Role of CD271 enrichment in the isolation of mesenchymal stromal cells from umbilical cord blood

Study of the relation between serum levels of long-acting penicillin and the inflammatory markers: C-reactive protein and interleukin-6 in patients with chronic rheumatic heart disease

Background

There is an evidence of a chronic inflammatory state in patients with chronic rheumatic valvular heart disease (RHD) as shown by high serum levels of high-sensitivity C-reactive protein (hs-CRP) and interleukin-6 (IL6). Despite the efficacy of long-acting penicillin (LAP) in secondary prevention of rheumatic fever, its effect on this inflammatory state is still unknown. So, we sought to study the effect of LAP on the inflammatory markers, CRP and IL-6, in patients with chronic rheumatic heart disease.

Results

Eighty RHD patients coming to our hospital’s outpatient clinic for rheumatic fever secondary prophylaxis by regular administration of LAP were enrolled in the study. Patients were divided into 3 groups: group A, 70 patients with RHD already on prophylactic LAP, group B, 10 patients with RHD who have not yet started prophylactic LAP, and group C, control group of 10 healthy individuals not known to have RHD. Serum levels of LAP, IL-6, and CRP were measured for the three groups.

Group A had significantly lower IL-6 levels than group B (25.22 ± 33.50 vs. 126.1 ± 33.76nng/ml, respectively, p < 0.0001). IL-6 levels were significantly lower in control subjects compared to patients in group B (3.600 ± 2.319, 25.22 ± 33.50 ng/ml, respectively, p < 0.0001). However, IL-6 levels in the control group were lower but non-significantly different compared to group A. CRP level was lower in group A than group B (8419 ± 4935 vs. 14400 ± 3375 mg/dl, respectively, p = 0.0002). CRP levels were significantly lower in control subjects compared to patients in group A and group B. IL-6 values were positively correlated with CRP values (r = 0.6387, p < 0.0001).

CRP values were negatively correlated with LAP values (r = -0.5277, p < 0.0001). IL-6 values were negatively correlated with LAP values (r = − 0.4401, p < 0.0001). There was a highly significant difference between LAP level in compliant and non-compliant patients (1.045 ± 1.270 vs. 0.0785 ± 0.1057 ng/ml, respectively, p value < 0.0001).

There was also a highly significant difference between CRP level in compliant and non-compliant patients (7640 ± 4558 vs. 13090 ± 4717 mg/dl, respectively, p = 0.005). Moreover, there was a significant difference between IL-6 levels in compliant and non-compliant patients (21.53 ± 32.70 vs. 47.40 ± 30.91 ng/ml, respectively, p value 0.03).

Conclusion

Serum LAP has a strong negative correlation with IL-6 and CRP levels. Regular administration of LAP strongly ameliorates the inflammatory state seen in patients with RHD.

Nerve growth factor (NGF) and NGF receptors in mesenchymal stem/stromal cells: Impact on potential therapies

Mesenchymal stem/stromal cells (MSCs) are promising for the treatment of degenerative diseases and traumatic injuries. However, MSC engraftment is not always successful and requires a strong comprehension of the cytokines and their receptors that mediate the biological behaviors of MSCs. The effects of nerve growth factor (NGF) and its two receptors, TrkA and p75NTR, on neural cells are well studied. Increasing evidence shows that NGF, TrkA, and p75NTR are also involved in various aspects of MSC function, including their survival, growth, differentiation, and angiogenesis. The regulatory effect of NGF on MSCs is thought to be achieved mainly through its binding to TrkA. p75NTR, another receptor of NGF, is regarded as a novel surface marker of MSCs. This review provides an overview of advances in understanding the roles of NGF and its receptors in MSCs as well as the effects of MSC‐derived NGF on other cell types, which will provide new insight for the optimization of MSC‐based therapy.

Isolation and characterization of neural crest-like progenitor cells in human umbilical cord blood

Introduction

Neural crest (NC)-like stem/progenitor cells provide an attractive cell source for regenerative medicine because of their multipotent property and ease of isolation from adult tissue. Although human umbilical cord blood (HUCB) is known to be a rich source of stem cells, the presence of the NC-like stem/progenitor cells in HUCB remains to be elucidated. In this study, we have isolated NC-like progenitor cells using an antibody to p75 neurotrophin receptor (p75NTR) and examined their phenotype and stem cell function in vitro.

Methods

To confirm whether p75NTR⁺ NC-derived cells are present in cord blood, flow cytometric analysis of cord blood derived from P0-Cre/Floxed-EGFP reporter mouse embryos was performed. Freshly isolated HUCB mononuclear cells was subjected to flow cytometry to detect p75NTR⁺ cells and determined their immunophenotype. HUCB p75NTR⁺ cells were then collected by immunomagnetic separation and their immunophenotype, clonogenic potential, gene expression profile, and multilineage differentiation potential were examined.

Results

NC-derived EGFP⁺ cells co-expressing p75NTR was detected in cord blood of P0-Cre/Floxed-EGFP reporter mice. We found that freshly isolated HUCB mononuclear cells contained 0.23% of p75NTR⁺ cells. Isolated p75NTR⁺ cells from HUCB efficiently formed neurospheres and could differentiate into neuronal and glial cell lineages. The p75NTR⁺ cells expressed a set of NC-associated genes and undifferentiated neural cell marker genes before and after the culture.

Conclusions

These findings revealed that HUCB contained the p75NTR⁺ NC-like progenitor cell population which have the self-renewal capacity and the potential to differentiate into both neuronal and glial cell lineages.

Comprehensive analysis of skeletal muscle- and bone-derived mesenchymal stem/stromal cells in patients with osteoarthritis and femoral neck fracture

BACKGROUND

Mesenchymal stem/stromal cells (MSCs) can replenish the aged cells of the musculoskeletal system in adult life. Stem cell exhaustion and decrease in their regenerative potential have been suggested to be hallmarks of aging. Here, we investigated whether muscle- and bone-derived MSCs of patients with osteoarthritis and osteoporosis are affected by this exhaustion, compared to healthy donors.

METHODS

Patients with primary osteoarthritis, femoral neck fractures due to osteoporosis, and healthy donors (controls) were included. MSCs were isolated from the skeletal muscle and subchondral bone from each patient and compared using ex vivo and in vitro analyses, including immunophenotyping, colony-forming unit fibroblast assays, growth kinetics, cell senescence, multilineage potential, and MSC marker gene expression profiling.

RESULTS

Freshly isolated cells from muscle from patients with osteoarthritis showed a lower proportion of CD45/CD19/CD14/CD34-negative cells compared to patients with osteoporosis and healthy donors. Freshly isolated muscle cells from patients with osteoarthritis and osteoporosis also showed higher clonogenicity compared to healthy donors. MSCs from both tissues of osteoarthritis patients showed significantly reduced osteogenesis and MSCs from the bone also reduced adipogenesis. Chondrogenic pellet diameter was reduced in bone-derived MSCs from both patient groups compared to healthy donors. A significant positive correlation was observed between adipogenesis and CD271 expression in muscle-derived MSCs. CD73 was significantly lower in bone-derived MSCs from osteoarthritis patients, compared to osteoporosis patients. Gene expression profiling showed significantly lower expression of MSC marker gene leptin receptor, LEPR, previously identified as the major source of the bone and adipocytes in the adult bone marrow, in bone-derived MSCs from patients with osteoarthritis in comparison with osteoporotic patients and healthy donors.

CONCLUSIONS

Our results show deficient ex vivo and in vitro properties of both skeletal muscle- and bone-derived MSCs in osteoarthritis and osteoporosis patients, compared to healthy donors. In bone-derived MSCs from patients with osteoarthritis, we also identified a lower expression of the leptin receptor, a marker of MSCs that present a major source of MSCs in the adult bone marrow. This suggests that exhaustion of skeletal muscle- and bone-derived MSCs is a hallmark of osteoarthritis and osteoporosis, which defines the need for further clinical trials of stem cell transplantation in these patients.

Is There a Noninvasive Source of MSCs Isolated with GMP Methods with Better Osteogenic Potential?

BACKGROUND

A new trend in the treatment for alveolar clefts in patients with cleft lip and palate involves the use of bone tissue engineering strategies to reduce or eliminate the morbidity associated with autologous bone grafting. The use of mesenchymal stem cells-autologous cells obtained from tissues such as bone marrow and fat-combined with various biomaterials has been proposed as a viable option for use in cleft patients. However, invasive procedures are necessary to obtain the mesenchymal stem cells from these two sources. To eliminate donor site morbidity, noninvasive stem cell sources such as the umbilical cord, orbicularis oris muscle, and deciduous dental pulp have been studied for use in alveolar cleft bone tissue engineering. In this study, we evaluate the osteogenic potential of these various stem cell types.

METHODS

Ten cellular strains obtained from each different source (umbilical cord, orbicularis oris muscle, or deciduous dental pulp) were induced to osteogenic differentiation in vitro, and the bone matrix deposition of each primary culture was quantified. To evaluate whether greater osteogenic potential of the established mesenchymal stem cell strains was associated with an increase in the expression profile of neural crest genes, real-time qPCR was performed on the following genes: SRY-box 9, SRY-box 10, nerve growth factor receptor, transcription factor AP-2 alpha, and paired box 3.

RESULTS

The mesenchymal stem cells obtained from deciduous dental pulp and orbicularis oris muscle demonstrated increased osteogenic potential with significantly more extracellular bone matrix deposition when compared to primary cultures obtained from the umbilical cord after twenty-one days in culture (p = 0.007 and p = 0.005, respectively). The paired box 3 gene was more highly expressed in the MSCs obtained from deciduous dental pulp and orbicularis oris muscle than in those obtained from the umbilical cord.

CONCLUSION

These results suggest that deciduous dental pulp and orbicularis oris muscle stem cells demonstrate superior osteogenic differentiation potential relative to umbilical cord-derived stem cells and that this increased potential is related to their neural crest origins. Based on these observations, and the distinct translational advantage of incorporating stem cells from noninvasive tissue sources into tissue engineering protocols, greater study of these specific cell lines in the setting of alveolar cleft repair is indicated.

Purification of Stem Cells from Oral Pyogenic Granuloma Tissue

Introduction:

The isolation of stem cells from pathologically damaged dental tissues has been examined only by a few studies. The purpose of this study was to evaluate the possibility of isolation of stem cells from pyogenic granuloma.

Methods:

Pyogenic granuloma tissues were enzymatically digested and the resulting single cells were cultured. Then, the cultured cells differentiated into adipocytes and osteoblasts cells. Flow cytometry analyses were performed on markers such as CD 90, CD 73, CD105, CD 45 and CD14. Other features were also analyzed including the effect of colony formation and potentials of differentiation into adipocytes and osteoblasts.

Results:

The cells derived from pyogenic granuloma tissue formed higher colonies similar to typical spindle-shaped fibroblasts. The cells were positive for mesenchymal markers such as CD 44, CD 271, CD 90, and CD 73, and negative for surface molecules such as CD 14, CD 34 and CD 45. Moreover, they successfully differentiated into adipocytes and osteoblasts.

Conclusion:

The cells isolated from pyogenic granuloma could form CFU fibroblastic units expressing an appropriate marker panel of the cell surface antigen and adequate differentiation potential, all of which met the Cell Therapy International Association criteria for the definition of mesenchymal stromal cells. Pyogenic granuloma contains cells with stem cell properties.

Low-affinity Nerve Growth Factor Receptor (CD271) Heterogeneous Expression in Adult and Fetal Mesenchymal Stromal Cells

Human multipotent mesenchymal stromal cells (MSC) are isolated from a plethora of tissue sources for cell therapy purposes. In 2006, the International Society for Cellular Therapy (ISCT) published minimal guidelines to define MSC identity. Nevertheless, many independent studies demonstrated that cells meeting the ISCT criteria possessed heterogeneous phenotypes and functionalities, heavily influenced by culture conditions. In this study, human MSC derived from many adult (bone marrow and adipose tissue) or fetal (cord blood, Wharton's jelly, umbilical cord perivascular compartment and amniotic fluid) tissues were investigated. Their immunophenotype was analyzed to define consistent source-specific markers by extensive flow cytometry analysis and real-time qRT-PCR. CD271⁺ subpopulations were detected in adult MSC, whereas NG2 was significantly more expressed in fetal MSC but failed validation on independent samples coming from an external laboratory. The highest number of CD271⁺ adult MSC were detected soon after isolation in serum-based culture conditions. Furthermore, heterogeneous percentages of CD271 expression were found in platelet lysate-based or serum-free culture conditions. Finally, CD271⁺ adult MSC showed high clonogenic and osteogenic properties as compared to CD271^- cells. To conclude, in this phenotype-function correlation study CD271⁺ subpopulation confers heterogeneity on adult MSC, confirming the need of more specific markers to address MSC properties.

The association of plasma high-sensitivity C-reactive protein level with rheumatic heart disease: The possible role of inflammation

Background

Currently, it is not clear whether recurrent traumatic events lead to progression of rheumatic heart disease (RHD) after the incident of acute rheumatic fever or a persistent inflammatory state at the site of the valves. The aim of this study was to assess the possible association between plasma high sensitive C Reactive Protein (hs-CRP) level as an indicator of inflammation and RHD.

Materials & methods

Ninety patients with RHD and 90 healthy controls who had undergone complete echocardiographic examination were enrolled in this cross-sectional study. A score was given to each patient according to the severity of valvular involvement. Plasma hs-CRP level was checked for each patient by ELISA method twice with two-week interval, and the mean hs-CRP was calculated.

Results

The mean plasma hs-CRP level in the case group was significantly higher compared to its level in the control group (2.59 ± 4.82 and 0.55 ± 0.43 in the case and control groups respectively, p < 0.001). There was also a strong association between the level of plasma hs-CRP and the severity of rheumatic valvular involvement (p < 0.001).

Conclusion

The mean plasma hs-CRP level seems to have a significant association with RHD and its severity. Further studies are needed to determine the cause and effect relationship.

A Chemically Defined Medium-Based Strategy to Efficiently Generate Clinically Relevant Cord Blood Mesenchymal Stromal Colonies

During the last decade it has been demonstrated that mesenchymal progenitors are present and can be isolated also from cord blood (CB). Recently, we managed to set up a standard protocol allowing the isolation of mesenchymal stromal cells (MSCs) with high proliferative potential and multiple differentiation capabilities, whereas the generation rate of MSC-initiating colonies could still be further improved. Herein, we strikingly succeeded in defining some simple and basic culture conditions based on the use of a chemically defined medium that increased the colony isolation efficiency up to almost 80% of processed CB units. Importantly, this result was achieved irrespective of CB unit white blood cell content and time elapsed from delivery, two limiting parameters involved with processing CB units. Thus, this high efficiency is guaranteed without strict selection of the starting material. In addition, since we are profoundly concerned about how different culture conditions can influence cell behavior, we devoted part of this study to in-depth characterization of the established CB-MSC populations to confirm their stemness features in this novel isolation and culture system. Therefore, an extended study of their immunophenotype, including classical pericytic markers, and a detailed molecular analysis addressing telomere length and also stemness-related microRNA contribution were performed. In summary, we propose a straightforward, extremely efficient, and reliable approach to isolate and expand thoroughly characterized CB-MSCs, even when poor-quality CB units are the only available source, or there is no space for an isolation to fail.

Isolation, Culture, and Characterization of Human Umbilical Cord Blood-Derived Mesenchymal Stromal Cells

Umbilical cord blood (CB) is considered one of the youngest available sources of adult stem cells. Besides hematopoietic stem cells, CB has been shown to contain endothelial progenitor cells as well as mesenchymal stromal/stem cells (MSC). To isolate MSC from cord blood, CB is collected into a sterile bag containing the anticoagulant citrate-phosphate-dextrose (CPD). The CB is then processed by density-gradient centrifugation to obtain mononuclear cells (MNC). These are cultured until the outgrowth of fibroblastoid cell colonies appears. After reaching a subconfluent stage, cells are harvested, expanded, and characterized as cord blood mesenchymal stromal cells (CB-MSC) according to standard criteria: plastic adherence, fibroblast morphology, CFU-f assay, proliferation potential, immune phenotype, and differentiation potential.Apparently, the frequency of MSC in CB is extremely low. Thus, not every CB unit will provide adequate MSC isolation yields. Different strategies have been proposed aiming to optimize the isolation success by selecting CB units of optimal quality. It is commonly agreed on that a high CB volume, a high cellular content, and a short time frame between birth and MSC isolation are criteria that will enhance the MSC isolation success.The procedures in this chapter are standardized protocols that were established and optimized in the authors' research laboratory; however, various modifications of the protocols are possible.

Ex vivo identification and characterization of a population of CD13(high) CD105(+) CD45(-) mesenchymal stem cells in human bone marrow

Introduction

Mesenchymal stem cells (MSCs) are multipotent cells capable of self-renewal and multilineage differentiation. Their multipotential capacity and immunomodulatory properties have led to an increasing interest in their biological properties and therapeutic applications. Currently, the definition of MSCs relies on a combination of phenotypic, morphological and functional characteristics which are typically evaluated upon in vitro expansion, a process that may ultimately lead to modulation of the immunophenotypic, functional and/or genetic features of these cells. Therefore, at present there is great interest in providing markers and phenotypes for direct in vivo and ex vivo identification and isolation of MSCs.

Methods

Multiparameter flow cytometry immunophenotypic studies were performed on 65 bone marrow (BM) samples for characterization of CD13^high CD105⁺ CD45^– cells. Isolation and expansion of these cells was performed in a subset of samples in parallel to the expansion of MSCs from mononuclear cells following currently established procedures. The protein expression profile of these cells was further assessed on (paired) primary and in vitro expanded BM MSCs, and their adipogenic, chondrogenic and osteogenic differentiation potential was also determined.

Results

Our results show that the CD13^high CD105⁺ CD45⁻ immunophenotype defines a minor subset of cells that are systematically present ex vivo in normal/reactive BM (n = 65) and that display immunophenotypic features, plastic adherence ability, and osteogenic, adipogenic and chondrogenic differentiation capacities fully compatible with those of MSCs. In addition, we also show that in vitro expansion of these cells modulates their immunophenotypic characteristics, including changes in the expression of markers currently used for the definition of MSCs, such as CD105, CD146 and HLA-DR.

Conclusions

BM MSCs can be identified ex vivo in normal/reactive BM, based on a robust CD13^high CD105⁺ and CD45⁻ immunophenotypic profile. Furthermore, in vitro expansion of these cells is associated with significant changes in the immunophenotypic profile of MSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0152-8) contains supplementary material, which is available to authorized users.

CD271 as a marker to identify mesenchymal stem cells from diverse sources before culture

Mesenchymal stem cells, due to their characteristics are ideal candidates for cellular therapy. Currently, in culture these cells are defined by their adherence to plastic, specific surface antigen expression and multipotent differentiation potential. However, the in vivo identification of mesenchymal stem cells, before culture, is not so well established. Pre-culture identification markers would ensure higher purity than that obtained with selection based on adherence to plastic. Up until now, CD271 has been described as the most specific marker for the characterization and purification of human bone marrow mesenchymal stem cells. This marker has been shown to be specifically expressed by these cells. Thus, CD271 has been proposed as a versatile marker to selectively isolated and expand multipotent mesenchymal stem cells with both immunosuppressive and lymphohematopoietic engraftment-promoting properties. This review focuses on this marker, specifically on identification of mesenchymal stem cells from different tissues. Literature revision suggests that CD271 should not be defined as a universal marker to identify mesenchymal stem cells before culture from different sources. In the case of bone marrow or adipose tissue, CD271 could be considered a quite suitable marker; however this marker seems to be inadequate for the isolation of mesenchymal stem cells from other tissues such as umbilical cord blood or wharton’s jelly among others.

Umbilical Cord Blood-Derived Mononuclear Cells Exhibit Pericyte-Like Phenotype and Support Network Formation of Endothelial Progenitor Cells In Vitro

Umbilical cord blood represents a promising cell source for pro-angiogenic therapies. The present study examined the potential of mononuclear cells (MNCs) from umbilical cord blood to support endothelial progenitor cell (EPC) microvessel formation. MNCs were isolated from the cord blood of 20 separate donors and selected for further characterization based upon their proliferation potential and morphological resemblance to human vascular pericytes (HVPs). MNCs were screened for their ability to support EPC network formation using an in vitro assay (Matrigel™) as well as a reductionist, coculture system consisting of no additional angiogenic cytokines beyond those present in serum. In less than 15% of the isolations, we identified a population of highly proliferative MNCs that phenotypically resembled HVPs as assessed by expression of PDGFR-β, NG2, α-SMA, and ephrin-B2. Within a Matrigel™ system, MNCs demonstrated pericyte-like function through colocalization to EPC networks and similar effects as HVPs upon total EPC tubule length (p = 0.95) and number of branch points (p = 0.93). In a reductionist coculture system, MNCs served as pro-angiogenic mural cells by supporting EPC network formation to a significantly greater extent than HVP cocultures, by day 14 of coculture, as evidenced through EPC total tubule length (p < 0.0001) and number of branch points (p < 0.0001). Our findings are significant as we demonstrate mural cell progenitors can be isolated from umbilical cord blood and develop culture conditions to support their use in microvascular tissue engineering applications.

The assessment of CD146-based cell sorting and telomere length analysis for establishing the identity of mesenchymal stem cells in human umbilical cord

Adult stem cells are characterised by longer telomeres compared to mature cells from the same tissue. In this study, candidate CD146 (+) umbilical cord (UC) mesenchymal stem cells (MSCs) were purified by cell sorting from UC tissue digests and their telomere lengths were measured in comparison to donor-matched CD146-negative fraction. UC tissue fragments were enzymatically treated with collagenase and the cells were used for cell sorting, colony-forming fibroblast (CFU-F) assay or for long-term MSC cultivation. Telomere lengths were measured by qPCR in both culture-expanded MSCs and candidate native UC MSCs. Immunohistochemistry was undertaken to study the topography of CD146 (+) cells. Culture-expanded UC MSCs had a stable expression of CD73, CD90 and CD105, whereas CD146 declined in later passages which correlated with the shortening of telomeres in the same cultures. In five out of seven donors, telomeres in candidate native UC MSCs (CD45 (-)CD235α (-)CD31 (-)CD146 (+)) were longer compared to donor-matched CD146 (-) population (CD45 (-)CD235α (-)CD31 (-)CD146 (-)). The frequency of CD45 (-)CD235α (-)CD31 (-)CD146 (+) cells measured by flow cytometry was ~1000-fold above that of CFU-Fs (means 10.4% and 0.01%, respectively). CD146 (+) cells were also abundant in situ having a broad topography including high levels of positivity in muscle areas in addition to vessels. Although qPCR-based telomere length analysis in sorted populations could be limited in its sensitivity, very high frequency of CD146 (+) cells in UC tissue suggests that CD146 expression alone is unlikely to be sufficient to identify and purify native MSCs from the UC tissue.

The assessment of CD146-based cell sorting and telomere length analysis for establishing the identity of mesenchymal stem cells in human umbilical cord

Adult stem cells are characterised by longer telomeres compared to mature cells from the same tissue. In this study, candidate CD146 ⁺ umbilical cord (UC) mesenchymal stem cells (MSCs) were purified by cell sorting from UC tissue digests and their telomere lengths were measured in comparison to donor-matched CD146-negative fraction.

UC tissue fragments were enzymatically treated with collagenase and the cells were used for cell sorting, colony-forming fibroblast (CFU-F) assay or for long-term MSC cultivation. Telomere lengths were measured by qPCR in both culture-expanded MSCs and candidate native UC MSCs. Immunohistochemistry was undertaken to study the topography of CD146 ⁺ cells.

Culture-expanded UC MSCs had a stable expression of CD73, CD90 and CD105, whereas CD146 declined in later passages which correlated with the shortening of telomeres in the same cultures. In five out of seven donors, telomeres in candidate native UC MSCs (CD45 ^-CD235α ^-CD31 ^-CD146 ⁺) were longer compared to donor-matched CD146 ^- population (CD45 ^-CD235α ^-CD31 ^-CD146 ^-). The frequency of CD45 ^-CD235α ^-CD31 ^-CD146 ⁺ cells measured by flow cytometry was ~1000-fold above that of CFU-Fs (means 10.4% and 0.01%, respectively). CD146 ⁺ cells were also abundant in situ having a broad topography including high levels of positivity in muscle areas in addition to vessels.

Although qPCR-based telomere length analysis in sorted populations could be limited in its sensitivity, very high frequency of CD146 ⁺ cells in UC tissue suggests that CD146 expression alone is unlikely to be sufficient to identify and purify native MSCs from the UC tissue.

Dental pulp polyps contain stem cells comparable to the normal dental pulps

Objectives: Few studies investigated the isolation of stem cells from pathologically injured dental tissues. The aim of this study was to assess the possibility of isolation of stem cells from pulp polyps (chronic hyperplastic pulpitis), a pathological tissue produced in an inflammatory proliferative response within a tooth. Study design: Pulp polyp tissues were enzymatically digested and the harvested single cells were cultured. Cultured cells underwent differentiation to adipocytes and osteoblasts as well as flowcytometric analysis for markers such as: CD90, CD73, CD105, CD45, and CD14. In addition we tried to compare other characteristics (including colonigenic efficacy, population doubling time and the cell surface antigen panels) of these cells to that of healthy dental pulp stem cells (DPSCs). Results: Cells isolated from pulp polyps displayed spindle shape morphology and differentiated into adipocytes and osteoblasts successfully. These cells expressed CD90, CD73, and CD105 while were negative for CD45, CD14. Number of colonies among 104 tissue cells was higher in the normal pulp tissue derived cells than the pulp polyps (P=0.016); but as polyp tissues are larger and contain more cells (P=0.004), the total number of the stem cell in a sample tissue was higher in polyps but not significantly (P=0.073). Conclusions: The cells isolated from pulp polyps fulfill minimal criteria needed for MSC definition; hence, it can be concluded that pulp polyps contain stem cells. Although pulp polyps are rare tissues in daily practice but when they are present, may serve as a possible new non-invasively acquired tissue resource of stem cells for affected patients. List of abbreviations: APC = allophycocyanin, BM = Bone Marrow, CFU-F = Colony Forming Unit Fibroblast, DPSC = Dental Pulp Stem Cell, FITC = fluorescein isothiocyanate, MNC = mononuclear cells, MSC = Multipotent Mesenchymal Stromal Cell, PE = Phycoerythrin, PerCP = Peridinin chlorophyll protein, PPSC = Pulp Polyp Stem Cell.

Key words:Adult stem cell, chronic hyperplastic pulpitis, dental pulp stem cell, pulp polyp.