Efficacy and Mechanism of Highly Active Umbilical Cord Mesenchymal Stem Cells in the Treatment of Osteoporosis in Rats
Authors: Tian Chuan , Lv Guanke , Ye Li , Zhao Xiaojuan , Chen Mengdie , Ye Qianqian , Li Qiang , Zhao Jing , Zhu Xiangqing , Pan Xinghua 
Published: February 2024

Background:
Osteoporosis increases bone brittleness and the risk of fracture. Umbilical
cord mesenchymal stem cell (UCMSC) treatment is effective, but how to improve the biological
activity and clinical efficacy of UCMSCs has not been determined.

Methods:
A rat model of osteoporosis was induced with dexamethasone sodium phosphate. Highly
active umbilical cord mesenchymal stem cells (HA-UCMSCs) and UCMSCs were isolated, cultured,
identified, and infused intravenously once at a dose of 2.29 × 106 cells/kg. In the 4th week
of treatment, bone mineral density (BMD) was evaluated via cross-micro-CT, tibial structure was
observed via HE staining, osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs)
was examined via alizarin red staining, and carboxy-terminal cross-linked telopeptide
(CTX), nuclear factor-κβ ligand (RANKL), procollagen type 1 N-terminal propeptide (PINP) and
osteoprotegerin (OPG) levels were investigated via enzyme-linked immunosorbent assays
(ELISAs). BMMSCs were treated with 10-6 mol/L dexamethasone and cocultured with HA-UCMSCs
and UCMSCs in transwells. The osteogenic and adipogenic differentiation of BMMSCs was
subsequently examined through directional induction culture. The protein expression levels of
WNT, β-catenin, RUNX2, IFN-γ and IL-17 in the bone tissue were measured via Western blotting.

Results:
The BMD in the healthy group was higher than that in the model group. Both UCMSCs
and HA-UCMSCs exhibited a fusiform morphology; swirling growth; high expression of CD73,
CD90 and CD105; and low expression of CD34 and CD45 and could differentiate into adipocytes,
osteoblasts and chondrocytes, while HA-UCMSCs were smaller in size; had a higher nuclear
percentage; and higher differentiation efficiency. Compared with those in the model group,
the BMD increased, the bone structure improved, the trabecular area, number, and perimeter increased,
the osteogenic differentiation of BMMSCs increased, RANKL expression decreased, and
PINP expression increased after UCMSC and HA-UCMSC treatment for 4 weeks. Furthermore,
the BMD, trabecular area, number and perimeter, calcareous nodule counts, and OPG/RANKL ratio
were higher in the HA-UCMSC treatment group than in the UCMSC treatment group. The osteogenic
and adipogenic differentiation of dexamethasone-treated BMMSCs was enhanced after
the coculture of UCMSCs and HA-UCMSCs, and the HA-UCMSC group exhibited better effects
than the UCMSC coculture group. The protein expression of WNT, β-catenin, and runx2 was upregulated,
and IFN-γ and IL-17 expression was downregulated after UCMSC and HA-UCMSC
treatment.

Conclusion::
HA-UCMSCs have a stronger therapeutic effect on osteoporosis compared with that
of UCMSCs. These effects include an improved bone structure, increased BMD, an increased
number and perimeter of trabeculae, and enhanced osteogenic differentiation of BMMSCs via activation
of the WNT/β-catenin pathway and inhibition of inflammation.