Stem Cells Derived From Amniotic Tissues Have Immunosuppressive Properties

Ever since they were first isolated, amnion-based stem cells have been considered promising candidates for cell therapies because of their ease of access, plasticity, and absence of ethical issues in their derivation and use. However, a Japanese research team has discovered that stem cells derived from human female amnion also have the ability to suppress the inappropriate activation of the immune system and that there are straight-forward ways to enhance their immunosuppressive potential.

The amniotic membrane is a three-layered structure that surrounds the baby and suspends it in amniotic fluid. Amniotic fluid acts as a protective shock-absorber, a lubricant and an important physiological player in the life of the embryo and fetus. Because the fetus is a privileged entity that escapes attack from the mother’s immune system, researchers have been very interested in determining the immunological properties of the amnion cells.

“The human amniotic membrane contains both epithelial cells and mesenchymal cells,” said study co-author Dr. Toshio Nikaido, Department of Regenerative Medicine, Graduate School of Medicine and Pharmaceutical Sciences at the University of Toyama. “Both kinds of cells have proliferation and differentiation characteristics, making the amniotic membrane a promising and attractive source for amnion-derived cells for transplantation in regenerative medicine. It is clear that these cells have promise, although the mechanism of their immune modulation remains to be elucidated.”

In this study by Nikaido and his coworkers, amnion-derived cells inhibited natural killer cell activity and induced white blood cell activation. Nikaido reported that he and his colleagues saw the amnion-derived cells increase production of a molecule called interleukin-10 (IL-10).

“We consider that IL-10 was involved in the function of amnion-derived cells toward NK cells,” explained Dr. Nikaido. “The immunomodulation of amnion-derived cells is a complicated procedure involving many factors, among which IL-10 and prostaglandin E2 (PGE2) play important roles.”

Molecules called “prostaglandins,” such as PGE2, mediate inflammation, smooth muscle activity, blood flow, and many other physiological process. In particular, PGE2 exerts important effects during labor and stimulates osteoblasts (bone-making cells) to release factors that stimulate bone resorption by osteoclasts. PGE2 also suppresses T cell receptor signaling and may play a role in the resolution of inflammation.

When Nikaido and others used antibodies against PGE2 and IL-10, they removed the immunosuppressive effects of the amnion-derived cells on natural killer cells. These data imply that these two factors contribute to the immunosuppressive abilities of amnion-derived cells.

“Soluble factors IL-10 and PGE2 produced by amnion-derived cells may suppress allogenic, or ‘other’ related immune responses,” concluded Dr. Nikaido. “Our findings support the hypothesis that these cells have potential therapeutic use. However, further study is needed to identify the detailed mechanisms responsible for their immodulatory effects. Amnion-derived cells must be transplanted into mouse models for further in vivo analysis of their immunosuppressive activity or anti-inflammatory effects.”

Given the levels of autoimmune diseases on the developed world, these results could be good news for patients who suffer from diseases like Crohn’s disease, systemic lupus erythematosus, or rheumatoid arthritis. While more work is needed, amnion-based cells certainly show promise as immunosuppressive agents.

The study will be published in a future issue of Cell Transplantation.

Clinical-Scale NK Cells for Cancer Therapy Made from Pluripotent Stem Cells

Dan Kaufman’s laboratory has done it again. The Kaufman laboratory at the University of Minnesota in collaboration with scientists from MD Anderson Cancer Center in Houston, Texas have designed a protocol to make natural killer cells from embryonic stem and induced pluripotent stem cells.

Natural killer cells provide a very important contribution to the innate immune response. These cells produce molecules called cytokines and they also kill virally infected cells and malignant cells. NK cells are unique among the cells of the immune system in that they have the ability to recognize foreign, infected or stressed cells in the absence of antibodies and Major Histocompatibility Complex proteins (the cell surface proteins that act as bar codes used by the immune system uses to determine if a cell is yours or not yours). Therefore, NKs typically work faster than the rest of the immune system.

Natural killer cells or NK cells have been used to treat patients with refractory cancers. Unfortunately, a major problem with using NK cells is growing a sufficient quantity of cells for therapy. Using pluripotent stem cells to make NK cells is an intriguing possibility, but the protocols for differentiating NK cells from embryonic stem cells (ESCs) is tedious and inefficient. However, the Kaufman laboratory has provided a much more efficient and straight-forward way to derive NK cells, thus allowing for the production of clinical scale quantities of NK cells.

The Kaufman lab protocol involves first deriving embryoid bodies from ESCs or induced pluripotent stem cells (iPSCs), which are made from adult cells through genetic engineering techniques that causes the cells to de-differentiate into ESC-like cells known as iPSCs. Embryoid bodies are three-dimensional aggregates of pluripotent stem cells that assume a kind of spherical shape and have a variety of cells differentiating into a wide range of cell types. Embryoid bodies can contain beating heart muscle, neural-type cells, blood progenitors cells, and even muscle or bone cells in their interiors in a haphazard arrangement. Forming embryoid bodies or EBs from cultured ESCs or iPSCs is rather easy, but controlling the differentiation of the cells in the EBs is quite another matter.

embryoid bodies
embryoid bodies

Kaufman and others discovered that if the EBs were incubated with artificial antigen-presenting cells that expressed a surface-bound version of the protein IL21 (interleukin 21) plus a cocktail of cytokines, these pluripotent stem cells could efficiently form NK cells.

Functional assays of the NK cells differentiated from ESCs and iPSCs easily showed that the NK cells for functional in every way and expressed all the cell surface molecules characteristic of NK cells. Furthermore, all ESC and iPSC lines examined were able to make NK cells, but the efficiency with which they made them different rather widely.

In conclusion, Kaufman and others state in their paper, “our ability to now produce large numbers of cytotoxic NK cells means that prospect hESC- and iPSC-derived hematopoietic products for diverse clinical therapies can be realized in the not-too-distant future.” For some cancer patients, that day cannot come soon enough.

Engineered T Cells Help a Child Get Rid of Leukemia

Pediatric oncologists from The Children’s Hospital of Pennsylvania (CHOP) and collaborating scientists from the University of Pennsylvania (UPenn) have used genetic engineering techniques to reprogram T lymphocytes from a young cancer patient’s blood. This reprogramming drove the T cells to attack the child’s leukemia, and, to date, has completely cured the child of leukemia.

Stephan Grupp, a pediatric oncologist from CHOP, is part of a clinical trial that tests cell therapy for adult chronic lymphocytic leukemia (CLL). CLL is the most common type of leukemia in adults and usually occurs during or after middle age and only rarely occurs in children.

As regular readers of this blog are aware, the bone marrow contains a stem cell population called hematopoietic stem cells. While this stem cell population is not a homogeneous one, these stem cells divide to renew themselves and replenish all the blood cells that we lose each day. When the hematopoietic stem cells divide, they renew themselves and give rise to either a myeloid or lymphoid progenitor cells. Myeloid progenitors differentiate into one of three types of mature blood cells: 1) red blood cells, which carry oxygen and the other substances to all tissues in the body; 2) white blood cells that fight infection and disease; 3) platelets that form blood clots to stop bleeding. Lymphoid progenitors become lymphoblast cells which then differentiate to become one of three cell types: 1) B lymphocytes, which make antibodies to fight infection; 2) T lymphocytes that help B lymphocytes to make antibodies to fight infection; 3) natural killer cells that attack cancer cells and viruses.

Hematopoietic stem cells

CHOP’s Stephen Grupp and Carl June, of the Perelman School of Medicine at the Univ. of Pennsylvania, lead this research group. Together, they have presented new data at the American Society of Hematology annual meeting in Atlanta that shows nine of 12 patients with advanced leukemias in the clinical trial, including two children, who responded to treatment with their newly engineered cells. This treatment strategy uses an engineered T lymphocyte that Grupp and June call “CTL019 cells.” By reprogramming the T cells to specifically attack this aggressive form of leukemia, some of these patients showed a complete remission of their leukemias.

Of the nine patients who responded to CTL019 treatment, one was a 7-year-old patient who suffered from acute lymphoblastic leukemia (ALL). Grupp and Penn colleagues adapted their treatment to combat ALL, which is the most common type of childhood leukemia and the most common childhood cancer. Although physicians cure roughly 85 percent of ALL cases, the remaining 15 percent of such cases stubbornly resist treatment.

Grupp’s research builds on his ongoing collaboration with scientists from UPenn. These UPenn researchers developed modified T cells as a treatment for B-cell leukemias. T cells are at the center of the immune response. T lymphocytes recognize and attack invading foreign invaders, but cancer cells slip under their surveillance net because they are so similar to normal cells. CAR T cells, which stands for “chimeric antigen receptor T cells” are engineered to specifically detect and target cancerous B cells. Since the B cells are the cancerous cells in the case of certain leukemias, such as ALL and CLL, CAR T cells can purge the body of these cancers rather effectively.

On the surface of B cells is a protein called CD19. By raising high-affinity antibodies to CD19 and then physically attaching those antibodies to T cells, UPenn researchers invented a kind of guided missile that detects and destroys B cells and B-cell leukemias.

When Grupp and his crew used CLT019 in his pediatric patients, they found that the engineered T cell was very active, but it caused an undesirable side effect called cytokine release syndrome. The child became very ill and was admitted to the intensive care unit. However, Grupp and his team counteracted these toxic side effects by using two 2 drugs that suppress the immune response and these thwarted the overactive immune response and rapidly relieved the child’s treatment-related symptoms. An added bonus was that these drugs had no effect on the engineered T cells, which still destroyed leukemia cells until the cows came home. These results were so effective, that this clinical approach is now being successfully incorporated into CTL019 treatments for adults as well.

The CHOP/UPenn team reported on early results of this clinical trial in adult chronic lymphocytic leukemia (CLL) patients in August of 2011. In their seven-year-old patient, they engineered her own T cells to attack her aggressive form of childhood leukemia. Without this treatment, she faced grim prospects once her cancer relapsed after conventional treatment. However, with this innovative CTL019 experimental therapy, the bioengineered T cells multiplied rapidly in her body and destroyed the leukemia cells. After her CTL019 treatment, the child’s doctors found that she had no evidence of cancer.

According to Grupp: “These engineered T cells have proven to be active in B cell leukemia in adults. We are excited to see that the CTL019 approach may be effective in untreatable cases of pediatric ALL as well. Our hope is that these results will lead to widely available treatments for high-risk B cell leukemia and lymphoma, and perhaps other cancers in the future.”

Susan Rheingold, one of the leaders in the Children’s Hospital program for children with relapsed leukemia added: “This type of pioneering research addresses the importance of timing when considering experimental therapies for relapsed patients. To ensure newly relapsed patients with refractory leukemia meet criteria for options like CTL019, we must begin exploring these innovative approaches earlier than ever before. Having the conversation with families earlier provides them more treatment options to offer the best possible outcome.”

In August 2012, the biotechnology company Novartis acquired exclusive rights from UPenn to CART-19, the therapy that was the subject of this clinical trial and which is now known as CTL019.