Evaluation of bone-protecting effects of palm carotene mixture in two- and three-dimensional osteoblast/osteoclast co-culture systems.

Abstract

Background: Carotene exists naturally in a complex mixture consisting of alpha (α), beta (β), and gamma (γ)-isoforms. Previous studies investigated the effects of individual carotene isomers on bone rather than their actions in a mixture. Purpose: This study explored the bone-protective properties of palm carotene mixture using both two- and three-dimensional co-culture systems. Study design: The viability of human foetal osteoblasts (hFOB 1.19), viability of human monocytic cell line (THP-1), osteoblast differentiation, osteoclast maturation, bone quality and strength were assessed in two- and three-dimensional co-culture system after treatment of palm carotene mixture. Methods: The viability of hFOB 1.19 and THP-1 was determined on day 1, 3, and 6 following treatment of palm carotene mixture. The osteoblast-osteoclast co-culture (ratio of hFOB 1.19 to THP-1 = 2:1) was treated with palm carotene mixture as well as subjected to alkaline phosphatase (ALP) and tartrate resistant acid phosphatase (TRAP) staining on day 21 to assess the osteoblast proliferation and osteoclast maturation. Dual-energy X-ray absorptiometry, micro-computed tomography, universal testing machine, and bone histomorphometry were used to assess the bone parameters of scaffolds co-cultured with osteoblasts and osteoclasts. Results: Palm carotene mixture (3.13 - 50 μg/mL) increased osteoblast viability. Monocyte viability decreased in lower concentration (3.13 - 12.5 μg/mL) but increased in higher concentration (25 - 50 μg/mL) of palm carotene mixture. Treatment with palm carotene mixture (12.5 µg/mL) demonstrated earlier peak for the ALP-positive area on day 14 but decreased total number of TRAP-positive multinucleated cells on day 21. Palm carotene mixture also increased bone volume and osteoblast number in the three-dimensional co-culture system. Conclusion: Palm carotene mixture potentially exhibits beneficial effects on bone by accelerating osteoblast proliferation and suppressing osteoclast maturation. The findings of current study serve as the basis for the further validation through animal experiments and human trials.