@article{WagenbrennerPokerHeinzetal.2022,
  author    = {Wagenbrenner, Mike and Poker, Konrad and Heinz, Tizian and Herrmann, Marietta and Horas, Konstantin and Ebert, Regina and Mayer-Wagner, Susanne and Holzapfel, Boris M. and Rudert, Maximilian and Steinert, Andre F. and Weißenberger, Manuel},
  title     = {Mesenchymal stromal cells (MSCs) isolated from various tissues of the human arthritic knee joint possess similar multipotent differentiation potential},
  series = {Applied Sciences},
  volume    = {12},
  journal   = {Applied Sciences},
  number    = {4},
  issn      = {2076-3417},
  doi       = {10.3390/app12042239},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-262334},
  year      = {2022},
  abstract  = {(1) Background: The mesenchymal stromal cells (MSCs) of different tissue origins are applied in cell-based chondrogenic regeneration. However, there is a lack of comparability determining the most suitable cell source for the tissue engineering (TE) of cartilage. The purpose of this study was to compare the in vitro chondrogenic potential of MSC-like cells from different tissue sources (bone marrow, meniscus, anterior cruciate ligament, synovial membrane, and the infrapatellar fat pad removed during total knee arthroplasty (TKA)) and define which cell source is best suited for cartilage regeneration. (2) Methods: MSC-like cells were isolated from five donors and expanded using adherent monolayer cultures. Differentiation was induced by culture media containing specific growth factors. Transforming growth factor (TGF)-ß1 was used as the growth factor for chondrogenic differentiation. Osteogenesis and adipogenesis were induced in monolayer cultures for 27 days, while pellet cell cultures were used for chondrogenesis for 21 days. Control cultures were maintained under the same conditions. After, the differentiation period samples were analyzed, using histological and immunohistochemical staining, as well as molecularbiological analysis by RT-PCR, to assess the expression of specific marker genes. (3) Results: Plastic-adherent growth and in vitro trilineage differentiation capacity of all isolated cells were proven. Flow cytometry revealed the clear co-expression of surface markers CD44, CD73, CD90, and CD105 on all isolated cells. Adipogenesis was validated through the formation of lipid droplets, while osteogenesis was proven by the formation of calcium deposits within differentiated cell cultures. The formation of proteoglycans was observed during chondrogenesis in pellet cultures, with immunohistochemical staining revealing an increased relative gene expression of collagen type II. RT-PCR proved an elevated expression of specific marker genes after successful differentiation, with no significant differences regarding different cell source of native tissue. (4) Conclusions: Irrespective of the cell source of native tissue, all MSC-like cells showed multipotent differentiation potential in vitro. The multipotent differentiation capacity did not differ significantly, and chondrogenic differentiation was proven in all pellet cultures. Therefore, cell suitability for cell-based cartilage therapies and tissue engineering is given for various tissue origins that are routinely removed during total knee arthroplasty (TKA). This study might provide essential information for the clinical tool of cell harvesting, leading to more flexibility in cell availability.},
  language  = {en}
}
@article{EidmannEwaldBoelchetal.2021,
  author    = {Eidmann, Annette and Ewald, Andrea and Boelch, Sebastian P. and Rudert, Maximilian and Holzapfel, Boris M. and Stratos, Ioannis},
  title     = {In vitro evaluation of antibacterial efficacy of vancomycin-loaded suture tapes and cerclage wires},
  series = {Journal of Materials Science: Materials in Medicine},
  volume    = {32},
  journal   = {Journal of Materials Science: Materials in Medicine},
  number    = {4},
  doi       = {10.1007/s10856-021-06513-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260089},
  pages     = {42},
  year      = {2021},
  abstract  = {Usage of implants containing antibiotic agents has been a common strategy to prevent implant related infections in orthopedic surgery. Unfortunately, most implants with microbial repellent properties are characterized by accessibility limitations during daily clinical practice. Aim of this in vitro study was to investigate whether suture tapes and cerclage wires, which were treated with vancomycin, show a sustainable antibacterial activity. For this purpose, we used 24 stainless steel wire cerclages and 24 ultra-high molecular weight polyethylene and polyester suture tape test bodies. The test bodies were incubated for 30 min. in 100 mg/ml vancomycin solution or equivalent volumes of 0.9\% NaCl. After measuring the initial solution uptake of the test bodies, antibacterial efficacy via agar diffusion test with Staphylococcus aureus and vancomycin elution tests were performed 1, 2, 3, and 6 days after incubation. Vancomycin-loaded tapes as well as vancomycin-loaded cerclage wires demonstrated increased bacterial growth inhibition when compared to NaCl-treated controls. Vancomycin-loaded tapes showed an additional twofold and eightfold increase of bacterial growth inhibition compared to vancomycin-loaded wires at day 1 and 2, respectively. Elution tests at day 1 revealed high levels of vancomycin concentration in vancomycin loaded tapes and wires. Additionally, the concentration in vancomycin loaded tapes was 14-fold higher when compared to vancomycin loaded wires. Incubating suture tapes and cerclage wires in vancomycin solution showed a good short-term antibacterial activity compared to controls. Considering the ease of vancomycin application on suture tapes or wires, our method could represent an attractive therapeutic strategy in biofilm prevention in orthopedic surgery.},
  language  = {en}
}
@article{ArnholdtKamawalHorasetal.2020,
  author    = {Arnholdt, J{\"o}rg and Kamawal, Yama and Horas, Konstantin and Holzapfel, Boris M. and Gilbert, Fabian and Ripp, Axel and Rudert, Maximilian and Steinert, Andre F.},
  title     = {Accurate implant fit and leg alignment after cruciate-retaining patient-specific total knee arthroplasty},
  series = {BMC Musculoskeletal Disorders},
  volume    = {21},
  journal   = {BMC Musculoskeletal Disorders},
  doi       = {10.1186/s12891-020-03707-2},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230012},
  year      = {2020},
  abstract  = {Background For improved outcomes in total knee arthroplasty (TKA) correct implant fitting and positioning are crucial. In order to facilitate a best possible implant fitting and positioning patient-specific systems have been developed. However, whether or not these systems allow for better implant fitting and positioning has yet to be elucidated. For this reason, the aim was to analyse the novel patient-specific cruciate retaining knee replacement system iTotal (TM) CR G2 that utilizes custom-made implants and instruments for its ability to facilitate accurate implant fitting and positioning including correction of the hip-knee-ankle angle (HKA). Methods We assessed radiographic results of 106 patients who were treated with the second generation of a patient-specific cruciate retaining knee arthroplasty using iTotal\(^{TM}\) CR G2 (ConforMIS Inc.) for tricompartmental knee osteoarthritis (OA) using custom-made implants and instruments. The implant fit and positioning as well as the correction of the mechanical axis (hip-knee-ankle angle, HKA) and restoration of the joint line were determined using pre- and postoperative radiographic analyses. Results On average, HKA was corrected from 174.4 degrees +/- 4.6 degrees preoperatively to 178.8 degrees +/- 2.2 degrees postoperatively and the coronal femoro-tibial angle was adjusted on average 4.4 degrees. The measured preoperative tibial slope was 5.3 degrees +/- 2.2 degrees (mean +/- SD) and the average postoperative tibial slope was 4.7 degrees +/- 1.1 degrees on lateral views. The joint line was well preserved with an average modified Insall-Salvati index of 1.66 +/- 0.16 pre- and 1.67 +/- 0.16 postoperatively. The overall accuracy of fit of implant components was decent with a measured medial overhang of more than 1 mm (1.33 mm +/- 0.32 mm) in 4 cases only. Further, a lateral overhang of more than 1 mm (1.8 mm +/- 0.63) (measured in the anterior-posterior radiographs) was observed in 11 cases, with none of the 106 patients showing femoral notching. Conclusion The patient-specific iTotal\(^{TM}\) CR G2 total knee replacement system facilitated a proper fitting and positioning of the implant components. Moreover, a good restoration of the leg axis towards neutral alignment was achieved as planned. Nonetheless, further clinical follow-up studies are necessary to validate our findings and to determine the long-term impact of using this patient- specific system.},
  language  = {en}
}
@article{WeissenbergerWeissenbergerWagenbrenneretal.2020,
  author    = {Weissenberger, Manuel and Weissenberger, Manuela H. and Wagenbrenner, Mike and Heinz, Tizian and Reboredo, Jenny and Holzapfel, Boris M. and Rudert, Maximilian and Groll, J{\"u}rgen and Evans, Christopher H. and Steinert, Andre F.},
  title     = {Different types of cartilage neotissue fabricated from collagen hydrogels and mesenchymal stromal cells via SOX9, TGFB1 or BMP2 gene transfer},
  series = {PLoS One},
  volume    = {15},
  journal   = {PLoS One},
  number    = {8},
  doi       = {10.1371/journal.pone.0237479},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230494},
  year      = {2020},
  abstract  = {Objective As native cartilage consists of different phenotypical zones, this study aims to fabricate different types of neocartilage constructs from collagen hydrogels and human mesenchymal stromal cells (MSCs) genetically modified to express different chondrogenic factors. Design Human MSCs derived from bone-marrow of osteoarthritis (OA) hips were genetically modified using adenoviral vectors encoding sex-determining region Y-type high-mobility-group-box (SOX)9,transforming growth factor beta (TGFB) 1or bone morphogenetic protein (BMP) 2cDNA, placed in type I collagen hydrogels and maintained in serum-free chondrogenic media for three weeks. Control constructs contained unmodified MSCs or MSCs expressing GFP. The respective constructs were analyzed histologically, immunohistochemically, biochemically, and by qRT-PCR for chondrogenesis and hypertrophy. Results Chondrogenesis in MSCs was consistently and strongly induced in collagen I hydrogels by the transgenesSOX9,TGFB1andBMP2as evidenced by positive staining for proteoglycans, chondroitin-4-sulfate (CS4) and collagen (COL) type II, increased levels of glycosaminoglycan (GAG) synthesis, and expression of mRNAs associated with chondrogenesis. The control groups were entirely non-chondrogenic. The levels of hypertrophy, as judged by expression of alkaline phosphatase (ALP) and COL X on both the protein and mRNA levels revealed different stages of hypertrophy within the chondrogenic groups (BMP2>TGFB1>SOX9). Conclusions Different types of neocartilage with varying levels of hypertrophy could be generated from human MSCs in collagen hydrogels by transfer of genes encoding the chondrogenic factorsSOX9,TGFB1andBMP2. This technology may be harnessed for regeneration of specific zones of native cartilage upon damage.},
  language  = {en}
}
@article{HorasvanHerckMaieretal.2020,
  author    = {Horas, Konstantin and van Herck, Ulrike and Maier, Gerrit S. and Maus, Uwe and Harrasser, Norbert and Jakob, Franz and Weissenberger, Manuel and Arnholdt, J{\"o}rg and Holzapfel, Boris M. and Rudert, Maximilian},
  title     = {Does vitamin D deficiency predict tumour malignancy in patients with bone tumours? Data from a multi-center cohort analysis},
  series = {Journal of Bone Oncology},
  volume    = {25},
  journal   = {Journal of Bone Oncology},
  doi       = {10.1016/j.jbo.2020.100329},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230314},
  year      = {2020},
  abstract  = {Vitamin D deficiency is a global health concern that is estimated to afflict over one billion people globally. The major role of vitamin D is that of a regulator of calcium and phosphate metabolism, thus, being essential for proper bone mineralisation. Concomitantly, vitamin D is known to exert numerous extra-skeletal actions. For example, it has become evident that vitamin D has direct anti-proliferative, pro-differentiation and pro-apoptotic actions on cancer cells. Hence, vitamin D deficiency has been associated with increased cancer risk and worse prognosis in several malignancies. We have recently demonstrated that vitamin D deficiency promotes secondary cancer growth in bone. These findings were partly attributable to an increase in bone remodelling but also through direct effects of vitamin D on cancer cells. To date, very little is known about vitamin D status of patients with bone tumours in general. Thus, the objective of this study was to assess vitamin D status of patients with diverse bone tumours. Moreover, the aim was to elucidate whether or not there is an association between pre-diagnostic vitamin D status and tumour malignancy in patients with bone tumours. In a multi-center analysis, 25(OH)D, PTH and calcium levels of 225 patients that presented with various bone tumours between 2017 and 2018 were assessed. Collectively, 76\% of all patients had insufficient vitamin D levels with a total mean 25(OH)D level of 21.43 ng/ml (53.58 nmol/L). In particular, 52\% (117/225) of patients were identified as vitamin D deficient and further 24\% of patients (55/225) were vitamin D insufficient. Notably, patients diagnosed with malignant bone tumours had significantly lower 25(OH)D levels than patients diagnosed with benign bone tumours [19.3 vs. 22.75 ng/ml (48.25 vs. 56.86 nmol/L); p = 0.04). In conclusion, we found a widespread and distressing rate of vitamin D deficiency and insufficiency in patients with bone tumours. However, especially for patients with bone tumours sufficient vitamin D levels seem to be of great importance. Thus, we believe that 25(OH)D status should routinely be monitored in these patients. Collectively, there should be an increased awareness for physicians to assess and if necessary correct vitamin D status of patients with bone tumours in general or of those at great risk of developing bone tumours.},
  language  = {en}
}
@article{WagenbrennerHeinzHorasetal.2020,
  author    = {Wagenbrenner, Mike and Heinz, Tizian and Horas, Konstantin and Jakuscheit, Axel and Arnholdt, J{\"o}rg and Hermann, Marietta and Rudert, Maximilian and Holzapfel, Boris M. and Steinert, Andre F. and Weißenberger, Manuel},
  title     = {The human arthritic hip joint is a source of mesenchymal stromal cells (MSCs) with extensive multipotent differentiation potential},
  series = {BMC Musculoskeletal Disorders},
  volume    = {21},
  journal   = {BMC Musculoskeletal Disorders},
  number    = {1},
  doi       = {10.1186/s12891-020-03340-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229497},
  year      = {2020},
  abstract  = {Background While multiple in vitro studies examined mesenchymal stromal cells (MSCs) derived from bone marrow or hyaline cartilage, there is little to no data about the presence of MSCs in the joint capsule or the ligamentum capitis femoris (LCF) of the hip joint. Therefore, this in vitro study examined the presence and differentiation potential of MSCs isolated from the bone marrow, arthritic hyaline cartilage, the LCF and full-thickness samples of the anterior joint capsule of the hip joint. Methods MSCs were isolated and multiplied in adherent monolayer cell cultures. Osteogenesis and adipogenesis were induced in monolayer cell cultures for 21 days using a differentiation medium containing specific growth factors, while chondrogenesis in the presence of TGF-ss1 was performed using pellet-culture for 27 days. Control cultures were maintained for comparison over the same duration of time. The differentiation process was analyzed using histological and immunohistochemical stainings as well as semiquantitative RT-PCR for measuring the mean expression levels of tissue-specific genes. Results This in vitro research showed that the isolated cells from all four donor tissues grew plastic-adherent and showed similar adipogenic and osteogenic differentiation capacity as proven by the histological detection of lipid droplets or deposits of extracellular calcium and collagen type I. After 27 days of chondrogenesis proteoglycans accumulated in the differentiated MSC-pellets from all donor tissues. Immunohistochemical staining revealed vast amounts of collagen type II in all differentiated MSC-pellets, except for those from the LCF. Interestingly, all differentiated MSCs still showed a clear increase in mean expression of adipogenic, osteogenic and chondrogenic marker genes. In addition, the examination of an exemplary selected donor sample revealed that cells from all four donor tissues were clearly positive for the surface markers CD44, CD73, CD90 and CD105 by flow cytometric analysis. Conclusions This study proved the presence of MSC-like cells in all four examined donor tissues of the hip joint. No significant differences were observed during osteogenic or adipogenic differentiation depending on the source of MSCs used. Further research is necessary to fully determine the tripotent differentiation potential of cells isolated from the LCF and capsule tissue of the hip joint.},
  language  = {en}
}
@article{JakubietzSchmidtHolzapfeletal.2020,
  author    = {Jakubietz, Rafael G. and Schmidt, Karsten and Holzapfel, Boris M. and Meffert, Rainer H. and Jakubietz, Michael G.},
  title     = {Pedicled perforator flaps for mid-tibial soft tissue reconstruction in medically compromised patients},
  series = {JPRAS Open},
  volume    = {24},
  journal   = {JPRAS Open},
  doi       = {10.1016/j.jpra.2020.02.002},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229473},
  pages     = {47-55},
  year      = {2020},
  abstract  = {Background: The soft tissue of the central pretibial area is difficult to reconstruct often requiring free tissue transfer. Especially medi- cally compromised patients are not ideal candidates for free tissue transfer and may benefit from expeditiously harvested local flaps with limited donor site morbidity. As muscle flaps are rare, pedi- cled flaps based on lateral perforators represent an alternative as the arc of rotation can often be limited to 90 °. Material and Methods: A retrospective analysis of patient data was conducted to identify patients over the age of 60 years with comor- bidities that underwent pretibial soft tissue reconstruction with a single-pedicle perforator flap. Patient demographics, size and cause of the defect, flap dimension, arc of rotation and complications were recorded. Results: Five patients with an average age of 71.4 years were in- cluded. The arc of rotation was 69 °, all flaps healed. There were two recurrences of osteomyelitis. Conclusion: Lateral perforators originating from the anterior tib- ial artery or peroneal artery are adequate source vessels for single pedicled perforator flaps even in medically compromised patients. A perforator located proximal to the defect allows limiting the arcof rotation to less than 90 °, which increases the safety of the flap. Patients benefit from a simple procedure without a microvascular anastomosis and a donor site confined to one extremity},
  language  = {en}
}
@article{WagenbrennerHeinzHorasetal.2020,
  author    = {Wagenbrenner, Mike and Heinz, Tizian and Horas, Konstantin and Jakuscheit, Axel and Arnholdt, Joerg and Mayer-Wagner, Susanne and Rudert, Maximilian and Holzapfel, Boris M. and Weißenberger, Manuel},
  title     = {Impact of Tranexamic Acid on Chondrocytes and Osteogenically Differentiated Human Mesenchymal Stromal Cells (hMSCs) In Vitro},
  series = {Journal of Clinical Medicine},
  volume    = {9},
  journal   = {Journal of Clinical Medicine},
  number    = {12},
  issn      = {2077-0383},
  doi       = {10.3390/jcm9123880},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219410},
  year      = {2020},
  abstract  = {The topical application of tranexamic acid (TXA) helps to prevent post-operative blood loss in total joint replacements. Despite these findings, the effects on articular and periarticular tissues remain unclear. Therefore, this in vitro study examined the effects of varying exposure times and concentrations of TXA on proliferation rates, gene expression and differentiation capacity of chondrocytes and human mesenchymal stromal cells (hMSCs), which underwent osteogenic differentiation. Chondrocytes and hMSCs were isolated and multiplied in monolayer cell cultures. Osteogenic differentiation of hMSCs was induced for 21 days using a differentiation medium containing specific growth factors. Cell proliferation was analyzed using ATP assays. Effects of TXA on cell morphology were examined via light microscopy and histological staining, while expression levels of tissue-specific genes were measured using semiquantitative RT-PCR. After treatment with 50 mg/mL of TXA, a decrease in cell proliferation rates was observed. Furthermore, treatment with concentrations of 20 mg/mL of TXA for at least 48 h led to a visible detachment of chondrocytes. TXA treatment with 50 mg/mL for at least 24 h led to a decrease in the expression of specific marker genes in chondrocytes and osteogenically differentiated hMSCs. No significant effects were observed for concentrations beyond 20 mg/mL of TXA combined with exposure times of less than 24 h. This might therefore represent a safe limit for topical application in vivo. Further research regarding in vivo conditions and effects on hMSC functionality are necessary to fully determine the effects of TXA on articular and periarticular tissues.},
  language  = {en}
}
@article{ThibaudeauTaubenbergerTheodoropoulosetal.2015,
  author    = {Thibaudeau, Laure and Taubenberger, Anna V. and Theodoropoulos, Christina and Holzapfel, Boris M. and Ramuz, Olivier and Straub, Melanie and Hutmacher, Dietmar W.},
  title     = {New mechanistic insights of integrin β1 in breast cancer bone colonization},
  series = {Oncotarget},
  volume    = {6},
  journal   = {Oncotarget},
  number    = {1},
  doi       = {10.18632/oncotarget.2788},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-175432},
  pages     = {332-344},
  year      = {2015},
  abstract  = {Bone metastasis is a frequent and life-threatening complication of breast cancer. The molecular mechanisms supporting the establishment of breast cancer cells in the skeleton are still not fully understood, which may be attributed to the lack of suitable models that interrogate interactions between human breast cancer cells and the bone microenvironment. Although it is well-known that integrins mediate adhesion of malignant cells to bone extracellular matrix, their role during bone colonization remains unclear. Here, the role of β1 integrins in bone colonization was investigated using tissue-engineered humanized in vitro and in vivo bone models. In vitro, bone-metastatic breast cancer cells with suppressed integrin β1 expression showed reduced attachment, spreading, and migration within human bone matrix compared to control cells. Cell proliferation in vitro was not affected by β1 integrin knockdown, yet tumor growth in vivo within humanized bone microenvironments was significantly inhibited upon β1 integrin suppression, as revealed by quantitative in/ex vivo fluorescence imaging and histological analysis. Tumor cells invaded bone marrow spaces in the humanized bone and formed osteolytic lesions; osteoclastic bone resorption was, however, not reduced by β1 integrin knockdown. Taken together, we demonstrate that β1 integrins have a pivotal role in bone colonization using unique tissue-engineered humanized bone models.},
  language  = {en}
}
@article{ThibaudeauTaubenbergerHolzapfeletal.2014,
  author    = {Thibaudeau, Laure and Taubenberger, Anna V. and Holzapfel, Boris M. and Quent, Verena M. and Fuehrmann, Tobias and Hesami, Parisa and Brown, Toby D. and Dalton, Paul D. and Power, Carl A. and Hollier, Brett G. and Hutmacher, Dietmar W.},
  title     = {A tissue-engineered humanized xenograft model of human breast cancer metastasis to bone},
  series = {Disease Models \& Mechanisms},
  volume    = {7},
  journal   = {Disease Models \& Mechanisms},
  number    = {2},
  doi       = {10.1242/dmm.014076},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-117466},
  pages     = {299-309},
  year      = {2014},
  abstract  = {The skeleton is a preferred homing site for breast cancer metastasis. To date, treatment options for patients with bone metastases are mostly palliative and the disease is still incurable. Indeed, key mechanisms involved in breast cancer osteotropism are still only partially understood due to the lack of suitable animal models to mimic metastasis of human tumor cells to a human bone microenvironment. In the presented study, we investigate the use of a human tissue-engineered bone construct to develop a humanized xenograft model of breast cancer-induced bone metastasis in a murine host. Primary human osteoblastic cell-seeded melt electrospun scaffolds in combination with recombinant human bone morphogenetic protein 7 were implanted subcutaneously in non-obese diabetic/severe combined immunodeficient mice. The tissue-engineered constructs led to the formation of a morphologically intact 'organ' bone incorporating a high amount of mineralized tissue, live osteocytes and bone marrow spaces. The newly formed bone was largely humanized, as indicated by the incorporation of human bone cells and human-derived matrix proteins. After intracardiac injection, the dissemination of luciferase-expressing human breast cancer cell lines to the humanized bone ossicles was detected by bioluminescent imaging. Histological analysis revealed the presence of metastases with clear osteolysis in the newly formed bone. Thus, human tissue-engineered bone constructs can be applied efficiently as a target tissue for human breast cancer cells injected into the blood circulation and replicate the osteolytic phenotype associated with breast cancer-induced bone lesions. In conclusion, we have developed an appropriate model for investigation of species-specific mechanisms of human breast cancer-related bone metastasis in vivo.},
  language  = {en}
}