Comparison of transforming growth factor-beta1 and lovastatin on differentiating mesenchymal stem cells toward nucleus pulposus-like phenotype: An in vitro cell culture study

Study Design: In vitro cell culture study. Purpose: This study aims to investigate the impact of transforming growth factor-beta1 (TGF-ß1) and lovastatin on differentiating human mesenchymal stem cells (MSCs) toward nucleus pulposus (NP)-like phenotype. Overview of Literature: MSCs offer a cell source to the cell-based therapy for intervertebral disc degeneration. TGF-ß1 is used to induce MSCs to differentiate into NP-like cells; however, an undesired expression of collagen type I has been reported. Statins reportedly stimulate expression of bone morphogenetic protein-2 (BMP-2) and promote the chondrogenic phenotype to NP cells. However, the effects of statins with or without TGF-ß1 on the differentiation of MSCs into NP-like cells remain unclear. Methods: Human MSCs were treated with TGF-ß1 alone, lovastatin alone, and simultaneous or sequential treatment with TGF-ß1 and lovastatin. After the proposed stimulation, the total RNA was extracted to assess the expression profile of NP cells-specific genes. Hematoxylin-eosin staining was used for examining the microscopic morphology. Furthermore, we detected the syntheses of S-100 protein, aggrecan, and collagen type II in the extracellular matrix using immunohistochemical staining. Results: Simultaneous or sequential treatment of TGF-ß1 and lovastatin could further augment the BMP-2 overexpression compared with lovastatin-alone treatment. However, the mRNA expression of aggrecan and collagen type II was not compatible with the expression level of BMP-2. Immunohistochemical studies revealed compatible production of aggrecan, collagen type II, and S-100 protein in all three groups treated with lovastatin. Cells in groups treated with lovastatin were less populated than that in the group treated with TGF-ß1 alone. Conclusions: This study demonstrates a promising role of lovastatin in inducing human MSCs into NP-like cells. However, further optimization of cell density before lovastatin treatment, treatment duration, and combination with TGF-ß1 are warranted to attain better stimulatory effects.