The Effect ofAging on Skeletal MuseIe Capillarization in a Murine Model

Capillarization 0/skeletal muscle has been reported to be both maintained and reduced with advancing age. This conftict may represent methodological differences between biopsy studies. We have examined capillarization throughout two muscles, soleus and extensor digitorum longus (EDL),/rom a well-established colony 0/aging mice, and related this to fiber number (CIF ratio) and type. Labeling 0 / muscle capillaries was performed with the biotinylated Griffonia (Bandeiraea) simplicifolia lectin (GSL I) using immunochemistry. The results showed a signijicant increase in the CIF ratio in the aged mice when compared with the younger (6-month mice soleus =1.296,95 % CI 1.226-1.366 vs 28-month mice soleus =1.530,95 % CI 1.488-1.572, P <.001; 6-month mice EDL =0.881,95 % CI 0.751-1.011 vs 28-month mice EDL = 1.124,95 % CI 1.028-1.220, p =.017). These differences could not be accountedfor by changes infiber type but may reflect loss 0/fibers. Alternatively, there may be increased angiogenic drive or a failure 0/downregulation 0/angioge1Jl!sis. M USCLE mass and force generation decline with advanc-ing age. The principal cause is believed to be loss of motor units, but other factors may contribute (1). Microenviron-mental failure or, more specifically, failure to produce support-ive structures such as capillary vessels, may account for a lim-ited capacity for maintenance and regeneration of skeletal muscle in elderly adults (2-4). Evidence does exist in othe