Andreas Gröger

Humboldt University of Berlin, Berlin, Land Berlin, Germany

Are you Andreas Gröger?

Claim your profile

Publications (9)22.82 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: In der rekonstruktiven Chirurgie könnte neben der etablierten Methode der autogenen Knorpeltransplantation das Tissue engineering humaner Knorpelgewebe zunehmend an Bedeutung gewinnen. Resorptive Mechanismen können jedoch bei beiden Methoden zu funktionell und kosmetisch unbefriedigenden Ergebnissen führen. Unter den heute zur Verfügung stehenden Verfahren der Gewebeprotektion könnte die Polyelektrolytmembranverkapselung mit Natriumzellulosesulfat und Polydialylldimethylammoniumchlorid einen ausreichenden Schutz vor resorptiven Einflüssen gewährleisten. Humaner nativer Nasenseptumknorpel wurde verkapselt (Gruppe 1) und unverkapselt (Gruppe 2) subkutan in thymusaplastische Nacktmäuse implantiert. Die Transplantate wurden nach 1, 4, 8, 12 und 16 Wochen explantiert und histologisch sowie rasterelektronenmikroskopisch untersucht. Gruppe 1 zeigte über den gesamten Implantationszeitraum keinerlei Resorptionsmerkmale bei vollständig erhaltener Knorpelgrundsubstanz. Gruppe 2 hingegen zeigte, korrelierend mit der Implantationsdauer, in zunehmendem Maße Knorpelzellnekrosen und einen bindegewebigen Umbau im Sinne einer Resorption. Die Polyelektrolytmembranverkapselung könnte somit eine sichere Methode zum Schutz humaner Knorpeltransplantate vor resorptiven Einflüssen darstellen. Für den Plastisch-rekonstruktiven Chirurgen wird hierdurch das gewünschte kosmetische und funktionelle Ergebnis kalkulierbarer. In reconstruction of cartilage defects, autogenous transplantation is known as a reliable and experienced method. Although a clinical application has not been reported until now, tissue engineering permits in vitro production of autogenous cartilage transplants. Nevertheless, in both methods the cartilage is exposed to individually varying resorptive mechanisms. Among other methods for in vivo tissue protection, the encapsulation with a semipermeable polyelectrolytecomplex membrane could guarantee sufficient protection against resorptive influences. Human septal cartilage was encapsulated (group 1) with polyelectrolytecomplex membranes and subcutaneously implanted on the back of thymusaplastic nude mice. Cartilage implants without encapsulation (group 2) were used as control. Scanning electron microscopy and histochemical investigations were performed 1, 4, 8, 12 and 16 weeks after implantation. Group 1 showed no signs of resorption and chronic inflammation at all. In contrast, group 2 presented, correlating to the time of implanta-tion, increasing signs of cell death and fibrotic transformation, representing an increased activity of resorption. In conclusion, tissue encapsulation with a polyelectrolytecomplex membrane could ensure a sufficient protection of human cartilage transplants from resorptive influences. For the plastic-reconstructive surgeon the desired result becomes more calculable.
    HNO 04/2012; 48(2):119-124. · 0.42 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: The purpose of the study was to examine the morphology and biomechanical characteristics of in vivo cultured tissue-engineered human septal cartilage as a prospective autogenous transplant material for subcutaneous implantation in reconstructive procedures. Chondrocytes were enzymatically isolated from human septal cartilage biopsies. The cell number was expanded in monolayer culture. Chondrocytes were then fixed on a non-woven poly-lactide-poly-glycolide (PGLA) polymer scaffold by means of fibrin glue. The PGLA-polymer construct was implanted subcutaneously on the back of athymic mice and allowed to mature for 6 or 12 weeks. After killing the mice, the formed cartilage was tested on a material testing machine with a highly standardized reproducible setting. Biomechanical testing consisted of an indentation test, which revealed the failure load and compressive modulus of the neocartilage. The failure load shows the upper limit of supported stress. The compressive modulus is a measure of the templates' stiffness. After testing, the templates were histologically stained. Native human septal cartilage served as a control group. Histological and macroscopic examination showed cartilage formation of a hyaline-like morphology. Histological staining revealed the synthesis of abundant mucopolysaccharid matrix. The biomechanical characteristics of neocartilage proved to be of no statistical difference compared to native human septal cartilage. The failure load and compressive modulus were initially somewhat lower and reached the control group's results after 12 weeks in-vivo. Summarizing, tissue engineered nasal cartilage matches typical mechanical characteristics of native hyaline cartilage. Its elasticity and failure load are of sufficient quality to meet the clinical requirements for reconstructive surgery.
    Archiv für Klinische und Experimentelle Ohren- Nasen- und Kehlkopfheilkunde 01/2006; 262(12):993-7. · 1.46 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Functional organ or tissue failure is one of the most frequent, devastating and costly problems in modern health care. The field of tissue engineering has tremendous potential for developing new functional tissue. In reconstructive surgery, cartilage engineering could be a serious alternative to the established method of autologous cartilage transplantation. Recent studies demonstrate cartilage engineering by subcutaneous implantation of chondrocyte-seeded PGA/PLA-fibrin glue scaffolds in the backs of nude mice. In both autologous cartilage transplantation and cartilage engineering, the host immune response affects transplant integrity and cartilage morphology to an unforeseeable extent. To investigate whether polyelectrolyte complex (PEC) membranes can prevent rejection of cartilage transplants without neglecting tissue metabolism, tissue-engineered cartilage encapsulated with a PEC membrane was subcutaneously implanted in the backs of nude mice. Non-encapsulated tissue-engineered cartilage was used for the control group. Histochemistry and scanning electron microscopy were performed 4 and 12 weeks after implantation. There was no interaction between the host and the implant with an intact PEC membrane. With protection by PEC encapsulation, implanted tissue-engineered cartilage showed no signs of degeneration and had a significantly weaker cellular immune response than without it. Thus, PEC membrane encapsulation appears to be a novel approach for protecting cartilage implants from host immune response after autologous transplantation.
    Archiv für Klinische und Experimentelle Ohren- Nasen- und Kehlkopfheilkunde 05/2005; 262(4):338-44. · 1.46 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Subcutaneously implanted, in vitro engineered tissue is generally affected by the immune system of the host even in autogenous transplantation. The aim of this study was to investigate immunomodulation of subcutaneously implanted tissue-engineered cartilage transplants by intramuscular methylprednisolone application. Transplants consisted of auricular rabbit chondrocytes, polylactide-polyglycolide co-polymer fleeces and species-specific fibrin or agarose. The transplants were subcutaneously implanted in the ridge. Thereafter, animals were separated into two groups, one with and one without methylprednisolone treatment. The specimens were histologically investigated after 6 and 12 weeks. Fleece fiber degradation was complete after 12 weeks, and all transplants showed areas of calcification. The corticosteroid-treated group presented pronounced trabecular bone generation without fibrous tissue infiltration. The untreated group showed sporadic islets of calcification without coherent bone formation, and adjacent fibrous tissue had infiltrated the transplants. Native controls and corticoid-treated transplants did not exhibit bone generation or signs of fibrous tissue infiltration. This study found that immunomodulation by intramuscular methylprednisolone application protects tissue-engineered autogenous chondrocyte transplants from fibrous tissue infiltration and induces trabecular bone formation.
    Archiv für Klinische und Experimentelle Ohren- Nasen- und Kehlkopfheilkunde 05/2004; 261(4):216-24. · 1.46 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Large mandibular defects caused by trauma, infection or resection of a tumour are still a major problem for plastic and maxillofacial surgeons. The modern concept of tissue engineering combines the osteoinductive effects of osteogenic cells with a suitable scaffold structure to promote differentiation of osteoblasts and optimal matrix production. Critical size mandibular bone defects were therefore made to investigate the osteogenic potential of periosteal cells and a bioabsorbable polymer fleece (Ethisorb 510) in minipigs. Periosteal cells were isolated from four minipigs, expanded in vitro and seeded with fibrin glue into Ethisorb 510 fleeces. Tissue constructs were used to repair critical size mandibular defects and compared with two minipigs with untreated bone defects. Bone healing was evaluated after 90 and 180 days by radiographs and a histological scoring system. The radiographs showed increased radiodensity of defects filled with the cell-fibrin-fleece-constructs compared with the untreated control group after 90 and 180 days in vivo. The defects repaired by the cell-fibrin-scaffolds (180 days in vivo) obtained the highest histological mean score 2.9 (range 2-3), while defects filled by cell-fibrin-scaffolds (90 days in vivo) achieved a mean score of 2.1 (range 2-3). In contrast, the control group (n = 2) scored 1 and 2. The results show that a combination of periosteal cells and polymer fleeces may be a promising approach for clinical mandibular augmentation.
    Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 02/2003; 37(3):129-33. · 0.94 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: The established surgical methods of external ear reconstruction using autogenous tissue represent the current state of the art. Because of the limited possibilities for shaping conventional harvested autogenous rib cartilage, the cosmetic results of auricular reconstruction are frequently unsatisfactory. Tissue engineering could represent an alternative technique for obtaining a precisely shaped cartilage implant that avoids donor site morbidity and unsatisfactory cosmetic results. In this study, the reliability and quality of a tissue-engineering model for the manufacture of auricular-shaped human cartilage implants was investigated, focusing on the feasibility of the manufacturing process and the in vivo and in vitro maturation of an extracellular cartilage-like matrix. Implants were molded within an auricular-shaped silicone cylinder, and human nasal septal chondrocytes crosslinked by human fibrin within bioresorbable PGLA-PLLA polymer scaffolds were used. After an in vitro incubation of up to 6 weeks, defined fragments of the prefabricated auricular-shaped construct were implanted subcutaneously on the backs of nude mice for at least 6 to 12 weeks ( n=7). Scaffolds without cell loading served as controls. Macroscopic and histochemical examination after 3 and 6 weeks in vitro showed a solid compound of homogenously distributed chondrocytes within the polymer scaffold, leading only to a limited pericellular matrix formation. Analysis after 6 and 12 weeks of in vivo maturation demonstrated a solid tissue compound and neocartilage formation with the presence of cartilage-specific matrix components. Implants obtained shape and size during the entire period of implantation. The model of cartilage implant manufacturing presented here meets all biocompatible requirements for in vitro prefabrication and in vivo maturation of autogenous, individually shaped cartilage transplants.
    Archiv für Klinische und Experimentelle Ohren- Nasen- und Kehlkopfheilkunde 08/2002; 259(6):316-21. · 1.46 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Autogenous cartilage transplantation is a generally accepted method in reconstructive surgery. A promising alternative to this established method could be represented by in vitro engineering of cartilage tissue. In both methods of autogenous transplantation, host response induces reduction of transplant size and transplant instability to an unforeseeable extent. To investigate if polyelectrolyte complex (PEC) membranes were able to avoid host-induced effects on implanted tissues without neglecting the tissue metabolism, human septal cartilage was encapsulated with polyelectrolyte complex membranes and subcutaneously implanted on the back of nude mice. Septal cartilage implants, without encapsulation served as control group. Histochemical and electron microscopic investigations were performed 1, 4, 8 and 16 weeks after implantation. In the case of an intact PEC-membrane no interactions between the host and the implant could be observed. In some implants, the capsule was torn in several areas and signs of chronic inflammation with the cartilage having been affected mildly could be observed. Implanted cartilage protected with PEC-encapsulation showed no signs of degeneration and significantly lower level of after effects of chronic inflammation than implanted cartilage without PEC-encapsulation. Therefore, it could be expected, that PEC membrane encapsulation offers a novel approach to protect cartilage implants from host response after autogenous transplantation.
    Biomaterials 09/2000; 21(15):1561-6. · 7.60 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: In reconstruction of cartilage defects, autogenous transplantation is known as a reliable and experienced method. Although a clinical application has not been reported until now, tissue engineering permits in vitro production of autogenous cartilage transplants. Nevertheless, in both methods the cartilage is exposed to individually varying resorptive mechanisms. Among other methods for in vivo tissue protection, the encapsulation with a semipermeable polyelectrolytecomplex membrane could guarantee sufficient protection against resorptive influences. Human septal cartilage was encapsulated (group 1) with polyelectrolytecomplex membranes and subcutaneously implanted on the back of thymusaplastic nude mice. Cartilage implants without encapsulation (group 2) were used as control. Scanning electron microscopy and histochemical investigations were performed 1, 4, 8, 12 and 16 weeks after implantation. Group 1 showed no signs of resorption and chronic inflammation at all. In contrast, group 2 presented, correlating to the time of implanta-tion, increasing signs of cell death and fibrotic transformation, representing an increased activity of resorption. In conclusion, tissue encapsulation with a polyelectrolytecomplex membrane could ensure a sufficient protection of human cartilage transplants from resorptive influences. For the plastic-reconstructive surgeon the desired result becomes more calculable.
    HNO 03/2000; 48(2):119-24. · 0.42 Impact Factor
  • Biomaterials 01/2000; 21:1561-1566. · 7.60 Impact Factor

Publication Stats

111 Citations
22.82 Total Impact Points

Institutions

  • 2000–2012
    • Humboldt University of Berlin
      • Department of Psychology
      Berlin, Land Berlin, Germany
  • 2005–2006
    • Charité Universitätsmedizin Berlin
      • Department of Otolaryngology
      Berlin, Land Berlin, Germany
  • 2002–2004
    • Freie Universität Berlin
      Berlín, Berlin, Germany