Influence of stem cell mobilization and liver regeneration on hepatic parenchymal chimerism in the rat

BACKGROUND: Despite the newly discovered plasticity of hematopoietic stem cells, their capacity to "transdifferentiate" into parenchymal cells and the regulation of this process is not yet elucidated. The present study was designed to investigate the effect of stem cell mobilization and liver regeneration on this process using a syngeneic rat female-to-male liver transplantation model. METHODS: Rate and frequency of Y-chromosome containing hepatocytes was determined by fluorescence-in situ hybridization (FISH) using a rat Y-chromosome specific probe. Rats were subjected to full-size or partial liver transplantation with and without stem cell mobilization using granulocyte colony stimulating factor (G-CSF). The effect of stem cell mobilization was confirmed by assessing the white blood count and by evaluating the migration of granulopoietic precursor cells to the liver. RESULTS: Treatment with G-CSF induced a twofold increase of peripheral white blood cells and a strong influx of granulopoietic precursor cells into the liver. Transplantation of a partial liver graft was followed by a 90% recovery of the original liver weight within a week, demonstrating the strong regenerative stimulus. Irrespective of the experimental model, the incidence and rate of Y-chromosome containing hepatocytes never exceeded 0.77%. CONCLUSION: Neither stem cell mobilization nor liver regeneration enhanced the incidence or rate of stem cell derived hepatocytes in a liver graft with unimpaired regenerative potential.     

Stem cells used for cardiovascular tissue engineering

Stem cell research and tissue engineering have become leading fields in basic research worldwide. Especially in cardiovascular medicine, initial reports on the potential of using stem cells to recover cardiac function and replace organ subunits such as heart valves seemed to offer the promise of widespread clinical use in the near future. However, the broad application of this new therapy failed due to safety and efficacy concerns. Due in part to the initial reports, major basic research efforts were undertaken to explore the specific cell types in greater detail and identify their mechanisms of supporting function, resulting in remarkable new findings in stem cell biology. For example, the notion of resident human cardiac stem cells has disproved the earlier supposition that the human heart is a finitely differentiated organ without the intrinsic potential for regeneration. Furthermore, new technologies emerged to produce pluripotent cells without the ethical and immunological drawbacks of embryonic stem cells (for instance by nuclear transfer). Other autologous cell sources are presently under investigation in myocardial tissue engineering. For tissue engineering of heart valves and small calibre vessels, the use of autologous endothelial (precursor) cells may be the optimal means of seeding a biological or artificial scaffold. It is important that ongoing basic and clinical research in cardiovascular surgery might explore the potential of different cell types either using tissue engineering constructs or in cell transplantation approaches.     

The adult "paraplegic" rat: treatment with cell graftings

Spinal cord injury often results in irreversible and permanent neurologic deficits below the lesion level. Nowadays, treatment is limited to drugs and/or physiotherapy aimed at compensating disability. New experimental studies focus on the transplantation of cells capable of surviving, regenerating tissue, recovering functions and/or improving symptoms. A review of such type of studies on spinal cord reconstruction published between 1991 and 2004 is presented. In the latter years, cell transplantation appeared as the most promising approach in spinal cord regeneration research. To date, this promise has not been maintained, despite the appearance of new attractive cell populations for grafting, such as neural stem cells. The demonstration that stem cells exist in the adult brain and that they can be isolated and expanded in vitro offers the possibility to test such interesting cells in the paraplegic rat. Some neurotrophic factors can facilitate axonal regeneration and neuronal survival. Therefore, the development of strategies, such as implanting neural stem cells engineered to secrete neurotrophic factors directly in the lesion site, could be important to promote regeneration in the injured spinal cord. Despite all the strategies used till now, the problem of the paraplegic rat remains. Only the solution of such problem will authorize studies in higher mammals and, finally, the clinical application in human patients. The paraplegic adult rat with a T8 spinal cord transection should be considered the standard experimental model to be used in spinal cord reconstruction studies. Function and anatomic results are undisputed only after spinal cord transection.     

Stem cells in regenerative biology and medicine

Embryonic stem cells of the mammalian blastocyst give rise to all the tissue lineages that begin to emerge at gastrulation. They are pluripotent cells and can be propagated in vitro without loss of pluripotency. Many adult tissues harbor cells that do not complete their differentiation program. These cells serve as self-renewing stem cells whose normal fate is to regenerate site-specific tissue, in response to either physiological cell turnover or damage inflicted by injury or disease. Neural, muscle, and bone marrow stem cells possess developmental potency far greater than their normal lineage-restricted fate. The understanding of the biology of stem cells is leading us into an era of regenerative medicine. The growth potential and pluripotency of embryonic stem cells and the developmental plasticity of adult stem cells, particularly those of bone marrow, make them potentially useful for replacing tissues, via transplantation or construction of bioartificial tissues, that either do not regenerate naturally or are damaged beyond their natural capability for regeneration. In addition to these two ways of replacing tissue, a third strategy of regenerative medicine is to stimulate regeneration in vivo from resident stem cells. Before these approaches become clinical reality, however, a number of basic research issues must be resolved, including the revision of our concept of a regeneration-competent cell.     

Stem cell transplantation as a therapeutic strategy for traumatic brain injury

Stem cell transplantation has enormous potential to be a viable therapeutic approach to replace the lost tissue/cells following traumatic brain injury (TBI). Several types of cell lines such as immortalized progenitors cells, embryonic rodent and human stem cells and bone marrow-derived cells have been successfully transplanted in experimental models of TBI, resulting in reduced neurobehavioral deficits and attenuation of histological damage. To date, it remains unclear whether stem cell are effective following transplantation into the injured brain via either cell replacement, trophic support, or manipulation of the local environment to stimulate endogenous neuroprotection/regeneration. This paper will review the most current and exciting pre-clinical data regarding the utility of cellular transplantation in experimental models of TBI. We believe that further work must continue to better understand the interaction between the host and the transplanted cells as well as the mechanisms regulating their differentiation into mature and functionally active neurons/glia.     

人脐带间充质干细胞用于衰老相关疾病治疗的研究进展

随着干细胞移植技术的发展,通过输入干细胞进行抗衰老治疗或治疗退行性疾病成为人们研究的热点。人脐带间充质干细胞(human umbilical cord mesenchymal stem cells,HUCMSCs)是一种存在于脐带沃顿胶以及血管周围组织中的独特前体细胞,具有自我更新和多向分化潜能。目前大量科学研究显示HUCMSCs通过再生和修复衰老的细胞、组织和器官达到抗衰老作用。该文对HUCMSCs的生物学特性、组织再生修复作用和抗衰老治疗机制的研究进展进行了详细回顾,并对目前HUCMSCs临床前研究现况进行了总结,提示HUCMSCs是一种具有良好应用潜力和价值的干细胞类型。     

Regenerative cells for transplantation in hepatic failure

Human embryonic stem (ES) cells and induced pluripotent stem (iPS) cells have an enormous potential; however, their potential clinical application is being arrested due to various limitations such as teratoma formation followed by tumorigenesis, emergent usage, and the quality control of cells, as well as safety issues regarding long-term culture are also delaying their clinical application. In addition, human ES cells have two crucial issues: immunogenicity and ethical issues associated with their clinical application. The efficient generation of human iPS cells requires gene transfer, yet the mechanism underlying pluripotent stem cell induction has not yet been fully elucidated. Otherwise, although human adult regenerative cells including mesenchymal stem cells have a limited capacity for differentiation, they are nevertheless promising candidates for tissue regeneration in a clinical setting. This review highlights the use of regenerative cells for transplantation in hepatic failure.     

Stem cell transplantation as a therapeutic approach to organ failure

BACKGROUND: Stem cell transplantation is one of the next great frontiers for surgery. Stem cells, which are undifferentiated and self-renewing, have shown the ability to differentiate into cardiomyocytes, as well as many other cell types for potential therapeutic use by surgeons. MATERIALS AND METHODS: As a result, stem cells have the potential to undo irreversible cellular damage, something traditional therapies could not cure. However, numerous issues must be resolved to permit safe and effective clinical application of stem cell therapy. These include the interpretation of cellular labeling, the origin of replicating myocytes, the homing mechanism of stem cells, and the differentiation process. RESULTS: Successful translational research will depend on precise delivery of these cells in real time to the area of interest, e.g., the spinal cord, liver, or heart. Surgeons will be better able to excise and replace/regrow, rather than excise alone. As such, a basic understanding of stem cell biology will benefit the surgeon scientist and clinical surgeon. CONCLUSIONS: The review: 1) discusses myocardial regeneration; 2) defines and categorizes stem cells; 3) presents evidence of stem cell transdifferentiation into cardiomyocytes; and, 4) delineates the therapeutic potential of stem cells in the treatment of ischemic heart disease.     

Update cardiac stem cell therapy

Chronic ischemic heart disease remains one of the most important causes of morbidity and mortality worldwide. Although revascularisation procedures and conventional drug therapy may delay ventricular remodelling, there is no basic therapeutic regime available to prevent or even reverse this process. Chronic coronary artery disease and heart failure impair quality of life and are associated with subsequent worsening of left ventricular function. In the recent past experimental and clinical studies have demonstrated the capacity of bone marrow stem cells in cardiac repair and regeneration of compromised heart muscle. Several clinical trials showed the safety and efficacy of autologous bone marrow stem cell transplantation in the patients with acute myocardial infarction or chronic ischemic heart disease. Today the therapeutic strategy of cell administration during cardiac surgery or coronary artery intervention is entering the clinical practice. Biological as well as methodological backgrounds, indications and clinical results of cardiac stem cell therapy for the treatment of acute myocardial infarction and chronic ischemic heart disease are reviewed.     

Stem cell therapy-present status

Stem cell research is a new field that is advancing at an incredible pace with new discoveries being reported from all over the world. Scientists have for years looked for ways to use stem cells to replace cells and tissues that are damaged or diseased. Stem cells are the foundation cells for every organ, tissue, and cell in the body. Stem cells are undifferentiated, "blank" cells that do not yet have a specific function. Under proper conditions, stem cells begin to develop into specialized tissues and organs. They are self-sustaining and can replicate themselves for long periods of time. Embryonic stem cells are pluripotent cells, isolated from the inner cell mass of the blastocyst-stage mammalian embryo. They have the ability to differentiate into several somatic or somatic-like functional cells such as neurons, hepatocytes, cardiomyocytes, and others. Adult stem cells are specialized cells found within many tissues of the body where they function in tissue homeostasis and repair. They are precursor cells capable of differentiation into several different cells. The knowledge of stem cells from various sources offered a new hope for the treatment of various diseases.     

Funktionelle Regeneration des Herzinfarkts durch die Transplantation von Stammzell-Patches

Stem cell research has created great fascination over the last decade. However, early randomized clinical trials on regeneration of the heart did not reveal the very high functional regeneration potential that was observed in the preclinical setting. In addition, the mode of action for the autologous stem cells used in the trials was obscure, since almost no new contractile tissue developed. During a typical injection into the ischemic myocardium, large numbers of cells are lost, which is why scaffold-based applications have gained attention. The transplantation of stem cells seeded on scaffolds results in functional benefit, which might be due to the release of cytokines.     

Regenerative medicine for pancreatic beta cells

Regenerative medicine involves varying degrees of interaction among many research domains. Regenerative medical therapies based on research into organogenesis and the regeneration of injured or dysfunctional tissue using cell therapy are being developed rapidly. For the treatment of diabetes mellitus (DM), pancreatic transplantation and islet (pancreatic endocrine) cell transplantation are considered to be one form of regenerative medicine to overcome pancreatic tissue dysfunction. Recently, the effective islet cell transplantation Edmonton protocol has been established, ushering in a new era in regenerative therapy for DM. However, unresolved problems remain, including a severe donor shortage and unexpected side effects with the longterm use of some immunosuppressive agents. With continuing advances and the clinical application of fundamental therapy for DM, a pancreatic islet cell transplantation or bioartificial pancreatic transplantation system, consisting of islet (pancreatic endocrine) cell purification, pancreatic cell proliferation techniques, immunoisolative membrane technology, and an appropriate transplantation procedure, will be effective. This paper focuses on applied research on human and/or porcine pancreatic cell purification, embryonic stem cell differentiation, and pancreatic stem cell differentiation into functional insulin-producing cells.     

Efficient human fetal liver cell isolation protocol based on vascular perfusion for liver cell-based therapy and case report on cell transplantation

Although hepatic cell transplantation (CT) holds the promise of bridging patients with end-stage chronic liver failure to whole liver transplantation, suitable cell populations are under debate. In addition to hepatic cells, mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) are being considered as alternative cell sources for initial clinical cell work. Fetal liver (FL) tissue contains potential progenitors for all these cell lineages. Based on the collagenase incubation of tissue fragments, traditional isolation techniques yield only a fraction of the number of available cells. We report a 5-step method in which a portal vein in situ perfusion technique is used for tissue from the late second trimester. This method results in the high viabilities known for adult liver vascular perfusion, addresses the low cell yields of conventional digestion methods, and reduces the exposure of the tissue to collagenase 4-fold. We used donated tissue from gestational weeks 18 to 22, which yielded 1.8 ± 0.7 × 10(9) cells with an average viability of 78%. Because HSC transplantation and MSC transplantation are of interest for the treatment of hepatic failure, we phenotypically confirmed that in addition to hepatic progenitors, the resulting cell preparation contained cells expressing typical MSC and HSC markers. The percentage of FL cells expressing proliferation markers was 45 times greater than the percentage of adult hepatocytes expressing these markers and was comparable to the percentage of immortalized HepG2 liver hepatocellular carcinoma cells; this indicated the strong proliferative capacity of fetal cells. We report a case of human FL CT with the described liver cell population for clinical end-stage chronic liver failure. The patient's Model for End-Stage Liver Disease (MELD) score improved from 15 to 10 within the first 18 months of observation. In conclusion, this human FL cell isolation protocol may be of interest for further clinical translation work on the development of liver cell-based therapies.     

Rolle der Stammzelltherapie in der chirurgischen Behandlung der Herzinsuffizienz

Direct intramyocardial stem cell transplantation is entering clinical practice for the surgical treatment of heart failure. Relying on experience gained from Phase I and Phase II clinical trials with intramyocardial transplantation of autologous bone marrow stem cells, we report here on the current knowledge of this new“cell-based” therapeutic option in the cardiac surgeon’s hand. The underlying mechanisms of cardiac regeneration by stem cells transplantation, as currently postulated, are presented and new ways of delivery, including the surgical“stand alone” stem cell treatment, are discussed. Furthermore, the possible beneficial effects of cardiac cell therapy in non-ischemic heart disease and its impact in the clinical bridge-to-transplant scenario are discussed. Finally, we provide evidence for the immunomodulatory effects of transplanted bone marrow stem cells and their possible impact in solid organ transplantation.     

Stem Cell Therapy for Osteoporosis

Osteoporosis is a debilitating disease that affects millions of people worldwide. Current osteoporosis treatments are predominantly bone-resorbing drugs that are associated with several side effects. The use of stem cells for tissue regeneration has raised great hope in various fields of medicine, including musculoskeletal disorders. Stem cell therapy for osteoporosis could potentially reduce the susceptibility of fractures and augment lost mineral density by either increasing the numbers or restoring the function of resident stem cells that can proliferate and differentiate into bone-forming cells. Such osteoporosis therapies can be carried out by exogenous introduction of mesenchymal stem cells (MSCs), typically procured from bone marrow, adipose, and umbilical cord blood tissues or through treatments with drugs or small molecules that recruit endogenous stem cells to osteoporotic sites. The main hurdle with cell-based osteoporosis therapy is the uncertainty of stem cell fate and biodistribution following cell transplantation. Therefore, future advancements will focus on long-term engraftment and differentiation of stem cells at desired bone sites for tangible clinical outcome.     

脂肪基质血管片段分离的研究进展

脂肪基质血管片段(SVF)是脂肪组织经分解并去掉上清后得到的底层细胞团,SVF含有多种细胞群,包括脂肪来源干细胞(ADSC),内皮祖细胞,免疫细胞,平滑肌细胞,周细胞和其他基质成分。SVF在临床中有诸多应用研究,如脂肪移植,糖尿病,促进组织再生血管化等。脂肪组织的分离方法决定了SVF的数量和质量,本文对目前SVF分离技...     

Therapeutic angiogenesis and myocardial regenerative medicine for ischemic heart disease

We have a new therapeutic modality, regenerative medicine, for patients with severe ischemic heart disease. Growth factor administration and cell transplantation are available. Therapeutic angiogenesis with bone marrow cell transplantation has been used clinically with favorable results. Basic fibroblast growth factor slow-release administration has recently started to be used clinically as another angiogenic therapy. It is more potent when combined with a donor artery and omentum (Bio-CABG). Myogenic cell transplantation is in clinical trials aimed at myocardial regeneration. However, it remains unresolved how transplanted myoblasts improve cardiac function and how we can prevent fatal arrhythmia. Many are researching cardiac stem cells and embryonic stem cells as candidates for myocardial regeneration. Recently, the paracrine effects of transplanted mesenchymal stem cells in the ischemic heart have been reported to contribute to improved cardiac function. Therefore, growth factors and cytokines may play an important role in the regeneration process induced by transplanted cells. We combined cell transplanstation with growth factor administration as well as reconstructive surgery for dilated left ventricle, which yielded excellent results. Our integrated strategy may result in the maximal benefits to patients in the future.     

Adult stem cell therapy: dream or reality?

Adult stem cells may be an invaluable source of plastic cells for tissue regeneration. The bone marrow contains different subpopulations of adult stem cells easily accessible for transplantation. However the therapeutic value of adult stem cell is a question of debate in the scientific community. We have investigated the potential benefits of adult hematopoietic stem cell transplantation in animal models of demyelinating and motor neuron diseases. Our results suggest that transplantation of HSC have direct and indirect neuroregenerative and neuroprotective effects.     

Nonmyeloablative stem cell transplantation and cell therapy for malignant and non-malignant diseases

The conditioning prior to allogeneic stem cell transplantation was originally designed as a myeloablative conditioning, designed to eliminate malignant or genetically abnormal cells and then use the transplant procedure for rescue of the patients or to replace missing bone marrow products. However, allografts can induce effective graft vs. malignancy effects and can also eliminate undesirable hematopoietic stem cells in patients with genetic disorders and autoimmune diseases, thus documenting that alloreactive effects mediated by donor lymphocytes post-grafting can play a major role in eliminating hematopoietic cell of host origin, as well as provide effective immunotherapy for the treatment of disease recurrence. The efficacy of donor lymphocyte infusion (DLI) could be improved by activation with rIL-2 or by donor immunization. The cumulative experience over the years suggesting that alloreactive donor lymphocytes were most effective in eliminating tumor cells of host origin resulted in an attempt to reduce the intensity of the conditioning in preparation for the transplant procedure used for the treatment of hematological and other malignancies as well as life-threatening non-malignant disorders for which allogeneic stem cell transplantation may be indicated. Our working hypothesis proposed that the myeloablative conditioning which is hazardous and may be associated with early and late side effects, may not be required for treatment of patients with any indication for allogeneic stem cell transplantation. Instead, nonmyeloablative conditioning based on the use of reduced intensive preparatory regimen, also known as nonmyeloablative stem cell transplantation, may be sufficient for engraftment of donor stem cells while avoiding procedure-related toxicity and mortality, followed by elimination of undesirable cells of host origin by post-transplant effects mediated by alloreactive donor lymphocytes infused along with donor stem cells or administered subsequently as DLI. Improvement of the immediate outcome of stem cell transplantation using NST due to a significant decrease in transplant related mortality has broadened the spectrum of patients eligible for allogeneic stem cell transplantation, including elderly patients and other patients with less than optimal performance status. Likewise, the safer use of stem cell transplantation prompted expanding the scope of potential indications for allogeneic stem cell transplantation, such as metastatic solid tumors and autoimmune disorders, which now are slowly becoming much more acceptable. Current strategies focus on the need to improve the capacity of donor lymphocytes to eliminate undesirable malignant and non-malignant hematopoietic cells of host origin, replacing abnormal or malignant stem cells or their products with normal hematopoietic stem cells of donor origin, while minimizing procedure-related toxicity and mortality and improving the quality of life by reducing the incidence and severity of hazardous acute and chronic GVHD.