Long-term bone mineral density changes after surgical cure of patients with tumor-induced osteomalacia

This paper reports our personal experience filling the gap regarding changes of bone mineral density after surgical treatment in patient suffering from tumor-induced osteomalacia.

INTRODUCTION

No systematic data are available regarding long-term bone mineral density (BMD) changes after surgical cure of patients with tumor-induced osteomalacia.

METHODS

From October 2001 through April 2018, we studied 10 consecutive patients (mean age ± SD, 45.5 ± 13.8 years; 5 males and 5 females) with tumor-induced osteomalacia. We evaluated BMD when initially presented at our Center and after surgical removal of the tumor.

RESULTS

Basal BMD and corresponding Z-score values (mean values ± SD) measured by DXA were as follows: L₁-L₄ = 0.692 ± 0.15 g/cm², Z-score = - 2.80 ± 1.60; femur neck 0.447 ± 0.10 g/cm², Z-score = - 2.66 ± 0.93; total femur = 0.450 ± 0.08 g/cm², Z-score = -3.04 ± 0.85). Furthermore, Trabecular Bone Score (TBS) was evaluated in three patients (basal values, 0.990 ± 0.32). Seven patients were intermittently followed after surgical excision of the tumor while supplemented with cholecalciferol and calcium salts; the remaining three were lost to follow-up. There was a striking increase of BMD values that peaked at 26.7 ± 6.50 months: L₁-L₄ = 1.289 ± 0.247 g/cm², p < 0.001, Z-score + 1.75 ± 1.42; femur neck = 0.890 ± 0.235 g/cm², p = 0.028, Z-score = + 0.50 ± 1.40; total femur = 0.834 ± 0.150 g/cm², p = 0.005, Z-score = - 0.74 ± 1.14. In patients with the greatest bone involvement at lumbar site, there was a striking increase of an average 1.5% (p < 0.01) in respect to baseline Z-score value for each additional month of observation during the first 2-3 years post-surgery. An improvement of trabecular microarchitecture was also documented (TBS, 1.255 ± 0.16).

CONCLUSION

This is the first case series documenting an impressive increase of BMD at both lumbar and femoral sites, together with an improvement of trabecular microarchitecture as documented by TBS. This is the consequence of huge mineralization of the large amount of osteoid tissue after resolution of the disease.

Slug transcription factor and nuclear Lamin B1 are upregulated in osteoarthritic chondrocytes

OBJECTIVE

To contribute to clarify molecular mechanisms supporting senescence and de-differentiation of chondrocytes in chondrocyte pathologies such as osteoarthritis (OA). Specifically, we investigated the relationship between the nuclear lamina protein Lamin B1 and the negative regulator of chondrogenesis Slug transcription factor in osteoarthritic chondrocytes.

METHODS

Lamin B1 and Slug proteins were analyzed in cartilage explants from normal subjects and OA patients by immunohistochemical technique. Their expression was confirmed on isolated chondrocytes both at passage 0 and passage 2 (de-differentiated chondrocytes) by immunofluorescence and western blot. Subsequently, we explored the "in vivo" binding of Slug on LMNB1 promoter by chromatin immunoprecipitation assay (ChIP).

RESULTS

In this study we demonstrated that nuclear lamina protein Lamin B1 and anti-chondrogenic Slug transcription factor are upregulated in cartilage and OA chondrocytes. Furthermore, we found that Slug is "in vivo" recruited by LMNB1 gene promoter mostly when chondrocytes undergo de-differentiation or OA degeneration.

CONCLUSIONS

We described for the first time a potential regulatory role of Slug on the LMNB1 gene expression in OA chondrocytes. These findings may have important implications for the study of premature senescence, and degeneration of cartilage, and may contribute to develop effective therapeutic strategies against signals supporting cartilage damage in different subsets of patients.