To scar or not to scar : origin and function of fibrotic tissue in the central nervous system
After injury, the adult mammalian central nervous system lacks long-distance axon regeneration, and insufficient repair results in the formation of a multicellular and compartmentalized scar. A great body of work has been dedicated to the study of the glial component of the scar, while the fibrotic...
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Format: | Dissertation |
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Zusammenfassung: | After injury, the adult mammalian central nervous system lacks long-distance axon
regeneration, and insufficient repair results in the formation of a multicellular and
compartmentalized scar. A great body of work has been dedicated to the study of the glial
component of the scar, while the fibrotic lesion core has received less attention. This thesis
aims to deepen our knowledge on the cellular origin and function of fibrotic scar tissue
following central nervous system injury and disease.
In Paper I we revealed that a subset of perivascular cells lining the vasculature, termed type
A pericytes, is the major source of stromal fibroblasts that constitute the extracellular matrixrich
fibrotic component of the central nervous system scar following spinal cord injury in the
mouse. Maximal genetic inhibition of proliferation by type A pericytes largely abolished
fibrotic scar tissue generation and resulted in unsealed lesions and impaired wound healing,
highlighting the importance of pericyte-derived scarring in regaining tissue integrity and
wound closure. On the other hand, moderate inhibition of type A pericyte proliferation
preserved wound closure and resulted in attenuated fibrotic scar tissue generation. This
represented an attractive scenario to investigate the role of pericyte-derived scarring in axonal
regeneration and functional recovery after spinal cord injury.
In Paper II we demonstrated that attenuation of pericyte-derived scarring is accompanied by
decreased fibrosis, extracellular matrix deposition, astrogliosis and inflammation, and
promoted regeneration of raphespinal and corticospinal tract axons caudal to the lesion.
Corticospinal tract axons found below the injury site established functional synapses with
local spinal neurons. Recovery of sensorimotor function was improved in animals with
reduced pericyte-derived scarring. These results established pericyte-derived scarring as a
therapeutic target to improve recovery following central nervous system injury.
In Paper III we asked whether generation of periycte-derived scar tissue is preserved across
diverse central nervous system lesions. In addition to traumatic spinal cord injury, we found
that type A pericyte progeny detached from the vascular wall and generated fibrotic scar
tissue, or contributed to tumor stroma, after traumatic brain injury, inflammatory
demyelinating disease and in a glioblastoma tumor model, respectively. Following cerebral
ischemic stroke, type A pericytes increased |
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