Dihydrotanshinone I attenuates estrogen-deficiency bone loss through RANKL-stimulated NF-κB, ERK and NFATc1 signaling pathways

Postmenopausal osteoporosis, a chronic condition that predominantly affects postmenopausal women, presents a significant impediment to their overall well-being. The condition arises from estrogen deficiency, leading to enhanced osteoclast activity. Salvia miltiorrhiza, a well-established Chinese herbal medicine with a history of clinical use for osteoporosis treatment, contains diverse active constituents that have shown inhibitory effects on osteoclast formation and bone loss. Dihydrotanshinone I (DTI), a phenanthrenonequinone compound derived from the root of Salvia miltiorrhiza, has been identified as a potential therapeutic agent, although its mechanism of action on osteoclasts remains elusive. In this study, we aimed to elucidate the inhibitory potential of DTI on RANKL-induced osteoclastogenesis. We observed the ability of DTI to effectively impede the expression of key osteoclast-specific genes and proteins, as assessed by Real-time PCR and Western Blotting analyses. Mechanistically, DTI exerted its inhibitory effects on osteoclast formation by modulating critical signaling pathways including NF-κB, ERK, and calcium ion signaling. Notably, DTI intervention disrupted the nuclear translocation and subsequent transcriptional activity of the NFATc1, thus providing mechanistic insights into its inhibitory role in osteoclastogenesis. To further assess the therapeutic potential of DTI, we employed an ovariectomized osteoporosis animal model to examine its impact on bone loss. Encouragingly, DTI demonstrated efficacy in mitigating bone loss induced by estrogen deficiency. In conclusion, our investigation elucidates the ability of DTI to regulate multiple signaling pathways activated by RANKL, leading to the inhibition of osteoclast formation and prevention of estrogen-deficiency osteoporosis. Consequently, DTI emerges as a promising candidate for the treatment of osteoporosis.

Impaired autophagy triggered by HDAC9 in mesenchymal stem cells accelerates bone mass loss

Background

Bone mass loss in aging is linked with imbalanced lineage differentiation of bone marrow mesenchymal stem cells (BMMSCs). Recent studies have proved that histone deacetylases (HDACs) are regarded as key regulators of bone remodeling. However, HDACs involve in regulating BMMSC bio-behaviors remain elusive. Here, we investigated the ability of HDAC9 on modulation of autophagy and its significance in lineage differentiation of BMMSCs.

Methods

The effects of HDAC9 on lineage differentiation of BMMSCs and autophagic signaling were assessed by various biochemical (western blot and ChIP assay), morphological (TEM and confocal microscopy), and micro-CT assays.

Results

Sixteen-month mice manifested obvious bone mass loss and marrow fat increase, accompanied with decreased osteogenic differentiation and increased adipogenic differentiation of BMMSCs. Further, the expression of HDAC9 elevated in bone and BMMSCs. Importantly, HDAC9 inhibitors recovered the lineage differentiation abnormality of 16-month BMMSCs and reduced p53 expression. Mechanistically, we revealed that HDAC9 regulated the autophagy of BMMSCs by controlling H3K9 acetylation in the promoters of the autophagic genes, ATG7, BECN1, and LC3a/b, which subsequently affected their lineage differentiation. Finally, HDAC9 inhibition improved endogenous BMMSC properties and promoted the bone mass recovery of 16-month mice.

Conclusions

Our data demonstrate that HDAC9 is a key regulator in a variety of bone mass by regulating autophagic activity in BMMSCs and thus a potential target of age-related bone loss treatment.

Radiomorphometric indices of mandibular bones in an 18th century population

OBJECTIVE

To estimate four radiomorphometric indices of mandibular bones in an 18th century population sample, and possibly associate the findings with bone mass loss related to sex, age, nutritional habits and pathologies reflecting on the bone.

DESIGN

Thirty-six sculls (31 males, 5 females), recovered from the crypt of Požega Cathedral in Croatia were analyzed. Age estimation was based on tooth wear, and Eichner class was determined according to the number of occlusal supporting zones. The parameters in recording analogue orthopantomographs were set to constant current of 16 mA, exposure time of 14.1s, and voltage between 62-78 kV. Films were processed in an automatic dark chamber processor for 12 min, and digitized at 8-bit, 300 dpi. The thickness of the mandibular cortex was assessed below the mental foramen (MI), at antegonion (AI), at gonion (GI). Qualitative mandibular cortical index (MCI) was assessed.

RESULTS

Average values of MI, AI and GI were 3.97 ± 0.94 mm, 2.98 ± 0.56 mm, and 1.99 ± 0.55 mm, respectively. Statistically significant differences between males and females were found for AI right (p=0.014), GI left (p=0.010) and GI average (p=0.006), and were in all cases higher in males. There were no statistically significant differences between age groups for either index (p>0.05). Considering Eichner classification the differences were not significant for MI (p=0.422), AI (p=0.516), and GI (p=0.443), but in Eichner classes II, MCI was significantly higher (p=0.02).

CONCLUSION

The obtained data does not suggest generalized malnutrition or calcium, phosphorus and vitamin D deprivation in the historic population studied.