3 research outputs found
Peripheral nerve glia as multipotent progenitors in craniofacial development
Craniofacial development is complex. Numerous populations of progenitor cells coordinate
activities to produce an array of highly integrated tissues inside the developing head.
However, it is not clear how some key multipotent progenitors continue to exist in late
developing head compartments. The general hypothesis of this thesis is focused around the
idea of an embryonic infrastructure represented by peripheral nerves that serves as a niche for
glial multipotent neural crest-like cells. The nerve-adjacent glial cells can change their fate
and be recruited in a targeted way to produce tissues at remote destinations during fast
growth, development and regeneration. Results presented in this thesis explain how the
nerves contribute pulp cells and matrix-producing cells of odontoblast lineage to the
developing and growing tooth. Glial cells as an unexpected progenitor source give rise to
almost half of all pulp cells and odontoblasts in the growing incisor. Furthermore, lineage
tracing with colour-coding of individual recombination events allowed us to discover new
aspects of tooth development and coordination between pulp cell lineage and odontoblasts.
Another important component of the craniofacial compartment, the parasympathetic nervous
system that targets glands in the head, is crucial for "rest-and-digest" or "feed and breed"
activities especially during eating, salivation and lacrimation. Importantly, neurons of the
autonomic parasympathetic nervous system are located very close to or inside the tissues they
innervate and appear late in embryonic development. The discrepancy in developmental
timing raised new questions: how do early neural crest-derived progenitors of
parasympathetic neurons reach their destinations, and how do they acquire neuronal
properties in situ? Furthermore, what is the nature of those progenitor cells? Our results
clearly demonstrate that cells of glial origin located in the peripheral nervous system possess
multipotency and gives rise to parasympathetic neurons during later developmental stages.
Peripheral glial cells arrive to late-developing tissues on the pioneer presynaptic nerve fibres.
Subsequently, some glial cells change fate, navigate for short distances and then convert into
neurons and satellite cells of parasympathetic ganglia. Our conclusions redraw a fundamental
principle on how the peripheral nervous system develops and provide a new type of logic,
where both the cellular elements, as well as, the wiring are solved by a simple deposition of
the postsynaptic elements from the presynaptic.
During our work we used a wide spectrum of approaches including advanced genetic tracing
with multicolor reporters, analysis of numerous mouse mutants, in vitro cell cultures and 3D
imaging of developing embryos. We have applied both genetic and surgical ablation
techniques to the peripheral nerves and investigated targeted recruitment of glia from the
nerves in each case.
Peripheral glia represents a novel amenable source of multipotent progenitor cells with
putative regenerative potential that in the future might be applied for the treatment of
congenital craniofacial pathologies, trauma cases or used for aesthetic body treatments
Glial origin of mesenchymal stem cells in a tooth model system
Mesenchymal stem cells occupy niches in stromal tissues where they provide sources of cells for specialized mesenchymal derivatives during growth and repair. The origins of mesenchymal stem cells have been the subject of considerable discussion, and current consensus holds that perivascular cells form mesenchymal stem cells in most tissues. The continuously growing mouse incisor tooth offers an excellent model to address the origin of mesenchymal stem cells. These stem cells dwell in a niche at the tooth apex where they produce a variety of differentiated derivatives. Cells constituting the tooth are mostly derived from two embryonic sources: neural crest ectomesenchyme and ectodermal epithelium. It has been thought for decades that the dental mesenchymal stem cells giving rise to pulp cells and odontoblasts derive from neural crest cells after their migration in the early head and formation of ectomesenchymal tissue. Here we show that a significant population of mesenchymal stem cells during development, self-renewal and repair of a tooth are derived from peripheral nerve-associated glia. Glial cells generate multipotent mesenchymal stem cells that produce pulp cells and odontoblasts. By combining a clonal colour-coding technique with tracing of peripheral glia, we provide new insights into the dynamics of tooth organogenesis and growth