A study on human adipose tissue-derived mesenchymal stem cells (AT-MSCs) by Massoudi (2011) showed that AT-MSCs fusion with myobast was essential to acquire muscle identity [1]. However, a study showed that induction of processed lipoaspirate in differentiation medium resulted in the expression of myoD1, myf5, myf6, myogenin, and myosin heavy chain. The differentiation medium contained 50µM hydrocortisone, 10% FBS and 5% horse serum [2]. MyoD, myf, and myogenin are some of the various transcription factors that control the determination, proliferation and differentiation of myoblast, and therefore are collectively called as myogenic regulatory factors [2a]. Another study showed that 0.001% of adipose tissue stromal vascular fraction cells differentiated into skeletal muscle when cultured in differentiation medium. The differentiation medium contained high glucose DMEM, 5% horse serum, and 2mM L-glutamine [3]. Both studies showed that without co-culture the adipose tissue derived cells with myoblast, the cells could differentiate into myogenic cells when cultured in special medium [2, 3].

Di Rocco et al (2006) showed that adipose tissue contained various kinds of stem cells, i.e. fast plastic adherent cells that gave rise to mesenchymal stem cells, and at least ten cell types with morphological difference that were slow plastic adherent, which required fibronectin coating to adhere to the culture dish. One of the ten cell types was able to generate contractile myotube upon induction with differentiation medium, followed by terminal differentiation. It is supposed that this small subpopulation of stem cells with myogenic potentials is represented by both Sca1 and CD34 negative stem cells [3].

In the study by Massoudi (2001), the content of the differentiation medium was not elaborated in the materials and method section. However, some explanations about the culture media were available in the results section: “In vitro, no myotube formation occurred when hMADS cells were cultured in various media supplemented with hormones and cytokines related to myogenesis, as well as with chemical activators or inhibitors of signaling pathways.” I supposed the differentiation medium to be the similar to Zuk et al [2], and Di Rocco et al [3], as horse serum was one of the materials [1]. Further, the initial culture was done as follows: “Cells were inoculated at a density of 4500 cells/cm2 in proliferation medium (PM), Dulbecco’s modified Eagle’s medium (DMEM, low glucose) supplemented with 10% FCS, 2.5 ng/ml hFGF2, penicillin/streptomycin. PM was changed every 2-3 days” [1]. The method of initial culture did not use fibronectin, and change of medium will possibly wash out most of the stem cells with myogenic properties, as they are late adhering cells.  

In conclusion, the possible cause of the failure to differentiate the adipose derived stem cells without co-culture is in the initial culture, which did not use fibronectin. Therefore, the stem cells with myogenic properties were washed out when the medium was changed. This fact should be highlighted in the discussion.

References

Doing researches on adipose tissue derived stem cell and immunohistochemistry