept of combining rapid prototyping techniques with tissue engineering technologies to facilitate precision development of heterogeneous complex tissue-test systems, i.e. systems to be used for drug discovery and the study of cellular behaviour, biomedical devices and progression of disease. The focus of this paper is on the challenges we have faced since that time, moving this concept towards reality, using the case of breast tissue as an example. PMID: 20308106 [PubMed - in process] | | |
| Guided Tissue Regeneration in Periapical Surgery.
March 24, 2010 at 6:18 AM
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| | Guided Tissue Regeneration in Periapical Surgery. J Endod. 2010 Apr;36(4):618-625 Authors: Lin L, Chen MY, Ricucci D, Rosenberg PA Tissue regeneration by using membrane barriers and bone grafting materials in periapical surgery is an example of tissue engineering technology. Membrane barriers and/or bone grafts are often used to enhance periapical new bone formation. However, the periapical tissues also consist of the periodontal ligament (PDL) and cementum. For regeneration of the periapical tissues after periapical surgery, one of the important requirements is recruitment and differentiation of progenitor/stem cells into committed pre-osteoblasts, pre-PDL cells, and pre-cementoblasts. Homing of progenitor/stem cells into the wounded periapical tissues is regulated by factors such as stromal cell-derived factor 1, growth factors/cytokines, and by microenvironmental cues such as adhesion molecules and extracellular matrix and associated noncollagenous molecules. Tissue regeneration after injury appears to recapitulate the pathway of normal embryonic tissue development. Multiple tissue regener! ation involves a complex interaction between different cells, extracellular matrix, growth/differentiation factors, and microenvironmental cues. Little is known concerning the biologic mechanisms that regulate temporal and spatial relationship between alveolar bone, PDL, and cementum regeneration during periapical wound healing. Simply applying a membrane barrier and/or bone graft during periapical surgery might not result in complete regeneration of the periapical tissues. It has not been clearly demonstrated that these biomaterials are capable of recruiting progenitor/stem cells and inducing these undifferentiated mesenchymal cells to differentiate into PDL cells and cementoblasts after periapical surgery. PMID: 20307733 [PubMed - as supplied by publisher] | | |
| Chitosan-Poly(lactide-co-glycolide) Microsphere Based Scaffolds for Bone Tissue Engineering: In Vitro Degradation and In Vivo Bone Regeneration Studies.
March 24, 2010 at 6:18 AM
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| | Chitosan-Poly(lactide-co-glycolide) Microsphere Based Scaffolds for Bone Tissue Engineering: In Vitro Degradation and In Vivo Bone Regeneration Studies. Acta Biomater. 2010 Mar 19; Authors: Jiang T, Nukavarapu SP, Deng M, Jabbarzadeh E, Kofron MD, Doty SB, Abdel-Fattah WI, Laurencin CT Natural polymer chitosan and synthetic polymer poly(lactide-co-glycolide) (PLAGA) have been investigated for a variety of tissue engineering applications. We have previously reported the fabrication and in vitro evaluation of a novel chitosan/PLAGA sintered microsphere scaffold for load-bearing bone tissue engineering applications. In this study, the in vitro degradation characteristics of the chitosan/PLAGA scaffold and the in vivo bone formation capacity of the chitosan/PLAGA based scaffolds in a rabbit ulnar critical sized defect model were investigated. The chitosan/PLAGA scaffold showed slower degradation than the PLAGA scaffold in vitro. Although chitosan/PLAGA scaffold showed a gradual decrease in compressive properties during the 12-week degradation period, the compressive strength and compressive modulus remained in the range of human trabecular bone. Chitosan/PLAGA based scaffolds were able to guide bone formation in a rabbit ulnar critical sized defect ! model. Microcomputed tomography analysis demonstrated that successful bridging of the critical sized defect on the sides both adjacent to and away from the radius occurred using chitosan/PLAGA based scaffolds. Immobilization of heparin and recombinant human bone morphogenetic protein-2 on the chitosan/PLAGA scaffold surface promoted early bone formation as evidenced by complete bridging of the defect along the radius and significantly enhanced mechanical properties when compared to the chitosan/PLAGA scaffold. Furthermore, histological analysis suggested that chitosan/PLAGA based scaffolds supported normal bone formation via intramembranous formation. PMID: 20307694 [PubMed - as supplied by publisher] | | |
| "Encapsulation of fibroblasts causes accelerated alginate hydrogel degradation"
March 24, 2010 at 6:18 AM
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| | "Encapsulation of fibroblasts causes accelerated alginate hydrogel degradation" Acta Biomater. 2010 Mar 19; Authors: Hunt NC, Smith AM, Gbureck U, Shelton RM, Grover LM Calcium-alginate hydrogel has been widely studied as a material for cell encapsulation for tissue engineering. At present, the effect that cells have on the degradation of alginate hydrogel is largely unknown. We have shown that fibroblasts encapsulated at a density of 7.5 x 10(5) cells/ml in both 2 and 5%w/v alginate remain viable for at least 60 days. Rheological analysis was used to study how the mechanical properties exhibited by alginate hydrogel changed during 28 days in vitro culture. Alginate degradation was shown to occur throughout the study but was greatest within the first 7 days of culture for all samples, which correlated with a sharp release of calcium ions from the construct. Fibroblasts were shown to increase the rate of degradation during the first 7 days when compared with acellular samples in both 2% and 5%w/v gels, but after 28 days both acellular and cell-encapsulating samples retained disc-shaped morphologies and gel-like spectra. The result! s demonstrate that although at an early stage cells influence the mechanical properties of encapsulating alginate, over a longer period of culture, the hydrogels retain sufficient mechanical integrity to exhibit gel-like properties. This allows sustained immobilisation of the cells at the desired location in vivo where they can produce extracellular matrix and growth factors to expedite the healing process. PMID: 20307693 [PubMed - as supplied by publisher] | | |
| Covalently Attached, Silver-Doped Poly(vinyl alcohol) Hydrogel Films on Poly(l-lactic acid).
March 24, 2010 at 6:18 AM
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| | Covalently Attached, Silver-Doped Poly(vinyl alcohol) Hydrogel Films on Poly(l-lactic acid). Biomacromolecules. 2010 Mar 22; Authors: Zan X, Kozlov M, McCarthy TJ, Su Z Covalently attached, soft poly(vinyl alcohol) (PVA) hydrogel films containing silver particles were prepared on solid biodegradable poly(l-lactic acid) (PLLA) samples by a multistep procedure involving oxygen plasma treatment, UV-initiated graft polymerization, and chemical grafting methods. The modification steps were followed and verified using attenuated total reflection infrared spectroscopy and X-ray photoelectron spectroscopy. 2-Hydroxyethyl methacrylate (HEMA) was graft polymerized from the surface of oxygen plasma-treated PLLA film samples and the alcohol functionality in the grafted polyHEMA chains was oxidized using pyridinium dichromate to obtain an aldehyde-rich surface. PVA was then grafted onto this surface using acid catalysis (acetal formation). The "freeze/thaw method" was used to form a PVA hydrogel layer that incorporated the covalently grafted PVA chains in the physically cross-linked gel. This composite film (PLLA-PVA(gel)) was doped with silv! er ions, which were reduced to silver using NaBH(4). Scanning electron microscopy of cross sections of PLLA-PVA(gel) indicates robust attachment of the PVA hydrogel layer to the PLLA film. PLLA-PVA(gel/Ag(0)) film samples exhibit both antibacterial and reduced cell adhesion properties due to the antibacterial properties of silver nanoparticles and high water content, respectively. This method provides a route to mechanically sound biodegradable materials with tunable soft material surface properties. Potential applications in tissue engineering and biomedical devices are envisioned. PMID: 20307097 [PubMed - as supplied by publisher] | | |
| A mass separation of chondrocytes from cartilage tissue utilizing an automatic crushing device.
March 24, 2010 at 6:18 AM
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| | A mass separation of chondrocytes from cartilage tissue utilizing an automatic crushing device. J Biosci Bioeng. 2010 Jan;109(1):73-4 Authors: Takagi M, Yoshioka H, Wakitani S Porcine articular cartilage tissue was crushed using Multi-Beads-Shocker() and digested with trypsin and collagenase type II. Chondrocyte cell yield was maximized by automatic crushing for 10 s, which was 4 times that by manual dicing with a surgical blade and might be useful for the automation of the cell processing. PMID: 20129086 [PubMed - indexed for MEDLINE] | | | | 
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