M. Bücheler

Cartilage and bone tissue engineering for reconstructive head and neck surgery

The loss of cartilage and bone because of congential defects, trauma and after tumor resection is a major clinical problem in head and neck surgery. The most prevalent methods of tissue repair are through autologous grafting or using implants. Tissue engineering applies the principles of engineering and life sciences in order to create bioartificial cartilage and bone. Most strategies for cartilage tissue engineering are based on resorbable biomaterials as temporary scaffolds for chondrocytes or precursor cells. Clinical application of tissue-engineered cartilage for reconstructive head and neck surgery as opposed to orthopedic applications has not been well established. While in orthopedic and trauma surgery engineered constructs or autologous chondrocytes are placed in the immunoprivileged region of joints, the subcutaneous transplant site in the head and neck can lead to strong inflammatory reactions and resorption of the bioartificial cartilage. Encapsulation of the engineered cartilage and modulation of the local immune response are potential strategies to overcome these limitations. In bone tissue engineering the combination of osteoconductive matrices, osteoinductive proteins such as bone morphogenetic proteins and osteogenic progenitor cells from the bone marrow or osteoblasts from bone biopsies offer a variety of tools for bone reconstruction in the craniofacial area. The utility of each technique is site dependent. Osteoconductive approaches are limited in that they merely create a favorable environment for bone formation, but do not play an active role in the recruitment of cells to the defect. Delivery of inductive signals from a scaffold can incite cells to migrate into a defect and control the progression of bone formation. Rapid osteoid matrix production in the defect site is best accomplished by using osteoblasts or progenitor cells.

[Cell-based strategies for salivary gland regeneration].

Xerostomia as a side effect of radiotherapy or due to Sjögrens disease leads to considerable impairment of the quality of life of the affected patients. Preventive treatment approaches such as intensity-modulated radiotherapy, surgical transfer of a submandibular gland to a site outside the radiation field or administration of amifostin during radiation treatment are not yet completely established in clinical practice and are not applicable for all patients. Symptomatic treatment with pilocarpin or synthetic saliva leads to an improvement of the symptoms only in some patients, and in the case of pilocarpin significant systemic anticholinergic side-effects might occur. Because large numbers of patients are affected and current treatment options are not satisfactory, it is essential to develop new treatment options. In parallel with the in vitro production of functional salivary gland constructs by means of tissue engineering techniques, attempts are currently under way to experimentally restore salivary gland function by genetic treatment approaches such as transfection of the affected salivary glands with aquaporins or pro-angiogenic factors. In addition, the in vivo application of stem cells is under investigation. In the present paper, we discuss the clinical and radiobiological background of xerostomia and highlight possible innovative future treatment options.

Zellbasierte Strategien für die Speicheldrüsenregeneration

Xerostomia as a side effect of radiotherapy or due to Sjögrens disease leads to considerable impairment of the quality of life of the affected patients. Preventive treatment approaches such as intensity-modulated radiotherapy, surgical transfer of a submandibular gland to a site outside the radiation field or administration of amifostin during radiation treatment are not yet completely established in clinical practice and are not applicable for all patients. Symptomatic treatment with pilocarpin or synthetic saliva leads to an improvement of the symptoms only in some patients, and in the case of pilocarpin significant systemic anticholinergic side-effects might occur. Because large numbers of patients are affected and current treatment options are not satisfactory, it is essential to develop new treatment options. In parallel with the in vitro production of functional salivary gland constructs by means of tissue engineering techniques, attempts are currently under way to experimentally restore salivary gland function by genetic treatment approaches such as transfection of the affected salivary glands with aquaporins or pro-angiogenic factors. In addition, the in vivo application of stem cells is under investigation. In the present paper, we discuss the clinical and radiobiological background of xerostomia and highlight possible innovative future treatment options.

Zellbasierte Strategien für die Speicheldrüsenregeneration@@@Cell-based strategies for salivary gland regeneration

Xerostomia as a side effect of radiotherapy or due to Sjögrens disease leads to considerable impairment of the quality of life of the affected patients. Preventive treatment approaches such as intensity-modulated radiotherapy, surgical transfer of a submandibular gland to a site outside the radiation field or administration of amifostin during radiation treatment are not yet completely established in clinical practice and are not applicable for all patients. Symptomatic treatment with pilocarpin or synthetic saliva leads to an improvement of the symptoms only in some patients, and in the case of pilocarpin significant systemic anticholinergic side-effects might occur. Because large numbers of patients are affected and current treatment options are not satisfactory, it is essential to develop new treatment options. In parallel with the in vitro production of functional salivary gland constructs by means of tissue engineering techniques, attempts are currently under way to experimentally restore salivary gland function by genetic treatment approaches such as transfection of the affected salivary glands with aquaporins or pro-angiogenic factors. In addition, the in vivo application of stem cells is under investigation. In the present paper, we discuss the clinical and radiobiological background of xerostomia and highlight possible innovative future treatment options.

Proliferation and differentiation of human osteoblasts from the nasal septum in a new perfusion culture system

BACKGROUND Today, perfusion culture systems are mainly used to investigate cellular physiology and to cultivate three-dimensional tissue complexes. As a rule, these systems are relatively expensive and do not enable continuous microscopic monitoring of the growing cells. Simple and inexpensive perfusion culture systems have not been available up to now. METHODS A novel perfusion culture system was developed in which the modular components consist of a mounting apparatus for inserting various media supply systems, microdispenser pumps, and laminar-flow culture chambers, each with a culture volume of 8 cm(3). The perfusion chambers were inoculated with human osteoblast cells from the tissue culture (5,000/cm(2)) and were perfused for 10 days after adherence of the cells (0.5 ml/min). As a control group, osteoblast-like cells were cultured in identically constructed culture chambers without medium perfusion. After 10 days, the cell counts were determined in accordance with the Coulter principle. Alkaline phosphatase was measured photometrically as a characteristic for differentiation. RESULTS Compared with the control group, three to four times the quantity of cells were produced within 10 days in the perfusion cultures. The alkaline phosphatase values were equally high or only slightly lower, indicating that osteoblast differentiation of the cells was maintained with a higher proliferation. CONCLUSIONS As large a number of in vitro proliferated cells as possible is a prerequisite for clinical application of tissue engineering. By continuously supplying medium, the tested perfusion culture system enables a higher rate of proliferation of osteoblast-like cells with maintenance of differentiation. Continuous microscopic monitoring of the cultures is possible using commercially available Petri dishes.

Vermehrung und Differenzierung humaner Nasenseptum-Osteoblasten@@@Proliferation and differentiation of human osteoblasts from the nasal septum in a new perfusion culture system: Ein neuartiges Perfusionskultursystem

BACKGROUND Today, perfusion culture systems are mainly used to investigate cellular physiology and to cultivate three-dimensional tissue complexes. As a rule, these systems are relatively expensive and do not enable continuous microscopic monitoring of the growing cells. Simple and inexpensive perfusion culture systems have not been available up to now. METHODS A novel perfusion culture system was developed in which the modular components consist of a mounting apparatus for inserting various media supply systems, microdispenser pumps, and laminar-flow culture chambers, each with a culture volume of 8 cm(3). The perfusion chambers were inoculated with human osteoblast cells from the tissue culture (5,000/cm(2)) and were perfused for 10 days after adherence of the cells (0.5 ml/min). As a control group, osteoblast-like cells were cultured in identically constructed culture chambers without medium perfusion. After 10 days, the cell counts were determined in accordance with the Coulter principle. Alkaline phosphatase was measured photometrically as a characteristic for differentiation. RESULTS Compared with the control group, three to four times the quantity of cells were produced within 10 days in the perfusion cultures. The alkaline phosphatase values were equally high or only slightly lower, indicating that osteoblast differentiation of the cells was maintained with a higher proliferation. CONCLUSIONS As large a number of in vitro proliferated cells as possible is a prerequisite for clinical application of tissue engineering. By continuously supplying medium, the tested perfusion culture system enables a higher rate of proliferation of osteoblast-like cells with maintenance of differentiation. Continuous microscopic monitoring of the cultures is possible using commercially available Petri dishes.

Vermehrung und Differenzierung humaner Nasenseptum-Osteoblasten

BACKGROUND Today, perfusion culture systems are mainly used to investigate cellular physiology and to cultivate three-dimensional tissue complexes. As a rule, these systems are relatively expensive and do not enable continuous microscopic monitoring of the growing cells. Simple and inexpensive perfusion culture systems have not been available up to now. METHODS A novel perfusion culture system was developed in which the modular components consist of a mounting apparatus for inserting various media supply systems, microdispenser pumps, and laminar-flow culture chambers, each with a culture volume of 8 cm(3). The perfusion chambers were inoculated with human osteoblast cells from the tissue culture (5,000/cm(2)) and were perfused for 10 days after adherence of the cells (0.5 ml/min). As a control group, osteoblast-like cells were cultured in identically constructed culture chambers without medium perfusion. After 10 days, the cell counts were determined in accordance with the Coulter principle. Alkaline phosphatase was measured photometrically as a characteristic for differentiation. RESULTS Compared with the control group, three to four times the quantity of cells were produced within 10 days in the perfusion cultures. The alkaline phosphatase values were equally high or only slightly lower, indicating that osteoblast differentiation of the cells was maintained with a higher proliferation. CONCLUSIONS As large a number of in vitro proliferated cells as possible is a prerequisite for clinical application of tissue engineering. By continuously supplying medium, the tested perfusion culture system enables a higher rate of proliferation of osteoblast-like cells with maintenance of differentiation. Continuous microscopic monitoring of the cultures is possible using commercially available Petri dishes.