Development of an Autologous Myogenic Cell Therapy against the Neuromuscular Phenotype of Myotonic Dystrophy type 1.

Myotonic dystrophy (dystrophia myotonica, DM1) is a chronic progressive
multisystemic disorder characterized by myotonia, muscular dystrophy and
cognitive problems including; mild-severe intellectual disability, behavioural
changes, speech disability and hypersomnia. It is the most common adult form of
muscular dystrophy, with a prevalence of approximately 10 per 100,000 people.
The genetic basis of DM1, a CTG-repeat expansion in the 3* untranslated region
of the DMPK gene, was elucidated in 1992, but so far no treatment is available.
However, cell-based therapies have recently emerged as an attractive
therapeutic approach for neuromuscular disorders. Pericytes are progenitor
cells that can be isolated from adult muscle tissue. They have the ability to
colonize muscle tissue and contribute to regeneration of the dystrophic muscle.
These properties have prompted investigations towards the use of pericytes in
the treatment of Duchenne Muscular Dystrophy and Limb-Girdle Muscular
Dystrophy. Here, we propose to generate genetically modified autologous
pericytes in which the disease-causing CTG-repeat has been removed by
CRISPR/Cas9 genome editing. In consecutive research, these cells will form the
basis for a therapeutic approach in DM1.

In this project we use skeletal muscle biopsy tissue from DM1 patients and
controls to isolate pericytes. These muscle-derived mesodermal cells can be
genetically corrected by the novel powerful CRISPR-Cas9 technique, which will
remove the disease causing repeat expansion. Pericytes have the potential to
functionally integrate in skeletal muscle fibers and contribute to muscle
regeneration. Human pericytes will be used for the proof-of-concept of
generation of edited pericytes from human skeletal muscle biopsies. We are
interested to see whether isolation, genetic manipulation and expansion will
give us enough genetically corected autologous pericytes for therapeutic
administration.

In this project we propose a preclinical study aimed to investigate the
feasability of a cellular therapy against the neuromuscular phenotype in DM1.
Pericytes obtained from DM1 patients by a quadriceps (vastus lateralis) muscle
biopsy are genetically corrected by CRISPR-Cas9 and amplified to obtain the
maximum number of genetically corrected autologous pericytes for therapeutic
application.

When performed by a skilled physician in a defined clinical setting, the
incidents associated muscle biopsy in volunteers are reasonable and rare. The
van Engelen group routinely performs regular and MR-guided muscle biopsies, and
has ample experience. There are no clinically defined major complications
associated with the procedure. In extremely rare cases, infection or bleeding
occurs after muscle biopsy. In some cases patients report pain, nausea, or
dizziness.

There is no direct benefit for DM1 patients involved in this study. Treatment
with autologous corrected pericytes will only be studied in animal models. In
this feasibility study, human pericytes will only be used for the
proof-of-concept of generation of edited pericytes. Therefore, the primary
benefit will be better knowledge on the potential of a cellular therapy against
the neuromuscular phenotype of DM1. No treatment is currently available for the
neuromuscular disorder. Performing this research will provide valuable
information about the possibility to use autologous genetically corrected
pericytes as a promising cellular therapy in DM1.