Conditioned medium of human mesenchymal stem cells affects stem cell senescence in osteoporosis.

Systemic transplantation of mesenchymal stem cells (MSCs) and conditioned medium derived from MSCs have been reported to recover bone loss in animal models of osteoporosis; however, the underlying mechanisms remain unclear. We recently reported that extracellular vesicles released from human mesenchymal stem cells (hMSCs) prevent senescence of stem cells in bisphosphonate-related osteonecrosis of the jaw model. In this study, we aimed to compare the effects of conditioned medium (hMSCs-CM) from early and late passage hMSCs on cellular senescence and to verify the benefits of CM from early passage hMSCs in mitigating the progression of osteoporosis through the prevention of cellular senescence. We investigated the distinct endocrine effects of early (P5) and late (P17) passage hMSCs in vitro, as well as the preventive benefits of early passage hMSCs-CM in osteoporosis model triggered by ovariectomy. Our results indicate that long-term cultured hMSCs contributed to the progression of inflammatory transcriptional programs in P5 hMSCs, ultimately impairing their functionality and enhancing senescence-related characteristics. Conversely, early passage hMSCs reversed these alterations. Moreover, early passage hMSCs-CM infused intravenously in a postmenopausal osteoporosis mouse model suppressed bone degeneration and prevented osteoporosis by reducing ovariectomy-induced senescence in bone marrow MSCs and reducing the expression of senescence-associated secretory phenotype-related cytokines. Our findings highlight the high translational value of early passage hMSCs-CM in antiaging intervention and osteoporosis prevention.

Cellular senescence is associated with osteonecrosis of the femoral head while mesenchymal stem cell conditioned medium inhibits bone collapse.

Osteonecrosis of the femoral head (ONFH) is a type of ischemic osteonecrosis that causes pain, loss of function, and femoral head collapse. Here, we analyzed samples of femoral heads excised from patients with ONFH to clarify the relationship between ischemic osteonecrosis and cellular senescence. X-gal staining was strong and p16INK4a-positive cells were abundant in the transitional region of ONFH. The ß-galactosidase-positive cells in the transitional region were also positive for nestin, periostin, or DMP-1. In contrast, no ß-galactosidase-positive cells were detected in the healthy region. The senescence-associated p16INK4a, p21, and p53 were upregulated in ONFH tissue. We also examined and analyzed a mouse ischemic femoral osteonecrosis model in vivo to verify the association between ONFH and cellular senescence. Human mesenchymal stem cell-conditioned medium (MSC-CM) was administered to determine its therapeutic efficacy against cellular senescence and bone collapse. MSC-CM reduced the number of senescent cells and downregulated the aforementioned senescence-related genes. It also decreased the number of empty lacunae 4 weeks after ischemia induction and promoted bone formation. At 6 weeks post-surgery, MSC-CM increased the trabecular bone volume, thereby suppressing bone collapse. We conclude that cellular senescence is associated with ONFH and that MSC-CM suppresses bone collapse in this disorder.

Dental pulp stem cell-derived small extracellular vesicle in irradiation-induced senescence.

Small extracellular vesicles (sEV) facilitate signaling molecule transfer among cells. We examined the therapeutic efficacy of human dental pulp stem cell-derived sEV (hDPSC-sEV) against cellular senescence in an irradiated-submandibular gland mouse model. Seven-week-old mice were exposed to 25 Gy radiation and randomly assigned to control, phosphate-buffered saline (PBS), or hDPSC-sEV groups. At 18 days post-irradiation, saliva production was measured; histological and reverse transcription-quantitative PCR analyses of the submandibular glands were performed. The salivary flow rate did not differ significantly between the PBS and hDPSC-sEV groups. AQP5-expressing acinar cell numbers and AQP5 expression levels in the submandibular glands were higher in the hDPSC-sEV group than in the other groups. Furthermore, compared with non-irradiated mice, mice in the 25 Gy + PBS group showed a high senescence-associated-ß-galactosidase-positive cell number and upregulated senescence-related gene (p16INK4a, p19Arf, p21) and senescence-associated secretory phenotypic factor (MMP3, IL-6, PAI-1, NF-κB, and TGF-ß) expression, all of which were downregulated in the hDPSC-sEV group. Superoxide dismutase levels were lower in the PBS group than in the hDPSC-sEV group. In summary, hDPSC-sEV reduced inflammatory cytokine and senescence-related gene expression and reversed oxidative stress in submandibular cells, thereby preventing irradiation-induced cellular senescence. Based on these results, we hope to contribute to the development of innovative treatment methods for salivary gland dysfunction that develops after radiotherapy for head and neck cancer.

Peripheral Nerve Regeneration in a Novel Rat Model of Dysphagia.

The superior laryngeal nerve (SLN) is known to play an essential role in the laryngeal reflex and swallowing. Damage to the SLN causes difficulty swallowing, that is, dysphagia. We successfully developed a novel rat model of dysphagia by SLN injury, in which we could evaluate the neuroregenerative capacity of stem cell from human exfoliated deciduous teeth (SHED). The dysphagic rats exhibit weight loss and altered drinking patterns. Furthermore, SLN injury induces a delayed onset of the swallowing reflex and accumulation of laryngeal debris in the pharynx. This rat model was used to evaluate the systemic application of SHED-conditioned medium (SHED-CM) as a therapeutic candidate for dysphagia. We found that SHED-CM promoted functional recovery and significant axonal regeneration in SLNs through the polarization shift of macrophages from activated inflammatory macrophages (M1) to anti-inflammatory macrophages (M2) and angiogenesis. This chapter describes the establishment of SLN-injury induced dysphagia rat model and the preparation and application of SHED-CM.

Dental pulp-derived stem cell conditioned medium to regenerate peripheral nerves in a novel animal model of dysphagia.

In nerve regeneration studies, various animal models are used to assess nerve regeneration. However, because of the difficulties in functional nerve assessment, a visceral nerve injury model is yet to be established. The superior laryngeal nerve (SLN) plays an essential role in swallowing. Although a treatment for SLN injury following trauma and surgery is desirable, no such treatment is reported in the literature. We recently reported that stem cells derived from human exfoliated deciduous teeth (SHED) have a therapeutic effect on various tissues via macrophage polarization. Here, we established a novel animal model of SLN injury. Our model was characterized as having weight loss and drinking behavior changes. In addition, the SLN lesion caused a delay in the onset of the swallowing reflex and gain of laryngeal residue in the pharynx. Systemic administration of SHED-conditioned media (SHED-CM) promoted functional recovery of the SLN and significantly promoted axonal regeneration by converting of macrophages to the anti-inflammatory M2 phenotype. In addition, SHED-CM enhanced new blood vessel formation at the injury site. Our data suggest that the administration of SHED-CM may provide therapeutic benefits for SLN injury.

Clinical Study of Bone Regeneration by Conditioned Medium From Mesenchymal Stem Cells After Maxillary Sinus Floor Elevation.

OBJECTIVE: This clinical study was undertaken to evaluate the safety of use of the secretome of bone marrow-derived mesenchymal stem cells (MSC-CM) for maxillary sinus floor elevation (SFE). MATERIALS AND METHODS: MSC-CM was prepared from conditioned medium from human bone marrow-derived MSCs. Six partially edentulous patients were enrolled in the study. MSC-CM was mixed with porous beta-tricalcium phosphate (ß-TCP) and implanted in 4 patients (experimental group), whereas only ß-TCP was implanted in the other 2 patients (control group). Six months after SFE, bone biopsies and histological assessments were performed. RESULTS: Bone formation was clinically confirmed in all cases. Although Hounsfield units in computed tomography images were not significantly different between the groups, histological analysis revealed a significant difference in newly formed bone area between the groups. In particular, bone volume in the center of the augmented area was significantly greater in the MSC-CM group. Newly formed bone consisted of lamellar bone in the MSC-CM group but woven bone in the ß-TCP group. CONCLUSION: The secretome of bone marrow-derived mesenchymal stem cells (MSC-CM) was used safely and has great osteogenic potential for regenerative medicine of bone.