Heat inactivation of sera was originally implemented to inactivate complement which interfered in assays. The process has impacts on other molecules that may not have been quantified or evaluated. The literature varies as to the potential positive and negative effects of heat inactivation. For most cell lines in routine culture, it is likely not needed. The question becomes less clear in specific applications such as proteomic studies. The only way to ensure heat inactivation is not required is data from controlled experiments. It may be determined that heat inactivation is required for consistency with prior data, culture performance or not at all. If it is determined that heat inactivation is required, I would advise that heat inactivated serum be purchased. Manufacturers should have validated processes for heat inactivation that will ensure the product you receive is as consistent as possible.
In reference specifically to MSC culture, there are products qualified for MSC applications that are not heat inactivated on the market. There are some culture routines and literature which support using heat inactivated serum in MSC culture. The final decision on to use heat inactivated serum or not is specific to the application.