Myristic acid beneficially modulates intervertebral disc degeneration by preventing endplate osteochondral remodeling and vertebral osteoporosis in naturally aged mice

Background: The origin of intervertebral disc degeneration (IDD) is
highly complex, where both cartilage endplate remodeling and
vertebral osteoporosis are of utmost importance. Myristic acid
(MA), a saturated fatty acid derived from nutmeg, a traditional
Chinese herb, has been shown to boost memory. Additionally, its
isomers have been verified to have
antiosteoporotic characteristics. However, the precise mechanism
by which MA functions in relation to IDD remains unclear.
Methods: In vivo, a natural aging animal model was used.
The drug—administration method of MA was intraperitoneal
injection to mice aged 22 months at a dose of 2 mg/kg·d for 2
months. Micro-CT observed vertebral bone mass and endplate
changes, followed by Hematoxylin‒eosin (H&E), Masson, and
Safranin-O staining of tissues. TRAP staining counted
osteoclasts; immunohistochemistry detected the expressions of
Aggrecan and Collagen II. Bioinformatics explored MA’s anti-IDD
mechanism. In vitro, MA-treated senescent endplate chondrocytes
(induced by TBHP) were analyzed by Real-Time PCR (qPCR) and
immunofluorescence (IF) for senescence and matrix synthesis
markers. TRAP and F-actin detected MA’s effect on RAW264.7
osteoclast differentiation (induced by RANKL); qPCR examined
the expressions of osteoclast genes. Results: Using the natural
aging model, we found that MA tended to
improve vertebral osteoporosis and endplate
osteochondral remodeling, decreased the TRAP activity of the
endplate, and alleviated IDD in naturally aging
mice. Bioinformatics analysis suggested that the relationships
among IDD, osteoporosis, and endplate degeneration were mainly
linked to cellular senescence. In vitro, MA postponed the
senescence of TBHP-induced endplate chondrocytes by increasing
the expression of aggrecan and decreasing the expressions of
MMP-3, MMP-9, and the senescence markers p16 and
p21. Additionally, MA notably inhibited osteoclast activity, as
evidenced by a decrease in the number of osteoclasts and a
significant suppression of F-actin formation. At the molecular
level, MA efficiently reduced the expressions of osteoclast
marker genes like ACP-5, CTSK, and DC-STAMP. Conclusion: The
findings of this research suggest that MA is capable of inhibiting
endplate osteochondral remodeling and vertebral osteoporosis, diminishing
osteoclastogenesis to preserve bone mass, and consequently delaying IDD in
naturally aging mice. Hence, MA holds the potential to serve as an
alternative therapeutic approach for IDD.