Biomedical subjects

R Strehl

Publications and source records attributed to R Strehl.

22 records · Page 2Linked to original sources

PubMedDate not supplied

Tissue factory: conceptual design of a modular system for the in vitro generation of functional tissues.

Tissue factory is a modular system designed to generate artificial tissues under optimal perfusion culture conditions. The microenvironment within the culture containers can be fine-tuned to meet the physiological needs of individual tissues, so that the generation of differentiated three-dimensional tissue constructs becomes possible. An optimal physiological environment is created by modulating a liquid phase as well as an artificial interstitium surrounding the growing construct. An innovative construction principle allows production of tissue culture containers, gas exchangers, and gas expanders at minimal material expenditure. Therefore it will be possible for the first time to produce sterile one-way perfusion culture modules for the generation of artificial tissues. The modules can be used separately as well as in a combined module. The system is designed to provide a possible platform for the standardized production of artificial tissues for future applications in biomedicine.

Cell Culture Techniques↗

PubMedDate not supplied

Controlled respiratory gas delivery to embryonic renal epithelial explants in perfusion culture.

During generation of artificial tissues high levels of oxygen are usually available whereas after implantation into a recipient's body the implant is not vascularized immediately, which leads to low oxygen partial pressures within the implanted tissue. Under these conditions cells will experience an oxygen shortage, contrasting with the abundance of oxygen during culture. It is uncertain whether tissues can be trained to tolerate such an acute hypoxic situation so that nonphysiological stress reactions and tissue necrosis can be avoided. To investigate the effects of varying oxygen levels on embryonic renal tissue in vitro we have been developing a model system combining continuous medium renewal with the ability to control levels of oxygen and carbon dioxide by gas equilibration through gas-permeable tubing. Renal embryonic tissue from neonatal rabbit was cultured in serum-free Iscove's modified Dulbecco's medium at 45, 90, 115, and 160 mmHg oxygen partial pressure for 14 days under continuous medium exchange in such a setup. After a 14-day culture period tissue sections were analyzed by cell biological methods and compared with fresh tissue histology. Surprisingly, embryonic renal explants survive and maintain good morphology for 14 days under all O(2) conditions tested. Expression of cytokeratin 19 within the established epithelium remains unchanged, indicating a structurally intact tissue. However, Na/K-ATPase is clearly downregulated under low O(2) conditions, whereas COX-2 expression increases drastically. An antiparallel effect of decreased O(2) concentrations on glycoprotein expression can be demonstrated with the lectin Dolichos biflorus agglutinin. Scanning electron microscopy reveals oxygen-dependent changes in cellular surface differentiation of developed collecting duct epithelium.

Adaptation, Physiological↗

PubMedDate not supplied

Modulation of cell differentiation in perfusion culture.

An in vitro model was used to investigate the terminal differentiation mechanisms leading from embryonic to adult renal tissue. For these experiments the capsula fibrosa with adherent embryonic tissue was isolated from neonatal rabbit kidneys. These explants were mounted onto special tissue carriers and cultured in medium containing serum for 24 h. During that time collecting duct (CD) cells grew out and formed a monolayered epithelium covering the whole surface of the explant. The carriers were then transferred to perfusion culture containers to obtain an optimal degree of differentiation. A special type of container allowed us to continuously superfuse the epithelia with individual media on the luminal and basal sides. Using this method it became possible to culture embryonic CD epithelia in a fluid gradient for weeks. The epithelia were superfused with standard Iscove's modified Dulbecco's medium (IMDM) on the basal side, while IMDM containing additional NaCl was used on the luminal side. In controls IMDM was superfused on both the luminal and basal sides. It was found that the degree of differentiation in the CD epithelia is dependent on the influence of fluid gradient exposure. Perfusion culture under isotonic conditions revealed that less than 5% of cells were immunopositive for principal and intercalated cell features, while epithelia cultured in a luminal-basal gradient showed more than 80% positive cells. Immunoreactivity for characteristic markers started to develop after an unexpectedly long latent period of 3-6 days, then increased continuously during the following 5 days and reached a maximum on day 14. After switching back from the gradient to isotonic culture conditions the immunoreactivity for some markers decreased within 5 days, while other characteristic features remained stable. Thus, differentiation was not only under the control of growth factors but was also regulated by the electrolyte environment.

Animals↗

PubMedDate not supplied

Electrolyte environment modulates differentiation in embryonic renal collecting duct epithelia.

The influence of electrolytes on the development of renal principal and intercalated collecting duct cells is unknown. Consequently embryonic collecting duct epithelia were exposed to different electrolyte concentrations, and their degree of differentiation was registered by immunohistochemical methods. Embryonic collecting duct epithelia were isolated from neonatal rabbit kidneys and placed on tissue carriers. The apical urine and the basal serum compartments were simulated in a gradient culture container. The two sides of the epithelium were each constantly superfused with medium for 13 days. In controls the medium on both apical and basal side was standard Iscove's modified Dulbecco's Medium (IMDM) with 112 mmol/l Na+ and 85 mmol/l Cl-. In experimental series the NaCl concentration at the basal side of the epithelium was increased up to 137 mmol/l Na+ and 99 mmol/l Cl- as found in the serum of neonatal rabbits. Light microscopy revealed morphologically faultless epithelia following gradient perfusion culture in standard and NaCl-adapted IMDM. The development of principal and intercalated cell features was monitored with the monoclonal antibodies 703, 503, PCD9, and peanut lectin. Cells immunopositive for monoclonal antibody 703, for example, increased from less than 10% in controls to more than 80% in NaCl-adapted IMDM. It is a new finding that the development of collecting duct cell features is influenced by the extracellular electrolyte environment.

Animals↗