Bone morphogenetic protein 2 alleviated intervertebral disc degeneration through mediating the degradation of ECM and apoptosis of nucleus pulposus cells via the PI3K/Akt pathway

Abstract

The present study aimed to explore the underlying mechanisms of bone morphogenetic protein 2 (BMP2) in alleviating intervertebral disc degeneration (Idd). A rat puncture Idd model was constructed, and the rats were randomly divided into six groups: control; Idd (model); Idd+PBS [containing 10 10 adeno-associated virus serotype 2 (AAV)]; and Idd + AAV2-BMP2 (10 6 , 10 8 and 10 10 ). IL-1β was used to treat primary nucleus pulposus (NP) cells to mimic Idd in vitro. The effects of BMP2 in Idd were determined by magnetic resonance imaging (MRI), hematoxylin and eosin staining and Alcian Blue staining in vivo. The levels of collagen II, aggrecan, transcription factor SOX9 (SOX9) and matrix metalloproteinase 13 (MMP-13) were examined using western blot analysis and reverse transcription quantitative polymerase chain reaction (RT-qPcR) in NP tissues and cells. The expression of c-telopeptide of type II collagen (cTX-II) in the sera or cell supernatants was determined by ELISA. In addition, the levels of phosphorylation of phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt), and the levels of apoptosis-associated proteins and apoptosis ratio of NP cells were also determined by western blot analysis and flow cytometry, respectively. LY29400, an inhibitor of PI3K, was used to additionally confirm the signal pathway mechanism of BMP2 treatment in IDD. BMP2 significantly extended the interval between discs and alleviated the fibrous ring rupture and the decrease in the levels of glycoproteins in Idd rats, as determined by MRI and histological staining. Additionally, BMP2 treatment significantly upregulated the levels of collagen II, aggrecan and SOX9, but downregulated the levels of MMP-13 and cTX-II in Idd rats and NP cells in a dose-dependent manner. concurrently, recombinant human (rh)BMP2 pretreatment also significantly decreased the apoptosis ratio of interleukin (IL)-1β-treated NP cells via downregulating the level of cleaved caspase-3 and upregulating the level of uncleaved poly (adenosine 5'-diphosphate-ribose) polymerase. It was demonstrated that rhBMP2 also significantly decreased the inflammatory response in NP tissues and cells, based on levels of IL-6, TNF-α and IL-10. In addition, rhBMP2 inhibited cell apoptosis via upregulating the phosphorylation levels of the PI3K/Akt signaling pathway, and LY29400 pretreatment inhibited the effects of BMP2 in IL-1β treated NP cells. BMP2 alleviated Idd via the PI3K/Akt signaling pathway by inhibiting NP cell apoptosis and decreasing the levels of matrix proteins.

Bone Morphogenetic Proteins for Nucleus Pulposus Regeneration

“…In co-cultures of NP cells and MSCs of one donor, most regeneration was accomplished by the addition of BMP4 rather than a heterodimer. The present study shows that of the BMPs tested here, BMP4 may be the most suitable candidate for NP regeneration, although BMP2 and BMP7 thus far have been the usual candidates employed in regenerative treatment strategies of the degenerated disc [21,22,[24][25][26][27][36][37][38]. In line with these findings, induction of chondrogenesis in MSCs has been shown to be more efficient with BMP4 than with BMP7, and these cells produced a better proteoglycan-rich matrix in vivo [39].…”

“…For NP regeneration, mainly BMP2 and BMP7 have been investigated [21,22], most likely because they are clinically available [23]. In rabbit models of induced IVD degeneration, injection of BMP7 into the epidural space or the NPs relocated to the epidural space was shown to be safe [24], and dosages of 2 µg [25] or 100 µg [26] BMP7 per disc exerted regenerative effects.…”

Role of lncRNA PART1 in intervertebral disc degeneration and associated underlying mechanism

“…A number of reports have previously revealed that the inflammatory response and ECM degradation are the main characteristics of IDD, which are associated with the development of IDD (11)(12)(13). Inflammation is the leading cause of IDD development, with various inflammatory factors, including IL-6, TNF-α and IL-1β, being found to be upregulated in patients with IDD (47).…”

“…There are three types of cells that have been reported to be involved in IDD, namely endplate chondrocytes cells, inner and outer annulus fibrosus cells and the internal nucleus pulposus (NP) cells (8)(9)(10). During IDD progression, a variety of inflammatory factors and extracellular matrix (ECM) degradation products accumulate in NP tissues, which affect NP cell physiology and function (11).…”

Molecular basis of degenerative spinal disorders from a proteomic perspective (Review)

“…The activation of the PI3K/AKT pathway serves an important role in protecting cells from harmful physiological processes, such as cellular apoptosis, oxidative damage, and a hypoxic microenvironment, and has been found to protect against IDD (88). Furthermore, it was recently demonstrated that bone morphogenetic protein 2 can inhibit cellular apoptosis and suppress the synthesis of matrix proteins via the PI3K/AKT signaling pathway, which further alleviates IDD (89).…”