In Vivo Implantation of Chondrocytes Seeded into a Three-dimensional PLGA Sponge: Is in Vitro Culture before Implantation Necessary?

For tissue-engineered neocartilage formation in vivo, most studies have cultured chondrocytes within a biodegradable polymer in vitro before implantation of cell-polymer complex into an animal. The present study was performed to investigate the necessity of in vitro culture (preconditioning). Cell-polymer complex was made of chondrocytes obtained from a rabbit ear and a 85:15 poly(DL-lactic-co- glycolic acid) (PLGA) sponge. The complex was implanted into a nude mouse either after or without in vitro preconditioning. For control groups, PLGA sponge without chondrocytes was used. One, 2, and 4 weeks after the implantation, each group was examined by measurement of weight and volume of sponges as well as histologic study with Safranin-O staining. The control groups showed loss of weight as time passed. The non-preconditioned group, on the other hand, showed weight loss for the first week, but increased in weight afterwards. The preconditioned group also had weight loss in the first week after the implantation with no noticeable weight changes thereafter. Neither weight nor volume of PLGA sponges in preconditioned group was significantly different from those in non-preconditioned group until the 2nd week. In the 4th week, volume of sponges in non-preconditioned group was significantly larger than that in preconditioned group. On histological observation, chondrocytes seeded into a PLGA sponges proliferated and differentiated into cartilage tissues both in preconditioned and non-preconditioned groups, but non-preconditioned group formed cartilage tissue more extensively than the preconditioned group. Based on the above results, it is suggested that new cartilage tissues can be formed successfully following the implantation of cell- polymer complex into a living body without any prior conditioning in a separate culture system.

In Vivo Biodegradability of PLLA and PLGA Sponge using Non-toxic Effevescent as a Porogen Additive

In many tissue engineering application, highly open porous scaffolds are required for efficient cell seeding and culture. Synthetic biodegradable polymers such as poly (L-lactic acid)(PLLA) and its copolymers with D-lactic and glycolic acids(PLGA) are widely used as a porous scaffold. The suitable biodegradability and dimensional stability of porous scaffolds during in vivo implantation play an important role in tissue engineering application. In this study, we investigated in vivo biodegradation and dimensional stability of acellular porous polymer scaffolds prepared by using a gas foaming technique with non-toxic effervescent mixture. In addition, we have engineered cartilage tissue 3D cultured on PLGA scaffolds in nude mouse in order to compare with degradation and deformation on acellular porous polymer scaffolds and to form tissue-engineered cartilage tissue. Sodium bicarbonate and citric acid crystals were used as an effervescent mixture. These particles were milled and sieved to yield various range of sizes(50 - 100, 100 - 300, and > 300 micrometer). After polymer scaffolds fabricated, biodegradation test was performed in subcutaneous tissue of male rats during 12 weeks. Degradability of polymer scaffolds were evaluated by weight difference, gel permeation chromatography(GPC), and SEM as each period. Tissue-engineered cartilage by transplanting 3D cultured chondrocytes onto PLGA 85:15 scaffolds in nude mouse was also made and compared with acellular scaffolds. In conclusion, highly open porous biodegradable scaffolds are prepared by gas foaming method using sodium bicarbonate and citric acid as a non-toxic effervescent mixture. Furthermore, tissue-engineered cartilage formation by in vivo 3D culture onto modified PLGA scaffolds in nude mouse was significantly improved as compared to controls.