Transcriptomic characterisation of the optimised rat model of Walker 256 breast cancer cell-induced bone pain

Analysis of Ionomic Profiles of Spinal Cords in a Rat Model with Bone Cancer Pain

Background

Ionomics is used to study levels of ionome in different states of organisms and their correlations. Bone cancer pain (BCP) severely reduces quality of life of patients or their lifespan. However, the relationship between BCP and ionome remains unclear.

Methods

The BCP rat model was constructed through inoculation of Walker 256 cells into the left tibia. Von Frey test, whole-cell patch-clamp recording and inductively coupled plasma mass spectrometry (ICP-MS) technologies were conducted for measuring tactile hypersensitivity, the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) of neurons of spinal slices, and ionome of spinal cord samples, respectively. Principal component analysis (PCA) was used to explore ionomic patterns of the spinal cord.

Results

The BCP rat model was successfully constructed through implantation of Walker 256 cells into the left tibia. The frequency and amplitude of mEPSCs of neurons in the spinal cord slices from the BCP model rats were notably greater than those in the sham control. In terms of ionomics, the spinal cord levels of two macroelements (Ca and S), four microelements (Fe, Mn, Li and Sr) and the toxic element Ti in the BCP group of rats were significantly increased by inoculation of Walker 256 cancer cells, compared to the sham control. In addition, the correlation patterns between the elements were greatly changed between the sham control and BCP groups. PCA showed that inoculation of Walker 256 cells into the tibia altered the overall ionomic profiles of the spinal cord. There was a significant separation trend between the two groups.

Conclusion

Taken together, inoculation of Walker 256 cells into the left tibia contributes to BCP, which could be closely correlated by some elements. The findings provided novel information on the relationship between the ionome and BCP.

Metformin Attenuates Bone Cancer Pain by Reducing TRPV1 and ASIC3 Expression

Bone cancer pain (BCP) is a common pathologic pain associated with destruction of bone and pathological reconstruction of nervous system. Current treatment strategies in clinical is inadequate and have unacceptable side effects due to the unclear pathology mechanism. In the present study, we showed that transplantation of Walker 256 cells aggravated mechanical allodynia of BCP rats (**p < 0.01 vs. Sham), and the expression of ASIC3 (Acid-sensitive ion channel 3) and TRPV1 was obviously enhanced in L4-6 dorsal root ganglions (DRGs) of BCP rats (**p < 0.01 vs. Sham). ASIC3 and TRPV1 was mainly expressed in CGRP and IB4 positive neurons of L4-6 DRGs. While, TRPV1 but not ASIC3 was markedly upregulated in L4-6 spinal dorsal horn (SDH) of BCP rats (**p < 0.01 vs. Sham). Importantly, intrathecal injection of CPZ (a TRPV1 inhibitor) or Amiloride (an ASICs antagonist) markedly increased the paw withdraw threshold (PWT) of BCP rats response to Von Frey filaments (**p < 0.01 vs. BCP + NS). What’s more, intraperitoneally injection of Metformin or Vinorelbine markedly elevated the PWT of BCP rats, but reduced the expression of TRPV1 and ASIC3 in L4-6 DRGs and decreased the TRPV1 expression in SDH (*p < 0.05, **p < 0.01 vs. BCP + NS). Collectively, these results suggest an effective analgesic effect of Metformin on mechanical allodynia of BCP rats, which may be mediated by the downregulation of ASIC3 and TRPV1.

Transcriptomic analysis of long noncoding RNAs and mRNAs expression profiles in the spinal cord of bone cancer pain rats

Bone cancer pain (BCP) is one of the most common types of chronic cancer pain and its pathogenesis has not been fully understood. Long non-coding RNAs (lncRNAs) are new promising targets in the field of pain research, however, their involvements in BCP have not been reported. In the present study, we established the BCP model by implantation of Walker 256 carcinoma cells into rats' tibial medullary cavity and performed transcriptome sequencing of the ipsilateral lumbar spinal cord to explore changes in expression profiles of lncRNA and mRNA. We identified 1220 differently expressed mRNAs (DEmRNAs) (1171 up-regulated and 49 down-regulated) and 323 differently expressed lncRNAs (DElncRNAs) (246 up-regulated and 77 down-regulated) in BCP model, among which 10 DEmRNAs (5 up-regulated and 5 down-regulated) and 10 DElncRNAs (5 up-regulated and 5 down-regulated) were validated the expression by RT-qPCR. Then, we performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis on the expression of DEmRNAs and DElncRNAs, showing that they were mainly enriched in inflammatory and immunologic processes/pathways. Finally, we constructed a co-expression network and a ceRNA network of DEmRNAs and DElncRNAs to exhibit a potential regulatory mechanism of DElncRNAs, directly regulating protein coding gene expression in cis or in trans and indirectly regulating protein coding gene expression by sponging miRNA. In conclusion, our study provided a landscape of dysregulated lncRNA and mRNA in spinal cord of bone cancer pain and detected novel potential targets for treatment in the future.