Previous studies have shown that although they lose some of the properties of stem cells, DPSCs-IPs retain the potential for tissue regeneration [9, 10, 13].
In the present study, DPSCs-IPs were transplanted into the patients’ periodontal bone defects for the first time and the effective repairing effect was observed.
To date, only a few in-vivo studies in patients have been reported in oral tissue regeneration instead of only discussing the biological characteristics of the stem cells. There are many reasons for this lack of research, but what is at least certain is that normal dental stem cells need to be obtained from normal tissues, a process which itself would be new damage for patients. In this case, patients often refused the treatment. However, DPSCs-IPs themselves are derived from the inflammatory dental pulp tissues that are always taken as medical waste, so it is acceptable for patients to agree with this kind of treatment.
This study was the first to complete bone regeneration by autologous transplantation of DPSCs-IPs in patients. We objectively evaluated the characteristics of DPSCs-IPs in each patient first. The study found that inflammatory dental pulp tissues in both patients to a certain extent retain the properties of DPSCs: they can differentiate into osteogenic cells, and they express certain surface markers of mesenchymal stem cells. The expression levels in CD44 and CD90 are highly positive, and the levels in CD34 and CD45 are negative, which is in line with the characterization of mesenchymal stem cells. But the levels in CD105 and CD271 are weak, which slightly differs from previous reports [14–16]. However, the underlying reason remains unclear. The property of stem cell markers in different species or organs indeed differs in some cases . Using the expression levels in CD44, CD90, CD34, and CD45, however, the stem cell properties of DPSCs-IPs can be determined. The following discusses the therapeutic effect of DPSCs-IPs from many aspects. We have provided evidence here that the dental clinical condition was improved obviously 9 months after transplantation of the DPSCs-IPs/β-TCP complex. As observed in the clinic, the color of the gum is pink, and its quality is tough and elastic. Although there is only an inconspicuous improvement in GR, the PD was evidently shallow, the gingival BI decreased from 3 to 1, clinical hemorrhage disappeared, the root bifurcation lesions reduced to degree II–I compared with degree III before treatment, and the treatment effect was obvious from the current clinical symptoms. Generally speaking, the DPSCs-IPs/β-TCP autograft dramatically improved the clinical symptoms of periodontitis. Our results provide evidence that DPSCs-IPs/β-TCP compounds may have a certain repair effect on periodontal hard tissue defects caused by periodontitis and may be a new source for oral tissue regeneration to provide a potential way of being used in future clinical applications.
β-TCP has been used in tissue engineering for a long time, it has excellent bone conductibility, biological activity, and mechanical performance, and it has certain ability to repair bone defeats combined with stem cells [17–20]. In our study, DPSCs-IPs can be well engrafted into β-TCP, and no side effect or uncomfortable feelings appeared in patients after the transplantation. Therefore it is suggested that β-TCP can be used as a good carrier for tissue repair in the future.
In the view of safety in the process of transplantation, no patients showed any systemic disorders related to the transplantations or adverse reactions during the process, so the procedures used in this study can benefit DPSCs-IPs clinical studies in the future.
By further comparing the biological characteristics of DPSCs-IPs with two kinds of normal DPSCs, we found that although DPSCs-IPs can be isolated from inflammatory dental tissues, their growth state is inhibited to some extent due to the inflammatory source, which is in line with previous reports [21–23]. However, despite the decreased osteogenic ability compared with normal DPSCs, the ability to differentiate into osteogenic, adipogenic, and chondrogenic cells proved the characteristics of stem cells and suggests the potential of mesenchymal stem cells to repair defeats.
Despite these promising results, the flaws of this study reside mainly in the definite mechanism of DPSCs-IPs-mediated regeneration and the small number of patients enrolled. Future studies should concentrate on the specific mechanism of DPSCs-IPs-mediated tissue regeneration and include more clinical studies with large numbers of patients.