In Vitro Control of Genes Critical for Parathyroid Embryogenesis by Extracellular Calcium

Thyroid and parathyroid function disorders induced by short-term exposure of microplastics and nanoplastics: Exploration of toxic mechanisms and early warning biomarkers

Human exposure to micro- and nano-plastics (MNPs) primarily occurs through respiration and diet in the environment. However, the early effects and warning signs of MNPs exposure on vertebrates are unclear. Here we used intratracheal instillation and intragastric infusion to establish mouse models for MNPs exposure to systematically investigate the toxic mechanisms of MNPs on endocrine organs. Results showed that MNPs induced endocrine disruptions in short-term exposure by both dietary and respiratory pathways. Microplastics (MPs) exposed through dietary route were more toxic to thyroid gland, whereas nanoplastics (NPs) exhibited the highest level of toxicity to parathyroid gland through respiration. The transcriptome and validation of related functional genes revealed that MNPs affected the synthesis of thyroglobulin by interfering with the expressions of PAX8 and CREB. MNPs also impacted the levels of thyroid stimulating hormone, further mediating the secretion of thyroid hormones. Moreover, MNPs modulate the expression of Mafb, thereby exerting regulatory effects on parathyroid hormone (PTH) synthesis and growth development in parathyroid cells. Meanwhile, MNPs interfered with the expression of IP3R in the calcium signaling pathway, indirectly affecting the secretion of PTH. This study reveals the effects and mechanisms of MNPs on thyroid and parathyroid and highlights the significance of early warning of MNPs exposure.

Potential impacts of SARS-CoV-2 on parathyroid: current advances and trends

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection affects several important organs including endocrine glands. Experimental studies demonstrated that the virus exploits the ACE2, a transmembrane glycoprotein on the cell surface as a receptor for cellular entry. This entry process is exclusively facilitated by other intracellular protein molecules such as TMPRSS2, furin, NRP1, and NRP2. Recent findings documented the involvement of the SARS-CoV-2 in inducing various parathyroid disorders including hypoparathyroidism and hypocalcemia, which received significant attention. This review extensively describes rapidly evolving knowledge on the potential part of SARS-CoV-2 in emerging various parathyroid disorders due to SARS-CoV-2 infection particularly parathyroid malfunction in COVID-19 cases, and post-COVID-19 conditions. Further, it presents the expression level of various molecules such as ACE2, TMPRSS2, furin, NRP1, and NRP2 in the parathyroid cells that facilitate the SARS-CoV-2 entry into the cell, and discusses the possible mechanism of parathyroid gland infection. Besides, it explores parathyroid malfunction in COVID-19 vaccine-administered cases. It also explains the possible long-COVID-19 effect on parathyroid and post-COVID-19 management of parathyroid. A complete understanding of the mechanisms of SARS-CoV-2-triggered pathogenesis in parathyroid dysfunctions may curtail treatment options and aid in the management of SARS-CoV-2-infected cases.

Establishment and characterization of long-term human primary parathyroid tumor subclones derived from Indian PHPT

The continuous cell line of epithelial human parathyroid cells has been proven difficult. Previously, PTH-C1 cell line was only established rat parathyroid tissue cell line known to express the parathyroid hormone-related peptide (Pthrp) gene. The paucity of continuous cell line of human parathyroid cells secreting parathyroid hormone (PTH) has imposed hurdle in in vitro assessment of the mechanisms involved in the control of parathyroid cell function and proliferation. The primary cell cultures of human parathyroid cells were derived from parathyroid adenoma tissue biopsy (n = 5). The cells were subsequently subcultured to maintained primary subclones. Karyotyping analysis was performed to analyze the genotypic identity of derived subclones. The expression of calcium-sensing receptor (CaSR) and intact parathyroid hormone (iPTH) were analyzed using immunocytochemistry and immunofluorescence. In the present study, we have used a defined condition medium to generate the continuous culture of human parathyroid cells derived from patients with parathyroid adenoma due to primary hyperparathyroidism. The subcultured primary subclones were maintained epithelial and polygonal morphology, doubling time of approximately 25 h, displaying a diploid chromosome number, and secretion of PTH. This cell line produces PTH and expresses the calcium-sensing receptor (CaSR) known to be involved in parathyroid function. Altogether these findings indicate the uniqueness of the human parathyroid cell line as an in vitro model for cellular and molecular studies on parathyroid physiopathology.

GCM2 Silencing in Parathyroid Adenoma Is Associated With Promoter Hypermethylation and Gain of Methylation on Histone 3

CONTEXT

Glial cells missing 2 (GCM2), a zinc finger-transcription factor, is essentially required for the development of the parathyroid glands.

OBJECTIVE

We sought to identify whether the epigenetic alterations in GCM2 transcription are involved in the pathogenesis of sporadic parathyroid adenoma. In addition, we examined the association between promoter methylation and histone modifications with disease indices.

METHODS

Messenger RNA (mRNA) and protein expression of GCM2 were analyzed by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry in 33 adenomatous and 10 control parathyroid tissues. DNA methylation and histone methylation/acetylation of the GCM2 promoter were measured by bisulfite sequencing and chromatin immunoprecipitation-qPCR. Additionally, we investigated the role of epigenetic modifications on GCM2 and DNA methyltransferase 1 (DNMT1) expression in parathyroid (PTH)-C1 cells by treating with 5-aza-2'-deoxycytidine (DAC) and BRD4770 and assessed for GCM2 mRNA and DNMT1 protein levels.

RESULTS

mRNA and protein expression of GCM2 were lower in sporadic adenomatous than in control parathyroid tissues. This reduction correlated with hypermethylation (P < .001) and higher H3K9me3 levels in the GCM2 promoter (P < .04) in adenomas. In PTH-C1 cells, DAC treatment resulted in increased GCM2 transcription and decreased DNMT1 protein expression, while cells treated with the BRD4770 showed reduced H3K9me3 levels but a nonsignificant change in GCM2 transcription.

CONCLUSION

These findings suggest the concurrent association of promoter hypermethylation and higher H3K9me3 with the repression of GCM2 expression in parathyroid adenomas. Treatment with DAC restored GCM2 expression in PTH-C1 cells. Our results showed a possible epigenetic landscape in the tumorigenesis of parathyroid adenoma and also that DAC may be a promising avenue of research for parathyroid adenoma therapeutics.

Study of the Expression and Function of Calcium-Sensing Receptor in Human Skeletal Muscle

Skeletal muscle has an outstanding capacity for regeneration in response to injuries, but there are disorders in which this process is seriously impaired, such as sarcopenia. Pharmacological treatments to restore muscle trophism are not available, therefore, the identification of suitable therapeutic targets that could be useful for the treatment of skeletal reduced myogenesis is highly desirable. In this in vitro study, we explored the expression and function of the calcium-sensing receptor (CaSR) in human skeletal muscle tissues and their derived satellite cells. The results obtained from analyses with various techniques of gene and protein CaSR expression and of its secondary messengers in response to calcium (Ca²⁺) and CaSR drugs have demonstrated that this receptor is not present in human skeletal muscle tissues, neither in the established satellite cells, nor during in vitro myogenic differentiation. Taken together, our data suggest that, although CaSR is a very important drug target in physiology and pathology, this receptor probably does not have any physiological role in skeletal muscle in normal conditions.