Biocompatibility and osteoconductivity of PLCL coated & non‐coated xenografts‐ an in‐vitro and pre‐clinical trial

Abstract

Background Cells, scaffolds and growth-factors are the key components required to generate engineered tissues. A scaffold can deliver growth factors, and supports cell attachment. The material composition, topography and architecture influence cell behavior and intercellular interactions, and overall performance of the scaffolds. Bovine deproteinized bone matrix has become a very popular grafting material for various oral indications including socket preservation due to its large availability. Aim/Hypothesis To compare viability and proliferation of mesenchymal stem cells (MSCs) seeded onto two commercial xenografts- Bio-Oss (BO) and Bioactive Bone Bovine (BB). Next, these materials were compared for histomorphometric bone formation in a socket preservation model in rats. Material and Methods MSCs were seeded onto monolayers of BO or BB granules that covered the bottom of 96 well plates. Both materials were used with the same granules size (0.25–1 mm granules). Cell viability and proliferation was evaluated after incubation of 0, 2, 20 and 48 hours. 24 Sprague Dawley rats underwent unilateral extraction of maxillary molars. Rats were randomly divided into three groups- natural healing (non-grafted socket) or socket preservation with either BO or BB. Rats were sacrificed after 8 weeks and evaluation of the socket preservation region was performed from each specimen, under a light microscope. Images were analyzed using software. The following values were measured- (i) total bone area (ii) connective tissue (iii) residual bone graft. The measurements were expressed as percentages of the total sample area. To compare between the group regarding the metabolic activity and histomorphometric parameters one way analysis of variance was used. A P-value < 0.05 was selected to determine Results Differences in the metabolic activity of MSCs that were seeded onto BO or BB was observed at 2 hours after seeding- the metabolic activity was elevated compared to baseline in the BB (P = 0.046) and not changed in the BO wells (P = 0.84). After 20 hours, the metabolic activity of MSCs seeded onto BO was decreasing (P = 0.005) while cell viability was not changed in the BB group (P = 0.356). Intergroup comparison revealed higher metabolic activity of MSCs seeded on BB after 48 hours compared with BO (P = 0.016). The in-vivo results demonstrated differences in socket healing between the groups- percentage of new bone was higher in the BB compare to BO group (39.1% ± 14.3 vs. 23.7% ± 10.8, respectively, P = 0.096). Connective tissue portion was higher in the BO group compared with BB (73.7% ± 11.1 vs. 49.6% ± 13.7 respectively P = 0.018). Residual grafting martial was higher in the BB (11.34% ± 4.18 vs. 2.62% ± 1.23, p =0.011). Conclusions and Clinical Implications The results of this study demonstrating higher vitality and proliferation of MSCs seeded onto BB. Furthermore, following ridge preservation, higher percentage of new bone and lower residual scaffold were found in the BB compared with BO. This enhanced regenerative response might be the result of an enhancement of metabolic activity in cells attached to it. Further research will be needed to understand the precise mechanism.