Exhibit 5.1

		DLA Piper LLP (US) 4365 Executive Drive, Suite 1100 San Diego, California 92121-2133 www.dlapiper.com   T 858.677.1400 F 858.677.1401

July 20, 2020

Histogen Inc.

10655 Sorrento Valley Road, Suite 200

San Diego, CA 92121

Ladies and Gentlemen:

You have requested our opinion with respect to certain matters in connection with the sale and issuance by Histogen Inc., a Delaware corporation (the “Company”), of 66,964 shares (the “Commitment Shares”) of the Company’s common stock, par value $0.0001 per share (the “Common Stock”), (ii) 328,516 shares of Common Stock (the “Initial Purchase Shares”), and (iii) up to Ten Million Dollars ($10,000,000) of Common Stock (the “Purchase Shares” and together with the Commitment Shares and the Initial Purchase Shares, the “Shares”), pursuant to an effective shelf registration statement on Form S-3 (File No. 333-220014) (the “Registration Statement”) filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”), and the related prospectus dated November 9, 2017 (the “Base Prospectus”), as supplemented by the prospectus supplement dated July 20, 2020 filed with the Commission pursuant to Rule 424(b) promulgated under the Act (together with the Base Prospectus, the “Prospectus”).

In connection with this opinion, we have examined and relied upon the Registration Statement and the related Prospectus, the Company’s Amended and Restated Certificate of Incorporation and Amended and Restated Bylaws, as currently in effect, and the originals or copies certified to our satisfaction of such other documents, records, certificates, memoranda and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below.

In rendering this opinion, we have assumed the genuineness and authenticity of all signatures on original documents; the genuineness and authenticity of all documents submitted to us as originals; the conformity to originals of all documents submitted to us as copies; the accuracy, completeness and authenticity of certificates of public officials; and the due authorization, execution and delivery of all documents where due authorization, execution and delivery are prerequisites to the effectiveness of such documents (other than with respect to the Company).

On the basis of the foregoing, and in reliance thereon, we are of the opinion that (i) the Commitment Shares and the Initial Purchase Shares have been duly and validly authorized and are validly issued, fully paid and nonassessable; and (ii) the Purchase Shares have been duly and validly authorized and, when issued and sold pursuant to that certain Purchase Agreement, dated July 20, 2020, by and between Histogen Inc. and Lincoln Park Capital Fund, LLC, in accordance with the Registration Statement and the Prospectus, will be validly issued, fully paid and nonassessable.

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We consent to the reference to our firm under the caption “Legal Matters” in the Prospectus and to the filing of this opinion as an exhibit to a Current Report of the Company on Form 8-K. In giving our consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission thereunder.

LN

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