Last update on September 2018
The ANTHOS project (Prerequisites for the use of mesenchymal stromal cells (MSC) combined with locally injected hydrogel and HS-mimetic for treating the side effects of abdominal-pelvic radiation therapy) aims to improve the effectiveness of MSC-based cell therapy in treating the severe side effects that may be induced by pelvic radiation therapy. The project, launched in February 2014 and scheduled to run for three years, is coordinated by IRSN (LR2I, the IRSN Laboratory for Research on Irradiated Healthy Tissue Regeneration). It was selected following the ANR call for proposals in connection with RPIB, a biomedical innovation program that seeks to promote the transfer of public research results for industrial applications in healthcare.
Background and goals
Between 3 and 5% of patients receiving radiation therapy to treat abdominal-pelvic cancers develop severe intestinal complications five years after the treatment has ended. These severe radiation-induced lesions occasionally require high-risk surgery and, until now, the effectiveness of any drug treatment given at an early stage has not been demonstrated.
Recently, IRSN, Saint Antoine University Hospital in Paris and CTSA Percy, the French Armed Forces Blood Transfusion Center, have demonstrated that intravenous injection of mesenchymal stromal cells (MSC) derived from bone marrow improves healing of colorectal ulcers. The demonstration involved different types of animal models (mice, rats and mini-pigs) as well as patients receiving experimental treatment (following the accident at Épinal).
This recent research at IRSN has furthered our understanding of the mechanisms involved in the tissue repair action of MSCs, in particular their action on the molecules that activate repair. As a result of this research, the treatment protocol currently in clinical use (systemic-injection of MSCs) may be improved and the ANTHOS project aims to test a number of potential ways to achieve this.
The ultimate goal is to be able to offer surgeons specializing in Gastroenterology a clinical-grade treatment protocol that will make it possible to avoid surgery for the least severe lesions (grade III) and improve post-surgery healing of the most severe lesions (grade IV). The use of cell therapy on its own or in combination with surgery could also find applications other than in treating the severe complications induced by radiation therapy, including the treatment of other inflammatory diseases of the colon (Crohn's disease and ulcerative colitis, for example).
Aiming to improve the effectiveness of MSCs, the ANTHOS project will develop a therapeutic strategy combining MSCs and a protective biomaterial with RGTAs - ReGeneraTing Agents - designed to stimulate the MSCs’ therapeutic capacities. The following points will be assessed:
- Local injection of MSCs by means of colonoscopy to increase the number of MSCs that reach the damaged tissue,
- The improved survival of MSCs in the damaged tissue by protecting the cells in HydroxyPorpylMethyl Cellulose (HPMC), a hydrogel which will serve as a matrix,
- The ability of RGTAs - ReGeneraTing Agents - to restore the microenvironment and enhance the regenerative capacity of MSCs.
The ANTHOS project will thus involve three main parts:
- biomaterial engineering;
- in vitro experiments on cell cultures;
- an assessment of the in vivo therapeutic benefits on a rat model developing radiation-induced colorectal ulceration combined with post-irradiation surgery.
The first stage of the project will entail development of a product consisting of the biomaterial in conjunction with the RGTAs and which will be easy to use during a colonoscopy (viscoelasticity, diffusion and adhesion tests).
The MSCs will then be incorporated into this hydrogel + RGTA combination and the cells' viability will be assessed, in particular by analyzing MSC secretion. This analysis will be carried out on rat MSCs and also on clinical grade human MSCs produced by E-cell France.
The third stage will aim to validate in vivo the improvement in the effectiveness of this combination injected locally in severe radiation-induced colic lesions. The results will enable the researchers to assess the benefits of this new strategy, comparing it to the reference protocol currently in clinical use, and also to identify the most functionally-beneficial combination.
At the end of the project, the results may lead to clinical trials on this new treatment strategy.
Aiming to improve the effectiveness of MSCs,, the chosen strategy for the ANTHOS project relies on a local injection in the colon of adipose-derived MSC (AD-MSC) protected in a hydrogel (silanized hydroxypropyl methylcellulose, or Si-HPMC). AD-MSC have the same therapeutic benefits as MSC from bone marrow (which have been used traditionally), but they are easier to collect with simple liposuction. The purpose of local administration by colonoscopy is to increase compared with intravenous administration, the success rate of cell transplantation at the damaged site and to reduce the number of cells injected (1 million instead of 5 million). In addition, the AD-MSC are encapsulated in a hydrogel, a matrix which protects them and thus increases their lifespan in the organism.
One of the first steps of the program for Nantes University Hospital consisted in adapting a hydrogel for use in the colon. This material had already proven itself in the treatment of cardiac ischemia but required the necessary rheological properties to be easily injectable with a coloscope. The next step involved an in vitro evaluation of the viability of AD-MSC incorporated into this matrix as well as their capacity to secrete active molecules. This led to a determination of the optimal concentration of hydrogel. After 21 days, 95% of the AD-MSC were still viable, with complete secreting functions.
Lastly, IRSN's researchers performed experiments in vivo on rats to validate the most effective treatment protocol with this combination of AD-MSC and biomaterial. Three series of rats were exposed to a dose of ionizing radiation creating radiation-induced colic lesions comparable to those of patients targeted by this future therapeutic protocol. They then received either AD-MSC alone by systemic intravenous injection, or AD-MSC alone locally, or AD-MSC with hydrogel locally. One week after administration of the treatment, the comparative analysis showed that the structure of the epithelium benefited from the effects of the AD-MSC-hydrogel pair: there was a significant reduction in the lesions of the colon mucosa and a notable increase in the process to regenerate the crypts that make up the epithelium. Same finding for the epithelial function: unlike the AD-MSC injected intravenously, the locally injected biomaterial significantly reduced the hyperpermeability of the colon as well as the inflammation reaction that is an inherent part of the radiation-induced lesions. This is all the more true since the AD-MSC combined with hydrogel also limit the infiltration of macrophages near the zone where the cells were injected, while these are known to sustain inflammation.
These preclinical results show that the AD-MSC-hydrogel combination developed by IRSN and the University of Nantes provides numerous benefits: effective treatment, ease of administration, etc. Studies further to the ANTHOS program on the benefit of an added molecule, known as a regenerating agent (RGTA) are under way. IRSN is also continuing to carry out studies on the harmlessness of cellular therapy treatment, whether associated with biomaterials or not, aiming for a clinical application in the medium term.