Meeting the growing needs of the perinatal RegenMed Industry: the only Umbilical Cord hMSC (hUC-MSC) system designed for today’s translationally focused research and product development

Authored by Iain Farrance, PhD, Technical Marketing Associate

Introduction

Human mesenchymal stromal cells (hMSC) are considered the "workhorse" of Regenerative Medicine (RegenMed).  hMSC are a critical starting material in a growing variety of established and emerging RegenMed products, including cellular therapies, cell-based gene therapies, hMSC-derived extracellular vesicles (EVs), and bioprinted engineered tissues (Olsen, 2018). Accordingly, there have been greater than 100 clinical trials initiated each year since 2011 using hMSC from various sources (database purchased from celltrials.org) across a host of indications and therapeutic strategies (clinical trials.gov).  hMSC have benefitted from having an excellent safety profile, and there have been nine (9) products approved globally over the last 10 years. The growth in use of hMSC in a variety of product types has created the opportunity to standardize the supply chain and provide economies of scale for a rapidly growing industry. RoosterBio was founded to industrialize and standardize the RegenMed supply chain and to radically simplify the incorporation of living cells into therapeutic product development. Our goal is to have the same impact on the RegenMed industry that Intel had on the computer industry.

Use of Human Umbilical Cord-derived MSCs (hUC-MSC) in research and clinical trials (CT) has grown rapidly over the last 10 to 15 years with quickest adoption in APAC (Figure 1, Davies, 2017; Zhao, 2018; Moll, 2019). hUC-MSC publications per year increased 19-fold increase from 2006 to 2016 (Zhao, 2018). CT with hUC-MSC have shown a similar growth pattern as publications. hUC-MSC are the second most used hMSC type in CT (Moll, 2019) and 178 CT using hUC-MSC were registered, are ongoing, or were completed between 2007 and 2017 (Couto, 2019). In fact, >30% of hMSC trials registered in 2019 use hUC-MSC as the cell source.  These drive the need for hUC-MSC to use in product development. Until now, IP surrounding hUC-MSC has been a primary roadblock to the widespread adoption of hUC-MSC. We have collaborated with leaders in Wharton’s Jelly/umbilical cord hMSC at Tissue RegenerationTherapeutics Inc. (TRT) and have brought to market a complete bioprocess cell and media system. RoosterBio’s hUC-MSC are available for licensing and are provided in scalable formulations and cGMP compatible processes that enable anyone to obtain hUC-MSC in numbers needed for incorporation into RegenMed product development.

Until now RoosterBio has paired our batch (2D) and fed-batch (3D bioreactor) bioprocess media systems with hMSC from two sources: adipose-derived (hAD-MSC) and bone marrow-derived (hBM-MSC and xeno-free (XF) hBM-MSC). RoosterBio’s launch of our XF hUC-MSC (RoosterVial™-hUC-MSC-XF) introduces the first umbilical cord-derived hMSC in the North American and worldwide market designed to meet the quality and volume needs of today’s translationally focused cell therapy product developers. For RoosterBio’s hMSC product lines see here.

RoosterBio’s RoosterVial-hUC-MSC-XF and RoosterNourish™-MSC cell and medium bioprocess system has several key advantages over the limited number of suppliers of perinatal hMSC. Being XF, and manufactured with RoosterBio’s existing cGMP compatible processes, our system is the only hUC-MSC commercially available with a clear line of sight to clinical translation.  Additionally, other suppliers (a) provide low cell number vials at a high price per M cells, (b) supply serum-based cells, or (c) require specialized, non-scalable culture vessels.  Finally, RoosterBio provides first in class characterization of hMSC key quality attributes (PDL, identity, expansion potential) and functional assays (cytokine secretion, trilineage differentiation, immunomodulation).

Guest Blog Post: The Ambitious Future of Tissue Engineering

Bagrat Grigoryan and Jordan Miller, Physiologic Systems Engineering & Advanced Materials Lab at Rice University.

Over the last several decades, various advances in tissue engineering have allowed for the not so distant possibility of replacing, repairing, or regenerating injured tissues¹. Significant progress has been made in understanding cellular biology as well as pathophysiology and healthy states of tissues. Additionally, a suite of diverse biofabrication technologies and biomaterials has been conceived, enabling fabrication of complex 3D tissues with greater physiological relevance compared to the traditional 2D context that cells are studied in². However, the field of tissue engineering still has unresolved questions involving choice of fabrication technique, biomaterial, cellular niche, or even cell type when designing a synthetic tissue.

While different fabrication techniques and biomaterials have been explored in fabricating tissues in vitro, the use of stem cells in engineered tissues is ubiquitous. Not surprisingly so, as biologists continually demonstrate novel ways of directing different lineage commitment of stem cells and further unlocking their vast regenerative potential³. Indeed, stem cell banks have emerged to cryogenically store a patient’s own cells as the therapeutic potential of stem cells is being positively demonstrated in multiple clinical trials⁴. With over 450 mesenchymal stem cell (MSC)-based trials alone currently ongoing or completed, the regenerative and immunoregulatory properties of MSCs are constantly being exploited to improve the quality of human life⁵.

Due to the immense therapeutic potential of MSCs, there is a need to rapidly and reproducibly grow a vast amount of MSCs for clinical and research purposes. Although MSCs were identified and isolated from bone marrow more than 40 years ago, we still have not fully mapped their biological characteristics³.

Enabling a New Paradigm in hMSC Suspension Bioreactor Cultures

Introduction

RoosterBio is introducing a new product for highly efficient bioreactor expansion of human Mesenchymal Stem/Stromal Cells (hMSCs) that we are calling RoosterReplenish-MSC.  This innovative, first-in-class stem cell product is a concentrated bioreactor feed that replaces nutrients and growth factors that have been depleted during microcarrier expansion of hMSCs and replaces the need for a media exchange, enabling scalable and efficient fed-batch hMSC bioreactor expansion processes.  This is the first of several new products that we will launch enabling a cell therapy and tissue engineering bioprocess revolution that will be the foundation of a sustainable Regenerative Medicine Industry.

Media Designed for Scale-up

Human stem cells, characterized by their multi-lineage differentiation potential, tissue regenerative capacity, and high proliferation rates, are the most critical raw material in Regenerative Medicine today. Most cell-based therapies require between 50 million and >1 billion cells per patient application, necessitating efficient expansion (i.e. manufacturing) of starting cell sources.  Today, the most widely used cell expansion platforms for stem cell culture are planar technologies such as flasks and multi-layer cell factories (Rowley et. al), but it is generally accepted that lot sizes and COGS generated from these platforms are insufficient to meet the demand of a widely-used commercial product (Simaria et al).

Production technologies such as single use suspension bioreactors (used routinely in protein, monoclonal antibody and vaccine production) are proven to be robust, scalable manufacturing platforms. These platforms operate in a closed and controlled environment, which minimizes the risk of contamination, and are shown to reduce the time, expense, and carbon footprint required for cell processing. More importantly, it has been shown that such systems can yield lot sizes of hundreds of billions to (eventually) >1 trillion cells per manufacturing run, producing commercially-relevant lot sizes (Rowley et. al). 

MSC expansion in suspension bioreactors is typically done by growing cells on adherent substrates, such as microcarriers (Chen et al, Schnitzler et al, Szczypka et al).  Optimization of an efficient MSC bioreactor culture is central to maximizing yields and recovering healthy, functional cells at harvest. Another key attribute to efficient manufacturing processes is cost, and minimizing cost is crucial for building successful business models around MSC-based regenerative therapies.  Cell culture media is consistently the main cost driver of any stem cell production process, and it is critical to minimize media usage to keep production costs to a minimum (Rowley et al). Optimization of MSC-microcarrier cultures typically involves either full or partial media exchanges to manage nutrient supply and waste build-up (Goh et. al, Reichmann et al, Nienow et al, Santos et al, and Heathman et al), which is expensive and impractical at larger scales of >50L culture. This media exchange mentality is driven by the fact that commercially-available hMSC media formulations have been designed for flask-based culture processes and full media exchanges.  

Half media exchanges are the simplest to perform in small scale; however, when spent medium is only partially replaced with growth medium, the final concentration of nutrients and growth factors required for optimum cell proliferation are significantly reduced, resulting in lower cell proliferation rates. In addition, this procedure is time consuming, and the feasibility at larger scales decreases. Fed-batch culture, on the other hand, is more efficient in reducing processing time, mitigating contamination risk, and reducing costs associated with waste management such as time, labor, equipment and facility required to prepare and handle spent media. Hence, a new media design philosophy is required for suspension-based hMSC culture, and RoosterReplenish-MSC, coupled with RoosterBio’s High Perfromance Media kit, is the first media system designed specifically for hMSC bioreactor culture.

RoosterReplenish-MSC, a concentrated bioreactor feed, replaces nutrients and growth factors that have been depleted from RoosterBio’s High Performance Growth Media (KT-001) during extended culture. The nutrient boost provided by RoosterReplenish-MSC replaces the need for partial or full media exchanges when using our rich basal media, yielding a more streamlined culture process for hMSC expansion in bioreactors, and enabling efficiency in media utilization. 

In the next section, we will describe a series of studies performed with RoosterReplenish-MSC in microcarrier suspension culture.

Experimental Methods, Results & Discusssions

Rapid and Economic Generation of hMSC Spheroids for Macroscopic Tissue Biofabrication

Mesenchymal stem cells (MSCs) aggregated into three-dimensional (3D) cellular spheroids are a potent configuration for cell therapy and tissue engineering research and product development (5), and cellular spheroids are a preferred format for many bioprinting applications (10).  Cellular spheroids are essentially micro-tissues that can be manufactured as standardized “living materials” with certain controllable, measurable, and evolving material properties (10). Studies have shown that MSC aggregation into spheroids yield improved in vitro biological functionality over MSCs grown as 2D monolayer; likely due to the 3D tissue-like structure resembling the native configuration of cells in vivo with a microenvironment that allows for direct cell-cell signaling and cell-matrix interactions. MSC spheroids demonstrate enhanced cartilage, bone, and fat differentiation, as well as increased paracrine factor secretion over 2D MSC cultures (1-7). In vivo administration of hMSC spheroids has also showed enhanced therapeutic properties in pre-clinical models of myocardial infarction, bone and cartilage repair, and limb ischemia (3, 5, 8).  

Traditionally, aggregates were formed using suspension culture in spinners or shake flasks or in hanging drop cultures (5). The advancement of technologies has allowed one to quickly and easily generate large numbers of spheroids consistent in size and shape using forced aggregation in micro-wells (AggreWells, Stem Cell Technologies), or using liquid handling automation and 96 or 384 well hanging-droplet plates. There are also tools available that allow researchers to mold micro-tissues into interesting shapes such as rods, toroids, honeycombs, or whatever one can dream up (12-13).  While there are multiple methods for creating hMSC micro-tissues, the biggest challenge is reproducibly growing up sufficient hMSCs to create enough spheroids to start an experiment.  For example, if a researcher needs 10,000 spheroids with an average of 1000 cells per spheroid, then he/she will need at least 10 million cells to begin the experiment, which can take weeks to grow (see process flow diagrams below).  If he/she wishes to use 5000, or 10,000 cells per spheroid, then he/she will need 50 million or 100 million cells for his/her experiment.  This volume of cells has traditionally been very costly and time consuming to generate.

This Application Blog Post will provide a simple protocol to rapidly and economically generate tens of millions of high quality hMSCs so that researchers can minimize their time spent on routine cell culture and maximize their effort on performing hMSC spheroid-based experiments.