Characterization of Different Sources of Human MSCs Expanded in Serum-Free Conditions with Quantification of Chondrogenic Induction in 3D.

Mesenchymal stem cells (MSCs) represent alternative candidates to chondrocytes for cartilage engineering. However, it remains difficult to identify the ideal source of MSCs for cartilage repair since conditions supporting chondrogenic induction are diverse among published works. In this study, we characterized and evaluated the chondrogenic potential of MSCs from bone marrow (BM), Wharton's jelly (WJ), dental pulp (DP), and adipose tissue (AT) isolated and cultivated under serum-free conditions. BM-, WJ-, DP-, and AT-MSCs did not differ in terms of viability, clonogenicity, and proliferation. By an extensive polychromatic flow cytometry analysis, we found notable differences in markers of the osteochondrogenic lineage between the 4 MSC sources. We then evaluated their chondrogenic potential in a micromass culture model, and only BM-MSCs showed chondrogenic conversion. This chondrogenic differentiation was specifically ascertained by the production of procollagen IIB, the only type II collagen isoform synthesized by well-differentiated chondrocytes. As a pilot study toward cartilage engineering, we encapsulated BM-MSCs in hydrogel and developed an original method to evaluate their chondrogenic conversion by flow cytometry analysis, after release of the cells from the hydrogel. This allowed the simultaneous quantification of procollagen IIB and α10, a subunit of a type II collagen receptor crucial for proper cartilage development. This work represents the first comparison of detailed immunophenotypic analysis and chondrogenic differentiation potential of human BM-, WJ-, DP-, and AT-MSCs performed under the same serum-free conditions, from their isolation to their induction. Our study, achieved in conditions compliant with clinical applications, highlights that BM-MSCs are good candidates for cartilage engineering.

Development of new 3D human ex vivo models to study sebaceous gland lipid metabolism and modulations.

OBJECTIVES: Sebaceous glands maintain skin homeostasis by producing sebum. Low production can induce hair loss and fragile skin. Overproduction provokes seborrhoea and may lead to acne and inflammatory events. To better study sebaceous gland maintenance, sebocyte maturation, lipid production and ageing or inflammatory processes, we developed innovative 3D ex vivo models for human sebaceous glands. MATERIALS AND METHODS: Culture conditions and analytical methods optimized on sebocyte monolayers were validated on extracted sebaceous glands and allowed the development of two 3D models: (a) "air-liquid" interface and (b) human fibronectin-coated "sandwich" method. Lipid production was assessed with microscopy, fluorometry or flow cytometry analysis after Nile Red staining. Specific lipids (particularly squalene and peroxidized squalene) were measured by Gas or liquid Chromatography and Mass spectrometry. RESULTS: This study allowed us to select appropriate conditions and design Seb4Gln culture medium inducing sebocyte proliferation and neutral lipid production. The "air-liquid" model was appropriate to induce sebocyte isolation. The "sandwich" model enabled sebaceous gland maintenance up to 42 days. A treatment with Insulin Growth Factor-1 allowed validation of the model as we succeeded in mimicking dynamic lipid overproduction. CONCLUSION: Functional sebocyte maturation and physiological maintenance were preserved up to 6 weeks in our models. Associated with functional assays, they provide a powerful platform to mimic physiological skin lipid metabolism and to screen for active ingredients modulating sebum production.

Immunophenotyping Reveals the Diversity of Human Dental Pulp Mesenchymal Stromal Cells In vivo and Their Evolution upon In vitro Amplification.

Mesenchymal stromal/stem cells (MSCs) from human dental pulp (DP) can be expanded in vitro for cell-based and regenerative dentistry therapeutic purposes. However, their heterogeneity may be a hurdle to the achievement of reproducible and predictable therapeutic outcomes. To get a better knowledge about this heterogeneity, we designed a flow cytometric strategy to analyze the phenotype of DP cells in vivo and upon in vitro expansion with stem cell markers. We focused on the CD31- cell population to exclude endothelial and leukocytic cells. Results showed that the in vivo CD31- DP cell population contained 1.4% of CD56+, 1.5% of CD146+, 2.4% of CD271+ and 6.3% of MSCA-1+ cells but very few Stro-1+ cells (≤ 1%). CD56+, CD146+, CD271+, and MSCA-1+ cell subpopulations expressed various levels of these markers. CD146+MSCA-1+, CD271+MSCA-1+, and CD146+CD271+ cells were the most abundant DP-MSC populations. Analysis of DP-MSCs expanded in vitro with a medicinal manufacturing approach showed that CD146 was expressed by about 50% of CD56+, CD271+, MSCA-1+, and Stro-1+ cells, and MSCA-1 by 15-30% of CD56+, CD146+, CD271+, and Stro-1+ cells. These ratios remained stable with passages. CD271 and Stro-1 were expressed by <1% of the expanded cell populations. Interestingly, the percentage of CD56+ cells strongly increased from P1 (25%) to P4 (80%) both in all sub-populations studied. CD146+CD56+, MSCA-1+CD56+, and CD146+MSCA-1+ cells were the most abundant DP-MSCs at the end of P4. These results established that DP-MSCs constitute a heterogeneous mixture of cells in pulp tissue in vivo and in culture, and that their phenotype is modified upon in vitro expansion. Further studies are needed to determine whether co-expression of specific MSC markers confers DP cells specific properties that could be used for the regeneration of human tissues, including the dental pulp, with standardized cell-based medicinal products.

Manufacturing of dental pulp cell-based products from human third molars: current strategies and future investigations.

In recent years, mesenchymal cell-based products have been developed to improve surgical therapies aimed at repairing human tissues. In this context, the tooth has recently emerged as a valuable source of stem/progenitor cells for regenerating orofacial tissues, with easy access to pulp tissue and high differentiation potential of dental pulp mesenchymal cells. International guidelines now recommend the use of standardized procedures for cell isolation, storage and expansion in culture to ensure optimal reproducibility, efficacy and safety when cells are used for clinical application. However, most dental pulp cell-based medicinal products manufacturing procedures may not be fully satisfactory since they could alter the cells biological properties and the quality of derived products. Cell isolation, enrichment and cryopreservation procedures combined to long-term expansion in culture media containing xeno- and allogeneic components are known to affect cell phenotype, viability, proliferation and differentiation capacities. This article focuses on current manufacturing strategies of dental pulp cell-based medicinal products and proposes a new protocol to improve efficiency, reproducibility and safety of these strategies.

Production of Human Dental Pulp Cells with a Medicinal Manufacturing Approach.

INTRODUCTION: Human dental pulp cells (HDPCs) are generally isolated and cultured with xenogeneic products and in stress conditions that may alter their biological features. However, guidelines from the American Food and Drug Administration and the European Medicines Agency currently recommend the use of protocols compliant with medicinal manufacturing. Our aim was to design an ex vivo procedure to produce large amounts of HDPCs for dentin/pulp and bone engineering according to these international recommendations. METHODS: HDPC isolation was performed from pulp explant cultures. After appropriate serum-free medium selection, cultured HDPCs were immunophenotyped with flow cytometry. Samples were then cryopreserved for 510 days. The post-thaw cell doubling time was determined up to passage 4 (P4). Karyotyping was performed by G-band analysis. Osteo/odontoblastic differentiation capability was determined after culture in a differentiation medium by gene expression analysis of osteo/odontoblast markers and mineralization quantification. RESULTS: Immunophenotyping of cultured HDPCs revealed a mesenchymal profile of the cells, some of which also expressed the stem/progenitor cell markers CD271, Stro-1, CD146, or MSCA-1. The post-thaw cell doubling times were stable and similar to fresh HDPCs. Cells displayed no karyotype abnormality. Alkaline phosphatase, osteocalcin, and dentin sialophosphoprotein gene expression and culture mineralization were increased in post-thaw HDPC cultures performed in differentiation medium compared with cultures in control medium. CONCLUSIONS: We successfully isolated, cryopreserved, and amplified human dental pulp cells with a medicinal manufacturing approach. These findings may constitute a basis on which to investigate how HDPC production can be optimized for human pulp/dentin and bone tissue engineering.

Osteoblastic differentiation of Wharton jelly biopsy specimens and their mesenchymal stromal cells after serum-free culture.

BACKGROUND: Cleft lip and cleft palate are increasingly being detected by prenatal ultrasound, which raises the opportunity of using the patient's own osteogenicity from umbilical cord mesenchymal cells for bony repair. The authors address the growth of the cells under a fully defined and regulated protocol. METHODS: Wharton jelly-derived mesenchymal stromal cells were isolated and expanded as a monolayer with defined serum-free medium. Osteoblastic differentiation was tested in the cells and in the entire Wharton jelly biopsy specimens. The serum-free-cultured cells were included in hydroxyapatite granule-fibrin constructs and, without predifferentiation, subcutaneously implanted into immunoincompetent mice. RESULTS: Isolation and expansion of Wharton jelly-derived mesenchymal stromal cells were consistently successful under serum-free conditions, and the cells expressed standard mesenchymal stromal cell markers. The serum-free-cultivated cells produced a mineralized extracellular matrix under osteogenic differentiation, with a significant increase of osteoblastic lineage gene expression (Hox-A10 and Runx2) and an up-regulation of downstream osteogenic genes (OSX, OCN, ALPL, and BSP2). In vivo, they formed a dense matrix adjacent to the granules after 8 weeks, but no lamellar bone. serum-free-cultivated entire Wharton jelly biopsy specimens produced a mineralized extracellular matrix within the collagen matrix of the Wharton jelly. CONCLUSIONS: The osteogenic differentiation potential of Wharton jelly-derived mesenchymal stromal cells was maintained under serum-free isolation and expansion techniques. The cells without predifferentiation form a dense collagen matrix but not bone in vivo. Moreover, entire Wharton jelly biopsy specimens showed periosteal-like mineralization under osteogenic differentiation, which offers new options for autologous bone tissue engineering, including cleft palate surgery.

Ischemic brain injury: a consortium analysis of key factors involved in mesenchymal stem cell-mediated inflammatory reduction.

Increasing global birth rate, coupled with the aging population surviving into their eighth decade has lead to increased incidence diseases, hitherto designated as rare. Brain related ischemia, at birth, or later in life, during, for example stroke, is increasing in global prevalence. Reactive microglia can contribute to neuronal damage as well as compromising transplantion. One potential treatment strategy is cellular therapy, using mesenchymal stem cells (hMSCs), which possess immunomodulatory and cell repair properties. For effective clinical therapy, mechanisms of action must be understood better. Here multicentre international laboratories assessed this question together investigating application of hMSCs neural involvement, with interest in the role of reactive microglia. Modulation by hMSCs in our in vivo and in vitro study shows they decrease markers of microglial activation (lower ED1 and Iba) and astrogliosis (lower GFAP) following transplantation in an ouabain-induced brain ischemia rat model and in organotypic hippocampal cultures. The anti-inflammatory effect in vitro was demonstrated to be CD200 ligand dependent with ligand expression shown to be increased by IL-4 stimulation. hMSC transplant reduced rat microglial STAT3 gene expression and reduced activation of Y705 phosphorylated STAT3, but STAT3 in the hMSCs themselves was elevated upon grafting. Surprisingly, activity was dependent on heterodimerisation with STAT1 activated by IL-4 and Oncostatin M. Our study paves the way to preclinical stages of a clinical trial with hMSC, and suggests a non-canonical JAK-STAT signaling of unphosphorylated STAT3 in immunomodulatory effects of hMSCs.