The misuse of steroid hormones is one of the primary factors contributing to femoral head necrosis (Wang et al. 2018c; Huang et al. 2021). Steroid-induced endothelial dysfunction leads to the disruption of blood supply to the femoral head, which progressively results in the robust upregulation of osteoclast-related proteins and localized bone tissue ischemia and necrosis (Maruyama et al. 2018; Chen et al. 2020).
The destruction of bone cells, coupled with the imbalance between osteogenesis and osteoclasis activities, ultimately leads to the degradation and collapse of the bone structure (Piuzzi et al. 2019). During this process, the disruption of the differentiation equilibrium in BMSCs represents a substantial pathological change (Powell et al. 2011; Chang et al. 2020). BMSCs with enhanced adipogenic potential not only forfeit their reparative capacity but also culminate in the catastrophic accumulation of adipocytes and increased intraosseous pressure within the femoral head, further exacerbating the progression of SONFH. In-depth investigations into the mechanisms underlying the differentiation disorder of SONFH-BMSCs are pivotal for a more comprehensive understanding of the pathogenesis of SONFH.
LncRNAs play an essential role in epigenetic regulation, employing mechanisms such as signal transduction, decoy, guidance, and scaffolding (Wang and Chang 2011; Mirzadeh Azad et al. 2021). In recent years, numerous efforts have been directed toward elucidating the differential expression profiles of various non-coding RNAs (ncRNAs), including lncRNAs and miRNAs, in SONFH-BMSCs (Table 3). Furthermore, a majority of studies have discovered that lncRNAs influence the differentiation lineage of BMSCs by modulating post-transcriptional mRNA levels via the competing endogenous RNA (ceRNA) mechanism. Our previous research conducted a screening of the lncRNA expression profile in human SONFH-BMSCs and hypothesized that the lncRNA MALAT1 could modulate the expression of DKK1, thereby influencing the osteogenic and adipogenic differentiation of BMSCs (Wang et al. 2018a). Wu et al. reported that lncRNA FGD5-AS1 regulates BMSCs proliferation and apoptosis by impacting the miR-296-5p/STAT3 axis in SONFH (Wu et al. 2022). Han et al. demonstrated that H19- hsa-miR-519b-3p/hsa-miR-296-5p-ANKH and lncRNA c9orf163- hsa-miR-424-5p-CCNT1 might play important roles in osteonecrosis of the femoral head development (Han and Li 2021). Our study shows H19 promotes the adipogenic differentiation of BMSCs and aggravates the progression of SONFH by miR-130b-3p/PPARγ Axis. As PPARγ is recognized as a transcription factor that facilitates adipogenic differentiation while inhibiting osteogenic differentiation (Cao 2011; Berhouma et al. 2013), our findings substantiated that the dysregulation of H19 contributes to the disruption of the equilibrium between adipogenic and osteogenic differentiation in ONFH, as well as illuminating its regulatory role. These newly identified SONFH-associated lncRNAs offer new insights not only for further elucidating the molecular regulatory mechanisms of SONFH but also for providing novel molecular markers and therapeutic targets for the diagnosis and treatment of femoral head necrosis.
Table 3. Functional characterization of the ncRNAs in SONFH
non-coding RNAs
|
Name
|
Expression
|
Functional role
|
Target miRNAs
|
Target genes
|
Sample
|
Reference
|
circRNA
|
circHGF
|
Up
|
suppress
proliferation and osteogenic differentiation of BMSCs
|
miR-25-3p
|
SMAD7
|
hBMSCs
(7 Male and 3 Female)
|
(Pan et al. 2021)
|
circRNA
|
circ_0058122
|
Up
|
increase dex-mediated HUVEC apoptosis
|
miR-7974
|
IGFBP5
|
Femoral head tissues (3 Male and 7 Female);HUVECs cells
|
(Yao et al. 2022)
|
LncRNA
|
LINC00473
|
Down
|
promote osteogenesis and suppress
the adipogenesis of BMSCs
|
miR-23a-3p
|
LRP5
|
hBMSCs
|
(Xu et al. 2022)
|
LncRNA
|
FGD5-AS1
|
Up
|
promote cell proliferation and restrain apoptosis
|
miR-296-5p/
|
STAT3
|
hBMSCs
|
(Wu et al. 2022)
|
LncRNA
|
NORAD
|
Down
|
promotion of proliferation and differentiation, and inhibition of apoptosis
|
miR-26a-5p
|
——
|
hBMSCs (20 patients)
|
(Fu et al. 2021)
|
LncRNA
|
RP11‐154D6
|
Down
|
promote BMSCs osteogenic differentiation and inhibit adipogenic differentiation
|
miR‐30a
|
——
|
hBMSCs (7 patients)
|
(Fu et al. 2021)
|
H19 was the first lncRNA to be identified and possesses a multitude of diverse biological functions, participating in the regulation of cellular proliferation, differentiation, and metabolism (Zhu et al. 2024). Previous studies have shown that H19 is involved in fat accumulation and regulation. The expression of H19 is augmented by fatty acids in hepatocytes and in diet-induced fatty liver, with the overexpression of H19 capable of promoting steatosis and enhancing lipid accumulation (Liu et al. 2018). Although Han et al. proposed a ceRNA network suggesting that H19 could act as a ceRNA for hsa-miR-519b-3p and hsa-miR-296-5p in ANKH (Han and Li 2021), this has yet to be substantiated by relevant experimental validation. In our study, H19 has been found to be aberrantly upregulated in both femoral head tissues and BMSCs. The relationship between H19 and miR-130b has been reported in the regulation of keratinocyte differentiation (Li et al. 2017) and in potentiating the effect of praziquantel on liver function (Ma et al. 2023); however, this relationship has not yet been explored in the context of SONFH. Motivated by these findings, we hypothesized that H19 could exert a regulatory influence on the progression of SONFH by functioning as a sponge for miR-130b-3p. Our investigations revealed that miR-130b-3p expression was increased following H19 knockdown. Additionally, we found an inverse correlation between PPARγ expression and miR-130b-3p levels. Through bioinformatics analysis and rescue experiments, we substantiated that miR-130b-3p could interact with both H19 and PPARγ. Collectively, our results suggest that H19 may modulate PPARγ expression by targeting miR-130b-3p.
Previous research has demonstrated that steroids have the capacity to upregulate the expression of PPARγ in both rodent and human BMSCs, thereby fostering adipogenic differentiation (Sheng et al. 2007). Our previous research also identified an association between gene variants of the transcription factor PPARγ and the development of osteonecrosis of the femoral head in the Chinese population. Our previous study found that association of gene variants of transcription factors PPARγ with the development of the femoral head osteonecrosis (Song et al. 2017). Several studies have also reported the abnormal expression and related regulatory effects of PPARγ in osteonecrosis of the femoral head (Zhao et al. 2019; Cui et al. 2022) (Fu et al. 2016). In the current study, discovered that PPARγ expression was notably elevated in both the femoral head tissues and BMSCs of patients with SONFH. Additionally, we found that miR-130b-3p regulates adipogenic differentiation by targeting PPARγ in the context of SONFH.
In summary, our findings reveal that elevated H19 expression is a characteristic molecular alteration in SONFH, and that H19 fosters BMSC adipogenic differentiation by enhancing PPARγ activity through the suppression of miR-130b-3p. Collectively, our study substantiates the regulatory function of lncRNAs in the progression of SONFH, positioning H19 as a pivotal and novel molecular target in the disease.
There were some limitations of our study. For instance, the number SONFH patients were small, which may have affected the lncRNA and mRNA expression results, more samples are needed to verify. Furthermore, luciferase reporter assays and animal experiments should be performed.