Enriching Stem/Progenitor Cells from Dental Pulp Cells by Low-density Culturing

Human Dental Pulp Cells form Spheroids in the Presence of Serum When Seeded on a Low-Attachment Cultural Surface

Spheroid formation is a characteristic feature of stem/progenitor cells. Under a serum-free cultural condition, human dental pulp cells can form spheroids. In the present study, we report that these cells can also form spheroids in the presence of serum when seeded on a low-attachment cultural surface. Dental pulp cells derived from three teeth were seeded with surface densities 103–105/cm2 in wells of low attachment and standard cultural plates. Fibroblasts were also seeded onto a low-attachment surface as a comparison. The growth of single spheroids of pulp cells was observed for 7 days. Pulp cells in spheroids and cells attached to the low-attachment surface were separated and further expanded on standard cultural surface in the monolayer and studied for their viability and osteogenic differentiation comparatively. In all three cultures of primary human dental pulp cells on low attachment surface, spheroids formed one day after seeding and grew in size over the 7 days of observation. The optimal seeding density for spheroids was around 104 cells/cm2 (105 cells/mL). Expanded pulp cells from the spheroids exhibited lower viability but higher osteogenic differentiation potential compared to pulp cells expanded from those attached to the surface of the low attachment plate. Human dental pulp cells have the specific capacity to forms spheroids when seeded on a low-attachment surface and may enable selection of a subpopulation with stronger differentiation potential and may also provide a strategy for culturing these cells in a three-dimensional organization without scaffolds.

Attachment and Osteogenic Potential of Dental Pulp Stem Cells on Non-Thermal Plasma and UV Light Treated Titanium, Zirconia and Modified PEEK Surfaces

Ultraviolet (UV) light and non-thermal plasma (NTP) treatment are chairside methods that can efficiently improve the biological aging of implant material surfaces caused by customary storage. However, the behaviors of stem cells on these treated surfaces of the implant are still unclear. This study aimed to investigate the effects of UV light and NTP treated surfaces of titanium, zirconia and modified polyetheretherketone (PEEK, BioHPP) on the attachment and osteogenic potential of human dental pulp stem cells (DPSCs) in vitro. Machined disks were treated using UV light and argon or oxygen NTP for 12 min each. Untreated disks were set as controls. DPSCs were cultured from the wisdom teeth of adults that gave informed consent. After 24 h of incubation, the attachment and viability of cells on surfaces were assessed. Cells were further osteogenically induced, alkaline phosphatase (ALP) activity was detected via a p-Nitrophenyl phosphate assay (day 14 and 21) and mineralization degree was measured using a Calcium Assay kit (day 21). UV light and NTP treated titanium, zirconia and BioHPP surfaces improved the early attachment and viability of DPSCs. ALP activity and mineralization degree of osteoinductive DPSCs were significantly increased on UV light and NTP treated surfaces of titanium, zirconia and also oxygen plasma treated Bio-HPP (p < 0.05). In conclusion, UV light and NTP treatments may improve the attachment of DPSCs on titanium, zirconia and BioHPP surfaces. Osteogenic differentiation of DPSCs can be enhanced on UV light and NTP treated surfaces of titanium and zirconia, as well as on oxygen plasma treated Bio-HPP.

Evaluation of the Effects of Human Dental Pulp Stem Cells on the Biological Phenotype of Hypertrophic Keloid Fibroblasts

OBJECTIVE

Despite numerous existing treatments for keloids, the responses in the clinic have been disappointing, due to either low efficacy or side effects. Numerous studies dealing with preclinical and clinical trials have been published about effective therapies for fibrotic diseases using mesenchymal stem cells; however, no research has yet been reported to scientifically investigate the effect of human dental pulp stem cells (HDPSCs) on the treatment of keloids. The objective is to provide an experimental basis for the application of stem cells in the treatment of keloids.

METHODS

Human normal fibroblasts (HNFs) and human keloid fibroblasts (HKFs) were cultured alone and in combination with HDPSCs using a transwell cell-contact-independent cell culture system. The effects of HDPSCs on HKFs were tested using a CCK-8 assay, live/dead staining assay, quantitative polymerase chain reaction, Western blot and immunofluorescence microscopy.

RESULTS

HDPSCs did not inhibit the proliferation nor the apoptosis of HKFs and HNFs. HDPSCs did, however, inhibit their migration. Furthermore, HDPSCs significantly decreased the expression of profibrotic genes (CTGF, TGF-β1 and TGF-β2) in HKFs and KNFs (p < 0.05), except for CTGF in HNFs. Moreover, HDPSCs suppressed the extracellular matrix (ECM) synthesis in HKFs, as indicated by the decreased expression of collagen I as well as the low levels of hydroxyproline in the cell culture supernatant (p < 0.05).

CONCLUSIONS

The co-culture of HDPSCs inhibits the migration of HKFs and the expression of pro-fibrotic genes, while promoting the expression of anti-fibrotic genes. HDPSCs' co-culture also inhibits the synthesis of the extracellular matrix by HKFs, whereas it does not affect the proliferation and apoptosis of HKFs. Therefore, it can be concluded that HDPSCs can themselves be used as a tool for restraining/hindering the initiation or progression of fibrotic tissue.

Inducing differentiation of human dental pulp cells toward acinar-lineage

OBJECTIVE

To induce acinar-differentiation from human dental pulp cells for potential application in aiding treatment of dry-eye syndromes.

METHOD

Human dental pulp cells were co-cultured with human submandibular gland acinar cells using a transwell construction for 2 weeks. The two populations of cells were physically separated while chemical and biochemical components can be exchanged. Fibroblasts were included as a negative control. Expression of amylase, cytokeratin 8 and vimentin were examined by immune-staining. Amylase activity was measured using an AMS Assay Kit.

RESULT

Cobblestone-like islands, a feature of acinar cells, appeared in the dental pulp cells which were co-cultured with salivary gland cells for one week and increased in number and size after two weeks. Antibody detected amylase in 30 and 50% of the pulp cells 1 and 2 weeks in the co-culture, respectively. Cytokeratin 8 increased while vimentin decreased. All these changes indicate an acinar-like differentiation of the dental pulp cells. None of these changes were observed in fibroblasts which were also co-cultured with salivary gland cells, indicating that the acinar-like differentiation is specific for the dental pulp cells. Neither of the changes were observed in dental pulp cells when not co-cultured with the salivary gland cells, indicating that induction is specific and essential.

CONCLUSIONS

Human dental pulp cells have the potential to differentiate into acinar-like cells which may provide an autologous source for cellular therapy for dry-eye syndromes.