Granulation tissues, hypertrophic scars, hypertrophic scars treated with mechanical pressure and mature scars from deep thermal injuries, or equivalent trauma, were examined for the presence and dermal distribution of mast cells. Statistical analyses of mast cell counts indicate that 1) the hypertrophic scar contains significantly greater numbers of mast cells than the other tissues studied. 2) as granulation tissue develops interstitial collagen, mast cells begin to appear, 3) mature scars contain significantly fewer mast cells than hypertrophic scars, 4) based on mast cell data, the effect of pressure therapy is first detected in the upper and middle reticularis of the dermis, and 5) on a mast cell statistical basis mature scar and hypertrophic scar under pressure are indistinguishable.

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A b s t r a c t : Keloid t i s s u e h a s been implanted i n t h e athymic nude mouse i n o r d e r t o develop a n experimental animal model f o r t h e s t u d y o f human k e l o i d s and h y p e r t r o p h i c s c a r s . Untreated k e l o i d t i s s u e s maintained e s s e n t i a l l y t h e same morphological p a t t e r n s and glycosaminoglycan d i s t r i b u t i o n s f o r a t l e a s t 60 days a f t e r i m p l a n t a t i o n i n t h e athymic mice. Normal human s k i n implanted i n t h e same way was maintained w i t h o u t change i n glycosaminog l y c a n d i s t r i b u t i o n o r morphologic c h a r a c t e r i s t i c s . W e s u g g e s t t h a t t h i s model may be u s e f u l f o r b a s i c r e s e a r c h of k e l o i d s and h y p e r t r o p h i c s c a r s i n t h a t it w i l l a l l o w s t u d i e s o f morphologic, biochemical and t h e r a p e u t i c i n t e r r e l a t i o n s h i p s under c o n t r o l l e d c o n d i t i o n s . @ 1985 Society f o r Experimental Biology and Nedicine. _Introduction: Basic r e s e a r c h on k e l o i d s and h y p e r t r o p h i c s c a r s h a s been g r e a t l y hampered because of t h e absence o f s u i t a b l e animal models f o r t h e s e c o n d i t i o n s . Hypertrophic s c a r s have been d e s c r i b e d i n a number o f farm animals; however, none of t h e s e have proven t o be s i m i l a r t o human h y p e r t r o p h i c s c a r s o r k e l o i d s i n regard t o h i s t o l o g y , biochemistry, o r c l i n i c a l h i s t o r y ( 1 ) . Attempts have been made t o induce t h e s e l e s i o n s i n animals, p a r t i c u l a r l y i n swine ( 2 ) . However, t h e s e s c a r s have n o t been accepted a s s i m i l a r t o human hypert r o p h i c s c a r s o r k e l o i d s . Recently, i t occurred t o u s t h a t s i n c e normal and d i s e a s e d human s k i n may be i mp l a n t e d and maintained i n t h e athymic nude mouse ( 3 , 4 , 5 , 6 ) a n animal model might be developed f o r k e l o i d r e s e a r c h by implanting k e l o i d s i n athymic nude mice. Consequently, we implanted human k e l o i d t i s s u e i n athymic nude mice and have i n v e s t i g ag a t e d whether t h e maintained t i s s u e has t h e d i s t i n c t i v e h i s t o l o g i c a l a s p e c t s and t h e biochemical composit i o n o f t h e o r i g i n a l k e l o i d t i s s u e . Previous p u b l i c a t i o n s have d e s c r i b e d t h e c h a r a c t e r i s t i c microscopic appearance (7) and c h a r a c t e r i s t i c a l t e r a t i o n s o f t h e glycosaminoglycans ( 8 ) i n k e l o i d s and h y p e r t r o p h i c s c a r s . M a t e r i a l s and Methods: Athymic nude mice ( N~/ c o x ) were obtained from Labor a t o r y Supply Company, I n d i a n a p o l i s , Indiana. They were k e p t i n p r e s t e r il i z e d cages, one mouse t o a cage, and placed i n a laminar flow sterile bench (Labconco Corporation, Model 36000).