A facile turn-on chemiluminescence probe for sensitive imaging on aminopeptidase N activity.

Aminopeptidase N, as a target for drug discovery, shows marked relationships with many diseases, especially liver injury and cancer. Here, we explored a chemiluminescence (CL) probe for sensing APN by tethering the APN-specific substrate group to the ortho-acrylated phenoxy-dioxetane scaffold. In this way, two CL probes (APN-CL and BAPN-CL) were designed with noncapped leucine and butoxy-carbonyl capped leucine as the protecting group to preserve the chemiexcitation energy. The uncovered leucine was demonstrated to be essential for detection of APN activity by comparing the CL intensity of two CL probes. Probe APN-CL was turned on upon APN cleavage, resulting in a high chemiluminescent emission, whereas the chemiexcitation energy of probe BAPN-CL was still restrained even with the high-level APN. The result was further elucidated by molecular docking simulations. Probe APN-CL exhibited a fast response and high sensitivity with a detection limit of 0.068 U/L, and an excellent specificity for the discrimination of APN from biological ions, small molecules, and other proteases commonly found in living system. By virtue of good stability and cell viability, probe APN-CL imaged abnormal levels of APN in tumour cells and tumour-bearing mice. Moreover, this probe APN-CL could be easily used to evaluate APN inhibitors and APN levels in plasma samples from 20 patients. Overall, as a facile and cost-effective probe, APN-CL will be a promising alternative in the early diagnosis of pathologies and for cost-effective screening of inhibitors.

Aminopeptidase N Activatable Fluorescent Probe for Tracking Metastatic Cancer and Image-Guided Surgery via in Situ Spraying.

The recurrence of malignant tumors is mostly caused by incompleted surgical resection. Especially, it is difficult for surgeons to detect and accurately remove metastatic tumors by predominantly using visual examination and palpation owing to the lack of effective means to specifically distinguish the boundary range between normal and tumor tissues. Thus, the development of activated fluorescent probe with superior tumor-to-normal (T/N) tissue ratios is particularly urgent in clinics. In view of CD13/aminopeptidase N (APN) regarded as a cancer-specific biomarker, mediating with progression, invasion, and migration of malignant tumor, herein, we reported an APN-responsive fluorescent probe YH-APN and demonstrated its application to distinguish cancer cells. Through in situ spraying manner, fluorescent superior tumor-to-normal (T/N) tissue ratios (subcutaneous transplantation tumor, 13.86; hepatic metastasis, 4.42 and 6.25; splenic metastasis, 4.99) were achieved. More importantly, we have demonstrated the ability to image metastasis tumor tissue less than 1 mm in diameter, highlighting the potential for this probe to be used as a tool in surgical resection. This research may spur the use of enzyme-activatable fluorescent probes for the progress of tumor diagnosis and image-guided surgery (IGS).

Use of a Blast Dominance-Hematogone Index for the Flow Cytometric Evaluation of Myelodysplastic Syndrome (MDS).

OBJECTIVES: We tested whether combined flow cytometric assessment of loss of blast heterogeneity and decreased hematogones is a diagnostically useful approach for evaluation of myelodysplastic syndrome (MDS). METHODS: Bone marrow samples from patients with known MDS were analyzed by 10-color flow cytometric immunophenotyping and compared with normal bone marrow samples. RESULTS: There was loss of blast heterogeneity in patients with MDS compared with normal bone marrow samples, based on the relative size of the dominant blast population (83.0% vs 64.8%) and fewer hematogones (0.08% vs 1.39%). The size of the largest blast population divided by the fraction of hematogones (blast dominance-hematogone [BDH] index) was significantly larger in MDS compared with normal cases (27,084 vs 190, P < .0001; receiver operating characteristic area under the curve = 0.96). CONCLUSIONS: The BDH index is more sensitive and specific than loss of blast heterogeneity or decrease in hematogones for detecting MDS in bone marrow samples and may be useful in clinical practice.

Molecular Imaging of Aminopeptidase N in Cancer and Angiogenesis.

This review focuses on recent advances in the molecular imaging of aminopeptidase N (APN, also known as CD13), a zinc metalloenzyme that cleaves N-terminal neutral amino acids. It is overexpressed in multiple cancer types and also on the surface of vasculature undergoing angiogenesis, making it a promising target for molecular imaging and targeted therapy. Molecular imaging probes for APN are divided into two large subgroups: reactive and nonreactive. The structures of the reactive probes (substrates) contain a reporter group that is cleaved and released by the APN enzyme. The nonreactive probes are not cleaved by the enzyme and contain an antibody, peptide, or nonpeptide for targeting the enzyme exterior or active site. Multivalent homotopic probes utilize multiple copies of the same targeting unit, whereas multivalent heterotopic molecular probes are equipped with different targeting units for different receptors. Several recent preclinical cancer imaging studies have shown that multivalent APN probes exhibit enhanced tumor specificity and accumulation compared to monovalent analogues. The few studies that have evaluated APN-specific probes for imaging angiogenesis have focused on cardiac regeneration. These promising results suggest that APN imaging can be expanded to detect and monitor other diseases that are associated with angiogenesis.

Expression of CD56 defines a distinct subgroup in childhood T-ALL with inferior outcome. Results of the ALL-BFM 2000 trial.

This study reports the prognostic impact of the expression of the natural killer cell marker CD56 in a large series of risk-adapted paediatric patients with T cell acute lymphoblastic leukaemia (T-ALL; n = 493) treated within the ALL-Berlin-Frankfurt-Münster (BFM) 2000 protocol. The immunophenotype was analysed centrally at diagnosis using flow cytometry and correlated with clinical parameters and outcome. CD56 expression was detected in 7·1% and early T-cell precursor (ETP) phenotype in 6·7% of all T-ALL patients. The percentage of ETP in the CD56+ T-ALL cohort was 4-fold higher than in the whole cohort. CD56+ T-ALL frequently expressed the progenitor marker CD34 and myeloid antigens CD13 and CD33. The 5-year event-free survival (EFS) rates for the European Group for the Immunological classification of Leukaemias/World Health Organization subgroups and the ETP phenotype were not statistically different. By contrast, patients with CD56 expression had a significantly reduced EFS (60 ± 8%) and overall survival (60 ± 8%) at 5 years, with a hazard ratio of 2·46 (P = 0·002) and 2·99 (P < 0·001), respectively. Moreover, CD56 expression in combination with the minimal residual disease (MRD)-based high risk assignment defined a population with a 'very-high' risk probability of relapse in the ALL-BFM 2000 trial. The CD56 marker has the potential to augment MRD-based risk stratification and may serve as a molecular target for antibody-based treatment strategies in childhood T-ALL.

Non-Proximal Renal Tubule-Derived Urinary Exosomal miR-200b as a Biomarker of Renal Fibrosis.

BACKGROUND: Renal fibrosis is a common outcome of nearly all kinds of chronic kidney disease (CKD) and eventually progresses to end-stage renal disease. The identification of an optimal biomarker of renal fibrosis to replace the invasive renal biopsy will have important clinical implications. METHODS: We isolated urinary exosomes from 50 participants and examined the exosomal protein content and particle number in 38 CKD patients with different degrees of renal fibrosis and in 12 normal individuals. We examined the levels of exosomal microRNAs (miRNAs), namely, miR-200a, miR-200b, miR-200c, miR-141, miR-429, miR-29a, miR-29b, miR-29c, miR-192, and miR-21, by sorting the exosomes and comparing the levels of proximal tubular, non-proximal tubular, and total exosomal miR-200b. RESULTS: The exosome content was higher in the CKD group, but no differences were evident among the mild, moderate, and severe fibrosis groups. Among the 10 exosomal miRNAs, miR-200b was lower in the CKD group than in the normal group and decreased more significantly with fibrosis progression as well as in IgA nephropathy and diabetic kidney disease. CD13+ CD63+ exosomes constituted 18.6% of all urinary exosomes. Sorting the proximal tubular exosomes with the CD13 protein marker revealed that miR-200b in the CD13+ group was extremely low; however, the result was significantly different in the CD13- group but not in the CD13+ group. The magnitude of the decline was greater in the CD13- groups than in the non-sorted whole groups between the fibrosis and normal patients. CONCLUSIONS: Non-proximal renal tubule-derived urinary exosomal miR-200b is a biomarker of renal fibrosis. Exosomes can be used as a liquid biopsy and may replace the traditional invasive renal biopsy in the diagnosis of renal fibrosis.

Design, synthesis and application of a near-infrared fluorescent probe for in vivo imaging of aminopeptidase N.

We have, for the first time, developed a near-infrared fluorescent probe for aminopeptidase N by combining a hemicyanine and an alanyl residue. The probe exhibits high selectivity and sensitivity with a detection limit of 0.8 ng mL-1. With the probe, aminopeptidase N has been imaged in both cells and mice in vivo, indicating a promising tool for studying the function of the enzyme.

Juvenile myelomonocytic leukemia with prominent CD141+ myeloid dendritic cell differentiation.

Myeloid malignancies showing CD141+ myeloid dendritic cell (MDC) differentiation have not been documented. Here, we describe a patient with juvenile myelomonocytic leukemia in which a prominent CD141+ cell population was identified most consistent with CD141+ MDCs based on phenotypic similarity with normal CD141+ MDCs. Molecular studies demonstrated a KRAS mutation. The findings from the spleen and bone marrow are described. This is the first well-documented demonstration of CD141+ MDC differentiation of a hematopoietic neoplasm.

Ultrasensitive Detection of Aminopeptidase N Activity in Urine and Cells with a Ratiometric Fluorescence Probe.

An ultrasensitive ratiometric fluorescent probe (CVN) has been designed and synthesized by incorporating alanine into the cresyl violet fluorophore. The probe shows ratiometric fluorescence response toward aminopeptidase N (APN) through the increase of fluorescent intensity ratio of 626/575 nm. The sensitivity of the probe is ultrahigh with a detection limit of 33 pg/mL, which can quantify the contents of APN in 500-fold diluted human urine samples. Furthermore, by using ratiometric fluorescence imaging, the probe reveals significantly higher contents of APN in HepG2 cells than those in LO2 cells, which has been further used to distinguish these two types of cells in mixed cocultures. The probe could be of great importance for the APN-related disease diagnosis and pathophysiology elucidation.

Detection of l-alanylaminopeptidase activity in microorganisms using fluorogenic self-immolative enzyme substrates.

A series of fluorogenic enzymatic substrates that incorporate a self-immolative spacer were synthesised for the purpose of identifying l-alanylaminopeptidase activity in microorganisms in agar media. These substrates resulted in the generation of fluorescent microorganism colonies with Gram-negative microorganisms.

Evaluation of 68Ga-labeled iNGR peptide with tumor-penetrating motif for microPET imaging of CD13-positive tumor xenografts.

The aim of the study is to evaluate the efficacy of 68Ga-labeled iNGR, containing Asn-Gly-Arg (NGR) homing sequence and CendR (R/KXXR/K) penetrating motif, as a new molecular probe for microPET imaging of CD13-positive xenografts. The synthesized iNGR and NGR peptides were conjugated with DOTA and then labeled with 68Ga. 68Ga-iNGR and 68Ga-NGR were compared in the performance of the in vitro stability, partition coefficient, binding affinity, cell uptake analysis, in vivo microPET imaging, and biodistribution studies in CD13-positive HT-1080 and CD13-negative HT-29 cell lines. The in vitro results revealed that both probes exhibited high radiochemical purity and stability, and no significant difference between two probes was observed in terms of the binding affinity to CD13. In vivo microPET/CT imaging showed that the uptake of 68Ga-iNGR in HT-1080 tumor was significantly higher than that of 68Ga-NGR. Moreover, tumor 68Ga-iNGR uptake could be completely blocked by cold NGR and partially blocked by neutralizing NRP-1 antibody. We concluded that 68Ga-iNGR has a higher tumor uptake and better tumor retention than 68Ga-NGR through NRP-1, indicating that CendR motif modification is a promising method for improving NGR peptide performance.

Comparison of mesenchymal stem cells isolated from pulp and periodontal ligament.

BACKGROUND: Cell-based therapy using mesenchymal stem cells (MSCs) seems promising to obtain regeneration of dental tissues. A comparison of tissue sources, including periodontal ligament (PDL) versus pulp (P), could provide critical information to select an appropriate MSC population for designing predictable regenerative therapies. The purpose of this study is to compare the proliferation and stemness and the MSC-specific and mineralized tissue-specific gene expression of P-MSCs and PDL-MSCs. METHODS: MSCs were obtained from PDL and P tissue of premolars (n = 3) extracted for orthodontic reasons. MSC proliferation was evaluated using a real-time cell analyzer for 160 hours. Telomerase activity was evaluated by a telomeric repeat amplification protocol assay based on enzyme-linked immunosorbent assay. Total RNA was isolated from the MSCs on day 3. A polymerase chain reaction (PCR) array was used to compare the expression of MSC-specific genes. The expression of mineralized tissue-associated genes, including Type I collagen (COL I), runt-related transcription factor 2 (RunX2), bone sialoprotein (BSP), and osteocalcin (OCN) messenger RNA (mRNA), was evaluated using quantitative real-time PCR. RESULTS: Higher proliferation potential and telomerase activity were observed in the P-MSCs compared to PDL-MSCs of premolar teeth. Fourteen of 84 genes related to MSCs were expressed differently in the PDL-MSCs versus the P-MSCs. The expressions of bone morphogenetic protein 2 (BMP2) and BMP6; sex-determining region Y-box 9 (SOX9); integrin, alpha 6 (ITGA6); melanoma cell adhesion molecule (MCAM); phosphatidylinositol glycan anchor biosynthesis, class S (PIGS); prominin 1 (PROM1); ribosomal protein L13A (RPL13A); and microphthalmia-associated transcription factor (MITF) were higher in the P-MSCs compared to the PDL-MSCs, and higher expression of matrix metalloproteinase 2 (MMP2), interleukin (IL)-6, insulin (INS), alanyl (membrane) aminopeptidase (ANPEP), and IL-10 were observed in the PDL-MSCs. However, there was no statistically significant difference in the expression of mineralized tissue-associated genes, including BSP and RunX2, between the P-MSCs and the PDL-MSCs. Higher expression of COL I and lower expression of OCN mRNA transcripts were noted in the PDL-MSCs compared to the P-MSCs. CONCLUSIONS: The results of this study suggest that MSCs isolated from P and PDL tissues show different cellular behavior. To increase the predictability of MSC-based regenerative treatment, differences in dental tissue-derived MSCs and favorable aspects of cell sources should be further clarified.

Evaluation of 99mTc-probestin for imaging APN expressing tumors by SPECT.

Aminopeptidase N (APN) is known to play important roles in tumor angiogenesis, tumor cell invasion, and metastasis. Thus, APN is an attractive biomarker for imaging tumor angiogenesis. Here we report results obtained from biodistribution and single photon emission computed tomography (SPECT) imaging studies of a technetium-99m labeled probestin (a potent APN inhibitor) conjugate containing a tripeptide, Asp-DAP-Cys (DAP=2,3-diaminopropionic acid), chelator and a 8-amino-3,6-dioxaoctanoic acid (PEG2) linker conducted in nude mice xenografted with HT-1080 human fibrosarcoma tumors (APN-positive tumors). These results collectively demonstrate that (99m)Tc-probestin uptake by tumors and other APN expressing tissues in vivo is specific and validate the use of probestin as a vector for targeting APN in vivo.

CD13 is essential for inflammatory trafficking and infarct healing following permanent coronary artery occlusion in mice.

AIMS: To determine the role of CD13 as an adhesion molecule in trafficking of inflammatory cells to the site of injury in vivo and its function in wound healing following myocardial infarction induced by permanent coronary artery occlusion. METHODS AND RESULTS: Seven days post-permanent ligation, hearts from CD13 knockout (CD13(KO)) mice showed significant reductions in cardiac function, suggesting impaired healing in the absence of CD13. Mechanistically, CD13(KO) infarcts showed an increase in small, endothelial-lined luminal structures, but no increase in perfusion, arguing against an angiogenic defect in the absence of CD13. Cardiac myocytes of CD13(KO) mice showed normal basal contractile function, eliminating myocyte dysfunction as a mechanism of adverse remodelling. Conversely, immunohistochemical and flow cytometric analysis of CD13(KO) infarcts demonstrated a dramatic 65% reduction in infiltrating haematopoietic cells, including monocytes, macrophages, dendritic, and T cells, suggesting a critical role for CD13 adhesion in inflammatory trafficking. Accordingly, CD13(KO) infarcts also contained fewer myofibroblasts, consistent with attenuation of fibroblast differentiation resulting from the reduced inflammation, leading to adverse remodelling. CONCLUSION: In the ischaemic heart, while compensatory mechanisms apparently relieve potential angiogenic defects, CD13 is essential for proper trafficking of the inflammatory cells necessary to prime and sustain the reparative response, thus promoting optimal post-infarction healing.

Clinical importance of myeloid antigen expression in Moroccan patients with adult B-lineage acute lymphoblastic leukemia.

The prognostic significance of myeloid antigen (MyAg) expression in acute lymphoblastic leukemias (ALL), especially in adult patients, is still controversial. In the present report, frequency and clinical significance of MyAg (CD13 and/or CD33) in blast cells were assessed in 80 consecutive adult (≥18 years) patients with B-lineage acute lymphoblastic leukemia (B-ALL), representing 66.7% of 120 patients diagnosed as having ALL during the study period. Immunophenotyping was used to classify leukemic cells as Bor Tlymphoblasts and to identify the aberrant expression of myeloid-associated antigens. MyAg expression was documented in 52.5% of the 80 B-ALL cases analyzed. CD13 was the most commonly antigen expressed (36.3%) followed by CD33 (28.8%). No significant associations were found between the expression of MyAg and the presence of known adverse prognostic features (eg: age>30 years, male gender, high WBC count and Philadelphia positivity). Also, we failed to observe any statistically significant difference between MyAg-positive and MyAg-negative patients in terms of achievement of complete remission and overall survival at 3 years. This study demonstrates that the presence of MyAg on lymphoblastic cells lacks prognostic value In Moroccan patients with adult B-ALL.

Study of chemoresistant CD133+ cancer stem cells from human glioblastoma cell line U138MG using multiple assays.

Glioblastoma is one of the most common malignant tumours in adults, with an average life expectancy of less than 1 year. The high mortality of glioblastomas is attributed to its resistance to conventional chemotherapeutic agents. Numerous studies have established the presence of a cancer stem population within glioblastomas. These CSC (cancer stem cell) populations express the cell-surface marker, CD133, and are tumorigenic and chemoresistant. Hence, CSCs make a potential target for anticancer therapies. We have focused on techniques that can reliably identify and isolate a viable CSC population, and studied their chemoresistant attributes. We show the presence of a CSC population within a slowly proliferating glioblastoma cell line, U138MG. An improvised neurosphere enrichment culture technique was developed for the isolation of CSC population. Stem cell neurospheres obtained by this protocol maintained their viability for several weeks, and could be redispersed for deriving colony-forming units and secondary spheres from single-cell suspensions. RT-PCR (reverse transcription-PCR), cell surface localization by immunofluorescence and enumeration by FACS analysis showed that the sphere cultures of U138MG grown on agarose-coated plates had elevated CD133 levels. Drug sensitivity assays indicated that these enriched spheres were more resistant to drug treatment than their non-CSC controls. Drug-resistant CSC had an increased expression of ABC (ATP-binding-cassette) drug transporters, such as ABCC2, ABCC4, ABCG2 and p-glycoprotein, indicative of their role in the resistance mechanisms. These studies will facilitate the development of in vitro assays for the sparse CSC population and strategies for improved treatment regimens for glioblastomas.

Qualitative flow cytometric analysis of Malaysian myelodysplastic syndromes (MDS) patients.

Myelodysplastic syndromes (MDS) are a group of haematological malignancies categorized by ineffective hematopoiesis that result in dysplasia. Although morphological diagnosis is a traditional and standard technique that is used for the diagnosis of MDS, the heterogeneous blood and bone marrow characteristics of MDS patients can potentially obscure the right diagnosis. Thus, we have utilized flow cytometric immunophenotyping as a supportive mechanism to obtain a more accurate and faster method for detection of abnormal markers in MDS. Flow cytometry was used for analyzing bone marrow samples from newly diagnosed MDS patients to investigate the abnormal antigen expression patterns in granulocytic, monocytic, erythroid, lymphoid lineages and myeloid precursors. The results were compared with those obtained from cases that had Idiopathic Thrombocytopenic Purpura (ITP) as a control. The most common abnormality found in the granulocytic lineage was the decrease of CD10. Low expressions of CD13 were the most frequent abnormality in the monocytic lineage. The erythroid lineage was found to have low expression of CD235A+/CD71+, reduce of CD71 and decreased CD235a. In conclusion, this method is useful for confirming cases in which it is difficult to make a diagnosis by morphology.

A human coronavirus responsible for the common cold massively kills dendritic cells but not monocytes.

Human coronaviruses are associated with upper respiratory tract infections that occasionally spread to the lungs and other organs. Although airway epithelial cells represent an important target for infection, the respiratory epithelium is also composed of an elaborate network of dendritic cells (DCs) that are essential sentinels of the immune system, sensing pathogens and presenting foreign antigens to T lymphocytes. In this report, we show that in vitro infection by human coronavirus 229E (HCoV-229E) induces massive cytopathic effects in DCs, including the formation of large syncytia and cell death within only few hours. In contrast, monocytes are much more resistant to infection and cytopathic effects despite similar expression levels of CD13, the membrane receptor for HCoV-229E. While the differentiation of monocytes into DCs in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4 requires 5 days, only 24 h are sufficient for these cytokines to sensitize monocytes to cell death and cytopathic effects when infected by HCoV-229E. Cell death induced by HCoV-229E is independent of TRAIL, FasL, tumor necrosis factor alpha, and caspase activity, indicating that viral replication is directly responsible for the observed cytopathic effects. The consequence of DC death at the early stage of HCoV-229E infection may have an impact on the early control of viral dissemination and on the establishment of long-lasting immune memory, since people can be reinfected multiple times by HCoV-229E.

Biochemical analysis of cystic fluid in the diagnosis of fetal intra-abdominal masses.

OBJECTIVE: The aim of the study was to evaluate a biochemical analysis of fluid sampled in utero from fetal abdominal cystic masses. METHODS: A retrospective study of 42 intra-abdominal cystic masses [ovarian cysts (n = 22), cloaca (n = 8), urodigestive fistulae (n = 4), and urogenital sinuses (n = 8)] was carried out. The control group (n = 30) consisted of fetal urine. Seven biochemical markers were assayed: sodium, estradiol, ß(2) -microglobulin, total proteins and digestive enzymes, gamma-glutamyl transpeptidase, aminopeptidase M, and intestinal alkaline phosphatase isoenzyme. Outcome of pregnancies and final diagnosis of intra-abdominal mass were known in all cases. RESULTS: Biochemical patterns allowed to demonstrate (1) an ovarian origin based on elevated level of estradiol and of total proteins (100% specificity, 100% sensitivity); (2) urodigestive fistula based on the presence of high levels of digestive enzymes (cloaca in female fetuses or recto-urethral fistula in male fetuses); and (3) a renal origin (urinary pattern with low total proteins and absence of digestive enzymes); however, a biochemical pattern could not differentiate between fetal urogenital sinus and megacystis. CONCLUSION: Etiological diagnosis of a fetal cystic abdominal mass could impact both prenatal and postnatal management providing adapted prenatal counseling by a pediatric surgeon in surgically correctable congenital anomalies.

Comparison of immuno-phenotypes of stem cells from human dental pulp and periodontal ligament.

It has been established that human dental pulp and periodontal ligament contain a population of mesenchymal stem cells (MSCs). However, the phenotypic analysis in terms of putative stem cell markers expressed by these stem cell populations is incomplete. It is relevant to understand whether stem cells derived from closely related tissues are programmed differently. The aim of the present study is to analyze whether these stem cells depict distinct characteristics by gaining insight into differences in their immunophenotype. Dental pulp and periodontal ligament tissue samples were obtained from extracted impacted wisdom teeth. Cell cultures were analyzed for surface and intracellular markers by indirect immunoflourescence. Detailed immunophenotype analysis was carried out by flow cytometry using relevant markers. The present study data shows dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) expressed embryonic stem (ES) cell markers Oct-4, Nanog and mesodermal marker Vimentin by indirect immunoflourescence. PDLSCs, however, had a weak expression of Nanog. Immunophenotyping revealed strong expression of MSC markers (CD73, CD90) in DPSCs and PDLSCs. Differences were observed in expression of stemness-related markers. DPSCs displayed increased percentages of SSEA4, CD13 and CD166 and decreased CD9 expression compared to PDLSCs. Both stem cells express common MSC markers, different levels of expression suggests there might be more than one stem cell population existing within these tissues which differ in their embryonic status, and DPSCs are a more primitive stem cell population in comparison to PDLSCs.