The potential role of myofibroblasts in the obliteration of arteriovenous malformations after radiosurgery.
OBJECTIVE
To examine the structural changes in arteriovenous malformations (AVMs) after stereotactic radiosurgery and to identify the cytoskeletal antigen phenotype of the proliferating cells to gain information about the possible mechanism of obliteration.


METHODS
We conducted immunohistochemical and electromicroscopic investigations of surgical material that was removed from seven patients. The patients were harboring cerebral AVMs that had been previously treated with gamma knife irradiation, and they experienced subsequent bleeding 10 to 52 months after treatment.


RESULTS
Light microscopy revealed spindle-shaped cell proliferation in the connective tissue stroma and in the subendothelial region of the vessels. The ultrastructural and immunohistochemical characteristics of these spindle cells were identical to those designated as myofibroblasts in wound healing processes and pathological fibromatoses. Whereas in nonirradiated specimens of AVMs, similar cells expressed vimentin and desmin positivity, in irradiated cases, alpha-smooth muscle actin activity was also observed.


CONCLUSIONS
In view of the contractile activity of myofibroblasts, the proliferation generated by irradiation and the transformation of the resting cells into an activated form could be relevant to the shrinking process and eventual occlusion of AVMs after radiosurgery.
Szeifert
G T
GT
Department of Neurological Surgery, Royal Hallamshire Hospital, Sheffield, England.
Kemeny
A A
AA
Timperley
W R
WR
Forster
D M
DM
D000328:Adult; D001165:Arteriovenous Malformations / Q000473:pathology / Q000601:surgery*; D002455:Cell Division / Q000502:physiology*; D003238:Connective Tissue / Q000473:pathology; D003598:Cytoskeletal Proteins / Q000032:analysis; D003893:Desmin; D005347:Fibroblasts / Q000473:pathology*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000473:pathology*; D011183:Postoperative Complications / Q000473:pathology*; D016634:Radiosurgery; D012008:Recurrence; D012086:Reoperation
D003598:Cytoskeletal Proteins; D003893:Desmin