Limbal epithelial stem cells or LESCs are found at the periphery of the cornea and they continuously renew the corneal epithelium. Loss of this stem cell population can cause loss of corneal transparency and eventual loss of vision.
Treatments of LESC deficiency include limbal stem cell grafts from one eye to another, but these grafts have a 3-5-year graft survival of only 30%-45%. If LESCs are expanded in culture on human amniotic membrane, then 76% of the grafts will successfully take 1-3 years after grafting. This procedure is not standardized. If LESCs are grafted from a cadaver, their survival is low.
Given these less than optimal treatments for LESC deficiencies, Alexander Ljubimov and his team from UCLA have used induced pluripotent stem cells (iPSCs) to make cultured LESCs. Ljubimov and his coworkers derived iPSCs from the skin cells of volunteers with non-integrating plasmids. Then they grew these cells on corneas that have been stripped of their cells and human amniotic membranes and these cells differentiated into LESC-like cells.
Ljubimov and others also made iPSCs from human LESCs, and when they cultured these iPSCs derived from LESCs on human amniotic membranes for two weeks, the cells differentiated into LESCs that made LESC-specific genes, and had the epigenetic characteristics of LESCs.
These experiments show that the cell source for iPSC derivation can greatly influence the epigenetic characteristics of the iPSC line. Also these experiments show that iPSCs can be used to make LESCs that can potentially be used for therapeutic purposes.
Repairing cartilage defects in the knee represents one of the primary goals of orthopedic regenerative medicine. Cartilage that covers the joints, otherwise known as articular cartilage, has a limited capacity for repair, which leads to further degeneration of the cartilage when it is damaged if it remains untreated. A number of surgical options for treating cartilage defects include microfracture, osteochondral grafting, and cell-based techniques such as autologous chondrocyte implantation (ACI). Each of these procedures have been used in clinical settings. Unfortunately cartilage injuries treated with microfracturing deteriorate with time, since the cartilage made by microfracturing has a high proportion of softer. less durable fibrocartilage. Also osteochondral grafting suffers from a lack of lateral integration between host and donor cartilage.
Alternatively, tissue engineering has shown some promise when it comes to the healing of cartilage defects. Mesenchymal stem cells (MSCs) are multipotent progenitor cells that have the ability to differentiate into several different cell lineages including cartilage-making chondrocytes. MSCs have theoretical advantages over implanted chondrocytes when it come to healing potential. MSCs have the ability to proliferate without losing their ability to differentiate into mature chondrocytes and produce collagen II and aggrecan. In the short-term, bone marrow-derived MSCs combined with scaffolds have been successful in cartilage repair using animal models such as rabbits (Dashtdar H, et al., J Orthop Res 2011; 29: 1336-42) sheep (Zscharnack M, et al., Am J Sports Med2010; 38: 1857–69) and horses (Wilke MM, et al.,l J Orthop Res2007; 25: 913–2).
In a recent study, Kazumasa Ogasawara and Yoshitaka Matsusue and their colleagues from Shiga University of Medical Science in Shiga, Japan, tested the ability of expanded bone marrow-derived MSCs that had been placed in a collagen scaffold to improve healing of cartilage defects in cynomolgus macaques (type of monkey). Before this study, there were no previous studies using MSCs from primates for cartilage repair. The monkey MSCs were shown to properly differentiate into fat, bone, or cartilage in culture, and then were transplanted into the injured cartilage in the cynomolgus macaque. The efficacy of these cells were ascertained at 6, 12, and 24 weeks after transplantation.
In culture, the cynomolgus MSCs were able to differentiate into fat, bone, and cartilage.
Upon transplantation into cartilage defects in the knee cartilage of cynomolgus monkeys, MSCs were compared with collagen gel devoid of MSCs. The knees that received the transplantations did not show any signs of irritation, bone spurs or infection. All of the animals had so-called “full-thickness cartilage defects,” and those in the non-treated group showed cartilage defects that did not change all that much. The cartilage defects of the gel group had sharp edges at 6 weeks that were thinly covered with reparative tissue by 12 weeks, and at 24 weeks, the defect was covered with thick tissue, but the central region of the defects often remained uncovered, with a hollow-like deformity. In the cartilage defects of those animals treated with MSCs plus the collagen gel, the sharp edges of the defects were visible at 6 weeks after the operation, but at 12 weeks, the defects were evenly covered with yellowish reparative tissue. At 24 weeks, the defects were covered with watery hyaline cartilage-like tissue that was very similar to the neighboring naïve cartilage.
When evaluated at the tissue level, Ogasawara and Matsusue and others used a stain called toluidine blue to visualize the amount of cartilage made by each treatment. As you can see in the picture below, the non-treated group didn’t do so well. In the full-thickness defect the region below the cartilage was filled with amorphous stuff 6 weeks after the procedure, and at 12 weeks, amorphous stuff faintly stained with toluidine blue, which reflects the conversion of the amorphous stuff into bone. At 24 weeks, bone tissue reappeared below the cartilage zone, even though the bone did not look all that normal (no trabecular structure but woven bone-like structure).
In the gel group, cartilage-like tissue is seen at 6 weeks, and at 12 weeks, the faintly stained layer covered the cartilage defect. At 24 weeks, the defect was covered with the cartilage-like stuff, even though the central region had only a little cartilage, as ascertained by toluidine blue staining. The bone underneath the cartilage looked crummy and there was excessive growth of cartilage into the region underneath the cartilage layer.
In the MSC group, the bone underneath the cartilage healed normally, and at 12 weeks, the boundary between the articular cartilage and the bone layer beneath it had reappeared. At 24 weeks, the thickness of the toluidine blue-stained cartilage layer was comparable to that of the neighboring naïve cartilage.
Even though the gel group showed most cartilage-rich tissue covering the defect, this was due to the formation of excessive cartilage extruding through the abnormal lower bone layer. Despite the lower amount of new cartilage produced, the MSC group showed better-quality cartilage with a regular surface, seamless integration with neighboring naïve cartilage, and reconstruction of the bone underneath the cartilage layer.
This protocol has been nicely optimized by Ogasawara and Matsusue and their research team. From these data, they conclude: “Application in larger defects is certainly in line with future clinical use. If MSCs—under optimized conditions—turn out to be superior to chondrocyte implantation in experimental cartilage repair, the procedure should be introduced to clinical practice after well-controlled randomized clinical trials.” Hopefully, clinical trials will commence before long. This procedure uses a patient’s own MSCs, and if such a procedure could reduce or delay the number of knee replacements, then it would surely be a godsend to clinicians and patients alike.
Making tissue-specific progenitor cells that possess the ability to survive, but have not passed through the pluripotency state is a highly desirable goal of regenerative medicine. The technique known as “direct reprogramming” uses various genetic tricks to transdifferentiate mature, adult cells into different cell types that can be used for regenerative treatments.
Juan Carlos Izpisua Belmonte and his colleagues from the Salk Institute for Biological Studies in La Jolla, California and his collaborators from Spain have used direct reprogramming to convert human skin cells into a type of white blood cells.
These experiments began with harvesting skin fibroblasts from human volunteers that were then forced to overexpress a gene called “Sox2.” The Sox2 gene is heavily expressed in mice whose bone marrow stem cells are being reconstituted with an infusion of new stem cells. Thus this gene might play a central role is the differentiation of bone marrow stem cells.
Sox2 overexpression in human skin fibroblasts cause the cells express a cell surface protein called CD34. Now this might seem so boring and unimportant, but it is actually really important because CD34 is expressed of the surfaces of hematopoietic stem cells. Hematopoietic stem cells make all the different types of white and red blood cells in our bodies. Therefore, the expression of these protein is not small potatoes.
In addition to the expression of CD34, other genes found in hematopoietic stem cells were also induced, but not strongly. Thus overexpression of SOX2 seems to induce an incipient hematopoietic stem cell‐like status on these fibroblasts. However, could these cells be pushed further?
Gene profiling of hematopoietic stem cells from Umbilical Cord Blood identified a small regulatory RNA known as miR-125b as a factor that pushes SOX2-generated CD34+ cells towards an immature hematopoietic stem cell-like progenitor cell that can be grafted into a laboratory animal.
When SOX2 and miR-125b were overexpressed in combination, the cells transdifferentiated into monocytic lineage progenitor cells.
What are monocytes? They are a type of white blood cells and are, in fact, the largest of all white blood cells. Monocytes compose 2% to 10% of all white blood cells in the human body. They play multiple roles in immune function, including phagocytosis (gobbling up bacteria and other stuff), antigen presentation (identifying and altering other cells to the presence of foreign substances), and cytokine production (small proteins that regulate the immune response).
Monocytes express a molecule on their cell surfaces called CD14, and when human fibroblasts overexpressed Sox2 and miR-125b, they became CD14-expressing cells that looked and acted like monocytes. These cells were able to gobble up bacteria and other foreign material, and when transplanted into a laboratory animal, these directly reprogrammed cells generated cells that established the monocytic/macrophage lineage.
Cancer patients, and other patients with bone marrow diseases can have trouble making sufficient white blood cells. A technique like this can generate transplantable monocytes (at least in laboratory animals) without many of the drawbacks associated with reprogramming human cells into hematopoietic stem cells that possess true clinical potential. Also because this technique skips the pluipotency stage, it is potentially safer.
The regenerative medicine company Regeneus Ltd announced this week that the Australian Football League or AFL has decided to approve, on a case-by-case basis, the use of its innovative HiQCell stem cell therapy as an optional treatment for injured AFL players. Football (soccer) players tend to suffer from impact-related osteoarthritis and tendonitis.
Regeneus’ Commercial Development Director for Human Health, Steve Barbera, said, “It’s pleasing that HiQCell has been approved under the new AFL Prohibited Treatments List released in March 2014. HiQCell also received clearance as an approved therapy from the Australian Sports Anti-Doping Authority (ASADA) for use with athletes who participate in sporting competitions subject to the WADA Anti-Doping Code, including the AFL. This recent decision by the AFL demonstrates a further level of compliance, specifically for players within that sporting code.”
Regeneus’ HiQCell treatment is the only stem cell treatment for osteoarthritis that has been subjected to the highest level of clinical scrutiny. A double-blind placebo-controlled safety trial is the gold standard for clinical trials. The particular clinical trial to which HiQCell treatments were subjected showed that HiQCell is safe and it reduces pain and halts cartilage degradation in arthritic joints. Additionally, the ongoing effects of HiQCell are being tracked in over 380 patients in an independent ethics-approved registry. A recent registry update demonstrated that patients are maintaining significant improvements 2 years after their treatment.
HiQCell has already been used to treat several high-profile athletes across several sporting codes, including the National Rugby League, which was announced on May 7th, 2014. It is encouraging for Regeneus that elite sports patients can use their HiQ therapy to much quickly return to sports from hard-to-treat injuries and continue their playing careers after receiving this innovative therapy.
Dr Phil Bloom, a Melbourne based Specialist Sports and Exercise Physician and HiQCell treating medical practitioner, said, “permission from the AFL for HiQCell treatment is a positive progression as it allows for an additional option for players with conditions that are unresponsive to existing treatments”.
The HiQCell treatment uses stem cells harvested from a small amount of a patient’s fat. After separating and concentrating these regenerative cells, they are re-injected in osteoarthritic-affected joints such as knees, hips and ankles. The HiQCell treatment reduces inflammation and repairs damaged tissue when it is carried out under the supervision of a medical practitioner.
Nearly 10% of all Americans suffer from Dry eye syndrome (DES), which makes this disorder one of the most common ocular diseases. Most of the currently-available treatments are palliative, but few therapeutic agents target the biological causes of DES. Many factors contribute to DES, but one of the most important factors in the cause of DES is inflammation of the ocular surface.
Since mesenchymal stem cells (MSCs) have been shown to suppress inflammation, using MSCs to treat DES seems to be a viable treatment option. MSCs can also repair tissues by regulating excessive immune responses in various diseases.
Thus Joo Youn Oh from the Seoul National University in Seoul, Korea and his colleagues investigated the therapeutic potential of MSCs in a mouse model of an inflammation-mediated dry eye. They induced DES in these mice by injecting a plant protein into the eye that grabs sugars into the eye. This protein injection dries out the eyes in these mice and induces a kind of DES-like condition.
Then they found that the administration of MSCs into the eye reduced the infiltration of immune cells into the eye and overall decreased eye inflammation. Administration of MSCs into the eye also significantly increased tear production and also increased the number of conjunctival goblet cells, which secrete lubricating mucus so that the eye lid slides gently over the eye surface. Further investigation showed that the structural integrity of the eye surface, known as the cornea, was well-preserved by MSCs.
When taken together, ocular administration of MSCs seem to suppress the inflammation that either accompanies or contributes to DES. These results also suggest that MSCs may provide a potential therapy for those diseases that cause inflammation of the ocular surface and adversely affect the eye because of it.
Since my father died of disseminated lung cancer (squamous cell carcinoma), this report has particular meaning to me.
When a person dies, their lungs can be harvested and stripped of their cells. This leaves a so-called “lung scaffold” that can then be used to build new lungs by means of tissue engineering techniques. Lung scaffolds consist of a protein called collagen, and sugar-rich proteins called “proteoglycans” (say that fast five times) and a rubber band-like protein called elastin. Depending on how the lung scaffolds are made more or less of these components can remain in the lung scaffold (see TH Peterson, and others, Cells Tissues Organs. Feb 2012; 195(3): 222–231). The important thing is that the cells are gone and this greatly reduces the tendency for the lung scaffold to be rejected by someone else’s immune system.
Once a lung scaffold is generated from a whole lung, cells can be used to reconstitute the lung. The key is to use the right cell type or mix of cell types and to induce them to form mature lung tissue.
The laboratory of Harald Ott at Harvard University Medical School used a technique called “perfusion decellularization” to make lung scaffolds from the lungs of cadavers. Then he and his co-workers used lung progenitor cells that were derived from induced pluripotent stem cells (iPSCs). This study was published in The Annals of Thoracic Surgery, and it examined the ability of iPSCs to regenerate a functional pulmonary organ
Whole lungs from rat and human cadavers were stripped of their living material by means of constant-pressure perfusion with a strong detergent called sodium dodecyl sulfate (SDS; 0.1% if anyone is interested). Ott and his crew then sectioned some of the resulting lung scaffolds and left others intact, and then applied human iPSCs that had been differentiated into developing lung tissue.
Lung tissue develops from the front part of the developing gut. This tissue is called “endoderm,” since it is in the very innermost layer of the embryo.
Therefore, the iPSCs were differentiated into endoderm with a cocktail of growth factors (FGF, Wnt, Retinoic acid), and then further differentiated in the anterior endoderm (foregut; treated cells with Activin-A, followed by transforming growth factor-β inhibition), and then even further differentiated into anterior, ventral endoderm, which is the precise tissue from which lungs form. In order to be sure that this tissue is lung tissue, they must express a gene called NK2 homeobox 1 (Nkx2.1). If these cells express this gene, then they are certainly lung cells.
Ott and his group showed that their differentiate iPSCs strongly expressed Nkx2.1, and then seeded them on slices and whole lung scaffolds. Then Otts’s group maintained these tissues in a culture system that was meant to mimic physiological conditions.
Those cells cultured on decellularized lung slices divided robustly and committed to the lung lineage after 5 days. Within whole-lung scaffolds and under the physiological mimicking culture, cells upgraded their expression of Nkx2.1. When the culture-grown rat lungs were transplanted into rats, they were perfused and ventilated by host vasculature and airways.
Thus these decellularized lung scaffolds supports the culture and lineage commitment of human iPSC-derived lung progenitor cells. Furthermore, whole-organ scaffolds and a culture system that mimics physiological conditions, allows scientists to enable seeding a combination of iPSC-derived endothelial and epithelial progenitors and enhance early lung fate. Transplantation of these laboratory-grown lungs seem to further maturation of these grafted lung tissues.