The purpose of this study was to investigate, in vitro and in vivo, the suitability of chitosan (CHS) scaffolds produced by the net-shape-nonwoven (NSN) technology, for use as bone graft substitutes in a critical-size femoral bone defect in rats. For in vitro investigations, scaffolds made of CHS, mineralized collagen (MCM), or human cancellous bone allograft (CBA) were seeded with human telomerase-immortalized mesenchymal stromal cells (hTERT-MSC), incubated for 14 days, and thereafter evaluated for proliferation and osteogenic differentiation. In vivo, CHS, MCM and CBA scaffolds were implanted into 5 mm critical-size femoral bone defects in rats. After 12 weeks, the volume of newly formed bone was determined by microcomputed tomography (µCT), while the degree of defect healing, as well as vascularization and the number of osteoblasts and osteoclasts, was evaluated histologically. In vitro, CHS scaffolds showed significantly higher osteogenic properties, whereas treatment with CHS, in vivo, led to a lower grade of bone-healing compared to CBA and MCM. While chitosan offers a completely new field of scaffold production by fibers, these scaffolds will have to be improved in the future, regarding mechanical stability and osteoconductivity.

For the purpose of studying nutrient digestion and absorption in the small intestine, pigs were provided with ileo-rectal anastomoses. The anaesthetic and operation method is described. X-ray examinations do not show a significant backflow of digesta into the from colon cranially open towards the anastomosis as well as a totally intact sphincter ani. With the help of additional doses of highly digestible, N-free nutrients rich in energy (starch + saccharose), the operated animals achieved a growth development corresponding to that of intact control animals. For the assessment of the physiologic state of the animals, the concentrations in the serum of the total protein, of albumin, urea, glucose, calcium, inorganic phosphorus and creatinine as well as the activities of aspartate amino transferase and alkaline phosphatase were determined. These showed for the respective criteria changes conditioned by age and dependent on feed intake. The fixing of the anastomoses did not result in disturbances of nutritional or organic damages. Histologic studies of the mucosa of stomach, duodenum and jejunum did not show pathologic changes. The weight of stomach, duodenum and jejunum, determined in 2 live weight ranges, is identical for operated and intact animals in relation to the weight of the empty body of the animals. The weight of ileum, caecum and colon of the operated animals is significantly lower, due to inactivity atrophy. The tissue amount available for the intake of a volume unit (weight-volume index) is nearly identical for operated and intact animals in the duodenum and the jejunum. The index functionally increasing for intact animals from the jejunum to the ileum (stenosis due to temporary digesta congestion in the ileum) remained the same with anastomosis animals for 29 or 26 weeks resp. after the operation. As a result of the biochemical and morphological studies it was shown that animals with an ileo-rectal anastomosis are suitable for the determination of nutrient digestibility at the end of the ileum.

Difficulties in treating pseudarthrosis and critical bone defects are still evident in physicians’ clinical routines. Bone morphogenetic protein 2 (BMP-2) has shown promising osteoinductive results but also considerable side effects, not unexpected given that it is a morphogen. Thus, the bone regenerative potential of the novel selective, non-morphogenic EP4 prostaglandin receptor agonist KMN-159 was investigated in this study. Therefore, mineralized collagen type-1 matrices were loaded with different amounts of BMP-2 or KMN-159 and implanted into a 5 mm critical-sized femoral defect in rats. After 12 weeks of observation, micro-computed tomography scans were performed to analyze the newly formed bone volume (BV) and bone mineral density (BMD). Histological analysis was performed to evaluate the degree of defect healing and the number of vessels, osteoclasts, and osteoblasts. Data were evaluated using Kruskal-Wallis followed by Dunn’s post hoc test. As expected, animals treated with BMP-2, the positive control for this model, showed a high amount of newly formed BV as well as bone healing. For KMN-159, a dose-dependent effect on bone regeneration could be observed up to a dose optimum, demonstrating that this non-morphogenic mechanism of action can stimulate bone formation in this model system.