Calreticulin Identified as One of the Androgen Response Genes That Trigger Full Regeneration of the Only Capable Mammalian Organ, the Deer Antler

Abstract

Deer antlers are male secondary sexual characters that develop to become bone; they are unique appendages that, once lost, can fully regenerate from the permanent bony protuberances or pedicles. Pedicle periosteum (PP) is the tissue that gives rise to the regenerating antlers with three differentiation stages, namely, dormant (DoPP), potentiated (PoPP), and activated (AcPP). Thus far, the transition from the PoPP to the AcPP has not been studied. Our results showed that the AcPP cells maintained their original stem cell features by expressing mesenchymal stem cell (MSC) markers CD73, CD90, and CD105, although they had entered the proliferation mode. The differentially expressed genes (DEGs) in the AcPP compared with those of the PoPP were mainly involved in protein processing, cell cycle, and calcium signaling pathways. Calreticulin (CALR), an androgen response gene, was significantly differentially upregulated in the AcPP cells, and its expression level was negatively regulated by androgens, in contrast to the currently known model systems where all regulation is positive. The downregulation of CALR expression in the AcPP cells in vitro inhibited cell proliferation, induced apoptosis, and inhibited cell cycle progression at G1-S transition. Therefore, CALR is likely a downstream mediator of androgen hormones for triggering initiation of antler regeneration. We believe that the identification of CALR has not only discovered “one critical piece” of the “jigsaw puzzle” in the initiation of antler regeneration but also helps in revealing the mechanism underlying this unique mammalian epimorphic regeneration and has also opened a new avenue for the study of the nature of CALR regulation by androgen (putative binding partners), thus facilitating the identification of potential molecule(s) for investigation as targets for clinical evaluation.

Conditioned media of deer antler stem cells accelerate regeneration of alveolar bone defects in rats

“…In our recent studies, AnSCs initiated antler regeneration though activating osteogenesis‐related pathways and upregulating bone formation‐related genes (e.g., RUNX2 and BMP4; Figure S3). 36 In the present study, expression levels of osteogenic marker genes both in vivo (OPG, RUNX2, CD163) in a rat model and in vitro (ALP, OCN, COL 1, OPN and Runx2) in a culture system for rBMSCs were significantly higher in the AnSC‐CM group than in the control group. Notably, expression levels of some genes were even significantly higher than in the hBMSC‐CM group.…”

“…PP tissue was obtained in a previous study 36 . Procedures for culturing the PP cells, that is, antler stem cells (AnSCs), were conducted as described previously 28 .…”

“…Cell proliferation was measured using the Cell Counting Kit‐8 (Solarbio, Beijing, China) according to the manufacturer's instructions. The colony formation assay was carried out using a reported methodology 36 . Briefly, 200 cells in 2 mL medium were seeded into each well of 6‐well plates and medium was replaced every 4 days after seeding; 14 days after culture the formed cell colonies were washed with PBS, fixed in 4% PFA for 30 min, and stained with 0.5% crystal violet dye for 5 min.…”

“…PP tissue was obtained in a previous study. 36 Procedures for culturing the PP cells, that is, antler stem cells (AnSCs), were conducted as described previously. 28 Human bone marrow mesenchymal stem cells (hBMSCs) were purchased from Guangzhou Cellbank Biotech Co., Ltd (Guangzhou, China).…”

“…The colony formation assay was carried out using a reported methodology. 36 Briefly, 200 cells in 2 mL medium were seeded into each well of 6-well plates and medium was replaced every 4 days after seeding; 14 days after culture the formed cell colonies were washed with PBS, fixed in 4% PFA for 30 min, and stained with 0.5% crystal violet dye for 5 min. Non-specific staining was removed via three rinses with double-distilled water, and the cells were photographed under a microscope (EVOS M5000, Thermo Fisher, USA).…”