In contrast to denervation, there seem to be indica tions of capillary growth in some muscle dystrophies.Capillary supply was lower in inflammatory myopathies. The results in skeletal muscles are controversial and indicate that capillary growth, or re gression, can be induced by difBetamethasone ferent mechanisms in dif ferent types of muscle diseases.Newly formed endothelial cells could migrate distally from their origin and extend the sprout.Tapering sprouts with an incomplete basement membrane occurred earlier than saccular sprouts that had welldeveloped basement membranes.Capillary growth has been extensively studied in minced and whole muscle grafts, as well as in regenerat ing limbs in amphibians.In the latter, capillary prolifer ation occurred in poorly rather than in wellvascular ized regions and was prevented by exposure to high oxy gen slowed vascular growth by denervation performed before the onset of vascularization.By days the regenerate was vascularized, and by days vas cularization was completed with myoblasts occurring in all regions slightly ahead of capillaries.Frequent mitosis and sprouting occurred on the second day.Capillaries sometimes grew into channels created by the basal lamina of the degenerat ing muscle fibers.Fibrocytelike cells were apposed to the endothelium and later formed arterioles, and some smooth muscle cells may have persisted and been used in the formation of larger vessels.The CF reached of control values by the seventh day in the periphery but only in the muscle center, and it took almost days to reach normal values. Speed and completeness of growth has been related to the size of the transplanted muscles, as well as to the age of the animal.Grafts in moold rabbits regener ated faster than in moold animals, and muscles larger than galways had an ischemic center filled with connective tissue without vascular supply. Au totransplanted cat muscles, which usually weighed g, were therefore revascularized much more slowly, the process starting days after transplantation and being completed after wk. Capillary growth never started from preexisting vessels and was faster in rein nervated parts of the muscle. When grafted mus cles were connected to supplying vessels and nerves, complete functional recovery with normal CD occurred after mo, even though blood flow had by then returned to normal values. Unlike in amphibian muscles, growth of vessels or re generation of muscle fibers was not affected by denerva tion performed before transplantation.Capillary growth was considerably accelerated when grafted rat fast muscles were stimulated chronically at a low frequency, but training by running did not have a great effect on vascular growth in soleus grafts. Direct observation of vascularization in muscle bundles from extensor digitorum longus transplanted into hamster cheek pouch revealed that blood vessels adjacent to the vascularized host tissue survived and gave rise to sprouts growing toward the cheek pouch. Circulation between the Pentoxifylline transplant and the host tissue was established within days, and growth of new vessels was preceded by dedifferentiation in which ex isting blood vessels lost their smooth muscle before be ginning to sprout.An increase in vessel length was the result of a combination of stretching of endothelial cells, migration, and mitosis.