The abortive SARS-CoV-2 infection of osteoclast precursors promotes
their differentiation into osteoclasts
Abstract
The COVID-19 pandemic has resulted in the loss of millions of lives,
although a majority of those infected have managed to survive.
Consequently, a set of outcomes, identified as long COVID, is now
emerging. While the primary target of SARS-CoV-2 is the respiratory
system, the impact of COVID-19 extends to various body parts, including
the bone. This study aims to investigate the effects of acute SARS-CoV-2
infection on osteoclastogenesis, utilizing both ancestral and Omicron
viral strains. Monocyte-derived macrophages (MDM), which serve as
precursors to osteoclasts, were exposed to both viral variants. However,
the infection proved abortive, even though ACE2 receptor expression
increased post-infection, with no significant impact on cellular
viability and redox balance. Both SARS-CoV-2 strains heightened
osteoclast formation in a dose-dependent manner, as well as CD51/61
expression and bone resorptive ability. Notably, SARS-CoV-2 induced
early pro-inflammatory M1 macrophage polarization, shifting towards an
M2-like profile. Osteoclastogenesis-related genes (RANK, NFATc1,
DC-STAMP, MMP9) were upregulated, and surprisingly, SARS-CoV-2 variants
promoted RANKL-independent osteoclast formation. This thorough
investigation illuminates the intricate interplay between SARS-CoV-2 and
osteoclast precursors, suggesting potential implications for bone
homeostasis and opening new avenues for therapeutic exploration in
COVID-19.