Mechanisms of hESC derived MSCs and BMSSCs to regenerate bone tissue

Funding Type: 
SEED Grant
Grant Number: 
ICOC Funds Committed: 
Disease Focus: 
Stem Cell Use: 
Embryonic Stem Cell
Public Abstract: 
We postulate that if bone marrow stromal stem cells or mesenchymal stem cells (MSC) derived from human ESCs can be enriched for osteoprogentior cells the likelihood of engraftment in to new bone after transplantation is going to be high resulting in long term bone repair and new bone formation in patients with bone diseases. Thus, we propose using human embryonic stem cells as a model system to determine whether TWIST expression can be used to enrich MSCs as a novel cell therapy strategy for bone regeneration. TWIST is a Helix-Loop-Helix transcription factor that is known to be a strong inhibitor of osteoblast differentiation. Our laboratory has recently demonstrated that expressing TWIST enriches for osteoblast precursor cells from adult bone tissue in culture. Therefore, allowing TWIST to be overexpressed in human embryonic stem cell derived mesenchymal stem cells (hMSC) under an inducible promoter should allow the enrichment of MSCs ex vivo, and, when turning off TWIST, osteoblast differentiation will be enabled after transplantation. Our laboratory has spent many years isolating and characterizing both mouse and human TWIST in osteoblasts and we are now embarking on new therapeutic applications of this factor in bone diseases. One of the major shortcomings in using bone marrow transplantation for cell therapy in bone diseases is the lack of osteoblast precursor cells. This lack of precursor cell enrichment results in little, if any engraftment of osteoblasts into new bone. Although external factors are presently being used, gene therapy relies on high levels of osteoblast engraftment if the therapy is going to have any phenotypic effect on bone formation, especially with respect to the following bone diseases; osteoporosis, which is prevalent in women over 50; osteogenesis imperfecta (OI) is a serious bone disorder that is usually present at birth as an inherited disease; metastatic cancers such as prostate and breast that can result in cancer induced bone disease leaving the patient in terrible pain for the duration of their life; and for the repair of damage in patients with tooth loss or weakened facial or skeletal bones. We hypothesize that TWIST will have a dramatic effect on stem cell enrichment, and will improve the outcome of hESC cell therapy in humans with bone disease or in need of bone repair. .
Statement of Benefit to California: 
This proposed research will benefit the State of California and its citizens in the following ways. First of all, many Californians are "Baby Boomers" who are over 50 and are now suffering from osteoporosis, dental tooth decay, and osteoarthritis resulting hip and knee replacements. Current medicine is deficient in the supply of tissues for bone transplantation. By generating a renewable supply of human MSCs, we hope to circumvent this short supply for future bone tissue regeneration. Secondly, cancer survivors living in California who are in remission are now suffering cancer induced bone disease either from their surgeries or treatment regimens are in need of bone tissue replacement or repairs to relieve them of terrible bone pain. With CIRM funding we now have the ability to use human embryonic stem cells to study the underlying mechanisms of bone formation that will allow us to customize treatments using the hESCs with patients own stem cells to prevent rejection for use in bone replacement and repairs. This proposed project is simply not feasible due to Federal restrictions on the use of hESC. If our hypothesis proves to be correct and mesenchymal stem cells derived from human ESCs can be enriched for osteoprogentior cells, the likelihood of engraftment into new bone after transplantation is going to be high, resulting in long term bone repair and new bone formation in patients with bone diseases. Therefore, Californians receiving hESC cell therapy for bone repairs should be able to remain ambulatory longer, and living more active lives and with less pain. This in turn results in fewer hospital visits for bone fractures. Reduced hospital costs will result in less financial burden on the State of California Health Insurance rates.
Progress Report: 
  • During the past reporting period, we have treated two different lines of human embryonic stem cells with a growth factor, BMP4, and differentiated them (i.e., made them change their character) down the pathway towards becoming a precursor of the human placenta. We have found that these cells initially lose their stem cell characteristics and change their appearance from stem cells to trophoblast (placental) cells. In addition, we conducted a study over 12 days in which these cells exhibited these changes, and we looked at not only their appearance, but also all the genes that they express, using whole genome array technology. We found that they lose their stemness and acquire genes important for commitment to be placental cells. Furthermore, we investigated the cellular pathways that are involved, and these are very fundamental for differentiating these cells to the placental phenotype (i.e., appearance and gene signature). Also, we are investigating whether another cell line has similar characteristics, and we are comparing all the genes expressed in the trophoectomer shell surrounding a human embryo (blastocyst) with the gene profiles in the trophoblast cells derived from human embryonic stem cells. Furthermore, we have studied the effects of products secreted by these cells on the first cells that the blastocyst encounters when it attaches to the mother’s lining of the uterus during the process of implantation. We have used a human endometrial epithelial cell line, to see if there are any effects, since we do not know if the levels of secreted products can indeed result in a response from the mother's uterus. We found an interesting array of factors that are regulated, and we are now poised to study human endometrial epithelial cells (not a cell line), since we know that a response occurs in these pilot studies with a cell line. The ultimate goal is to define proteins secreted by human blastocysts and predict which blastocysts have a profile that is consistent with an ability to attach to the mother’s uterus and then begin the process of implantation.

© 2013 California Institute for Regenerative Medicine