Ennio Becchetti

Multipotent mesenchymal stem cells with immunosuppressive activity can be easily isolated from dental pulp.

Background. Bone marrow mesenchymal stem cells (MSCs) are currently being investigated in preclinical and clinical settings because of their multipotent differentiative capacity or, alternatively, their immunosuppressive function. The aim of this study was to evaluate dental pulp (DP) as a potential source of MSCs instead of bone marrow (BM). Methods. Flow cytometric analysis showed that DP-MSCs and BM-MSCs were equally SH2, SH3, SH4, CD29 and CD 166 positive. The in vitro proliferative kinetics of MSCs were measured by 3H-thymidine incorporation uptake. The immunosuppressive function of MSCs was then tested by coculturing PHA-stimulated allogeneic T cells with or without MSCs for 3 days. Results. BM-MSCs could be differentiated in vitro into osteogenic, chondrogenic and adipogenic lineages. DP-MSCs showed osteogenic and adipocytic differentiation, but did not differentiate into chondrocytes. Although DP-MSCs grow rapidly in vitro between day 3 and day 8 of culture and then decrease their proliferation by day 15, BM-MSCs have a stable and continuous proliferation over the same period of time. The addition of DP-MSCs or BM-MSCs resulted in 91 ± 4% and 75 ± 3% inhibition of T cell response, respectively, assessed by a 3H-thymidine assay. Conclusions. Dental pulp is an easily accessible and efficient source of MSCs, with different kinetics and differentiation potentialities from MSCs as isolated from the bone marrow. The rapid proliferative capacity together with the immunoregulatory characteristics of DP-MSCs may prompt future studies aimed at using these cells in the treatment or prevention of T-cell alloreactivity in hematopoietic or solid organ allogeneic transplantation.

Therapy of experimental type 1 diabetes by isolated Sertoli cell xenografts alone

Type I diabetes mellitus is caused by autoimmune destruction of pancreatic β cells, and effective treatment of the disease might require rescuing β cell function in a context of reinstalled immune tolerance. Sertoli cells (SCs) are found in the testes, where their main task is to provide local immunological protection and nourishment to developing germ cells. SCs engraft, self-protect, and coprotect allogeneic and xenogeneic grafts from immune destruction in different experimental settings. SCs have also been successfully implanted into the central nervous system to create a regulatory environment to the surrounding tissue which is trophic and counter-inflammatory. We report that isolated neonatal porcine SC, administered alone in highly biocompatible microcapsules, led to diabetes prevention and reversion in the respective 88 and 81% of overtly diabetic (nonobese diabetic [NOD]) mice, with no need for additional β cell or insulin therapy. The effect was associated with restoration of systemic immune tolerance and detection of functional pancreatic islets that consisted of glucose-responsive and insulin-secreting cells. Curative effects by SC were strictly dependent on efficient tryptophan metabolism in the xenografts, leading to TGF-β–dependent emergence of autoantigen-specific regulatory T cells and recovery of β cell function in the diabetic recipients.

Transforming growth factor ß1 acid interaction

Chick embryo skin fibroblasts release transforming growth factor β1 that is able to modulate glycosaminoglycan synthesis and secretion. When incubated with individual classes of glycosaminoglycans, the factors modulatory activity was altered. To determine whether direct interactions between transforming growth factor β1 and glycosaminoglycans occur, we have assessed the activity of the growth factor after pre-incubation with single classes of glycosaminoglycans by assaying its inhibitory effect upon the proliferative response of thymocytes stimulated with interleukin-1. Untreated transforming growth factor β1 suppressed the proliferative response of thymocytes to interleukin-1, as did transforming growth factor β1 pre-incubated with sulphated glycosaminoglycans. By contrast, transforming growth factor β1 lost its inhibitory capacity when preincubated with high molecular weight hyaluronic acid. Digestion of transforming growth factor β1-hyaluronic acid complex with hyaluronidase released active transforming growth factor β1. Trypsin degraded transforming growth factor β1 alone, but did not degrade the transforming growth factor β1-hyaluronic acid complex. These results suggest that hyaluronic acid interacts with transforming growth factor β1, thus protecting the factor from tryptic degradation and may be a means of concentrating growth factor activity.

Biocompatibility of alloys used in orthodontics evaluated by cell culture tests.

The cytotoxicity of the most common alloys used in orthodontic appliances was determined by cell culture testing. Human gingival fibroblasts were cultured on 304 and 316 stainless steel, on brazing alloy composed of palladium (Pd), copper (Cu), and silver (Ag), and on plastic substrate (control). Studies were carried out with SEM and radiolabeled precursor incorporation. Cells were cultured in MEM without serum but with the addition of (3)H-thymidine to evaluate cell proliferation and (3)H-glucosamine to evaluate glycosaminoglycan (GAG) synthesis and secretion in the culture medium. Moreover, gingival fibroblasts were cultured in the presence of some metal ions generally released by orthodontic appliances to evaluate the cytotoxic effects of single ions. Morphologic observations with SEM and radiolabeled incorporation studies showed that 304 and 316 stainless steel were more biocompatible than the brazing alloy. Among the metal ions tested, Ag and Pd, constituents of the brazing alloy, showed the highest cytotoxicity.

Apert's syndrome: differential in vitro production of matrix macromolecules and its regulation by interleukins

During embryonic development, variations in the composition of the extracellular matrix (ECM) macromolecules influence bone tissue differentiation. We present novel findings on the in vitro phenotypic expression of periosteal fibroblasts obtained from patients affected by Apert’s syndrome, a rare craniofacial malformation, and the effects that interleukins (ILs) induce on the phenotype. Apert fibroblasts synthesized greater quantities of glycosaminoglycans (GAGs) and intracellular type I collagen, and also produced more type III collagen and fibronectin. The amount of hyaluronic acid (HA) secreted by Apert fibroblasts was much higher than that secreted by normal fibroblasts, but, as the absolute values of heparan sulphate (HS), chondroitin sulphate (CS) and dermatan sulphate (DS) also rose in Apert media, the HA–sulphated GAG ratio was similar in the media obtained from both populations. Both ILs triggered elevations of HA in normal cells, although relative percentage secretion remained unaltered, but significantly reduced HA secretion by Apert cells. IL‐1 significantly increased CS in normal and Apert media, whereas IL‐6 enhanced HS and DS in media of both populations. HA–sulphated GAG ratio decreased in Apert media after IL treatment. Both ILs boosted fibronectin production by Apert fibroblasts, whereas IL‐1 increased type III but not type I collagen. Taken together, these data demonstrate that the synthesis and secretion of ECM macromolecules are markedly altered in Apert fibroblasts. The fact that treatment with ILs further modifies the Apert phenotype suggests that ILs may be implicated in the pathophysiology of the malformations during skull morphogenesis.

Cellular Support Systems for Alginate Microcapsules Containing Islets, as Composite Bioartificial Pancreas

Abstract: To improve the functional performance of microencapsulated islets, we examined the effects of putative cellular support systems, consisting of rat purified Sertoli cells (SC) and astrocytes (AA), on coenveloped allogeneic islets. Coincubation of islets with SC but not AA, resulted in significant stimulation of β cell mitogenesis, coupled with a significant increase in in vitro glucose‐stimulated insulin release. Preliminarily, the xenotransplantation of coencapsulated rat islets and homologous SC significantly prolonged remission of hyperglycemia in diabetic mice.

Glycosaminoglycan Metabolism and Cytokine Release in Normal and Otosclerotic Human Bone Cells Interleukin-1 Treated

Glycosaminoglycans (GAGs), normal components of the extracellular matrix (ECM), and the glycosidases, that degrade them, play a key role in the bone remodelling process. The effects of interleukin-1 alpha (IL-1 alpha) on GAG metabolism in normal and otosclerotic human bone cells as well as its capacity to modulate IL-1 alpha, IL-1 beta and IL-6 secretion in both populations was analyzed. The amount of radiolabeled GAGs was lower in otosclerotic than in normal bone cells. IL-1 alpha reduced newly synthesized cellular and extracellular GAGs in normal cells, but only those of the cellular compartment in otosclerotic bone cells. It depressed heparan sulphate (HS) more in normal cells and chondroitin sulphate (CS) more in otosclerotic bone cells. The HA/total sulphated GAG ratio was shifted in favour of the latter in otosclerotic cells, whereas the opposite effect was seen after IL-1 alpha treatment. There was little difference in the beta-D-glucuronidase levels of the normal and pathological cells, while beta-N-acetyl-D-glucosaminidase was significantly increased in otosclerotic bone cells. As the activity of neither enzyme was modified by treatment with IL-1 alpha, the cytokine seems to exert its influences on GAG synthesis rather than on the degradation process. IL-1 alpha, IL-1 beta and IL-6 secretion was markedly higher in otosclerotic cells. IL-1 alpha modulated the secretion of each interleukin differently, thus resulting in a cytokine cascade that may act in autocrine/paracrine manner on target cells. The authors suggest that changes in the cytokine network may have a specific, yet still unknown, role during normal and pathological osteogenesis.

Effects of hydroxyapatite and biostite® on osteogenic induction of hMSC

When isolated from the iliac crest human mesenchymal stem cells (hMSC) differentiate into osteoblast-like cells with appropriate stimulation in culture. This in vitro study tested the hypothesis that Biostite® and hydroxyapatite (HA) affect proliferation and differentiation of hMSC into osteoblastic cells. Cell proliferation was determined by measuring 3H-thymidine incorporation into DNA and typical markers of osteoblastic phenotype were determined by RT-PCR assay. No differences emerged in cell proliferation cultures with Biostite® or hydroxyapatite (HA), but gene expression analysis revealed higher expression of collagen, alkaline phosphatase (ALP), osteopontin and bone sialoprotein (BSP) in the presence of Biostite®. TGFβ2 production, as assessed by an Elisa kit, and Runx2 expression by RT-PCR, were greater in Biostite cultures, suggesting Biostite® provides a better environment for hMSC differentiation into osteoblasts and is, potentially, a more promising bone-filling material than HA.

Improved function of rat islets upon co-microencapsulation with Sertoli's cells in alginate/poly-L-ornithine

The purpose of this study was to assess whether Sertolis cells would improve functional performance of homologous pancreatic islets within microcapsules. Purified rat Sertolis cells were co-enveloped with islets in microcapsules that had been fabricated with alginic acid and poly-L-ornithine Confocal laser microscopy was used to determine any mitogenic effects of Sertolis cells on islets ß-cells. Insulin secretion from islets, with or without Sertolis cells, was examined and grafts of Sertolis cells with islets in microcapsules into diabetic mice were carried out. Co-incubation of Sertolis cells with islets resulted in a significant increase in the islet ß-cell mitotic rate, which was coupled with significantly higher insulin release under glucose stimulation, as compared to controls. Grafts of co-microencapsulated Sertolis cells with islets resulted in prolongation of the achieved normoglycemia in the animals receiving Sertolis cells with islets as compared to controls that received islets only. Sertolis cells do promote mitogenic activities upon in vitro co-incubation with islets, whose in vitro functional and in vivo post-transplant consequences were evident. Sertolis cells could, therefore, be comicroencapsulated with islets for transplantation in diabetic recipients.

In vitro cytotoxic effects of orthodontic appliances

The objective of this study was to evaluate the effects of an orthodontic appliance and of its components (brackets, bands, and arch wires) on some cell functions. Fibroblasts were cultured either in the presence of one unwashed orthodontic appliance, or one orthodontic appliance immersed in MEM for 28 days before use (washed appliance), or in the presence of MEM in which the appliances had been immersed. At the end of in vitro maintenance, morphological studies were carried out with SEM and TEM. Cell proliferation and GAG synthesis and secretion by radio-labeled precursors were assessed. The data indicated that unwashed appliances were more cytotoxic than washed ones. Moreover, the arch wire was the most biocompatible component of the orthodontic appliance, and the bracket was the least biocompatible. A comparative study into the effects on cell proliferation of the most common metal ions released by the appliances was also carried out. At the concentration released by one orthodontic appliance immersed for 28 days, the highest reduction in DNA synthesis was observed in the presence of Cu(++).