1. A method for improving the cosmetic condition of a mammalian skin, wherein the mammal is administered: (i) a polypeptide containing the amino acid sequence shown in any of the sequences of SEQ ID No.1-4, or a sequence that is at least 90% identical to the sequence, or part of any of these sequences； or (ii) a cosmetic composition comprising (i) and one or more pharmaceutically acceptable excipients and / or diluents. 2. The method according to claim 1, wherein the polypeptide or composition is obtained, or the polypeptide or composition can be obtained by a method comprising at least the following steps: a) suspending fish eggs, preferably salmon caviar, in a minimum volume of water； b) initiating a synchronized, quick hatch caviar, preferably so that more than 95% of the embryos are hatching completed in less than 2 hours； c) filtering the caviar mass after hatching to obtain a medium obtained after hatching； and d) filtering the medium obtained after hatching to obtain a polypeptide and / or composition, the step of filtering the medium obtained after hatching includes at least the following steps: (i) filtering the medium obtained after hatching with a filter, pore size which is at least 5 μm, and collecting the filtrate； (ii) filtering the filtrate obtained in step (i) with a filter whose pore size is from 0.30 to 0.60 μm and collecting the filtrate； (iii) replacing the water in the filtrate obtained in step (ii), pharmaceutical acceptable buffer； (iv) filtering the solution obtained in step (iii) with a filter, and�1. Способ улучшения косметического состояния кожи млекопитающего согласно которому млекопитающему вводят:(i) полипептид, содержащий последовательность аминокислот, приведенную в любой из последовательностей SEQ ID No.1-4, или последовательность, которая по меньшей мере на 90% идентична упомянутой последовательности, или часть любой из упомянутых последовательностей； или(ii) косметическую композицию, содержащую (i) и один или несколько фармацевтиче
