# Knockdown of the UL-16 binding protein 1 promotes osteoblast differentiation of human mesenchymal stem cells by activating the SMAD2/3 pathway

## TL;DR

This study shows that reducing ULBP1 in human stem cells boosts bone cell development, suggesting it could be a new treatment for osteoporosis.

## Contribution

The novel finding is that ULBP1 suppression promotes osteoblast differentiation via the TNF-β signaling pathway in mesenchymal stem cells.

## Key findings

- ULBP1 is upregulated in osteoporosis and downregulated in differentiated human mesenchymal stem cells.
- Knockdown of ULBP1 increases osteoblast differentiation markers like ALP activity and mineralization.
- Rescue experiments confirm that ULBP1 suppression activates the TNF-β signaling pathway.

## Abstract

Osteoporosis is caused by the imbalance of osteoblasts and osteoclasts. The regulatory mechanisms of differentially expressed genes (DEGs) in pathogenesis of osteoporosis are of significant and needed to be further investigated. GSE100609 dataset downloaded from Gene Expression Omnibus (GEO) database was used to identified DEGs in osteoporosis patients. KEGG analysis was conducted to demonstrate signaling pathways related to enriched genes. Osteoporosis patients and the human mesenchymal stem cells (hMSCs) were obtained for in vivo and in vitro resaerch. Lentivirus construction and viral infection was used to knockdown genes. mRNA expression and protein expression were detected via qRT-PCR and western blot assay separately. Alkaline phosphatase (ALP) activity detection, alizarin Red S (ARS) staining, and expression of bone morphogenetic protein 2 (BMP2), osteocalcin (OCN) and Osterix were evaluated to determine osteoblast differentiation capacity. UL-16 binding protein 1 (ULBP1) gene was upregulated in osteoporosis and downregulated in differentiated hMSCs. Knockdown of ULBP1 increased ALP activity, mineralization ability evaluated by ARS staining, expression of BMP2, OCN and Osterix in differentiated hMSCs. Furthermore, rescue experiment demonstrated that suppressed ULBP1 boosted osteoblast differentiation by activating TNF-β signaling pathway. Knockdown of ULBP1 gene could promoted osteoblast differentiation by activating TNF-β signaling pathway in differentiated hMSCs. ULBP1 may be a the Achilles’ heel of osteoporosis, and suppression of ULBP1 could be a promising treatment for osteoporosis.

The online version contains supplementary material available at 10.1186/s12891-024-07341-0.