Requirements reuse has been recently pointed out as one of the most pressing needs and grand challenges in Requirements Engineering. To cope with this demand, this work presents a systematic requirements reuse approach in the Model-Driven Software Development context. The proposal revolves around REMM, a Requirements Engineering MetaModel, which has been recently extended to provide variability modeling mechanisms, which enable requirements reuse. The REMM-Studio⁺ graphical modeling tool, built to support the new modeling capabilities of REMM, now enables the specification of both (1) catalogs of reusable requirements models (modeling for reuse), and (2) specific product requirements, by reusing previously defined requirements (modeling by reuse).