|
Year |
2002 |
|---|---|
|
Question Number |
253 |
|
Category |
Orthopaedic Science |
Question
The distinguishing morphologic characteristic of the myofibroblast, in contrast to the fibroblast and smooth muscle cell, is the presence of
1- prominent intracellular bundles of microfilaments
2- poorly developed secretory organelles
3- a well-developed enveloping basal lamina
4- a rounded, smooth nucleus
5- extracellular appendages
Figures
Answer (click for answer)
Preferred response: 1
Dupuytren’s disease is characterized by contraction of the palmar fascia which causes progressive and sometimes debilitating flexion deformity of the fingers. The disease is more common in male patients (ratio as high as 9:1 in some studies) and persons of northern European and Scandinavian ancestry. Risk factors for its development include smoking, EtOH, and diabetes. Genetics also appears to play a role and the condition is inherited in an autosomal dominant fashion (variable penetrance).
The pathologic cell responsible for causing fascial contraction is the myofibroblast. This cell shares characteristics of both the smooth muscle cell and the fibroblast and has been isolated from Dupuytren’s hands by electron microscopy. Its presence transforms the normal fascial bands and ligaments of the palm and digits into the pathologic "cords" responsible for the deformity. The distinguishing characteristic of the myofibroblast is the presence of intracellular bundles of actin and myosin, which give the cell its contractile ability. This definitely sets it apart from fibroblasts, which have no discernable bundles. However, smooth muscle cells have similar microfilament bundles making answer 1 at best questionable. All of the other choices are not characteristic of the myofibroblast, leaving answer 1 as the most appropriate choice of this poorly worded question. Myofibroblasts have well-developed secretory organelles (answer 2 incorrect) and lack a basal lamina (answer 3 incorrect). Their nuclei are elongated with shallow indentations (answer 4 incorrect) and no extracellular appendages are present (answer 5 incorrect), although a specialized attachment site called the fibronexus has been identified at the cell’s surface as the proposed transmitter of intracellular contraction to the extracellular tissues (ie: palmar fascia).
Reference: Tomasek JJ, Vaughn MB, Haaksma CJ: Cellular structure and biology of Dupuytren’s disease. Hand Clin 1999;15:21-34.
Light TR (ed): Hand Surgery Update 2. Rosemont, IL, American Society for Surgery of the Hand, 1999, pp. 263-272.