Untersuchung der Angiogenese im Tissue Engineering

Chick embryo chorioallantoic membrane (CAM) model: a useful tool to study short-term transplantation of cryopreserved human ovarian tissue

OBJECTIVE

To investigate the chorioallantoic membrane (CAM) model for the study of short-term transplantation of frozen human ovarian tissue.

DESIGN

Prospective study.

SETTING

Academic research unit.

PATIENT(S)

Ovarian tissue was obtained from three women.

INTERVENTION(S)

Frozen-thawed human cortical fragments were grafted onto traumatized CAM or beneath the CAM of 10-day-old chick embryos. Grafts were retrieved after 1, 2, 3, 4, and 5 days in ovo.

MAIN OUTCOMES MEASURE(S)

Viability was assessed by calcein-AM and ethidium homodimer I. Tissue integrity, ischemic injury, and neovascularization were evaluated by histology. Cell proliferation was analyzed by Ki-67 immunohistochemistry.

RESULT(S)

All the grafts showed adhesion when placed onto CAM, compared with only 30.4% beneath the CAM. Follicles were healthy, apart from a few degenerated follicles in necrotic and fibrotic areas. After 5 days, the majority of follicles were intermediate (32%) or primary (45.7%). Ki-67 immunohistochemistry revealed 12.5% proliferative follicles on day 2, reaching 20.7% on day 5. Fibrosis appeared on day 1; necrosis, follicular degeneration and follicular proliferation on day 2; and neovascularization and stromal cell proliferation on day 3.

CONCLUSION(S)

The present study showed that the CAM model provides a new approach to study human ovarian tissue transplantation in its first ischemic stages, yielding information on the timing of tissue changes before the establishment of neovascularization.

Mechanical regulation of matrix reorganization and phenotype of smooth muscle cells and mesenchymal stem cells in 3D matrix

In an effort to develop small-diameter tissue-engineered vascular grafts (< 6 mm), collagen and fibrin gels seeded with human aortic smooth muscle cells (HASMCs) were constructed in a three-dimensional tubular environment and subjected to mechanical stimulation to investigate changes in cellular response and matrix remodeling. After testing various collagen and fibrin concentrations, experiments indicated 2:1 mg/mL of collagen:fibrin constructs with embedded HASMCs contracted as well as the pure fibrin, at 54% their original length after 3 days, indicating enhanced cellular activity and matrix remodeling . Vascular constructs were cultured for three days before undergoing pulsatile 10% cyclic strain at 1 Hz for three days. RT-PCR showed that cyclic strain increased the gene expression of SMC markers alpha-actin and SM22, indicating that mechanical stimulation induces SMCs to a more contractile phenotype. Histology showed a more compacted collagen fiber structure for mechanically stimulated constructs compared to the looser collagen network in static constructs. The effects of 3D mechanical strain were also tested on mesenchymal stem cells (MSCs), which can be a possible source for SMCs. Cyclic strain increased alpha-actin and SM22 gene expression in MSCs, suggesting the differentiation of MSCs into a SMC phenotype.