In vitro construction technology is a key approach to industrialization and clinic application of engineered cartilage. However, it is very difficult to acquire a functional engineered cartilage with the present technology. Bioreactors can simulate the cartilage microenvironment in vivo and are expected to make up the shortcoming of the present technology. Current bioreactors in use are designed according to fluid shear pressure, hydrostatic pressure and/or direct compression, all of which can promote the development and mature of cartilage in vivo. Due to the failure to achieve ideal results by a single-purpose bioreactor, it will become a development direction in future to design and produce a compound bioreactor. This article reviewed the advances in the bioreactor for cartilage tissue engineering.

Objective This study investigates feasibility of replacing urinary epidermal cells with foreskin epidermal cells to reconstruct engineered anterior urethra with acellular collagen matrix. Methods A cellular collagen matrices were generated from allogeneic rabbit bladder submucosa.In 6 rabbits,autologous foreskin epidermal cells isolated,in vitro expanded and labeled with Brdu before seeding onto a tubular collagen matrix of 2 cm long.In 12 male rabbits, urethral mucous defect was created and urethroplasty was performed with tubular collagen matrix seeded with epidermal cells (n=6) in experimental group or matrix without cells seeding (n=6) in control group.Urethrography was performed at 1,2,and 6 months postoperatively.Urethras grafts were harvested and analyzed grossly and histologically at the same time points. Results In control group, gross and urethrography demonstrated urethral stricture of repaired defects at all time points.Histology showed a single layer of epidermal cell with unorganized and crassitude muscle fiber bundles in submucosa layer.In contrast, urethrography showed a patency of repaired urethral defect with the maintenance of a wide urethral caliber in experimental group without sign of strictures at any time points. Histologically,the graft seeded with epidermal cell had a multi-layers epidermal cells by 1 month,which demonstrated the presence of a epidermal cells layer with a normal submucosa structure.The immunoflorescent staining of Brdu confirmed the presence of implanted epidermal cells.In addition, the implanted cells also express keratin when stained with anti-pancytokeratins AE1/AE3 antibody.At 2 month,histology showed relatively normal urethral architecture with vessel abundance in submucosa structure.The staining of Brdu showed decreased at implanted epidermal cells and epithelial phenotypes were confirmed immunocytochemically using pancytokeratins AE1/AE3.At 6 month,the graft structure show multi-layers epidermal cells without staining of Brdu. Conclusions Urethra reconstruction was better achieved with cell seeded acellular collagen matrix when compare with acellular matrices alone.Foreskin epidermal cells seems succeeded in replacing urethral epidermal cells for urethra reconstruction.