Dental pulp stem cells for reconstructing bone defects: A systematic review and meta-analysis

The role of mesenchymal stem cells-derived from oral and teeth in regenerative and reconstructive medicine

Defects and abnormalities of the skull, jaw, and face tissues due to various physiological problems such as speech, chewing, and swallowing disorders, cause illness and psychological effects with creation of significant public health challenges. Both autograft and allograft reconstruction methods, have different limitations, especially in the complete reconstruction of complex tissues such as sensory and periodontal tissues, which cannot be wholly relied on for treatment. Recently, mesenchymal stem cells (MSCs)-derived from oral and teeth have emerged as a promising alternative way in regenerative and reconstructive medicine. These types of stem cells with the high differentiation potential and self-renewal capabilities include dental pulp stem cells (DPSCs), stem cells from human exfoliated deciduous teeth (SHEDs), periodontal stem cells (PDLSCs) and gum-derived stem cells (GMSCs). These stem cells can be easily collected from accessible and numerous sources, such as extracted molars and milk teeth, with minimal invasiveness, playing pivotal roles in clinical application. This review explains the applications and therapeutic effects of the above-mentioned MSCs-derived from oral and dental tissues. Each of these stem cells, have unique characteristics and used for the treatment of specific abnormalities and defects. In this article, we aims to elucidate the indispensable and pivotal roles of MSCs-derived from the oral and teeth in addressing intractable and complex challenges in restorative and reconstructive medicine.

The Chick Embryo Chorioallantoic Membrane (CAM) Assay: A Novel Experimental Model in Dental Research

Animal experimental models are ruled out by respecting the 3Rs (Replacement, Reduction, Refinement) rules which governed the experimental research for decades with an increased tendency to minimize as much as it is possible any pain suffering or distress that the animals might feel. The chick embryo chorioallantoic membrane (CAM) model is an alternative to other experimental models due to its superior properties compared to other animal models. The CAM is painless by itself due to the lack of innervation and has no immune cells till the 11th day of incubation. Thus, it is extensively used for implanting malignant tumors and assessing them in relation to their metastatic and angiogenic potential. Also, various biomaterials from collagen to hard scaffolds can be implanted on the CAM surface and analyzed mainly related to their property of inducing inflammation. Dental research often uses mouse or rabbit models for experimental purposes. Different surgical techniques from experimentally induced periodontal disease to experimental dental implants may cause pain and suffering to animals. Due to all these arguments, the CAM model is a quick, cheap, and reliable alternative to other animal experimental models used in dental research. Despite its usefulness as an experimental model for different applications, ranging from inflammation studies to cancer research, the CAM model is insufficiently used in dental research. Currently, about 135 studies pertaining to this issue are available in PubMed, the majority of which focus on the reactivity of CAM vessels to various materials employed in dentistry. Limited data exist about the capacity of the CAM to promote osteogenic differentiation of dental stem cells or to enhance biomaterial integration into novel tissue architectures. The present review critically analyzed the use of the CAM model as an experimental tool in dental research. We selected from PubMed all the papers having as topic the CAM in dentistry by searching based on the following keywords: " chorioallantoic membrane, dentistry" or "chorioallantoic membrane, dental ". We focused on discussing the benefits and limitations of the CAM model in dental studies and its prospective role as a preclinical instrument for the assessment of dental tissues, biomaterials, or different dentistry-related substances prior to their use for various purposes in dental clinical practice. ​​​​​​The impact of the CAM model-derived preclinical findings on clinical practice will be also stated by mentioning "pros and cons" arguments. The last part of the present paper reviewed the perspective of CAM assay used in combination with other experimental techniques such as tooth organoids and also the strengths and weaknesses of other species CAM assays recently developed in ostrich and Nile crocodile CAMs.

RPLP0/TBP are the most stable reference genes for human dental pulp stem cells under osteogenic differentiation

BACKGROUND

Validation of the reference gene (RG) stability during experimental analyses is essential for correct quantitative real-time polymerase chain reaction (RT-qPCR) data normalisation. Commonly, in an unreliable way, several studies use genes involved in essential cellular functions [glyceraldehyde-3-phosphate dehydrogenase (GAPDH), 18S rRNA, and β-actin] without paying attention to whether they are suitable for such experimental conditions or the reason for choosing such genes. Furthermore, such studies use only one gene when Minimum Information for Publication of Quantitative Real-Time PCR Experiments guidelines recommend two or more genes. It impacts the credibility of these studies and causes distortions in the gene expression findings. For tissue engineering, the accuracy of gene expression drives the best experimental or therapeutical approaches.

AIM

To verify the most stable RG during osteogenic differentiation of human dental pulp stem cells (DPSCs) by RT-qPCR.

METHODS

We cultivated DPSCs under two conditions: Undifferentiated and osteogenic differentiation, both for 35 d. We evaluated the gene expression of 10 candidates for RGs [ribosomal protein, large, P0 (RPLP0), TATA-binding protein (TBP), GAPDH, actin beta (ACTB), tubulin (TUB), aminolevulinic acid synthase 1 (ALAS1), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta (YWHAZ), eukaryotic translational elongation factor 1 alpha (EF1a), succinate dehydrogenase complex, subunit A, flavoprotein (SDHA), and beta-2-microglobulin (B2M)] every 7 d (1, 7, 14, 21, 28, and 35 d) by RT-qPCR. The data were analysed by the four main algorithms, ΔCt method, geNorm, NormFinder, and BestKeeper and ranked by the RefFinder method. We subdivided the samples into eight subgroups.

RESULTS

All of the data sets from clonogenic and osteogenic samples were analysed using the RefFinder algorithm. The final ranking showed RPLP0/TBP as the two most stable RGs and TUB/B2M as the two least stable RGs. Either the ΔCt method or NormFinder analysis showed TBP/RPLP0 as the two most stable genes. However, geNorm analysis showed RPLP0/EF1α in the first place. These algorithms' two least stable RGs were B2M/GAPDH. For BestKeeper, ALAS1 was ranked as the most stable RG, and SDHA as the least stable RG. The pair RPLP0/TBP was detected in most subgroups as the most stable RGs, following the RefFinfer ranking.

CONCLUSION

For the first time, we show that RPLP0/TBP are the most stable RGs, whereas TUB/B2M are unstable RGs for long-term osteogenic differentiation of human DPSCs in traditional monolayers.

RPLP0/TBP are the most stable reference genes for human dental pulp stem cells under osteogenic differentiation

BACKGROUND

Validation of the reference gene (RG) stability during experimental analyses is essential for correct quantitative real-time polymerase chain reaction (RT-qPCR) data normalisation. Commonly, in an unreliable way, several studies use genes involved in essential cellular functions [glyceraldehyde-3-phosphate dehydrogenase (GAPDH), 18S rRNA, and β-actin] without paying attention to whether they are suitable for such experimental conditions or the reason for choosing such genes. Furthermore, such studies use only one gene when Minimum Information for Publication of Quantitative Real-Time PCR Experiments guidelines recommend two or more genes. It impacts the credibility of these studies and causes distortions in the gene expression findings. For tissue engineering, the accuracy of gene expression drives the best experimental or therapeutical approaches.

AIM

To verify the most stable RG during osteogenic differentiation of human dental pulp stem cells (DPSCs) by RT-qPCR.

METHODS

We cultivated DPSCs under two conditions: Undifferentiated and osteogenic differentiation, both for 35 d. We evaluated the gene expression of 10 candidates for RGs [ribosomal protein, large, P0 (RPLP0), TATA-binding protein (TBP), GAPDH, actin beta (ACTB), tubulin (TUB), aminolevulinic acid synthase 1 (ALAS1), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta (YWHAZ), eukaryotic translational elongation factor 1 alpha (EF1a), succinate dehydrogenase complex, subunit A, flavoprotein (SDHA), and beta-2-microglobulin (B2M)] every 7 d (1, 7, 14, 21, 28, and 35 d) by RT-qPCR. The data were analysed by the four main algorithms, ΔCt method, geNorm, NormFinder, and BestKeeper and ranked by the RefFinder method. We subdivided the samples into eight subgroups.

RESULTS

All of the data sets from clonogenic and osteogenic samples were analysed using the RefFinder algorithm. The final ranking showed RPLP0/TBP as the two most stable RGs and TUB/B2M as the two least stable RGs. Either the ΔCt method or NormFinder analysis showed TBP/RPLP0 as the two most stable genes. However, geNorm analysis showed RPLP0/EF1α in the first place. These algorithms’ two least stable RGs were B2M/GAPDH. For BestKeeper, ALAS1 was ranked as the most stable RG, and SDHA as the least stable RG. The pair RPLP0/TBP was detected in most subgroups as the most stable RGs, following the RefFinfer ranking.

CONCLUSION

For the first time, we show that RPLP0/TBP are the most stable RGs, whereas TUB/B2M are unstable RGs for long-term osteogenic differentiation of human DPSCs in traditional monolayers.

The impact of acemannan, an extracted product from Aloe vera, on proliferation of dental pulp stem cells and healing of mandibular defects in rabbits

OBJECTIVES

Dental pulp stem cells (DPSCs) were shown to play an important role in regenerative medicine including reconstruction of various bone lesions. This study determined the impact of acemannan, an extracted product from Aloe vera, on in vitro proliferation of DPSCs and in vivo healing of mandibular defects in rabbits.

METHODS

DPSCs were isolated and characterized. The growth kinetics of cells exposed to acemannan (8 mg/mL) and Hank's balanced salt solution (HBSS) were compared in vitro. Fifteen male rabbits were divided into 3 groups. Five animals were left as control group without any therapeutic intervention. Five rabbits were considered as experimental group 1 and received 20 µL of a cell suspension containing 106 DPSCs in the bone defect. Another 5 rabbits were regarded as experimental group 2 and were injected in the bone defect with 20 µL of a cell suspension containing 106 DPSCs treated with acemannan for 24 h. After 60 days, the animals were assessed by radiography and histologically.

RESULTS

The mesenchymal properties of DPSCs were confirmed. Population doubling time (PDT) of DPSCs treated with acemannan (29.8 h) was significantly shorter than cells were just exposed to HBSS (45.9 h). DPSCs together with acemannan could significantly accelerate the healing process and osteogenesis in mandibular defects.

CONCLUSIONS

As DPSCS showed an increased proliferation when treated with acemannan and accelerated the healing process in mandibular defects, these findings can open a new avenue in dentistry regenerative medicine when remedies of bone defects are targeted.

Evaluation of the efficacy of using dental pulp graft in the healing of the alveolar bone after impacted canine extraction: a prospective cohort study

Summary

The purpose of this study was to evaluate the radiographic density of the alveolar bone of the maxilla after extraction of the impacted canines and using the pulp tissue as an autogenous graft.

Materials and methods

This prospective cohort study recruited 14 patients (8 females and 6 males) between 2021 and 2023, with an average age of 35 years. All participants had palatally impacted maxillary canines. The impacted teeth were extracted surgically. The extracted teeth were then used for autogenous grafting. The pulp tissue was removed, cut into small pieces, and placed on an absorbable gelatin sponge before being inserted into the extraction socket. The wound was subsequently closed meticulously. After 4 months, the bone density was assessed radiographically using the Hounsfield Scale on cone beam computed tomography scans.

Results

After 4 months, the mean radiographic bone density value in the extraction area was (652.77 ± 56.13 HU), while the average density of the original bone was (659.7 ± 39.6 HU).

Conclusions

Within the limits of this study, dental pulp tissue can be used to restore bony defects of the alveolar bone in the maxilla. However, further research is needed to confirm these findings.