Problem with Fibroblasts cell culture from a skin biopsy

I used collagenase to digest the minced tissue it takes about 2 hr to completely dissolve them..than to a 70 um cell strainer..pellet the cells and culture with DMEM with 10% serum..they attach at the next day...it's not difficult really

http://www.currentprotocols.com/WileyCDA/CPUnit/refId-cb0201.html

I've used the explants method. We use to mince the skin punch biopsy and place around 5-10 pieces on the botton of a T25 flask. We add 1,5mL of CHANG medium, put the flask in an incubator (5% of CO2 in atmospheric air) then let the skin pieces adhere 3 days. After this time, the medium is completed to 4 mL. After one week of culture, the cells began to appear aroud the skin pieces. the medium is changed to 4/5 (HAM F'10 + 12%SVF, +antibiotics if necessary) + 1/5 CHANG medium until the cell culture become confluent.
Then the cells are trypsinized and reseeded in 1T75 flask in HAM F'10 + 12% SVF. We use to duplicate our cells every weeks.