We tested the hypothesis that multipotent stromal cells from human bone marrow (hMSCs) can provide a potential therapy for human diabetes mellitus. Severe but nonlethal hyperglycemia was produced in NOD͞scid mice with daily low doses of streptozotocin on days 1-4, and hMSCs were delivered via intracardiac infusion on days 10 and 17. The hMSCs lowered blood glucose levels in the diabetic mice on day 32 relative to untreated controls (18.34 mM ؎ 1.12 SE vs. 27.78 mM ؎ 2.45 SE, P ‫؍‬ 0.0019). ELISAs demonstrated that blood levels of mouse insulin were higher in the hMSC-treated as compared with untreated diabetic mice, but human insulin was not detected. PCR assays detected human Alu sequences in DNA in pancreas and kidney on day 17 or 32 but not in other tissues, except heart, into which the cells were infused. In the hMSC-treated diabetic mice, there was an increase in pancreatic islets and ␤ cells producing mouse insulin. Rare islets contained human cells that colabeled for human insulin or PDX-1. Most of the ␤ cells in the islets were mouse cells that expressed mouse insulin. In kidneys of hMSC-treated diabetic mice, human cells were found in the glomeruli. There was a decrease in mesangial thickening and a decrease in macrophage infiltration. A few of the human cells appeared to differentiate into glomerular endothelial cells. Therefore, the results raised the possibility that hMSCs may be useful in enhancing insulin secretion and perhaps improving the renal lesions that develop in patients with diabetes mellitus.insulin ͉ pancreas ͉ streptozotocin ͉ transplantation P revious publications presented conflicting observations as to whether cells from bone marrow can provide a potential therapy for diabetes mellitus. One strategy (1-4) was to differentiate plastic adherent marrow cells in culture into insulin-secreting cells. A second strategy was to transplant diabetic mice with genetically labeled marrow and to search for labeled insulinproducing cells in the recipient mice. One study using a CRELoxP-GFP system found that 1.7-3% of the cells in islets of the recipient mice were marrow-derived and that GFP-labeled donor cells isolated from the islets expressed insulin, glucose transporter 2, and transcription factors typically found in ␤ cells (5). Three subsequent reports in which mice were transplanted with GFPexpressing bone marrow did not find evidence of marrow cells becoming insulin-producing cells in the pancreas of recipient mice (6-8), but in the reports it was difficult to exclude the possibility that the GFP gene was inactivated or that GFP-labeled cells were destroyed as they engrafted into islets. A third strategy was to determine whether systemically administered marrow cells enhanced regeneration of pancreatic insulin-producing cells in diabetic models. Hess et al. (9) reported that in NOD͞scid mice in which diabetes was induced with streptozotocin (STZ), partial marrow ablation followed by transplantation of either GFP-labeled whole-marrow or GFP-labeled c-kit ϩ cells from murine marrowenhanced r...

Human mesenchymal stromal cells (hMSCs) were injected into the hippocampus of adult mice 1 day after transient global ischemia. The hMSCs both improved neurologic function and markedly decreased neuronal cell death of the hippocampus. Microarray assays indicated that ischemia up-regulated 586 mouse genes. The hMSCs persisted for <7 days, but they down-regulated >10% of the ischemia-induced genes, most of which were involved in inflammatory and immune responses. The hMSCs also upregulated three mouse genes, including the neuroprotective gene Ym1 that is expressed by activated microglia/macrophages. In addition, the transcriptomes of the hMSC changed with upregulation of 170 human genes and down-regulation of 54 human genes. Protein assays of the hippocampus demonstrated increased expression in microglia/macrophages of Ym1, the cell survival factor insulin-like growth factor 1, galectin-3, cytokines reflective of a type 2 T cell immune bias, and the major histocompatibility complex II. The observed beneficial effects of hMSCs were largely explained by their modulation of inflammatory and immune responses, apparently by alternative activation of microglia and/or macrophages.inflammation ͉ mesenchymal stromal cells ͉ microglia ͉ mesenchymal stem cells O bservations in rodent and primate models suggest that a potential therapy for ischemia of the central nervous system is the administration of the adult stem/progenitor cells from bone marrow referred to as mesenchymal stem cells or multipotent mesenchymal stromal cells (MSCs) (1-3). Administration of MSCs also produced beneficial effects in animal models for neurodegenerative diseases, such as Parkinson's disease, experimental autoimmune encephalomyelitis, and amyotrophic lateral sclerosis (2-5). MSCs initially attracted interest for their ability to differentiate into multiple cellular phenotypes in culture and in vivo (1-7). However, recent observations indicate that only small numbers of the cells engraft into most injured tissues, and they disappear quickly (2-5, 8-10). When human MSCs (hMSCs) were injected into the dentate gyrus (DG) of the hippocampus in adult immunodeficient (ID) mice, most of the cells disappeared within 1 week, but they enhanced proliferation, migration, and neural differentiation of the endogenous neural stem cells (8). These and related observations have focused attention on the paracrine effects of MSCs (2, 3, 11). However, it has not been established whether the beneficial effects of MSCs in ischemic models of brain injury are explained by enhanced neurogenesis (8) or by neuroprotection.Experiments here were performed in a mouse model of global ischemia to assess the neuroprotective effects of hMSCs. Administration of hMSCs 1 day after transient common carotid artery occlusion (tCCAO) improved neurologic function and decreased the delayed neuronal cell death of the hippocampus. Surveys with microarrays indicated that the hMSCs decreased expression of many of the mouse genes that were induced by ischemia and that were involved in inflamma...

In this review, we focus on the adult stem/progenitor cells that were initially isolated from bone marrow and first referred to as colony forming units-fibroblastic, then as marrow stromal cells and subsequently as either mesenchymal stem cells or multipotent mesenchymal stromal cells (MSCs). The current interest in MSCs and similar cells from other tissues is reflected in over 10,000 citations in PubMed at the time of this writing with 5 to 10 new publications per day. It is also reflected in over 100 registered clinical trials with MSCs or related cells (). As a guide to the vast literature, this review will attempt to summarize many of the publications in terms of three paradigms that have directed much of the work: an initial paradigm that the primary role of the cells was to form niches for haematopoietic stem cells (paradigm I); a second paradigm that the cells repaired tissues by engraftment and differentiation to replace injured cells (paradigm II); and the more recent paradigm that MSCs engage in cross-talk with injured tissues and thereby generate microenvironments or ‘quasi-niches’ that enhance the repair tissues (paradigm III).

The human adult stem cells from bone marrow stroma referred to as mesenchymal stem cells or marrow stromal cells (MSCs) are of interest because they are easily isolated and expanded and are capable of multipotential differentiation. Here, we examined the ability of recombinant human bone morphogenetic protein (BMP)-2, -4, and -6 to enhance in vitro cartilage formation of MSCs. Human MSCs were isolated from bone marrow taken from normal adult donors. The cells were pelleted and cultured for 21 days in chondrogenic medium containing transforming growth factor beta3 and dexamethasone with or without BMP-2, -4, or -6. All the BMPs tested increased chondrogenic differentiation as assayed by immunohistochemistry and by the size and weight of the cartilage synthesized. However, BMP-2 was the most effective. Microarray analyses of approximately 12,000 genes and reverse transcription-polymerase chain reaction assays established that the critical genes for cartilage synthesis were expressed in the expected time sequence in response to BMP-2. The tissue engineering of autologous cartilage derived from MSCs in vitro for transplantation will be a future alternative for patients with cartilage injuries. To obtain large amounts of cartilage rich in proteoglycans, the use of BMP-2 is recommended, instead of BMP-4 or -6.

Objective Meniscal regeneration was previously shown to be enhanced by injection of mesenchymal stem/stromal cells (MSCs) but the mode of action of the MSCs was not established. The aim of this study was to define how injection of MSCs enhances meniscal regeneration. Design A hemi-meniscectomy model in rats was used. Rat-MSCs (rMSCs) or human-MSCs (hMSCs) were injected into the right knee joint after the surgery, and PBS was injected into the left. The groups were compared macroscopically and histologically at 2, 4, and 8 w. The changes in transcription in both human and rat genes were assayed by species-specific microarrays and real-time RT-PCRs. Results Although the number of hMSCs decreased with time, hMSCs enhanced meniscal regeneration in a manner similar to rMSCs. hMSCs injection increased expression of rat type II collagen (rat-Col II), and inhibited osteoarthritis progression. The small fraction of hMSCs were activated to express high levels of a series of genes including Indian hedgehog (Ihh), parathyroid hormone-like hormone (PTHLH), and bone morphogenetic protein 2 (BMP2). The presence of hMSCs triggered the subsequent expression of rat-Col II. An antagonist of hedgehog signaling inhibited the expression of rat-Col II and an agonist increased expression of rat-Col II in the absence of hMSCs. Conclusions Despite rapid reduction in cell numbers, intra-articular injected hMSCs were activated to express Ihh, PTHLH, and BMP2 and contributed to meniscal regeneration. The hedgehog signaling was essential in enhancing the expression of rat-Col II, but several other factors provided by the hMSCs probably contributed to the repair.