Biodegradable polymer film as a source for formation of human fetal retinal pigment epithelium spheroids.

PURPOSE: To evaluate the attachment of human fetal rctinal pigment epithelial (HFRPE) cells to a biodegradable polymer film with subsequent formation of spheroids in vitro. METHODS: Ten biodegradable polymer films with different compositions were examined for their physical properties and ease of manipulation under a dissecting microscope. The film with the most suitable handling characteristics was chosen, and a purely isolated sheet of HFRPE cells was attached to it. The purity of the cells was assessed by their pigmentation and expression of cytokeratin. Proliferation was assessed by incorporation of 5-bromo-2'-deoxyuridine (BrdtJ). Cellular structure was analyzed under light and electron microscopes, and the functional capability of the cells was evaluated by rod outer segment (ROS) phagocytosis. RESULTS: The polymer film with composition 50:50 poly (DL-lactide) (PLA)/poly (DL-lactide-co-glycolide) (PLG) with an inherent viscosity of 1.03 dl/g was found to be the most suitable for handling under the microscope. Sheets of HFRPE cells attached to the polymer films within 48 hours and began to form spheroids. All the isolated cells were pigmented and expressed cytokeratin. They possessed a cuboidal morphology, numerous apical microvilli, and no sign of dedifferentiation. HFRPE cells produced extracellular matrix (collagen filaments) on their basal side, filling the cavities of the polymer film. The cells subsequently proliferated, incorporated BrdU, migrated onto the culture plate to form monolayers, and phagocytized ROS. CONCLUSIONS: Biodegradable polymer films can be used as a scaffold for the adhesion of the HFRPE sheet and formation of spheroids. Spheroids represent a source of high density and well-differentiated HFRPE cells that are easy to transfer. Furthermore, the stricture of the membrane makes it suitable for additional applications.

Biodegradation and biocompatibility of a guided tissue regeneration barrier membrane formed from a liquid polymer material.

Biodegradable barrier films were made by coagulating a solution of poly(DL-lactide) in N-methyl-2-pyrrolidone on porous polyethylene pads wetted with saline solution. The semisolid films were cut into 10 x 10 mm barriers and implanted subcutaneously in rabbits. At monthly intervals, the polymer implant sites were compared histologically to those implanted with USP negative control plastic. The polymer films were retrieved from the surrounding tissue, dried, weighed, and the changes in molecular weight determined using gel permeation chromatography. The molecular weight of the polymer decreased at a relatively constant rate over 5 months; however, no significant mass loss occurred until 5 months postimplantation. Also, no distinct histological differences were noted between the polymer barrier and the control plastic sites until 6 months when histiocytes and multinucleated giant cells showed a modest increase around fragmented polymer films. Similar barrier films also were fitted over naturally occurring buccal dehiscence defects in beagle dogs and the tissue sites compared histologically at 6 months to sham-operated control sites. New bone and dense connective tissues closely approximated segments of the remaining polymer and demonstrated the biocompatibility of the biodegradable films. Histomorphometric analyses of treated sites compared to sham controls showed that the polymer barrier is effective in promoting bone and cementum regeneration in periodontal defects in dogs.

Periodontal regeneration in naturally occurring Class II furcation defects in beagle dogs after guided tissue regeneration with bioabsorbable barriers.

THE EFFICACY OF A BIOABSORBABLE polylactic acid based barrier was evaluated using naturally occurring buccal Class II furcation defects in beagle dogs. Sixteen furcation sites (8 control and 8 experimental) were treated in 6 adult animals. After full thickness flap reflection, exposed furcations and root surfaces were thoroughly root planed. In experimental sites a customized barrier was formed and fitted to cover the defect. Surgical flaps were replaced slightly coronal to the cemento-enamel junction. Animals were sacrificed at 6 months and specimens processed for histologic evaluation. Histologic and histometric analyses were done using 6 micrograms step serial sections in the buccal-lingual plane, corresponding to the buccal-lingual extent of the furcation. Results were: mean total defect experimental sites 1.92 mm; control sites 1.47 mm. Mean new cementum formation experimental sites 1.36 mm (71% of initial defect); control sites 0.25 mm (17% of initial defect). Mean new bone formation experimental sites 1.42 mm (74% of initial defect); control sites 0.20 mm (14% of initial defect). Mean junctional epithelium formation experimental sites 0.42 mm (22% of initial defect); control sites 1.21 mm (82% of initial defect). Statistical analysis demonstrated significant differences in all healing parameters favoring experimental (barrier-treated) sites. In this model, regeneration (new bone, cementum, and periodontal ligament) of 71% of the original defect in experimental sites and only 14% in control sites demonstrated a response that highly favored use of the barrier.

Periodontal healing after guided tissue regeneration with Atrisorb barriers in beagle dogs.

Periodontal healing after use of Atrisorb barrier material (polylactic acid) for guided tissue regeneration was studied in the premolar and molar teeth of six beagle dogs. Defects studied were surgically induced or were caused by naturally occurring periodontitis. Barriers fragmented and became displaced in 2 to 5 weeks after application. Granulation tissue was sometimes present between the barrier and root surface at 10 days to 4 weeks. Several sites were surgically reentered at 4 months, and new bone covered 60% to 100% of the formerly exposed furcations and root surfaces. Sites obtained for histologic evaluation 9 to 12 months after the baseline surgery showed new connective tissue attachment, cementum, and alveolar bone. Histomorphometric analyses quantitated these tissue changes, and new connective tissue attachment covered 72% of surgically exposed root surfaces and 77% of periodontitis-exposed root surfaces. It was concluded that new periodontal supporting tissues became reconstituted on root and furcation surfaces after use of the Atrisorb barrier material for GTR.